Table of contents

Performing accurate, linear and stable Electrochemical Impedance Spectroscopy of Li/SOCl₂ based batteries (and more generally, all primary batteries) is challenging due to the lack of a (well-defined) charging reaction. The difficulty stems from irreversible operation chemistry (compromising stable operation) and the inconsistent anode passivation of the cell. The very scarce literature examples lack proper measurement protocol and accurate EIS data for Li/SOCl₂ that can be modeled. In this study, we demonstrate how these challenges can be overcome by performing Galvanostatic-EIS in discharge mode and investigate the details of how experimental parameters influence not only the measurement, but also the cell itself. We present linear and stable data that is compatible with the Kramers-Kronig relations in frequency ranges as wide as 10 kHz to 1 mHz for fully charged to fully discharged cells. Moreover, we utilize Harmonic Analysis to study the nonlinearities in the measurement and further show that the passivation of the anode is a major cause for the nonlinearities.

A systematic study on the key factors affecting the performance of electrochemical capacitor electrodes in solid electrolytes and their liquid electrolyte baselines was conducted. The study combined a test matrix of two types of activate carbons (AC) with different specific surface area, pore size and structures at various loadings in three solid and liquid electrolyte pairs. Working curves on loading vs. capacitance of these ACs in solid and corresponding liquid electrolytes revealed the correlation and interconnection of these material properties. A cross-sectional microscopic elemental analysis was used to identify and visualize the influence of these factors. When transition from liquid to solid polymer electrolytes, the infiltration of the electrolyte into the porous carbon plays a critical role in the performance of AC electrode especially at a high loading. When the precursor solution of polymer electrolyte was relatively less viscous, AC with an open structure and mesopores had similar capacitance as their liquid counterparts. A highly viscous precursor solution blocked some access of the polymer electrolytes into the bulk electrode, making infiltration less effective at high loading. This work shows an approach to project the performance of carbon electrodes in solid electrolytes and can provide directions for developing solid-state electrochemical capacitors.

In this paper we implement and test a new approach for the description of the electrochemical data (cyclic voltammetry and chronoamperometry) for phase transforming intercalation electrode materials. This approach assumes the rate-limiting step being associated with the slow nucleation of a new phase in the material particles. As a test model system, we used LiFePO₄ material. It is shown that all the electrochemical data for LiFePO₄ can be self-consistently described assuming a slow nucleation step with only minor influence of ionic diffusion and interfacial charge transfer kinetics on the intercalation rates. The developed formalism allows for a reliable diagnostics of the reaction rate control regime as well as for the extraction of information on the pre-exponential factor and activation energy values. The electrochemical diagnostic criteria for the slow nucleation step are formulated based on the shapes of the cyclic voltammetry peaks, current transients registered under potentiostatic conditions and specific features in the impedance spectra of phase-transforming electrodes.

Nickel sulfide has been studied extensively as a next-generation anode material for lithium ion batteries due to its great theoretical capacity (590 mAh g⁻¹), relatively high electrical conductivity and thermal stability compared to metal oxides. However, if it is used alone as an anode, performance is drastically reduced due to its pulverization during the cycling. To solve such problem, in this work, hierarchical carbon coated nickel sulfide is synthesized using both chemical vapor deposition of toluene and CaCO₃ nano-template, and the resultant material is employed as an anode material of lithium ion battery. It shows a capacity of 575 mAh g⁻¹ at a current density of 100 mA g⁻¹, and maintains over 270 mAh g⁻¹ at a high current density of 2000 mA g⁻¹. In the long-term cycle test, the capacity gradually increases to 606 mAh g⁻¹ around the 100^th cycle and shows the high retaining ratio relative to the initial capacity over 84% after 200 cycles. During the cycles, the nickel sulfide pulverizes into nanoparticles, but these particles remain inside the hierarchical carbon structure. Finally, they separate into nickel and lithium sulfide. This mechanism is confirmed using the cycle-by-cycle transmission electron microscopy images and additional ex situ analyses.

Crossover in Vanadium Redox Flow Batteries (VRFB) has an important impact on performance and is dependent on several physical properties, including the transference number. In this work, model-guided design of experiment was used to determine vanadium transference number in fully-hydrated ion-selective membranes, while minimizing uncertainties related to unknown or unmeasured properties. The transference number of VO²⁺ in Nafion 117 for varying ratios of H₂SO₄ to VOSO₄ was measured, and the analysis showed that the transference number estimate can be obtained with 5% or less uncertainty. The VO²⁺ transference number sharply decreased as acid was added to the electrolyte. The variation in the transference number with the ratio of H₂SO₄ to VOSO₄ was fit to a model to obtain the product of the ratio of vanadium-to-proton partition and diffusion coefficients.

Preparing carbon materials for supercapacitors with high specific capacitance via a facile approach has been a crucial issue recently. Nitrogen/phosphorus co-doped carbon materials (NPCs) have been prepared via direct carbonization of the mixture of urea formaldehyde microspheres (UFMs) and phosphoric acid (H₃PO₄). Change of chemical structure of UFMs during carbonization in the presence of H₃PO₄ was investigated by use of Thermogravimetric Analysis and Fourier transform infrared. The results showed that by controlling the content of H₃PO₄, specific surface area, elemental composition and microstructure of as-prepared product could be tuned, along with tunable electrochemical properties. When used as electrode materials for supercapacitors, the NPCs with optimized phosphorus content exhibited a markedly enhanced specific capacitance of 245 F·g⁻¹ at 0.5 A·g⁻¹ in 1 M H₂SO₄ with the moderate specific surface area (∼ 200 m²·g⁻¹). Moreover, the NPCs presented high rate capability of 191 F·g⁻¹ at 30 A·g⁻¹ (78% capacitance retention when compared with that at 0.5 A·g⁻¹) and excellent long-term stability with almost no capacitance loss over 7200 galvanostatic charge/discharge cycles.

Lithium-rich layered oxide Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ is synthesized by solid phase method and followed by surface modification with 2 wt% nAl₂O₃/SiO₂ (n means the molar ratio of Al₂O₃ and SiO₂). The morphology, structure and electrochemical properties of the material samples before and after coating treatment are systematically investigated by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, linear sweeping voltammetry, potentiostatic intermittent titration and electrochemical impedance spectroscopy. The results show that a protective multilayer is formed on the material particle surface with a new coating layer like Li_x[Al_ySi_zO₄] and an intermediate layer with lithium-deficient disordered spinel structure after annealing treatment. This multilayer can prevent the material from corrosion of the electrolyte deposition product, provide improved lithium ion transportation and suppress the evolution from layered structure to spinel. The coated samples present the improved initial coulombic efficiency, capacity retention, cycling stability, rate capability and reduced voltage decay compared to the pristine material and it delivers the best comprehensive electrochemical performance when the molar ratio of Al₂O₃ and SiO₂ is 2:1. The main role of Al₂O₃ and SiO₂ in coating for the improvements of the material performance is further discussed.

In order to meet the critical energy-storage challenges of the future, a next-generation lithium-ion battery will need to achieve a higher energy density and longer cycle life. While increasing the nickel content in layered LiMO₂ (M = Ni, Mn, Co) significantly improves the capacity of the material, nickel-rich cathodes cycled in conventional organic electrolytes commonly suffer from crystallographic phase transformation and the growth of a resistive interfacial layer, both of which result in voltage fade and capacity degradation during cycling. However, pairing a nickel-rich cathode with an appropriate ionic liquid (IL) electrolyte enables exceptional cycling stability and energy retention. This work demonstrates how a pyrrolidinium-based IL electrolyte not only allows for cycling to higher voltages but shows a 95% energy retention and average discharge capacity of 189 mAh g⁻¹ over 150 cycles between 3 and 4.5 V vs. Li/Li⁺ with a nickel-rich layered cathode. Based on electrochemical and crystallographic analyses, the exceptional performance of the cells cycled in IL is attributed to the stability of the electrode-electrolyte interfacial layer formed by the IL which protects the active material and suppresses the structural degradation commonly observed in nickel-rich cathodes.

Lithium-sulfur battery (LSBs) is one of the most promising energy storage technologies due to its high energy density. The insulating properties of the sulfur and shuttle effect of the polysulfides during charge/discharge process limit its commercial application. In this work, we prepared a hierarchical N/P co-doped porous carbon (DPC) via NH₄H₂PO₄ and KHCO₃ dual-activation of the porous carbon, which was obtained by annealing of nano-calcium carbonate/sucrose composites. The resulting DPC/S composite as cathode materials for LSBs shows a promising long-term cycling stability (968.9 mAh g⁻¹ after 100 cycles at 0.2 C) and rate performance (624.4 mAh g⁻¹ at 1 C, 545.4 mAh g⁻¹ at 2 C). The structural superiority of DPC host materials, i.e., highly porous structure, hierarchical pores and N/P co-doping contributes to the superior electrochemical performance of the materials. The simple synthesis process and low cost of the highly porous carbon makes it a promising candidate for encapsulation of active sulfur in lithium sulfur battery.

In this work, an artificial intelligence based optimization analysis is done using the porous electrode pseudo two-dimensional (P2D) lithium-ion battery model. Due to the nonlinearity and large parameter space of the physics-based model, parameter calibration is often an expensive and difficult task. Several classes of optimizers are tested under ideal conditions. Using artificial neural networks, a hybrid optimization scheme inspired by the neural network-based chess engine DeepChess is proposed that can significantly improve the converged optimization result, outperforming a genetic algorithm and polishing optimizer pair by 10-fold and outperforming a random initial guess by 30-fold. This initial guess creation technique demonstrates significant improvements on accurate identification of model parameters compared to conventional methods. Accurate parameter identification is of paramount importance when using sophisticated models in control applications.

This paper studied the gases release of a graphite//NMC111(LiNi_1/3Mn_1/3Co_1/3O₂) cell during cycle in the voltage ranges of 2.6-4.2V and 2.6-4.8V and the temperatures of at 25°C and 60°C. It was proved that the CO₂, CO, and H₂ gases are released as a result of electrolyte decomposition. And it shows that the CO and H₂ gases evolution is a direct consequence of the electrochemical reaction of electrolyte decomposition, while the CO₂ generation is a consequence of the additional chemical reaction of interaction between the O₂ released from the cathode atomic lattice oxygen and CO released from the same place on the cathode (appearing because of the electrolyte decomposition). That is why at the same electrochemical reaction of electrolyte decomposition, the ratio CO₂/CO varies in the wide range from 0.82 to 2.42 depending on cycling conditions (temperature and cutoff voltage). It was proved that a potential-independent H₂ evolution is a consequence of its adsorption in pores of powdered graphite on anode. There was proposed the mechanism of the electrolyte decomposition and the gases evolution in lithium-ion cells at their cycling, which corresponds quantitatively to all obtained experimental results.

Due to its low cost, high abundance and non-toxicity zinc metal is a very promising electrode material for rechargeable batteries. The main drawback of using zinc in aqueous alkaline solutions is the formation of zinc dendrites, which lead to cell failure, and a low coulombic efficiency. In this study the suppression of dendritic zinc growth by applying either pure 1-ethylimidazolium trifluoromethane sulfonate or 1-ethylimidazolium trifluoromethane sulfonate / water mixtures with zinc trifluoromethane sulfonate as electrolyte formulations was examined. The surface morphology of the deposited zinc is significantly influenced by the amount of water present in the electrolyte. Cyclic voltammetry measurements showed a less negative reduction potential of zinc with increasing water content. Additionally, the presence of air in the electrolyte proved to be another factor influencing the cyclic voltammetry results. Furthermore, galvanostatic cycling data showed a lowering of the overpotential and constant potentials during long-term cycling of 100 cycles if water is present in the electrolyte, and SEM micrographs confirmed that the surface structure remains compact even after long-term cycling.

High capacity all-solid-state Li-ion battery anodes were prepared using an industrially scalable solution coating process. Employing commercially available polyacrylonitrile as a mixed conducting binder, we have demonstrated stable cycling, high capacity electrodes with large mass loadings of tin active material. This is, to our knowledge, the first time a high capacity lithium-alloying material has been utilized in a slurry-coated sheet-style all-solid-state Li-ion battery anode. Optimization of this new electrode architecture resulted in a sheet-style anode capable of retaining an electrode specific capacity of 643.5 mAh/g after 100 charge-discharge cycles at a 0.1C rate. We believe that this work represents a step forward for slurry-coated electrodes intended for use with sulfide solid electrolytes and that the continued development of these high capacity sheet-style anodes will be critical to the commercialization of the all-solid-state Li-ion battery.

Advancements in micro-scale additive manufacturing techniques have made it possible to fabricate intricate architectures including 3D interpenetrating electrode microstructures. A mesoscale electrochemical lithium-ion battery model is presented and implemented in the PETSc software framework using a finite volume scheme. The model is used to investigate interpenetrating 3D electrode architectures that offer potential energy density and power density improvements over traditional particle bed battery geometries. Using the computational model, a variety of battery electrode geometries are simulated and compared across various battery discharge rates and length scales to quantify performance trends and investigate geometrical factors that improve battery performance. The energy density vs. power density relationship of the electrode microstructures are compared in several ways, including a uniform surface area to volume ratio comparison as well as a comparison requiring a minimum manufacturable feature size. Significant performance improvements over traditional particle-bed electrode designs are predicted, and electrode microarchitectures derived from minimal surfaces are shown to be superior under a minimum feature size constraint, especially when subjected to high discharge currents. An average Thiele modulus formulation is presented as a back-of-the-envelope calculation to predict the performance trends of microbattery electrode geometries.

For the first time, polypyrrole (PPy) coated carbon nanotubes (CNT) were combined with FeOOH to fabricate negative supercapacitor (SCP) electrodes. The synergistic effects of PPy-CNT and FeOOH resulted in enhanced electrochemical performance at high active mass loading of 37 mg cm⁻² in a voltage window of −0.8–+0.1 V versus a saturated calomel electrode. Particle extraction through liquid-liquid interface (PELLI) was utilized for the agglomerate-free processing of FeOOH, which improved FeOOH mixing with PPy-CNT and contributed to the enhanced capacitive behavior of the composite. Tetradecylamine (TA) was found to be an efficient extractor for FeOOH. Cyclic voltammetry and impedance spectroscopy data at different electrode potentials provided an insight into the synergistic effects of PPy-CNT and FeOOH, and influence of PELLI on electrode performance. An areal capacitance of 4.5 F cm⁻² and nearly ideal capacitive behavior were achieved at a low electrode impedance. The important finding was that capacitances of the negative PPy-CNT-FeOOH and positive MnO₂-CNT electrodes can be matched in different voltage windows to fabricate advanced asymmetric devices, which exhibited promising electrochemical performance in a voltage window of 1.6 V at high active mass.

Lithium silicate was incorporated within Ni_0.5Co_0.2Mn_0.3(OH)₂ precursor particles via an anti-solvent precipitation method to prepare lithium silicate-added LiNi_0.5Co_0.2Mn_0.3O₂ (NCM) particles. Lithium silicate was found at the grain boundaries in the NCM secondary particles, which significantly improved the capacity retention in high voltage operation (3.0–4.6 V). Cross-sectional SEM images revealed that cracks were seriously formed inside the lithium silicate-free NCM particles after cycling, while crack formation was remarkably inhibited for lithium silicate-added NCM. These results suggested that lithium silicate at the grain boundaries strengthened the interfacial-adhesion between primary particles, resulting in the improved cycling stability.

Electrolytes based on non-flammable and electrochemically and thermally stable ionic liquids (ILs) are rendered promising alternatives to the conventionally applied organic electrolytes for lithium as well as sodium ion batteries (SIBs). In this study the electrochemical performance and thermal stability of a SIB full-cell containing an IL based electrolyte is evaluated and compared to a reference system employing a conventional organic electrolyte. Compatibility of the IL electrolyte with the electrode materials Na_0.6Co_0.1Mn_0.9O₂ (NMO) and Na_2.55V₆O₁₆ (NVO) is assured by SIB half-cell studies. In NMO/NVO full-cells the IL electrolyte outperforms the organic electrolyte in terms of cycling stability and columbic efficiency, reaching a retention of 76% after 100 cycles. Studies at 75°C show that, in contrast to the system based on the organic electrolyte, the IL-based SIB is capable of operating at elevated temperatures. Further, for the first time the superior safety of an IL-based SIB full-cell over the organic analogue is proven using Accelerating Rate Calorimetry (ARC) underlining the benefits of the IL based electrolyte.

Carbon nanosheets were synthesized by facile molten salt route using glucose as carbon source, and employed as positive electrocatalyst for vanadium redox flow battery (VRFB). Two kinds of carbon nanosheets were obtained at glucose/salt mass ratio of 1:10 (CNS-10) and 1:100 (CNS-100), respectively. Compared with CNS-10, CNS-100 with graphene-like structure has crumpled shape and large surface area. Electrochemical measurements verify that as-prepared carbon nanosheets exhibit good electrocatalytic properties to VO²⁺/VO₂⁺ redox reaction, and CNS-100 demonstrates the best performance. Excellent electrocatalytic performance of CNS-100 mainly comes from large specific area, crumpled shape and enhanced carbonization degree. These features favor the increase of reaction place, active site, and electrical conductivity, respectively, further accelerating the electrochemical kinetic process of VO²⁺/VO₂⁺ redox reaction. The cell using CNS-100 as positive catalyst displays superior electrochemical performance. Higher discharge capacity and capacity retention can be achieved in the cell using CNS-100. Moreover, utilization of CNS-100 can lead to energy efficiency increase of 5.3% compared with pristine cell at 50 mA cm⁻². Low-cost, high-performance, and graphene-like nanosheet obtained by molten salt route offers a broad application prospect for VRFB.

Composite materials containing metal oxide and carbon with optimized structures have shown potential advantages in improving the supercapacitor performance. Herein, the cohesive porous Co₃O₄/C composites are synthesized via a two-step calcination of zeolitic imidazole framework-67 (ZIF-67) single-source precursor. The results indicate that Co₃O₄ nanopaticles are in situ incorporated with partial graphitized carbon. As supercapacitor electrode material, the Co₃O₄/C composite exhibit higher specific capacitance (875.6 F g⁻¹ at 1 A g⁻¹) and better cycling stability (capacitance retention of 87.8% after 1000 cycles at 6 A g⁻¹) compared to pure Co₃O₄ (245.3 F g⁻¹ and 78.4% at the same condition). In addition, it shows good cycling stability with capacitance retention of 82% after 1000 cycles at 6 A g⁻¹ in the symmetric supercapacitor device. The better electrochemical performance can be attributed to the improvement of the conductivity, larger surface area for more active sites, and the ameliorative volume expansion of Co₃O₄ by the stable structure of Co₃O₄ nanopaticles well embedded in partial graphitized carbon matrix during long cycling process.

In this paper, nano Ag₄Bi₂O₅/rGO composite catalyst was obtained by in-situ growth and co-precipitation. The nano Ag₄Bi₂O₅ with a length of 200–300 nm and a width of 10–20 nm is supported by the surface of reduced graphene oxide. The obtained catalyst was represented by SEM, XRD, XPS, EDS and TG-DTG methods, and its electrocatalytic properties were evaluated by RDE, linear sweep voltammetry, EIS and cyclic voltammetry tests. The CV results display that there is a significant oxygen reduction peak current (2.27 mA cm⁻²) at the potential of 0.82V in the oxygen saturated 0.1 mol L⁻¹ KOH electrolyte. The LSV result shows, the catalyst has slightly higher current density (4.96 mA cm⁻²) and half-wave potential (0.75 V) than commercial Pt/C through a 4 electrons oxygen reduction mechanism. The results of i-t chronoamperometric method show the catalyst has superior methanol tolerance ability to the commercialized Pt/C (20%). Furthermore, the assembled Zn-O₂ batteries with Ag₄Bi₂O₅/rGO oxygen electrode provide better durability performance than commercialized Pt/C (20%) in the same alkaline electrolyte.

Sulfide-based solid electrolytes (SE) are quite attractive for application in all-solid-state batteries (ASSB) due to their high ionic conductivities and low grain boundary resistance. However, limited chemical and electrochemical stability demands for protection on both cathode and anode side. One promising concept to prevent unwanted reactions and simultaneously improve interfacial contacting at the anode side consists in applying a thin polymer film as interlayer between Li metal and the SE. In the present study, we investigated the combination of polyethylene oxide (PEO) based polymer films with the sulfide-based SE Li₁₀SnP₂S₁₂ (LSPS). We analyzed their compatibility using both electrochemical and chemical techniques. A steady increase in the cell resistance during calendar aging indicated decomposition reactions at the interfaces. By means of X-ray photoelectron spectroscopy and further analytical methods, the formation of polysulfides, P–[S]_n–P like bridged PS₄³⁻ units and sulfite, SO₃²⁻, was demonstrated. We critically discuss potential reasons and propose a plausible mechanism for the degradation of LSPS with PEO. The main objective of this paper is to highlight the importance of understanding interfaces in ASSBs not only from an electrochemical perspective, but also from a chemical point of view.

Roughening of metal electrodes in batteries is detrimental as it can lead to metal dendrites. Such dendrites can cause short circuits when they grow from the metal electrode to the other one, as can happen during battery operation when metal is plated onto the surface of an electrode. It has been suggested that solid electrolytes of sufficient elastic stiffness can suppress electrode surface roughening and dendriting, although experimental evidence is now emerging that this possibility is not valid. To investigate whether metal electrode surfaces will roughen during battery charging we carry out a linear perturbation analysis. Our calculations explore whether an electrode surface with one-dimensional sinusoidal roughness will experience growth of its amplitude. We assess a linear elastic electrolyte that is a single ion conductor bonded to a metal electrode being plated by a cathodic ionic current. We find that long wavelength perturbations will always increase in roughness. High current densities during battery charging are found to permit growth of the amplitude of small wavelength roughness. The stiffness of the solid electrolyte is found to play a role in limiting the growth of roughness, but its effect can always be overcome at high current densities and for long wavelength protrusions.

Increasing the charge rate of Li-ion cells over 1–2C (full charge in 30–60 min) would be highly desirable, but high currents flowing through the active materials push these cells to their endurance limits. In this article, we aim to understand how such high-current regimes affect electrochemical properties of the cells. Formation of Li metal deposits is a recognized hazard of high-rate charging, as Li plating can overtake lithium intercalation in the negative electrode. Here we demonstrate how microprobe Li/Cu reference electrodes can be used to characterize the graphite anode and layered oxide (NCM523) cathode during constant-current (≤ 6C) voltage-limited (4.39 V) charging of Li-ion cells. These reference electrodes are used to monitor the onset of Li plating conditions in situ during cell charging. As the current increases over 3C, the anode potentials decrease below −40 mV causing lithium nucleation. Surprisingly, this nucleation (at least, initially) does not result in capacity fade or a higher anode impedance even in strongly polarized cells, so it appears that the nascent Li nuclei are isolated from electrolyte by the pre-existing solid electrolyte interphase. Our study shows that microprobe reference electrodes are an important diagnostic tool to characterize full-cell behavior in the high-current regimes.

It is a common opinion that activated carbon (AC) should be functional groups-free when employed as capacitor-type material in organic electrolytes. This work analyzes in detail the relationship between the electrochemical performance of modified activated carbon electrodes and the introduced functional groups in two organic electrolytes containing lithium salts:1M LiPF₆ in EC-DMC (the commercial LP30) and 1M LiTFSI in EC-DMC. The surface functional groups (especially C=O or O–C=O) can induce higher capacitance to AC (more than 50% increase compared to commercial unmodified AC), whereas the rate capability dramatically decreases. The appropriate amount of functional groups is helpful to expand the electrochemical stability window in LP30 (2.8–2.9 V), that is responsible for the high energy and power density. Moreover, the proper functional groups inhibit the potential shift of the AC electrode. However, a large number of functionalities can result in a high amount of irreversible redox products remaining in the pores of AC, which leads to a faster capacitance fade respect to materials with less functional groups.

Li₂MoO₃ is a promising structural stabilizing unit for use in composite layered-layered cathodes for Li-ion batteries. To enable the rational design of such cathodes, studies on fundamental phenomena related to the active material structure and electrode/electrolyte interface are needed. The present work details the fabrication and characterization of thin film Li₂MoO₃ cathodes and shows that their electrochemical performance greatly depends on the nature of the cathode/electrolyte interface. The Li₂MoO₃ thin films exhibit poor cyclability in a liquid carbonate electrolyte (e.g., initial capacity of 166 mAh/g with 40% capacity fade over 20 cycles) whereas all-solid-state Li₂MoO₃/Lipon/Li batteries show negligible fade during cycling. A suite of characterization methods including Raman spectroscopy and X-ray photoelectron spectroscopy are used to study the evolution of the cathode structure and cathode electrolyte interphase (CEI) layer during charge/discharge cycling. Li transport rates are another important factor which affect cathode performance. AC impedance spectroscopy studies reveal that the Li diffusion coefficient (D_Li) in Li₂MoO₃ decreases from 4.36 × 10⁻¹¹ cm²/s in the fully discharged state to 4.51 × 10⁻¹³ cm²/s when charged to 3.6 V vs. Li/Li⁺. Overall, the results presented herein provide insight on the fundamental phenomena which govern Li₂MoO₃ cathode performance.

Surface chemistry modification of positive electrodes has been used widely to decrease capacity loss during Li-ion battery cycling. Recent work shows that coupled LiPF₆ decomposition and carbonate dehydrogenation is enhanced by increased metal-oxygen covalency associated with increasing Ni and/or lithium de-intercalation in metal oxide electrode, which can be responsible for capacity fading of Ni-rich oxide electrodes. Here we examined the reactivity of lithium nickel, manganese, cobalt oxide (LiNi_0.6Mn_0.2Co_0.2O₂, NMC622) modified by coating of Al₂O₃, Nb₂O₅ and TiO₂ with a 1 M LiPF₆ carbonate-based electrolyte. Cycling measurements revealed that Al₂O₃-coated NMC622 showed the least capacity loss during cycling to 4.6 V_Li compared to Nb₂O₅-, TiO₂- coated and uncoated NMC622, which was in agreement with smallest electrode impedance growth during cycling from electrochemical impedance spectroscopy (EIS). Ex-situ infrared spectroscopy of charged Nb₂O₅- and TiO₂-coated NMC622 pellets (without carbon nor binder) revealed blue peak shifts of 10 cm⁻¹, indicative of dehydrogenation of ethylene carbonate (EC), but not for Al₂O₃-coated NMC622. X-ray Photoelectron Spectroscopy (XPS) of charged TiO₂-coated NMC622 electrodes (carbon-free and binder-free) showed greater salt decomposition with the formation of lithium-nickel-titanium oxyfluoride species, which was in agreement with ex-situ infrared spectroscopy showing greater blue shifts of P-F peaks with increased charged voltages, indicative of species with less F-coordination than salt PF₆⁻ anion on the electrode surface. Greater salt decomposition was coupled with the increasing dehydrogenation of EC with higher coating content on the surface. This work shows that Al₂O₃ coating on NMC622 is the most effective in reducing carbonate dehydrogenation and accompanied salt decomposition and rendering minimum capacity loss relative to TiO₂ and Nb₂O₅ coating.

CoS is one of the ideal electrode materials for supercapacitor, but its long-term stability and electrochemical performance needed to be improved before its successful application. Uniformly embedding carbon nanotubes (CNTs) inside the CoS matrix can provide numerous and effective diffusion paths of electrons and electrolyte ions, which can reduce the charge-transfer resistance and effectively improve the electrochemical performance of CoS. In this work, nanocomposites of Co₂(CO₃)(OH)₂ and CNTs were prepared using a facile hydrothermal method, and then were transformed into CoS_1.29@CNTs nanocomposites via an ion-exchange process. The carbon nanotubes were uniformly embedded inside the CoS_1.29 matrix. When the amount of CNTs was 6.1 wt%, the CoS_1.29@CNTs electrode exhibited a higher specific capacitance (99.7 mAh g⁻¹) than that of CoS_1.29 electrode (84.1 mAh g⁻¹) at a current density of 1 A g⁻¹ measured in 2 M KOH electrolyte. The asymmetric supercapacitor assembled with the CoS_1.29@CNTs-6.1% electrode and an activated carbon (AC) electrode exhibited an energy density of 39.1 Wh kg⁻¹ at a power density of 399.9 W kg⁻¹. Moreover, the specific capacitance of the CoS_1.29@CNTs-6.1%//AC device maintained 91.3% of its original value after 2000 cycles at a current density of 3 A g⁻¹.

LiNi_0.8Co_0.15Al_0.05O₂ cathode material coated with graphene nanodots (GNDs) is designed for the first time to enhance the electrochemical performance. The uniform distribution of GNDs with the size of 5 nm on the LiNi_0.8Co_0.15Al_0.05O₂ particle surface can dramatically improve the electronic conductivity. Furthermore, the moderate GNDs coating can provide abundant lithium-ion transportation pathways for the enhanced rate performance. As a result, the GNDs-coated LiNi_0.8Co_0.15Al_0.05O₂ with 0.5 wt% coating amount exhibits a high discharge capacity of 150 mAh g⁻¹ at the high rate of 5 C. The novel GNDs coating proposed in this study provides a new strategy to improve the power and energy density for lithium-ion batteries.

Lithium-sulfur battery, which has high theoretical specific capacity and energy density, is considered to be one of the next-generation of rechargeable batteries. But the "shuttle effect" still hinders its application. Here, carbon/gelatin microcapsule (C/GM) as a micro-reactor for sulfur cathode to suppress "shuttle effect" is prepared. The submicron-sulfur particles, which are synthesized with the regulation of gelatin, are encapsulated in the C/GM so that a region-limited electrochemical reaction can be realized. Benefiting from the micro-reactor inhibiting the dissolution of polysulfide, the initial discharge specific capacity of lithium-sulfur battery with C/GM cathode is up to 1259.0 mAh/g and still retains 961.0 mAh/g after 100 cycles. Due to the sustainable source and facile method, the C/GM cathode is promising for the application of lithium-sulfur batteries.

Silicon-graphite (SiG) electrodes are attractive candidates as anodes for Li-ion batteries due to their high theoretical specific capacity. However, repeated lithiation/delithiation during charge/discharge cycling causes significant morphological changes of the silicon particles. This results in the formation of highly porous silicon structures and severe side reactions at the silicon/electrolyte interface. To quantify these morphological changes, small-angle neutron scattering (SANS) was applied with selective contrast matching of Si nanoparticles (200 nm diameter) and the surrounding electrolyte decomposition products. Using electrolytes consisting of 1.5 M LiPF₆ dissolved in either deuterated or protonated ethylene carbonate (EC) resulted in solid-electrolyte-interphase (SEI) compounds with scattering length densities either matching or mismatching that of the Si nanoparticles. SiG anodes with 35 wt% silicon nanoparticles were aged for 10 and 20 charge/discharge cycles against capacitively oversized LiFePO₄ cathodes. Afterwards, the morphological changes and size distribution of the SEI compounds were evaluated by means of ex-situ SANS measurements of the SiG electrodes in their fully discharged state. Transmission electron microscopy (TEM) images of the pristine and cycled silicon nanoparticles complement the interpretation of the SANS analysis.

High-power lithium ion batteries have become the development focus of electric vehicles and large-scale energy storage devices. But it is also particularly critical to further study their hazardous properties under abuse conditions because higher capacity is more catastrophic. In this study, overcharge tests of 43 Ah cubic lithium ion batteries with different charge rates are conducted to study the thermal runaway behavior and parameter characteristics. Material characterization and thermal analysis tests further explain the overcharge mechanism. The emergence of voltage platform during overcharge is considered to be a significant characteristic for the high-power batteries which can be considered as an important criterion for suppressing thermal runaway. The reason for the appearance of the voltage platform is further discussed and the relevant thermal runaway critical parameters near the voltage platform under different overcharge rate are summarized. Thermal runaway risk assessment of overcharge and the critical parameter analysis of early warning are established to provide references for battery management system.

Recently, because of their cost effectiveness, high safety and environmental friendliness, zinc-ion batteries (ZIBs) are receiving enormous attention. Until now, aqueous-based ZIBs have been the focus of attention. However, the issues regarding hydrogen evolution, and zinc electrode passivation as well as dendrite formation limit their practical application. In this work, a biocompatible, stable and low-cost choline chloride/ urea (ChCl/urea) deep eutectic solvent is reported as an alternative electrolyte for rechargeable ZIBs based on delta-type manganese oxide (δ-MnO₂) intercalation electrode. The behavior of the zinc electrode on stripping and deposition in ChCl/urea electrolyte was examined. Besides, the charge storage and charge-transfer characteristics of the battery was studied. The results showed that there was no sign of dendrite formation on the zinc electrode during long-term cycling. Consequently, the fabricated battery exhibited good electrochemical performance with the maximum specific capacity of 170 mAh/g and good cyclability. In addition, the system showed reversible plating/stripping of zinc (Zn) without dendrite formation and no passivation layer on the zinc electrode. Hence, the results confirmed the reversible intercalation of Zn from the deep eutectic solvent ChCl/urea into the δ-MnO₂ electrode. Overall, the proposed electrolyte shows good promise for Zn/δ-MnO₂ battery system.

This paper conducts battery cyclic life tests under a full state-of-charge range (0-100%) and five partitioned state-of-charge ranges (0–20%, 20%–40%, 40%–60%, 60%–80% and 80%–100%). The attenuation of state-of-health indicator parameters along with cycle times under different state-of-charge ranges is compared. For the batteries cycled under 20% state-of-charge depth, loss of lithium inventory (LLI) is the leading factor resulting in capacity degradation. Expanding cycle state-of-charge depth accelerates the loss of electrode active material, but has little effects on LLI. When suffering identical cycle times, the sum of the decrements of state-of- health indicator parameter related to LLI under the five partitioned state-of-charge ranges is equal to 0–100% state-of-charge, which proves the additivity of LLI. Considering the linear correlation between capacity and state-of-health indicator parameters, a linear regression capacity model is established. Then, based on the additivity of LLI and capacity estimation model, an innovative evaluation method of battery lifetime with less testing time consumption is proposed, which conducts cycle aging tests under the partitioned state-of-charge ranges replacing full state-of-charge range to reduce testing time. Using this method, time consumption can be reduced by 75%, and the estimation error of capacity and lifetime is 3% and 10% respectively.

A composite separator with a tunable pore structure is prepared by coating a porous expanded dickite layer on a cross-linked nonwoven fabric. The expanded dickite is prepared by rapidly calcining the mixture of a dickite-urea intercalation complex and potassium chlorate (KClO₃). Moreover, the ratio of the external urea outside the dickite-urea intercalation complex and KClO₃ significantly determines the energy released by the reaction of urea and KClO₃, and further affects the expansive degree and functional group characteristics of the dickite. When the ratio of external urea to KClO₃ is 0.448, the porous expanded dickite with hydroxyl groups shows an average layer gap of 0.212 μm. The composite separator coated with porous expanded dickite has obvious pore morphology characteristics similar to the expanded dickite, and displays a higher porosity (61.6%), electrolyte uptake (0.861 g cm⁻³), ionic conductivity (3.157 mS cm⁻¹) and discharge capacity (152 mAh g⁻¹) than commercial Celgard 2400. Using this composite separator, LiFePO₄/Li cells exhibit an excellent rate capability and acceptable cycling stability, indicating that nonwoven coating by porous expanded dickite is a kind of the high-performance separator for lithium-ion batteries.

An essential ingredient in modeling the response of lithium in an all-solid-state lithium battery is a theory for the large deformation elastic-viscoplastic response of lithium. In this paper we report on a such a theory. The material parameters for the theory have been calibrated using stress-strain data from direct tension tests on polycrystalline lithium specimens reported recently in the literature. The theory has been implemented as a user-material-subroutine in a finite element program. This simulation capability should be useful in the design and development of lithium metal solid-state-batteries.

Herein, we describe the preparation of waxberry-like TiO₂@carbon core-shell composites through one-pot in-situ polymerization and a subsequent calcination process using polythiophene as both a carbon and a sulfur source. This simple preparative process allows for the simultaneous introduction of sulfur into the TiO₂ and carbon (STiO₂@SC). The morphology, structure, and electrochemical performance were studied in detail. The introduction of sulfur and the core-shell structure afford STiO₂@SC composites with high-pseudocapacitive sodium storage capacity and are thus considered promising anode materials for sodium ion batteries. STiO₂@SC composites deliver high reversible capacity (212.9 mA h g⁻¹ at 0.2 A g⁻¹), superior high-rate capability (121.2 mA h g⁻¹ after 2000 cycles at 1 A g⁻¹), excellent cycling stability (capacity retention of ∼100% except 1st cycle at 1 A g⁻¹), and stability against high current variations.

Ionic liquids are promising electrolytes for the primary Mg-air batteries. Three electrolytes, including pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid, 50 mol.% butyl acetate and 50 mol.% water were studied. Attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy were used to examine discharge performance and the effects of butyl acetate and water additions. Galvanostatic measurements indicate that butyl acetate is an excellent additive, which can significantly improve the battery performance by reducing electrolyte impedance by increasing conductivity. However, while water also improved electrolyte discharge performance, it was consumed by the hydrogen evolution reaction over the 72 h discharge.

Lithium dendrites may cause internal short-circuiting, fires, and even explosions. Unfortunately, the study of dendrites has been hindered by the impossibility of in situ observations. This work proposes a new double-scale in situ experimental setup that records the dendrite evolution of half and full cells during small-current-density electrochemical testing. The experiments confirmed that dendritic growth eventually connects the cathode to the anode, with significant effects on the cell voltage. In the full and half-cells, the attached dendrites decreased and increased the voltage, respectively. During discharge, the bubbles generated by the side reaction affected the dendrite evolution in both cells. A detailed model of lithium dendrite evolution mechanism in the anode is also proposed.

CoSn₂/SnO₂/C nanocomposites were synthesized by a simple mechanical solid-state synthesis method using a disproportionation reaction of SnO and a stable formation of CoSn₂. The synthesized CoSn₂/SnO₂/C nanocomposites were composed of small CoSn₂ (5–10 nm) and SnO₂ (∼5 nm) nanocrystallites within amorphous C matrices, whose electrochemical performances were tested for use as Li-ion battery anodes. Additionally, the electrochemical reaction mechanism during Li insertion/extraction was characterized thoroughly using ex situ extended X-ray absorption fine structure analyses. The CoSn₂/SnO₂/C nanocomposites showed high electrochemical performances with a high reversible initial capacity of 803 mAh g⁻¹, an excellent cycling behavior (571 mAh g⁻¹ after 500 cycles), and a fast C-rate performance (approximately 645 mAh g⁻¹ at 1C rate and 560 mAh g⁻¹ at 3C rate). The high electrochemical performance of CoSn₂/SnO₂/C nanocomposites demonstrated its promise as a new high-performance Li-ion battery anode.

In our prior study, ultraviolet (UV) light was used for the first time to improve long-term cycling of lithium-ion battery (LIB) electrodes. It was found that UV treatment of the anode resulted in thinner solid electrolyte interphase (SEI) layers, higher capacity retentions, and lower charge transfer resistance after cycling. In this study, pristine graphite powders and polyvinylidene fluoride films (binder) with/without UV treatment were individually analyzed before cell assemblies. X-ray photoelectron spectroscopy (XPS) analysis showed a 300% increase in atomic percentage of oxygen on the graphite powder surfaces after UV treatment. However, fluorine level of the binder film decreased by more than 10%. The PVDF film also expanded in thickness by 3.7% after the UV treatment for 40 minutes, indicating scissions of the polymer backbones. The changes in PVDF weight, thickness, and fluorine atomic percentage from XPS peaks also indicated the release of fluorine containing gases (e.g., hydrogen fluoride and difluoroethylene gas) after crosslinking and scission of the PVDF. Although UV light was found to partially decompose PVDF in this study, it helped to increase oxygen level on the graphite, which, resulted in a thinner SEI layer, lower resistance, and eventually higher capacity retention as shown in our prior study.

Nanosized Si-based materials have been extensively investigated because of their high gravimetric capacity and stable cycle performance. However, the tap density of nanosized materials is poor, leading to poor volumetric capacity. In this regard, micrometer-sized Si nanoparticles and carbon composites have been introduced to improve the volumetric energy density of Li-ion cells. However, most synthesis methods for these Si/C composites are complex, and thus, only a few methods among them are scalable for mass production. Herein, a scalable solid-state synthesis through self-assembly due to the relative miscibility of hydrophobic and hydrophilic precursors is introduced to obtain micrometer-sized porous carbon spheres containing nanosized Si particles. The self-assembly synthesis uses hydrophilic Si/SiO₂ core-shell nanoparticles, hydrophilic phenolic resins, and hydrophobic fumed silica. Because phenolic resin melts and Si/SiO₂ core-shells are miscible, the Si/SiO₂ core-shells are embedded in the phenolic resins. Immiscible phenolic resin melts and fumed silica lead to the formation of spherical resins. Eventually, the self-assembled micrometer-sized Si/C composite spheres are obtained after heating and HF etching. The tap density of the self-assembled Si/C spheres is much higher than that of the bare Si nanoparticles. In addition, the self-assembled Si/C composite shows excellent cycle performance because of voids in the composite.

On the basis of a previously developed measurement method [M. Bockelmann, M. Becker, L. Reining, U. Kunz, and T. Turek, J. Electrochem. Soc., 165 (13), A3048 (2018)] the influence of current load interruptions, KOH electrolyte composition, temperature, and forced electrolyte convection on the anodic passivation of zinc was investigated in this study. Our aim was to find appropriate experimental conditions which could allow a long-term usability of the zinc anode without formation of passive films. We found out that interruptions lasting several minutes during galvanostatic dissolution of zinc, as well as increasing temperature and raising concentration of OH⁻ ions in the electrolyte, effectively prolonged the service life of the electrode, but could not fully prevent it from passivation. On the contrary, increasing concentration of zinc oxide in the electrolyte enhanced the direct oxidation of zinc. However, application of sufficiently strong electrolyte convection and electrode overpotentials below a limiting value of about 0.1 V, allowed for electrode dissolution times of more than 1000 minutes without any indication of passive film formation. Therefore, the passivation of zinc anodes can be effectively avoided in cells with forced electrolyte convection and limited current densities.

Lotader 5500, a commercially-available polyethylene-co-ethyl acrylate-co-maleic anhydride thermoplastic elastomer, is investigated as a new binder for Li-ion battery composite electrodes with LiFePO₄ and Li₄Ti₅O₁₂. This binder was chosen to enhance the cohesion and adhesion properties of the composite electrode it binds through its reactive functional groups; moreover, the absence of fluorine in its composition renders it more suitable than polyvinylidene fluoride (PVDF) in the battery recycling process, which often relies on pyrolysis. Lotader 5500's insolubility in a carbonate electrolyte is demonstrated, as well as its similar electrochemical behavior to PVDF in the 50 mV to 4.2 V range vs. Li⁺/Li. After demonstrating the high-rate performance of the half-cells, full cells were assembled, and cycled 1,000 times (charged at a constant voltage of 2.4 V and discharged at 10D), and all exhibit a final capacity of approximately 70 mAh.g⁻¹.

Diazonium chemistry was used to enrich Kynol carbon cloth with catechol (dihydroxybenzene) moieties as redox agents. Comprehensive surface analyses (combining BET, SEM, TGA, and TGA-GC/MS) were carried out to evaluate the effect of redox molecules grafted over the carbon cloth surface. Electrochemical deprotection of 3,4-dimethoxyaniline grafted to the electrochemically active catechol, followed by electrochemical assessment in a three-electrode cell, shows a faradaic contribution due to redox reactions from the catechol-grafted moieties. Galvanostatic measurements underline the remarkably stable performance of this redox reaction, which permits over 3,000 cycles.

Novel copper-doped manganese ferrite nanoparticles were synthesized using a low-cost facile route via. hydrothermal method which provided high surface area and good conductivity for use as functional materials for storing and producing energy. A "hybrid mix" of the nano-ferrites with polyaniline showed a phenomenal influence on the investigated electrochemical properties. The hybrid mix gave maximum specific capacitance of 478.797 mAh/g of the symmetrical supercapacitor at 1 A/g current density and displayed an excellent cycling stability with capacitance retention of 78% after 5000 cycles. Morphology and structural analysis was carried out using Transmission electron microscope, Field-emission scanning electron microscope, and Fourier transform infra-red spectroscopy in detail. The interactive mechanism between the Cu_xMn_(1-x)Fe₂O₄ and PANI in the Cu_xMn_(1-x)Fe₂O₄@PANI hybrid electrode material was investigated using RAMAN and X-ray photoelectron microscopy. In addition, the proposed energy storage system has been constructed without using any binder which simplified the electrode fabrication process by preventing the contact resistance between the electrode and current collector.

With the increasing number of electric vehicles, inevitable crash accidents, vibration and foreign objective penetration potentially generate catastrophic consequences such as fire or explosion. Unlike traditional engineering materials or structures, LIBs exhibit multiphysical behaviors including mechanical deformation/failure, thermal conduction, series of electrochemical and chemical reactions, upon mechanical abusive loading. Therefore, developing computational frameworks capable of describing multiphysical behaviors of cylindrical batteries in crash safety design of electric vehicles based on commercially available platform is in pressing need. In this paper, based on the widely used LS-DYNA software platform, a multiphysics model with the comprehensive coupling of mechanical, battery, short-circuit, exothermic and thermal models are established. Models are validated by the in-house designed experiments. Further, parametric studies based on the established model demonstrates that a larger indentor leads to a later onset of internal short circuit (ISC) for LIBs but result in a higher peak battery temperature. On the other hand, an ISC will be triggered early if the compressive loading is applied near the ends of battery cells. This study provides an accessible, fast and accurate computational framework for safety design, assessment and improvement of lithium-ion batteries and electric vehicles in harsh mechanical scenarios.

In this first part of a two-part study of the synthesis, microstructure and electrochemical properties of ball milled silicon-tungsten alloys (Si_100-xW_x, x = 15, 20, 25, 30), the ball milling process is discussed in detail. The phase evolution was quantitatively followed during milling, allowing for a detailed understanding of the ball milling process. A volume element model of the process was developed that uses only three parameters that are directly related to the milling conditions. This model was found to well explain the ball milling process and suggests that energy initially accumulates in the Si and W powders after every ball collision. Eventually the stored energy overcomes activation energy for the reaction of Si and W to form Si₂W. The kinetics of these processes and the tendency for reactants to cake in the mill are important parameters to consider for the practical synthesis of different Si-metal alloy materials.

Based on fundamental electrochemical theory, an impedance model of a Nickel-Metal Hydride (NiMH) battery considering blocked-diffusion with frequency dispersion has been developed in this study. The impedance model accounts for electrochemical mechanisms during the decrease in the state of charge of a NiMH battery. The a.c. diffusion mechanisms in the NiMH battery during electrochemical impedance spectroscopy (EIS) tests can be modelled through a Warburg element considering blocked-diffusion with frequency dispersion. The Warburg element is analogous to a transmission line circuit comprised of distributed constant phase elements connected in parallel with resistors attributed to the resistance of diffusion processes. The NiMH impedance model is applied to EIS measurements carried out after discharging a NiMH battery pack. The impedance model can reproduce the straight-line EIS measurements of the NiMH battery represented in the low frequency range of the Nyquist plot. The change in slope of the straight-line EIS measurements at low frequencies can be related to nonhomogeneous electrode ion concentration and can be attributed to roughness of the NiMH electrode. This study has demonstrated that it is possible to gain an insight into the electrochemical processes of NiMH by combining fundamental theory of battery electrode and EIS measurements in a complementary manner.

Blending of the popular anodic material graphite with hard carbon is one of the suggested way to improve the rate capability and cycle life performance in Lithium ion batteries. Based on this concept, this work proposes a high-rate battery with optimal blend composition, which can undergo high charge rate with high cycle life durability. This is done by suitably blending the existing graphite based anode with low cost hard carbon material, which improves the rate limiting solid phase diffusion. In this paper, an electrochemical model is developed for cell comprising of electrode with multiple active materials. Simulation study confirms that the hard carbon layer on graphite matrix facilitates charge transfer and creates additional electronic conduction pathways. Electrochemical model is used to devise a generic methodology to optimally design lithium ion cell comprising of anode with multiple active materials. In particular, the optimal composition of 30% hard carbon (HC) and 70% natural graphite (NG) exhibits high rate charging capability compared to pure NG. Efficacy of the proposed solution is also shown by demonstrating the high rate capability of the battery fabricated in the laboratory and prediction from proposed model are in good quantitative accord with the test result.

The state of a lithium (Li)-ion cell as a function of measureable quantities like cell voltage and current is not available in closed form without simplifying assumptions like uniform reaction rate, thus limiting the applicability of reduced order electrochemical models for on-board estimation. In the present work, an analytic form for non-uniform reaction rate profile is derived under certain limiting conditions. Using this form and polynomial approximations for the concentration profiles, a direct non-iterative solution scheme is developed for estimation of cell voltage, state of charge (SOC) and other internal variables. The predicted cell voltage is validated against experimental results for commercial cells while the internal variables are verified against the full pseudo 2 dimensional (P2D) model. The results show that, in spite of the order reduction, the model predicts cell voltage as well as the physical processes of the Li-ion cell accurately with less than 1% error for a wide range (0.2C – 5C) of operating conditions. The self-consistent predictive capability along with low computational cost, makes the proposed model an ideal candidate for physics based on-board state estimation.

Rechargeable Zn metal aqueous batteries featuring low cost, superior safety, and ultrahigh volumetric capacity are of great interest for large-scale applications. However, their practical implementation is hindered by poor reversibility and short cycling stability, which fundamentally result from the corrosion and the dendritic growth of the Zn metal anode in the aqueous electrolyte. Stabilization of Zn metal is therefore essential to achieve satisfactory performances. Here, we report a new electrolyte system containing a thickening agent (fumed silica) that can immobilize the water molecules and a homogenizing agent (fatty methyl ester ethoxylate) that assists in smoothing the Zn²⁺ cations deposition, which effectively alleviates the water-induced corrosion reaction and suppresses the Zn dendrite formation. Zn/Zn symmetric cells in the new electrolyte, therefore, show extraordinary reversibility with a coulombic efficiency of 99.5% that is the highest among those of the reported symmetric cells and a long cycling stability of 1500 h. Furthermore, the Zn-MnO₂ full cell in this work exhibits equally excellent cycling stability with low capacity loss of 0.002% per cycle, which is superior to those of previously developed Zn metal batteries. This study offers a promising approach to stabilize Zn metal and enable high-performance Zn metal aqueous battery.

Potassium-ion batteries are now regarded as powerful competitors to lithium-ion batteries due to their merits of low-cost and abundant resource contrasted with state-of-art lithium ion batteries. However, the extremely flammable electrolytes may cause severe safety issues. Herein, we report an intrinsic non-flammable trimethyl phosphate-based potassium ion battery electrolyte. The problem of its poor electrochemical compatibility with graphite electrode is successful settled by using concentrated salt electrolyte. Graphite anode with high concentrated potassium bis(fluorosulfonyl)imide (KFSI)/trimethyl phosphate (TMP) electrolyte demonstrates high Coulombic efficiency and stable cyclability after 80 cycles. The performance enhancement mechanism is further probed via X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The flame-retarding character of the concentrated electrolyte with stable electrochemical performance paves the way toward low cost and highly safe potassium ion batteries.

In this paper, the Fe-Compounds (FeF₂ and Fe₂O₃) doping porous carbon nanofiber & carbon nanotube (FeCD-PCNF&CNT) composite material is firstly prepared by electro-blown spinning followed by pretreatment and one-step carbonization & chemical vapor deposition (CVD) processes. The CNTs are uniformly growing on the PCNF skeleton which deeply increased specific surface area (from 334.066 to 743.402 m² g⁻¹) and enhanced electrical conductivity (from 42.22 to 149.48 S cm⁻¹) comparing to those of PCNF, and large number of hierarchical-pores are existed. In addition, the Fe-Compounds are uniformly distributed on the PCNF skeleton which provided numerous active sites. The obtained FeCD-PCNF&CNT as an anode material for Li-ion capacitors exhibited high energy density and power density (76.1 Wh kg⁻¹ at 0.075 kW kg⁻¹, 15.4 Wh kg⁻¹ at 7.5 kW kg⁻¹), which had broad application prospect in the energy storage field. Moreover, the composite materials with special structure and excellent properties may realize the other applications in the fields of adsorption, water treatment, etc., and the prepared method has a great industrialization potentiality.

The N-doped porous carbon materials were prepared via the co-carbonization of cellulose acetate fiber and urea. The cellulose acetate fiber was derived from waste cigarette and urea was used as the nitrogen source and the activating agent. The carbonization temperature has an important effect on the specific surface area, porosity and nitrogen content of as-prepared porous carbon materials. When the carbonization temperature was 750°C, as-prepared CN-750 with an average pore size of 4.84 nm exhibited the highest specific surface area of 734 m²·g⁻¹. The sample of CN-600 synthesized at 600°C showed the highest nitrogen content of 11.69 at%. Moreover, as-prepared samples with disordered pores showed a low graphitization degree and a large interlayer space. The specific capacitance of CN-750 is 152 F·g⁻¹ at the current density of 1 A·g⁻¹, which is higher than that of CN-600 and CN-900. After 5000 cycles, the capacitance retention of CN-600, CN-750 and CN-900 is 91.9%, 93.1% and 95.1%, respectively. The energy density of CN-750 is 5.28 Wh·kg⁻¹ at the power density of 250.1 W·kg⁻¹ and it retains 6.09 Wh·kg⁻¹ at the power density of 24.97 W·kg⁻¹. Our study indicates that the waste cigarette butts can be effectively recycled via the co-carbonization method, and as-prepared N-doped porous carbon materials with an excellent cycling stability and a reasonable availability are promising candidates for the electrode materials of supercapacitors.

All solid state 3D batteries are pursued for their increased safety and high power capabilities. At present conformal coating of the solid electrolyte remains one of the key hurdles for the implementation of such devices. In the present work we investigate atomic layer deposition (ALD) as means of conformal deposition of lithium phosphate (Li₃PO₄) and nitrogen doped lithium phosphates (LiPON). These processes are characterized here to obtain the highest possible Li-ion conductivity. Li₃PO₄ is shown to yield a conductivity of 10⁻¹⁰ S/cm at 25°C. On the other hand, an optimized LiPON process gave rise to a Li-ion conductivity of 5⋅10⁻⁷ S/cm at 25°C. In addition, good conformality of the LiPON process was shown on high aspect ratio pillars. Furthermore, a solid state battery device was fabricated comprising a Li₄Ti₅O₁₂ cathode, a 70 nm thick ALD LiPON solid electrolyte and a metallic lithium anode. This finding indicates that a layer down to 70 nm can be made pinhole free.

The thermal runaway of a lithium ion battery (LIB) during a nail-penetration test was investigated using an LIB internal short circuit observation system equipped with an X-ray scanner (LiSC scanner). Using high-speed moving images and high-precision voltage measurements, the layer-by-layer internal short circuit caused by the nail was clearly observed during nail motion. Following this motion, gas generation outside the cell, which is well-known in thermal runaway, was observed. The main causes of smoke are speculated to be the boiling of the electrolyte and/or decomposition of the active materials owing to heating by the short circuit current. The initial behavior of the short circuit before gas generation was clearly observed. Therefore, gas generation, which is well-known to indicate an internal short circuit of the cell, and the electrical behavior of the short circuit during the nail-penetration test were observed separately. This LiSC scanner allowed us to analyze the details of the internal short circuit of the cell, and it is expected to lead to significant advancements in the safety of LIBs.

Silicon-graphite (Si/C) composite anodes are used to increase total anode capacity while maintaining a tolerable degree of active material volume expansion. However, increasing the Si/C ratio does not directly lead to an increase in the accessible capacity because excessive volume expansion can lead to unacceptable cell pressure or electrode porosity. To predict the accessible capacity as a function of Si/C ratio, we integrated mechanical behavior for individual cell components into our previous battery model that couples mechanical and electrochemical phenomena and then simulated a full charge of a pouch cell with foam packing. The simulations were used to determine the anode accessible capacity as a function of Si/C ratio, based on practical pressure and porosity design limitations. The resulting predictions illustrate the tradeoff between the capacity gained by increasing the Si/C ratio and the accessible capacity lost based on the pressures that build up in the cell due to the interconnected mechanical and electrochemical phenomena. For a given set of cell and pack design requirements, battery designers can use these types of simulations as a tool to maximize accessible capacity of an operating cell by selecting appropriate cell/pack materials and identifying optimal Si/C ratios.

Olivine-type LiMnPO₄ was synthesized via a citric-acid assisted sol-gel method. The structural evolution of the as-prepared material during calcination and the crystallization of LiMnPO₄ was investigated by XRD measurements. A reaction mechanism including two intermediate phases was derived for the synthesis. Furthermore, the electrochemical Li extraction and insertion processes were studied by in situ/ex situ XRD and MAS NMR measurements. The phase transition from LiMnPO₄ to MnPO₄ and vice versa proceeds via a two-phase mechanism. The ³¹P MAS NMR spectra of MnPO₄, which forms upon delithiation as confirmed by XRD patterns, shows a very broad signal. Possible explanations for the large width of this signal are given and evaluated.

Increased electroactivity of polyaniline prior doped with lithium ions is observed during polymerization by cyclic voltammograms (CV) compared with pure polyaniline. The electrochemical performance of a three-dimensional nickel foam-supported polyaniline composite prepared by electrophoresis and a casting process was investigated at different low-vacuum pressures for casting the aforementioned slurry. An appropriate vacuum pressure of 3000 Pa was certified by cyclic voltammetry and scanning electron microscopy. The nickel foam-supported polyaniline composite cathode were prepared and observed with prohibited hydrogen evolution and the enhanced conductivity in a manganese acetate-zinc acetate solution electrolyte system with lithium ions additive. The deposited zinc anode prepared by co-electrodeposition of zinc-manganese exhibited with high discharge voltage and stable discharge platform. The zinc-manganese-deposited zinc//nickel foam-supported polyaniline composite battery exhibited significant improvement in the capacity density and cycle performance. A discharge capacity density of 142.3 mAh.g⁻¹ was attained by the battery, and it was maintained more than 94.7% of the original value after 60 cycles, and there was no distinct change in the coulomb efficiency with an average value of 90% over the experiment, which indicates that the present cell has promising possibility for use as an energy storage or high-performance rechargeable battery.

Lithium- and manganese-rich layered oxide-based cathode active materials (often referred to as HE-NCM) exhibit high reversible specific capacity (≈250 mAh/g) and could improve future lithium-ion batteries in terms of energy density and safety, while offering lower cost. Unfortunately, drawbacks such as voltage-fading, hysteresis, and increasing cathode impedance over charge/discharge cycling have so far hindered its commercialization. In this study, we examine the reasons and the implications of the high resistance build-up of this material in graphite//HE-NCM full-cells. Impedances/resistance were obtained either by electrochemical impedance spectroscopy (EIS) with a micro-reference electrode or by current pulse measurements (so-called direct-current internal-resistance (DCIR) measurements). These data show that the so-called activation of the material above 4.5 V vs. Li⁺/Li leads to an asymmetric high charge-transfer impedance at low state-of-charge (SOC) between charge and discharge, manifested as an anomalous cell resistance hysteresis which increases over cycling and with increasing upper cutoff potentials. These findings are rationalized by reversible transition-metal migration phenomena.

Conducting polymers, which have a great potential for use in many technological application areas, can be used to design new selective, sensitive, highly efficient and practical sensor platforms. Herein, a pyrene-substituted 2,5-dithienylpyrrole (TPP) has been synthesized and its conductive polymer has been coated electrochemically on the ITO electrode surface to form a new sensor platform. After electrochemical and surface characterization of conducting polymer based sensor platform, its electrochemical responses to different metal ions have been investigated in aqueous media. It has been determined that P(TPP) displays excellent potentiometric response to Fe(III) ions while there is no significant electrochemical signal observed in other metal ion solutions including Fe(II), Zn(II), Cu(II), Hg(II), Cd(II). P(TPP) sensor platform has exhibited high stability, sensitivity, reproducibility toward the determination of Fe(III) with a good detection limit of 1.73 × 10⁻⁷ M. The sensor platform has great potential for disposable low-cost metal ion sensing platform which is convenient in-field testing application could be used in aqueous and biological samples.

In this research, conducting polymer – polypyrrole (Ppy), was electrochemically polymerized on the indium tin oxide coated glass (glass/ITO) electrode. The adhesion of Ppy on the surface of ITO was improved by modification with triethoxymethylsilane (TEMS). Potential cycling was applied for electrochemical deposition of Ppy layer and cyclic voltammograms were recorded during the deposition to monitor polymerization process. Cyclic voltammetry and the potential pulse sequence (PPS)-based chronoamperometry methods complemented the registration of absorbance spectra of glass/ITO_(TEMS)/Ppy at various pH and different concentrations of CO₂. The applicability of glass/ITO_(TEMS)/Ppy electrode in the design of electrochromic sensor sensitive toward CO₂ has been evaluated. Cyclic voltammetry based experiments at different potential sweep rates in presence and absence of CO₂ were performed in order to evaluate charge transfer phenomenon in glass/ITO_(TEMS)/Ppy structure.

A novel nanocomposite of hexagonal cobalt oxide nanosheets (HCONS) homogeneously dispersed on a carbon matrix of reduced graphene oxide (RGO) and multiwall carbon nanotubes (MWCNTs) has been developed. The HCONS@RGO@MWCNT nanocomposite was prepared successfully via a hydrothermal process followed by calcinations for the individual and simultaneous non-enzymatic detection of ascorbic acid (AA), uric acid (UA), and dopamine (DA). The morphology and structure of the HCONSs and synthesized nanocomposite were analyzed by X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and Raman spectra. The electrochemical performance of the nanocomposite was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the simultaneous determination of the AA, DA, and UA were examined using differential pulse voltammetry (DPV) with linear ranges of (12.5−1382), (1.6–23.6), and (46.5–806.5) μM, and lower detection limits of 12.5, 0.012, and 1.5 μM (S/N=3), respectively. The proposed electrode exhibited an excellent selectivity, long-term stability, and good reproducibility. Therefore, the developed nanocomposite is a promising material for non-enzymatic electrochemical sensors.

The in-situ monitoring of electrochemical deposition (ECD) processes is still a challenge regarding the measurement of the effective temperature of the substrate and the formation of mechanical stress in the layer under given plating conditions. Monitoring problems can be solved by applying a pre-coated fiber Bragg grating (FBG) to the electrolytic process as the shift of the Bragg wavelength is affected by both the temperature of the electrolyte near the substrate and the stress formation in the growing layer. The experimental FBG set-up and the quantitative determination of temperature- and stress-related strain is described for a nickel-iron electrolyte.

Organic semiconductors are among the most promising next generation materials for biosensors as the greener and cheaper alternative to transition metal-based electrodes. This work focuses on the production and analysis of organic p-type semiconductor-based glucose biosensors. The compressed graphite electrodes have electrochemically been modified with 9-ethyl-9H-carbazole (CzEt), 9-phenyl-9H-carbazole (CzPh), N,N,N-triphenylamine (TPA) and with cross-linked glucose oxidase (GOx). Response of the created biosensors to the changing concentration of glucose has been assessed by cyclic voltammetry. The electrochemical impedance of these organic semiconductor layers was investigated by using an electrochemical impedance spectroscopy method. Herein, we aim at drawing a picture of the electro-polymerized derivatives and the applicability of p-type carbazole and triphenylamine-based organic semiconductors for amperometric biosensors.

Sensitive and rapid detection of pesticides in food has become an important and crucial research area due to the extensive use of agriculture residues and stringent environmental protection acts. In present work, an electrochemical nanohybrid sensor was facilely developed based on carboxymethyl cellulose (CMC) fuctionalized carbon nanotubes (CNTs). The sensor shows high sensitivity, excellent stability and good anti-interference capability in the detection of carbendazim (MBC) by differential pulse voltammetry method. Under optimized conditions, it exhibits a wide linearity of 0.03 μmol·L⁻¹ – 10 μmol·L⁻¹ with a low detection limit of 0.015 μmol·L⁻¹. In real samples analyses for peer and kiwifruit, the proposed sensor shows good recoveries which are comparable with that of the conventional HPLC method. In addition, the oxidation mechanism of MBC at the nanohybrid sensor was studied using voltammetric methods and validated according to the density functional theory (DFT) calculation. The results reveal that the oxidation of carbendazim is a typical adsorption-controlled electrochemical oxidation process proceeding with four protons and four electrons. The proposed nanohybrid sensor is a promising alternative to the currently used methods for carbendazim detection and our results provide a new insight in MBC electrochemical oxidation mechanism.

A sensitive and simple electrochemical sensor for determination of norepinephrine (NE) was developed. The electrode (ERG-UiO-67-bpy/GCE) was fabricated by modifying the glassy carbon electrode with a Zr (IV) metal-organic framework (MOF) with 2,2'-bipyridyl-5,5'-dicarboxylate (UiO-67-bpy) and graphene oxide (GO), followed by electrochemical reduction of GO to ERG (electrochemically reduced graphene). The ERG and UiO-67-bpy components of the composite electrode show a synergic electrocatalytic effect, leading to much enhanced voltammetric response to the oxidation of NE. Comparative studies indicate that the hydrogen bonds between the bipyridyl moiety of the MOF and the 2-aminoethanol moiety of NE play an important role in promoting electron transfer on the electrode surface. Differential pulse voltammetry using the composite electrode shows a wide linear-response concentration range with a submicromolar detection limit of 0.026 μM. The sensor shows good reproducibility and stability and also be used for sensitive simultaneous detection of NE and uric acid.

A novel Hg²⁺ electrochemical assay was presented based on target triggered exonuclease III (Exo III) assisted dual cycle amplification and tetrahedron DNA (TDNA) nanostructures as efficient signal molecules carrier. The thymine bases rich (T-rich) hairpin 1 (HP1) was wisely designed with the significant report DNA (RDNA) sequence in the loop, which could be acted as probes for specially recognizing Hg²⁺ with formation of duplex-like structure through T-Hg²⁺-T coordination. This duplex-like structure could be digested by Exo III to release numerous Hg²⁺ for next cycle, accompanying with the generation of an important digestion product RDNA for opening hairpin 2 (HP2) on electrode. After the introduction of hairpin 3 (HP3) on electrode via strand displacement reactions, the RDNA could be released again for next cycle, leading to the assembly of large amounts of HP3 for decorating TDNA. Finally, by using the TDNA as carriers for loading substantial signal probe thionine (Thi), a remarkable electrochemical signal could be acquired for quantitative detection of target. As a result, the developed biosensor showed a low detection limit of 33 fM for Hg²⁺ determination. This strategy designed a novel electrochemical biosensor, which offered a new way for metal ion detection, showing potential applications in environmental monitoring.

A sensitive, selective, and stable electrochemical sensor based on Mn_1-xZn_xFe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) nanoparticle and Nafion-modified glassy carbon electrode (GCE) was designed and developed to detect Pb²⁺. The uniform and monodisperse Mn_1-xZn_xFe₂O₄ nanospheres were synthesized via a hard template-free (soft template) hydrothermal method. This research mainly focused on the influence of different Zn²⁺ substituting ratios in Mn_1-xZn_xFe₂O₄ on sensing characteristics of the sensor. The highest response value to 0.6 μM Pb²⁺ was observed for the sensor using Mn_0.4Zn_0.6Fe₂O₄. In addition, the influence of experimental parameters (e.g., the kinds of electrolyte, pH, deposition potential, and time) on sensing performance was studied. When measured in 0.1 M NaAc–HAc (pH = 2.0) at the deposition potential of −1.0V with the deposition time of 130 s, Mn_1-xZn_xFe₂O₄ and Nafion-modified GCE exhibited good sensitivity of 58.613 μA/μM, favorable repeatability, and an ultralow detection limit of 0.7 nM (based on S/N ratio  =  3). The superior sensing properties to Pb²⁺ were attributed to the bigger electrochemically effective surface area with the addition of Zn²⁺, high adsorption capacity, and high specific surface area of Mn_0.4Zn_0.6Fe₂O₄ nanospheres. Using Nafion also enhanced the adsorption capacity and stability of the modified electrode.

In this study, we first proposed a low-cost and highly reproducible method for the mass production of a novel biosensor electrode with self-assembled monolayer of gold nanoparticle on a micro hemisphere array. An ordered array of micro hemispherical features was formed on a 6-inch reclaimed silicon wafer using photolithography. Then, a thin gold layer was sputtered onto the hemispheres. The wafer was then immersed into a 5 mM ethanol solution of 1,6-hexanedithiol (1,6-HDT) to enable the attachment of one thio-end of 1,6-HDT to the thin gold layer. Finally, a colloidal gold (∼13.5 nm) solution was dripped onto the wafer and baked on a hot plate in such a way that the monolayer of gold nanoparticles could self-assemble on the 1,6-HDT surface. The features of the fabricated biosensor electrodes were then applied for non-enzymatic glucose detections. Chronoamperometry (CA) detection of glucose demonstrated that the proposed non-enzymatic glucose biosensor can operate in a linear range from 1.39 to 13.89 mM with a sensitivity of 336.1 μA•mM⁻¹•cm⁻² and a detection limit of 5.2 μM. The accuracy of the developed glucose biosensor reaches ±1.29%, which is significantly better than the FDA and ISO 15197 standard of ±15%. The relatively high repeatability of the proposed glucose biosensor can be attributed to the uniform semiconductor fabrication process and the extremely ordered self-assembled monolayer of gold nanoparticles. The proposed biosensor can be easily produced on a large scale, the cost of fabrication is low, repeatability is high, and is easy to preserve on a long-term basis.

In this work, a porous silicon nanostructure has been fabricated by electrochemical means and used as a thermal sensor. The thermo-optic effect in the near infrared region has been experimentally studied based on spectroscopy measurements. Values of the thermo-optic coefficient between 3.2 and 7.9·10⁻⁵ K⁻¹ have been obtained, depending on the porosity, reaching a maximum thermal sensitivity of 91 ± 3 pm/°C during the experiments carried out with the fabricated samples. Additionally, the oxidation process of the sensor at temperatures below 500 K has been studied, showing that the growth of the silicon oxide was dependent on the characteristics of the porous layers. Based on the experimental results, a mathematical model was developed to estimate the evolution of the oxidation process as a function of porosity and thickness.

This paper presents a new type of the working electrode - bi-Disc Glassy Carbon Electrode (b-DGCE). An innovative design of the electrode surface consists of two glassy carbon discs (ϕ = 1.0 mm) symmetrically placed on the lateral surface of the guidewire formed with chemically resistant resin. The results obtained during characterization of the electrode, conducted by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), were consistent with the reversible reaction theory. The b-DGCE was constructed and used as a working electrode for determination of vitamin K2 (VK2) by the differential pulse adsorptive stripping voltammetry (DP AdSV). The electrochemical behavior of VK2 on the b-DGCE was investigated. Parameters affecting the stripping performance, such as composition and concentration of the supporting electrolyte as well as several key instrumental parameters were investigated and optimized. Under the optimized experimental conditions, a linear voltammetric response was received for VK2 in the concentration range from 0.06 to 0.55 mg·L⁻¹ with limit of detection (LoD) of 0.017 for cathodic and 0.021 mg·L⁻¹ for anodic scans, for a short accumulation time of 10 s. Repeatability of the method, expressed as RSD (n = 5) was 2.12 and 1.37 mg·L⁻¹ for cathodic and anodic scans, respectively.

Herein, a simple and selective electrochemical sensor was proposed for non-enzymatic determination of hydrogen peroxide (H₂O₂). This sensor was fabricated by incorporation of the novel nanostructured orthorhombic vanadium pentoxide (V₂O₅) into the carbon paste electrode (CPE) which provides significant catalytic activities for H₂O₂ reduction. The electrochemical impedance spectroscopy (EIS) studies illustrated lower charge transfer resistance (R_ct) of the V₂O₅ modified CPE compared to the unmodified CPE. The effects of various experimental factors such as solution pH, applied potential and amount of modifier were studied in an amperometric mode. After optimization, the proposed method displayed a wide linear detection range from 5.0 to 1400.0 μM with a low detection limit of 2.5 μM based S/N = 3 and a response time less than 5 s. The sensitivity of 3.44 μA μM⁻¹ cm⁻² was acquired in the present method for H₂O₂ quantification is considerably better than other reported amperometric sensors with similar detection limits. In addition, the designed sensor depicted good reproducibility, remarkable selectivity, and excellent stability. The modified CPE was applicable for analysis of H₂O₂ in some cosmetic and personal care products.

A novel hierarchical Au/Ni/boron-doped diamond (BDD) heterostructure electrode was fabricated by two-step heat-treatment. The heterostructure that hierarchical Au/Ni nanoparticles are embedded on the surface of BDD was demonstrated by transmission electron microscope (TEM). Cyclic voltammetry (CV) and amperometric detection were used to test electrochemical properties of the prepared electrodes. The Au/Ni/BDD electrode exhibited enhanced catalytic activity and stability in glucose detection, as compared to that of the Au/BDD and Ni/BDD electrodes. On the optimal NaOH concentration and applied potential, the Au/Ni/BDD electrode exhibited an extremely wide detection range of 0.005–32 mM with high sensitivity of 1229.5 μAmM⁻¹cm⁻² and an excellent long-term stability (maintains 94.8% of initial current after one month). In addition, the prepared electrode also exhibited a low detection limit of 2 μM (S/N = 3), good selectivity and reproducibility. At last, the reasons for enhanced catalytic activity and excellent stability of Au/Ni/BDD electrode were discussed.

Reduced graphene oxide-nanocrystals has attracted considerable attention since it has great potential due to its great chemical activity, high mechanical stability and excellent electrical properties. But the synthesis of reduced graphene oxide-nanocrystals still faces challenges, for example introduce of RGO would contribute to change the morphology of nanocrystals. To address the challenge, we designed a simple method to prepare the common composite material and it was successfully adopted to fabricate glucose sensor with higher catalytic activity. Under the optimal conditions, the experimental results indicated that RGO-Pd NCs@CuO/GC electrode showed excellent electrocatalysis for glucose oxidation with a lower detection limit of 10 nM. This sensor was of excellent stability and sensitivity. This study not only provides a new sensor for selective and reliable detection of glucose but also offers a common and facile strategy for syntheses of nanocrystals supported on reduced graphene oxide.

An electrochemical sensor based on PEDOT:PSS-β-CD-SWCNT-COOH/GCE for highly sensitive analysis of shikonin (SHI) in PBS buffer solution was reported. PEDOT:PSS-β-CD-SWCNT-COOH composite was obtained by using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS), β-Cyclodextrin (β-CD) and carboxylated single-walled carbon nanotube (SWCNT-COOH) to modify glassy carbon electrode (GCE) and characterized by scanning electron microscopy and electrochemical impedance spectroscopies. In optimized conditions, PEDOT:PSS-β-CD-SWCNT-COOH had a high sensitivity to SHI and it could detect SHI in linear ranges 6 nM to 30 μM with a low detection limit of 1.8 nM. And a series of experiments showed that the modified electrode exhibited good repeatability, reproducibility, and selectivity to electrochemical determination of SHI.

In this study, pencil graphite electrodes were modified by electropolymerization of p-phenylenediamine polymer imprinted with diuron to develop a sensor for diuron detection. Polymer growth and template leach conditions were investigated for determining optimal settings in developing the sensor. Under optimal working conditions, the differential pulse voltammetric current response of diuron oxidation was linear in the range of 10–500 μM (R²: 0.9875) with a detection limit of 43.43 μM (S/N: 10). The molecularly imprinted polymer modified electrode showed selectivity and sensitivity for diuron compared to its structural analogues. The developed sensor was applied to the detection of diuron in water samples.

This study represents an electrochemical sensor to determine the hydroxylamine through voltammetry methods based on a screen printed electrode (SPE) modified with La³⁺-doped Co₃O₄ nanocubes. The La³⁺-doped Co₃O₄ nano-composite was prepared through an easy chemical reduction technique. The modified SPE presented good electrocatalytic performance toward hydroxylamine oxidation. The limit of detection (LOD) (S/N = 3) and sensitivity were obtained 0.08 μM and 0.037 μA/μM, respectively. The sensor was used for detecting hydroxylamine in (spiked) water samples.

In this study, we developed a super Nernstian pH sensitivity of InSn_xO_y (ITO) sensing film deposited on PET flexible through a simple sol-gel method for an extended-gate field-effect transistor (EGFET) pH sensor. We employed X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy to characterize the structural, morphological and chemical features, respectively, of the films prepared under three Sn concentrations (10, 15 and 20 mol%). The ITO-based EGFET device processed at the 15 mol% Sn concentration exhibited the highest sensitivity of 62.04 mV/pH, the lowest hysteresis voltage 2.60 mV and the smallest drift 1.08 mV/h among these concentrations. We attribute this behavior to the optimal Sn content in the ITO film to induce a large number of free electron, causing a lower sheet resistivity.

Electrolyte/semiconductor junctions have attracted considerable attention from different disciplines such as physical chemistry and electrochemistry in recent years. Here, we investigated a single-crystal gallium oxide (β-Ga₂O₃)-based electrolyte/semiconductor junction behaving similar to a Schottky type diode, determined its electrical properties and analyzed the junction characteristics under certain conditions (e.g., ionic strength, temperature, etc.). The junction was formed by adding an electrolyte layer with a specific ionic concentration (150 × 10⁻³ M) on top an n-type β-Ga₂O₃ substrate and a metal contact to assist I-V measurement. The junction diode exhibited rectifying behavior and good electrical characteristics such as an ideality factor of 1.8, a threshold potential (V_bi) of 0.74 eV and a Schottky barrier height (Ø_B) of 1.05 eV. The threshold voltage of the diode can be tuned by changing the ionic strength in the junction layer and the conductivity can be varied by changing the measurement temperature. The sensitivity of the conductivity of the diode to changes in the electrolyte concentration means that it can be used in various applications. As an application of the semiconductor/electrolyte junction, the selective detection of miRNA (let-7a, let-7f) molecules was demonstrated.

The development of new sensing platforms for the rapid, real-time, and onsite detection of metabolic compounds could provide significant opportunities for medical science, and healthcare applications. Microplates are standard tools that are widely used in cell biology, tissue engineering, or medical diagnosis. Here, we demonstrate for the first time the microplate-integrated amperometric biosensors for the rapid and sensitive detection of glucose and lactate. The sensor is constructed by printing carbon-graphite mediator paste as the working electrode, and Ag/AgCl paste as both reference and counter electrodes. The working electrode is then immobilized with glucose oxidase or lactate oxidase. The sensor shows a sensitive and rapid detection of glucose or lactate with a detection range from micromolar to millimolar and a short detection time of about 1 min. It is expected that the methodology can provide rapid, real-time, and onsite platforms for detecting a variety of metabolic compounds, and could provide new avenues for the fundamental studies and practical applications in cell biology, tissue engineering, or medical diagnosis.

A facile and sensitive chiral analysis for the recognition of tyrosine (Tyr) enantiomers has been designed based on teicoplanin (Tei) and a flower-like nanocomposite which consisted of copper-platinum core-shell microspheres and single-walled carbon nanotubes-molybdenum disulfide (Cu@Pt/SWCTNs-MoS₂). The flower-like nanocomposite was employed to improve the immobilization of the chiral selector Tei and the electrochemical performance. The nanocomposite was characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Raman spectrum, fourier transform infrared spectroscopy (FTIR), water contact angles and electrochemical methods. The interaction between Tyr enantiomers and the Tei/Cu@Pt/SWCTNs-MoS₂ chiral interface was determined via differential pulse voltammetry (DPV). The results exhibited enantioselective interaction between the modified electrodes and Tyr enantiomers, and a stronger interaction was obtained from L-Tyr than D-Tyr. The DPV responses were linearly dependent with concentration in the range of 10.0 μmol·L⁻¹ to 5.0 mmol·L⁻¹, and the limits of detection were 3.2 μmol·L⁻¹ and 4.7 μmol·L⁻¹ for L-Try and D-Tyr (at S/N = 3), respectively. The simple and cost-effective method opens up a new channel for the application of macrocyclic antibiotics.

This paper explores to use graphene as transparent interdigital transducer (IDT) electrode for a fully transparent surface acoustic wave (SAW) device due to its extraordinary electrical, physical and mechanical properties. The number of graphene atomic layers was firstly optimized for its best performance as the SAW electrode, and a 4-layered graphene IDT electrode, with aluminum doped zinc oxide, AZO, as the bus bar and wire bonding pad, was selected to fabricate fully transparent ZnO/glass SAW devices. The SAW resonators exhibited obvious resonant response at different wavelengths, and resonance signals with amplitude up to 20 dB were obtained with the transparency above 80%. The graphene-based transparent SAW sensor has been used for different sensing applications. Temperature sensing tests showed that the frequencies increase linearly with the increase of temperature, which has an opposite trend compared to that obtained from a conventional LiNbO₃ SAW device. The humidity sensing and human breathing detection have been demonstrated, and discontinuous respiration measurement can be used to distinguish the human respiration at the normal state or the state after exercise. Strong acoustic streaming and particle concentration using the transparent SAW devices have been achieved, which are suitable for microfluidic and lab-on-chip applications.

To develop a CaZrO₃ -based, high-temperature proton conductor with high conductivity and resistance to the reduced atmosphere, we used Sc as a substitute for In as the dopant in CaZrO₃. The electrical conductivity of CaZr_1-xSc_xO_3-α (x = 0.06, 0.12, 0.18, and 0.24) specimens was measured using the two-terminal ac method in an oxygen-rich atmosphere, hydrogen-rich atmosphere, and water vapor-rich atmosphere, at temperatures ranging from 573 K to 1473 K. The electrical conductivity of the CaZr_1-xSc_xO_3-α samples first increased and then decreased with the increase in amount of Sc₂O₃ doping, and it increased with an increase in temperature. The results of the H/D isotope effect measurement indicated that in the three different atmospheres, at temperatures from 573 K to 1273 K, protons are the dominant charge carrier. From the measurement of electromotive force, the theoretical (calculated) and the measured electromotive forces coincided. The proton mobility of CaZr_1-xSc_xO_3-α exceeded 90% in the hydrogen-rich atmosphere at temperatures from 573 K to 1273 K. At higher temperatures of 1373 K to 1473 K, positive holes were the dominant charge carrier in the oxygen-rich atmosphere, whereas the dominant charge carrier was vacancies in the hydrogen-rich atmosphere. These results agree with our previous studies.

In this study, a simple but highly sensitive label-free aptasensor based on a screen-printed electrode (SPE) was developed for detection of Cd²⁺. As crucial biorecognizer, the Cd²⁺ aptamer (issAP08-Cd²⁺) was first screened out using the isothermal titration calorimetric method, which showed that the equilibrium dissociation constant (K_D) of Cd²⁺ binding with issAP08-Cd²⁺ was 2.9 μM. Then, the issAP08-Cd²⁺, which is a single-stranded DNA with 25 nucleotides, was modified with thiol and assembled on gold screen-printed electrode. After that, the electrochemical aptasensor was used for Cd²⁺ detection by dropping Cd²⁺ solution on the SPE. The electrochemical properties were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimal conditions, the change of DPV peak currents density values (Δi) increased linearly with the logarithm of Cd²⁺ concentrations from 0.1 ng/mL to 1000 ng/mL. The regression coefficient was 0.9914 and the limit of detection (LOD) was 0.05 ng/mL (S/N = 3). This outcome supported the conclusion that the electrochemical aptasensor not only showed good sensitivity and selectivity but also obtained satisfactory reproducibility and stability results and performance on applications in real samples. More importantly, the composition of this aptasensor is very simple, and it has promising potential for rapid field detection of Cd²⁺.

A novel graphene-NiO-polyaniline (Gr-NiO-PANI) was prepared by electrolysis, electrodeposition and electropolymerization methods, respectively. The X-ray diffraction (XRD) proved the successful preparation and composition of the Gr-NiO-PANI hybrid. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to further determine the structure and morphology of as-prepared composites. Cyclic voltammetry confirmed that Gr-NiO-PANI composite had excellent detection effect on urea. By comparing the electrochemical behavior of Gr-NiO-PANI with Gr-NiO and Gr-PANI modified electrodes toward urea, the role of NiO in composite and the detection mechanism of urea were explored. A common linear sweep voltammetry technique was used to detect urea. The test results showed that urea exhibited a good response on the Gr-NiO-PANI modified electrode. In the range of 60∼160 μM urea concentration, the response current of the Gr-NiO-PANI modified electrode is proportional to the urea concentration, and the concentration stand curve equation was I(μA) = −0.0886C(μM) + 58.39 (R² = 0.9917). The as-fabricated sensor exhibited high sensitivity (1.266 μA/μM), lower limit of detection (7.35 μM), excellent reproducibility, and so it can provide a simple and cheap method for detection of urea in environmental monitoring, agriculture, medical industry.

An electrochemical sensor for Zn²⁺ ions in aqueous medium has been developed using disposable screen printed electrodes (SPE). Working electrode of the screen printed electrode has been modified using an ionophore (SMS-3) having schiff base moiety. Surface modification and redox behavior of the SMS-3 modified SPE has been compared with unmodified SPE using Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV). Herein, we discovered that modified SPE showed good electrochemical signals and sensitivity toward metal ions. The characteristic cathodic peaks at −0.59 V and 0.55 V of the ionophore was quenched in the presence of Zn²⁺. SMS-3 modified SPE works in the detection range of 0.47 to 5.56 μM with a limit of detection (LOD) 0.92 μM. DFT studies on SMS-3 supported the observations for the modified SPE. Further, sensitivity and selectivity of the electrode were also examined in the presence of various interfering ions and found that these ions did not interfere in the detection of Zn²⁺ ions. The electrodes were applied for the detection of Zn²⁺ in food samples.

In the recent years, the growing number of diphtheria cases (also lethal) has been observed. As the diphtheria disease characterizes with rapid development and highly nonspecific initial symptoms, the fast detection method of pathogenic Corynebacterium strains, especially by the diphtheria toxin, is of particular importance. Herein, we present the studies on the development of an electrochemical immunosensor toward diphtheria toxoid (part of the vaccines inducing an immune response). The monoclonal (from rat ascites) and polyclonal (guinea pigs) antibodies were compared as receptor elements. The influence of different immobilization methods, electrode surface blocking agents or metallic nanoparticles on the biosensor response was examined. The degree of surface modification and further interaction with diphtheria toxoid was verified using cyclic and square – wave voltammetry as well as impedance spectroscopy. The calculated dissociation constant (6.892·10⁻⁵ Lf/mL) for the developed sensing layer confirmed high affinity toward the toxoid. The linear dependence of redox current change versus diphtheria toxoid was recorded within 10⁻⁴ to 10⁻¹ Lf/mL. Moreover, the selectivity studies indicated a distinctly lower biosensor response for thrombin, lysozyme, IgG and Phe-Ala peptide what allowed for detection of diphtheria toxoid in real sample.

In this study, the labyrinth resonator based chemical liquid and transformer oil condition sensor are presented in a microwave frequency range both numerically and experimentally. The transmission coefficient is observed by the magnetic coupling between the transmission line and resonator which also contain a sensing layer. The sensor structure is tested with the ethanol-water mixtures, methanol-water mixtures and different kind of pure chemical fluidics. In addition, the proposed sensor is used for distinguishing the waste and clean transformer oil sensitively. In the chemical liquids sensing study, linear response characteristics of the sensor have been investigated by the resonance frequency shifts for ethanol-water and methanol-water mixtures. The frequency shifts for each 10% steps of ethanol and methanol content have been monitored as about 25 MHz and 15 MHz, respectively. In the transformer oil condition sensing study, non-destructive methods have been used for providing the long term stability of the sensor structure. In addition, the measured response time between the signal applied from the input port and observation of the transmitted signal from the output port is around 5ns. This value is consistent with the period of the applied signal and the length of the receiver/transmitter cables and the sensor circuit.

The present study was designed to synthesize lanthanum doped feathers-type ZnO nano-flower (feathers-type La³⁺-ZnO nano-flower), that are specified via Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). To simultaneously determine codeine and diclofenac using feather-type La³⁺-ZnO nano-flower modified carbon paste electrode (La³⁺-ZnO/CPE), an original cost-efficient and simple methodology is presented. Evidently, La³⁺-ZnO/CPE proved to be a prospective, stable, sensitive and chemically reliable electrochemical sensor to determine diclofenac and codeine simultaneously with no intervention or overlapping of voltammetric peaks or signals. Codeine electro-analytical sensing was examined via La³⁺-ZnO/CPE across an extensive concentration range at a relatively low detection limit of 0.01 μM, (3S/N). La³⁺-ZnO/CPE of nanoscale feathers-type La³⁺-ZnO structure displays favorable practicality in analytical terms to accurately and simultaneously determine diclofenac and codeine within real specimens with exceptional recoveries. The outcomes prove exceptional La³⁺-ZnO/CPE performance in regard to facile, reliability and sensing capabilities which may favorably decrease the relevant processing expenses for routine analysis and scalable production.

Guanine (G) and adenine (A) are two important components of nucleic acid and some small molecules in an organism. In this paper, we developed a new and convenient biosensor for the simultaneous determination of G and A based on overoxidized polypyrrole/multi- walled carbon nanotube and molybdenum disulfide modified glassy carbon electrode (PPyox/ MWNTs-MoS₂/GCE). The composite material exhibited remarkable electro-catalytic properties toward the oxidation of G and A due to its large surface area and fast electron transfer. The oxidation peak positions of G and A were at 0.73 V and 1.03 V, respectively, which allowed simultaneous detection of the two substances in coexistence solution. The designed biosensor exhibited linear responses to G and A both in the ranges 5–30 μM and 30–120 μM, with detection limits (S/N = 3) of 1.6 μM (G) and 1.7 μM (A), respectively. Moreover, interferences from some coexisting electro-active species including inorganic ions, glucose, glycine and citric acid were nearly negligible. Further, the sensing strategy was successfully used for the detection of G and A in real samples with satisfactory results, indicating a potential application for the simultaneous electrochemical detection of G and A.

Graphene has generated widely interest in biosensor study because it had a large surface area, excellent electrical and thermal conductivity, high mechanical strength and other unique physical and chemical properties. In this paper, graphene was reviewed from three aspects. Firstly, several common fabrication methods and characteristics of graphene were introduced. Secondly, applications of the nanosized graphene (NG) and nanosized graphene oxide (NGO) in biosensor and medical imaging were discussed. The NG and NGO had the characteristics of photoluminescence. Based on the fluorescence quenching nature of the graphene surface, the targeting molecules could be confirmed by detecting the fluorescent substance. In addition, the graphene oxide (GO) had a promising prospect in the field of surface-enhanced Raman imaging. In the field of electrochemistry, graphene and its derivatives could be modified on the surface to couple with ligands and antigens and were able to detect specific biomolecules, such as glucose, DNA, proteins and etc. Thirdly, this paper introduced graphene applications in medical treatment. Due to the inherent high near-infrared (NIR) absorbance, graphene materials were widely used in the treatment of in vivo cancer photothermal therapy. The combination of the graphene, anticancer drugs, and specific antigens was highly efficient for drug delivery. This paper summarized the achievements of graphene materials in the medical diagnostics, the presents challenges, and the future prospect.

Amorphous nickel boride (NB) nanoparticles are facilely synthesized by one-step chemical precipitation and for the first time applied for glucose oxidation. Benefiting from the merits of uniform nano-morphology and highly-dispersed Ni, the achieved NB-modified electrode exhibits excellent electrochemical performances with high sensitivity for non-enzyme glucose detection.

Point-of-care testing (POCT) of neurotransmitters, such as dopamine (DA) and 5-hydroxytryptamine (5-HT), can be used for early diagnosis of neurological diseases. Among various POCT platforms, electrochemical method-based platforms have attracted increasing interest owning to their high detection sensitivity and specificity as well as fast response time. In this work, we developed a portable electrochemical POCT platform for detection of neurotransmitters, which is based on integration of a three-dimensional (3D) gold nanoparticles/carbon nanotubes (AuNPs/CNTs) sponge synthesized by a simple in-situ growth and eco-friendly ice-templating method modified screen-printed electrode with a miniaturized USB electrochemical analyzer. We demonstrated the good performance of the portable electrochemical platform for detection of two typical neurotransmitters, i.e., DA and 5-HT, with detection sensitivities of 1.02 μA μM⁻¹ cm⁻² and 0.55 μA μM⁻¹ cm⁻², and detection limits of 0.06 μM and 0.30 μM for DA and 5-HT, respectively. We further verified the feasibility and practicability of the platform by simultaneous detection of DA and 5-HT in spiked saliva. The developed portable electrochemical platform provides a simple and user-friendly way for early diagnosis of neurological diseases in the future, especially at point of care.

The electrochemical determination of ultra-low concentrations of silver requires reliable, reproducible measurements using sensitive analytical techniques. To date, the electrochemical determination of silver in biological buffers and pH neutral media has not been successful in terms of reproducibility. In this work, we report on the determination of ultra-low concentrations of silver in chloride-free phosphate buffer solution (PB, pH 7.4). Detection was conducted at gold and platinum micro and nanoelectrodes using anodic stripping voltammetry (ASV). The micro and nanoelectrodes were fabricated using a Sutter P-2000 laser puller, with physical and electrochemical characterization revealing flat disk-shaped working surfaces of 10–15 μm (microelectrode) and 10–100 nm (nanoelectrodes) in radius. These dimensions were calculated from steady-state limiting currents and confirmed using FE-SEM. The laser pulled electrodes exhibit excellent electrochemical activity when characterized using ferrocene, without the addition of supporting electrolyte, and reproducible stripping voltammetric profiles for the determination of silver, with a LoD of 1.3 pM (1.8%) were obtained in 0.1 M chloride-free phosphate at platinum nanoelectrode. Determination of ultra-low concentrations of silver in chloride-free PB provides the scope to explore the mechanism of action of bioinorganic silver-based anti-bacterial, anti-fungal and anti-cancer drugs in cell media for in vitro and, potentially, in vivo analysis.

We studied a dissolved oxygen sensor in aqueous media based on a mesoporous Pt microelectrode with the aim of obtaining a large sensor output. Mesoporous Pt structures were fabricated via Pt thin film deposition on a skeleton of nanoporous gold. The dissolved oxygen was measured via adoptive stripping voltammetry, i.e., the dissolved oxygen was adsorped on the surface of the mesostructured platinum microelectrode over a certain period. Accumulated oxygen on the surface of the mesostructures was reduced through voltammetry with a large current. This led to a linear increase in the reduction current as a function of the active surface area of the Pt mesostructures, indicating that the entire surface area of the mesostructures is utilized to adsorb and reduce oxygen in the given experimental condition. The proposed method could obtain a lager sensor output compared with sensors under diffusion-controlled reactions and better fits for oxygen sensors in micro total analysis systems.

Three dihydroxybenzene isomers, hydroquinone (HQ), catechol (CC) and resorcinol (RS), were determined simultaneously by an ultrasensitive electrochemical sensor based on a glassy carbon electrode modified by multiwalled carbon nanotube@reduced graphene oxide nanoribbon (MWCNT@rGONR) composite. The material was synthesized via hydrothermal method and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). We used cyclic voltammetry (CV) to study the electrochemical performance of the three isomers and differential pulse voltammetry (DPV) to optimize the experimental parameters. Based on the optimal experimental condition, our electrochemical sensor displayed a good linear relationship with the concentration range of 15 to 921 μM, 15 to 1101 μM, and 15 to 1301 μM and detection limit of 3.89 μM, 1.73 μM and 5.77 μM for HQ, CC and RS respectively. The electrochemical sensor based on MWCNT@GONR composite showed outstanding ability of reproducibility, stability and anti-interference. In addition, this sensor was also used successfully for simultaneous determination of HQ, CC and RS in real samples with satisfactory result.

In this research, a mechanistic approach was used to investigate the effect of molybdate ion on the critical pitting temperature (CPT) of 2205 duplex stainless steel. Firstly, the CPT of 2205 DSS was measured using potentiodynamic and potentiostatic polarization. It was found that with addition of 0.0005, 0.005 and 0.05 M Na₂MoO₄ to 0.5 M NaCl solution, the CPT increases approximately 4, 9, and 14°C, respectively. Using the lead-in pencil electrode technique, the mechanism by which molybdate ion influences the CPT was interpreted using the CPT model proposed by Salinas-Bravo and Newman. The results showed that molybdate has a negligible effect on the pit solution chemistry, resulting in a slight change in the diffusion-limited current density. However, it reduces the rate of alloy dissolution within the simulated pit solution, which was found as a reduced maximum current density.

We report on a study of morphology evolution following de-lithiation of Li-Pb alloys, produced by the electrochemical lithiation of Pb particulate and sheet electrodes. Electrochemical titration and time of flight measurements were performed in order to determine the intrinsic diffusivity of Li, , as a function of alloy composition, which ranged from 10⁻¹²–10⁻¹⁰ cm²s⁻¹. Morphology evolution was studied under conditions of galvanostatic and potentiostatic dealloying. For the particulate electrodes, we observed dealloyed morphologies corresponding to Kirkendall voids, negative dendrites, void nodules and conventional bicontinuous nanoporous structures. In the case of Pb sheets, similar dealloyed morphologies were obtained under galvanostatic dealloying conditions, however, in the case of potentiostatic dealloying, we did not observe the formation of large volume bicontinuous nanoporous structures. For Pb sheets lithiated to a composition corresponding to the Li₈Pb₃ phase and galvanostatically dealloyed at current densities ∼1 mAcm⁻², voltage oscillations were observed with periods of 70–90 s and amplitudes ranging from 20–130 mV. Current oscillations were also observed for potentiostatic dealloying at 1 V vs Li⁺/Li. The possible mechanism of these oscillations is discussed and attributed to a salt film precipitation and lift-off process.

In Part II of this series, a framework for pit stability established, and it was expanded in Part III to describe salt film formation in pits. It was shown that a salt film was not required for pit stabilization; it is just a consequence of a pit achieving diffusion-controlled growth. A salt film can form on the surface of both metastable and stable pits when the maximum pit dissolution current density, i_diss,max, exceeds the diffusion-limited current density, i_lim. Based on this clarifying framework, this paper shows mathematically that the main function of a salt film is to adjust the actual potential at pit surface by regulating its thickness, thus to restrict the anodic dissolution rate of pit surface metal at the value of diffusion-limited current density. As a result, the film thickness will respond to any changes in the applied potential, temperature, pit depth, ohmic potential drop in the solution and perforation radius of the pit cover. Additionally, the pit stability criteria that have been discussed previously in the literature are reinterpreted using the new framework, and they are unified by the critical temperatures, potentials and pit depths for pit stabilization and salt film formation proposed in Part III.

Silicon (Si) based implantable components are widely used to restore functionalities in the human body. However, there have been reported instances of Si corroding after only a few years of implantation. A key parameter often overlooked when assessing Si stability in-vitro, is the added constricting geometries introduced through in-vivo implantation. The influence of crevices and confined solutions on the stability of Si is presented in this study, considering two simulated physiological solutions: 0.01 M phosphate buffered saline (PBS) and HyClone Wear Test Fluid (WTF). It was found that Si is highly vulnerable to corrosion in confined/crevice conditions. High pitting corrosion susceptibility is found in a crevice, whereas a dissolution rate of ca. 3.6 nm/h at body temperature occurred due to local alkalization within a confined cathodic area. The corrosion rates could be increased by elevating the temperature and yielded linear Arrhenius relations, with activation energies of 106 KJ/mol in 0.01 M PBS and 109 KJ/mol in HyClone WTF, corresponding to a phosphorous-silicon interaction mechanism. Phosphorous species favored corrosion and contributed to enhanced Si dissolution, while chlorides were not so influential, and applied anodic potential induced pseudo-passivation. These results highlight the importance geometrical configurations can have on a material's surface stability.

The inhibitory effects of Mg²⁺ and Zn²⁺ on the cathodic kinetics of AA7050-T7451 were investigated by both electrochemical techniques and surface characterization tools. This study focused on the effects of Zn²⁺/Mg²⁺ concentration and immersion time. It has been found that in the cathodic potential regime where the oxygen reduction reaction (ORR) was dominant, Mg(OH)₂ and NaZn₄(SO₄)(OH)₆Cl⋅6H₂O were precipitated on Cu-bearing intermetallic compounds (IMCs) embedded in AA7050-T7451 in Mg²⁺-and Zn²⁺-containing solutions, respectively. Both formed a barrier to oxygen diffusion, thus lowering the cathodic limiting current density. The decrease in cathodic limiting current density pertinent to ORR was proportional to Mg²⁺/Zn²⁺ concentration. At short times, both ions decreased the open circuit corrosion rate, with the inhibition increasing with increased cation concentration. Better inhibition was provided by Zn²⁺ than by Mg²⁺ at the same ion concentration. The corrosion inhibitive effect of Mg²⁺ was inferior to Zn²⁺ during the first 120hrs, but was inferred to be superior to Zn²⁺ for an immersion exposure period longer than 120hrs.

The chemical resistance of the ZrN powder to molten LiCl with additions of PbCl₂, KCl, Li₂O, LiOH, and H₂O at 650°С have been thermodynamically evaluated and experimentally verified. Using complex physical-chemical methods it has been demonstrated that ZrN exhibits a high resistance to the LiCl-PbCl₂ melts. After long-term exposure of the ZrN powder in these melts the PbCl₂ concentration was not changed and the ZrCl₄ content did not exceed 0.002 wt% in the melt and 0.23 wt% in the sublimates. An increase in temperature or molar ratio of PbCl₂/ZrN, as well as appearance of the KCl modifying component insignificantly reduces the ZrN resistance to molten LiCl-PbCl₂. According to the SEM analysis, a structure of the ZrN powder becomes less dense after the exposure in LiCl-PbCl₂. Almost complete oxidation of the ZrN powder was found after long-term exposure in the LiCl-PbCl₂ melts with Li₂O and LiOH additions, and only partial oxidation was observed in melts with H₂O addition. Nevertheless, a high resistance of the ZrN powder to the LiCl-Li₂O melt was determined.

The effect of Al³⁺ on the cathodic kinetics of Al alloys as well as Pt and SS316L has been investigated by a number of electrochemical techniques. It has been observed that the addition of Al³⁺ into NaCl solution can significantly increase the diffusion limited cathodic kinetics of Al alloys, and this increase is proportional to the [Al³⁺]. The same phenomenon was also observed on Pt and SS316L, which indicates that this enhancement in cathodic kinetics is not related the surface structure of Al alloy, and it is the HER diffusion-limited kinetics that are increased rather than ORR kinetics as a result. Based on electrochemical studies on Pt, it is proposed that although the addition of Al³⁺ can lead to the precipitation of an oxide/hydroxide film on Pt there is a greatly enhanced proton diffusivity which overwhelms the barrier effect of the precipitate film, leading to substantially increased cathodic kinetics. The results are interpreted in terms of an extension of the Grotthuss Theory in which Al³⁺ can facilitate transport of the proton.

The corrosion behavior of Inconel 625 in molten LiCl solutions maintained at 650°C and containing various quantities of Li₂O and metallic Li was studied for possible application in the electroreduction of used oxide-based nuclear fuel. This study focusses on the morphological and elemental changes on the surface of the samples with an emphasis on cross-sectional analyses conducted using focused ion beam microscopy. In the absence of metallic Li, a stable oxide film is formed that limits the corrosion of the base material to 0.07mm/year. However, in the presence of metallic Li, the formation of this film is impeded, resulting in dealloying of the base material and the formation of a highly porous microstructure composed primarily of Ni.

Fluorine doped tin oxide coated glass slides were evaluated for their chemical stability in different pH solutions at room temperature by carrying out potentiodynamic polarization and cyclic voltammetry (CV). The FTO was more stable in 0.1 M HNO₃ and 0.1 M NaCl solutions under both anodic and cathodic polarization conditions. Cathodic polarization in 0.1 M HCl solution resulted in a reduction of SnO₂ to lower valent species. The semiconductivity of FTO, which was n-type at low anodic potentials, was p-type at high anodic potentials possibly due to the formation of a SnO-type surface layer by the removal of lattice oxygen during the oxygen evolution reaction. Cyclic stability of the FTO was evaluated by conducting CV between −2.0 and vbn 2.0 V_Ag/AgCl at 1 V/s. Intergranular corrosion was observed and the stability was completely lost after 215 cycles in the 0.1 M HCl solution. The stability of FTO was better in the 0.1 M NaOH solution, wherein the electro-catalytic activity degraded after 500 cycles, the electrical connectivity was maintained even after 4500 cycles.

The inhibition of AA2024-T3 corrosion by the synergistic combination of 3-Amino-1,2,4-triazole-5-thiol (ATAT) and cerium chloride in sodium chloride solution is assessed. Analysis of electrochemical impedance spectroscopy results show improved corrosion inhibition for the inhibitor combination by increased charge transfer resistance. Scanning vibrating electrode technique was utilized for corrosion current monitoring and quantification. X-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry were utilized to characterize the ATAT/Ce based film and to explain the mechanism of inhibition. The obtained results demonstrate a good potential of the inhibitor combination for improved suppression of corrosion processes.

Sulfide-induced corrosion is expected to be the dominating long-term corrosion process for copper containers in technical concepts for deep geological disposal of spent nuclear fuel (SNF), adapted in several waste management programs around the world. The present study investigates the atomic-scale mechanism of the cathode side of the corrosion reaction using Density Functional Theory (DFT) calculations. Despite the central role of the reaction, neither the site of reaction nor the active species has been previously established. Here we compare the cathodic reaction leading to H₂-evolution on pure copper and on chalcocite (Cu₂S) surfaces. The considered H-donors are OH⁻/H₂O and HS⁻/H₂S which are all available at the neutral to alkaline conditions anticipated at the SNF disposal sites. Assuming Volmer-Tafel-Heyrovsky kinetics, we find that the cathodic reactions are many orders of magnitude faster on copper compared to copper sulfide. Although we find that HS⁻/H₂S have lower reaction barriers than H₂O, our kinetic analysis suggest that H₂O is expected to be the main H-source for the cathodic reaction under SNF repository conditions as results of the low sulfide concentrations (≲ 10 μM) expected in SNF repositories in Sweden, Finland and Canada.

Ni-W alloy coatings on mild steel substrate with various crystalline structures were prepared using pulse and pulse reverse electrodeposition method for corrosion protection application. The co-deposition behavior of tungsten and basic electrochemical information of electrolytes were confirmed through cyclic voltammetry studies. The crystalline nature, alloy phase and it is crystal (cubic and tetragonal) phase transformations were confirmed using X-ray diffractions. The corrosion resistance performances of the deposits were studied using Tafel polarization and electrochemical impedance studies. Correlation between the crystal structures and its corrosion resistance performance were explored and tetragonal Ni-W alloy film having better corrosion resistance than cubic Ni-W alloy film. The mixed phase of tetragonal dominated cubic structures in the alloy matrix has the superior corrosion resistance performance. This study confirms the Ni-W alloy films have good corrosion protection and this can be tuned with the modification of crystal structure using various deposition conditions.

In this work, molybdenum disulfide nanosheets were electrophoretically co-deposited with PEEK 708 microparticles to fabricate composite coatings on Ti-6Al-4V titanium alloy substrates. Different dispersion media, pure ethanol and ethanol with the addition of cationic chitosan polyelectrolyte have been studied. The co-deposition mechanisms were indicated based on zeta potential measurements and investigation of the interaction between particles in the suspension using electron microscopy. The composite coatings deposited from the suspension containing a low amount of MoS₂ stabilized by chitosan were homogeneous. The polymer morphology changed as a result of heat-treatment from granular in the as-deposited coating into a dense, continuous matrix in the heat treated coating. The separate MoS₂ nanosheets and their packages were relatively homogeneously distributed and formed arrays that were mainly parallel to the coating surface. The coatings exhibited an amorphous structure regardless of the applied cooling rate after heating. The amorphization of the coating, slowly cooled after heating above the melting point, is due to the partial diffusion of sulfur from MoS₂ to PEEK 708 and its sulfonation. The obtained results provide new knowledge regarding the co-deposition mechanisms of MoS₂ and PEEK in the presence of chitosan and polymer sulfonating at elevated temperatures.

The reaction mechanism of electrolytic reduction of SiO₂ at a liquid Zn cathode in molten CaCl₂ was investigated with the aim of establishing a new production process of solar-grade Si. Three types of Zn/SiO₂ contacting electrodes were prepared depending on the objectives. Cyclic voltammetry suggested two reduction mechanisms of SiO₂ at a Zn electrode. One is a direct electrolytic reduction that proceeds at potentials more negative than 1.55 V vs. Ca²⁺/Ca. The other is an indirect reduction by liquid Ca–Zn alloy at potentials more negative than 0.85 V. The both reduction mechanisms were confirmed to proceed at 0.60 V by electrolysis and immersion experiments. Impurity analysis by ICP-AES was conducted for the Si prepared by potentiostatic electrolysis at 0.60 V, and confirmed that the concentrations of the metal elements and P were lower than the target levels for primary Si before directional solidification process.

Hexagonal phase β-NaYF₄ thin films doped with Yb³⁺ and Er³⁺ have been made by electrodepositing onto β-NaGdF₄ underlayer using Y-EDTA, Yb-EDTA, Er-EDTA and NaF as precursors in an aqueous solution at low temperature. The underlayer substrates have large effects on their crystal phase. The hexagonal phase β-NaYF₄:Yb/Er can even be obtained at 30°C if the films are electrodeposited onto electrodeposited hexagonal phase β-NaGdF₄ underlayer. Cubic-phase (α-phase) NaYF₄:Yb/Er films are formed only if the films are electrodeposited onto tin doped indium oxide (ITO) glass. The formation of hexagonal phase β-NaYF₄:Yb/Er might be due to the epitaxial stabilization effect since β-NaYF₄:Yb/Er and β-NaGdF₄ crystals have same crystal structure and very small lattice parameter difference (less than 1%). XRD, SEM and HRTEM were used to characterize the structures of electrodeposited films. The hexagonal phase β-NaYF₄:Yb/Er films exhibited much higher intense visible light emissions excited by a 980 nm laser than its cubic phase.

NiFe nanocrystalline films were formed onto Au film via pulsed electrolyte deposition with variable time of relaxation between the sequential pulses. Analysis of anomalous non-liner changes in the NiFe film structure showed the implementation of three mechanisms, resulting in "layer-by-layer", "layer-plus-island", or "island" growth. The change of the interpulse relaxation time provides the possibility to realize all three different mechanisms. The grown NiFe films may have different morphology. The ultrathin NiFe films have nanosized grains and exhibit high uniformity of structure, the films may be also combined of less that 10 nm nanoscale grains and their conglomerates, typically, about 50 nm in size, and, additionally, the film structure, consisting of isolated magnetic islands can be realized. The phenomenological explanation of the different mechanisms was obtained using atomic-force-microscopy (AFM) approach. It has been demonstrated that the growth mechanism can be controlled by nanocrystallites conglomeration, which is accelerated with increasing the relaxation time. The origin of the conglomeration process is mainly associated with high surface energy of nanosized grains.

This paper shows the preparation of a gold suspension containing carbon nanocapsules and their co-deposition from the colloidal galvanic bath on a nickel electrode to obtain gold/nanocapsules composite coatings. The incorporation of the nanocapsules was confirmed by surface analysis and confocal microscopy. The influence of suspension preparation, nanocapsule concentration and stirring during the co-deposition was analyzed and showed that capsules strongly adhere on the surface and are coated by the gold matrix forming rounded clusters. The efficiency of the galvanostatic deposition increases in presence of capsules due to the increase in the active area and the metal growth on the carbon surfaces. The results establish a theoretical background for the electrochemical co-deposition of carbon nanocapsules acting as carriers for the further development of smart coatings.

To support the proposal for separating uranium from used fuel salt of Molten Salt Reactor (MSR), the electrochemical behavior of UO₂²⁺ in the carrier salt of MSR (LiF-BeF₂, FLiBe) was investigated in this work. Cyclic voltammetry and square wave voltammetry measurements showed that the reduction of UO₂²⁺ in UO₂F₂-FLiBe melt with addition of KF exhibited one step with two exchanged electrons: UO₂²⁺ +2e⁻ →UO₂, with reduction peak of 1.93 V (vs. Be²⁺/Be). By potentiostatic electrolysis, the product of octahedral UO₂ single crystals with micron size was obtained.

The suitability of N-ethylpyridinium bromide as a potential electrolyte additive for zinc electrodeposition in aqueous solution has been investigated by a combination of cyclic voltammetry, bulk electrolysis, scanning electron microscopy, synthesis and NMR spectroscopy. The current magnitudes of the Zn/Zn(II) redox reaction observed at the electrode decreased dramatically after a single deposition/stripping cycle in the presence of N-ethylpyridinium bromide at switching potentials more negative than −1.30 V vs Ag/AgCl. This is attributed to the reduction of the N-ethylpyridinium cation to form a pyridyl radical that subsequently and rapidly dimerizes. The proposed dimer was synthesized and shown to have a low solubility in aqueous solutions, consistent with a passivation of the electrode surface by precipitation and inhibition of redox behavior. Based on this understanding for the pyridinium cation reduction, alternative pyridinium-based additives have been examined in order to determine their influence on zinc electrodeposition.

In this work, the leaching of the active material electrodes of spent alkaline batteries was carried out using a deep eutectic solvent formed by acetylcholine chloride-urea as leaching medium. From the leaching liquors of the cathode or the cathode/anode mix, the electrochemical formation of Mn or Mn-Zn alloy, onto a glassy carbon electrode, was respectively performed by means of cyclic voltammetry and chronoamperometry techniques. The analysis of the potentiostatic current density transients was done using of models that involve the three-dimensional nucleation and diffusion controlled growth of a) bimetallic phases [Díaz-Morales et al. J. Solid. State Electrochem. 17 (2013) 345–351], in the case of the Mn-Zn alloy and b) metallic nuclei, for Mn electrodeposition [Scharifker and Mostany, J. Electroanal. Chem., 177 (1984) 13–23]. From scanning electron microscopy and EDX, it was verified that the nuclei formed were composed of Mn, or the Mn-Zn alloy depending on the leaching liquors used.

Electrolytes for decorative chromium plating based on trivalent chromium salts are known since several decades. As the use of conventional, hexavalent chromium based plating baths is more and more restricted by governmental regulations, these electrolytes gain ground in electroplating industry. However, compared to hexavalent chromium electrolytes, trivalent chromium electrolytes cannot fully meet the requirements with regard to appearance of the electrodeposited chromium, and there is little knowledge about the influencing factors on the shade of color. In this paper, chromium plated from a solution of chromium(III) sulfate was characterized by colorimetry, SEM and AFM and compared to a sample plated from a chromic acid electrolyte in order to reveal correlations between visual appearance and surface morphology. A relation between an increase of grain size and a color shift from blueish to yellowish was observed. Unlike in hexavalent based systems, grain size, roughness and color depend on layer thickness as the grain growth mechanism appears to be different. A model based on the theory of light scattering at rough surfaces is provided that links roughness and reflection behavior of the chromium surface.

In this study, we analyzed the diffusion behavior of additives, such as Cl⁻ and bis–(3–sulfopropyl) disulfide (SPS), during the through-silicon via process with our surface-enhanced Raman spectroscopy (SERS) measurement system equipped with a model structure of a micro via. The via structure, made of poly(dimethyl siloxane) (PDMS), which has a transparent wall, was attached horizontally on the Cu nano-patterned substrate, an array of nanodots with 150-nm diameter and 300-nm pitch. This substrate provides the SERS effect with high uniformity and also works as one of the sidewalls of the via. The simultaneous diffusion of Cl⁻ and SPS into the micro via on the Cu nanodot wall was observed by Raman microspectroscopy. The obtained SERS spectrum clearly indicated the diffusion of these two species. First, Cl⁻ adsorbs on Cu, because it has a larger diffusion coefficient; SPS removes the pre-adsorbed Cl⁻ to dominate the adsorption site of the surface a few minutes later. Pre-adsorbed SPS is sufficiently stable, and is not removed by a highly negative potential (for example, −200 mV vs. Ag/AgCl).

The design of electrolyte systems suitable for room-temperature electrochemical extraction of Li, Mg, Al, Ti, rare earth elements, and other active metals from their salts or oxides has long been a scientific challenge. Herein, we report an exceptional organic solvent (1,3-dimethyl-2-imidazolidinone) supported by LiNO₃ with properties superior to those of conventional ionic liquids and show that it is well suited for room-temperature potentiostatic deposition of La coatings from LaCl₃ on high-purity Al substrates. Thus, this work paves the way to cost-effective La extraction and presents an innovative approach to the selection of electrolyte systems used for electrodeposition of active metals.

Cu and CuPb were electrodeposited from the mixture of water and a protic amide-type ionic liquid (IL), the protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]), in which CuO and PbO were dissolved. The electrodeposited Cu electrode showed electrocatalytic activity toward glucose oxidation in alkaline conditions, and the activity was significantly enhanced once Pb was doped. Activity enhancement might result from the changes of the surface morphologies and the electronic states of Cu, which were concluded according to the SEM observations and XPS analyses.

In this work, we demonstrate electrochemical methods for determination of porosity and surface area of thin films of interconnected nickel nanowires. While the standard porosimetry and gas adsorption methods lack sensitivity for characterization of thin metallic films, the electrochemical methods employing coulometry, cyclic voltammetry and electrochemical impedance spectroscopy can be applied to accurately determine textural properties of micron- and sub-micron thick nanostructured materials. Additionally, in this work we evaluated accuracy and precision of five electrochemical signals recorded during cyclic voltammetry and electrochemical impedance spectroscopy, which are commonly used for determination of electrochemical surface area (A_ECSA) of various nickel electrodes. By verifying the data with two independent surface characterization techniques, we found that the analysis based on surface-limited oxidation of nickel and on capacitive charging of nickel surface during hydrogen evolution reaction give the best accuracy and smallest errors. We also show that experimental conditions play a crucial role in the accurate determination of A_ECSA of nickel nanomaterials. If the influence of experimental conditions is not corrected for, the electrochemical surface area can differ by over 250% compared to the surface area determined with other methods.

Lithium isotope fractionation, based on the difference of the diffusion coefficients, migration mobility, as well as the electrochemical isotope effect, can be achieved in the appropriate solvents. The Propylene Carbonate-Polyethylene Oxide gel electrolyte was utilized to separate Li isotopes by eliminating the fluid flow mixing and part of the solvation shell around Li ions. A higher Li isotope fractionation (△⁷Li = −4.53‰) was achieved with the effects of both diffusion and electrochemical migration in a long 10-cm cell test. Also, a short 2-cm cell gel electrolyte short duration test yielded a very high separation factor of 1.033, which is a very promising separation factor for Li isotope separation. Similarly, the electrochemical intercalation test into the graphite plate electrode associated with the diffusion and migration assisted separation shows a separation factor of 1.033. Influence of the electrochemical cell length was studied with an electrochemical model, and results show that an appropriate cell length needs to be determined by considering both the separation time and the separation factor.

Control of the dissolved oxygen concentration is crucial for the use of liquid lead bismuth eutectic (LBE) as a coolant of advanced nuclear reactors. An electrochemical oxygen pumping (EOP) system was applied to a non-isothermal liquid LBE loop in order to evaluate its capability to control oxygen in 700 liters of flowing LBE. Oxygen pumps were fabricated using one end closed tube of yttria partially stabilized zirconia (YPSZ) as the solid electrolyte and LSCF (lanthanum strontium cobalt ferrite) as electrode. The oxygen transfer through the oxygen pump was regulated by controlling the applied electric current using a PID controller with feedback from a potentiometric oxygen sensor. The oxygen was added to or removed from the LBE by oxygen pumps depending on target oxygen concentration and a process value given by the oxygen sensor. At low oxygen concentrations, oxygen removal rates were limited by oxygen mass transfer. This limitation could be overcome by operating the pumps above the decomposition potential of zirconia.

Cl₂/Cl⁻ reference system was established with quartz cell where Cl₂ gas was trapped on a glassy carbon electrode surface allowing the thermodynamic equilibrium between Cl₂ and Cl⁻ ions. Based on the Cl₂/Cl⁻ reference, the equilibrium potential of Ag/AgCl reference electrode was evaluated at concentrations ranging from 0.00039 mole fraction AgCl to 1.0 mole fraction AgCl and temperatures from 723 K to 823 K. The measured values ranged from −0.877 V to −1.361 V and followed linear correlations against temperature and concentration. However, pure AgCl showed slight upward in comparison to other observed linear trends. Compared to the previously published data sets, this study provides a full spectrum of data yielding better understandings on Ag/AgCl reference, applicable for different experimental conditions. In addition, the activity coefficients of AgCl in LiCl-KCl salt were calculated using ideal Gibbs free energy at supercooled liquid standard state. The activity coefficients range from 0.0012 to 1.19, which did not conform to a linear relationship to AgCl concentration.

Wire electrochemical micro machining (WEMM) using ultra-short pulses has been recognized as a flexible and effective tool for producing planar contour micro-features. However, high-efficiency mass transport in the extremely narrow machining gap (several micrometers or even smaller) is still a great challenge. Here, a method of WEMM assisted with coupling axial and intermittent feed-direction vibrations is proposed. The mechanism of the mass transport in the machining gap using this method was theoretically analyzed with the results indicating that the proposed method was very beneficial for improving the mass transport rate in the machining gap, owing to the high flow velocity in both the feeding and axial directions. A series of comparative experiments with different vibration styles were performed, the results of which were in accord with those of the theoretical analysis. Then, the effect of wire feed length, traveling speed, and amplitude for the intermittent feed-direction vibration to the machining efficiency and quality was investigated. Finally, under one group of optimal machining conditions, a multi-slit micro-structure with small standard deviation (about 0.53 μm) of slit width (about 13.8 μm) and good surface roughness (about Ra = 0.042 μm) was successfully fabricated using a wire electrode with the diameter of 10 μm.

Plasma electrolysis, where a solid electrode in an electrolytic cell is replaced by a plasma (or gas discharge), differs from conventional electrolysis by not being dictated by the surface characteristics of an electrode, but by the chemical species injected into the solution from the plasma. Reduction in a plasma cathode configuration occurs mostly by plasma-injected solvated electrons (e⁻_aq), which may engage in side reactions, such as the second order recombination of e⁻_aq, that ultimately reduce the faradaic efficiency for the production of a desired product. In this work, we show that the depletion of reactants at the plasma-liquid interface due to insufficient transport can reduce the predicted faradaic efficiency for a plasma cathode at low concentrations. Measurements of the faradaic efficiency using the dissociative electron attachment to chloroacetate and the ferri/ferrocyanide redox couple confirm this behavior. The effect of other mechanisms on the faradaic efficiency, such as competing oxidation reactions with the hydroxyl radical, are also evaluated and found to be far less significant. Unlike conventional electrolysis, stirring the solution does not increase the faradaic efficiency, but increasing the species concentration does.

Many techniques used for N₂O abatement involve high temperature catalytic removal with the synthesis of relatively non-valuable products. In the present attempt, N₂O degradation was achieved at ambient temperature using different electron mediators during electroscrubbing to form a high value product, NH₃. A combination of mediator precursors, such as Fe(III)[Ni(II)(CN)₄]¹⁺, Fe(III)[Co(II)(CN)₅], and [Ni(II)(CN)₄]²⁻•[Co(II)(CN)₅]¹⁻, were added to a 10 M KOH solution to generate the electron mediators. The oxidation/reduction potential (ORP) of the electrolyzed solutions of each complex and the UV-visible spectra confirmed the formation of Fe(II)[Ni(II)(CN)₄], Fe(II)[Co(II)(CN)₅]¹⁻, and [Ni(I)(CN)₄]³⁻•[Co(II)(CN)₅]³⁻ at the cathodic half-cell. N₂O degradation was confirmed to occur via a mediated electrochemical reduction (MER) process from the change in reduction efficiency from 4% to 2% (Fe(II)-Ni) and 15% to 12.5% (Ni(I)-Co(II)). Online FTIR gas analysis confirmed that NH₃ formed from the degradation of N₂O. Although the reduction efficiency was lower for Fe(III)[Ni(II)(CN)₄]¹⁺, a high NH₃ concentration formed (4.39 mg/hr.) when it was used as an electron mediator. The presence of the [Co(II)(CN)₅]³⁻ complex in the mixed complex reduced the level of NH₃ formation. The developed method can degrade N₂O to NH₃ efficiently at ambient temperature.

The electrochemical degradation of tetracycline antibiotics (TCs), such as tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC), was investigated by using SnO₂-Sb₂O₃ and PbO₂ modified Ti electrode (Ti/SnO₂-Sb₂O₃/PbO₂ anode). The modified electrode was prepared with a SnO₂-Sb₂O₃ interlayer and a PbO₂ active layer on the surface of Ti sheet, and characterized by scanning electron microscope, X-ray diffraction and cyclic voltammetry. The effects of supporting electrolyte, current density and the initial concentration of TCs on electrochemical degradation were also examined. For the degradation of 50 mg·L⁻¹ TC, OTC and CTC at 5 mA ⋅ cm⁻², the energy consumption were 39.9, 40.0 and 37.7 kWh⋅mol⁻¹, and the removal efficiencies could reach 79.5%, 82.0% and 90.3% for 2 h, respectively. The degradation processes followed the first-order kinetic model, and the rate constants of TC, OTC and CTC were 0.78, 0.84 and 0.97 h⁻¹, respectively. The possible degradation pathways were proposed through monitoring the degradation products of TCs. The results from bioluminescence inhibition assays suggested the residual biotoxicity after complete TCs degradation, and extra reaction was necessary to reduce biotoxicity. Overall, the electrochemical degradation using Ti/SnO₂-Sb₂O₃/PbO₂ anode has a great potential to remove TCs from wastewater.

The available indicators of catalysts for oxygen reduction reaction (ORR) activity are typically characterized at high potentials (commonly at 0.9 V), whereas fuel cells generally operate at 0.8V∼0.6V in its practical application. In our work, charge-transfer resistance (R_ct) was proposed to evaluate the ORR activity of catalysts for fuel cells at rated voltage. Firstly, the Rct of MEA with Pt/C catalysts was measured in the range of 0.68V∼0.92V. Tafel slopes calculated from R_ct were approximately 80 mV/decade at high potentials, whereas the value increased with the decline of potentials below 0.8 V. It showed that R_ct as the ORR indicator of catalysts has certain rationality preliminarily. Secondly, the R_ct of MEA with Pt_xCo_y/C catalysts was compared with Pt/C catalysts. It was lower than that of Pt/C in the high potential region, indicating that the higher ORR activities than that of Pt/C catalysts in higher potential region. Whereas they tended to be the same in the low potential region, indicating that the same ORR activities in rated potential region. Thirdly, R_ct of MEA with Pt/C catalysts during durability test was monitored. It was interesting that the Rct increased by nearly 125.6% after 900 hours.

A powder metallurgy route is described as a promising route to produce highly active Raney-Ni electrodes. An expanded Ni mesh was used as metallic substrate on the surface of which Raney-Ni phases were produced via a heat-treatment step using Al powder at different loads. The overpotential at −300 mA/cm² as well as the active surface area were determined to evaluate the electrodes. The results reveal that a high Al loading is necessary to achieve a stable electrode and a high activity for the hydrogen evolution reaction.

Enhanced catalysis of ethylene glycol electro-oxidation (EGO) is reported at a ternary CoOx/NiOx/Pt catalyst in which Pt nanoparticles (nano-Pt), nickel oxide nanoflowers (nanoNiOx), and cobalt oxide nanoparticles (nano-CoOx); are respectively electrodeposited onto a glassy carbon (GC) substrate. The electrocatalytic activity of the catalyst toward EGO depends on the catalyst's composition, loading sequence and loading level besides the electrolyte's pH and temperature. A detailed morphological, compositional, and structural inspection for the catalyst is achieved by FE-SEM, energy dispersive X-ray spectroscopy, and X-ray diffraction, respectively. Cyclic voltammetry is employed to ensure the successful electrodeposition of the catalyst's ingredients and to assess its activity. The superiority of the CoOx/NiOx/Pt/GC catalyst over a series of catalysts employing different ingredients and/or deposition sequence is demonstrated. It supports a larger (ca. fourfold) oxidation peak current, and a significant (ca. ‒330 mV) negative shift in the onset potential of EGO together with a much more enhanced long-term stability toward continuous electrolysis when compared to the Pt catalyst. The novelty of this investigation extends to employing the electrochemical impedance spectroscopy (EIS) as a probe that provides important information about the reaction pathway of EGO. Interestingly, the maximum capacitance obtained at the CoOx/NiOx/Pt/GC catalyst (coincides with the EGO peak current) is fivefold higher than that obtained at the Pt/GC catalyst at ‒0.35 V vs. Ag/AgCl. Formic acid and oxalic acid were the major products of EGO, as revealed by high performance liquid chromatography.

This paper reports on the development of a novel approach to investigate the stress and strain distributions at the fiber's scale of PEMFC gas diffusion layers (GDLs). The present method includes stochastic reconstruction and finite element solution procedure. The microstructure of a GDL was randomly generated and meshed, upon which solid mechanics simulations were performed. Stress and strain distributions in three dimensions were obtained by considering dynamic contact, frictional motion and extruding deformation of the fibers. A sensitivity analysis on the present model showed that frictional coefficient between fibers has more influence on the model results than the mechanical properties of the fiber. Our simulation results show that under compression, the fiber's displacement in the through-plane direction is significantly more than the in-plane direction. Fibers intruding into the gas channel were also observed. For the case with 20% compression ratio, the computed stress is mostly below 100 kPa with a maximum in excess of 1,000 kPa. Simulation results, which include stress and displacement distributions under compression, are in qualitative agreement with actual observations in the literature. The present methodology can be extended to most porous electrodes that involve material deformation to allow accurate evaluation of their transport properties and performance.

As an oxygen reduction reaction (ORR) catalyst, the activity in acid medium of nitrogen and sulphur co-doped graphene with carbon defect (_V-N,S-gra) is investigated via density functional theory (DFT), including the activity sites, the reaction pathways as well as free energy diagrams. Based on the spin-polarized calculations, six kinds of O₂ adsorption configurations are found and the reaction sites are all carbon atoms adjacent to the dopants. However, they are physisorption in the neighboring carbon of nitrogen, unlikely to initialize the ORR process. Otherwise, if the adsorption sites are in the adjacent carbon of sulphur, the catalyst activity is associated with the adsorption energy, that is, we find a best ORR pathway with a gentle adsorption (−0.03eV). An energy barrier of 0.82eV is found in this favorable process in which the adsorbed O₂ molecular is prone to be hydrogenated continuously to give rise to H₂O molecular, promising a four-electron pathway. On the other hand, in the O₂ strongly adsorbed configurations, the intermediate ^*OH is not easily to be hydrogenated in the final step. At last, the effect of electrode potential is simulated and for the best reaction pathway all the elemental reactions are downhill until the potential is as large as 0.31eV.

Traditional Ni/YSZ anode SOFCs were modified by Sn, Cu and Ag by an infiltration method to obtain Sn-Ni, Cu-Ni and Ag-Ni alloy anode catalysts on the anode. The obtained maximum power density of Ni/YSZ, Sn-doped Ni/YSZ, Cu-doped Ni/YSZ, and Ag-Ni/YSZ cells fuelled by simulated biogas (14 mL min⁻¹ CH₄, 7mL min⁻¹ CO₂ and 7mL min⁻¹ N₂) at 750°C were 0.101, 0.272, 0.085 and 0.102 W cm⁻² respectively. Stability tests of SOFCs in biogas revealed that the stability of Sn-Ni/YSZ and Ag-Ni/YSZ cells in operation was greatly improved compared to the undoped Ni/YSZ cell. Both Sn-Ni/YSZ and Ag-Ni/YSZ cells stably operated for 48 h, but Ni/YSZ cell ceased operation after 19 h due to carbon deposition. The addition of small amount of Cu did not enhance the anti-coking ability. Other than with the severe carbon deposition on the Ni/YSZ anode surface, no observable fibrous carbon could be identified on the Sn-Ni/YSZ and Ag-Ni/YSZ anode surfaces.

A polyaniline dynamic electrode is prepared on titanium round plate through the galvanostatic polymerization synchronized with protonation and possesses the characteristics of conducting emeraldine salt state, granular surface structure, narrow bandgap energy, visible-light excitation. A photo-driving energy conversion system equipped with the polyaniline dynamic photoanode can degrade organic pollutants (i.e. reactive brilliant red x-3b dye) and concurrently generate hydrogen and electric flow. The hydrogen evolution amounts are 300.2 μmol and 163.5 μmol under ultraviolet light and visible irradiation, respectively. Based on its rapid doping/dedoping property, the polyaniline dynamic electrode is easily regenerated and almost recovered to the initial through re-doping with an acid. This work confirms the feasibility that polyaniline can be used alone as photocatalyst to construct a dynamic electrode, which is equipped in a photo-driving energy conversion system can convert organic pollutants into useful forms of energy (viz. hydrogen and electricity).

Developing bi-functional catalyst is an effective way to improve the kinetics of oxygen electrochemistry and promote the performance of Li-O₂ batteries. In this study, spinel NiCo₂S₄ with urchin-like and yolk-shell morphologies were successfully synthesized and evaluated as cathode catalysts for rechargeable Li-O₂ batteries. The results demonstrate both NiCo₂S₄ materials are catalytically active toward ORR/OER, but the urchin-like NiCo₂S₄ performs better with faster kinetics, higher capacity, lower polarization and longer cycle life. Moreover, cycling performance of the Li-O₂ batteries with urchin-like NiCo₂S₄ is evidently better than the reported data in literatures for the batteries with many other transition metal sulfides.

Factors governing the change of the surface composition and the degradation of transport properties of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) under low concentration sulfur-contained air (0.01 ppm) were examined as functions of water vapor pressure (p(H₂O)) and oxygen partial pressure (p(O₂)). Bulk LSCF samples were heat-treated at 973 K in dry or wet air containing SO₂ and more enhanced SrSO₄ formation/growth was observed under wet compared to dry air. When the p(O₂) was changed from 0.21 to 0.01 bar, the SrSO₄ precipitates became smaller in size and higher in number, indicating that the p(H₂O) and the p(O₂) have different effects on secondary phase formation. Detailed analysis of the surface composition indicates the presence of CoFe₂O₄ in the vicinity of the SrSO₄ particle, suggesting the Sr and Co depletion in the subsurface region. Based on the analysis, the water vapor affects the secondary phase growth due to the possibility of additional reaction pathways that may enhance the growth rate. This behavior is correlated with the logarithmic surface oxygen exchange coefficient, log k^*, that was observed to decrease monotonically within 20 h of annealing time but its degradation was found to be faster under wet air, in accordance with Sr and Co depletion rate.

The Ni-Mn₃O₄ composite coating has been deposited on the surface of steel interconnects by electrophoresis and electrodeposition techniques. The effect of bath temperature and bath pH on the microstructure, thickness and composition of the coating during electrodeposition process is analyzed by XRD, SEM and ICP-OES. Mn₃O₄ particles are uniformly distributed in Ni matrix. The optimum temperature and pH value in the electrodeposition bath are 45°C and 5, respectively. The oxide scale microstructure and electrical property of the samples are characterized after an oxidation of 100 h at 800°C in air. The results demonstrate that the area specific resistance (ASR) of the scale for the coated steel is significantly lower than that for the uncoated steel. The thermally converted (Ni,Mn,Fe)₃O₄/NiO layer serves as an effective obstacle against Cr outward migration.

A physics–based numerical model for fitting local impedance spectra (local impedance model, LIM) of the segmented PEM fuel cell is developed and used to validate our recent model for recovery of local parameters from a single spectrum of the whole cell (cell impedance model, CIM). Shapes of the local parameters along the cathode channel resulting from the two models are compared. Overall, the CIM quite satisfactorily describes the cell local parameters provided that the oxygen transport impedance in the channel is not small as compared to other impedances in the cell.

Cyclic voltammetry and controlled-potential electrolysis have been employed to investigate the reductive intramolecular cyclization of propargyl bromoethers derivatives, catalyzed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane)nickel(I), [Ni(tmc)]⁺, as the catalyst, in N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N_{1 1 1 2(OH)}][NTf₂] and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C₂mim][NTf₂] in the absence and in the presence of water. The results show that the reaction leads to the formation of the expected heterocyclic compounds, in moderate to good yields. These compounds are important intermediates in the synthesis of natural products with possible biological activities.

Microelectrodes are small scale electrodes used for electroanalytical detection which have found applications in a wide variety of research areas including biology, kinetics, instrumental development, and surface modification. In this review, we provide a summary of the theory and experimental parameters used for bioelectrochemistry applications of microelectrodes. We then delve into a review of select bio-analytical applications of microelectrodes from 2013 to 2018 and provide a discussion on future research directions.

Cobalt trioxide is a promising cobalt-based oxygen evolution reaction (OER) electrocatalyst, and its OER performance is limited by its low ratio of Co³⁺ to Co²⁺ ions and the dispersibility of nanoparticles. Here we report a simple method to improve the OER catalytic activity via loading Co₃O₄ nanoparticles onto boron carbon oxynitride (BCNO) nanosheets, which greatly decreases the overpotential (∼80 mV) and improves the stability of the Co₃O₄ nanoparticles. The Co₃O₄/BCNO nanocomposite exhibits a good OER performance with a small Tafel slope of 57.58 mV/dec and a low overpotential of 317 mV (vs RHE at 10 mA/cm²) under alkaline conditions. The high OER performance of the Co₃O₄/BCNO nanocomposite is induced by the larger active surface area and higher ratio of Co³⁺ to Co²⁺ ions as well as the formation of Co-N chemical bonds.

This work proposed a novel and facile strategy for in-situ deposition of silver nanoparticles (AgNPs) on polydopamine nanospheres (PDANSs), and used the as-synthesized nanocomposite (AgNPs/PDANSs) as electrochemical tracer for an ultrasensitive aptasensor of ochratoxin A (OTA). The morphology and composition of PDANSs and AgNPs/PDANSs were characterized by electron microscopies and energy dispersive X-ray spectroscopy, and the results showed that AgNPs uniformly on PDANSs surface. AgNPs/PDANSs were combined with streptavidin (SA) to obtain signal probe for constructing of OTA aptasensor. Sequentially, the thiolated capture DNA (cDNA) was firstly immobilized on the gold electrode (GE) to capture the OTA aptamer, and then SA/AgNPs/PDANSs nanoprobes could bind with the end biotin of the aptamer through biotin-streptavidin biorecognition. The monitoring of the proposed OTA aptasensor was realized by the electrochemical stripping signal of AgNPs on PDANSs, and PDANSs was used for signal amplification. In the presence of OTA, the aptamer was preferentially bonded with OTA because of their high affinity, and resulted in the decrease of signal tags on the aptasensor surface, which reduced the electrochemical response signal of AgNPs. Under optimal experimental conditions, the proposed aptasensor offered a wide linear range from 1.0 × 10⁻⁶ μM to 1.0 × 10⁻² μM and a low detection limit of 0.57 pM (S/N = 3). Meanwhile, This AgNPs/PDANSs-based OTA aptasensor had excellent specificity, stability and reproducibility, and was successfully employed for OTA detection in red wine samples, which showed promising application in electrochemical analysis of other toxic molecules.

In this study, a newfangled molecularly imprinted electrochemical sensor based on nanoporous carbon (NC) was constructed and applied to the sensitive determination of calycosin in complex Chinese medicine samples. Aniline as functional monomer and calycosin as template were used to assemble molecularly imprinted polymer (MIP), which was bonded to the surface of NC modified glassy carbon electrode (GCE) by electropolymerization. After characterization of the successfully prepared MIP/NC composite, the electrochemical performance of the proposed sensor (MIP/NC/GCE) was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. The results proved that the sensor could accelerate electron transfer rate and heighten specific surface area. Under optimized conditions, the proposed sensor was used to detect calycosin, which displayed good reproducibility, stability and selectivity. The method demonstrated a liner range of 4.20 × 10⁻⁷∼1.29 × 10⁻⁴ mol/L with the detection limit of 8.5 × 10⁻⁸ mol/L. Moreover, this study will provide a prospective exploration for the application of electrochemical analysis technology in the active ingredient detection of traditional Chinese medicine.

The voltammetry and chronocoulometry methods were used in the research of kinetics of redox processes occurring on electrodes modified with conductive polymers, derived from the following complexes: (±)-trans- N,N'-bis(salicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn)]), ((±)-trans-N,N'-bis(3,-methylsalicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn(Me))]) and ((±)-trans-N,N'-bis(3,-tert-butylsalicylidene)-1,2-cyclohexanediaminenickel(II) (poly[Ni(salcn(Bu))]). Spectroelectrochemical method and chronopotentiometry were used to determine the mechanisms of redox processes. In poly[Ni(salcn)] and poly[Ni(salcn(Bu))] the ligand is oxidized, whereas in poly[Ni(salcn(Me))] both the ligand and the central ion are oxidized. The processes take place according to the EE mechanism. The poly[Ni(salcn)] and poly[Ni(salcn(Me))] films of thickness obtained as a result of 1–30 electropolymerization cycles, as well as poly[Ni(salcn(Bu))] of thickness obtained as a result of up to 150 cycles were studied. The investigated films of each complex are limited by surface processes, diffusion and surface-diffusion processes, depending on the film thickness. For the films that generate surface-diffusion processes, the boundaries of such processes have been determined. For the diffusion processes, the boundaries of semi-infinite diffusion regime and finite diffusion regime have been defined. On this basis, the cD^1/2 value for anode and cathode processes providing semi-infinite diffusion conditions has been determined as a criterion for selection of the optimal conditions for modification of the electrodes.

Chirality has an important impact in chemical and biological research, since most active substances possess chirality. Usually, the performance and properties of chiral enantiomers exhibit significant differences in terms of biochemical activity, toxicity, transport mechanism and pathways of metabolism. Thus, developing effective method to achieve chiral recognition is of great significance and has always been a hot topic in chemo/biological study. In recent years, the electrochemical technologies, which can offer many advantages over the other conventional methods, have received considerable attention in chiral recognition. In this review, a comprehensive and critical detail of the trends on electrochemical chiral recognition in the last 5 years have been presented. In addition, some critical challenges and prospects in the field of electrochemical chiral recognition are also discussed in the latter part.

Deoxyepinephrine (DXEP) is a catecholamine derivative with pharmaceutical activity to raise blood pressure. Therefore, the control of DXEP in biological samples is very important for human health. The proposed research introduces a fast electro-analytical strategy based on CuFe₂O₄/ionic liquid (1-Hexyl-3-methylimidazolium Bromide (1H3MBr)) nanocomposite modified pate electrode (CuFe₂O₄/1H3MBr/PE) for voltammetric determination of deoxyepinephrine. For this goal, the CuFe₂O₄ as conductive mediator was synthesized using facile sonochemical method and characterized by XRD and FESEM methods. The CuFe₂O₄/1H3MBr/PE exhibited good performance for determination of DXEP in the presence of uric acid (UA) with separated potential ∼170 mV. The CuFe₂O₄/1H3MBr/PE was showed linearly proportional to DXEP and UA concentrations in the wide linear ranges from 0.3−300 μM and 0.7−300 μM with LOD of 0.09 μM and 0.4 μM, respectively. The CuFe₂O₄/1H3MBr/PE was suggested as an excellent platform for determination of DXEP and UA in real samples.

Cyclic voltammetry is one of today's standard electrochemical measurement techniques. What characterizes cyclic voltammetry is that potential is linearly ramped in cycles. In general, in this kind of measurements, the system tends to a stationary state, which is known as limit cycle. The common practice for assessing the voltammogram convergence is to perform a multicycle cyclic voltammetry, and visually compare the sequential cycles in order to see if there are significant changes from one cycle to the following one. The main limitation of visual comparison is its limited accuracy and its dependence on the analyst's subjectivity. In this work, an algorithm for quantitatively assessing the convergence of experimental cyclic voltammograms (CVs) was developed. The algorithm was successfully validated experimentally using two systems: it is able to determine whether the CV converged to its limit cycle, and when it converged. Moreover, the algorithm is able to quantify the measurement noise. The low computational cost of the developed algorithm allows to execute it in real time during the cyclic voltammetry measurement. In this way, it can be used in order to automate the measurement process which would decide, according to predefined convergence criteria, when to stop cycling.

Delafossite CuMnO₂ powder composed of earth-abundant elements was synthesized by a sol-gel process and thoroughly characterized by powder X-ray diffraction, SEM, XPS, FT-IR, and Raman spectroscopy. More importantly, their electrocatalytic performances for oxygen and hydrogen evolution reactions (OER and HER) have been fully investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry with a rotating electrode in 1 M KOH electrolyte versus Ag/AgCl. Based on the measurements from these CuMnO₂-based working electrodes, the specific capacitance, total charge, most accessible charge, electrochemically active surface area, and roughness factor were calculated for the first time. Their stability was also studied for cost-effective and active electrode material. Furthermore, by comparing measurements at 1600 rpm and no rotation of the electrodes in alkaline media, the delafossite CuMnO₂ synthesized in this work showed current densities of 12.3 mA/cm² at 1600 rpm and 11.9 mA/cm² at no rotation for OER and 6.9 mA/cm² and 6.3 mA/cm² for HER. Overall, our study demonstrated that delafossite CuMnO₂ possesses effective bifunctional OER and HER activities.

Due to the superposition of various effects at electrocatalyst/solution interfaces, the Frumkin and Temkin adsorption isotherms of H and D are not readily determined using conventional methods. The phase-shift method is a unique electrochemical impedance spectroscopy technique for studying the linear relationship between the phase shift (90° ≥ −φ ≥ 0°) for the optimum intermediate frequency vs potential (E) behavior and the fractional coverage (0 ≤ θ ≤ 1) for adsorption vs potential (E) behavior. The Frumkin and Temkin adsorption isotherms (θ vs E) of H and D and their isotopic shifts at Pt/0.1 M LiOH (H₂O, D₂O) solution interfaces are determined using the phase-shift method. Over the θ range (i.e., 1 ≥ θ ≥ 0), the kinetic isotope effect (K_H/D) is 3.1 to 3.5 and the standard Gibbs energy (ΔG_θ⁰) of D is 2.8 to 3.1 kJ mol⁻¹ greater than that of H. The bond dissociation energy for Pt−D₂O is greater than that for Pt−H₂O. The rate-determining steps are determined by the recombination step at low θ or E and electrochemical desorption step at high θ or E, sequentially. The isotopic shifts of the Frumkin and Temkin adsorption isotherms of H and D and related electrode kinetic effects are clearly distinguished.

Present study investigates the degradation capability of ruthenium oxide coated titanium (Ti/RuO₂) anode for ofloxacin (OFLX) antibiotic, using electro-oxidation (EO) technique in a continuous reactor. Further, the degradation mechanism and its pathway were explored with intermediate/final OFLX transformation products identification. The EO method was optimized using response surface methodology (RSM). Effect of process parameters such as applied current (I), initial pH of wastewater, elapsed time (t) and retention time (R_T), on % total organic carbon (TOC) removal, %OFLX removal and specific energy consumption (SEC, kWh (g TOC removed)⁻¹) was studied in detail and the EO mechanism was explored. Under optimum conditions, 76.78% OFLX removal and 23.85% TOC removal were achieved with 0.706 kWh (g TOC removed)⁻¹ of SEC. OFLX and TOC removal followed pseudo-first order kinetics with rate constant (k_f) values of 5.3 × 10⁻² and 1.5 × 10⁻² min⁻¹, respectively. UPLC-Q-TOF-MS analysis of samples extracted from reactor at pre-determined time-intervals revealed the presence of seven reaction intermediates formed during continuous EO treatment of OFLX. Subsequently, a plausible degradation pathway of OFLX by EO using Ti/RuO₂ anodes was proposed.