Table of contents

High-nickel, cobalt-free, single-crystal positive electrode materials could provide the ultimate intersection of high-specific capacity, low cost, and long-lifetime in lithium-ion batteries. In this work, the synthesis of LiNiO₂, LiNi_0.975Mg_0.025O₂, and LiNi_0.95Al_0.05O₂ is studied by dynamic XRD during heating, in order to guide improvements in synthesis procedures. A comparison of Li₂CO₃ and LiOH·H₂O lithium sources shows that either can be used to prepare these materials, but Li₂CO₃ requires a higher temperature. Mg doping is shown to be beneficial in lowering the temperature required to get fully lithiated, crystalline material. Additional experiments show that synthesis with a 480 °C preheat step, or synthesis directly from individual metal hydroxides (without a precursor), could be used as potentially viable alternative synthesis methods.

Redox flow batteries (RFBs) are energy storage devices designed for grid-scale application. For next generation RFBs it is desirable to develop low cost materials with low ohmic resistance and high transport selectivity. We present a composite membrane for the vanadium redox flow battery (VRFB) consisting of a composite of a porous polypropylene separator laminated with a thin film of polybenzimidazole (PBI). PBI layers are prepared by solution casting to obtain thicknesses in the range of 0.2 to 10 μm. The ohmic resistance of vanadium electrolyte imbibed PBI is ∼50 mOhm·cm² per micrometer of film thickness at room temperature. In cell tests, composite membranes show higher coulombic efficiency compared to Nafion® 212. Composite membranes with a PBI layer thickness of 1 μm and below outperform Nafion® 212 in terms of energy efficiency and discharge capacity up to a current density of 250 mA cm⁻². With thicker PBI films the ohmic cell resistance is excessively high. Over 100 charge-discharge cycles a higher rate of capacity fading is observed for a composite membrane with 0.7 μm PBI compared to Nafion® 212, which is a result of a more pronounced net electrolyte flux from the negative to the positive electrolyte.

A full depth of discharge mathematical model for the lithium trivanadate cathode, considering lithiation of the layered α-phase, phase change, and lithiation of the rock-salt like β-phase at lower potentials, is developed. The coupled electrode-scale and crystal-scale model is fit to electrochemical data, and additionally validated with operando EDXRD. There is good agreement between the simulated and measured spatial variation of the volume fraction of the β-phase. This mathematical model is used to guide electrode fabrication, accounting for both ionic and electronic transport effects. Values of three design parameters—electrode thickness, porosity, and volume fraction of conductor—are identified, and the sensitivity of the energy density to these design parameters is quantified. The model is also used to investigate electrode design to create electrodes that deliver the maximum achievable energy density under the constraint that the α to β-phase transition is avoided, since phase change has been demonstrated to reduce cycle life. The energy density sacrificed to avoid phase change decreases at higher discharge rates, but the target values for electrode fabrication remain the same as those when optimizing the electrode for the full depth of discharge.

Poly(acrylic acid) (PAA) is added as a binder to the water-based slurry of Ni-rich Li(Ni_0.8Co_0.1Mn_0.1)O₂ (NCM811) powder. After adding PAA, the pH of the slurry changes from strongly alkaline to nearly neutral (pH9.0), making it suitable for casting on the aluminum current collector without corroding the aluminum (Al) and a largely increased adhesion from 318 to 458 kg m⁻² after drying. The use of PAA also improves the dispersion of the slurry, because the carboxyl groups of PAA can interact with NCM811 to help stabilize the electrode particles in the slurry. Given the improved dispersion, reduced corrosion potential, and better adhesion, the resultant NCM811 cathode exhibits good structural integrity and greatly lowered charge-transfer resistance from 37.0 to 8.5 Ω, showing a high initial capacity of 189.2 mAh g⁻¹ and capacity retention of 84.2% after 100 charge-discharge cycles under 0.2C.

In this paper, the dependency on the metal deformation of the anode and electrochemical performance in an Al-air battery is investigated. We notably find a strong dependency in which the electrochemical performance is significantly governed by the dislocation density of the metal. Three specimens of different dislocation densities are prepared through a cold-rolling press: (і) 3.0 × 10¹⁵ m⁻², (ⅱ) 6.5 × 10¹⁵ m⁻², and (ⅲ) 19 × 10¹⁵ m⁻². The peak power densities of the three Al-air batteries show 252, 219 and 174 mWcm⁻², respectively. We conclude that the high mechanical properties (i.e., high dislocation density and hardness) are related to the electrochemical performances in Al-air battery.

In dual–ion batteries (DIBs), it is a key issue to search for electrolyte solutions compatible with graphite positive electrode. The solutions of LiPF₆ dissolved in short chain esters like ethyl methyl carbonate or methyl propionate have emerged as suitable choices, in which graphite positive electrode can deliver a PF₆^– storage capacity about 100 mA h g^–1. However, in a much shorter chain ester, methyl acetate (MA), the PF₆^– storage capacity delivered by graphite electrode is limited to 60 mA h g^–1. In this paper, the flame–retardant solvent of trimethyl phosphate (TMP) is introduced into LiPF₆–MA solutions to improve the electrochemical performance of graphite electrode. The reversible capacity can be enhanced to near 90 mA h g^–1 in 3 M LiPF₆–MA/TMP (6:4 by vol.). Traditional electrochemical tests in combination with ex situ/in situ X–ray diffraction (XRD) characterizations have been applied to probe the charge storage mechanism across the interfaces between graphite electrode and electrolyte solutions. Raman/fourier transform infrared (FTIR) spectra and nuclear magnetic resonance (NMR) spectra have been carried out to explore the solvation states of ions in the solutions.

In this study, P2-type K_0.7[Cr_0.85Sb_0.15]O₂ (KCSO) is prepared via a solid-state route and its electrochemical properties are compared with those of P2-K_0.62Na_0.08[Cr_0.85Sb_0.15]O₂ (IE-KCSO), which is prepared via an electrochemical ion-exchange of P2-Na_0.7[Cr_0.85Sb_0.15]O₂. Despite the near-identical chemical compositions and crystallographic structures, the IE-KCSO demonstrates rate capability and cyclic stability that is distinctively better than those of KCSO when used as a cathode in potassium-ion batteries (KIBs). For example, while KCSO shows a significant reduction in discharge capacities at high rates (48 mAh·g⁻¹ at 2C vs 70 mAh·g⁻¹ at 0.1C), IE-KCSO retains substantial capacities at high rates (67 mAh·g⁻¹ at 2C vs 78 mAh·g⁻¹ at 0.1C). The cyclic stability of IE-KCSO is also superior, as it delivers 96% of initial capacity after 100 charge/discharge (C/D) cycles, in contrast to 76% retention for KCSO. This study confirms that the Na⁺ ions remaining in IE-KCSO contribute to the fast K⁺ diffusion and, thereby, to its superior rate capability. Smaller dimensional changes in IE-KCSO during C/D are also apparent and these result in better cyclic stability. This work suggests that preparing KIB cathode materials via an ion-exchange protocol is more efficient than direct synthesis, particularly when the latter creates difficulties in obtaining phase-pure target compounds.

In recent work, we developed a set of equations that can be used to treat Li plating and subsequent electro-dissolution, and we analyzed how the equation system behaved for a particle of graphite, a fundamental unit of the negative electrode in lithium ion cells. In this work, we apply the same governing equations to the more realistic setting of a porous electrode consisting of many graphite particles. We propose a Li activity model wherein the activity of plated lithium differs from the activity of bulk Li in a thin layer (on the order of monolayers) at the interface with the graphite substrate and transitions smoothly to the activity of bulk Li at greater distances from the graphite interface. Since it is unclear at this point exactly how large this interfacial layer should be, we also show how to treat the limiting case, in which the interfacial layer thickness goes to zero and the activity of any deposited Li is that of bulk Li, which significantly complicates the porous-electrode analysis. We find the two approaches (i.e., finite thickness on the order of monlayers and zero thickness for the interfacial layer) yield very similar results.

In the present study, Co₃O₄ nanowires have been synthesized and coated uniformly on nickel foam (NF). The excellent electrochemical performance was demonstrated by the binder-free electrode material in 3 M KOH electrolytes; excellent specific capacitance of 1140 F g⁻¹ at 1 A g⁻¹ with 93.3% of its initial value is retained after galvanic charge-discharge (GCD) cycles of 5000. Activated carbon as negative and Co₃O₄ as a positive electrode is assembled in a hybrid supercapacitor device (HSC). HSC shows high capacitance retention 95 F g⁻¹ at 1 A g⁻¹ with maximum power density (11.80 kW kg⁻¹ at 18.20 Wh kg⁻¹) and high rate capability (58.26 F g⁻¹ at 15 A g⁻¹). The tremendous electrochemical performance could be attributed to the nanowire-like structure of Co₃O₄ on nickel foam which provides a high rate for ion diffusion and facilitates rapid transfer of electron and ion on the Co₃O₄/electrolyte interfaces. Obtained results indicate that synthesized Co₃O₄ nanowires with enhanced performance are potential electrode candidates for energy-storage applications.

Li plating on graphite anode is known to be one of the bottlenecks for fast charge of Li-ion batteries and a Li/graphite half-cell has been often used to determine lithiation rate capability of the graphite electrode. In this work, a three-electrode Li/graphite cell with a graphite loading of 3.72 mg cm⁻² is used to simultaneously record the cell's voltage and graphite's potential during the Li/graphite cell is lithiated at different current rates. It is surprisingly found that the polarization of a Li/graphite cell is dominated by the Li counter electrode, and that the lithiation capacity of graphite is centered in a narrow potential range between 0.068 V and 0.200 V vs Li/Li⁺. Impedance analysis reveals that the former is because the Li counter electrode has much larger charge-transfer resistance compared with the graphite electrode. As such, over-potential of the Li counter electrode can readily drive the potential of graphite to negative, leading to Li plating, even at moderate lithiation rates. The results of this work indicate that the lithiation rate capability of graphite determined from a Li/graphite half-cell is largely undervalued, and that an alternative technique is needed for accurate determination of the lithiation rate capability of graphite electrode.

Nickel-rich NCM (LiMO₂, with M = Ni, Co, and Mn) cathode active materials for lithium-ion batteries are being increasingly commercialized due to their high specific capacity. However, their capacity retention upon cycling is impaired by crack formation of NCM secondary agglomerates induced by the volume change upon repeated (de)lithiation that depends on the nickel content and the cutoff potential. Particle cracking leads to loss of electrical contact and enhanced side reactions caused by an increased surface area. Here, we introduce a novel method based on electrochemical impedance spectroscopy (EIS) in blocking conditions to quantify the increase in the active material's surface area upon cycling, utilizing the correlation between the surface area of the electrode and the electrochemical double-layer capacitance that is validated experimentally by comparing the capacitance and BET surface area increase of NCM electrodes upon mechanical compression. To quantify the cracking of the particles upon 200 charge/discharge cycles, we perform in situ EIS measurements utilizing a micro-reference electrode and monitor the cathode's impedance response. In addition, the crack formation of cycled NCM particles is validated visually by post mortem FIB-SEM. The effect of volume change on cracking is illuminated through the analysis of LFP and LTO as model materials.

While lithium-sulfur (Li-S) batteries promise very high gravimetric energy densities, they typically suffer from short cycle life and low power densities, particularly at high electrode loadings. Highly concentrated electrolytes (2M-5M) may demonstrate improved capacity retention, but at the expense of added weight and cost of electrolyte salts and reduced rate performance. Here we report our counter-intuitive findings on very promising performance of electrolyte compositions with salt concentrations below 0.3M. Such a low concentration enables effective use of unconventional salts and electrolyte additives which do not dissolve in the ether-based solvents at higher concentrations typically used in experimental and commercial batteries, thus substantially increasing cell design freedom. The significantly lower viscosity of the low concentration electrolytes also allows for faster electrolyte permeation. This report opens a new and promising field of studying low concentration electrolytes for Li-S and likely other chemistries.

To sustain the continuous high-rate charge current required for fast charging of electric vehicle batteries, the ionic effective diffusion coefficient of the electrodes must be high enough to avoid the electrode being transport limited. Tortuosity factor and porosity are the two microstructure parameters that control this effective diffusion coefficient. While different methods exist to experimentally measure or calculate the tortuosity factor, no generic relationship between tortuosity and microstructure presently exists that is applicable across a large variety of electrode microstructures and porosities. Indeed, most relationships are microstructure specific. In this work, generic relationships are established using only geometrically defined metrics that can thus be used to design thick electrodes suitable for fast charging. To achieve this objective, an original, discrete particle-size algorithm is introduced and used to identify and segment particles across a set of 19 various electrode microstructures (nickel-manganese-cobalt [NMC] and graphite) obtained from X-ray computed tomography (CT) to quantify parameters such as porosity, particle elongation, sinuosity, and constriction, which influence the effective diffusion coefficient. Compared to the widely used watershed method, the new algorithm shows less over-segmentation. Particle size obtained with different numerical methods is also compared. Lastly, microstructure-tortuosity relationship and particle size and morphology analysis methods are reviewed.

We design Al-doped V₂O₃ (Al_xV₂O₃) compounds as cathodes of aluminium battery. A citric acid-assisted simple solid-state synthesis is used to produce Al_xV₂O₃ compounds by heating, at different temperature, a reaction mixture of NH₄VO₃, Al(NO₃)₃·9H₂O and citric acid under Ar flow. Al-doping in-between layers and at lattice sites of V₂O₃ is confirmed by structural, vibrational and chemical analyses. The doped compounds obtained at 600 °C and 800 °C are confirmed as Al_0.56V₂O₃ and Al_0.53V₂O₃ corresponding to theoretical capacities 488 and 490 mAh g⁻¹, respectively, for the extraction of doped Al by considering three electron transfer (Al/Al³⁺). The as-synthesized Al_xV₂O₃ compounds are tested as cathodes in aluminium battery with 1.0 M AlCl₃:[EMIM]Cl electrolyte. The electrodes of Al_0.56V₂O₃ and Al_0.53V₂O₃ exhibited the first charge capacity of 415 and 385 mAh g⁻¹, respectively. The electrochemical extraction of doped Al is confirmed by comparisons with bare V₂O₃ control cathodes and post-cycling structural studies. The extraction of doped Al from Al_xV₂O₃ indicates its promising use in high capacity cathode for Al-ion battery.

Fast charging of lithium-ion batteries remains one of the most delicate challenges for the automotive industry, being seriously affected by the formation of lithium metal in the negative electrode. Here we present a physicochemical pseudo-3D model that explicitly includes the plating reaction as side reaction running in parallel to the main intercalation reaction. The thermodynamics of the plating reaction are modeled depending on temperature and ion concentration, which differs from the often-used assumption of a constant plating condition of 0 V anode potential. The reaction kinetics are described with an Arrhenius-type rate law parameterized from an extensive literature research. Re-intercalation of plated lithium was modeled to take place either via reverse plating (solution-mediated) or via an explicit interfacial reaction (surface-mediated). At low temperatures not only the main processes (intercalation and solid-state diffusion) become slow, but also the plating reaction itself becomes slower. Using this model, we are able to predict typical macroscopic experimental observables that are indicative of plating, that is, a voltage plateau during discharge and a voltage drop upon temperature increase. A spatiotemporal analysis of the internal cell states allows a quantitative insight into the competition between intercalation and plating. Finally, we calculate operation maps over a wide range of C-rates and temperatures that allow to assess plating propensity as function of operating condition.

Numerical physics-based models for Li-ion batteries under abuse conditions are useful in understanding failure mechanisms and deciding safety designs. Since battery design is generally required to decrease the failure risks while increasing the performance, multi-objective optimization methods are useful. Nevertheless, these usually require huge computational costs because these models targeting abuse battery conditions generally have many input physical parameters and computational costs for calculating one result are high. Therefore, we develop a framework for performing multi-objective optimization at a reasonable computational cost using machine learning methods. With this framework, an inverse analysis of optimal Li-ion battery design conditions, including safety conditions, is performed. Nail penetration simulations on different input conditions are performed so as to build a database for battery design conditions/test conditions (descriptors) and safety/performance (predictors). As a result of analyzing the relationship between descriptors and predictors, a high correlation between fire spread and negative electrode active material diameter is confirmed. Furthermore, a regression model to predict the database is created with a Gaussian process model. Using the model and a genetic algorithm, optimal design conditions are searched, and the design conditions that offer higher safety and better performance are identified under the assumed conditions.

Solid polymer electrolytes (sPE) offer a pathway for safer, less flammable lithium batteries. However, developing a polymer that provides high Li⁺ mobility as well electrochemical stability remains a challenge, because ion conductive functional units in the polymer main-chain (e.g., polycarbonate and polyether) usually suffer from poor electrochemical stability at high and low potentials. Herein, an sPE with pendent carbonate on a hydrocarbon backbone has been designed and synthesized to overcome conductivity and electrochemical stability problems. This pendant polycarbonate is different from conventional polycarbonate electrolytes because the carbonate moiety is in the sidechain, which mitigates polycarbonate backbone stability problems while still providing high ionic conductivity when used with a plasticizer. Conductivity as high as 1.1 mS cm⁻¹ at 22 °C was obtained. Stable lithium metal plating and stripping using the sPE was observed for 1,200 h and electrochemical stability up to 4.6 V vs Li⁺/Li has been demonstrated. The low interfacial resistance (<160 ohmcm² at 22 °C) and reasonable ionic conductivity have enabled acceptable cycling performance in a Li-LiFePO₄ battery at 0.98 mA cm⁻² for 2,300 cycles.

Slurry making is a critical step that can irrevocably affect the subsequent steps in battery manufacturing. Many experimental parameters, including the mixing sequence, must be considered in making the slurry. In this work, we investigated the effects of the two main industry-used mixing sequences on the rheological behavior of the slurry, and the relation of the slurry rheology to structural, mechanical, and electrochemical performance of LiNi_0.33Mn_0.33Co_0.33O₂ (NMC) electrodes. We show that: (1) mixing carbon black (CB) with polyvinylidene fluoride (PVDF) solution before adding NMC can facilitate the formation of a gel-like slurry; (2) porous clusters of CB/PVDF can form around NMC after drying the gel-like slurry, providing a high C-rate capability; (3) dry powder mixing of CB and NMC can facilitate the binding of the CB to the NMC surfaces, reducing the amount of CB in the PVDF and resulting in a liquid-like slurry; (4) after drying of the liquid-like slurry, a dense CB/PVDF layer can form on the NMC surfaces; and (5) this dense layer can provide high binding strength but may block ionic transport and weaken the electronic connection, reducing the C-rate capability. Thus, it is critically important to understand the effects of mixing sequence in electrode manufacturing.

Layered metal oxides with high nickel content are commonly used cathode materials in commercial lithium ion batteries due to high capacity and lower cost resulting from higher nickel content and lower cobalt content. Cathodes with increased nickel content suffer from rapid capacity fade due to a combination of thickening of the anode solid electrolyte interphase (SEI) and impedance growth on the cathode after extended cycling. While transition metal catalyzed degradation of the anode SEI has been widely proposed as a primary source of capacity loss, we propose that a related acid induced degradation of the anode SEI also occurs.

Because of their higher energy density, compared to lithium-ion batteries, rechargeable lithium-metal batteries have been considered one of the most attractive next-generation energy-storage systems. Uneven deposition of lithium during charge results mainly from two processes. At the peak of lithium dendrites (or lithium hump) a fresh SEI is formed. This freshly formed SEI has a higher concentration of defects, thus higher lithium-ion conductivity. Another mechanism is the preferential lithium-ion conduction at the grain boundaries (GB) in the SEI, at which the concentration of lithium-ion defects is higher than in the bulk of the crystals. During discharge (lithium dissolution), dead lithium, (lithium particles that are electrically disconnected from the current collector) is formed. In this work we studied the effects of several parameters, in carbonate-based electrolytes, on the properties of the SEI and on capacity losses. The effects of vinyl carbonate (VC) and fluoroethylene carbonate (FEC) additives, current density and cycle number on the total capacity loss (Q_TL, Q deposition—Q dissolution), the capacity needed to repair the SEI after dissolution of lithium (Q_{SEI repair}), two types of dead lithium, roundtrip coulombic efficiency and on the correlation among them, will be discussed. Elucidation of these phenomena will lead to the improvement of the lithium deposition/dissolution (charge and discharge) processes in lithium-metal rechargeable batteries.

The microstructures of Li-ion positive composite electrodes designed for EVs have been characterised at different scales and in particular by FIB/SEM nanotomography. These electrodes are composed of Li(Ni_0.5Mn_0.3Co_0.2)O₂, carbon black (CB), and polyvinylidene fluoride (PVdF). The component proportions in the electrodes and the electrode densities were varied. Specific image analysis tools have been developed to quantify the microstructure parameters that will influence the transport and exchange properties of ionic and electronic charges during battery operation. Different porosities have been highlighted, in particular the micrometric porosity which appears to be the most effective for the ion diffusion in the liquid electrolyte due to its low tortuosity and large intra-connectiviy. Different parallel paths for the transport of electrons in solid phases such as the CB/PVdF percolating network and a hybrid one consisting of CB/PVdF islands distributed on the NMC cluster surface and the NMC grains pertaining to these clusters. This last network can be effective when the CB/PVdF islands allow the electrons to short-circuit the resistive NMC grain boundaries.

Herein, ultra-tiny Sb-doped SnO₂ nanoparticles were prepared using co-precipitation as superior catalyst for vanadium redox reactions. Different concentrations of Sb in range of 2%, 5%, and 10% were doped in lattice structure of SnO₂. The size of nanoparticles decreased, as doping concentration increased. Sb doping also decreased the crystallinity of SnO₂, producing structural defects. It is notable that Sb-doped SnO₂ showed greatly improved conductivity. However, excessive Sb doping reduced conductivity of SnO₂. Sb-doped SnO₂ exhibited better electrocatalysis for V³⁺/V²⁺ and VO₂⁺/VO²⁺ reactions. It benefits from Sb-doped SnO₂ with smaller size, more structural defects, and higher conductivity, increasing active sites and electron transfer rate for vanadium redox reactions. SnO₂/Sb-5% showed the best electrocatalysis. SnO₂/Sb-5% was used to modify graphite felt, such that it had better electrochemical performance for vanadium redox reactions. A cell using SnO₂/Sb-5% improved electrolyte usage and discharge capacity retention at 50 mA cm⁻² for 50 cycles. SnO₂/Sb-5% also efficiently reduced electrochemical polarization of cell. The cell using SnO₂/Sb-5% had higher energy efficiency compared to pristine cell. At 150 mA cm⁻², the energy efficiency of modified cell increased by 9.2% compared with pristine cell (57.3%). Therefore, Sb-doped SnO₂ can be used as a promising catalyst for vanadium redox reactions.

The bromine-bromide redox couple is a promising solution for aqueous cathodes of several flow batteries. In this work, we present an experimental characterization of the system Br₂-HBr-H₂O at chemical equilibrium, featuring isothermal measurements of Open Circuit Voltage (OCV), density and conductivity in solutions with concentrations up to 2 M Br₂ and 4 M HBr. An equilibrium model considering polybromides formation that fits experimental data with an accuracy of 1.8 mV is presented. Information on activity coefficients and equilibrium constants of polybromides can be extrapolated from the model. Furthermore, alternative approaches are considered to effectively fit the measured voltage using algebraic equations, that provide a convenient tool for flow battery modeling at system-level.

With rapidly rising demand of power in the field of flexible and wearable electronics, electrolytes being one of the influential components of the electrochemical energy storage devices and are getting more attention as their physical and chemical properties play vital role in device performance. Hydrogel electrolytes are emerging as novel materials for use in supercapacitors due to their diverse 3D porous network, bendable structure and tuneable properties. In the present work, Poly (acrylic acid) hydrogel has been synthesized using free-radical polymerization in the presence of chemical crosslinker N,N'-methylene bisacrylamide (MBA). The prepared hydrogels were soaked in four different molar concentration of lithium perchlorate (LiClO₄) for 48 h to form double network hydrogel electrolytes. The structural and morphological characteristics of hydrogel electrolytes have been investigated using Fourier transform infrared-attenuated total reflectance (FTIR-ATR), X-ray diffraction and field emission scanning electron microscope (FESEM). In addition, the mechanical strength of hydrogel electrolytes was observed. The electrochemical studies including cyclic voltammetry (CV) and galvanic charge-discharge (GCD) investigated the performance of fabricated cells (AC/AA1/AC, AC/AA2/AC, AC/AA3/AC, and AC/AA4/AC) using hydrogel electrolytes in terms of specific capacitance, energy density and power density. Electrochemical studies show that AC/AA3/AC (activated carbon/acrylic acid (1.5 M LiClO₄)/activated carbon) is the optimised electrochemical cell among the fabricated cells of hydrogel electrolytes. AC/AA3/AC achieved maximum specific capacitance of 115 F g⁻¹ at 3 mV s⁻¹ and 132.20 F g⁻¹ at 50 mA g⁻¹ with energy density and power density of 18.36 Wh kg⁻¹ and 1000 W kg⁻¹, respectively. All the results indicated significantly that poly (acrylic acid)/LiClO₄ hydrogel electrolytes are competitive candidates for application in supercapacitors.

Hierarchical C@MoS₂ hollow spheres assembled from few layer-MoS₂ nanosheets coated on both interior and exterior surfaces of hollow carbon spheres (HCSs) have been developed by a modified template method. The polydopamine-derived carbon shell functions as a support with a negatively charged surface resulting in the in situ growth of few layer-MoS₂ nanosheets and prevents them from agglomeration with an integrated structure. In addition, the hollow carbon spheres with their mesopores provide sufficient liquid-solid contact area and shorter electron and ion pathways, as well as buffer for volume changes occurring during the charge/discharge process. The prepared C@MoS₂ material is characterized by XRD, TGA, BET, Raman, SEM, HRTEM and XPS measurements. When applied as a negative electrode material in LIBs, the C@MoS₂ electrode exhibits high reversible gravimetric capacity (1100 mAh·g⁻¹ at 0.1 C), superior rate performance (633 mAh·g⁻¹ at 20.0 C) and superb cycling life (86.0% of its original specific capacity left after 130 cycles).

Lithium-sulfur (Li-S) batteries are a promising technology capable of reaching high energy density of 500–700 Wh kg⁻¹, however the practically achievable performance is still lower than this value. This hindrance can be attributed to a lack of understanding of the fundamental electrochemical processes during Li-S battery cycling, in particular the so-called redox shuttle effect which is due to the relatively high solubility of polysulfide intermediates in the electrolyte. Herein, the effects of LiNO₃ as an additive as well as C₄mpyr-based ionic liquids (ILs) in electrolyte formulations for Li-S cells are analysed using in situ X-ray powder diffraction (XRD) and ex situ soft X-ray absorption spectroscopy (sXAS) techniques. Whilst LiNO₃ is known for its protective properties on the lithium anode in Li-S cells, our studies have provided further evidence for suppression of Li₂S deposition when using LiNO₃ as an additive, as well as affecting the solid electrolyte interphase (SEI) layer at a molecular level. Moreover, the detected sulfur species on the surface of the anode and cathode, after a few cycles are compared for IL and organic-based electrolytes.

Nano-oxides and hydroxides generate great interest as promising positive electrode materials for the development of high energy density supercapacitors. However, their usually limited ionic and electronic conductivities significantly decrease their energy storage performances when increasing the electrode's mass loading. Here, we report on a sonochemical approach to functionalize the surface of Co(OH)₂ nanomaterials by EmimBF₄ ionic liquid that greatly improves the stability and the electrochemical performances of high mass loading electrodes (13 mg cm⁻²). This surface functionalization boosts the transport properties and strongly enhances the capacity as well as the capacity retention at higher current densities compared to basic Co(OH)₂ (e.g. 113.5 C g⁻¹ vs 59.2 C g⁻¹ at 1 A g⁻¹). Additionally, the protective layer formed by the ionic liquid stabilizes the electrode material upon cycling in KOH aqueous electrolyte and protects the material from oxidation upon open-air storage.

Solid-state rechargeable lithium batteries are considered as one of the promising energy storage technologies due to their safety and high energy density. While developing better solid-state batteries is hampered by the poor interfacial compatibility. In this work, one novel design of buffer layer using the Li_1+xAl_xTi_2−x(PO₄)₃ (LATP) solid electrolyte is reported to address the poor compatibility and big migration gap at the electrode-solid electrolyte interface. Such a facile design works well on facilitating the interfacial ionic inter-diffusion by padding the gap of ionic conductivity between electrode and electrolyte, as well as passivating the electric activity of interface region to avoid the continuously interfacial degradation, hence makes the interface more homogeneous and intimate to deliver the superior electrochemical performance. Moreover, upon cycling, a new carbon-rich interphase is revealed from electron microscopy in the interface region, which probably plays an important role in stabilizing the structure and regulating the electron/ion fluxes. All these findings provide a rewarding avenue to resolve the interfacial issues of solid-state lithium ion batteries and the integrated electronic devices.

Electrochemical impedance spectroscopy (EIS) has been proposed as an in situ strategy for the analysis of materials properties applied in the study of lithium-ion batteries (LIBs). However, the number and physical nature of the processes occurring simultaneously, combined with the typical interpretation of EIS spectra make the study challenging. To make the EIS interpretation more inclusive, in this work a graphical Bode diagram deconvolution is proposed, utilizing time constants τ (R-CPE), associated with relaxation of the phenomena occurring in battery composite electrodes. Since the effect of the additives on the electrode composite is still controversial and difficult to analyze for other in situ techniques, the graphical strategy is first applied to a LiFePO₄ cathode with PVDF as the binder, to discriminate the contribution of each τ during different state of charge (SOC). This is done by removing the influence of counter electrode using a commercial three-electrode set-up cell. Then, the same cathode was evaluated, but with a Single Lithium-Ion Conducting Binder (SLICB). The electrode modification was easily observed with the graphical analysis. The results show that SLICB improved the speed of the processes, moving them to high frequencies, given that the polymer provides a continuous supply of ions diminishing concentration polarization.

Aim of investigation is to study the possibility of activating a promising Ni(OH)₂, prepared using two-step high-temperature synthesis, by adding 3%, 5% and 10% (mol.) Al³⁺ to Ni²⁺. For describing the intercalation of Al³⁺ into hydroxide structure, "Separate-Solid—Liquid—Solid" mechanism, which included the formation of separate Al-containing phase on synthesis stage, and incorporation of Al³⁺ into Ni(OH)₂ or formation of surface compounds during hydrolysis stage, has been proposed. EDX analysis of precursor confirmed the formation of separate Al-containing phases. By means of PXRD, EDX, SEM, TEM revealed realization of both ways of Al³⁺ incorporation: at high amounts of Al³⁺ (5% and 10% mol.), predominantly surface compounds are formed with distorted and altered particle shape and appearance of "core–shell" particles. At low amounts of Al³⁺ (3% mol.), permeably doping occurs, with partial intercalation of Al³⁺ into the nickel hydroxide structure. Based on CVA and GCDC results, Al³⁺ acts as a poison upon the formation of surface compounds have been found. Upon doping of hot hydrolysis samples with aluminum, sample activation was observed, which resulted in an increase of specific capacity by 1.99 times, from 569 Fg⁻¹ (pure Ni(OH)₂) to 1112 Fg⁻¹.

In the present work, nitrogen and sulphur co-doped porous carbon materials are obtained by using ammonium sulphate as a template. The multi-role of ammonium sulphate as an activating agent and as nitrogen and sulphur dopant is investigated. The resulting porous carbon material achieved high doping level (9.3 at% for nitrogen and 3.5 at% for sulphur) and increased interlayer spacing from 0.35 to 0.38 nm which improves the storage kinetics of Na⁺-ions inside the carbon lattice. The synthesized materials, when used as negative electrodes for sodium-ion battery, provide promising electrochemical performance with a reversible storage capacity of 439 mAh g⁻¹ at a current density of 10 mA g⁻¹. The storage capacity of ∼100 mAh g⁻¹ with capacity retention of 62% retained after 200 cycles at 220 mA g⁻¹. This work presents the multifunctional roles of ammonium sulphate in achieving the nitrogen and sulphur co-doped porous carbon materials.

In liquid electrolyte-type lithium-ion batteries, Nickel-rich NCM (Li_1+x(Ni_1−y−zCo_yMn_z)_1−xO₂) as cathode active material allows for high discharge capacities and good material utilization, while solid-state batteries perform worse despite the past efforts in improving solid electrolyte conductivity and stability. In this work, we identify major reasons for this discrepancy by investigating the lithium transport kinetics in NCM-811 as typical Ni-rich material. During the first charge of battery half-cells, cracks form and are filled by the liquid electrolyte distributing inside the secondary particles of NCM. This drastically improves both the lithium chemical diffusion and charge transfer kinetics by increasing the electrochemically active surface area and reducing the effective particle size. Solid-state batteries are not affected by these cracks because of the mechanical rigidity of solid electrolytes. Hence, secondary particle cracking improves the initial charge and discharge kinetics of NCM in liquid electrolytes, while it degrades the corresponding kinetics in solid electrolytes. Accounting for these kinetic limitations by combining galvanostatic and potentiostatic discharge, we show that Coulombic efficiencies of about 89% at discharge capacities of about 173 mAh g_NCM⁻¹ can be reached in solid-state battery half-cells with LiNi_0.8Co_0.1Mn_0.1O₂ as cathode active material and Li₆PS₅Cl as solid electrolyte.

Organic electrode materials for lithium-ion batteries are essential tools for energy storage systems starting from portable electronics to electric vehicles. Many attempts have been made to improve the electrochemical behavior of organic electrode materials for lithium-ion batteries. Herein we have proposed a new electrode material called Aurin tricarboxylic acid synthesized via the condensation of aldehyde and acid in the presence of sodium nitrite which is further converted into the metal-organic framework using copper salt to increase its conductivity and used as an anode material for both aqueous and non-aqueous rechargeable lithium-ion batteries. The electrochemical performance of modified Aurin Tricarboxylic acid copper metal-organic framework (ATC-MOF) was studied using cyclic voltammetry, galvanostatic cycling with potential limitation and Potentio electrochemical impedance spectroscopy techniques and the structures were confirmed using ¹H-NMR, FT-IR spectroscopy, and Powder XRD techniques. It exhibits excellent cyclability and a good discharge capacity of about 438.09 mA h g⁻¹ in a non-aqueous electrolyte and 169.69 mAh g⁻¹ in an aqueous electrolytic system. The electrochemical activity of the ATC-MOF shows that it can be used as electrode material in aqueous and non-aqueous rechargeable lithium-ion battery systems.

To develop feasible oxygen reduction reaction (ORR) for fuel cell technology and metal-air battery, it is crucial to find suitable replacement for platinum-based noble metal catalysts. N-doped carbon materials specially for graphene have been intensively investigated and proved to be efficient for ORR. In this work, to enhance performance of graphene-based electrocatalyst, we develop a facile method to prepare g-C₃N₄ quantum dot (QD) decorated g-C₃N₄ sheet/reduced graphene oxide (rGO) composite for efficient ORR. At first, a hydrothermal reaction gives a 3D g-C₃N₄ sheet/rGO matrix. Then, the g-C₃N₄ QDs are attached to the 3D g-C₃N₄ sheet/rGO matrix by simple stirring. The obtained product has high nitrogen content and provides sufficient active sites for ORR, showing excellent catalytic performance compared with Pt/C, which is attributed to as follows: the 3D honeycomb structure provides larger specific surface area for ORR; the addition of g-C₃N₄ QDs provides sufficient active sites to increase the reaction efficiency; high nitrogen content plays an important role in the progress for the oxygen reduction reaction. Present work provides possibility for the commercial application of non-metallic catalysts for ORR.

Silicon is a long-standing candidate for replacing graphite as the active material in negative electrodes for Li-ion batteries, due to its significantly higher specific capacity. However, Si suffers from rapid capacity fading, as a result of the large volume expansion upon lithiation. As an alternative to pure Si electrodes, Si could be used, instead, as a capacity-enhancing additive in graphite electrodes. Such graphite–Si blended electrodes exhibit lower irreversible-charge losses during the formation of the passivation layer and maintain a better electronic contact than pure Si electrodes. While previous works have mostly focused on the Si properties and Si content, this study investigates how the choice of graphite matrix can alter the electrode properties. By varying the type of graphite and the Si content (5 or 20 wt%), different electrode morphologies were obtained and their capacity retention upon long-term cycling was studied. Despite unfavorable electrode morphologies, such as large void spaces and poor active-material distribution, certain types of graphites with large particle sizes were found to be competitive with graphite–Si blends, containing smaller graphite particles. In an attempt to mitigate excess void-space and inhomogeneous material distribution, two approaches were examined: densification (calendering) and blending in a fraction of smaller graphite particles. While the former approach led in general to poorer capacity retention, the latter yielded an improved Coulombic efficiency without compromising the cycling performance.

Three quinone-based organic electrodes were tested in nonaqueous Zn-batteries using different salts and solvents. The Zn(TFSI)₂/acetonitrile system exhibited the best performance due to its excellent transport and electrochemical properties. The mechanistic studies on the electrode kinetics were also carried out. While 2,5-dimethoxybenzoquinone (DMBQ) displayed a typical faradaic battery behavior, its polymeric derivatives showed a slow charge transfer inside the polymeric film as depicted by cyclic voltammograms.

The majority of the ceramic solid electrolytes (LLZO, LATP) demonstrate polycrystalline grain/grain-boundary (G/GB) microstructure. Higher lithium (Li) concentration and lower mechanical stiffness result in current focusing at the GBs. Growth of Li dendrites through local inhomogeneities and subsequent short circuit of the cell is a major concern. Recent studies have revealed that bulk Li metal is a viscoplastic material that has low (∼0.3 MPa) and high (∼1.0 MPa) yield strength during deformation at smaller and larger rates of strain, respectively. It has been argued that during deposition at smaller current densities, due to its lower yield strength, Li metal should demonstrate plastic flow against stiff ceramic electrolytes, and Li dendrites will be prevented from penetrating through solid electrolytes. In this manuscript, a multiscale modeling framework has been developed for predicting properties of GBs and the bulk of ceramic electrolytes using atomistic calculations for input to mesoscale models. Using the parameters obtained from the atomistic simulations, the mesoscale model reveals that, given enough time, even at low charge rates, lithium dendrites can grow through the GBs of LLZO. The present multiscale model results also provide information regarding the dendrite growth velocity through LLZO.

The electrolyte additive lithium difluorophosphate improves the lifetime of lithium-ion cells. This work presents the synthesis and evaluation of alternative difluorophosphate salt electrolyte additives. Ammonium difluorophosphate is readily prepared via a solid-state, benchtop reaction of ammonium fluoride and phosphorus pentoxide that requires only gentle heating to initiate. The best yield of sodium difluorophosphate (NaFO) in the present study was obtained by reacting difluorophosphoric acid and sodium carbonate in 1,2-diemethoxyethane over 3 Å molecular sieves. Tetramethylammonium difluorophosphate was prepared from NaFO via cation-exchange with tetramethylammonium chloride. NaFO is here reported to be a very good electrolyte additive, with similar performance in NMC532/graphite pouch cells as the lithium salt. The beneficial nature of both additives is attributable to the difluorophosphate anion. In contrast, ammonium and tetramethylammonium difluorophosphates are found to be poor electrolyte additives. For the former, this is suggested to be due to the formation of lithium nitride and hydrogen gas.

Designing competitive and reliable Redox Flow Batteries (RFBs) requires the development of specific analytical tools at lab-scale. Specifically, the influence of the cycling conditions on the system performance must be well identified. An instrumented test bench dedicated to the tuning of the operating parameters and the monitoring of the battery internal behavior was developed. The use of a segmented cell with a 1D-like design allowed to focus on the local current distribution along the electrolyte flow. The study started by examining the performances of a RFB coupling the ferri/ferrocyanide couple (Fe(CN)₆³⁻/ Fe(CN)₆⁴⁻) to the anthraquinone Alizarin Red S, over 300 cycles. Once cycling in standard conditions was reviewed, a parameter study was performed to scan a varied range of operating points, by changing the current density, the flow rate and the temperature successively. Thanks to the spatially-resolved analysis of the cell, the global performance could be related to local processes. This investigation gave unprecedented insight of the internal operation of a RFB, with peculiar features appearing at the start of the charge and the discharge. It was shown that a same global response of the cell could actually hide very different internal operations.

Free-standing electrodes can be useful for a plethora of diagnostic measurements, as they allow transmissive measurements, stacking of electrodes, and/or measurements where the current collector would be disturbing the signal. Another advantage displayed in this publication is their use in Li-ion battery half-cells to decrease and stabilize the impedance of the counter electrode that is usually made of metallic lithium, allowing to conduct electrochemical impedance spectroscopy of a battery-type working electrode via μ-reference electrode which would otherwise show artefacts over a wide range of frequencies. Using measurements on an equivalent circuit mimicking a Li-ion battery half-cell with a μ-reference electrode we show how such artefacts arise from the large resistance in the μ-reference electrode and the imbalance in working and counter electrode resistance. We also show how the use of a free-standing graphite electrode attached to the Li-metal counter electrode (Li/FSG) reduces the counter electrode resistance and allows an artefact-free impedance measurement of the working electrode via a μ-reference electrode. Finally, we show the stability of the Li/FSG electrode and compare it to a Li-metal electrode.

In this study, an Al-0.08Sn-0.08Ga-0.5Mg alloy was annealed at 200 °C–400 °C for 10 h. The microstructure and corrosion morphology of the Al anode were observed by scanning electron microscopy (SEM), and the effects of different annealing temperatures on the electrochemical properties of the Al anodes were studied by the hydrogen evolution rate, open circuit potential, Tafel curves, EIS and constant current discharge. The results show that the annealing treatment had a certain effect on the number and size of precipitates on the alloy surface, which improved the electrochemical activity and corrosion resistance of the Al alloy. Additionally, the Al–Sn–Ga–Mg alloy anode material has an excellent discharge performance in the actual use process when the annealing temperature is 350 °C, the related performance parameters were greatly improved compared with other annealing temperature conditions. The capacity density is 2670.99 mAh·g⁻¹, and the energy density is 3379.15 mWh·g⁻¹.

Battery cathodes are complex multiscale, multifunctional materials. The length scale at which the dominant impedance arises may be difficult to determine even with the most advanced experimental characterization efforts, and thus modeling can play an important role in analysis. Discharge and voltage relaxation curves, interrogated with theory, are used to distinguish between transport impedance that arise on the scale of the active crystal and on the scale of agglomerates (secondary particles) comprised of nanoscale crystals. Model-selection algorithms are applied to determine that the agglomerate scale is dominant in the ${\rm{Li}}\left({{\rm{Ni}}}_{0.33}{{\rm{Mn}}}_{0.33}{{\rm{Co}}}_{0.33}\right){{\rm{O}}}_{2}$ electrode studied here. Furthermore, conditions where the agglomerate and crystal-scale models yield distinct simulation results are demonstrated, providing approaches that can be applied to other systems.

While the choices of active materials for redox flow batteries (RFBs) have grown substantially, very few can adequately serve in the positive side of a RFB. We attempt to address the challenge with an inexpensive, high-potential tris(bipyridyl)iron complex. Paired with methyl viologen, the complex enables a 1.4 V neutral RFB with 215 cycles at a current efficiency of 99.8% and capacity retention over 99.9% per cycle. The discharging process displays two peculiar plateaus due to the dimerization of ferric complexes, as confirmed by ex situ cyclic voltammetry and the UV–vis spectroscopy.

In this work, aprotic and protic ionic liquid (IL)-based electrolytes designed for calcium-based energy storage systems are investigated. We have shown that these electrolytes display good transport properties and electrochemical stabilities comparable with those of IL-based electrolytes proposed for lithium and sodium-based systems. The use of these electrolytes in electrochemical double layer capacitors (EDLCs) leads to the realization of devices displaying good capacitances paired with a high reversibility and stability. Their use in combination with TiS₂ cathode appears more problematic as the cation of the ILs is inserting in the layered structure of this material during the charge process. In this latter case a careful design of the cation appears necessary to guarantee selective insertion of Ca²⁺ and reversible charge-discharge process.

A molecular level understanding of the structure and energetics of the monovalent and divalent metal ion complexes is of great importance for development of next-generation batteries. In this contribution, Density Functional Theory (DFT) simulations at the ωb97xD/6–31 + G(d,p) level of theory are performed to investigate the interaction of metal ions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺) with 26 organic solvent molecules. The reduction energetics (electron affinity and reduction potential) and structural responses of the solvent molecules and the molecular complexes are discussed. The DFT calculations are carried out to investigate the structure, energetics and electron affinities of chelated complexes of water (H₂O), tetrahydrofuran (THF) and di-methoxy ethane (DME) solvent molecules. Additionally, ab initio dynamic simulations (AIMD) at 298 K using atom centered density matrix propagation (ADMP) formalism are performed to understand the spontaneous structure formation upon electron attachment of the metal ion-solvent complexes. The ADMP simulations indicate the decomposition of Mg⁺−(DME)₃ complex via cleavage of C–O bond of one of the three DME molecules indicating irreversible decomposition of DME in the presence of the Mg⁺ radical. We believe that the data collected as part of this investigation serves as a library of fundamental knowledge towards a deeper understanding of the electrode-electrolyte interfacial reactions.

Filling of the electrode and the separator with an electrolyte is a crucial step in the lithium ion battery manufacturing process. Incomplete filling negatively impacts electrochemical performance, cycle life, and safety of cells. Here, we apply concepts from the theory of partial wetting to explain the amount of gas entrapment that occurs during electrolyte infilling and show that this can explain the lower than expected effective transport coefficients that are measured experimentally. We consider a polyethylene separator as a model system. Quasi-static infilling simulations on 3D reconstructions of the separator structure indicate that there can be up to 30% gas entrapment upon infilling due to the geometry of the separator, which results in a reduction of effective transport by >40%. Considering the dynamics of the electrolyte (e.g., viscosity) and the infilling process explains why the residual gas phase is typically less (15%–20%) and why, for electrolytes that wet well, increasing viscosity leads to higher values of gas entrapment, which is observed experimentally as decreased effective electrolyte conductivity. This work highlights the importance of optimizing not only the physiochemical properties of the electrolyte and pore surfaces, but also the 3D structure of the pore space, providing insights how to do so.

Both electrochemically and chemically delithiated layered rock-salt Li_xNi_0.5Mn_0.5O₂ were successfully synthesized to investigate their crystal structures and cathode properties in the Mg rechargeable batteries. While the electrochemically delithiated Li_xNi_0.5Mn_0.5O₂ (x = 0.1 or 0.5) showed reversible behavior only two cycles in a Mg cell with subphase after initial discharge, the chemically delithiated Li_0.45Ni_0.5Mn_0.5O₂ delivered a discharge capacity of 175 mAh g⁻¹ with an average potential of 2.4 V vs Mg/Mg²⁺ during several cycles. The chemically delithiated structure with x = 0.45 was found to be able to intercalate Mg ions according to the Rietveld analysis for synchrotron XRD patterns and XANES spectra for discharged electrode. It was concluded that the chemically delithiated Li_0.45Ni_0.5Mn_0.5O₂ provided the favored structure for Mg intercalation due to the appropriate interlayer distance.

Poly(3,4-ethylenedioxythiophene) and its derivatives provide an excellent platform as electrode materials for supercapacitors due to their superior stability and conductivity. In this study, a poly(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol (PEDOT-MeOH) porous nanonet (PEDOT-MeOH-PNN), PEDOT-MeOH hollow nanotube array (PEDOT-MeOH-HNA) and PEDOT-MeOH-PNN coated PEDOT-MeOH-HNA (PEDOT-MeOH-PNN@PEDOT-MeOH-HNA) are successfully fabricated using a template-free electrodeposition of (2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methanol monomer. These three nanostructures were studied by Fourier transform infrared spectrum and Raman spectrum, scanning electron microscopy, thermal analysis and electrochemical methods, respectively. PEDOT-MeOH-PNN@PEDOT-MeOH-HNA has a specific capacitance of 40.5 mF cm⁻² at 40 mV s⁻¹, which is higher than PEDOT-MeOH-PNN (21.6 mF cm⁻²) and PEDOT-MeOH-HNA (35.5 mF cm⁻²). Moreover, the PEDOT-MeOH-PNN@PEDOT-MeOH-HNA based symmetric supercapacitor delivers excellent rate performance and superior cycling stability (90% of the initial capacitance remains after 10,000 cycles). The results indicate that the structural design of a supercapacitor electrode can improve their electrochemical performance, and promote the application and development of conducting polymers in the field of supercapacitors.

A lithium powder electrode is applied as an anode in a lithium-sulfur battery system to examine the effects of changes in the anode surface area on electrochemical behavior. Besides preventing dendrite growth, as in other lithium-ion batteries, the lithium powder anode achieves an elevation in lithium-ion transfer, which can be attributed to an increase in the exchange current density caused by expansion of the surface area of the anode. This promotion of lithium-ion diffusion also leads to an increase in lithium-ion transfer near the cathode site and contributes to the reversible reaction between the lithium ion and sulfur. As a result, the reversibility in cathodic reactions is enhanced, thereby improving its specific capacity and retention. Scanning electron microscopy and X-ray photoelectron spectroscopy reveal that the morphology of the cathode is maintained throughout the process, and a solid electrolyte interphase (SEI) with lower electrolyte decomposition can be constructed. Impedance analysis also confirms that a stable electrochemical reaction is achieved with low resistance values.

A novel poly(acrylamide-co-acrylic acid) (P(AM-co-AA)) coating layer is facilely introduced on the top of sulfur composite cathode. The polymer membrane owns abundant and well-distributed microporous framework, favoring large electrolyte uptake and high ionic conductivity. Upon activation with the liquid electrolyte, the porous matrix immediately swells, forming a gel polymer electrolyte coating (GPEC) cathode. Not only does the unique coating design greatly restrain the out-diffusion of polysulfides from the cathode, but also improves ion transport at the cathode/electrolyte interface and provides flexible surface protection for the electrode structure. The GPEC cathode exhibits relatively low polarization, high sulfur utilization and superior cycle stability, as compared to the conventional sulfur cathode.

The fabrication of all solid-state 3D micro-supercapacitor is challenging for powering connected and miniaturized emerging electronics devices in the frame of the future Internet of Things paradigm. Here we highlight the design of a specific solid electrolyte based on ethylmethylimidazolium bis(trifluoromethanesulfonate)imide confined within polyvinylidenefluoride which enables to meet the requirements of safety, easy packaging, and leakage free 3D micro-supercapacitors. This ionogel-based microdevice (2 mm × 2 mm footprint area) exhibits good cycling stability over 30 000 cycles with an areal energy density of 4.4 μWh.cm⁻² and a power density of 3.8 mW.cm⁻². It can also sustain the high temperature reflow soldering process (∼250 °C–5 min) without damage, which is performed to directly bond surface mounted miniaturized devices onto printed circuit boards. This strategy not only provides a reference for the design of high-performance 3D interdigitated micro-supercapacitors, but also paves the way to their further implementation in miniaturized electronic chips for Internet of Things applications.

The rechargeable Zn²⁺ ion batteries are promising for the sustainable energy storage device applications. Recently they have been extensively evaluated for finding new cathode material and prevention of dendrite growth at Zn plate anode. Herein we have evaluated redox active organic molecule 7,7,8,8Tetracyanoquino dimethane (TCNQ) as a cathode material for aqueous zinc battery with zinc plates as anode in 1 M ZnSO₄. The charging/discharging of the battery was associated with formation and deformation of Zn-TCNQ complex, which was confirmed by XRD and FTIR. The specific capacity of cathode was found to be 123.2 mAh g⁻¹ at 100 mA current density with 96% coulombic efficiency. Whereas specific capacity at 1 A current density was found to be 60 mAh g⁻¹ with 94% coulombic efficiency. In a cycling experiments we observed the fading of capacity with time by partial dissolution of Zn-TCNQ complex. The fading of capacity was prevented by confining TCNQ molecules inside the nano structures of newly prepared covalent organic polymers. The confinement remarkably increased the capacitance to 171 mAh g⁻¹ at 1 A current density. As the material is readily available and the absence of toxic inflammable volatile organic electrolytes in our battery this material offers a very good choice as cathode material for zinc battery.

Lithium metal is a high-energy-density battery electrode material, but the largely irreversible growth of lithium protrusions on an initially planar electrode during cycling makes it unsuitable for incorporation into a commercial battery. In this study, a lithium electrode with globular protrusions was stripped electrochemically, and the local morphology of the electrode as a function of time was determined by hard X-ray tomography. We demonstrate that globules are preferentially stripped compared to a planar electrode in our system, which incorporates a nanostructured block copolymer electrolyte. We report current density at the electrode as a function of micron-scale position and time. The local current density during the electrode healing process calculated from a reference frame at the electrode/electrolyte interface provides insight into the driving forces responsible for selective stripping of the globule. These results imply the possibility of discharging protocols that may return a lithium electrode to its initial planar state.

In this study, we present a novel cell design for liquid electrolyte-based lithium-ion batteries (LIBs) to detect the lithium distribution across an electrode by neutron depth profiling (NDP). This newly developed cell design allows to obtain electrochemical data comparable to a standard laboratory cell making use of 500 μm diameter holes to assure a homogeneous compression over the entire electrode area. We present operando NDP data recorded during the formation of a porous graphite electrode where we can both distinguish between irreversibly bound lithium within the solid electrolyte interphase (SEI) and reversibly intercalated lithium into graphite, and quantify the lithium concentration profile across the electrode. The amount of lithium reversibly intercalated into the graphite electrode (≈LiC₆), based on one lithium per electron of charge (1 Li/e⁻), was found to corroborate well with the lithium amount quantified using operando NDP. However, comparing the irreversible capacity with the amount of lithium detected as SEI within the graphite anode, a significantly smaller Li/e⁻ ratio was observed. Furthermore, we confirm that small amounts of lithium alloy into the copper current collector, using NDP and complementary ex situ X-ray photoelectron spectroscopy (XPS).

We performed molecular dynamics simulations of lithium-sulfur-graphene compounds using reactive force fields, providing a time scale to observe atomistic features relevant to the microscopic behavior of the of the bulk of sulfur-based cathodes to be used beyond our present Li-ion batteries. The samples we used were set to realistic geometries through sophisticated protocols to simulate ultrafast reactions that occur within the picosecond range, thus allowing us to get some insights into the characteristics of the bulk material in working cathodes of Li–S batteries, which are mixed with carbon to increase the poor electronic conductivity of S. We report chemical speciation and geometrical data at atomistic levels. We observed that slowly lithiated cathodes were more stable and with higher density than those that were suddenly fully-lithiated. We did not observe molecular Li₂S formation; however, we observed an amorphous solid arrangement with the same stoichiometry of Li and S, with S–Li–S angles of ∼111° and smaller ones due to the interaction between polysulfides that did not reacted totally. In addition, graphene keeps its planar shape; however, S₈ changes its shape from rings to chains. Lithiated structures are more stable with lower energies, and more close-packed structures than structures with Li already inserted.

Non-aqueous organic redox flow batteries (NORFBs) have emerged as a promising technology for renewable energy storage and conversion. High capacity and power density can be achieved by virtue of high solubility and high operating voltage of the organic anolytes and catholytes in organic media. However, the lack of anolyte materials with high redox potentials and their poor electrochemical stability retard the wider application of NORFBs. Here, we investigated an evolutionary design of a set of bipyridines and their analogues as anolytes and examined their performance in full flow batteries. Using combined techniques of repeated voltammetry, lower scan rate cyclic voltammetry, proton nuclear magnetic resonance, and density functional theory calculations, we could rapidly evaluate the redox potential, stability, and reversibility of these redox candidates. The promising candidates, 4-pyridylpyridinium bis(trifluoromethanesulfonyl)imide (monoMebiPy) and 4,4'-bipyridine (4,4'-biPy), were subjected to battery cycling. Extended studies of the post-cycling electrolytes were conducted to analyze the pathway of capacity fading and revealed a reduction-promoted methyl group shift mechanism for monoMebiPy. A family of easily accessible anolyte molecules with high redox stability and redox potentials was discovered that can be applied in NORFBs.

A Ni-rich layered cathode, Li[Ni_0.885Co_0.100Al_0.015]O₂ (NCA89), was compositionally modified to demonstrate that multiple doping can effectively stabilize the delithiated structure. Incorporation of B and Ga into the cathode substantially improved the cycling stability of the NCA89 cathode. The 0.25 mol% B– and 0.75- mol% Ga– doped NCA89 cathode retained 91.7% of its initial capacity after 100 cycles while delivering a discharge capacity of 222.2 mAh g⁻¹ at 0.1 C, whereas the pristine NCA89 cathode retained only 79.4% of its initial capacity. The multi-doped cathode exhibited excellent long-term cycling stability; it retained 83.4% of the initial capacity after 500 cycles compared to the P-NCA89 cathode that retained only 62.4%. We attributed the improved cycling stability to the incorporation of B, which modified the surface energy to produce a highly aligned microstructure conducive to relieving anisotropic internal strain, and Ga, which provided structural and chemical stability to the O-TM-O slab. Co-doping with Ga and B is an effective strategy to improve the cycling stability of Ni-rich layered cathodes, which are projected to be the power source for next-generation electric vehicles.

In this study, a synchrotron transmission X-ray microscopy tomography system has been utilized to reconstruct the three-dimensional (3D) morphology of all-solid-state lithium-ion battery (ASSB) electrodes. The electrode was fabricated with a mixture of Li(Ni_1/3Mn_1/3Co_1/3)O₂, Li_1.3Ti_1.7Al_0.3(PO₄)₃, and super-P. For the first time, a 3D numerical multi-physics model was developed to simulate the galvanostatic discharge performance of an ASSB, elucidating the spatial distribution of physical and electrochemical properties inside the electrode microstructure. The 3D model shows a wide range of electrochemical properties distribution in the solid electrolyte (SE) and the active material (AM) which might have a negative effect on ASSB performance. The results show that at high current rates, the void space hinders the ions' movement and causes local inhomogeneity in the lithium-ion distribution. The simulation results for electrodes fabricated under two pressing pressures reveal that higher pressure decreases the void spaces, leading to a more uniform distribution of lithium ions in the SE due to more facile lithium ion transport. The approach in this study is a key step moving forward in the design of 3D ASSBs and sheds light on the physical and electrochemical property distribution in the SE, active material, and their interface.

Cold rolled super duplex stainless steel (SDSS) were subjected to recovery (300 °C) and recrystallization (1020 °C) annealing. Annealing related microstructural changes were quantified with microtexture and phase-specific micro-hardness. Subsequent electrochemical characterization included potentiodynamic anodic polarization tests and Mott-Schottky analysis. It was established, for both single and two-phase specimens, that extensive recovery did not affect the electrochemical behavior, while the shortest recrystallization led to significant improvements in corrosion resistance. Improvements in corrosion performance of cold rolled SDSS was thus possible only through recrystallization, and associated removal of large lattice curvatures in the metallic substrate and reduced defect densities in the protective oxide film.

Electrochemical measurements were performed on Ni-30Co-16Cr-xMo and Ni-30Co-16Cr-xMo-2Cu (x = 7–15, wt%) alloys to clarify their electrochemical responses and corrosion behaviors influenced by Mo and Cu in 0.5 M aqueous HF acid solution at room temperature. Results indicate that both Mo and Cu play positive roles in improving the corrosion resistance. The enhanced corrosion performance by Cu addition is observed in all alloys while this is more obvious in the alloy with low Mo concentration. Moreover, 2 wt% Cu addition is found to not only reduce the critical Mo concentration for spontaneous passivation of alloy, but also alter the nature of the exposed surface with distinct declines of effective capacitance. Ni-30Co-16Cr-15Mo-2Cu alloy shows the best corrosion resistance among all alloys studied.

Cerium-based conversion coatings have emerged as promising green alternatives to the harmful chromium-based ones, but the mechanism of corrosive protection still remains a subject of academic and industrial research. This study focuses at small scale phenomena of corrosion inhibition imparted by ceria (CeO₂) to AA7075. Ceria nanoparticles were deposited from diluted and concentrated CeO₂ sols by immersion. A multi-analytical approach, combining Atomic Force microscopy (AFM), Scanning Kelvin Probe Force Microscopy, Glow Discharge Optical Emission Spectroscopy, open circuit potential and electrochemical impedance spectroscopy was employed. Deposition of ceria films led to deactivation of cathodic sites, i.e. decreased Volta potential difference, resulting in increased corrosion inhibition. In situ AFM real-time monitoring revealed that during exposure to NaCl electrolyte, the changes in size of deposited ceria aggregates occurred: nanoparticles disintegrated/desorbed and re-deposited at the coating surface. The process was found to be dynamic in nature. Small particles size and inherent reactivity are believed to accelerate this phenomenon. Due to the greater CeO₂ reservoir, this phenomenon was more pronounced with a thicker film, imparting longer term protection.

In this study, electrochemistry was combined with mass spectroscopy and surface analysis to investigate the selective dissolution of Cu and the consequent surface enrichment of Pt in Pt–Cu binary alloys. Two different compositions of Pt–50at% Cu (Pt–50Cu) and Pt–75at% Cu (Pt–75Cu) underwent potential cycling. Cu from both alloys was selectively dissolved, although trivial Pt dissolution occurred, causing the subsequent formation of a Pt-enriched layer on the alloys' surfaces. The morphology of the layer was quite different between the two alloys. The Pt-enriched layer formed on the Pt–50Cu surface was extremely thin and compact, further suppressing Cu dissolution from the alloy in the later stage of potential cycling. The Pt-enriched layer formed on the Pt–75Cu surface contained numerous pits, mainly because a lot of Cu was dissolved from Pt–75Cu during potential cycling. Thus, Cu continued to dissolve from the bottom of the pits at the later stage, causing the thickness of the Pt-enriched layer to gradually grow with an increase in the cycle number. The correlation between Pt and Cu dissolution and surface morphological changes of Pt–Cu alloys was discussed.

Melatonin (MEL), as a new accelerating agent, is applied for phosphate chemical conversion coating on mild steel. Scanning electron microscopy has been applied to observe the morphology of phosphating crystals, showing that the incorporation of MEL results in more dense and uniform phosphate coatings. Electrochemical impedance spectroscopy and potentiodynamic polarization are performed to evaluate corrosion resistance of phosphate coatings. The results show that the corrosion rate of blank phosphate coating is 5.64 mpy, while the corrosion rate of phosphate coating accelerated with 1.25 g l⁻¹ MEL is reduced to 0.04 mpy. In addition, the dry friction test shows that friction coefficient of the phosphate coatings with the introduction of MEL is decreased to 0.3 compared to 0.6 of the blank one, proving that MEL also reduces the friction resistance of phosphate coatings along with improved corrosion resistance.

Pitting corrosion resistance and passive films of Fe_balance-18Cr-12Ni-1.5Mn-0.07C-based alloys containing 0.19, 0.78, and 1.76 wt% B were investigated through potentiodynamic polarization tests and scanning transmission electron microscopy—energy dispersive spectroscopy analyses, respectively, in NaCl and H₃BO₃ solutions. The addition of B lowered the resistance to pitting corrosion due to the increase in the volume fraction of (Cr,Fe)₂B. For the alloy with a large volume fraction of (Cr,Fe)₂B, the resistance to pitting corrosion in the NaCl solution was improved due to the addition of H₃BO₃, as H₃BO₃ assisted passivation and raised the Cr fraction in the passive film.

Linear sweep voltammetry (LSV) test parameters in alkaline medium were optimized by Doehlert matrix design in order to quantify the deleterious phases in a superduplex stainless steel UNS S32750. The microstructural analysis was performed, in several heat treated specimens, by Light Optical (LOM) and Scanning Electron (SEM) Microscopies and correlated with the electrochemical tests. In these tests, optimized parameters were obtained for tests in aqueous solutions of KOH. The concentration of 3.55 mol l⁻¹, scan rate of 3.42 mV s⁻¹ and initial potential of −0.818 V, showed a good correlation between the deleterious phases precipitated and charge density values. Differently from LOM characterization, chi and sigma deleterious phases can be distinguished by LSV optimized test. Finally, this test can be a non-destructive powerful tool of quality control to detect embrittlement and corrosion resistance decay that commonly affected this stainless steel as consequence of inadequate fabrication processes.

Electrochemical Impedance Spectroscopy was utilized to investigate the corrosion behavior of carbon steel in a salt spray test (SST) chamber. The salt spray was applied using 5% NaCl solution at 35 °C. A two-electrode cell comprising a pair of identical carbon steel electrodes embedded in epoxy resin were placed at six different angles (0°, 30°, 45°, 60°, 75°, and 90°) to the horizontal in the chamber. The corrosion rate (CR) of the carbon steel samples and the thickness of the solution film formed on the sample surface were evaluated from the impedances at low and high frequencies, respectively. The CR of carbon steel fixed horizontally (0°) exhibited a low value compared with that fixed at other angles. When the angle changed from 30 to 75°, the solution film thickness decreased greatly, but there was no significant difference in the CR. The CR of carbon steel under the employed SST conditions was more than five times higher than that in a bulk 5% NaCl solution under natural convection. The corrosion mechanism of carbon steel in the SST chamber is also discussed.

The corrosion resistance of a heat-treated Ti–6Al–4 V alloy fabricated using the additive manufacturing (AM) method was investigated through a series of electrochemical techniques, including potentiodynamic polarization, electrochemical impedance spectroscopy, and critical pitting temperature measurements, in an effort to improve the corrosion resistance of AM Ti–6Al–4 V subject to different stages of heat treatment. During this process, we reported that the corrosion resistance of the AM Ti–6Al–4 V alloy significantly reduced, which we attributed to both preexisting α' phases and newly emerging precipitates. After heat treatment at 650 °C and 750 °C, the corrosion resistance of AM Ti–6Al–4 V worsened further after cooling compared to the original as-received sample because of the existence of the α' phase (without decomposition) and precipitates. However, at 850 °C and 1000 °C, the heat-treated samples demonstrated much better corrosion resistance compared to the as-received sample, possibly because of the complete transformation of the α' phase into the α phase and the evolution of a β phase. Based on these experimental results, we believe that adequate heat treatments such as rapid cooling illustrate added advantages for the enhanced corrosion resistance of AM Ti–6Al–4 V alloys.

Aqueous corrosion, atmospheric corrosion, and ionic liquid dissolution studies were performed on commercial alloys AZ31B, AM60, and AZ91D and compared with previously reported results for single-phase binary Mg–Al alloys containing similar Al concentrations (αMg-2 at% Al, αMg-5 at% Al, and Mg-8 at% Al). Polarization studies in 0.6 M NaCl were used to characterize the aqueous free corrosion behavior during 20-h free immersion. Accelerated corrosion testing was performed using a rotating-disk electrode which revealed the evolution of an Al-rich mud-cracking and platelet morphology. Atmospheric droplet testing showed rapid pH increases that depended on the Al concentration in the alloy. Time-dependent contact angle measurements showed that the degree of droplet wetting increased during free corrosion by ∼50° over 20 h in 0.6 M NaCl. Ionic liquid dissolution studies in 1:2 M choline chloride:urea deep eutectic solvent were performed in order to examine the current-voltage behavior of these alloys in the absence of water and hydrogen reduction. The results of these studies revealed the formation of nanowire corrosion morphologies within a honeycomb lattice structure which we attribute to selective dissolution of Mg via a two-dimensional step-flow process.

The composition and structure of the native and passive oxide films formed on 316 L stainless steel have been studied in situ by ToF-SIMS. High temperature re-oxidation experiments in isotopic ¹⁸O₂ gas have also been done to assess the ion transport mechanisms in the native and passive oxide films. Duplex oxides with an inner Cr rich layer and an outer layer rich in Fe and Mo oxide have been observed on native and passive oxide films. Exposure of the oxide films to isotopic ¹⁸O₂ tracer at 300 °C reveals that the outward cationic diffusion governs the inner oxide growth. The outer Mo-rich layer prevents the continued transport of Cr to the outermost surface. The passive film, due to its composition and structure, exhibits a markedly lower oxidation rate compared to native oxide films.

Electrochemical reduction of Sr²⁺ and Ba²⁺ into liquid Bi was investigated in dilute concentrations of SrCl₂/BaCl₂ (0‒5 mol%) in LiCl-KCl electrolytes at 500 °C to ascertain the limit of liquid Bi electrodes for alkaline-earth recovery. Analysis of the electrodes after constant current electrolysis to the specific charge of 270 C g⁻¹ showed Sr²⁺ ions consuming 29% of charge at 5 mol% before dropping to 8%‒10% of the total charge at 0.45‒0.72 mol% SrCl₂. Ba²⁺ ions consumed 54% at 5 mol% BaCl₂ before decreasing to 22%‒24% at 0.42‒0.89 mol% BaCl₂; substantial co-deposition of Li was observed in all chemistries, consuming up to 53% of charge. Considering only 1% of the total charge was consumed for depositing Ba²⁺ and Sr²⁺ ions in ∼0.1 mol% SrCl₂/BaCl₂ electrolyte, the lower recovery limit of Bi for alkaline-earth elements is suggested to be at ∼0.4 mol% SrCl₂/BaCl₂ to achieve appreciable deposition of alkaline-earths (>1.5 mol% Ba/Sr in liquid Bi). The overpotentials of liquid Bi at 5 mol% of SrCl₂/BaCl₂ were evaluated by electrochemical impedance spectroscopy. The co-deposition of Sr and Li exhibited the largest increase in charge transfer resistances implying sluggish charge transfer kinetics whereas the co-deposition of Ba and Li exhibited a large increase in mass transport resistances due to the slow diffusion of Ba²⁺ ions in the electrolyte.

To improve the deposition accuracy and surface quality of the deposited micro-features, a novel compressed air-film encircling Jet ECD was proposed. In the proposed Jet ECD, a high-speed compressed air-film is coaxially encircling the impinging electrolytic jet. Numerical model describing the coupled field of electric field and flow field was established, and some auxiliary observations and measurement experiments were conducted to investigate the distribution characteristics of electric field and hydrodynamics characteristics in the concerned regions as well as the change of the electrolyte jet diameter. And the effect of air-film formation parameters and hydrodynamic parameters of the electrolyte jet on the electrodeposition behaviors during forming patterns and high aspect ratio micro-features were studied. Deposition accuracy and surface quality of the microstructures fabricated by the compressed air-film encircling Jet ECD were evaluated. It was demonstrated that, compared with the traditional Jet ECD, the proposed Jet ECD has a higher deposition accuracy and faster deposition rate (up to 1 μm s⁻¹) as well as better surface quality. In addition, the newly developed Jet ECD has an admirable additive manufacturing ability and a 370 ± 3 μm-diameter smooth column with the aspect ratio of about 20 was successfully manufactured.

A review of the existing methods for producing aluminum master alloys with silicon, zirconium, scandium and boron are given. Basic parameters, advantages and disadvantages of the existing methods are analyzed, indicating the need to develop new more energy-efficient technologies. The prospects of obtaining aluminum master alloys in the electrolysis of melts based on the KF-NaF-AlF₃-Al₂O₃-MeO (MeO = SiO_2, ZrO₂, Sc₂O₃, and B₂O₃) system are considered. For this purpose, the results of physical and chemical measurements in these melts are presented, including data on the solubility of Al₂O₃, SiO_2, ZrO₂, Sc₂O₃, and B₂O₃ oxides in KF-NaF-AlF₃ melts, data on the effect of oxide additives on the liquidus temperature of studied melts, as well as data on the kinetics of electrowinning of aluminum and alloying element from KF-AlF₃-Al₂O₃-MeO melts. Based on the measurements, the parameters were selected and electrolysis tests were carried out for obtaining aluminum master alloys with silicon, zirconium, scandium, and boron from its oxides. The composition and structure of the obtained master alloys were studied.

The influence of the second coordination sphere complexes on the roughness of niobium and tantalum coatings was studied. It was found that the discharge potential of niobium oxofluoride complexes has a more positive potential than fluoride ones in the NaCl-KCl-NaF (10 wt%)-K₂NbF₇ melt. For the СsCl-CsF (10 wt%)-CsNbF₆ molten system the inversion of potentials corresponding to discharge of oxofluoride and fluoride complexes was observed. Due to micropassivation by oxygen impurities as niobium suboxides and oxygen-niobium solid solution the coating roughness in the NaCl-KCl-NaF (10 wt%)-K₂NbF₇ (8 wt%) melt diminishes in comparison with СsCl-CsF (10 wt%)-CsNbF₆ (8 wt%) melt. In molten salts NaCl-KCl-NaF (10 wt%)-K₂TaF₇ and СsCl-CsF (10 wt%)-CsTaF₆ tantalum oxofluoride complexes are discharged at more negative potentials than fluoride ones and changes in the composition of the second coordination sphere from sodium to cesium led to a lower level of roughness. For melts containing in the second coordination sphere cesium cations, the roughness of the tantalum coatings was less than that of niobium due to the greater strength of the fluoride complexes of tantalum. It was found that pulsed current electrolysis for deposition of niobium and tantalum coatings has significant advantages in comparison with direct current electrolysis.

We synthesize new triethylene glycol-based levelers containing quaternary ammonium groups with different terminal functional groups (allyl, propyl, benzyl, and naphthylmethyl) to investigate the structure-property relationship of the levelers. Though all the synthesized levelers indicate the convection-dependent adsorption behavior through the onset potential in linear sweep voltammetry, the inhibition strength depends considerably on the functional groups. The exchange current density of 0.40 mA cm⁻² for Cu reduction in the naphthylmethyl case is the lowest among our levelers, owing to the π-cloud interactions of a large aromatic naphthylmethyl group with Cu. The naphthylmethyl leveler maintains the inhibition layer that is not deactivated even by the addition of bis(3-sulfopropyl) disulfide (SPS) unlike the other functional groups in chronopotentiometry. The complex inhibition layer composed of the leveler and a suppressor is retained, displaying a high potential difference of –157 mV between 100 and 1000 rpm. By using three-additives containing the naphthylmethyl leveler, microvias show the filling ratio of 100% within 50 min and a thin top thickness of only about 15 μm. These results provide the effectiveness of the naphthylmethyl terminal functional group for enhancing the inhibition of leveler and can help the new design of electroplating additives.

In this paper, nanostructured Co₂FeGa Heusler alloy films with L2₁, B2 and A2-type cubic structures were synthesized using a low-cost electrodeposition method for the first time. The crystal structure of the deposited Co₂FeGa is dependent on pH of electrolyte. Magnetic measurements show that the saturation magnetization and coercivity of the samples have a positive correlation with the pH of electrolyte. The relationships of the microstructure and magnetic properties of the samples were discussed. The electrodeposited Co₂FeGa films with a high magnetization and low coercivity in our work will be of particular interest in industrial and technology applications.

A liquid metal electrochemically deposited in CaCl₂ or its chloride melts serves as an effective reductant for active metal oxides. Although a very low oxygen concentration can be achieved at a considerably high electrolysis efficiency, the existence of small amount of water impurity in molten chlorides, which is very difficult to detect, causes low electrolysis efficiency. In this study, to clarify the morphological and thermal characteristics of a cathodic electrode in a slightly hygroscopic LiCl–KCl–CaCl₂ melt, we simultaneously performed electrochemical measurements and thermal measurements using an ultrafine thermocouple inserted inside a Mo electrode (i.d. 1.57 mm). Concomitantly, changes in the electrode interface were recorded at 500-μs intervals using a synchronized high-speed digital camera. Despite the small amount of water included in the system, the measured heat absorption was much smaller than thermodynamically predicted, which suggested that the generated hydrogen decreased the purity of the liquid alloy electrodeposited on the cathode surface possibly through hydride formation. By using the synchronized thermal measurement, it was possible to trace the change in the electrodeposition pattern of impurity water quickly and sensitively, which was difficult to determine in only the electrochemical potential-current response.

Electrochemical reduction of iron oxides into zero-valent iron (ZVI, Fe⁰) is a promising alternative to the traditional methods used for iron production. The electrochemical deposition of Fe⁰ from hematite and hematite-based Fe_2−xAl_xO₃ ceramic in alkaline suspensions (10 M of NaOH) was assessed at relatively low temperature (90 °C). Ceramic compositions aimed to mimic the main components of red mud waste from the alumina refining industry for iron valorisation purposes. The impact of aluminium content on the electroreduction and microstructure of the deposited Fe⁰ films was demonstrated and discussed. Trapping and following the leaching of the aluminium species during deposition causes drastic morphological changes and induces significant porosity. Faradaic efficiencies of the reduction to Fe⁰ were found to decrease from 70% to 32% for Fe₂O₃ and Fe_1.4Al_0.6O₃, respectively. The results highlight possible effects imposed by aluminium presence during Fe⁰ electrodeposition for future iron recycling from, for example, red mud or other aluminium containing wastes by electrowinning in alkaline conditions.

Carbon nanotube (CNT)/Cu composite yarns were formed via a single-step electrodeposition process. A twisted CNT yarn composed of multiwalled CNTs (MWCNTs) was used. Copper was directly electrodeposited onto the CNT yarn under galvanostatic conditions using copper sulfate baths with and without additives. Four additives (polyethylene glycol (PEG), chloride anion (Cl⁻), bis(3-sulfopropyl)disulfide (SPS), and Janus green B (JGB)) that are well known as "via-filling additives" were used together. The surface and cross-sectional microstructures of the copper-deposited CNT yarns were analyzed. Copper was electrodeposited only onto the surface of the CNT yarn from the bath without additives, resulting in a copper-coated CNT yarn. By contrast, copper was deposited not only onto the surface but also into the interior of the CNT yarn from the bath with the additives. The amount of copper deposited into the CNT yarn tended to increase with increasing PEG and Cl⁻ concentrations. The current density also affected the size and location of the deposited copper particles. When the electrodeposition conditions were optimized, copper was relatively homogeneously deposited into the interior of the CNT yarn, resulting in a CNT/Cu composite yarn.

Base metal electrodeposition is inevitably accompanied by parasitic hydrogen evolution. This results in a less-than-unity Faradaic efficiency (FE_m) of metal deposition that is known to depend on many factors like the applied current density, the composition (primarily, the metal ion concentration and the pH) of the depositing bath, and the rate of convection. Analysing how FE_m values depend on the current density j under well-defined transport conditions (e.g., by the use of rotating disk electrodes) became an integral part of industrial approaches to the screening of bath compositions applied for base metal electroplating. Yet FE_m(j) curves are still not very well understood, and most studies content themselves with their mere qualitative analysis, reaching no conclusions as to the mechanisms of the underlying reactions. We attempt to fill this gap by creating a simple model for FE_m(j) curves based on first principles. The presented model can very well be fitted to experimental data obtained for the electrodeposition of nickel and of cobalt, and it yields a consistent set of kinetic and transport parameters over a broad range of pH, rotation rates and current densities. The presented model thus paves the way towards a knowledge-driven benchmarking strategy of base metal electroplating baths.

In this work, the cyclic voltammetry (CV) was used to investigate the redox process of Cr(III) on glassy carbon electrode (GC) in deep eutectic solvents (DESs), prepared using choline chloride (ChCl) and ethylene glycol (EG). The anode and cathode branches of the CV curve meant the process of deposition/dissolution equilibrium of trivalent chromium. The equilibrium potential (E_eq) of Cr(III)/Cr(0) was −0.964 V (vs Ag QRE). The analysis of the potentiostatic current density transient (chronoamperometry (CA)) results showed that the electrodeposition process of Cr(III) involved multiple processes, mainly j_ad, j_3D and j_WR. By calculating the amount of charge (Q_ad%, Q_3D%, and Q_WR%) in each process, it can be found that the contribution rate could be controlled by the potential to increase Q_3D%. The kinetic parameters of Cr nucleation/growth rate were determined from the standard model of 3D nucleation of diffusion-control, such as nucleation rate (A), active centre number density (N₀), and diffusion coefficient (D). The ln(A) and η were used to calculate the nucleated Gibbs free energy (Δ∼G(n_c)), the critical core size (n_c), the current exchange density (j⁰), the transfer coefficient (α), and the surface tension (σ). The chromium coating was constituted by particles of Cr(0), Cr₂O₃ and Cr(OH)₃.

Zirconium oxide (ZrO_x) films were successfully prepared on a transparent conducting substrate (fluorine-doped tin oxide) by galvanostatic cathodic electrolysis of a solution containing ammonium hexafluorozirconate (AFZ) and ammonium nitrate at 323 K. The morphology of the film evidently changed based on the initial concentration of AFZ in the solutions. The film prepared at comparably higher AFZ concentration exhibited aggregates of sword-type leaf-like units tens of micrometers in size in the longitudinal direction, radially growing and dividing into secondary structure. On the other hand, normal planar films of a micrometer order were deposited at a lower concentration of the AFZ solution. The films were classified as zirconium oxyfluorides (Zr–O–F) from the atomic concentration ratios of Zr, O, and F determined by X-ray fluorescent spectrometry analysis. Regardless of the initial AFZ concentrations, the crystallographic structures of the films were converted to monoclinic crystalline ZrO₂ (baddeleyite) by the calcination at 773 K. The leaf shape of the film obtained in the solution of higher AFZ concentration was maintained following the calcination process, indicating the development of a 3D ZrO₂ film. The present work evaluated the chemical character of the films and gave deeper insight into the growth mechanism of these remarkable materials.

In this work, a 3D nanoflower-like Ni@FeCo₂O₄@Yb-Ni(OH)₂ composite was prepared via a facile liquid phase chemical deposition and electrochemical deposition method. The as-synthesized Ni@FeCo₂O₄@Yb-Ni(OH)₂ composites have a large specific surface area because of the developed nanoflower morphology, which creates good contact between the material and electrolyte. A high specific capacitance of 11.04 F·cm⁻² is reached at a current density of 4 mA·cm⁻². More importantly, the asymmetric supercapacitor assembled by using the as-synthesized Ni@FeCo₂O₄@Yb-Ni(OH)₂ composites as the positive electrode and activated carbon as the negative electrode exhibits a high energy density of 36.86 Wh·kg⁻¹, a power density of 1.2 kW·kg⁻¹ and excellent cycling stability (97.8% capacitance retention).

It is very simple and convenient using the commercial chloroauric acid instead of sodium gold sulfite as the main salt in the Au(I) sulfite electrodeposition bath. In this paper, the effects of chloride ions on cyanide-free Au(I) electrodeposition in the gold sulfite bath are carefully investigated. Both UV–vis absorption spectroscopy and visual inspection reveal that chloride ions suppress the disproportionation reaction of Au(I) and improve the bath stability. Cyclic voltammetry indicates that chloride ions promote the cathodic reduction of Au(I). EC-SERS spectra elucidate that in the sodium sulfite solution, SO₃²⁻ ions firstly adsorb on the gold electrode, then experience a structural transformation (SO₃²⁻ → S₂O₅²⁻), and last electroreduce to S₂O₃²⁻ ions (S₂O₅²⁻ → S₂O₃²⁻) as the potential shifts negatively. In the gold sulfite electrolytes, the cathodic reduction of Au(I) and chloride ions hinder the reduction of S₂O₅²⁻ ions. The gold coatings obtained from the gold sulfite electrolyte containing chloride ions present in fine and pure grains without chlorine and sulfur inclusion.

Highly efficient and cost-efficient catalysts for overall water splitting are essential for practical applications; however, it is challenging to manufacture such catalysts. Herein, we report the fabrication of a cost-effective electrocatalyst consisting of FeCoNiP alloy nanoparticles that are integrated on vertically aligned phosphorus-doped single-walled carbon nanotubes (VPSWCNTs) on Au electrode (FeCoNiP/VPSWCNTs/Au). The catalyst exhibited excellent catalytic performance in 1.0 M KOH for hydrogen evolution reaction (HER) (overpotential of 147 mV and Tafel slope of 64 mV dec⁻¹) and oxygen evolution reaction (OER) (overpotential of 280 mV and Tafel slope of 43 mV dec⁻¹) with the current density of 10 mA cm⁻². FeCoNiP/VPSWCNTs/Au exhibited good stability and activity for at least 10 h. These results indicate that FeCoNiP/VPSWCNTs/Au can be used as a cost-effective and earth-abundant non-noble-metal efficient catalyst for overall water splitting.

The kinetics of the dissolution and deposition of aluminum from a first generation ionic liquid consisting of AlCl₃/1-ethyl-3-methylimidazolium chloride (molar ratio 2:1) was studied. Electrochemical impedance spectroscopy shows that the double layer capacitance and the charge–transfer resistance depend on the state of the electrode surface. The impedance spectra are strongly influenced by mass transport. The rate–determining step of the aluminum deposition, as determined from the cathodic Tafel slope evaluated from current step experiments, was found to be either a chemical step, releasing the complexing agent chloride, while aluminum is in the divalent oxidation state (AlCl₃⁻ → AlCl₂ + Cl⁻) or an electron transfer from the divalent to the monovalent aluminum occurring twice for the overall reaction to occur once (Al²⁺ + e⁻ → Al⁺). The rate–determining step for aluminum dissolution was found to be the transfer of an electron from elemental aluminum to the monovalent oxidation state (Al⁰ → Al⁺ + e⁻). A linear slope in the low cathodic overpotential region of the Tafel plot suggests a change in the cathodic rate–determining step. The Tafel slope indicates a chemical step, releasing the complexing agent chloride, after the last electron transfer (AlCl⁻ → Al⁰ + Cl⁻) to be the rate–determining step for overpotentials below 50 mV. Density functional theory calculations support the proposed reduction and oxidation mechanisms.

Ion transport membrane (ITM) technology is a key perspective for efficient oxygen separation. At the present time, semi-industrial modules based on ceramic ITMs produce oxygen of 98.9%–99.9% purity. In order to improve the oxygen purity, we suggest using newly developed liquid-oxide ITMs with a record oxygen selectivity (O₂/N₂ > 10⁵). Along with the highest oxygen selectivity, these membranes exhibit competitive oxygen permeability and could be successfully used for ultrahigh purity oxygen separation. Here we review the advantages and future prospects of liquid-oxide ITMs for a potentially disruptive technology which will provide improvement in oxygen purity and energy efficiency.

The objective of this work is to advance the mechanistic understanding of cathodic electrocoating. These efforts focus on the initial processes responsible for deposition, which are examined through direct experimentation and simulation. Electrocoating is a global industrial process providing a corrosion-resistant, base-paint layer to automobile bodies. Presently, empirical models are used to model coating thickness; these models tend to overpredict deposition in occluded areas. Convection is implemented to study electrochemical mechanisms at the surface of the coated part. The impact of surface H₂ bubbles and early e-coat deposition on the local current density is studied using current distribution simulations. Results show an increase in current density locally around surface H₂ bubbles and early e-coat deposition influences film growth. When surface H₂ bubbles are displaced by convection before sufficient e-coat is deposited, deposition is slowed under lower local current density. However, when the e-coat covers sufficient surface area, and convection is then applied, the induction period is unaffected, implying the early deposition is sufficient to keep the local current density high enough to drive deposition. These results provide an increased understanding of fundamental processes responsible for e-coat deposition, which is the foundation needed for advanced physics-based models of the electrocoating process.

Alumina-containing waste can potentially be used to produce a coarse Al–Si alloy by carbothermal reduction and subsequent aluminum metal extraction by soluble anode electrolysis. However, metal impurities in the alloy have important effects on the product purity. In this study, anodic dissolution of the coarse Al–Si alloy and cathodic electrochemical reduction of metal impurity ions in the electrolyte were investigated. The phases, element distributions, and compositions of the anode, electrolyte, and products were investigated by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma atomic emission spectrometry. When using an aluminum wire of diameter 2 mm as reference electrode, the order of anodic metal dissolution is Mg > Ca > Al > Fe > Si > Ti > Mn, and that of metal impurity ion reduction in the electrolyte is Fe > Si > Al > Mg > Ca. Mg and Ca dissolve into the electrolyte before aluminum does, but they have little effect on the product purity because of their high decomposition voltages. Fe and Si in the alloy anode begin to dissolve at electrode potentials of 0.4 and 0.7 V, respectively. If keeping the electrode potential lower than 0.3 V, the Al purity reaches 99.9%.

Redox flow batteries (RFBs) are attractive energy storage solutions for the grid, the simulation of which enables system and material optimization. In this article, we introduce tailored numerical schemes to model coupling between the transport of dissolved species, electrons, and fluid with redox reaction kinetics within RFBs in a robust way. The macro-scale transport of species (including advection, migration, and hydrodynamic dispersion) is coupled with the volume-averaged pore-scale processes of reaction kinetics, and mass transport, while the Poisson equation is used to model Donnan exclusion across ion exchange membranes that limit capacity fade due to the crossover of redox-active species. The governing equations are discretized using the finite volume method with a Newton-Raphson iteration scheme to resolve non-linearity. We introduce several numerical schemes to increase solver robustness, including reaction rate damping and logarithmic transform of concentration fields. Based on fixed-point iteration convergence criteria we also show that the mechanistic Marcus-Hush-Chidsey (MHC) redox kinetics model can tolerate larger time steps than the empirical Butler-Volmer (BV) kinetics model. The numerical schemes presented in this article can also find application in other electrochemical systems, including desalination devices, fuel cells, and electrodialysis.

Straight nanowires fabricated from single-layer porous anodic alumina (PAA) templates are known to be mechanically weak. To provide additional support, nanowires can be fabricated on multilayered PAA templates. In this work, Cu and Ni nanowires were fabricated using single-, double-, and three-layer PAA templates by pulse electrochemical deposition (PECD). The templates were made by anodizing Al-1 wt% Si and Al-0.5 wt% Cu thin films under different conditions. The morphologies of the PAA templates and fabricated nanowires were examined with scanning electron microscopy. The length of the nanowires was 3 μm, while the diameters ranged from 50 to 70 nm. The nanowires fabricated from a double-layered template (Al-0.5 wt% Cu/Al-1 wt% Si) were mechanically stronger with larger surface areas than those fabricated from an anodized Al-1 wt% Si template. The nanowires formed within the anodized Al-1 wt% Si layer had tree-like branches, while vertical nanowires with horizontal anchors were formed in the anodized Al-0.5 wt% Cu layer. The results also indicated that the volume expansion of the PAA template was controlled by depositing a Al-0.5 wt% Cu layer below the Al-1 wt% Si film. The Ni nanowires can be used as a platform for hydrogen production and in other technological applications.

In the present study, we investigated the effect of an anode temperature on current transient process during porous anodic alumina growth and morphology of the anodic layers. Alumina films were formed in a 0.4 M oxalic acid at a constant voltage mode and electrolyte temperature. The temperature of the Al anode was controlled by thermoelectric Peltier element and varied in the range of 5 °C–60 °C. Surface morphology of both sides of anodic films and their cross-sections were analyzed by scanning electron microscopy (SEM) with subsequent statistical analysis of the SEM images by ImageJ software. It was found that when anode temperature was increased from 5 °С to 50 °С the pores diameter and interpore distance has not changed, but the porous structure became more ordered. According to these results, the rate of chemical dissolution of the barrier layer and pore walls did not depend on the anode temperature. At the anode temperature of 60 °С, pores diameter has increased 1.7 times and there was a distortion of the ordering of porous cells. It was concluded that the temperature difference between the aluminum substrate and electrolyte is an important parameter affecting the formation of ordered structure of nanoporous anodic alumina.

Electrochemical degradation of Acid Yellow 3 dye (AY3) in aqueous solution was investigated over a novel Ti/nanoSnO₂-α-Fe₂O3 electrode ssuccessfully fabricated by the cathodic electrophoretic deposition method. The surface morphology, elemental analysis, crystalline structure, and electrochemical properties of as-prepared nanoSnO₂-α-Fe₂O₃ films on titanium substrate surface were characterized by field emission scanning electron microscopy (FE-SEM) with an X-ray spectrometer attached, X-ray diffraction (XRD), linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chrono-potentiometry (CP). The r esults showed that, compared to the traditional nanoSnO₂ electrode, the novel Ti/nanoSnO₂-α-Fe₂O₃ electrode with a porous morphology and without voids or cracks on the surface possessed higher electro-catalytic activity and electrochemical stability. To obtain maximum dye removal and to determine the relationship between important operating variables, pH, current density, electrolysis time, and electrolyte concentration were selected for the batch experiments as independent variables in a central composite design (CCD). In the first run, color removal efficiency was 92.73% for the fresh electrode, and 88.40% after 6 consecutive cycles of use under optimized conditions. These results presented here prove that the Ti/nanoSnO₂-α-Fe₂O₃ electrode has good electro-catalytic performance and a great potential for efficient degradation of organic pollutants.

The Mn-doped Ni(OH)₂ nanostructures were obtained by a simple ion-exchange hydrothermal method. The as-prepared materials were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDXS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) for their morphological, composition and structural properties. As a material for modified electrodes, electrochemical tests demonstrate that the methanol oxidation peak current density of Mn-doped Ni(OH)₂ nanostructures reached 14.18 mA cm⁻² at 0.596 V (vs Ag/AgCl) in NaOH electrolyte. Similarly, the Mn-doped Ni(OH)₂ nanostructures also maintained good electrocatalytic stability during the term of 36,000 s. The improvement of electrochemical performance is related to the introduction of Mn element in Ni(OH)₂. It may promote Ni in the Mn-doped Ni(OH)₂ nanostructures to carry the lower electron density and the higher oxidation state which may be responsible for the better performance toward methanol oxidation.

Transition metal and nitrogen co-doped carbon-based nanomaterial has been used as non-precious metal catalyst for oxygen reduction reaction (ORR). In this work, bamboo-like carbon nanotubes structured FeCo/N/C electrocatalyst is proved to show much enhanced performance compared with Co/N/C. MIL-53 (Fe) is used as iron source, MIL-53 (Co) is used as cobalt source and ZIF-8 as carbon source. The ball-milling procedure plays a significant role for the distribution of Fe and Co component and the formation of carbon nanotubes, which is believed to enhance the catalytic performance due to abundant electrocatalytic active sites and efficient mass transfer. The as prepared sample obtained by optimized preparation conditions exhibits outstanding ORR activity in acid solution with an onset potential of 0.96 V vs RHE (reversible hydrogen electrode), half-wave potential of 0.78 V, and a current density of 0.575 m A cm⁻² at 0.7 V in a H₂-O₂ fuel cell test, which provides an ideal viewpoint to develop highly efficient catalyst for the oxygen reduction reaction. The high ORR performance could be attributed to the synergistic effect between Fe and Co and the high conductivity and mass transfer of the carbon nanotube.

To predict the novel poly(benzimidazole):poly(acrylic acid) (PBI:PAA) blend membranes proton conductivity, an ionic conductivity equation combined with thermodynamic model is proposed where different proton transport mechanisms including Grotthuss, vehicle and surface hopping mechanisms are considered in calculations. Based on the PAA titration behavior, by increasing the number-average molecular weight (${\bar{M}}_{n}$), apparent acidity of PAA decreases. Hence, to calculate the concentration of protons involved in different mechanisms, a new modification in the predictive model is suggested by considering acidity and its relation with ${\bar{M}}_{n}.$ Effect of temperature, PAA molar ratio and ${\bar{M}}_{n}$ on the membranes proton conductivity is investigated theoretically and compared with experimental data. The conductivity of membranes is increased by increasing the ${\bar{M}}_{n}$ and molar ratio of PAA where the highest proton conductivity is attributed to the membrane with PAA of ${\bar{M}}_{n}$ = 10⁵ g · mol⁻¹ and molar ratio of PBI:PAA = 1:4. The experimental proton conductivity and predicted results show a good agreement in comparison to the previous models based on Nernst–Einstein equation, indicating that acidic behavior, which is usually omitted in theoretical models, has an important effect on the total proton conductivity of PBI:Polyacid membranes, especially at higher temperatures.

Temperature gradients can move water within the porous media of a polymer electrolyte fuel cell through phase-change-induced (PCI) flow. It is critical to understand PCI flow so that control and distribution of water within a fuel cell can be accomplished. This work investigates the role of architecture, specifically anode land width, on overall cell water content and distribution in the through-plane direction. A specially-designed 4.8 cm² fuel cell with precise thermal boundary conditions was imaged with neutrons using two different anode flow field configurations. A new, non-dimensional thermal transport number was developed which quantifies the relative influence of PCI flow on cell water transport. It was found that anode lands larger than the cathode lands cause large thermal gradients that instigate net water flux from the cathode to the anode. An asymmetric configuration with larger anode lands was found to have large changes in water content that were strongly sensitive to cell operating conditions. The thermal transport number developed here enables deduction of the net flux condition based on operating conditions and architecture. This approach enables design of high-performance systems with balanced water management.

Improvements in synchrotron based operando X-ray tomographic microscopy (XTM) of polymer electrolyte fuel cells (PEFCs) have paved the way for 4D imaging studies of the water distribution in the gas diffusion layer (GDL). In order to capture the full water dynamics in 4D, a decrease of the scan time towards 0.1 s is aspired, posing significant challenges in image processing for quantitative water detection. In this work, ex situ and in situ X-ray tomographic microscopy experiments were conducted to study the influence of imaging parameters and image denoising settings on image quality and water detectability in the GDL. The image quality is quantified for scan times between 50 ms and 12.8 s at the TOMCAT beamline of the Swiss Light Source. Denoising strategies for a broad range of image qualities were identified, which enable high in situ water detectability rate of 96% at a scan time of 1.6 s and 88% at subsecond scan time as short as 0.4 s. The presented methodology can be transferred to other PEFC or similar XTM imaging setups and image processing pipelines to verify their water detection capabilities.

An analytical model for resistance to oxygen transport in air electrodes containing carbon black supports with high surface area was developed by combining a Thiele modulus—effectiveness factor approach at the agglomerate scale (∼150 nm) with nanoscale diffusional resistance in carbon micropores/pits (∼5 nm). This paper extends an earlier model for transport resistance to platinum nanoparticles on low surface area carbon. Differences in transport resistances between catalyst layers with high and low surface area carbon blacks predicted by the model with reasonable geometric dimensions and physical properties are consistent with experimental observations.

Increased interest in liquid ammonia (NH₃) for hydrogen storage can be attributed to its lack of carbon, high energy density to volume and mass ratios (17.6 wt% hydrogen), a ubiquitous supply and distribution network, and lower cost. Recent progress in direct ammonia fuel cells for power generation, as well as ongoing work on the electrochemical synthesis of ammonia, motivate the need for fundamental investigations of aqueous ammonia interactions with electrode materials. Porous gas-diffusion media (GDM) play a large role in facilitating liquid, gas, and charge transport and are an inherent part of these technologies membrane electrode assemblies (MEA). This work characterizes how key wetting properties such as contact angle, advancing/receding contact angles, adhesion force, and breakthrough pressure are influenced by GDM wet-proofing, thickness, and structure. These properties are studied for aqueous ammonia solutions with 0, 10, 20, and 30 wt% NH₃. The higher concentrations of NH₃ along an electrode surface can lead to lower contact angles as surface tension is reduced. Wet-proofing with PTFE loadings up to 10 wt% increases hydrophobicity, while higher loadings have diminishing effects. The results are useful to those involved with modeling, design, construction, and optimization of these systems.

Water-vapor fed electrolysis, a simplified single-phase electrolyzer using a proton-exchange membrane electrode assembly, achieved >100 mA cm⁻² performance at <1.7 V, the best for water-vapor electrolysis to date, and was tested under various operating conditions (temperature and inlet relative humidity (RH)). To further probe the limitations of the electrolyzer, a mathematical model was used to identify the overpotentials, local water activity, water content values, and temperature within the cell at these various conditions. The major limitations within the water-vapor electrolyzer are caused by a decreased water content within the membrane phase, indicated by increased Ohmic and mass transport losses seen in applied voltage breakdowns. Further investigations show the water content (λ, mole of water/mole of sulfonic acid) can decrease from 13 at low current densities down to 6 at high current densities. Increasing the temperature or decreasing RH exacerbates this dry-out effect. Using our mathematical model, we show how these mass transport limitations can be alleviated by considering the role of water as both a reactant and a hydrating agent. We show that low cathode RH can be tolerated as long as the anode RH remains high, showing equivalent performance as symmetric RH feeds.

Fuel flexibility is a unique feature of solid oxide fuel cells (SOFCs), the instability of Ni-based cermet anodes in hydrocarbon fuels impede the advancement of low-temperature solid oxide fuel cells (LT-SOFCs). Here we demonstrate highly stable LT-SOFCs prepared by catalytically modifying the surface of a conductive ceramic oxide, SrFe_0.2Co_0.4Mo_0.4O₃ (SFCM), using Ni-GDC nanoparticles (<100 nm). The nano-sized Ni-GDC electrocatalysts, resulting from careful optimization of Ni-to-GDC ratio, and subsequent low-temperature calcination process, enhance the fuel oxidation kinetics and stability of SFCM anode significantly. An optimized Ni-to-GDC ratio of 1:10 on SFCM-supported SOFC delivered peak power density of 0.75, 0.65 and 0.36 W cm⁻² at 650 °C, 600 °C and 550 °C, respectively, in humidified H₂ and 0.62, 0.39 and 0.22 W cm⁻² at 650 °C, 600 °C and 550 °C, respectively, in CH₄/H₂ gas mixtures, nearly 4× higher than GDC as electrocatalyst. Remarkably, for the same Ni-to-GDC ratio, a stable cell voltage of 0.82 V is maintained over 200 h of operations (under current) at 600 °C in CH₄/H₂ gas mixtures.

Metal supported solid oxide fuel cell (MSC) technology has a significant potential for mobile applications, due to high electrical efficiencies, fuel flexibility, cheap materials, and mechanical robustness. The MSC concept in the current study relies on scalable, ceramic processing methodology. Two MSC generations with different anodes, one with a FeCr-ScYSZ-based anode backbone and one with a FeCr-titanate based anode backbone, both infiltrated with GDC and Ni electro catalysts, were tested using methane containing fuel. It was found that the internal reforming activity of the anodes is reduced as compared to state-of-the-art Ni-cermet anodes, due to the lower Ni content in the anodes of the MSCs. Still, power densities of ca. 0.22 W cm⁻² were obtained at 650 °C in a methane/steam fuel and long-term tests at medium to high fuel utilization were successfully demonstrated on the titanate based MSC.

In this paper, the bifunctional Ir cluster-decorated carbon Composite (Ir/C-1) electrocatalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are synthesized through simple in-situ growth of bimetallic Zn-Ir-MOF, followed by Zn reduction and evaporation for creating pore structure and uniform particle distribution. The prepared catalyst of Ir/C-1 with Ir cluster (d = 3 ± 0.1 nm) highly dispersed and closely attached to pore carbon through Ir–O–C bonds shows both excellent OER and HER performance. At a current density of 10 mA cm⁻², the catalyst shows overpotentials of only 50.4 mV for HER and 359 mV for OER in 0.5 M H₂SO₄, respectively, which are better than commercial Ir/C and Pt/C catalysts. Density functional theory (DFT) calculations further revealed that the exposure of Ir (110) in Ir/C-1 can facilitate the thermodynamic process of HER and OER. This paper also gives a detailed discussion about the enhancement mechanism. To validate the catalyst, a single electrolysis cell is assembled using the prepared Ir/C-1 catalyst as both the anode and cathode catalysts. The result shows that the cell only needs a cell voltage of 1.653 V to obtain a current density of 10 mA cm⁻², which is better than commercial Ir/C and Pt/C catalysts.

This paper describes and analyzes a system that tightly couples an electrochemical oxidation cell (EOC) with a protonic-conducting ceramic separation cell (PSC) to produce compressed pure hydrogen from a hydrocarbon feedstock and water. The EOC introduces oxygen through its membrane-electrode assembly (MEA) into the fuel chamber, enabling partial oxidation and reformation of the fuel to produce a hydrogen-rich mixture within the anode microstructure. At the same time, the EOC generates the electric power needed to drive the PSC for hydrogen separation and compression. On the other hand, removing hydrogen from the fuel stream by PSC can thermodynamically promote the catalytic conversion of the fuel stream. The concept leads to a self-contained integrated system, being independent of any external electrical power source, and being capable of producing pressurized hydrogen with potentially high energy-conversion efficiency.

Carbon-based electrodes in polymer electrolyte fuel cells (PEFCs) are prone to corrosion. Therefore, alternative "carbon-free" materials are required. Here, the use of a catalyst-coated porous metal support is proposed as a gas diffusion electrode. As a proof-of-concept, commercially available porous titanium sheets comprising sintered titanium fibers are chemically etched with NaOH, followed by heat treatment. This results in the formation of oxidized titanium nanostructures (such as nanosheets and nanotubes) at the surface. Subsequently, platinum decoration is performed via arc plasma deposition (APD). This porous composite structure is then attached to the membrane, and used as the gas diffusion electrode for PEFC membrane electrode assemblies (MEAs). This concept integrates the catalyst, catalyst support, gas diffusion layer, and current collector in a single structure, cutting down on the number of cell components and reducing total device thickness. The carbon-free nature of this integrated gas diffusion electrode is demonstrated to successfully avoid carbon corrosion during start-stop potential cycling over 60,000 potential cycles. However, further improvements in initial electrochemical activity are still required.

La_0.6Sr_0.4FeO_3−δ (LSF64) thin films are prepared by pulsed laser deposition (PLD) on yttria stabilized zirconia single crystals (YSZ) and characterized by electrochemical impedance spectroscopy (EIS) measurements before and after decoration with platinum nanoparticles. The platinum on the surface of LSF64 strongly accelerates the oxygen surface exchange kinetics. Especially at low oxygen partial pressures, the area-specific resistance (ASR) decreases by almost two orders of magnitude (e.g. in 0.25 mbar pO₂ from 125 Ωcm² to ca. 2 Ωcm² at 600 °C). While the pure LSF64 films exhibit severe degradation of the polarization resistance, Pt decorated films degrade much slower and show less scatter between individual samples. Surprisingly, faster oxygen incorporation (=lower polarization resistance) results for lower oxygen partial pressures, which indicates a severe mechanism change compared to undecorated LSF64 surfaces. The obtained results thus also reveal valuable information on the rate-determining step of oxygen exchange on LSF64 surfaces with and without platinum. On undecorated LSF64 surfaces oxygen dissociation is suggested to be rate limiting, while the Pt particles on LSF64 enable fast oxygen dissociation. Consequently, on Pt-decorated LSF64 electrodes a kind of job sharing mechanism results, with oxygen dissociation taking place on Pt and oxide ion formation and incorporation proceeding on the oxide.

In the process of developing an excellent active and stable Pt/C electrocatalyst for oxygen reduction reaction in fuel cells, metals are supported on heteroatom doped mesoporous carbon derived from natural resources. In this context, tamarind seeds are utilized to derive high surface area porous carbon for N heteroatom doping and followed by Pt deposition for oxygen reduction reaction (ORR) catalyst. The synthesis process involves optimization of temperature, N-content in the catalyst followed by Pt deposition by virtue of their electrochemical ORR behavior. The Pt/N-TC-1000 catalyst exhibits an outstanding activity and stability towards ORR even after 20,000 potential cycles. This is credited to the existence of N heteroatom in the matrix of carbon, where N acts as the linker between Pt and TC-1000 to avail the Pt-N and N-C chemical bonds in the Pt/N-TC-1000 catalyst. A peak power density of 800 mW cm⁻² is attained while evaluating the catalyst performance in a H₂-O₂ polymer electrolyte membrane fuel cell (PEMFC), at 70 °C and ambient pressure. The Pt/N-TC-1000 catalyst outpaces the commercial Pt/C with reference to fuel cell performance and stability. This is attributed to the high porous and corrosion resistive carbon support in combination with the strong Pt–N–C chemical bonds.

Proton exchange membrane fuel cells (PEMFC) require a gas diffusion layer (GDL) to aid in the transport of liquid fuel to the catalyst layer. In this work, direct modeling using the Lattice Boltzmann Method (LBM) was applied to X-ray CT scans of four different carbon gas diffusion layers to understand the mass transport properties through the samples. Three injection orientations were used to study local saturation levels, water evolution through the sample, and mass transport behavior at breakthrough conditions. The LBM, combined with computational fluid dynamic modeling techniques, can accurately predict liquid saturation at the macro and micro scale, which provides more insight into the mass transport phenomena through the GDL. The change of pore structure and orientation in both the in-plane and through-plane determines the path that liquid water must take, which could aid or impact PEMFC performance. The outcomes from this work will also benefit any research that needs knowledge of internal mass transport qualities of gas diffusion media.

An insoluble sulfonated polyphosphazene (SPOP) with high degree of sulfonation is synthesized and used as the proton conductor in polybenzimidazole (PBI) high-temperature proton exchange membrane. Polyfunctional triglycidyl isocyanurate (TGIC) is used as covalent cross-linking agent to obtain a high proton conductivity at low cross-linking degrees. The composite membrane is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). SPOP has good compatibility with mPBI-TGIC, leading to uniform dispersion in the obtained membranes with neither phase separation nor agglomeration. As a highly efficient cross-linking agent, TGIC not only makes the composite membrane have good mechanical properties, thermal stability, anti-swelling and anti-oxidation properties at low cross-linking degrees, but also leads to high doping amount of SPOP, thus making the composite the membrane have a high proton conductivity. The conductivity of mPBI-TGIC(5%)/SPOP(50%) at 100% RH, 50% RH and 0 RH is 0.143, 0.076 and 0.044 S cm⁻¹ at 180 °C, respectively. In addition, the composite membranes has good methanol resistance and selectivity, so the composite membrane can be applied in the direct methanol fuel cell.

Electrochemical single nano-impacts of electroactive Shewanella oneidensis bacteria at a 7 μm diameter carbon fibre ultramicroelectrode in an aqueous potassium phosphate buffer (pH = 7.2) solution containing a redox active probe (potassium ferro- or ferricyanide) is reported. We present chronoamperometric measurements recorded at the ultramicroelectrode polarized at the potential of the steady-state current of the redox probe in solution (oxidation for K₄Fe(CN)₆ or reduction for K₃Fe(CN)₆) in the presence of bacteria. The shape of current transients associated to single bacteria nano-impacts is compared and discussed as a function of the redox probe in solution and of the ultramicroelectrode applied potential.

Nickel nanowire arrays with preferential growth of (111), (200) and (220) lattice planes were prepared via a modified template-assisted electrodeposition method respectively. As a HER electrocatalyst, (220) preferred orientation nickel nanowire arrays exhibited higher catalytic activity and stability in alkaline solution, and the hydrogen evolution overpotential was as low as 128 mV at the current density of 10 mA · cm⁻². The performance is attributed to the higher surface energy of the (220) lattice plane of nickel nanowire arrays as the exposed surface and more active sites participate in HER process, which is beneficial to charge transfer and decrease of activation energy of reactions. Simultaneously, the activation energy of exposed surface evaluated directly by calculating with First-principles correspond to the trend of the experimental results, catalytic activity (220) > (200)> (111) lattice plane in the hydrogen evolution process. The strategy of using crystal anisotropy to improve catalytic performance can be extended to the synthesis of other nanocrystals with higher activity and high-energy surface catalysts.

As a promising electrochromic material, WO₃ frequently suffers from the cyclic degradation caused by trapped ions in the host structure. The intrinsic trapped sites in WO₃ host structure usually are considered as the main contribution to the formation of trapped ions. In this study, by chronopotentiometry technology to quantify the diffused ions, we find that ions transport behavior plays a key role in the structural stability and the generation of trapped ions. Specifically, repeated insertion/extraction behavior will result in WO₃ structure damage. As a result, the ions transport shows hysteretic kinetics in the subsequent reaction process, and the inserted Li⁺ ions in the coloration process can not be completely extracted, which contributes to the generation of the majority of trapped ions in film. Subsequently, the transmittance of the bleaching state and the optical modulation ability of WO₃ film show serious decay. This work exhibits a new understanding of the degradation of electrochromic materials and offers an efficient method for WO₃ to maintain a long-life performance.

We newly developed a rotating disk electrode-online electrochemical mass spectrometry (RDE-OLEMS) to investigate potential-dependent molecular behaviors in electrode surface vicinity under mass transport-controlled conditions of reacting molecules. The potential-dependent molecular behaviors were investigated by using a quadrupole mass spectrometer (Q-mass) where the molecules are collected through a gas-sampling tip located in near the electrode surface. For the oxygen reduction reaction (ORR) on the polycrystalline Pt electrode, the potential-dependent Q-mass ion signal intensities of O₂ (m/z = 32) that are ascribable to the dissolved oxygen molecules increased linearly with the disk electrode rotation rates without substantial interference from the collection tip, clearly showing that the dissolved O₂ for ORR can be monitored by the RDE-OLEMS. For electrochemical carbon dioxide reduction (ECR) on the polycrystalline Au electrode, the potential-dependent Q-mass ion signal intensities of CO (m/z = 28) generated by the ECR increased with increasing disk rotation rates from 0 (without disk rotation) to 300 rpm in the potential region from −0.4 to −1.4 V vs. the reversible hydrogen electrode. The results demonstrate that the RDE-OLEMS enables us to evaluate the potential-dependent behaviors of reactant and product molecules present near the electrode surface under the mass transport-controlled condition.

The electrochemical polymerization of polyaniline (PANI) was studied using correlative measurements of electrochemistry and UV–vis spectroscopy, i.e., spectroelectrochemistry. The electropolymerization of PANI was performed in an acidic medium (1 M HCl) containing 0.1 M aniline with cyclic voltammetry (CV) in a potential window from −0.3 to 1 V and a 50 mV s⁻¹ scan rate. At the same time, UV–vis absorbance spectra in the wavelength range from 200 to 900 nm were measured for every 10 mV change in the CV. The CV results show the oxidation of the monomer at a high positive potential (0.9 V vs Ag), the continuous growth of the PANI film and the transformation between the three best-known forms of PANI redox in the potential range between −0.3 V and 1 V. In parallel, the spectroscopic study confirmed the formation of PANI oxidation. The spectroscopic results showed the formation of the final conductive PANI product (emeraldine salt) due to the absorbance of the formed charge carriers (polarons, bipolarons) during the polymerization. The correlative electrochemical/spectroscopy study gave an additional dimension to the PANI polymerization mechanism, where not only was the oxidation the lead type of reaction, but the reduction was also found to play an important role.

Electrocatalytic Cu is key to the development of processes that can convert CO and CO₂ to hydrocarbons, and nitrate to ammonia. The hydrogen evolution reaction (HER) often competes with these processes. Few studies studied this reaction on Cu under alkaline conditions. Herein, we examined the HER on Cu electrodes under alkaline conditions in Na⁺- and Cs⁺-containing electrolytes. We found that in 0.1 M solutions of NaOH and CsOH of the highest commercially available purity grades, trace impurities of iron deposit on the Cu electrode during electrolysis. As a result, the rate of the HER is enhanced by up to a factor of ≈5 over the course of eleven cyclic voltammograms (CV) from 0.15 to −0.65 V vs the reversible hydrogen electrode. After removal of the iron impurities, the CVs are stable as a function of cycle number. Comparison of the CVs in pre-electrolyzed 0.1 M NaOH and CsOH reveals that changing the cation from Na⁺ to Cs⁺ has no measurable effect on the HER. With density functional theory (DFT), we further rationalized our experimental findings. We discuss the implications of our results for electrocatalytic processes on Cu electrodes.

Atmospheric pollution is one of the major aspects of concern which led to the research of sensors for the detection of toxic gases. The supreme surface-to-volume ratio makes two-dimensional MoS₂ a promising material to be used as an electronic sensor. Here, we demonstrate the fabrication of a high-performance gas sensor based on atomic-layered MoS₂ nanoflakes synthesized by a facile hydrothermal process. Structural and morphological studies confirmed the formation of few-layered phase pure hexagonal MoS₂ nanoflakes. The results demonstrate that the Pd-MoS₂ layers exhibited a very high relative response to NO gas (700%) at 2 ppm concentration with a minimum NO detection limit of 0.1 ppm and Ni-MoS₂ demonstrated a relative response of 80% towards H₂S gas with a limit of detection of 0.3 ppm with good repeatability and selectivity, owing to the increased adsorption energy of NO on Pd-MoS₂ and H₂S on Ni-MoS₂ through the formation of PdNO_x and NiS₂ complexes respectively. The improved sensing performance of this MoS₂-based sensor also suggests the great potential and possibility of MoS₂ related 2D materials and its combinations for the development of futuristic highly sensitive nanosized gas sensors suitable for anti-pollution automotive system and as volatile biomarkers.

The influence of the amount of Pt deposited onto Rh and Ru nanoparticles on the oxidation of methanol and ethanol has been compared in H₂SO₄(aq) at ambient temperature and in a proton exchange membrane (PEM) cell at 80 °C. In H₂SO₄(aq), Rh@Pt and Ru@Pt show similar enhancements in activities over Pt for both methanol and ethanol oxidation. However, differences in the optimum Pt coverage indicate that compression of the Pt lattice by Rh plays a dominate role, while ligand effects are more important for Ru@Pt. In the PEM cell, the Ru core enhanced activities significantly for both methanol and ethanol, while activities were suppressed by the Rh core. This may arise from dominance of ligand and/or bifunctional effects for the Ru@Pt catalyst at 80 °C. Data from the PEM cell showed that the stoichiometry for ethanol oxidation at Ru@Pt was higher than for Rh@Pt, indicating a higher selectivity for the complete oxidation to CO₂.

We introduce a framework for analyzing and designing EIS inversion algorithms. Our framework stems from the observation of four features common to well-defined EIS inversion algorithms, namely (1) the representation of unknown distributions, (2) the minimization of a metric of error to estimate parameters arising from the chosen representation, subject to constraints on (3) the complexity control parameters, and (4) a means for choosing optimal control parameter values. These features must be present to overcome the ill-posed nature of EIS inversion problems. We review three established EIS inversion algorithms to illustrate the pervasiveness of these features, and show the utility of the framework by resolving ambiguities concerning three more algorithms. Our framework is then used to design the generalized EIS inversion (gEISi) algorithm, which uses Gaussian basis function representation, modality control parameter, and cross-validation for choosing the optimal control parameter value. The gEISi algorithm is applicable to the generalized EIS inversion problem, which allows for a wider range of underlying models. We also considered the construction of credible intervals for distributions arising from the algorithm. The algorithm is able to accurately reproduce distributions which have been difficult to obtain using existing algorithms. It is provided gratis on the repository https://github.com/suryaeff/gEISi.git.

Urea oxidation reaction (UOR) has been known as a viable method for renal/liver disease diagnostic detection. Here, we reported a three-dimensional (3D) nickel oxide nanoparticles dressed carbonized eggshell membrane (3D NiO/c-ESM) as a modified electrode toward urea detection. Several common physical measurements were employed to confirm its structural and morphological information. NiO/c-ESM modified electrode exhibits an outstanding performance for urea determination with a linear range from 0.05 to 2.5 mM, and limit detection of ∼20 μM (3σ). This work offered a green approach for introducing 3D nanostructure through employing biowaste ESMs as templates, providing a typical example for producing new value-added nanomaterials with urea detection.

A highly efficient flow cell for sequential electrolysis containing two complete electrochemical cells, capable of generating reactive species at the upstream working electrode and transporting them to the downstream working electrode, is demonstrated. Deconvolution of the intermixed electrode circuits is accomplished through analysis of the inherent resistance of the electrolyte, which allows for precise and independent control of the electrochemical potential at each electrode without altering concentrations of supporting or background electrolyte species. Sequential electrolysis involving oxidation of hydrogen and reduction of the generated protons downstream is demonstrated at nearly 100% efficiency on Pt-decorated dealloyed porous Nb catalysts. The conversion efficiency of the catalysts is discussed in terms of their geometries and active surface composition, elucidating strategies for use of sequential electrolysis cells for fundamental and applied studies.

The electrodeposition of MoS₂ from dichloromethane (CH₂Cl₂) using tetrabutylammonium tetrathiomolybdate ([NⁿBu₄]₂[MoS₄]) as a single source precursor is presented. The electrodeposition of MoS₂ from CH₂Cl₂ requires addition of a proton donor to the electrolyte and trimethylammonium chloride (Me₃NHCl) was used for this purpose. Electrochemical Quartz Crystal Microbalance (EQCM) experiments have been employed for a detailed study of the electrochemical mechanism and to study the role of the proton donor. EQCM reveals cathodic electrodeposition of MoS₂ and anodic deposition of MoS₃ as well as an additional corrosion process where the deposited MoS₃ strips back into solution. The electrodeposited MoS₂ films are amorphous in nature. All the films were found to be homogeneous in composition across the electrode area and to be reproducible between experiments. Annealing of the as-deposited films under a sulfur atmosphere results in crystalline MoS₂ as confirmed by energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy and X-ray diffraction. The deposited films were smooth and planar, as observed with scanning electron microscopy (SEM), indicating a layer-by-layer growth typical of transition metal dichalogenides.

We present and analyze a model for polycrystalline electrode surfaces based on an improved continuum model that takes finite ion size and solvation into account. The numerical simulation of finite size facet patterns allows to study two limiting cases: While for facet size diameter ${d}^{\mathrm{facet}}\to 0$ we get the typical capacitance of a spatially homogeneous but possible amorphous or liquid surface, in the limit $1[\mathrm{nm}]\ll {d}^{\mathrm{facet}}$, an ensemble of non-interacting single crystal surfaces is approached. Already for moderate size of the facet diameters, the capacitance is remarkably well approximated by the classical approach of adding the single crystal capacities of the contributing facets weighted by their respective surface fraction. As a consequence, the potential of zero charge is not necessarily attained at a local minimum of capacitance, but might be located at a local capacitance maximum instead. Moreover, the results show that surface roughness can be accurately taken into account by multiplication of the ideally flat polycrystalline surface capacitance with a single factor. In particular, we find that the influence of the actual geometry of the facet pattern in negligible and our theory opens the way to a stochastic description of complex real polycrystal surfaces.

Herein, we report the development of a nickel-based catalyst obtained by reduction of Ni²⁺ ions on the surface of ceria nanopowder using aqueous solution of NaBH₄. The catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). Nickel(0) nanoparticles supported on nanoceria (Ni⁰/CeO₂) were employed as electrocatalyst on glassy carbon electrode (GCE) for H₂ evolution reaction. The modified Ni⁰/CeO₂-GCE requires a relatively small overpotentials of 150 mV, 175 mV and 203 mV to drive current densities of 10, 20 and 50 mA cm⁻², respectively. Tafel slope, 80 mV dec⁻¹, indicates that HER process follows the Volmer-Heyrovsky mechanism with relatively high turnover frequency (TOF), i.e. 0.41 and 5.84 s⁻¹ at an overpotential of 100 and 200 mV, respectively. A drastic enhancement in the electrocatalytic activity of Ni⁰/CeO₂-GCE was observed when platinum wire was used as counter electrode instead of graphite rod, especially after long term potential cycling due to platinum dissolution and deposition on the modified electrode. Ni⁰/CeO₂-GCE was found to exhibit high electrochemical stability (i.e. a small change both in the Tafel slope and onset potential) after 2000 CV scans in 0.5 M H₂SO₄, which makes Ni⁰/CeO₂ a potential electrocatalyst for H₂ evolution from water.

Poly(Azure A) (PAA) films doped with sodium dodecyl sulfate (SDS) were grown on transparent indium tin oxide (ITO) glass substrates by cyclic voltammetry. The electrochromism of PAA was investigated by digital video-electrochemistry (DVEC). DVEC consists of the acquisition of sequential digital images during the electro-stimulated changes of PAA color. The evolution of red, green, and blue (R, G, B) colors intensity (I) of analyzed pixels provides enough sensitivity to detect changes of some nmol cm⁻² of electroactive centers. Besides, the different time evolution of these color intensities can serve to discern among different electroactive centers activated in the polymer. For the first time, contrast, coloration efficiency, and bleaching times of PAA are calculated by DVEC. The coloration efficiencies were between 15–25 cm² mC⁻¹ with short response times for the bleaching process between 2.9 and 5.5 s. PAA has good electrochromic performances to be used in electrochromic devices. Our present work provides an important insight into the design principles for a practical application of DVEC to characterize electrochromic devices in light-controlled conditions allowing us to find the best performances of these materials.

Tungsten disulfide quantum dots (WS₂ QDs) embedded lab on genochip based analytical device (PAD) was developed for the specific DNA detection of Meningitis, a life threatening disease. This paper-based lab on genochip was designed by grafting the two electrodes onto the surface of paper using conductive ink. The WS₂ QDs were characterized by X-ray diffraction technique, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Following this, specific oligonucleotide sequence of DNA (capture probe) was immobilized over the surface of WS₂ QDs/PAD electrode. The ssDNA/WS₂QDs/PAD device was characterized electrochemically by cyclic voltammetry. The device was employed for detection of target DNA (by hybridization) by employing methylene blue (MB) as an indicator. The biosensor exhibited a wide linear response in the range 1 nM–100 μM towards the target DNA. The limit of detection (LOD) of target DNA of the proposed device is 1 nM. The advantageous features of this device than the existing biosensors include cheaper analysis cost, tiny sample requirements and stability.

Electrochemical sensor on the basis of glassy carbon electrode (GCE) covered with multi-walled carbon nanotubes and electropolymerized ellagic acid (polyEA/MWNT/GCE) has been developed for the naringin determination. Polymeric film has been obtained by potentiodynamic electrolysis. The working conditions of polymeric coverage formation (scans number, supporting electrolyte pH, monomer concentration and electrolysis parameters) providing the best naringin response have been found. Ellagic acid (EA) electropolymerization has to be performed from 10 μM monomer by sevenfold cycling of potential in the range of 0.0–1.0 V at the scan rate of 100 mV s⁻¹ in phosphate buffer (PB) pH 7.0. Scanning electron microscopy (SEM) confirms successful modification of the sensor surface with evenly distributed 30–50 nm spherical particles providing 9.6-fold increase of the electrode effective surface area vs GCE. Naringin electrooxidation parameters on polyEA/MWNT/GCE have been found. Sensor acting under conditions of differential pulse voltammetry in PB pH 6.5 provides linear dynamic ranges of 0.050–1.0 and 1.0–100 μM with the detection and quantification limits of 14 and 47 nM, respectively. The selectivity of sensor towards naringin in the presence of inorganic ions, saccharides, hesperidin, ascorbic and phenolic acids is proved. The sensor developed has been successfully tested on grapefruit juices.

Antimony sulfide graphene oxide (Sb₂S₃-GO) was synthesized using a solvothermal method for electrochemical detection of dopamine (DA). Thiourea acted as a sulfur source, while polyvinyl pyrrolidone (PVP) acted as a surfactant to fabricate nanoproduct in the presence of GO. X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectra, Energy-dispersive X-ray spectrum (EDS), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) were employed to characterize Sb₂S₃-GO nanocomposite, and the results exhibited a large number of spherical Sb₂S₃ particles were attached to the surface of GO. Electrochemical techniques were used to study the performance of sensor, and the results showed the sensor has excellent electrochemical characteristics to detect DA with linear ranges of 1.55 μM–15.55 μM, 15.55 μM–0.35 mM, excellent sensitivity of 307.7 μA mM⁻¹ cm⁻² and 205.4 μA mM⁻¹ cm⁻², and a low detection limit of 0.8 μM (at an S/N radio of 3). Therefore, Sb₂S₃-GO can be used potential sensing material to detect dopamine.

A non-enzymatic electrocatalyst, nickel oxide (NiO) nanosheets was developed via a facile hydrothermal approach and further characterized in detail. To harness the potential of NiO nanosheets as a potential electrocatalyst, the hydrothermally synthesized nanosheets were fixed onto the sensor working electrode for glucose sensing application. The NiO nanosheets providing abundance active sites for non-enzymatic glucose detection showed sensitive (1618.4 μA mM⁻¹ cm⁻²) response in the linear range of 0.25–3.75 mM. The excellent electrocatalytic activity of the NiO modified gold working electrode resulted in a low detection limit (2.5 μM). Moreover, the sensor selectively detected glucose in the solution containing common interferants such as cholesterol, dopamine, uric acid and ascorbic acid, further makes it highly suitable for non-enzymatic glucose detection in near-real samples.

In this work, a sensitive polyethylenimine functionalized Perylene derivative PTC-PEI, S₂O₈²⁻ and 3D flower-like MoS₂ (3D MoS₂ NFs) ternary system was fabricated for quantitation of Methotrexate (MTX) based on the quenched electrochemiluminescence (ECL) signals. Specifically, the PTC-PEI was prepared via cross-linking Perylenetetracarboxylic acid (PTCA) and polyethylenimine (PEI). Then, the hybrid nanocomposite PTC-PEI-MoS₂ was synthysized through electrostatic absorption effect between PTC-PEI and 3D MoS₂ NFs. With the excellent catalytic effect of 3D MoS₂ NFs towards the electrochemical reduction process of S₂O₈²⁻ thus resulting in generation of more sulfate radical anions (SO₄^·−), the ECL signal probe PTC-PEI-MoS₂ exhibits higher luminous efficiency compared with PTC-PEI (3-fold enhancement). In addition, electrochemical regenerable property of Mo⁶⁺/Mo⁴⁺ active sites endows 3D MoS₂ NFs excellent signal enhancement efficiency. Under the optimum conditions, a linear range from 10 μM to 1pM with the limit of detection down to 0.15 pM could be obtained in MTX determination. Notably, the proposed strategy provides a new idea for sensitive determination of MTX.

A sensor based on polyethylenimine-functionalized multi-walled carbon nanotubes/glassy carbon electrode (fMWCNT-PEI/GCE) was developed for promethazine hydrochloride (PMZ) detection in pharmaceutical samples. PMZ is oxidized at the modified electrode at more negative potentials and with higher sensitivity than at the bare electrode. The morphological characterization of the sensor surface showed a homogeneous layer with size distribution of the diameters of the PEI-fMWCNT ranging from 22–47 nm. The characterization of the electrochemical behavior suggested that an equal number of electrons and protons participate in the PMZ irreversible oxidation on the fMWCNT-PEI/GCE. The optimized conditions were Sörensen buffer at pH 2.0, frequency of 90 s⁻¹, amplitude of the pulse of 40 mV, and height of the potential step of 2 mV. Based on the most sensitive peak, at ca. −0.75 V, which is related to the formation of the phenazothiazonium ion, the PMZ calibration curve was obtained with sensitivity of 3.21 × 10⁻³ A mol⁻¹ l, a linearity range of 4.97 × 10⁻⁷ to 5.03 × 10⁻⁶ mol l⁻¹, and a detection limit of 2.31 × 10⁻⁷ mol⁻¹ l. This methodology was successfully validated in pharmaceutical samples by comparison with the standard method of the Pharmacopoeia, showing high potential applicability of the fMWCNT-PEI/GCE.

Ferrocene-substituted 2,5-di(thienyl)pyrrole (SNS-Fc) was electrochemically polymerized in the presence and absence of 3,4-ethylenedioxythiophene (EDOT) and utilized for biosensing upon immobilization of glucose oxidase (GOD) through cross-linking. The two biosensors, homopolymer P(SNS-Fc) and copolymer-based P(SNS-Fc-co-EDOT) were evaluated by comparison in terms of analytical performance. Due to the conducting-redox active nature of the films, the study was able to consider the developed sensors both as "first generation," monitoring H₂O₂ oxidation and as "second generation," using the optimum potential for ferrocene oxidation. The difference in performance at these two working potentials served as assessment of the influence of ferrocene moiety within the conducting film. In the scope of further improvement, carbon nanotubes (MWCNTs) were incorporated in both type systems. This improved the detection efficiency leading to extension of linear range up to 1.5 mM with sensitivity up to 23.12 μA mM⁻¹ cm⁻² and detection limits as low as 0.43 μM. The proposed biosensors showed little to no interference to other saccharides and accurate recovery in real sample analysis, especially when glucose detection was based on mediated electron transfer. Thus, the association of ferrocene, poly 2,5-di(thienyl)pyrroles and CNTs is highly efficient in the development of sensitive "reagentless" biosensor systems.

An effective approach is required to pattern graphene with high spatial resolution and accuracy for advanced graphene-based sensors. In this work, we describe a simple and effective strategy for direct writing micro-scale graphene patterns by drop-on-demand (DoD) electrohydrodynamic jet (E-Jet) printing, using a highly concentrated graphene dispersion. The uniform micro-scale graphene patterns were formed by droplets produced under the electric field "pulling" force, these droplets are far smaller than the inner diameter of nozzle, which can effectively avoid nozzle clogging. With the control of pulse voltage width and frequency, different micro-scale graphene patterns were directly printed using DoD E-Jet printing technique. Graphene lines with a thickness of 5 nm were produced for 1 time printing, which provided a resistivity of 4.2 mΩ·cm. In addition, the graphene layer was directly written on the Pt microelectrodes to form Graphene/Pt (G/Pt) composite microelectrodes. The electrochemical test shows that the peak current of G/Pt composite microelectrodes was more than twice larger than that of bare Pt microelectrodes. The sensing sensitivity was significantly increased, presenting great potential for high performance electrochemical sensing devices.

In the present work, a novel sensitive electrochemical carbon paste electrode chemically modified with yttrium doped manganese oxide Mn₂O₃/Y₂O₃ nanostructures was assigned for determination of marbofloxacin (MRB) using square wave voltammetry (SWV) method. MRB has a broad spectrum of bactericidal activity for the treatment of urinary, respiratory and dermatological diseases in bovines and their retention in animal meats and milk leads to adverse side effects for the consumer. Thus a rapid estimation of minor concentrations of MRB has exerted a great concern to ensure food safety. XRD, EDX, Raman spectroscopy, SEM, and TEM techniques were employed to characterize the samples. The electrochemical oxidation behavior of MRB shows irreversible anodic peak at 1.10 V vs Ag/AgCl, in Britton–Robinson buffer (BR) at pH 5.0. The relationship was rectilinear over the range 10 × 10⁻⁹–1.0 × 10⁻⁴ M between the peak current and its related concentration with a minimum detection limit of 2.4 × 10⁻⁹ M. The developed method was green chemistry challenges and successfully applied to assay the drug in its dosage form, bovine meat and milk samples with a good recovery lies between 94.56% and 105.33% with relative standard deviation less than 10%.