Table of contents

The effects of using low-cost inorganic fluoride salts (i.e., KF or NaF) as fluoride sources in fluoride shuttle batteries (FSBs) on the electrochemical compatibility of BiF₃ electrodes are investigated herein. The preparation of electrolytes containing saturated KF or NaF and 0.5 M 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (DiOB-Py) in G4 is described. For Py/NaF/G4, the discharge and charge reactions of BiF₃ were hindered because of the low solubility of NaF as well as the low ionic conductivity of the electrolyte. However, inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed that the solubility of KF in Py/KF/G4 was moderate and the ionic conductivity of Py/KF/G4 was promising. Higher oxidation and reduction peaks observed in the cyclic voltammograms of Py/KF/G4 than those of Py/G4 and Py/NaF/G4 are attributed to the enhanced electrochemical activity of the former. Consequently, the BiF₃/C nanocomposite electrode exhibits good cycling capability in Py/KF/G4, with initial discharge/charge capacities of 316/218 mAh g⁻¹, respectively. Moreover, the ICP-MS and Raman spectroscopy analyses revealed that defluorination reactions of BiF₃ occur via a direct desorption mechanism. Py/KF/G4 is the first effective electrolyte based on a low-cost inorganic salt. FSBs exhibit improved performance in Py/KF/G4 compared with CsF salt systems, which warrants further investigation.

The present study aims to develop a simplified mathematical model for the evolution of heating-induced thermal runaway (TR) of lithium-ion batteries (LIBs). This model only requires a minimum number of input parameters, and some of these unknown parameters can be obtained from accelerating rate calorimeter (ARC) tests and previous studies, removing the need for detailed measurements of heat flow of cell components by differential scanning calorimetry. The model was firstly verified by ARC tests for a commercial cylindrical 21700 cell for the prediction of the cell surface temperature evolution with time. It was further validated by uniform heating tests of 21700 cells conducted with flexible and nichrome-wire heaters, respectively. The validated model was finally used to investigate the critical ambient temperature that triggers battery TR. The predicted critical ambient temperature is between 127 °C and 128 °C. The model has been formulated as lumped 0D, axisymmetric 2D and full 3D to suit different heating and geometric arrangements and can be easily extended to predict the TR evolution of other LIBs with different geometric configurations and cathode materials. It can also be easily implemented into other computational fluid dynamics (CFD) code.

The energy density of traditional Li−Si/FeS₂ thermal batteries, which multiple cations are contained in molten salt electrolyte, is limited by the deficiency of Li⁺ in cathode when a high discharge current is applied. To address this issue, LiCl−KCl is taken as an example to build a functional gradient structure through Li−Si/FeS₂ thermal batteries. By levering the Li⁺ concentration in cathode and preventing the formation of high concentration polarization resistivity as well as molten salt precipitation, the energy density of Li−Si/FeS₂ single cell with a discharge current of 500 mA cm⁻², increase from 157.0 Wh kg⁻¹ to 218.4 Wh kg⁻¹ at 450 °C (with an increase ratio of 39.1%), compared with the original one. Similarly, a 25.6% raise is observed at 525 °C. Moreover, the effects of LiCl-rich electrolyte and the functional gradient structure on the electrochemical performance of Li−Si/FeS₂ single cells are discussed and classified.

In situ electrochemical cells were assembled with an amorphous germanium (a-Ge) film as working electrode and sodium foil as reference and counter electrode. The stresses generated in a-Ge electrodes due to electrochemical reaction with sodium were measured in real-time during the galvanostatic cycling. A specially designed patterned a-Ge electrode was cycled against sodium and the corresponding volume changes were measured using an AFM; it was observed that sodiation/desodiation of a-Ge results in more than 300% volume change, consistent with literature. The potential and stress response showed that the a-Ge film undergoes irreversible changes during the first sodiation process, but the subsequent desodiation/sodiation cycles are reversible. The stress response of the film reached steady-state after the initial sodiation and is qualitatively similar to the response of Ge during lithiation, i.e., initial linear elastic response followed by extensive plastic deformation of the film to accommodate large volume changes. However, despite being bigger ion, sodiation of Ge generated lower stress levels compared to lithiation. Consequently, the mechanical dissipation losses associated with plastic deformation are lower during sodiation process than it is for lithiation.

Ethylene carbonate (EC) has been used as the Solid-Electrolyte Interphase (SEI) former in the conventional electrolyte for decades. However, its low anodic stability leads to severe capacity decay during cycling under high voltage operation. Therefore, finding a viable electrolyte with high anodic stability and the ability to form robust SEI for high voltage lithium-ion batteries is of primary importance. In this study, a series of electrolytes containing various fluorinated cyclic carbonates as the SEI former have been designed, synthesized and evaluated. Linear sweep voltammetry study suggested that fluorinated cyclic carbonates generally possess higher anodic stability than EC. Based on the cycling performance of LiNi_0.5Co_0.2Mn_0.3O₂ (NMC532)/ graphite full cells, the electrolyte with DFEC/FEMC (1.0 M LiPF₆) inhibited the oxidation side reaction on the cathode and forms a vigorous SEI on the anode. The high voltage NMC532/Graphite cell utilizing the novel electrolyte exhibits excellent cycling durability under both room and elevated temperature. The superior performance of the DFEC based electrolyte was further unveiled by SEM, EDAX and XRD. Both the anode and cathode of the full cell employing DFEC based electrolyte retained their intrinsic structures after cycling while the electrodes cycled in conventional electrolyte showed severe degradation.

We present in situ electrochemical impedance spectroscopy data measured during (de)sodiation and (de)lithiation of a commercial hard carbon (HC) anode material. For this purpose, two different systems of micro-reference electrodes (μ-RE) were used: a gold-wire reference electrode (μ-GWRE) for Li/HC half-cells and a tin-wire reference electrode (μ-TWRE) for Na/HC half-cells. We show that for both (de)sodiation (using EC/DMC + 1 M NaPF₆ electrolyte) and (de)lithiation (using EC/EMC + 1 M LiPF₆ electrolyte) the impedance spectra are dominated by a charge transfer resistance (R_CT) which is reversibly decreasing/increasing with increasing/decreasing state-of-charge. The contributions to the HC electrode resistance (R_anode), i.e., charge transfer (R_CT), pore (R_pore), and separator resistance (R_HFR), were obtained by fitting the impedance spectra using a representative equivalent circuit. We conclude that the R_CT associated with sodiation of HC is ≈10-fold higher compared to the lithiation of HC at 100% SOC. Furthermore, we compare the evolution of R_anode measured in situ over 52 cycles at the same SOC. We find that the higher electrode resistances for sodiated HC result in a considerably reduced rate capability for HC sodiation. For a potential future commercialization of sodium-ion batteries, the fast-charging properties (=HC sodiation) would be a crucial performance indicator.

Graphite is the most commonly used anode material in commercial lithium-ion batteries (LiBs). Understanding the mechanisms driving the dimensional changes of graphite can pave the way to methods for inhibiting degradation pathways and possibly predict electrochemical performance loss. In this study, correlative microscopy tools were used alongside electrochemical dilatometry (ECD) to provide new insights into the dimensional changes during galvanostatic cycling. X-ray computed tomography (CT) provided a morphological perspective of the cycled electrode so that the effects of dilation and contraction on effective diffusivity and electrode pore phase volume fraction could be examined. During the first cycle, the graphite electrode underwent thickness changes close to 9% after lithiation and, moreover, it did not return to its initial thickness after subsequent delithiation. The irreversible dilation increased over subsequent cycles. It is suggested the primary reason for this dilation is electrode delamination. This is supported by the finding that the electrode porosity remained mostly unchanged during cycling, as revealed by X-ray CT.

Developing new methods to prepare pseudocapacitive materials with high pseudocapacitance/electronic conductivity is of great interest for hybrid supercapacitors. Recently, the exfoliation/restacking of manganese and cobalt layered transition metal oxides was proposed. Despite improved electrochemical performance of such Mn-Co composites, their bulk organization (i.e. the scale at which the stacking occurs) and structure (i.e. porosity...) remains to be elucidated so far. To tackle this issue, here, SEM and Auger analysis with a nanoscale resolution, coupled to cross-section preparation is proposed. A good correlation between the restacking method, the nanoscale organization/structure of composites and resulting electrochemical performance is obtained. Importantly, the combination of cross-section with Auger analysis allows revealing the nanoscale stacking of the Mn and Co phases. Also, the porosity of the nano-composites, revealed by the cross-section preparation, is correlated to the speed of the restacking process. A fast flocculation step forms aggregates with a porous bulk structure while a slow flocculation step leads to a dense and closed bulk structure of the aggregates. These results highlight that a better control/understanding of the organization/structure of such nano-composites can lead to further improvement. Overall, the innovative cross-section Auger approach proposed in this study should also benefit to the understanding of other nano-composites.

We investigated the suppressed capacity fading of a Ca-substituted P3-type Na_xCoO₂ during the charge/discharge process. The Ca-substituted Na_xCoO₂ shows similar phase transition behavior to the Ca free one, with an expanded P'3 phase region. The capacity fading of the Na_xCoO₂ is highly correlated with the phase transition at 4.0 V of P'3–O3' phase transition and at 2.7 V of O'3–P'3 phase transition. The amount of Co₃O₄ observed in the cycled electrodes corresponds to the capacity loss during the cycling test. Thus, the migration of the Co^3+/4+ ions during the phase transition process causes the capacity fading. The decomposition of the electrolyte solution also accelerates the migration of the Co^3+/4+ ions. Though the Ca-substitution does not prevent the phase transition, the Ca-substituted Na_xCoO₂ shows improved capacity retention.

The layered siloxene and germanane, derived from CaSi₂ and CaGe₂, respectively, have shown very promising results as anodes for Lithium-ion batteries. Their delivered capacities, capacity retention and high rate cycling are superior compared to bulk Si and Ge. These positive features are most probably related to the layered morphology that buffers the volume changes and improves the kinetics. Despite numerous recently published studies regarding their electrochemical properties, very little is known about their electrochemical mechanism. In this work, we have used a combination of different characterization techniques to study the processes taking place during the lithiation of siloxene and germanane and compared with Si and Ge. Our results suggest a slightly different pathway for the lithiation of siloxene and germanane: their initial layered morphology is preserved after cycling, the crystalline Li₁₅Si₄ and Li₁₅Ge₄ characteristic of an alloying mechanism are absent and possibly different lithiated intermediates are formed. We provide then, an initial assessment of the involved Li_xSi and Li_xGe phases and propose the hypothesis of a reversible Li intercalation in the siloxene and germanane layers.

The applicability of heat generation data obtained after cylindrical Li-ion cells discharging with a constant current was analyzed thoroughly to determine cell degradation mechanisms. Different commercial and noncommercial cylindrical Li-ion cells, wherein graphite was used for negative electrode creation, were considered in this study and the degradation mechanisms were analyzed during cycling and storage. The heat generation in the cylindrical cells was estimated using heat flux and temperature measurements of the cell surface. The results obtained using analysis of the heat generation data were compared with those obtained using differential voltage analysis. The use of the heat generation data was shown to improve the detection and separation of the degradation mechanisms in Li-ion batteries during cycling and storage. The differential curve, which is based on the heat generation data, was proposed to investigate the degradation mechanisms. Moreover, the effects of the C-rate current and temperature on the form of the proposed differential curve were evaluated.

Fast charging of Li-ion batteries would make "fueling" of electric vehicles comparable in time to fueling of gasoline-powered cars, increasing consumer appeal of the new technology. Taking the US Department of Energy goal of safe 6 C charging to 80% capacity as a guide, we describe approaches that can mitigate Li plating on the graphite anode. To make this possible, a variable-rate anode potential charging protocol has been implemented by using a microprobe reference electrode to continuously monitor and adjust the current, in this way avoiding low anode potentials that favor Li deposition. Various implementations of the anode potential control are considered using electrochemical modeling and compared with the experimental data. For charge to 80% capacity at 30 °C, an average C-rate of 4.97 C was obtained for an NCM523/graphite cell with 70 μm thick graphite electrode and 7.40 C for a cell with 47 μm thick graphite electrode. Our electrochemical model accounts for these observations and provides a means to extrapolate the approach to other cell designs and operation regimes, drawing the maximum average fast charging rates that can still avoid Li plating.

In this work, we report a systematic investigation about the chemical-physical properties of mixtures containing glyoxylic solvents (tetramethoxyglyoxal (TMG) and tetraethoxyglyoxal (TEG)) and organic carbonates, and about the use of these blends as electrolytes for lithium-ion batteries (LIBs). We showed that these mixtures display promising conductivities and viscosities as well as high thermal stability. Furthermore, they also display significantly higher flash points (up to 60 °C) than the state-of-the-art LIB electrolytes. These mixtures can be successfully utilized for the realization of lab scale LIBs displaying high stability and good rate capability at high C-rate. Furthermore, LIBs containing this innovative electrolyte display good stability at room temperature as well as at 40 °C and 60 °C. Considering these results, mixtures of glyoxylic acetals and organic carbonates appear as promising electrolytes for advanced LIBs.

A matrix of LiNi_0.5Mn_0.3Co_0.2O₂/graphite cells filled with 1.33 molal LiPF₆ in EC:EMC:DMC (ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate) (25:5:70 by volume) electrolyte and different weight percentages of vinylene carbonate (VC) and ethylene sulfate (DTD) electrolyte additives underwent prolonged charge-discharge cycling at 20 °C and 40 °C. The volume of gas produced during formation and cycle testing was measured. The impedance spectra of the cells before and after cycling was measured. After testing, the electrolyte was extracted for study by nuclear magnetic resonance spectroscopy (NMR) and gas chromatography/mass spectroscopy (GC-MS) to determine what changes in electrolyte composition had occurred. Some cells had their negative electrodes studied by scanning micro-X-ray fluorescence to quantify the amount of transition metals that transferred from the positive electrode to the negative electrode during the testing. Cells containing 1% VC or 2% VC with an additional 1% DTD by weight had the best capacity retention and lowest impedance growth. NMR and GC-MS suggest that these additive combinations promote increased electrolyte salt consumption which may represent a source of lithium to replenish the lithium inventory. Only a small amount of transition metals (0.03% or less) originating from the positive electrode active material was found on the negative electrode after testing. Most cells had over 1500 cycles at both 20 °C and 40 °C conditions.

SiO_x is a silicon-based anode material for Li-ion batteries that has a high specific capacity and good cycle life. Lithiation of SiO_x results in the formation of active Si cores surrounded by an inactive stabilizing matrix of irreversible lithium silicates and lithium oxides. SiO_x with adjustable values of x can be synthesized by roller milling under oxygen flow, with the oxygen content being controlled by the amount of time spent milling in oxygen vs milling under argon. A fast and inexpensive oxygen content determination method was needed for determination of the oxygen content in SiO_x as the roller milling process proceeded. A simple 4-step procedure to determine the oxygen content in SiO_x is presented using a KOH solution, aluminized pouch bags, and Archimedes gas quantification measurements. This method can serve as a quick and inexpensive substitute to traditional oxygen content determination measurements such as gas fusion analysis.

Volumetric changes occur in electrodes of rechargeable Li-ion batteries during charge-discharge cycles. In solid-state batteries, the resulting strains cause mechanical degradation of the electrodes, solid electrolyte (SE) and/or SE-electrode interface due to the presence of brittle interfaces as well as mechanical constraints. Here, we investigate the chemo-mechanical response in working electrodes of solid-state Li-ion batteries. In situ strains are measured by full-field optical Digital Image Correlation (DIC) in a high stiffness oxide solid electrolyte, LAGP, along with a model Au working electrode during cyclic voltammetry. Mechanical deformations are correlated with electrochemical performance and damage mechanisms. The measured strains are large enough to induce cracking in the solid electrolyte. Moreover, we show the chemo-mechanical strains developed in electrodes of a solid-state battery are less reversible than those of liquid electrolyte batteries.

Particle cracking caused by diffusion-induced stresses (DISs) is an important reason for lithium-ion battery (LIB) capacity fading. In this study, concentration-dependent material properties are introduced to model the distribution of the concentrations and evolution of DISs in anisotropic active particles. The concentration-dependent diffusion coefficient increases the concentration gradient and thus the DISs, and the concentration-dependent elastic modulus hardening increases the internal DISs and thus the stress-enhanced diffusion of Li ions. Diffusion in the direction of a large diffusion coefficient enhances the diffusion in the direction of a small diffusion coefficient, which leads to an anisotropic concentration, concentration gradient and DISs. The greater the anisotropic difference within the particles is, the more obvious the decrease in the radial stress and hoop stress. The results can be comparable with many published experimental results of graphite and indicate that the role of concentration-dependent material properties and anisotropy in the particles cannot be ignored.

After the lithium extraction from LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) to high-voltage region, structural variation has been investigated during relaxation process. When the lithium ions are extracted to x ≤ 0.12 for Li_xNi_0.8Co_0.1Mn_0.1O₂, H3 phase is mainly observed in addition to small amount of H2 phase. For highly lithium extraction up to x = 0.09 or 0.06, excess amount of H3 phase is created at the charging which turns into H2 at the relaxation. On the other hand, no significant variation is observed for the sample of x = 0.12. In comparison with LiNiO₂, less amount of transformation from H3 to H2 occurs during the relaxation for NCM-811. For all the samples, Ni interlayer distance of H3 phase decreases with relaxation time, which is presumably due to the increase in valence of Ni for diminishment of lithium concentration in the remaining H3 phase.

Solid state electrolytes are receiving significant interest due to the prospect of improved safety, however, addressing the incidence and consequence of internal short circuits remains an important issue. Herein, a battery based on a LiI-LiI(HPN)₂ solid state electrolyte demonstrated self-healing after internal shorting where the cells recovered and continued to cycle effectively. The functional rechargeable electrochemistry of the self-forming Li/I₂-based battery was investigated through interfacial modification by inclusion of Li metal (at the negative interface), and/or fabricated carbon nanotube substrates at the positive interface. A cell design with lithium metal at the negative and a carbon substrate at the positive interface produced Coulombic efficiencies > 90% over 60 cycles. Finally, the beneficial effects of moderately elevated temperature were established where a 10 °C temperature increase led to ∼5× lower resistance.

The cycle stability of lithium negative electrodes for Li–air secondary batteries was studied under oxygen atmosphere using Li∣Li symmetric cells with three organic electrolyte solutions: 1.0 M LiCF₃SO₃/tetraglyme (G4), 1.0 M LiN(SO₂CF₃)₂/G4, and 1.0 M LiNO₃/G4. Of these, 1.0 M LiNO₃/G4 showed excellent stability without dendrite deposition, even for increased dissolution/deposition capacity from 0.50 to 2.0 mAh cm⁻². These results are considered to be due to the stable Li₂O passivation layer that was formed, not only by the direct reaction with oxygen, but also by the action of NO₃⁻ as an oxidant, which released NO₂⁻ as a redox mediator. Li–O₂ cells with 1.0 M LiNO₃/G4 showed a clear charging voltage plateau at 3.7 V, which evidenced the redox mediator effect of NO₂⁻, and cell cycleability was enhanced to 25 cycles.

A LiNiO₂ cathode material with a layered structure and a high capacity was synthesized by co-precipitation with Taylor−Couette flow. Taylor−Couette flow is caused by the rotation of an inner cylinder in a device consisting of two concentric shaft cylinders. A regular donut-shaped vortex is developed above a certain rotational speed of the inner cylinder. Ni(OH)₂ precursors synthesized by co-precipitation with the Taylor–Couette flow were sintered at 600 °C, 650 °C, 700 °C, and 750 °C. The LiNiO₂ cathode material synthesized at 700 °C exhibited the highest discharge capacity of 233 mAh g⁻¹. It was confirmed that the cyclability and rate performance of the LiNiO₂ cathode material improved at other sintering temperatures.

The conventional LiPF₆/carbonate-based electrolytes have been widely used in graphite (Gr)-based lithium (Li) ion batteries (LIBs) for more than 30 years because a stable solid electrolyte interphase (SEI) layer forms on the graphite surface and enables its long-term cycling stability. However, few of these electrolytes are stable under the more stringent conditions needed with a Li metal anode (LMA) and other anodes, such as silicon (Si), which exhibit large volume changes during charge/discharge processes. Many different approaches have been developed lately to stabilize Li metal batteries (LMBs) and Si-based LIBs. From this aspect, localized high-concentration electrolytes (LHCEs) have unique advantages: not only are they stable in a wide electrochemical window, they can also form stable SEI layers on LMA and Si anode surfaces to enable their long-term cycling stability. The ultrathin SEI layer formed on a Gr anode can also improve the safety and high-rate operation of conventional LIBs. In this paper, we give a brief summary of our recent work on LHCEs, including their design principle and applications in both LMBs and LIBs. A perspective on the future development of LHCEs is also discussed.

Silicon is a promising alternative anode material to graphite because of its high gravimetric and volumetric energy densities. However, severe capacity fading is observed in Si electrodes, and it is a result of mechanical changes of Si, such as volume changes, stress or fracture. Furthermore, these mechanical behaviors are strongly coupled with the electrochemistry of the Li–Si alloying reaction in Si-based electrodes, including both thermodynamics and kinetics. Therefore, the electrochemical properties of Si-based electrodes are strongly dependent on the control of the mechanics of Si during lithiation/delithiation. Thus, it is very important to understand the correlation between electrochemistry and mechanics. Here, we review lithiation/delithiation behaviors of various types of Si-based electrodes, applying a fundamental understanding of electrochemistry and mechanics and the correlation between them.

Silicon (Si) is a promising anode material for lithium-ion batteries owing to its high theoretical capacity. However, it suffers from poor capacity retention during cycling due to mechanical stresses, pulverization, and an unstable solid electrolyte interface. One practical approach to mitigate the problem is a coating design, where nano-sized silicon is encapsulated within a selected protective layer. In this study, silicon nanoparticles have been coated with a protective layer of Li₄Ti₅O₁₂ (LTO) ceramic and prepared using a water-based sodium alginate binder. It is found that the Si@LTO composites can be combined with graphite to improve battery performance further. The composite electrodes have been tested in half cells at C/10 and 1C rates. The best Si@LTO and graphite composite has an initial high capacity (∼900 mAh g⁻¹ at C/10 and ∼600 mAh g⁻¹ at 1C) and good capacity retention. It is found that this capacity retention is superior to Si@LTO alone and a binary composite of silicon with graphite. These Si@LTO + graphite composites are a promising way to integrate silicon into the development of stable and high-energy-density lithium-ion batteries.

Highly stable lithium-ion battery cycling of niobium tungsten oxide (Nb₁₆W₅O₅₅, NWO) is demonstrated in full cells with cathode materials LiNi_0.6Mn_0.2Co_0.2O₂ (NMC-622) and LiFePO₄ (LFP). The cells show high rate performance and long-term stability under 5 C and 10 C cycling rates with a conventional carbonate electrolyte without any additives. The degradation of the cell performance is mainly attributed to the increased charge transfer resistance at the NMC side, consistent with the ex situ XRD and XPS analysis demonstrating the structural stability of NWO during cycling together with minimal electrolyte decomposition. Finally, we demonstrate the temperature-dependent performance of this full cell at 10, 25 and 60 °C and confirm, using operando XRD, that the structural change of the NWO material during lithiation/de-lithiation at 60 °C is very similar to its behaviour at 25 °C, reversible and with a low volume change. With the merits of high rate performance and long cycle life, the combination of NWO and a commercial cathode represents a promising, safe battery for fast charge/discharge applications.

The value and interpretation of dynamic electrochemical impedance spectroscopy (DEIS) during the charging and discharging of lithium-ion batteries is examined using the Doyle-Fuller-Newman pseudo-two-dimensional (P2D) lithium-ion battery model with parameters for a lithium-cobalt-oxide/graphite cell. Two computational approaches are explored to balance accuracy, speed, and interpretability: (i) A brute force time domain calculation of the full nonlinear equation set subject to direct current (DC) plus superimposed sinusoidal modulation of frequency ω₁, followed by post-processing with short-time Fourier transforms to track the dynamic impedance signal at the modulation frequency during charge and discharge; (ii) A fast-computing time-separated method that solves the C-rate dependent P2D equations for the DC charge/discharge transients occurring on the slow time-scales, t_b ∼ O(3600 s/C), followed by solutions to linearized frequency domain equations derived for direct computation of the dynamic impedance signal. The time-separated method is rigorously correct in the limit 1/(t_bω₁) → 0. Key physics that drives differences between stationary and dynamic EIS signals is easily explored with the time-separated method. C-rate dependent studies show that DEIS signals are selectively sensitive to interfacial processes in ways that may be promising for real-time diagnostics and control of the negative electrode at high states-of-charge (SOC) and the positive electrode at low SOCs.

Herein, we report a method of recycling spent lithium-ion batteries (LIBs) cathode materials by utilizing them as a metal feedstock for the synthesis of Mn-based metal-organic frameworks (Mn-MOF). Spent cathodes were converted to manganese salts using acids (HCl and H₂SO₄) and reacted with commercial benzene-1,4-dicarboxylic acid (H₂BDC), as an organic linker. The LIB-derived metal salts were compared to commercial available MnCl₂ salt in the formation of Mn-MOFs. Mn-MOFs from spent LIBs (MOF(Cl₂) and Mn-MOF(SO₄)) exhibited similar morphological, structural and textural properties when compared to that obtained from commercial MnCl₂ salt. HCl obtained MOF (Mn-MOF(Cl₂)) was analysed for electrochemical properties due to its superior structural properties. It achieved coulombic efficiency of approximately 99% and discharge capacity of 1355 mAh g⁻¹ as compared to Mn-MOF obtained using commercial salt (Mn-MOF(Com)) with a discharge capacity of 772.55 mAh g⁻¹ at 100 cycles. The developed LIBs recycling strategy has the potential for contributing to existing LIBs recycling strategies and as well to the circular economy.

Dual carbon batteries have recently attracted significant attention because of their ecofriendliness and reliability. In this study, graphene-like graphite (GLG) was prepared by thermal reduction of graphite oxide to be used as a cathode material, and the electrochemical PF₆⁻ anion-intercalation reaction into GLG was investigated. Decreasing the heat-treatment temperature of GLGs from 900 °C to 600 °C resulted in increasing the reversible capacities and interlayer distances of GLG samples. Among them, GLG synthesized at 700 °C (GLG700) showed the largest discharge capacity of 137 mAh g⁻¹, which was much larger than that of graphite (52 mAh g⁻¹). Variations in the X-ray diffraction patterns and Raman spectra of GLG700 indicated that the stage number reached 1 at 4.8 V (vs Li⁺/Li) while that of graphite was 2 at the same potential. This indicates that GLG could store PF₆⁻ anion in every interlayer, which is probably one of the main causes of the larger capacity. The charge–discharge cycling test of GLG700 showed that the capacity gradually increased during cycling, and the coulombic efficiency was approximately 97% at every cycle after the 5th cycle. These results clearly demonstrate that GLG can be used as a cathode material with a large capacity for dual carbon batteries.

Rechargeable secondary batteries operating through fluoride-ion shuttling between the positive and negative electrodes, referred to as fluoride shuttle batteries (FSBs), offer a potentially promising solution to overcoming the energy-density limitations of current lithium-ion battery systems. However, there are many technical issues that need to be resolved to achieve high-quality fluoride-carrying electrolytes and ensure reversible transformations between a metal and its fluoride counterpart at both electrodes. Here, we introduce novel lactone-based liquid electrolytes consisting either of CsF or KF, which are prepared by a solvent substitution method. Although the maximum fluoride-ion concentration achieved by the method is approximately 0.05 M, these systems behave as strong electrolytes where CsF(KF) is almost fully dissociated into Cs⁺(K⁺) and F⁻ ions to give a maximum ionic conductivity of 0.8 mS.cm⁻¹. Hence, the solvent supports electrochemically active fluoride ions that can drive reversible metal/metal-fluoride transformations at room temperature for a wide range of metal electrodes. However, irreversible reductive reactions of the solvent, also promoted by the fluoride ions, limit currently the negative potential window to approximately −1.5 V vs the standard hydrogen electrode.

In support of GM's traction battery efforts, we derive and implement a method to describe the electrochemical performance of a battery cell through the combination of a modified Newman Pseudo 2-Dimensional model and a three-electrode experimental apparatus. To assess the capability of the method, we compare model results with experimental data for a lithiated graphite and lithium nickel manganese cobalt oxide system. The model is applied to simulate the electrochemical and transport processes within the battery cell to predict the negative electrode potential and positive electrode potential with respect to a lithium iron phosphate reference electrode, as well as the terminal voltage. We also provide a commentary on the validity of the fitted parameters governing transport at the electrode level.

In this study, the possibility to characterize the electrochemical characteristics of the particle-polymer interface in dual-phase electrolytes by measuring the contact potential difference with high local resolution is demonstrated. Two different polymer electrolytes, polyethylene oxide (PEO) and poly[bis-2-(2-methoxyethoxy)-ethoxyphosphazene] (MEEP), were investigated in combination with lithium ion conductive Li₇La₃Zr₂O₁₂ (LLZ) particles and two different mixed ionic-electronic conductive ceramic particles: uncoated and carbon coated LiFePO₄ (LFP) as typical cathode material and uncoated Li₄Ti₅O₁₂ as typical anode material. A distinct Volta potential gradient between the particles and the polymer was observable in all cases, except when no lithium salt was present within the polymer matrix. The measured potential gradients can be explained in terms of a contact potential between the polymer electrolyte and the ceramic electrolyte. A more negatively charged space charge layer around LFP particles in PEO matrix and around LLZ particles in MEEP can be explained by enrichment of salt anions in direct vicinity of the particle. Electrochemical characterization with impedance spectroscopy showed an increased conductivity for addition of LFP for PEO while the addition of various particles in different concentrations showed no effect on the conductivity of MEEP. The lithium transference number was unaffected by particle addition for all samples.

Pre-lithiation plays an increasingly significant role for high-energy Li-ion batteries (LIBs) since it can improve the energy density by compensating the Li loss during the initial cycle. The pre-lithiation related research so far has been focused on the development of materials and methods of pre-lithiation but has lacked theoretical and mathematical descriptions to illustrate the relationship between pre-lithiation and energy density. In this contribution, a series of mathematical formulas are derived to describe the gravimetric and volumetric energy densities of LIBs with pre-lithiation, by which the effects of the important parameters, e.g. the Coulombic efficiencies (CEs) of anode, the capacities of Li sources, etc., on the energy densities are well demonstrated. Then, the developed theory and mathematical formulas are applied to practical LIB systems, i.e. the cell using Li nickel manganese cobalt oxide (NMC) as a cathode and silicon-carbon (Si–C) composite as an anode, to identify possible energy density improvement after pre-lithiation. These systematic formulas with great universality have the potential to give significant guidelines for future studies on the pre-lithiation methods and be useful tools for the design of high energy LIBs with imperfect CEs from fundamental and practical perspectives.

Li₁₀GeP₂S₁₂ (LGPS) is a superionic conductor that has an ionic conductivity matching conventional liquid electrolytes (10⁻³ S cm⁻¹) and thus shows exceptional potential to fulfill the promise of solid-state Li metal batteries. Conventional mechanical die pressing of LGPS powder into pellets for electrochemical testing can result in large porosity, low density, and large grain boundary resistance at the solid-solid interface with the electrodes which greatly decrease the performance of LGPS, in addition to poor mechanical stability of such pressed pellets. We demonstrate the use of hot pressing to fabricate of LGPS pellets using commercially available powder. We obtain pellets that are the most dense, and accordingly have the highest ionic conductance, at 150 °C. XPS demonstrates there is no chemical degradation of the LGPS powder during the hot pressing process.

Single-crystal lithium-nickel-manganese-cobalt-oxide (SC-NMC) has recently emerged as a promising battery cathode material due to its outstanding cycle performance and mechanical stability over the tradional polycrystalline NMC. It is favorable to further increase the grain size of SC-NMC particles to achieve a higher volumetric energy density and minimize surface-related degradations. However, the preparation of large-size yet high performance SC-NMC particles faces a challenge in choosing a suitable temperature for sintering. High temperature promotes grain growth but induces cation mixing that negatively impacts the electrochemical performance. Here we report a temperature-swing sintering (TSS) strategy with two isothermal stages that fulfils the needs for grain growth and structural ordering sequentially. A high-temperature sintering is first used for a short period of time to increase grain size and then the reaction temperature is lowered and kept constant for a longer period of time to improve structural ordering and complete the lithiation process. SC-LiNi_0.6Mn_0.2Co_0.2O₂ materials prepared via TSS exhibit large grain size (∼4 μm), a low degree of cation mixing (∼0.9%), and outperform the control samples prepared by the conventional sintering method. This work highlights the importance of understanding the process-structure-property relationships and may guide the synthesis of other SC Ni-rich cathode materials.

Herein, NASICON-type Li_1.15Y_0.15Zr_1.85P₃O₁₂ glass ceramics (a-LYZP) were synthesized from amorphous materials. Compared with samples prepared by the solid-state reaction (s-LYZP), a-LYZP showed a higher total ionic conductivity of 7.0 × 10⁻⁵ S cm⁻¹ at 298 K and improved inter-particle contact. The structure of this glass ceramic effectively reduced the resistance of the Li_1.15Y_0.15Zr_1.85P₃O₁₂. In the temperature range 263–298 K, the activation energy of a-LYZP was 0.43 eV, which was smaller than that for s-LYZP (0.63 eV). Rietveld analysis of XRD patterns suggested that the longer a-axis and larger unit lattice volume of a-LYZP prevented phase change from rhombohedral to triclinic.

Binder-free and flexible oxygen-vacancy CeO₂@C core–shell nanocomposites directly anchored on carbon cloth (CC) are prepared via a simple two-step process, in which CeO₂ nanoparticles are hydrothermally fabricated and mixed with polyvinylpyrrolidone (PVP) composites, subsequently, as-formed CeO₂@PVP composites coated on CC are calcined at 700 °C. The morphologies, structures and electrochemical properties of as-obtained CeO₂@C nanocomposites are studied by SEM, HRTEM, XRD, XPS and electrochemical techniques, respectively. The CeO₂@C nanocomposites are composed of the CeO₂ core with diameter of about 10 nm and the carbon shell with thickness of about 1.5 nm. The electrochemical results reveal that the CeO₂@C nanocomposites show a wide electrochemical active window of −1.0 ∼ 0.8 V and a specific capacitance of 141.56 F g⁻¹ at 1 A g⁻¹ in 1.0 M Na₂SO₄ electrolyte. In addition, an asymmetric supercapacitor (ASC) assembled with CeO₂@C and poly(3,4-ethylene dioxythiophene) (PEDOT) can work in the wide operational voltage region of 2.0 V and deliver the energy density of 11.12 Wh kg⁻¹ at 2000 W kg⁻¹. The present study indicates that the CeO₂@C will have a greater advantage in terms of energy density for CeO₂ and its carbon-based composites supercapacitor electrodes.

The application of layered oxide compounds as cathode materials for sodium-ion batteries is considered a promising direction for the development of high-energy Na-ion batteries. However, despite many efforts, practical implementation of such electrodes is still challenging, mainly due to structural and surface instabilities associated with the high operating voltage of these cathodes. One of the most effective ways to mitigate these undesirable phenomena is the use of atomic layer deposition (ALD) to form a Nano-sized protective layer on the electrode surface. Application of ALD treatment results in increased electrode stability by preventing irreversible interactions between the electrolyte and cathode material. In search of optimal coating formulations, the effect of various ALD coatings viz. sodium-aluminate, lithium-aluminate, and alumina on the electrochemical performance of Na-NCM cathode synthesized by ion-exchange method. While the initial capacity loss attributed to oxygen release was significantly suppressed in all coated samples, better stability was observed for Na_xAl_yO_z coating. The stabilization mechanism of the Na_xAl_yO_z coating further investigated by XPS, XRD, and TEM revealed improved surface properties that prevent irreversible oxygen loss and migration of manganese from the electrode bulk toward the surface.

Imparting high energy density to already power dense capacitor leads to hybrid supercapacitor (SC), which is most sought after in automobile, heavy-duty electronics application, and internet of things. The hybrid SCs with lithium or sodium ion chemistry demand organic electrolytes for their operation, which is environmental unfriendly and poses fire-hazard. As an alternative, here we report a low cost and highly safe energetic hybrid SC based on zinc-ion chemistry operated in 3 M ZnSO₄ with high surface area (1018 ± 4 m² g⁻¹) hierarchical porous carbon cathode material derived from the Tamarindusindica seeds (ACTS-800), a bio-source. The hybrid SC demonstrates a maximum energy density of 127 (± 3) Wh kg⁻¹ (254 μWh cm⁻²) at 0.1 A g⁻¹ and power density of 7920 (± 24) W kg⁻¹ (15.84 mW cm⁻²) at 10 A g⁻¹. Besides having excellent power/energy density values, ∼ 100% capacity retention over 5000 galvanostatic charge/discharge cycles was observed. The most interesting feature of this SC is its low open-circuit voltage decay (34% in 60 h) and low leakage current density (11 mA g⁻¹), which allows it to hold charge for longer duration qualifying it as one of the best aqueous SC known in the literature.

Energy security and green energy are paving way for entire globe to adopt battery based ESS and EV. Online monitoring of battery parameters namely capacity and impedance are crucial to get better performance and life from the system. Impedance is a complex parameter comprises of ohmic, charge transfer and diffusion components. The effective impedance value differs depending on the measurement methodology and data accusation speed. DC method is generally used in the field due to simplicity and cost effectiveness. The present study adopts DC current interruption method for measuring impedance of 12.8 V/10 Ah, LFP/C battery. The voltage recovery and relaxation segment were used to derive impedance value at various SoC's. First using electrochemical theory, it was proved that only diffusion is operating after current interruption when data is monitored at 1 s interval. The diffusion resistance changes not only with SoC but also with mode of operation i.e., charge vs. discharge. An empirical model was proposed taking care of three forces namely voltage gradient, repulsive force between lithium atom in graphene layer and Van der Waal's force between graphene layers. The impact of the diffusion resistance on BMS is highlighted. It is suggested that the study can be used for monitoring ageing and calendaring life of battery, deducing the relationship between raw material and design parameter to performance of the battery.

The evaluation of the materials performance for applications in pressurized water reactors (PWRs) primary water environment are often conducted in either low pressure superheated hydrogenated steam or in supercritical hydrogenated water in order to accelerate the pressurized water stress corrosion cracking (PWSCC) mechanism and reduce experimental time. The high temperature accelerates SCC initiation, which is typically slow under real primary water conditions. However, both in hydrogenated steam and in supercritical hydrogenated water, it is important that the material attains environmental conditions and oxidizing potentials that are relevant to a primary water environment, so that the same PWSCC initiation mechanism operates. The aim of this paper is to establish a thermodynamic equivalence between laboratory systems, namely low pressure superheated hydrogenated steam and supercritical hydrogenated water, and the PWR primary water environments. Experimental data obtained from different sources in the literature are used to obtain thermodynamic relationships as a function of temperature and media. The applicability of these correlations is shown and discussed with examples, and equivalence charts have been generated for practical selection of experimental conditions.

With the aim to open a new window into corrosion processes this paper presents respirometric methods for real-time in situ monitoring of corrosion rates under immersion conditions. With these techniques, sensitive, non-destructive corrosion rate measurements are possible on basically all metals and alloys. Different methods are presented that enable to monitor HER, ORR or both reactions simultaneously based on the amount of evolved H₂ or the amount of consumed O₂ by volumetric, manometric and sensor-based approaches. Various research examples are presented, demonstrating the benefits and limitations of the different approaches. For Mg alloys, besides HER, ORR plays a role in the cathodic reactions and a good correlation of the total cathodic charge with mass loss was obtained. H₂ dissolution into the electrolyte was identified as an important factor. The results obtained for Zn immersion corrosion in intermittent-flow and flow-through respirometric experiments suggest that the ORR mechanism leads to the generation of stable H₂O₂ under these conditions. As a result, the effective number of exchanged electrons for one O₂ molecule was found to be in between two and four. The here introduced respirometric techniques allow new insights into corrosion mechanisms, in addition to enabling real-time monitoring of corrosion.

An aluminium-samarium binary library with a varying Sm concentration between 4 to 14 at.% was produced using a thermal co-evaporation technique. Morphological and crystallographic characterization of the parent metal alloys revealed compositionally dependent surface structure and atomic arrangements. Grains resembling pure Al on the surface slowly disappeared with increasing Sm content and above 8 at.% Sm nucleation of the AlSm₂ intermetallic phase was observed. Scanning droplet cell microscopy was used for a comprehensive electrochemical characterization along the Al-Sm compositional gradient. Anodic oxide formation under high field conditions was discussed for alloys below the compositional threshold of 8 at.% Sm. Above this threshold a continuous increase of Sm dissolution during anodization with increasing Sm concentration was proven by inductively coupled plasma optical emission spectroscopy. Coulometry followed by EIS allowed mapping of the oxide formation factors and oxide electrical permittivity as material constants for single Al-Sm alloys. A small increase of both material constants for alloys below the compositional threshold described the Sm contribution to the anodization process. An apparent enhancement of their values at alloys above the threshold was directly attributed to the increased Sm dissolution rates reaching values of 2 ng cm⁻² s^–1 at 12 at.% Sm.

Basic electrochemical studies of coordination complexes between cupric ions and simple amino acids as ligands (L), namely glycine, alanine and valine, have been carried out to provide insight in the effect of complexation on Cu²⁺ discharge electrochemistry. The results show that there are strong differences in their cyclic voltammograms, despite the similarities in coordination equilibrium, central atom d electronic structure and inner sphere coordination distances (verified by chemical equilibrium quantification, UV spectroscopy and EXAFS). Evidence of mass transport limitations by diffusion of the neutral CuL₂ complexes in solution, and cuprous species generation on the electrode during copper electrodeposition was found, both of which proved to be the main phenomena accounting for the different electrochemical behaviour previously mentioned. Voltammetric studies also showed that, surprisingly, cuprous species are produced not only at the onset of copper electroreduction but at more cathodic potentials. Furthermore, results suggest the existence of a cuprous compound layer beneath the metallic copper deposit. The data gathered in this investigation, leads to the conclusion that the bigger molecular size and organic nature of the ligands induce unexpected processes on the copper electroreduction mechanism.

The effect of Cu(I) ions on electrodeposition of aluminum from AlCl₃-BMIC (AlCl₃-1-butyl-3-methylimidazolium chloride) ionic liquid was investigated. The cyclic voltammetry and cathodic polarization analyses showed that Cu(I) ions obviously decreased the nucleation overpotential of Al and promoted the reduction reaction of Al (III). The analysis of thechronoamperometric transients indicated that the presence of Cu(I) does not change the nucleation and growth mode of Al deposition, but affects nucleation rate. Besides, the addition of Cu(I) slightly decreased the cathodic current efficiency (CE), increased the power consumption (PC), and reduced the purity of Al deposit. X-ray diffractogram revealed the presence of Cu(I) ions in electrolyte affected the preferred orientations of the electrodeposited Al by promoting the growth of (220) plane. SEM images showed that the grain of the Al deposit was refined with the increase of Cu(I) ions.

The electrodeposition of Fe–Al alloy in AlCl₃–NaCl–KCl–FeCl₂ quaternary molten salts was investigated by potentiostatic electrolysis to prepare Fe–Al alloy film with a thermoelectric conversion function. In the AlCl₃–NaCl–KCl–FeCl₂ molten salts with an AlCl₃/FeCl₂ mole ratio of 200 (FeCl₂: 32.6 mmol l⁻¹), the electrodeposited Al formed a solid solution with Fe in the potential range from 0.5 to 0.2 V vs Al(III)/Al and formed the intermetallic compound of Fe₃Al at the potential of 0.1 V. Fe–Al alloys containing 0.8–34.5 mol% Al were obtained by controlling the AlCl₃/FeCl₂ mole ratio (FeCl₂ concentration) in AlCl₃–NaCl–KCl–FeCl₂ molten salts and the applied potential in the potential range from 0.2 to −0.1 V vs Al(III)/Al. The Fe–Al alloy films prepared in the present study exhibited the p- or n-type thermoelectric conversion, depending on their composition.

The fundamental kinetic parameters of corrosion product ions (Fe, Ni and Cr ions) are of significant importance to understand the corrosion mechanisms of the structural materials in the molten salts. In the present study, the fundamental data of Fe²⁺, Ni²⁺, Cr²⁺ and Cr³⁺ (diffusion coefficient D, exchange current density i₀, charge transfer coefficient α, limiting current density i_L and standard rate constant k⁰) were measured at different concentrations (1.53 × 10⁻⁶−7.48 × 10⁻⁴ mol cm⁻³) and temperatures (600 °C–800 °C). The values of D are independent of concentrations and follow Arrhenius law with temperature, which descend in the order of ${D}_{C{r}^{2+}}$ > ${D}_{F{e}^{2+}}$ > ${D}_{C{r}^{3+}}$ > ${D}_{N{i}^{2+}},$ with values ranging from 0.94 × 10⁻⁵ to 3.31 × 10⁻⁵ cm² s⁻¹. Both i₀ and k⁰ depend on the temperatures, which also follow Arrhenius law. The values of the estimated k⁰ descend in the order of ${k}_{C{r}^{2+}}^{0}$ > ${k}_{F{e}^{2+}}^{0}$ > ${k}_{N{i}^{2+}}^{0}$ > ${k}_{C{r}^{3+}}^{0},$ which range from 1.88 × 10⁻⁵ to 9.06 × 10⁻⁴ cm s⁻¹.

The innovative three-dimensional (3-D) nanocrystals constructed by 1-D stalactite-like branches with a diameter of 107 ± 27 nm and a varied length of a few hundred nanometers were successfully synthesized via a facile tri-block copolymer assisted chemical approach. The highly-branched Ag nanocrystals were applied as promising electrical conducting fillers to form PVP-based composites for electromagnetic interference (EMI) shielding applications. In comparison with the dense Ag-flakes based film, the slip-coated sponge-like Ag film exhibits a comparably-high electrical conductivity after annealing and a stably-excellent EMI shielding effectiveness of 47−53 dB over the frequency from 500 MHz to 10 GHz.

In this study, a polyethylene glycol-based organic additive, with quaternary ammonium cation functional groups linked to a naphthalene rings at both ends was synthesized, for through silicon via (TSV) filling. The synthesized additive strongly suppressed Cu electrodeposition under convection and successfully bifurcated the deposition surface of TSVs into active and passive regions, allowing defect-free TSV filling. However, there was a variation in TSV filling uniformity depending on the additive chain length. The chain length was adjusted using polyethylene glycol of various molecular weights as a starting material for the additive. The electrochemical investigation revealed that the chain length was related to the re-adsorption rate during Cu electrodeposition, which is critical in TSV filling. At the optimal chain length, uniform and defect-free bottom-up TSV filling was successfully achieved and TSV filling time was reduced to 500 s.

The traditional lead-based anodes used in industrial electrolysis process trigger the high energy consumption, lead pollution and hazardous anode slime discharge. In this work, an original undecorated Polyacrylonitrile (PAN)-based carbon fiber was employed as anode material (CF anode) to evaluate its electrochemical performance and feasibility, aiming at fundamentally reducing the energy consumption and pollution emissions for the manganese electrolysis. The results shown that the CF anode exhibited excellent electrocatalytic activity and delivered a current density of 350 A m^–2 at an overpotential decreased by 112 mV for oxygen evolution reaction (OER) compared with commercial lead-based alloy anode (Pb anode). We also found CF anode exhibited favorable performance with average current efficiency increased by 4.30%, energy consumption decreased by 8.36%, and a noteworthy abatement of anode slime by 80% compared with Pb anode in MnSO₄ electrolyte. Additionally, the growth of manganese dendrites on the cathode edge which directly affected the electrolytic efficiency has also been effectively controlled and the possible mechanisms were also discussed. This work displayed the excellent electrocatalytic effect of CF anode serviced as a promising candidate for green and efficient electrolysis process.

The global need for freshwater rapidly drives the development of emerging and efficient freshwater-production methods such as capacitive deionization (CDI). To allow the CDI technique to continue to grow, simulations can be important for tractably describing, predicting, and optimizing the desalination processes. Amongst the disparate simulation tools available, the Randles-circuit model is widely used in electrochemical measurements but its simplified structure limits its use for wider CDI operations. Thus, we herein describe a systematic stepwise process for widely developing CDI models, and as a proof-of-concept, transform the core Randles circuit into an extended Randles circuit (ERaC) that is highly relevant for CDI systems. Experimental data from the literature extensively verify that the ERaC model accuracy now describes charge storage, charging rate, ion adsorption, and current leakages for a variety of structural and operational parameters, such as asymmetric electrodes, different ion concentrations, and the applied voltage. In conclusion, this developed stepwise process can systematically and effectively create, enhance, and expand CDI models. Thus, researchers will embrace this method of model development, and benefit from the broad usefulness of the proposed ERaC model for a wide range of CDI operations.

Electrochemical discharge machining (ECDM) utilizes the principle of thermal melting and chemical dissolution for machining "non-conductive" materials like ceramics, glass, silicon wafers. These materials exhibit colossal applications in the fields of MEMS and lab-on-chips. Since its first demonstration, different aspects of the ECDM process have been studied for improving its efficiency. However, only a few numbers of studies were delineated to comprehend the mechanism of gas film and effective parameters for its stability concerning the machining repeatability. This paper comprehensively reviews the gas film mechanism concentrating on bubble formation, bubble adherence, bubble amalgamation, departure and breakdown behavior. The parameters for controlling the gas film stability such as voltage, current, gas film formation time, gas film thickness, surface tension, viscosity, surface topography, magnetic field, tool electrode's motions and material, are also likewise discussed. Moreover, research findings on ECDM performance based on discrete input parameters is also covered and presented. It was concluded that stabilized gas film significantly influences machining efficacy and can be achieved effectively by controlling the electrolyte's electrochemical properties, tool electrode shape and motions. Further, the paper underlines the future possibilities that may have the potential to enhance the ECDM performance.

This study examines the thermodynamic, kinetic, and spectroscopic behaviors of Cr, Fe, Co, and Ni to lay the foundation to develop an electrochemical decontamination process for radioactive metallic wastes. Cyclic voltammetry combined with numerical fitting was used to obtain the formal potentials, standard rate constants, and diffusion coefficients of redox reactions, Cr(II)/Cr, Fe(II)/Fe(0), Co(II)/Co(0), and Ni(II)/Ni(0), in LiCl-KCl at 773 K. The order of the diffusion coefficients was 10^–5 cm² s⁻¹, which agrees with the existing data and the standard rate constants showed similar values with the order of 10^–3 cm s⁻¹ between experimental correlations and numerical fitting. UV–vis-NIR absorption spectroscopy of the metallic constituents was performed to derive molar absorption coefficients and molecular structures in molten salt media. In particular, the redox reaction of Cr(III)/Cr(II) was investigated by chronoabsorptometry to obtain its formal potential, the number of electrons, and the diffusion coefficient of Cr(II). The obtained reaction properties were used in the numerical modeling of the ECE reaction in a Ni and Co binary system to reproduce the experimental results of CV, revealing the presence of chemical reaction. The findings of this study will be directly used for designing a decontamination process to produce acceptable waste forms and reduce waste volume.

Electrochemical behaviour of aluminium ions from the Pt/γ-Al₂O₃ spent catalyst in the eutectic [LiF (63.6 wt.%)–AlF₃ (36.4 wt.%)]_eutectic−5 wt.% CaF₂ melt was studied by the means of cyclic voltammetry, chronopotentiometry and chronoamperometry methods. Tungsten rod (diameter 2 mm) was used as a working electrode. The XRD method was used to study the composition of melt collected near the working electrode and the spent catalyst. The aluminium reduction kinetics was studied concerning varying parameters like spent catalyst content in the melt and the temperature. The reduction of Al³⁺ ions on the tungsten electrode changed from diffusion-controlled to quasi-reversible process. The charge transfer coefficient and the diffusion coefficient were calculated from the data obtained from the above-mentioned methods. The estimated diffusion activation energy was 117.85 kJ.mole⁻¹.

Hydroxide exchange membrane fuel cells (HEMFCs) are a potentially lower-cost hydrogen fuel cell technology; however, ambient levels of CO₂ in air significantly reduce HEMFCs' performance. In this work, we demonstrate an electrochemically-driven CO₂ separator (EDCS) which can be used to remove ambient levels of CO₂ from air upstream of the HEMFC stack in fuel cell vehicles, protecting it from CO₂-related performance losses. The EDCS operating window was explored for current density, anode flow, and cathode flow with respect to its impact on CO₂ separation performance. Additionally, gas-phase mass transport was improved by selecting flow fields and gas diffusion layers conducive to the EDCS operating regime. The use of a carbon-ionomer interlayer at the cathode was explored and improved CO₂ removal performance from 77.7% to 98.2% at 20 mA cm⁻². An analytical, 1-D model is used to explain the experimental observations and design improvements. A single-cell, 25 cm² EDCS using the aforementioned improved design demonstrated greater than 98% CO₂ removal at a cathode flow rate of 1300 sccm for 100 h with 2.7% hydrogen stack consumption.

I propose a new noise reduction concept for FFT (Fast Fourier transform) Electrochemical Impedance Spectroscopy (EIS) using the ergodic hypothesis. Instead of a conventional time-averaged impedance, an ensemble average of impedances with slightly different frequencies (quasi-ensemble-median value) is defined as an experimentally obtained appropriate impedance. This approximation is acceptable in some conditions and will contribute to faster measurement. By applying this method to a hydrogen fuel cell, a high-accuracy measurement of fuel cell impedance between approx. 0.38 Hz and 10 kHz was performed within three seconds. The results from FRA and the proposed FFT method in the steady state were almost the same. The averaged percentage error throughout the whole of the measured frequencies was around ±1%, and the maximum difference was around −6% at approx. 1 Hz.

Extensive research efforts have been made on platinum group metal (PGM)-free electrocatalysts for oxygen reduction reaction, with the aim of lowering the cost hurdle of acidic polymer electrolyte fuel cells (PEFCs). While the activity and durability of PGM-free catalysts have been boosted, the PEFC performance relies also on the electrode structure at the membrane electrode assembly (MEA) level. However, the extensive number of variables involved in the electrode preparation as well as in the fuel cell testing, poses severe challenge to compare results obtained in different labs. In this work, we systematically investigated the effect on performance of some operational variables, such as polarization curve scan direction, and gas flow rates. Additionally, anodic Pt catalyst loading and cathodic PGM-free catalyst loading were investigated. The tests were done in a differential cell hardware using a commercial Fe-N-C catalyst at the cathode. The results indicate that PGM-free catalyst loading and air flow rate on the cathode are impactful variables. Polarization curve scan direction (also considering averaging process on multiple consecutive scans), anode Pt loading as low as 0.035 mg cm⁻², as well as H₂ and O₂ flow rates above 300 scm³ min⁻¹ have negligible impact on the performance of PGM-free based MEAs.

Electrochemical hydrogen compression is seen as a promising alternative to mechanical compression in the context of power-to-gas plants. It can be carried out either as direct co-compression in a water electrolyzer (WE) or via a separate electrochemical hydrogen compressor (EHC). This study analyzes the specific energy demand of different hydrogen generation and compression pathways using WEs and EHCs, both based on proton exchange membrane (PEM) technology, for pressures up to $1000\,{\rm{bar}}$. The energy demand is systematically investigated as a function of design parameters such as pressure, current density, temperature and membrane thickness and presented in overpotential-specific and gas-crossover dependent shares. The analysis reveals intrinsic differences in the compression behavior of WEs and EHCs. In the EHC, permeated hydrogen is simply re-compressed back to the cathode. In the WE, instead, water has to be split again to compensate for the hydrogen loss, causing energetic disadvantages with increasing hydrogen pressure. Moreover, using an EHC enables design parameters to be optimized separately regarding hydrogen generation and compression. Therefore, at low current densities, compression via EHC is already favorable to co-compression via WE for pressures above $4\,{\rm{bar}}$. With increasing current density, however, this intersection point shifts up to pressures above $200\,{\rm{bar}}$.

Developments of the porous transport layers (PTLs) in recent years resulted in significant performance improvements in polymer electrolyte water electrolyzers (PEWEs). One of the milestones of the material design was the integration of a microporous layer (MPL) on sintered titanium PTLs. Utilizing high-resolution neutron imaging, the water and gas distribution in the multi-layered porous transport media (ML-PTL) was probed at various current densities (up to 4 A cm⁻²) and pressure conditions up to 8 bar, using a series of four materials, differing in MPL morphology. The water and gas distribution measured is greatly affected by the presence of an MPL. While in the bulk of the PTL, the gas accumulation is increased in the presence of an MPL, in the MPL itself more water is retained. The finer the MPL structure, the higher the liquid saturation. It is observed that the two-phase flow in the MPL has minor influence on the performance of the cell even though the gas accumulation at the CL interface is greatly reduced. The improvements, therefore, appear to be related to the CL and MPL interaction on sub-micron scale and microstructure effect on catalyst area utilization.

The formation of extended metal thin films (<5 nm) or monolayers on oxide surfaces, for applications in (electro-)catalysis, has never been achieved due to the high interfacial energy of the metal/oxide interface that always results in a 3D growth of the deposited metal. To realize 2D growth, the outermost surface of the oxide must be reduced prior to metal deposition in the same system. Here, we demonstrate that the polyol method, typically used for metal nanoparticles synthesis, can be used for the reduction of oxide thin films. The reduction of the oxide layer upon heating in ethylene glycol was electrochemically monitored in situ by measuring the open circuit potential and confirmed by cyclic voltammetry and near ambient pressure X-ray photoelectron spectroscopy. The reduction of oxide thin films could be verified for nanoparticles of Sn, Ni and Sb-doped SnO₂ in accordance with thermodynamic calculations. This method will enable the formation of metal thin films and monolayers on oxide substrates for applications in (electro-)catalysis.

Low temperature direct ammonia fuel cells (DAFCs) are attractive for transportation applications. The primary obstacle to their commercial use is their low performance and poor durability. In the present work, we focus on improving DAFCs performance and durability by examining the effect of operating backpressure and oxygen reduction reaction (ORR) catalysts such as Acta 4020, Pd/C and Pt/C. DAFCs with Acta 4020 cathode can reach a peak power density of 390 mW cm⁻² which is among the best reported performance, but they can be operated for a period of 11 h at 300 mA cm⁻². DAFCs with Pd/C cathode offer a moderate performance with a peak power density of 304 mW cm⁻², but has a much improved durability - a continuous operation for up to 36 h with a slow decay rate of ∼1 mV h⁻¹ at 300 mA cm⁻². In addition, the degradation pathways for DAFCs with Pd/C cathode are probed by characterizing the initial and final electrodes by XPS, suggesting that cathodic Pd dissolution occurs during the durability test.

A 5/15 kW-class reversible Solid Oxide Cell (rSOC) system was developed and experimentally investigated at the Forschungszentrum Jülich GmbH. The main component of this system is the well-established Jülich Integrated Module, which consists of four 10-layer SOC sub-stacks with an active cell area per layer of 320 cm². The other necessary system components, such as the evaporator, condenser and blowers are compactly arranged in the vicinity of the Integrated Module. The system's total operation time was more than 9000 h, in detail 2607 h in fuel cells, 6043 h in electrolysis and 448 h in hot standby mode. In fuel cell mode, a power of 5374 W_DC at 0.5 A cm⁻² at a fuel utilization of 97.3% was delivered, which resulted in a DC electrical system's efficiency of 62.7% (LHV). Furthermore, in electrolysis mode, a power of −14347 W_DC was consumed at 0.89 A cm⁻². At this operating point, the system's DC efficiency reached 70% at a steam utilization of 85%.

Long-term stability tests are performed at 800 °C on Pr₂NiO_4+δ air electrodes by use of a symmetrical button cell with Ce_0.9Gd_0.1O_1.95 as solid electrolyte. The experiments are carried out by means of electrochemical impedance spectroscopy and current-voltage measurements with and without current load under dry and humid conditions in the presence of a chromium source. Chromium poisoning of Pr₂NiO_4+δ air electrodes is investigated for periods of several hundred hours at 30% relative humidity. In order to separate the influence of anodic and cathodic electrode polarization on Cr-deposition, measurements are conducted using a Pt-reference electrode. The electrode performance is found to remain fairly stable under dry conditions, even when a current is drawn. However, after volatile Cr-species in a humid atmosphere are introduced, the cell performance starts to deteriorate and the polarization resistance contribution of the SOFC cathode increases significantly. After several thousand hours, the electrodes are analyzed by means of analytical electron microscopy. Detailed post-test analyses provide evidence for a correlation between the extent of Cr-deposition and electrode degradation in SOFC as well as SOEC mode. Based on these findings, enhanced resilience of Pr₂NiO_4+δ against Cr-poisoning in SOEC mode can be established.

The separator is a critical component for the performance of alkaline water electrolysis as it ensures the ionic contact between the electrodes and prevents the product gases from mixing. While the ionic conductivity of the separator affects the cell voltage, the permeability of the dissolved product gases influences the product gas impurity. Currently, diaphragms are used as separators, the pore system of which is filled with the electrolyte solution to enable the exchange of ions. The breakthrough of the gas phase can be prevented up to a specific differential pressure. A drawback of diaphragms is the requirement of a highly concentrated electrolyte solution to maintain a high ionic conductivity. The usage of anion-exchange membranes could solve this problem. However, the long-term stability of such materials remains unproven. This study compares two pre-commercial diaphragms, an anion-exchange membrane, and an ion-solvating membrane with the state-of-the-art diaphragm Zirfon^TM Perl UTP 500. Besides physical characterization, the material samples were evaluated electrochemically to determine the ohmic resistance and the product gas impurities. The results show that the thinner diaphragm outperforms the reference material and that polymer membranes can compete with the performance of the reference material.

Understanding the O₂ permeation resistance and its dependence on the material structure in an ionomer thin film on a platinum surface is vital for the electrocatalyst performance at low platinum loading in proton exchange membrane fuel cells. In this study, the ionomer film nanostructure and O₂ permeation resistances and routes at different water contents are investigated using molecular dynamics (MD) simulations. The MD model is reasonably validated, and simulation results show that the ionomer film contains three regions according to their structures. The dense layer with a tight arrangement of perfluorosulfonic acid (PFSA) chains in the ionomer-Pt interface (Region I) has a density ∼1.5–2 times higher than that in the bulk-like ionomer (Region II). The overall O₂ permeation resistance increases with decreasing water content and the ionomer-Pt interface plays a dominant role in the O₂ resistance due to its high-density structure. The study on O₂ permeation routes shows that O₂ mainly permeates via the water sites in the ionomer-Pt interface and thus a lower resistance is present at higher water contents. In the bulk-like ionomer, O₂ mainly permeates via small cavities at low water contents and the large interfacial areas between water clusters and PFSA frameworks at high water contents.

This study reveals the source of discrepancy between the lifetime of oxygen evolution reaction (OER) catalysts determined by rotating disk electrode (RDE) measurements vs that obtained in a membrane electrode assembly (MEA) in an electrolyzer. We show that the accumulation of microscopic oxygen bubbles in the pores of the electro-catalyst layer during the OER takes place in both RDE and MEA measurements. However, this accumulation was found to be much more significant in RDE measurements, where the shielding of almost all of the catalyst active sites by gas bubbles leads to rapid performance deterioration. This decrease in performance, albeit largely reversible, was found to also induce irreversible catalyst degradation, which could be avoided if the accumulation of microscopic bubbles is prevented. This type of artefact results in vastly under-estimated catalyst lifetimes obtained by RDE experiments, resulting in values that are orders of magnitude shorter than those obtained using MEA measurements, and a hypothesis for this discrepancy will be proposed. Therefore, electrochemical cells with liquid electrolytes are not reliable for OER catalyst lifetime determination.

This was paper 236 presented at the Atlanta, Georgia, Meeting of the Society, October 13–17, 2019.

Understanding the degradation mechanism of Fe/N/C cathode catalysts in proton exchange membrane fuel cells (PEMFCs) is important. We studied the degradation of an Fe/N/C catalyst prepared from polyimide nanoparticles in an in situ cell by X-ray absorption spectroscopy (XAS). This technique enables real-time monitoring of the Fe species during a fuel cell operation. The Fe K-edge absorption spectra were recorded during the continuous operation of the fuel cell. Initially during the fuel cell operation, the Fe species were atomically isolated and their valence state was found to be 3+. The spectra gradually changed during the first few hours of operation, suggesting the dissolution of the Fe species from the active sites, whereas the fuel cell performance continued to decrease during the eight hours of operation. The demetallation from the FeN_x centers during the first few hours has been successfully monitored in real time, while the remaining FeN_x centers seem to be stable in the following fuel cell operating condition.

An improved stochastic reconstruction method for a gas diffusion layer (GDL) of proton exchange membrane fuel cell is developed to promote the accuracy in evaluating effective gas diffusivity. Carbon fibers are generated using stochastic algorithm within a representative element volume. Structural characteristics, porosity distribution and fiber orientation distribution are set as constraints in reconstructing the microstructure. Morphological opening of image processing with structuring element is employed to add binder and polytetrafluoroethylene (PTFE), with disk and sphere binder configurations. Pore-scale simulations are subsequently carried out to compute the anisotropic, effective gas diffusivities of these reconstructed GDLs. Simulation results show that the reconstructed GDL with binder and PTFE produces significant decrease of the effective gas diffusivity. The disk-shape binder appears to match the real GDL geometry visually, and the predicted effective gas diffusivity is also in good agreement with the reported experimental data in the literature. This demonstrates the importance of binder and PTFE in GDL reconstruction. Moreover, the correlations of the effective diffusivities in the through-plane and in-plane directions as functions of porosity and volume fraction of binder and PTFE are determined for the reconstructed GDLs.

A metal- and oxidant-free electrochemical synthesis of aryl sulfides was developed through a C–H sulfidation reaction of arenes and disulfides. Compared with traditional organic synthesis methods, this direct electrochemical approach efficiently generates aryl sulfides under catalyst- and oxidant-free conditions with the superiorities of wide substrate compatibility, mild reaction condition and waster free. At room temperature, various aryl thiols could be transformed smoothly in an undivided cell. Based on cyclic voltammetry (CV) and control experiments, the possible reaction mechanism was also proposed. The gram-scale synthesis emphasizes the practicability of this electrochemical strategy.

In this study, a series of M-In_0.2Cd_0.8 s (M = La, Y, Ga, Bi, Pr, Nd and Gd) photocatalyst arrays was effectively screened with an optical fiber under UV–visible light illumination in 0.1 M Na₂SO₄/Na₂SO₃ solution by scanning electrochemical microscopy (SECM). The spot corresponding to the Ga_0.3(In_0.2Cd_0.8)_0.7 s photocatalyst displayed the highest photocatalytic activity among the photocatalyst arrays. The Ga_0.3(In_0.2Cd_0.8)_0.7 s photoelectrode possessed a hexagonal wurzite structure with a bandgap of 2.49 eV. The addition of 30% of Ga could greatly reduce the charge transfer resistance on the surface of the In_0.2Cd_0.8)_0.7 s photocatalyst. The Ga_0.3(In_0.2Cd_0.8)_0.7 s photoelectrode exhibited a flat band position of −0.497 V vs Ag/AgCl and charge carrier density of 1.68 ± 0.15 × 10²² m⁻³. The maximum incident photo to current conversion efficiency (IPCE) value for the Ga_0.3(In_0.2Cd_0.8)_0.7 s photoelectrode was found to be 74% at 400 nm. The enhanced photocatalytic efficiency of the Ga_0.3(In_0.2Cd_0.8)_0.7 s photoelectrode was resulted from improvement the level of visible light energy utilization and decreased charge transfer resistance for photocatalytic reactions under optimum composition.

The electrical conductivity of 0.507KCl–0.493YbCl₃ and 0.5YbCl₃–0.25KCl–0.25NaCl chloride melts with the ytterbium oxide (Yb₂O₃) additions ranging from 0 to 3.15 mol% was measured depending on both the temperature and concentration of Yb₂O₃. The liquidus temperatures of the studied systems containing from 0 to 3.35 mol.% Yb₂O₃ were determined by DSC method and the electrical conductivity measurements. The Yb₂O₃ additions increase the liquidus temperatures of the systems under study. The high-temperature Raman spectra of chloride (YbCl₃–KCl–NaCl) and oxide-chloride (YbCl₃–KCl–NaCl–Yb₂O₃) melts were recorded. In the oxide-chloride melt an additional band was detected in the region of 460 cm⁻¹ corresponding to stretching-vibrations of the Yb–O bond in [OYb₃Cl_n] oxychloride associates. There was no evidence of vibrational bands related to ytterbium oxide. Such changes in the Raman spectrum points to the dissociation of ytterbium oxide and modifications to the local structure of the chloride melt.

TiN and ZrN refractory transition metal nitride nanoparticles (NPs) have recently emerged as an alternative to noble metals in plasmonic applications. However, plasmon-driven photocatalysis by ZrN NPs is largely unexplored. In this study, optical properties, morphology, crystal structure and surface composition of in-house synthesized and commercial ZrN nanoparticles (NPs) are vigorously characterized in order to select the best candidate material for evaluation of activity towards CH₃OH photoelectrochemical oxidation. The photocatalytic activity of TiO₂-supported ZrN NPs is compared to that of TiN/TiO₂ as a function of NP loading and illumination wavelength. Our results indicate that optical properties and photocatalytic activity of ZrN/TiO₂ are strongly affected by ZrN surface oxidation and agglomeration. We found that under visible illumination, both in-house synthesized 17 nm ZrN and commercial 30 nm TiN NPs promote TiO₂ activity for CH₃OH oxidation, while under visible + UV excitation, an inhibition effect is observed. The differences between the TiN/TiO₂ and ZrN/TiO₂ interfaces are discussed and the mechanisms of promotion/inhibition of TiO₂ photocatalytic activity by ZrN and TiN NPs are proposed. Electromagnetic simulations are used to facilitate interpretation of experimental extinctions and photocatalytic activities.

The cleavage of the linkage bonds among the C9 units in lignin molecules via selective oxidation method to obtain small-weight aromatic compounds is an important way to lignin valorisation. In this study, the cleavage pathways of bonds in a lignin model compound, GGE (guaiacylglycerol-β-guaiacyl ether), by the reactive oxygen species (ROS) in situ generated through electrochemical oxygen reduction reaction (ORR) in an aprotic ionic liquid ([BMIM]BF₄) was investigated. The results indicated that when the main ROS was ·OOH, coniferyl alcohol, guaiacol and vanillin were detected as the degradation products which is supposed to be caused by β-O-4 bonds cleavage; Otherwise, when HO₂⁻ was the main ROS, coniferyl alcohol could not be detected and the degradation reaction is believed to be trigerred by C_α-C_β bonds cleavage.

Stinging nettle is a perennial plant from the Urticaceae botanical family. Apart from various biologically active compounds with health-promoting properties, it contains large amounts of titanium, which plays a key role in growing plants. This work focuses on the determination of titanium content in leaves of stinging nettle by adsorptive stripping voltammetry. For this purpose, dry leaves of stinging nettle from three different producers were used to obtain extracts using high pressure microwave-assisted mineralization. The obtained results confirm the satisfactory accuracy of the developed voltammetric procedure and its usefulness for determining this kind of real samples.

Ligand exchange conduction or hopping conduction which means ions move faster than their ligands or solvents, is one of the striking phenomena in electrochemistry. Here, we report a glyme-based electrolyte where ligand exchange conduction takes place. The electrolyte is a concentrated pentaglyme (G5) solution of lithium bis(trifluoromethylsulfonyl)amide (LiTf₂N; Tf = SO₂CF₃) with molar ratio of [G5]/[LiTf₂N] = 1/2. Since a diglyme (G2) solution [G2]/[LiTf₂N] = 1/1 which has the same molar ratio of ether oxygen to Li⁺ ([O]/[Li⁺] = 3) does not show ligand exchange conduction, the glyme chain length may need to be long enough to bridge Li⁺ ions, by which the momentum exchange of Li⁺ ions via solvent molecules is allowed.

Surface potential measurement values of the gas-liquid interface can be ambiguous despite the numerous electrochemical approaches used for quantification of the reported values. Calibration and normalization methods are not standardized, which often undermines the robustness of the reported values. Surface potential instrumentation and data interpretation also varies significantly across literature. Here, we propose a circuit model for an ionizing surface potential method based on the alpha decay of a radioactive americium-241 electrode. We evaluate the robustness of the circuit model for quantifying the surface potential at the air-aqueous interface. We then show successful validation of our circuit model through determination of the surface tension of the air-electrolyte interface with comparison to respective surface tension literature values. This validation reveals the reliability of surface potential measurements using the americium-241 ionizing method. We also report the surface potential difference of the air/water interface to be −0.49 V ± 0.01 V consistent with hydrogens of water pointing toward the air phase.

It is shown for the first time that the deep eutectic solvent, DES, formed by acetylcholine chloride and urea can be successfully used for Ag recovery from the cathode powder of spent silver oxide batteries. This DES performs two important functions namely, as selective leaching liquor to extract Ag(I) ions from the remaining Ag₂O, leaving intact the metallic Ag in the solid phase, and as electrolytic bath for silver electrodeposition onto a glassy carbon electrode or graphite. Using potentiodynamic and potentiostatic electrochemical measurements, it was possible to quantify both: the Ag(I) leaching rate and the concentration of Ag(I) ions leached after 24 h. From this value, it was possible to estimate that about 7% of the original mass of the cathode powder corresponds to Ag₂O and the rest to metallic Ag. Moreover, from potentiostatic current density transients, recorded during Ag electrodeposition, it was shown, for the first time in this DES, that this process occurs via multiple 3D nucleation with diffusion-controlled growth and valuable practical information i.e. the diffusion coefficient of Ag(I) ions in this media was quantified. From scanning electron microscopy images and energy-dispersive X-ray spectroscopy, the morphology and composition of the resulting deposits were characterized.

In this work, the separation and purification of 1,5-Di-O-caffeoylquinic acid (1,5 DCQA) was carried out via column chromatography (ethyl acetate/n-hexane with volume ratio 20/80) from Artichoke (Cynara scolymus L.) head ethanolic extract and characterized with IR, LC/MS, and UV/visible. The electrochemical approach has been used to analyze and detect electroactive compounds in ethanolic extract. Differential pulse voltammetry results indicated that a bioactive and electroactive molecule (1,5-Di-O-caffeoylquinic acid) is the major constituent in the Artichoke ethanolic extract. The analytical parameters are calculated via calibration curve and obtained 7.8 μM and 9.0 μM–1.8 mM for LOD and linear range, respectively. The theoretical and experimental biological assessment has been carried out with molecular docking, 2,2-diphenyl-1-picrylhydrazyl (DPPH), and in vitro antibacterial susceptibility assay. The adsorption peak of DPPH is thoroughly deleted after the addition of Artichoke extract; therefore, its antioxidant activity is achieved approximately 100%. The inhibition zone surrounding the wells indicated that relevant extract has inhibitory function against E. coli (19 mm), S. enterica (21 mm), B. cereus (20 mm), and S. aureus (17 mm) bacterial. The binding affinity values showed that 1,5 DCQA has an inhibitory effect against ROS generation enzymes and bacterial enzymes.

Development of efficient non-precious metals catalysts for the oxygen reduction reaction (ORR) has attracted considerable attention. A composite catalyst based on nickel- 5,10,15,20-tetra(p-thioanisole) porphyrin complex (Ni-TPT-P) and carbon fibres (CF) is here investigated for the ORR. The porphyrin is synthesised by a one-pot multi-step approach. Ultraviolet-visible (UV–vis) and fourier-transform infrared (FTIR) techniques are used to confirm the synthesis of the Ni-TPT-P complex. The metalloporphyrins (Ni-TPT-P) are non-covalently adsorbed on the CF via $\pi -\pi$ stacking interaction. The composite catalyst shows well-defined redox peaks attributed to the Ni²⁺/Ni³⁺ redox couple in O₂-saturated 0.1 M KOH solution. The area under the reduction peak is used to calculate a surface coverage (${\rm{\unicode{x00413}}}$) of 2.43 × 10¹⁵ for the Ni²⁺/Ni³⁺ species on the catalyst surface area. The rotating ring disk electrode (RRDE) technique is used to assess the performance of the catalyst towards the ORR. Key performance indicators such as the onset potential, average number of electrons and ${{\rm{HO}}}_{2}^{-}$ yield are found to be, 0.82 V vs RHE, 3.6 electrons and 22.0% respectively.

SnS₂-sensitized TiO₂ nanotubes were fabricated via anodic oxidation and a successive ionic layer adsorption and reaction process. The prepared SnS₂/TiO₂ composites were used as photoanodes, and the corresponding photocathodic protection effect on 304 stainless steel was studied. The effect of the number of adsorbed SnS₂ molecules on the photocatalytic protection conferred by the SnS₂/TiO₂ composites was also analyzed. The morphology and composition of the samples were analyzed by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The optical absorption properties of the samples were analyzed by ultraviolet-visible diffuse reflectance spectroscopy. The electrochemical properties of the SnS₂/TiO₂ composites were characterized in terms of their open circuit potential, the photocurrent density, the electrochemical impedance spectrum and the current-voltage curve and used to analyze the photocatalytic protection effect. The results show that the SnS₂/TiO₂ composite exhibits higher visible light absorption and offers more photocathodic protection than pure TiO₂ nanotubes. Using SnS₂/TiO₂(6C) as a photoanode reduces the potential of 304 stainless steel to −730 mV.

A highly sensitive label free electrochemical impedance biosensor based on gold nanocrystals (AuNCs) for hepatitis B virus (HBV) detection in blood serum was reported. A functional platform for measuring the geno-biosensor sensitivity for detecting HBV DNA based on AuNCs electrode was materialized. The adjusted morphologies of 50–100 nm beaded AuNCs on the In₂O₃ support layer were materialized and characterized by a field emission scanning electron microscope (FESEM) and a high resolution transmission electron microscope (HRTEM). The bio-sensing measurements were conducted by electrochemical impedance spectroscopy (EIS) approach under redox reactions process. The HBV DNA probe (ssDNA) was immobilized on the AuNCs surface by forming a special bond between ssDNA and gold. The DNA target was diagnosed using ssDNA/AuNCs biosensor through EIS measurements in concentration ranges from 0.1 pM to 0.1 μM with a limit of detection (LOD) of 0.1 fM. The selectivity property of the biosensor was investigated and it could distinctively distinguish the complementary DNA target from the non-complementary DNA, 1-, 2- and 3-mismatch targets. Finally, the capability of the electrode for detection of the HBV in blood serum samples was explored and biosensor showed interesting results in the HBV DNA sensing as a potential candidate for practical applications.

Three N-heterocyclic carbenes (NHCs) are synthesized and their self-assembled monolayers (SAMs) are built up on gold substrate. Electrochemical impedance spectroscopy (EIS) tests show that the NHC-based SAMs exhibit high stability in 0.1 M HCl solution, and the loss of NHC molecules on gold surface is less than 3% after immersion of 32 h. The unsaturated level of heterocyclic moiety has a negligible effect on the stability of NHC-SAMs, which is attributed to the special bonding mechanism between NHCs and gold atom. Theoretical calculations reveal that the bonding of NHC molecule is dominantly contributed by the interaction of the d orbital of gold atom with the molecular orbitals mainly distributing on carbene carbon atom of NHC, such as HOMO-1 (σ1) and HOMO-2 (π1), and the σ-type interaction accounts for the main state of bonding in comparison to the π-type one. Those molecular orbitals distributing on heterocyclic moiety nearly take no part in the bonding, and the interaction of isopropyl substituents on N atoms with gold surface is not observed in this study. In addition, it is confirmed that EIS measurement can both sensitively and quantitatively examine the adsorption and desorption of SAMs on gold surface.

Bi-based catalysts have attracted great attention for efficient electrocatalytic carbon dioxide (CO₂) reduction to formic acid (HCOOH). However, the effect of the growth kinetics of Bi nanostructures on morphology and their catalytic performance has not been studied. Here, we varied the Bi³⁺ precursor concentration in the electrolyte to control the electrochemical growth rate of Bi nanostructures. It was found that the growth rate determines not only the geometric structure but also the microstructure of Bi nanostructures. The slow growth with a low precursor concentration (1 mM) produced Bi nano-sheet (NS) with high crystallinity in (012) preferred orientation. But, the polycrystalline Bi nano-branch (NB) with a larger surface area was formed by a faster growth condition (precursor concentration = 30 mM). As a result, Bi NB achieved a higher FE_HCOOH of 97.1% than Bi NS (FE_HCOOH = 81.5%) at −1.0 V_RHE. This work reveals that the growth condition of the Bi nanostructures plays a significant role in designing the catalysts for the efficient CO₂ reduction reaction.

In this study, we synthesized hierarchical CuO nanoleaves in large-quantity via the hydrothermal method. We employed different techniques to characterize the morphological, structural, optical properties of the as-prepared hierarchical CuO nanoleaves sample. An electrochemical based nonenzymatic glucose biosensor was fabricated using engineered hierarchical CuO nanoleaves. The electrochemical behavior of fabricated biosensor towards glucose was analyzed with cyclic voltammetry (CV) and amperometry (i–t) techniques. Owing to the high electroactive surface area, hierarchical CuO nanoleaves based nonenzymatic biosensor electrode shows enhanced electrochemical catalytic behavior for glucose electro-oxidation in 100 mM sodium hydroxide (NaOH) electrolyte. The nonenzymatic biosensor displays a high sensitivity (1467.32 μA/(mM cm²)), linear range (0.005–5.89 mM), and detection limit of 12 nM (S/N = 3). Moreover, biosensor displayed good selectivity, reproducibility, repeatability, and stability at room temperature over three-week storage period. Further, as-fabricated nonenzymatic glucose biosensors were employed for practical applications in human serum sample measurements. The obtained data were compared to the commercial biosensor, which demonstrates the practical usability of nonenzymatic glucose biosensors in real sample analysis.

Portable fluorescence sensors have been developed for biochemical detection, water quality monitoring, biomedical sensing, and many other applications. With help of advancement in modern electronics, conventional fluorescence-based instrumentations are now integrated into portable sensing devices for remote and resource-limited settings. In this work, fluorescence sensing technology is introduced and different applications of portable fluorescence sensors and their characteristics are reviewed. Current issues, technological challenges, and future direction of the portable fluorescence sensor development are discussed. The goal is to provide a comprehensive survey on the recent advancements in optics, semiconductors, smartphones, and many other manufacturing technologies that increased the portability, miniaturization, and sensitivity of portable fluorescence sensor devices.

A simple method is demonstrated for hydrogen concentrations measurement directly in transformer oil and in the gas space above it use a highly sensitive (at the level of units and fractions of ppm) gas sensor based on a metal-insulator-semiconductor capacitive structure (MIS sensor). The results obtained can be used in online monitoring systems and predicting the power transformers integral performance, in particular those that have been put into operation long ago, by tracking slow and invisible at the initial stage aging processes of current-carrying connections and structural elements.

Development in polymer chemistry empowers creative analytical solutions. Polymers have provided a multitude of separation modes in solid-phase-extraction and chromatography, also they served as matrices for chemical sensors. The current study introduces a polymeric cation-exchanger as a modifier for a solid-state Zn(II) sensor. Literature relates the deteriorated response and limited performance of potentiometric-sensors to the leaching of ion-exchanger and/or analyte out of the sensor matrix. The polymer's limited solubility, small particle size, large surface area, and strong ion-exchanging capacity counteract the efflux of the sensor ingredients, thereby, enhance its performance. An initial optimization study included seven different sensors to reach optimal sensor composition. The optimized sensor maintained a Nernstian response over two months with a slope of 28.06 ± 0.05 mV decade⁻¹, a linear range of 6.3 × 10⁻⁶−1 × 10⁻² M, and a detection limit of 5.12 × 10⁻⁶ M within pH range 4.3–6.8. Statistical comparison shows no significant difference from the official method. Sensor performance parameters were further compared with those of the reported Zn(II) sensors to highlight the advantages and limitations of polymeric ion-exchanger. The sensor expressed a relatively lower detection limit and faster response time. Polymeric exchangers provide potential opportunities to enhance potentiometric sensor performance.

A novel approach for signal enhancement of electrochemical biosensors by incorporating mechanical vibrations has been developed. We report the electrochemical study of the ferricyanide and ferrocyanide $\left(\,{\left[{\rm{Fe}}{\left({\rm{CN}}\right)}_{6}\right]}^{-3/-4}\right)$ a redox couple, at room temperature (∼25 °C), under the effect of mechanical vibrations of different frequencies applied to the sensor, for sensitivity enhancement. The experimental results showed a sensitivity enhancement of ∼332% (from $3.125\,{\rm{nA}}\,\mu {{\rm{M}}}^{-1}$ to $13.5\,{\rm{nA}}\,\mu {{\rm{M}}}^{-1}$) at 88.75 Hz of vibration. This novel approach of signal sensitivity enhancement is also validated with antibody immobilization-based Vi antigen detection for typhoid assessment. The sensitivity enhancement up to ∼15% is achieved for Vi antigen detection under the mechanical vibration of 120 Hz. The sensor is fabricated using microfabrication technology. The vibration-assisted ultrasensitive biosensing platform is also prototyped as a portable and Internet of Thing (IoT) enabled device, suitable for point-of-care applications. Detailed features of the prototype along with the test results are elaborated in the paper.

In this work, we introduced a model of glucose reaction at the electrode and determined the reduction potential of CuOOH/CuO redox couple at CuO nanowires/ITO electrode (CNIE) via an empirical study. The cyclic voltage scanning of CNIE to glucose in different concentrations of NaOH electrolyte solution was conducted using the background subtraction (BS-CV) method. By interpolating the glucose concentration to zero based on the curve of glucose concentration versus oxidation potential in different pH media of NaOH, the standard electrode potential of the CuOOH/CuO redox couple was calculated to be +0.433 (V vs SHE).

Herein, we report a dual biosensing platform operating viz., electrochemical and fluorescence mode for the cancer biomarker, CA15–3 detection. A one-step strategy was employed to synthesize sulphur doped graphitic carbon nitride nanosheets (S-g-C₃N₄). The presence of heteroatom (sulphur) in the molecular structure improved the optoelectronic properties and the surface functional group (–NH₂) facilitated the covalent binding of antibodies and improved the selectivity during the analysis. The proposed biosensing platform was able to quantify very low concentration of the cancer biomarker, CA15–3 (2.9 U mL⁻¹) in human serum samples and thereby evidenced the usefulness of this platform for clinical analysis and early disease diagnosis.

Hydrogen peroxide (H₂O₂) serves a significant role in biological tissues. Throughout this manuscript, the synthesis of a copper complex on the Fe-MIL-101-NH₂ surface functionalized with 5-bromo-2-hydroxy-benzaldehyde (BHB), Cu(BHB)₂/Fe-MIL-101-NH₂ composite was characterized by various techniques. The glassy carbon electrode (GCE) was modified with the Cu (BHB)₂/Fe-MIL-101-NH₂ heterostructure to prepare Cu (BHB)₂/Fe-MIL-101-NH₂/GCE and used for the electrochemical detection of H₂O₂. The results showed that it had a good synergetic effect on the reduction of H₂O₂ in a phosphate buffer solution (PBS) at the pH level of 7.4, in comparison with the bare GCE. The electrochemical methods were also performed for the characterization of the Cu (BHB)₂/Fe-MIL-101-NH₂, these included cyclic voltammetry (CV) and Chronoamperometry (CA). A quantitative H₂O₂ detection was found with a wide linear response toward H₂O₂ concentrations ranging from 0.05 to 3750 μmol l⁻¹, with the limit of detection (LOD) being as low as 10 nmol l⁻¹. Finally, the Cu (BHB)₂/Fe-MIL-101-NH₂/GCE electrochemical sensor was effectively applied to H₂O₂ detection, its applicability was investigated in various milk samples, displaying satisfactory results.

An overdose of the antihypertensive agent in the human body causes a high cardiotoxicity, which may lead to the heart failure and stroke. The routine detection of amount of the antihypertensive agents in biological fluids is vital to control the regulation of blood pressure. In this work, a novel and sensitive electrochemical sensor based on nafion (NF) modified molybdenum disulfide in a metallic 1T phase (1T-MoS₂) for voltammetric determination of renin-inhibitor Aliskiren (ALN) in human plasma. 1T-MoS₂ was effectively synthesized by the exfoliation of bulk MoS₂ using NaK alloy. The structure and morphology of 1T-MoS₂ was characterized by Raman, XPS and TEM. The electrochemical behavior of ALN was investigated on a screen-printed electrode (SPE) modified with 1T-MoS₂/NF nanocomposite by cyclic voltammetry (CV) and adsorptive stripping differential pulse voltammetry (AdsDPV). The proposed electrochemical sensing platform (1T-MoS₂/NF/SPE) demonstrated a good electrochemical activity towards the ALN. Under optimized condition, 1T-MoS₂/NF/SPE exhibited an outstanding analytical performance for ALN with a wide linear working range of 0.05–7.0 μM and a low limit of detection (LOD) of 8.0 nM. The reliability of the developed sensing platform was successfully tested by analyzing of ALN in human plasma samples with satisfactory recoveries. Therefore, 1T-MoS₂/NF/SPE could present as a promising analytical tool for the determination of ALN at trace level in clinical samples.

A fluorescent temperature sensor using temperature dependence of fluorescent inorganic materials is studied for low temperature measurement. Ruby (chromium ions doped sapphire) is used as a sensor head of the fluorescence thermometer because of long photoluminescence (PL) lifetime and visible emission. In this research, ruby crystal is found to be useful as the sensor head for fluorescence thermometer. In addition, the ruby crystal is potentially useful material for the sensor head crystals to measure low temperature below 0 °C.

In this paper, we developed a high performance NiO_x extended-gate field-effect transistor (EGFET) biosensor for detection of uric acid. The structural and sensing properties of the NiO_x sensing film deposited on a n⁺-type Si substrate was examined for an EGFET pH sensor. X-ray diffraction, atomic force microscope and X-ray photoelectron spectroscopy were used to analyze the film features of the NiO_x sensing film. The NiO_x sensing film based on EGFET exhibited a high pH sensitivity of 58.53 mV pH⁻¹, a small hysteresis voltage of 1.4 mV and a low drift rate of 0.30 mV h⁻¹. Moreover, the NiO_x EGFET biosensor showed a high linearity in the uric acid range between 1 and 30 mg dl⁻¹. In addition, this NiO_x EGFET biosensor demonstrated a very good selectivity to uric acid over other interfering substrates (ascorbic acid, glucose, urea).

Integrated mechanical resonators with high quality factors (Q) made in high acoustic velocity materials are essential for a wide range of applications, including chemical sensors, timing resonators, and high-performance inertial sensors for navigation in GPS-occluded environments. While silicon is the most popular substrate for the implementation of microelectromechanical systems (MEMS) resonators, SiC exhibits an exceptionally small intrinsic phononic dissipation due to its low Akhiezer damping limit. This paper reports on the latest developments of precision deep reactive ion etching (DRIE) of monocrystalline 4H SiC-on-Insulator (SiCOI) substrates with the aim to fully take advantage of the exquisite mechanical properties of crystalline SiC. To wit, capacitive Lamé mode micromechanical resonators exhibit ƒ·Q products beyond 1 × 10¹⁴ Hz independent of crystalline orientation. The contribution of surface roughness to dissipation and practical considerations to etch mirror-polished trenches in SiCOI substrates are discussed, paving the way towards micromechanical monocrystalline SiC resonators with Qs beyond 100 Million.

Copper nanoparticles (Cu NPs) have good catalytic performance, but they are easy to be oxidized in the air, which greatly limits their practical application. In this paper, a novel anti-oxidation nitrite electrochemical sensor based on carboxymethylcellulose sodium functionalized reduced graphene oxide-copper nanoparticles (RGO-CMC@Cu NPs) was successfully prepared. Utilizing the high hydrophilia characteristic of CMC, the surface of Cu NPs was coated with an anti-oxidation film to reduce the oxidation rate of copper. At the same time, CMC was used to modify RGO that effectively increased the dispersion ability of RGO in aqueous solution. The prepared nanocomposites were characterized by Transmission Electron Microscope (TEM) and Energy Dispersive Spectroscopy (EDS). Under the optimal conditions, the fabricated sensor based on RGO-CMC@Cu NPs was used to detect nitrite by chronoamperometry. The linear detection ranges of the sensor were 1–15,000 μM and 15,000–41,000 μM with limit of detection (LOD) of 0.05 μM (S/N = 3), and the sensitivities were 0.171 μA·μM⁻¹·cm⁻² and 0.108 μA·μM⁻¹·cm⁻², respectively. In the stability test, the sensor was able to retain 91.1% of its initial sensitivity after 25 days of exposure to air.

In this paper, the N and P co-doped reduce graphene oxide (N, P-rGO) was prepared with one-pot solution method and characterized by using SEM and electrochemical technology. It was found that the N, P-rGO has an outstanding conductivity, large surface area and excellent electrocatalytic activity to hydroquinone (HQ) and catechol (CC), which usually coexist in aqueous environment. Under the optimal conditions, compared with bare glassy carbon electrode (GCE) and N doped reduce graphene oxide (N-rGO) modified GCE (N-rGO/GCE), the N, P-rGO/GCE displayed an excellent simultaneous determination towards HQ and CC. And the oxidation peak potential difference of HQ and CC obtained from N, P-rGO/GCE was 106 mV, indicating N, P-rGO/GCE has excellent resolution. The obtained detection limit was 62.1 nM and 99.7 nM for HQ and CC in a concentration range of 1 μM to 100 μM, respectively. At the same time, N, P-rGO/GCE also displayed satisfied selectivity, decent stability and desirable reproducibility. Furthermore, the fabricated sensor was successfully applied to detect two isomers in tap water and the recoveries of 99.52% to 106.36% and 95.5% to 103.97% for HQ and CC were obtained, which verified the practical application potential of N, P-rGO/GCE.

The strategy of detecting physiological signals and body movements using fabric-based pressure sensors offers the opportunity to unobtrusively collect multimodal health metrics using loose-fitting, familiar garments in natural environments. (A. Kiaghadi, S. Z. Homayounfar, J. Gummeson, T. Andrew, and D. Ganesan, Proc. ACM Interact. Mob. Wearable Ubiquitous Technol., 3, 1–29 (2019)). However, many sensing scenarios, such as sleep and posture monitoring, involve an added static pressure from exerted body weight, which overpowers weaker pressure signals originating from heartbeats, respiration and pulse and phonation. Here, we introduce an all-fabric piezoionic pressure sensor (PressION) that, on account of its ionic conductivity, functions over a wide range of static and dynamic applied pressures (from subtle ballistic heartbeats and pulse waveforms, to larger-scale body movements). This piezoionic sensor also maintains its pressure responsivity in the presence of an added background pressure and upon integration into loose-fitting garments. The broad ability of PressION to record a wide variety of physiological signals in realistic environments was confirmed by acquiring heartbeat, pulse, joint motion, phonation and step data from different body locations. PressION's sensitivity, along with its low-cost fabrication process, qualifies it as a uniquely useful sensing element in wearable health monitoring systems.