Potentiostatic Operation Research Articles

Operando Raman Spectroscopy Reveals Degradation Byproducts from Ionomer Oxidation in Anion Exchange Membrane Water Electrolyzers.

This work showcases the discovery of degradation mechanisms for nonplatinum group metal catalyst (PGM free) based anion exchange membrane water electrolyzers (AEMWE) that utilize hydroxide ion conductive polymer ionomers and membranes in a zero gap configuration. An entirely unique and customized test cell was designed from the ground up for the purposes of obtaining Raman spectra during potentiostatic operation. These results represent some of the first operando Raman spectroscopy explorations into the breakdown products that are generated from high oxidative potential conditions with carbonate electrolytes. We provide a unique design and fabrication method for three-dimensional (3D) printable flow cells that enable spatially resolved Raman spectra collection from the electrode surface into the bulk electrolyte. It is proposed that the generation of breakdown products from the hydroxide-conductive ionomers and membranes originates from a multistep, free radical reaction pathway resulting in chain scission of the poly aryl backbone. This hypothesis is backed by the detection of carboxylic and aromatic functional group Raman signals from small molecules that had dissolved and diffused into the bulk electrolyte.

Degradation modeling in solid oxide electrolysis systems: A comparative analysis of operation modes

To fully realize the potential of solid oxide electrolysis (SOE) systems, improvements in long-term durability and scalability are required. Investigating and comparing different degradation mechanisms under different conditions is crucial. A multi-scale cell to system level time-dependent simulation framework for SOE systems including various degradation phenomena is presented. Galvanostatic, Potentiostatic, and Potentio-Galvanostatic operation, a combination of the two previous modes, are investigated. The time and space evolution of various performance and degradation parameters are compared. Potentio-Galvanostatic operation consistently maintains stable efficiency throughout its lifetime. Near thermoneutral condition is maintained in Potentiostatic and Potentio-Galvanostatic operations, while degradation eventually leads to exothermic operation in Galvanostatic mode. Cathode overpotential is higher in Galvanostatic operation, while in Potentio-Galvanostatic operation, it drops over time as the temperature increases. After 25,000 h of operation under specified conditions, the area-specific resistance (ASR) experiences a 51% and 62% increase in Galvanostatic and Potentiostatic operations, respectively, while Potentio-Galvanostatic operation results in only a 4% increase compared to the beginning of life. Interconnect oxidation is most pronounced in Potentio-Galvanostatic mode, highlighting the need for high-quality steels and coatings in this operation strategy. Over time, in Galvanostatic operation, the current density shifts from being highest at the inlet towards the outlet.

Theoretical Understanding of Effects of Operating Modes on the Performance Durability of Solid Oxide Cells: A Comparison between Potentiostatic and Galvanostatic Operations

In solid oxide cells (SOCs), the choice between galvanostatic (constant current) and potentiostatic (constant voltage) modes does not significantly affect the performance of SOCs as long as the cell components remain unchanged and intact. However, the degradation of cell components, which leads to changes in electrochemical and physical properties of the cell, elevates the importance of the selected operating mode. This paper aims to investigate the effects of galvanostatic and potentiostatic operating modes on the evolving properties of SOCs and their subsequent influence on performance durability. Employing non-equilibrium thermodynamic analysis, a crucial approach for understanding the degradation phenomena within an active electrochemical system, this study aims to provide in-depth insights into how these operating modes affect the longevity and efficacy of SOCs. Key findings include: In cases where oxygen electrode (OE) degradation is accelerated by higher partial pressure of oxygen ( pO2 ), operating under constant voltage electrolysis can mitigate the high pO2 at the OE|electrolyte (OE|EL) interface. Conversely, if OE degradation occurs more rapidly under a lower pO2, constant current electrolysis is more effective in suppressing degradation by achieving a high pO2 at the OE|EL interface. For degradation of the fuel electrode (FE) due to higher pO2, constant current electrolysis is beneficial for more stable performance, which helps maintain low pO2 at the FE|EL interface. When FE degradation is accelerated by lower pO2, constant voltage electrolysis can avert low pO2 at the FE|EL interface. In practical scenarios, more complex degradation mechanisms come into play, especially when pO2 significantly deviates from initial conditions. Degradation in one electrode can influence pO2 in the other electrode, a phenomenon more pronounced in potentiostatic than in galvanostatic electrolysis.

Hydrogen Production Via Mediated Electrolysis of Biomass from Distillery Whisky Waste Streams

Fuel-flexible hydrogen generation methods, such as electrochemical conversion of waste biomass, offer a route to sustainable production of hydrogen (in addition to steam or water electrolysis using renewable electricity [1]) whilst valorising feedstocks that are often overlooked. [2] In this research, the authors explore the potential of a novel, two-stage electrolysis process to convert biomass-containing solid and liquid distillery waste products into hydrogen, using a phosphomolybdic acid (H3[PMo12O40] or PMA) catalyst, at lower operating voltages (<0.95 V) than proton exchange membrane (PEM) water electrolysers (1.5 – 1.6 V). [3]Firstly, an overview of the processes, energy usage and waste stream generation at the Isle of Raasay Distillery (Hebrides, Scotland) will be provided, before results from the characterization of whisky waste products are introduced. This provides a detailed compositional analysis of both solid (draff/spent barley) and liquid (pot ale and spent lees) wastes, as well as residual alcohol analysis of the liquid wastes, and their potential for conversion to hydrogen.Subsequently, the concept of thermal digestion of each waste-type, using the Keggin-type polyoxometalate PMA catalyst to abstract protons and electrons from biomass, will be outlined. Finally, details of electrolysis of the PMA-biomass solutions using a PEM flow cell will be provided, including electrochemical data (AC impedance spectroscopy, linear sweep voltammetry and potentiostatic operation) in order to determine the optimal operating conditions for the process, in addition to the respective yield of hydrogen from each biomass source. Prospects for upscaling the process will also be discussed. References Götz, M., Lefebvre, J., Mörs, F., McDaniel Koch, A., Graf, F., Bajohr, S. Reimert, R. and Kolb, T., Renew. Energ., 85, 1371 – 1390 (2016).Liu, W., Cui, Y., Du, X., Zhang, Z., Chao, Z. and Deng, Y., Energy Environ. Sci., 9, 467 – 472 (2016).Oh, H., Choi, Y., Shin, C., Nguyen, T. V. T., Han, Y., Kim, H., Kim, Y. H., Lee, J-W., Jang, J-W. and Ryu, J., ACS Catal. 10, 2060 – 2068 (2020).

Coupled diffusion-mechanical analysis with dislocation effect in porous spherical electrode

The electrochemical and mechanical performance of lithium-ion batteries is greatly affected by the porous electrode materials and dislocation effect. A diffusion-mechanical coupling model of porous electrode particle with dislocation effect is developed under potentiostatic operation in this work. Then, the distributions of lithium-ion concentration, volumetric strain and stress in the electrode particles with/without dislocation effect are analyzed. Finally, the influences of porosity and tortuosity on the lithium-ion concentration, volumetric strain, radial stress, hoop stress and strain energy are numerically discussed, respectively. The results show that dislocation effect retards the diffusion and relieves the electrode particle expansion and stresses. Moreover, larger porosity or smaller tortuosity can enhance the charge efficiency and avoid electrode particle damage or crack nucleation and propagation by reducing the stress and strain energy. Finally, from the perspective of fracture, dislocation effect can resist the crack propagation or avoid the formation of cracks during charge. This work will provide some theoretical guidance to improve the charge efficiency and prolong battery life.

Evolution of bismuth oxide catalysts during electrochemical CO2 reduction

Bismuth is a promising electrocatalyst for active and selective CO2 electroreduction to formate. Herein, we investigated the evolution of various Bi-based catalysts (β-Bi2O3 nanoparticles, BiOBr nanosheets, Bi2O2CO3 nanosheets, and large α-Bi2O3 and β-Bi2O3 particles) during reaction. Apart from the α-Bi2O3 particles, all the electrocatalysts reach the same Faradaic efficiency (93 ± 2%) and current density during potentiostatic operation, and their morphology changed to nanosheets. This change in morphology can be linked to the formation of Bi2O2CO3 layers, which are prone to reduction to metallic Bi. The final phase and morphology depend on the size of the Bi precursor. Quasi-in situ XPS suggests that a Bi2O2CO3 contribution persists on the surface even for the reduced catalysts. At a current density of 200 mA/cm2, all catalysts reduce to metallic Bi without forming a well-defined sheet morphology. Only for the Bi2O3 nanoparticles can a FE above 90% be maintained.

Role of Operating Modes on the Performance Durability of Solid Oxide Cells: A Comparison between Potentiostatic and Galvanostatic Operations

The commercialization of solid oxide cells for power generation or hydrogen production requires extended cell lifetime and durability. A solid oxide cell can operate either under a potentiostatic or a galvanostatic mode. It remains unclear what’s the role of those two operating modes on the performance durability of solid oxide cells, which limits our understanding and subsequently predicting service life and reliability of solid oxide cells.It is known that many degradation phenomena in solid oxide cells can be accelerated by the electrochemical operations, which manifest various distributions of oxygen chemical potential (μO2) across a solid oxide cell. The variation in the local μO2 is a central driving force for the phase transformation, demixing, and microstructure evolution, leading to a higher resistance of the cell components and decreasing cell performance. As a response to the degradation, the μO2 redistributes across the cell and the driving force for the degradation changes. The μO2 distribution differs when a cell operates at a constant current or a constant voltage. The driving force with different extents of degradation under both operation modes is compared to establish the optimum operation approach, which can shed light on identifying mitigation strategies to improve performance durability with existing cell configurations and materials. Acknowledgement We greatly appreciate the support from U.S. Department of Energy’s Office of Fossil Energy and Carbon Management under DE-FE0032110. Part of this work is supported by U.S. National Science Foundation under NSF-2119688.

Electrochemical Performance of a Spatially Distributed ECPrOx Reactor

In this contribution a spatially distributed Electrochemical Preferential Oxidation (ECPrOx) reactor is evaluated and the influence of the temperature, CO inlet concentration, feed flow rate and relative humidity on the polarization curve, the local current distribution and the CO outlet concentration, selectivity and conversion are investigated. For that, six different cases are studied under galvanostatic and potentiostatic operation. For Galvanostatic operation, it was observed that depending on the operation conditions, the bifurcation point as well as the frequency and amplitude of the oscillations can be modified. Additionally, several spatiotemporal profiles of the local current density were found. For potentiostatic operation, the spatiotemporal profiles are constant with time, however they are affected by the anode overvoltage. Finally, after the bifurcation point, the temporal averaged anode overvoltage and the CO outlet concentration is always lower for galvanostatic control.

The role of the solving strategy in electrokinetic transport modelling in saturated porous media

The characterisation of the reactive transport of solutes is a complex problem that is applied in many fields of industry and environmental management. However, this problem has been treated with multiple mathematical approaches. This paper reviews several strategies for solving the different physical constraints that must be applied to this type of problem using COMSOL Multiphysics. The number of mass balance equations of the chemical species is evaluated together with the use of Gauss’s Law or electric charge balance to analyse the no-charge accumulation or electroneutrality conditions as electrical constraints. Problems of natural diffusion and electrokinetic transport in saturated porous materials are evaluated for electroconductive and nonconductive solid matrices in both potentiostatic and galvanostatic operation modes. Of all the solving strategies proposed, only one is valid and consistent for all types of problems presented. This approach is based on posing a mass balance equation of less (N-1) than the species in solution (N), solving for the mass of the missing species by electroneutrality and imposing the condition of no electric charge accumulation on the charge balance equation.

Energetic evaluations of an electrochemical hydrogen compressor

Hydrogen has been considered as the energy vector that could narrow the gap in the transition towards less polluting energy production. However, it faces compression and storage as technological challenges. Electrochemical hydrogen compression (EHC) is an interesting alternative since it demands low power consumption and could even separate hydrogen from a gas mixture. Therefore, it is necessary to conduct an energetic evaluation of the EHC related to its working conditions to establish the optimal ones in terms of efficiency. This work presents the evaluation and comparison of galvanostatic and potentiostatic operation modes of an EHC with a 50-bar pressure target. During the development of the experimental work, the values of the main overpotentials that affect an EHC were obtained: diffusion voltage, membrane voltage, activation overpotential, and contact overpotential. The highest actual work and power values were achieved at 0.215 V and 0.5 A/cm2 (potentiostatic and galvanostatic mode), while the lowest were obtained at 0.072 V and 0.1 A/cm2. This trend is reversed for voltage efficiency, reaching a maximum of 69.7 % for 0.072 V and a minimum of 19.9 % for 0.5 A/cm2. The calculated flow efficiency values were, for all cases, higher than 94 %, with a maximum efficiency of 99 % at operating conditions of 0.5 A/cm2 and 0.215 V. The global efficiencies of the EHC were also calculated, being more efficient when working in a potentiostatic mode, presenting values of 66 % at 0.072 V against 52 % at 0.1 A/cm2.

Roles of mass transfer and cell architecture in electrochemical desalination performance using polyglycerol activated carbon electrodes

Capacitive deionization (CDI) has emerged as a viable alternative for brackish water desalination. Despite the remarkable advances in salt adsorption capacity (SAC) and charge efficiency (QE), improvements in cell architectures regarding the mass transfer aspects are still needed to boost electrode performance. In this work, we report a comprehensive study of flow-by (FBC), flow-through (FTC), and a percolation flow (PFC) cell architectures for brackish water desalination. It was observed that the electrode thickness was a crucial parameter influencing the desalination performance using the FBC, since the concentration gradient decreased towards the substrate interface, due to mass transfer limitations in the interstitial pores, so thin electrodes were recommended. Although the mass transfer and electrode thickness did not impose restrictions for the FTC, the short residence time limited the SAC, which also dramatically decreased after milling the PGAC particles, due to changes in the textural properties of the electrode, despite the fast desalination rates promoted by the mass transfer enhancement. Taking advantage of the beneficial aspects of the FBC and FTC designs, the desalination carried out using the PFC was enhanced by 170 %. With the flow direction perpendicular to the electric field, together with electrolyte percolation, the substantial improvement of the desalination rate provided by the PFC was also observed under more realistic conditions (single-pass and galvanostatic mode). Compared to batch potentiostatic operation, the PFC presented a remarkable desalination rate of 1661 mg g−1 day−1 at 1.0 mA cm−2 and 7.0 mL min−1. These findings enable a better understanding of the mass transfer aspects involved in CDI desalination, revealing the paramount importance of optimization not only of operational parameters, but also of the cell design.

α-MoB2 Nanosheets for Hydrogen Evolution in Alkaline and Acidic Media

α-MoB2 is recognized as the most efficient molybdenum boride for electrocatalytic hydrogen evolution reaction (HER). However, the convenient synthesis of single phase α-MoB2 is still challenging, and its HER activity in alkaline electrolytes remains unclear. Herein, we report the first successful synthesis of the α-MoB2 nanosheets by a simple and facile molten salt method through the MoCl5 and NaBH4 reaction at 850 °C. The α-MoB2 nanosheets exhibit a remarkable HER performance in alkaline electrolytes, delivering a low overpotential of 124 mV at a current density of 10 mA/cm2. In acidic electrolytes, an improved performance was found in comparison to that of the bulk and nano α-MoB2 with an overpotential as low as 141 mV at 10 mA/cm2. Such HER performance arises from the nanosheet structure that allows more active planes to be exposed. In addition, the α-MoB2 nanosheets possess an outstanding stability in both acidic and alkaline media, showing negligible current density drop even after 3000 cycles and more than 24 h of potentiostatic operation.

A Modular in-Situ Cell to Monitor Gas Diffusion Electrodes during ORR and CO2RR

Metal-based gas diffusion electrodes (GDE) are utilized to achieve high current densities during the reaction in energy conversion systems, such as chlor-alkali electrolysis or the electrochemical reduction of carbon dioxide. By intense contact between the liquid and the gas phase with the catalytically active surfaces within the metallic electrodes, industrially required current densities can be accomplished. Their almost bulk-like silver structures with the 3D porous design and the strong absorption of the extended material make radiographic measurements extremely demanding. To receive in-depth information on electrolyte intrusion into the electrode's porous structure and the distribution during electrochemical measurements, lab-based and synchrotron radiography allows for monitoring this process operando 1, 2 .In this work, we describe the development of a cell design that can be modularly adapted and successfully used to monitor both the ORR and the CO2RR as exemplary and currently very relevant examples of gas-liquid reactions. The applied half-cell set-up designed for ORR allowed for operando synchrotron radiation measurements at electrochemically stable operation at viable industrial conditions and current densities to follow the electrolyte distribution within Ag-based GDE during chlor-alkali-electrolysis. By adding one additional electrolyte compartment, extending the X-ray window, and implementing an anion exchange membrane, the in-house built half-cell set-up designed for operando synchrotron radiation measurements of ORR, was converted into a full-cell set-up for imaging CO2RR of strongly absorbing metal-based GDEs. With the reported cell design, we were able to observe the electrolyte distribution within GDEs during cell operation at technically relevant current densities for CO2RR up to 300 mAcm-2 (Figure 1). By high-resolution synchrotron radiation operando measurements, we demonstrated crystallization of electrolyte caused by the hydrophobic character of the GDE. At high overpotentials, hydrogen evolution reaction caused blockade of the Ag-based GDE, resulting in declining current densities, which could be imaged and monitored during realistic potentiostatic operation. M. C. Paulisch, M. Gebhard, D. Franzen, A. Hilger, M. Osenberg, S. Marathe, C. Rau, B. Ellendorff, T. Turek, C. Roth and I. Manke, ACS Appl. Energy Mater., 4(8), 7497–7503 (2021).M. Gebhard, M. Paulisch, A. Hilger, D. Franzen, B. Ellendorff, T. Turek, I. Manke and C. Roth, Materials (Basel, Switzerland), 12(8) (2019). Figure 1

Performance Characteristics of Polymer Electrolyte Membrane CO2 Electrolyzer: Effect of CO2 Dilution, Flow Rate and Pressure

CO2 electrolyzer designed to operate on dilute CO2 feed and low stoichiometric ratio would alleviate the separation costs for CO2 purification and electrolyzer exit gas processing, respectively. The effect of CO2 concentration, CO2 flow rate, and CO2 pressure on current density and faradaic efficiency of a solid polymer electrolyte membrane CO2 electrolyzer was quantified. An approach for estimating voltage breakdown into activation overpotential for CO2 reduction reaction as well as oxygen evolution reaction, ohmic losses, and concentration overpotential is introduced. No enhancement in current density (∼160 mA cm−2) was observed above stoichiometry ratio of 4 whereas reducing the stoichiometric ratio to 2.7 still yielded a current density of ∼100 mA cm−2. Dilution of CO2 in the feed from 100 mol% to 30 mol%, at ∼90kPa of cell pressure, resulted in a monotonically decreasing current density. A square root dependency on CO2 partial pressure was observed under these conditions. Operation with pure CO2 at different total pressure yielded only a minor increase in current density indicating some form of saturation-limited behavior. Long-term potentiostatic operation over 85 h revealed continuous drop in current density and a corresponding increase in electrode resistance, observed in electrochemical impedance response.

Spatially resolved electrochemical performance and temperature distribution of a segmented solid oxide fuel cell under various hydrogen dilution ratios and electrical loadings

Inhomogeneous distributions are essential factors resulting in degradations of performance and durability of a solid oxide fuel cell (SOFC). In this work, effects of hydrogen dilution ratio and electrical loading on spatially distributed electrical performance and temperature of a segmented SOFC are investigated. Interpretations of local electrode processes and polarization resistances including ion transport, charge transfer, and gas diffusion during potentiostatic operation of the whole cell are obtained. The segment near the gas outlet has the worst initial performance owing to considerably large oxygen surface exchange and reaction overpotential. The temperature distribution obtained by spline interpolation of the experimental data demonstrates that diluting the fuel significantly decreases the average cell temperature at open circuit voltage, which indicates the parasitic combustion heat cannot be ignored. Strongly inhomogeneous distributions of current density and temperature in the cell are observed at low hydrogen ratio and operating voltage, which leads to locally harsh conditions near the gas outlet region. Furthermore, microstructure analysis reveals that the cathode segment adjacent to the gas outlet undergoes greater degradation resulting from oxygen depletion of the cell under low voltage. The results facilitate better understanding of the inhomogeneous electrochemical and temperature behaviors in different zones of a SOFC.

Numerical calculation of lithiation-induced stress in a spherical electrode: Effect of lithiation-induced structural damage

The improvement of the long-time stability of metal-ion batteries requires the understanding of structural integrity of electrode materials during electrochemical cycling. Using the correlation between damage state variable, local concentration and concentration gradient of solute atoms proposed by Yang [Journal of Energy Storage 45 (2022) 103748], we analyze the effects of lithiation-induced structural damage/degradation on the stress evolution in a spherical electrode in the framework of linear elasticity with the coupling between diffusion and stress under respective potentiostatic and galvanostatic operation. Without the contribution of the concentration gradient to structural damage/degradation, the effective stress exhibits an increasing trend, reaches local maximum and then decreases with the increase of the lithiation time at a spatial position away from the center of the spherical electrode for both the potentiostatic and galvanostatic operations. The largest maximum effective stress is present at the surface of the spherical electrode immediately after the onset of the lithiation for potentiostatic operation and inside the spherical electrode for galvanostatic operation. The concentration gradient causes less structural damage/degradation under galvanostatic operation than under photentiostatic operation due to that galvanostatic operation introduces less concentration gradient than potentiostatic operation.

Dynamic acoustic emission analysis of polymer electrolyte membrane fuel cells

This study measures acoustic activity from a PEM fuel cell as a dynamic response during potentiostatic and galvanostatic operations of the cell.

Multiscale modeling of degradation of full solid oxide fuel cell stacks

Limiting the degradation of solid oxide fuel cells is an important challenge for their widespread use and commercialization. The computational expense of long-term simulation of a full stack with conventional models is immense. In this study, we present a multiscale three-dimensional model of a degrading full stack of solid oxide cells, where we integrate degradation phenomena of nickel particle coarsening in the anode electrode, chromium poisoning of the cathode electrode, and oxidation of the interconnect into a multiscale model of the stack. This approach makes this type of simulation computationally feasible, and 38 thousand hours of the stack operation can be simulated in 1 h and 15 min on a high-end workstation. Hereby one can start to explore the optimum operating conditions for a range of parameters. The model is validated with experimental data from an 18-cell Jülich Mark-F stack experiment and predicts common trends reported in the literature for evolutions of the stack performance, degradation phenomena, and the related model variables. Moreover, it captures how different regimes in the full stack degrades at different rates and how the various degradation phenomena interact over time. The model is used to investigate the effects of galvanostatic and potentiostatic operation modes, operating conditions, and flow configurations on the long-term performance of the stack. Results demonstrate, as expected, that potentiostatic operation mode, moderate temperature, lower load current, and counter-flow configuration improve the long-term performance of the stack.

Study of solid oxide electrolysis cells operated in potentiostatic mode: Effect of operating temperature on durability

Potentiostatic operation of solid oxide electrolysis cells (SOECs) at the thermoneutral voltage enables operation of the SOECs close to 100% electrical efficiency and simplifies the heat management at the stack and system level. In this work, we investigate the long-term durability of Ni/yttria-stabilized zirconia (YSZ) fuel electrode supported SOECs operated for electrolysis of steam at the thermoneutral voltage of 1290 mV, by testing cells at 800, 750, and 700 ℃ for periods exceeding 1000 h each. The cells show different initial performance due to different operating temperatures, but all experience a significant degree of initial degradation within the first 300 h, with a degradation rate of 2.80, 1.93, and 1.77 A cm−2 kh−1 (~1.80, 1.51 and 1.90% kh−1) for the cells tested at 800, 750, and 700 ℃, respectively. Hereafter the cells show stable performance or even slight activation. After 300 h of operation, the cell tested at 750 ℃ exhibits performance comparable to the cell tested at 800 ℃ and more than 74% higher than the cell tested at 700 ℃, and this is maintained until the end of the test, suggesting that among three operating temperatures 750 ℃ is the optimum one. The different degradation behavior of the cells is further investigated by electrochemical impedance spectroscopy (EIS) analysis and post-test microstructural characterization. The cause of degradation is discussed in terms of electrode overpotential. Our findings highlight the significance of operating temperature optimization on the long-term durability of SOECs when operated in potentiostatic mode.

Fully chemo‐mechanical coupling analysis of a spherical electrode with reversible chemical reaction

Reversible chemical reaction has an important effect on lithium-ion intercalation/deintercalation and the stress distribution. Reversible chemical reaction, diffusion and electrode deformation will strongly interact with each other. In this work, considering the reversible chemical reaction and its effect on the diffusion and stress, a fully coupled reversible reaction-diffusion-mechanical model is developed, which evaluates reversible reaction-diffusion-induced stresses. Two key parameters, n (the ratio of forward and backward reaction coefficient) and Thiele number (the ratio of forward reaction and diffusion) are used to characterize their effects on the charge and stress under potentiostatic operation. Numerical results show that (1) the forward chemical reaction decreases the charge and promotes the deformation and (2) the backward reaction is needed to improve the charge and prevent the electrode damage.