Slow Scan Rate Cyclic Voltammetry Research Articles

New aqueous energy storage devices comprising graphite cathodes, MXene anodes and concentrated sulfuric acid solutions

The newly emerging demand for ‘beyond-lithium’ electrochemical energy storage systems necessitates the development of alternative options in providing sustainable cost-effective storage capabilities. In pursuit of discovering such a solution, the intercalation of bisulfate anions into graphite in 17 ​M ​H2SO4 solutions has been revaluated. Although the insertion process of bisulfate into graphite was extensively studied many years ago, only poor electrochemical performance has been demonstrated. In this work, we discovered the superior performance of the graphite bisulfate system, associated with the electrodes’ fabrication method which presents a high energy density of more than 80 ​mW ​h/g and a surprising rate capability (75 ​mW ​h/g was obtained at 15 ​C) alongside impressive long-term stability of more than 1500 cycles with only 5% capacity fading. Potentiostatic intermittent titration technique followed by slow-scan-rate cyclic voltammetry (SSCV) was used to shed light on the bisulfate intercalation process. Combining the bisulfate intercalation into the graphite with a highly reversible proton insertion process into Ti3C2 MXene in such a concentrated acidic environment allows the development of a dual-ion device composed of graphite positive electrode (cathode) and MXene negative electrode (anode). This asymmetric system shows a high energy density of 35 ​mW ​h/g, good cyclability and an extended potential window of 1.5 ​V, demonstrating new opportunities for further developments of intercalation electrodes for large energy storage.

Microbial Biocathode Catalyzing Oxygen Reduction and Processing Nitrification

Oxygen biocathodes with electroactive biofilms on graphite electrodes were developed consistently and reproducibly from wastewater inoculum under a high ammonium content selective pressure in a batch microbial fuel cell configuration using ferrocyanide at the anode. The microbial biocathodes process nitrification reactions and catalyse the reduction of molecular oxygen with an onset potential of 0.0 V vs. Ag /AgCl, and a current density at -0.28 V of j = -296 μA/cm2 at pH 7 and 20 °C under oxygen saturation (Cf. Figure).These biofilms also reduce hydrogen peroxide (not shown) at +0.25 V, the potential of an electroactive species in the biofilm (Cf. Figure). The nitrification reactions performed by the biofilm are found to be associated with the catalytic reduction of dioxygen. Nitrification reactions were studied by assaying the nitrogen species (ammonium, nitrite and nitrate) and the effect of adding hydroxylamine, an intermediate of the enzymatic oxidation of ammonium. Metagenomic studies via 16S rRNA gene sequencing of the biofilms onto the colonized electrodes were performed 4 week after inoculation. These studies show that the cathodic biofilms were significantly enriched with Cupriavidus, a proteobacteria genus, that is likely to be responsible for the catalytic properties of the microbial biocathode.The Figure shows the reduction of molecular oxygen by a colonized electrode at pH 7 and 20 °C in a 0.1 M fresh phosphate buffer as recorded with slow scan rate cyclic voltammetry. Scan rate: 1 mV/s. Green: abiotic graphite electrode under oxygen saturation. Black: biocathode under argon saturation. Red: biocathode under air. Blue: biocathode under oxygen saturation. Note also the chemically reversible system found at +0.25 V and assigned to the biofilm. Catalytic hydrogen peroxide reduction (not shown) occurs at the potential of this system. Figure 1

Modulation, Characterization, and Engineering of Advanced Materials for Electrochemical Energy Storage Applications: MoO3/V2O5 Bilayer Model System

Core–shell, multilayered and coated materials have great importance to electrochemical energy storage systems, sensors, actuators, photonics, and photoactive applications. A deeper understanding of the effect of combining different materials in complex structures on their physical and electrochemical properties is vital for better engineering of such compounds and wise modulation of their physical characteristics. Herein we proposed a model system of thin film MoO3/V2O5 bilayer systems. The crystallinity, texture, and morphology of each layer in the bilayer structures were determined by X-ray diffraction (XRD), Raman spectroscopy, high resolution scanning electron microscopy (HR-SEM), and atomic force microscopy (AFM). The electrochemical properties were studied via slow scan rate cyclic voltammetry (SSCV) in lithium ions containing solution. The study clearly shows that the physical and electrochemical properties of each layer in a bilayer configuration are not similar to the properties of the single mat...

Investigation on Electrochemical Properties of TiNb6O17 As the New Anode Materials for High Power Lithium Ion Batteries

Among the commercial anode materials, graphite isn`t suitable for high-power applications such as electric vehicles and large-scale energy storage due to formation of the solid-electrolyte interphase (SEI) leading to lithium irreversibly at about 0.8V and inactive high rate performance. Although, Li4Ti5O12 (LTO) are being pursued as alternatives to graphite electrodes due to high lithium storage voltages (1.0~2.0V) which are higher than the formation of SEI voltage and high rate capability, it has low theoretical capacity (~175mAhg-1). Recently titanium-niobium oxides (TNO) such as TiNb2O7, Ti2Nb10O29 with high redox potential range have been considered as interesting candidates for anode material of LIB. Because they have higher theoretical capacity of 380~396mAhg-1 due to multiple redox couples such as Ti4+/Ti3+, Nb5+/Nb4+, Nb4+/Nb3+ by compared with LTO having only Ti4+/Ti3+ redox couple. In addition, they have good stability, high rate capability. However, they are show limited reversible capacities (240~270mAhg-1) owing to low electronic conductivity and lithium diffusion coefficient. Chunfu Lin et al. presented that TiNb6O17 showed higher capacity, lithium diffusion coefficient and high rate performance than Ti2Nb10O29. Because it is consist of larger amount of Nb5+ ions with larger size (0.64A) than that of Ti4+ ions (0.605A). As a result, it has more open lithium insertion structure and lithium diffusion coefficient than Ti2Nb10O29. But this study not exactly proposed chemical properties such as oxidation state, lithium insertion behavior of TiNb6O17. Based on above study, we have compared physical properties and electrochemical performance of new compound TiNb6O17 and TiNb2O7 which were fabricated using a solid-state reaction method. In a typical synthesis, TiO2 and Nb2O5 in the molar ratio (1:2, 1:6) were mixed with ethanol in a ball mill at 300rpm for 4h. After drying, calcination treatment is carried at 1100°C for 10h in air atmosphere. The crystal structures were determined by X-ray diffraction (XRD), rietveld refinement in order to compare lattice parameters and unit cell volume. X-ray absorption spectroscopy (XAS) was measured to confirm variation of oxidation state and lithium insertion/extraction behavior after charge and discharge. The morphologies were observed by scanning electron microscope (SEM). Finally, we investigated electrochemical performance by measuring cyclic voltammetry, galvanostatic charge-discharge curve and C-rate. Also, electrochemical impedance spectroscopy (EIS) and slow scan rate cyclic voltammetry (SSCV) were measured to compare lithium diffusion coefficients of TiNb2O7 and TiNb6O17. As the result of, TiNb6O17 exhibited better electrochemical performance with lithium diffusion coefficient, charge-discharge capacities and high rate performance than TiNb2O7.

Electrochemical and Spectroscopic Analysis of Mg2+ Intercalation into Thin Film Electrodes of Layered Oxides: V2O5 and MoO3

Electrochemical, surface, and structural studies related to rechargeable Mg batteries were carried out with monolithic thin-film cathodes comprising layered V2O5 and MoO3. The reversible intercalation reactions of these electrodes with Mg ion in nonaqueous Mg salt solutions were explored using a variety of analytical tools. These included slow-scan rate cyclic voltammetry (SSCV), chrono-potentiometry (galvanostatic cycling), Raman and photoelectron spectroscopies, high-resolution microscopy, and XRD. The V2O5 electrodes exhibited reversible Mg-ion intercalation at capacities around 150-180 mAh g(-1) with 100% efficiency. A capacity of 220 mAh g(-1) at >95% efficiency was obtained with MoO3 electrodes. By applying the electrochemical driving force sufficiently slowly it was possible to measure the electrodes at equilibrium conditions and verify by spectroscopy, microscopy, and diffractometry that these electrodes undergo fully reversible structural changes upon Mg-ion insertion/deinsertion cycling.

Synthesis and Electrochemical Characterization of LiNi0.8Co0.2O2 as Cathode Material for Aqueous Rechargeable Lithium Batteries

LiNi0.8Co0.2O2 cathode material for lithium ion batteries is synthesized by reaction under autogenic pressure at elevated temperature (RAPET) method. The simple synthesis procedure is time and energy saving, and thus is promising for commercial application. The structure and stability of the material have been characterized by means of XRD and TG-DTA. The electrochemical properties of the LiNi0.8Co0.2O2 cathode are investigated in 2 M Li2SO4 aqueous electrolyte and they are compared to that in an organic electrolyte. A battery cell consisting of LiNi0.8Co0.2O2 as cathode in 2 M Li2SO4 solution is constructed in combination with LiTi2 (PO4)3 as anode. The cell retained almost constant discharge capacity over hundred cycles. The electrochemical impedance spectral (EIS) studies in aqueous and nonaqueous electrolytes revealed that the mechanism of lithium ion intercalation and deintercalation processes in LiNi0.8Co0.2O2 electrode follow almost similar mechanism in both aqueous and nonaqueous electrolytes. The chemical diffusion coefficient was calculated from slow scan rate cyclic voltammetry and EIS.

Measurement of the ground-state distributions in bistable mechanically interlocked molecules using slow scan rate cyclic voltammetry

In donor-acceptor mechanically interlocked molecules that exhibit bistability, the relative populations of the translational isomers--present, for example, in a bistable [2]rotaxane, as well as in a couple of bistable [2]catenanes of the donor-acceptor vintage--can be elucidated by slow scan rate cyclic voltammetry. The practice of transitioning from a fast scan rate regime to a slow one permits the measurement of an intermediate redox couple that is a function of the equilibrium that exists between the two translational isomers in the case of all three mechanically interlocked molecules investigated. These intermediate redox potentials can be used to calculate the ground-state distribution constants, K. Whereas, (i) in the case of the bistable [2]rotaxane, composed of a dumbbell component containing π-electron-rich tetrathiafulvalene and dioxynaphthalene recognition sites for the ring component (namely, a tetracationic cyclophane, containing two π-electron-deficient bipyridinium units), a value for K of 10 ± 2 is calculated, (ii) in the case of the two bistable [2]catenanes--one containing a crown ether with tetrathiafulvalene and dioxynaphthalene recognition sites for the tetracationic cyclophane, and the other, tetrathiafulvalene and butadiyne recognition sites--the values for K are orders (one and three, respectively) of magnitude greater. This observation, which has also been probed by theoretical calculations, supports the hypothesis that the extra stability of one translational isomer over the other is because of the influence of the enforced side-on donor-acceptor interactions brought about by both π-electron-rich recognition sites being part of a macrocyclic polyether.

Voltammetry and Growth Physiology of Geobacter sulfurreducens Biofilms as a Function of Growth Stage and Imposed Electrode Potential

AbstractThe ability of Geobacter sulfurreducens to utilize electrodes as electron acceptors provides a system for monitoring mechanisms of electron transfer beyond the cell surface. This study examined the physiology of extracellular electron transfer during many stages of growth, and in response to short‐ and long‐term changes in electron acceptor potential. When G. sulfurreducens was grown on planar potentiostat‐controlled electrodes, the magnitude of early cell attachment increased with initial cell density. However, the first cells to attach did not demonstrate the same electron transfer rates as cells grown on electrodes. For example, following initial attachment of fumarate‐grown cells, the electron transfer rate was 2 mA/mg protein, but increased to nearly 8 mA/mg protein within 6 h of growth. Once attached, all biofilms grew at a constant rate (doubling every 6 h), and sustained a high specific electron transfer rate and growth yield, while current density was below 300 μA/cm2. Beyond this point, the rate of current increase slowed and approached a stable plateau. At all phases, slow scan rate cyclic voltammetry of G. sulfurreducens showed a similar well‐defined sigmoidal catalytic wave, indicating the general model of electron transfer to the electrode was not changing. Short‐term exposure to reducing potentials (3 h) did not alter these characteristics, but did cause accumulation of electrons which could be discharged at potentials above −0.1 V. Sustained growth at lower potentials (−0.16 V) only slightly altered the pattern of detectable redox species at the electrode, but did eliminate this pattern of discharge from the biofilm. Single‐turnover voltammetry of colonized electrodes showed at least 3 redox couples at potentials similar to other recent observations, with redox protein coverage of the electrode on the order of ca. 1 nmol/cm2. The consistent electrochemistry, growth rate, and growth yield of the G. sulfurreducens biofilm at all stages suggests an initial phase where cells must optimize attachment or electron transfer to a surface, and that after this point, the rate of electron production by cells (rate electrons are delivered to the external surface) remains rate limiting compared to the rate electrons can be transferred between cells, and to electrodes.

Electrochemical investigation of polarization phenomena and intercalation kinetics of oxidized graphite electrodes coated with evaporated metal layers

The electrochemical behavior of partially oxidized graphite electrodes coated with 50 Å thick Au, Cu, In, Pb or Sn layers has been studied by slow scan rate cyclic voltammetry and galvanostatic charge–discharge. Electrochemical impedance spectroscopy (EIS) has also been applied to Cu- and Sn-coated electrodes in order to study the effect of the metal coating on the interfacial intercalation/deintercalation kinetics. The results demonstrate that certain metallic layers produce remarkable improvements of intercalation kinetics of graphite electrodes by reducing the charge-transfer and the solid–electrolyte interface (SEI) resistance making this type of surface modification attractive for the development of high rate anodes for lithium-ion batteries.

The film growth and electrochemical properties of rf-sputtered LiCoO 2 thin films

In this work, the effect of various sputtering parameters (such as working pressure, O 2 fraction, and rf power) on the film growth of HT-LiCoO 2 on Pt-coated silicon were investigated. The as-deposited films and annealed films show crystalline HT-LiCoO 2 single phase with (1 0 4) preferred orientation under various sputtering parameters. From ICP results, it was observed that the sputtering parameters and annealing process affected the compositions of the films obviously. The annealing process enhanced the crystallinity of HT-LiCoO 2 films. They showed difference in crystallinity and resulted in the variation of Li + diffusion coefficient that was measured and estimated by slow-scan-rate cyclic voltammetry (SSCV) and galvanostatic intermittent titration technique (GITT) techniques. The charge/discharge tests indicated that films exhibit higher D L i + showed better rate capability.

Kinetic and Thermodynamic Studies of Mg2 + and Li + Ion Insertion into the Mo6 S 8 Chevrel Phase

Slow-scan rate cyclic voltammetry (SSCV) and chronopotentiometry were used for a quantitative comparison of the thermodynamic and kinetic characteristics of and -ion insertion into the chevrel phase compound. The Li-insertion process consists mainly of three stages with the relative stoichiometries 1:2:1, corresponding to the formation of and respectively. The kinetics of the intercalation is relatively fast. Mg-ion insertion was found to have the stoichiometry 2:2, i.e., and are formed. The initial magnesiation and the final demagnesiation of the chevrel phase reveal intrinsically slow kinetics, accompanied by a substantial decrease in the intercalation level. This probably results from a low ionic conductivity of the electrode bulk caused by both small concentration and low mobility of the Mg ion in this potential region, related to the sites that the Mg intercalants occupy in the phase. A moderate increase in temperature results in a drastic increase of ion mobility. In solution, the difference of the two sequential insertions of Mg ion into the chevrel phase was found to be 0.26 V, i.e., by 0.08 V lower than that for the insertion of Li ion. © 2004 The Electrochemical Society. All rights reserved.

The effect of dimethyl pyrocarbonate on electroanalytical behavior and cycling of graphite electrodes

The addition of small concentrations of dimethyl pyrocarbonate (DMPC), about 5% by volume, to a standard solution of 1 M (1:1) was shown to improve substantially the cycling behavior of graphite electrodes. A combination of fast and slow scan rate cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared, and nuclear magnetic resonance spectroscopy were applied to understand the nature of the stabilizing effect caused by the presence of DMPC. DMPC was shown to increase impregnation of the active mass of the porous electrodes with solution (thus increasing the specific electrode capacity), and facilitates the rate of Li-ion migration across the surface films around the graphite particles and across the surface film/particle interface. Based on a combination of fast- and slow-scan rate CV and EIS, a convenient procedure allowing for an intermittent monitoring of the kinetic and thermodynamic characteristics of the Li-insertion process into graphite in the course of long-term electrode cycling was elaborated. We show that a simple procedure consisting of the application of a series of consecutive fast- and slow-scan rate CVs can be conveniently used for a systematic search and optimization of electrolyte solutions suitable for long-term cycling of graphite electrodes in lithium-ion cells. © 2004 The Electrochemical Society. All rights reserved.

Effect of temperature on the kinetics and thermodynamics of electrochemical insertion of Li-ions into a graphite electrode

We report on the potential and temperature dependences of the differential intercalation capacitance, C dif, and the chemical diffusion coefficient, D, during Li intercalation into a graphite anode by a combined application of slow-scan rate cyclic voltammetry (SSCV) and the potentiostatic intermittent titration technique (PITT). Drastically different behavior was observed within the short-time ranges of the PITT response measured for a two-phase coexistence domain and a solid solution of phases 4 and 3. Electroanalytical evidence for small droplet formation (nucleation) of a new phase in the bulk of the old one was found for the former domain, showing good correlation with in situ XRD studies. SSCV data obtained in the 25–80 °C temperature range were in excellent agreement with the published temperature–concentration phase diagrams built on the basis of detailed XRD characterizations. The simultaneous appearance of maxima on C dif versus E plots and minima on the related log D versus E plots in the two-phase domains was rationalized in terms of a lattice gas model with single site energy, and highly attractive interactions between the intercalated guest atoms. The electroanalytical behavior of graphite within the solid-solution domain (a mixture of phases 4 and 3) was interpreted semi-quantitatively on the basis of a model that took into account the presence of two sub-lattices of different energy (a model of “energetic heterogeneity”) for Li accommodation, and attractive interactions between the guest atoms on each sub-lattice, or, alternatively, due to in-plane order–disorder transitions because of short-range repulsive interactions between the intercalated guest species.

Electrochemical behavior of graphite anode at elevated temperatures in organic carbonate solutions

A combination of three major electroanalytical techniques (slow-scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS)) was applied for comprehensive analysis of temperature dependence of the most important equilibrium and kinetic parameters related to the Li-insertion process. These parameters include the differential intercalation capacity, C int and the chemical diffusion coefficient, D chem. We have analyzed the complicated, ambivalent influence of the temperature on the shape of the cyclic voltammety curves, probing the rate of separate steps of the intercalation process close to equilibrium. Good agreement had been found between the SSCV data measured over a wide range of temperatures, and the classical staging phase diagram of Li x C 6 (this diagram is presented as a plot of the absolute temperature, T versus intercalation level, x).

Lithium intercalation into the shell of `cylindrical hard deposit'

As the main by-product of fullerene, a novel form of solid carbon – the shell of the `cylindrical hard deposit' was synthesized by electrical arc discharge between two carbon electrodes. The results of the electrochemical intercalation of lithium into the shell in 1 M LiClO 4 EC/DEC (50:50) electrolyte are presented here. Our results show that the shell has high irreversible capacity. Complementary analytical techniques, including X-ray diffraction, slow scan rate cyclic voltammetry, constant current charge–discharge tests and ac impedance investigations, were used for full structural characterization of the shell and the electrochemical intercalation of lithium.

Study of lithium insertion into electrochemically synthesized sodium–vanadium oxide

We report herein on the electroanalytical behavior of Li x Na y V 2O 5 electrodes that were synthesized electrochemically from aqueous solutions of vanadyl and sodium sulphates, followed by thermal annealing (300°C). The electrodes were comprised of monolithic layers deposited on a stainless steel plate. A capacity above 200 mAh/g could be obtained at relatively high rates (>C/3 h) and prolonged cycling (hundreds of charge–discharge cycles). As evident from FTIR and XPS measurements, the electrodes develop surface films due to interactions with CO 2 in the air and solution species. Electroanalytical data obtained from slow scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT), and impedance spectroscopy (EIS) are discussed.

Li-insertion into thin monolithic V 2O 5 films electrodes characterized by a variety of electroanalytical techniques

Slow-scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) have been simultaneously applied to study Li-ion intercalation into V 2O 5 films prepared by vacuum-deposition on Pt foils. The most prominent feature of their electrochemical behavior relates to sharp minima on D versus E plots, which are observed in the vicinity of very narrow cyclic voltammetric peaks. This was explained in the framework of a lattice-gas model with very high, attractive electron-ion interactions during Li-ion intercalation into the V 2O 5 electrode, as was already described for similar processes in graphite and some transition metal oxides: Li x CoO 2, Li x NiO 2, Li x Co y Ni 1− y O 2 and Li x Mn 2O 4. Referring to the impedance spectra of the V 2O 5 electrodes, we show good agreement between the data obtained by the different techniques in the related time (or frequency) domains. This relates to both the differential intercalation capacity, C int (low-frequency domain), and the chemical diffusion coefficient D (medium-frequency domain).

On the correlation between the electroanalytical behavior and crystallographic features of Li-intercalation electrodes

Abstract The electroanalytical behavior of LixNiO2 and LixCo0.2Ni0.8O2 was studied by simultaneous application of slow-scan rate cyclic voltammetry (SSCV), potentiostatic and galvanostatic intermittent titration (PITT and GITT), and electrochemical impedance spectroscopy (EIS). Application of a finite-space diffusion model for treating the results obtained by these techniques allowed us to calculate the diffusion coefficient of Li ions (D) and the differential (incremental) capacity (Cint) as functions of the electrode’s potential. Our final purpose was to compare D versus E and Cint versus E plots for both the electrodes, in order to correlate the observed difference in their electroanalytical behavior with the clear distinction in the related Li-insertion mechanisms deduced from XRD studies. While Li insertion into LixCo0.2Ni0.8O2 exhibits a single-phase reaction upon charge in the 3.0–4.08 V (versus Li/Li+) range, Li intercalation into LixNiO2 undergoes two-phase transitions in the same potential range. The shape of both plots, D versus E and Cint versus E for these electrodes, is discussed in the framework of a finite-space diffusion model and Li-insertion processes that can be described by Frumkin-type intercalation isotherms with short-range attraction interactions among intercalation sites.

Basic electroanalytical characterization of lithium insertion into thin, well-crystallized V2O5 films

Slow-scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT) and electrochemical impedance spectroscopy (EIS) have been applied simultaneously to study Li ion intercalation into V2O5 films prepared by evaporative vacuum-deposition on Pt foils. Two different films, 1600 and 3600 A thick, were used to study the influence of the film's thickness on the major electroanalytical characteristics of these intercalation electrodes. Modeling of the impedance spectrum related to the thin V2O5 film was performed using an equivalent circuit analog including the following elements: three R ∣∣ C semicircles (covering the high-frequency domain) and finite-length Warburg in sequence with the intercalation capacity (a straight line of unit slope at intermediate frequencies, and a sloping capacitive line at the very low frequencies). Sharp minima on D versus E plots, which are observed in the vicinity of the cyclic voltammetric peaks, present further evidence of very high, attractive electron–ion interactions during Li ion intercalation into the V2O5 electrode, as was already described for similar processes in graphite and some transition metal oxides: LixCoO2, LixNiO2, LixCoyNi1−yO2 and LixMn2O4. The diffusion length in these electrodes related to the V2O5 film's thickness.

Evidence for Slow Droplet Formation during Cubic‐to‐Tetragonal Phase Transition in LixMn2 O 4 Spinel

We studied the electroanalytical response of electrodes around 3 V (vs. ) using slow scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. Broad anodic and cathodic peaks of typical 50 to 60 mV half‐peak width, and a surprisingly large peak potential separation (ca. 150 mV and higher) appear on the SSCV curves of thin electrodes around 3 V (vs. ). The subsequent potentiostatic titrations performed at 10 mV steps revealed quite an unusual response; an increase in the current with time at 2.94 and 3.00 V during discharge and charge, respectively. The above features of the cyclic voltammograms (at slow scan rate) and the current vs. time response can be understood in terms of a phase transition controlled by slow formation of droplets of a new phase in the bulk of the old one. A model describing such a process, based on the refined Frumkin‐type sorption isotherm, which relates to both the electronic and the ionic species which participate in the intercalation reaction, is developed. The SSCV curves simulated according to this model agree well with the experimental ones. We also show a semiquantitative comparison of the electroanalytical characteristics of electrodes around 3 and 4 V (vs. ). © 2000 The Electrochemical Society. All rights reserved.