Theory and application of cyclic voltammetry for measurement of fast electrode kinetics at microdisk electrode

An analytical expression describing voltammetric behaviors responses at microdisk electrode for various diffusion conditions and degrees of reversibility is reported in this paper. Results of theoretical calculation made it possible to use cyclic voltammetry to evaluate heterogeneous rate constants under intermediate diffusion conditions. At relatively low scan rate, the distortion of current-voltage can be reduced due to small iR drops and charging current. The effects of transfer coefficient, a, kinetic parameter, (=k0r/4D), and switching potential, s, on potential peak separation are discussed in detail. The relationship obtained in this paper between potential peak separation and \ is in good agreement with that in Ref. 14, whose authors have got their results by using digital simulation technique. After the experiment of Fe(CN)64- oxidation, k0 and a were obtained by the theory of this paper. The result agrees with that in Ref. 19.     

Study on electrode process of myoglobin at a polymerized Toluidine Blue film electrode

This paper reports the use of an electrochemically polymerized Toluidine Blue (TB) filmelectrode.The film on platinum electrode surface was analyzed with ESCA.The heterogeneouselectron transfer processes of myoglobin at the polymerized TB film electrode have been investigatedusing in situ UV-visible spectroelectrochemistry.The formal potential(E°′)and electron transfernumber(n)of myoglobin were calculated as E°′=0.045 V(vs.NHE)and n=0.99.The exhaustivereduction and oxidation electrolyses are achieved in 130 s and 110 s respectively,during a potential stepbetween-0.4 V and+0.4 V.A formal heterogeneous electron transfer rate constant(ksh)of 1.09×10~(-4) cm/s and a transfer coefficient(α)of 0.47 were obtained by cyclic voltabsorptometry,whichindicated that myoglobin underwent a quasi-reversible electrode process at the polymerized TB filmelectrode.     

Application of silver electrode to the electrochemical studies of hemoglobin

Several aspects of the application of silver electrode to the electrochemical studies of hemoglobin have been discussed in this paper . The silver electrode could not only be used directly as the electrode for the electrochemical studies of hemoglobin, but also react with phenothiazine and benzimidazole to give stable and useful mediator-coated electrodes. In addition, the silver electrode could help sodium dodecyl sulfate to give full play to its promoting effect on the protein.     

Reversible electrochemistry of DNA on multi-walled carbon nanotube modified electrode

Calf thymus DNA was electrochemically oxidized at a multi-walled carbon nanotube modified electrode. The potentials for DNA oxidation at pH 7.0 were 0.71 and 0.81 V versus SCE, corresponding to the oxidation of guanine and adenine residues, respectively. The initial 6e-oxidation of adenine, observed in the first scan, resulted a quasi-reversible 2e-redox process of the oxidation product in the following scans.     

Investigation on property and mechanism of redox wave of methylhesperidine at Hg electrode

The voltammetric behaviors of methylhesperidine (MH) were studied by means of linear sweep voltammetry, cyclic voltammetry and normal pulse voltammetry. In the Brit-ton-Robinson buffer solutions with pH values from 2.05 to 6.37, MH could yield three reduction waves PC1,PC2 and PC3. PC1 wave is an adsorptive pre-wave. PC2 wave is an irreversible reduction of pre-protonated MH involving one electron and one proton. PC3 wave is an irreversible wave of reduction species radical of MH involving one electron.     

Voltammetric determination of uric acid by using gold nanotubule electrode

Gold nanotubule membranes were prepared by using electroless deposition of gold within the pores and surfaces of polycarbonate track-etched membranes.And the gold nanotubule membrane was used as an electrode for determination of uric acid in urine samples for the first time.In Britton-Robinson buffer of pH 4.56,uric acid exhibited well-defined differential pulse voltammograms.And the interference between coexistent ascorbic acid and uric acid was overcome owing to the attractive ability of the gold nanotubule electrode to yield a large anodic peak difference ca.0.404 V(vs.SCE).The proposed method was then applied to the determination of uric acid in urine without any pretreatment.     

Systematic evaluation of advance in application and discharge mechanism of solution electrode glow discharge

As a kind of microplasma sustained in air, solution electrode glow discharge(SEGD) ignited between the liquid electrode and metal electrode is attractive to the fields of optical emission spectrometry and mass spectrometry due to its unique advantages, such as low power consumption and low carrier gas consumption. Moreover, the complex and efficient reactions in the liquid phase and plasma phase of SEGD make it considerable research potential in the fields of biology and medicine, material synth...     

Direct electrochemistry behavior of Cytochrome c on silicon dioxide nanoparticles-modified electrode

A newfangled direct electrochemistry behavior of Cytochrome c (Cyt c) was found on glassy carbon (GC) electrode modified with the silicon dioxide (SiO2) nanoparticles by physical adsorption. A pair of stable and well-defined redox peaks of Cyt c′ quasi-reversible electrochemical reaction were obtained with a heterogeneous electron transfer rate constant of 1.66×10-3 cm/s and a formal potential of 0.069 V (vs. Ag/AgCl) (0.263 V versus NHE) in 0.1 mol/L pH 6.8 PBS. Both the size and the amount of SiO2 nanoparticles could influence the electron transfer between Cyt c and the electrode. Electrostatic interaction which is between the negative nanoparticle surface and positively charged amino acid residues on the Cyt c surface is of importance for the stability and reproducibility toward the direct electron transfer of Cyt c. It is suggested that the modification of SiO2 nanoparticles proposes a novel approach to realize the direct electrochemistry of proteins.     

Measurement of the change in the partial molar volume during electrode reaction by gravity electrode—I. Theoretical examination

Gravity electrode is an electrode system, which is operated in a high gravity field arising from centrifugal force, and allows us to measure the change in the partial molar volume between product and reactant ions in an electrode reaction. In this paper, in the presence of a large amount of supporting electrolyte, the partial molar volume of each active ion in equilibrium state is first formulated on the basis of thermodynamics. Then, the change in the partial molar volume applicable to gravity electrode is derived. Therefore, it is possible to validate the equation obtained for gravity electrode by the thermodynamic measurement.     

A digital simulation study of two-dimensional convection diffusion for channel electrode

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Review of vanadium-based electrode materials for rechargeable aqueous zinc ion batteries

In recent years,rechargeable aqueous zinc ion batteries(ZIBs),as emerging energy storage devices,stand out from numerous metal ion batteries.Due to the advantages of low cost,environmentally friendly characteristic and safety,ZIBs can be considered as alternatives to lithium-ion batteries(LIBs).Vanadiumbased compounds with various structures and large layer spacings are considered as suitable cathode candidates for ZIBs.In this review,the recent research advances of vanadium-based electrode materials are systematically summarized.The electrode design strategy,electrochemical performances and energy storage mechanisms are emphasized.Finally,we point out the limitation of vanadium-based materials at present and the future prospect.     

Computer simulation of negative electrode operation in lithium—ion battery: Galvanostatic discharge,porous electrode model and film model

Computer simulation of the structure and methods of operation (galvanostatic discharge) of the negative electrode of a lithium-ion battery is performed. Two possible models of the active anode layer were compared. 1. The model of porous active layer (mixture of active substance grains with grains of electrolyte). Here, the electrochemical process occurs within a porous active layer. 2. The film model (constant-thickness layer) of pure active substance (intercalating agent) grains without admixture of grains of electrolyte. In this case, the electrochemical reaction occurs only on the planar active electrode layer/interelectrode space interface. In both cases, the optimum working parameters of anode active layers were calculated: porous active layer thickness (in the film model, this was the calculation parameter), duration of full anode discharge, specific electric capacitance and finite difference between the intercalating agent/electrolyte potentials at the active anode layer/interelectrode space interface. It is found that each of these two models has its advantages and faults. Specific electric capacitance C cannot exceed the values of the order of magnitude of 10 C/cm² when a porous active layer is used. Whereas in the film model, much higher values of C may be obtained: tens and even hundreds of C/cm². On the other hand, in the case of anode discharge, the reasonable discharge current density value, its maximum value, at which practically full recovery of lithium atoms from active intercalating agent grains is still possible, proves to be by orders of magnitude higher in the case of an anode with a porous active layer, as compared with a film-type anode. Thus, in the case of development of electrode active layers of lithium-ion batteries, there is a possibility of choosing from two variants. There is the variant of an active film-type layer providing high capacitance values, but low discharge current density. Or there is another variant: a porous active layer with limited capacitance but then much higher values of discharge current density.     

Study of electrooxidation of binary electrolytic deposit palladium–bismuth deposited on graphite electrode surface

The phase structure of palladium–bismuth binary electrolytic deposit was studied. The electrodeposition of deposit components on the surface of a graphite electrode (GE) was carried out in situ. On current–voltage curves, the peak of bismuth electrooxidation, the peak of palladium electrooxidation and an additional peak at 0.15 V vs. Ag/AgCl are observed. The peak current at 0.15 V depends both on the concentration of palladium(II) ions and on that of bismuth(III) ions. The thermodynamic theory of alloys in the approximation of the theory of regular solutions was used for calculations. The mixing heat of the binary alloy components and the equilibrium potential of bismuth in the bismuth–palladium alloy are calculated. The calculated equilibrium potential of bismuth in an alloy with palladium is 0.12 V vs. Ag/AgCl which corresponds to the Bi₂Pd intermetallic compound (IMC). Investigation of the surface of a GE with a palladium–bismuth deposit with use of scanning electron microscope showed that the electrolytic deposit contains bismuth, palladium and the Bi₂Pd IMC. Peak at the potential of plus 0.15 V vs. Ag/AgCl is due to selective bismuth electrooxidation from the Bi₂Pd IMC.     

Electrooxidation and determination of some non-steroidal anti-inflammatory drugs on nanoparticles of Ni–curcumin-complex-modified electrode

The electrooxidation of several non-steroidal anti-inflammatory drugs (indomethacin, mefenamic acid, and diclofenac) was investigated on nanoparticles of Ni–curcumin-complex-modified glassy carbon (n-GC) electrode in alkaline solution. Surfaces studies were performed by scanning electron micrographs and atomic force microscopy. The oxidation process and its kinetics were studied using cyclic voltammetry and chronoamperometry techniques and also pseudo-steady-state polarization measurements. Voltammetric studies indicated that, in the presence of drugs, the anodic peak current of low-valence nickel species increases, followed by a decrease in the corresponding cathodic current. This pattern indicates that drugs were oxidized on the redox mediator immobilized on the electrode surface via an electrocatalytic mechanism. A mechanism based on the electrochemical generation of Ni(III)-active sites and their subsequent consumption by drugs was proposed. The rate constants of the catalytic oxidation of drugs and the electron-transfer coefficient are reported. A sensitive, simple, and time-saving amperometric procedure was developed for the analysis of these drugs in bulk form and for the direct assay of tablets, using the n-GC electrode.     

A comparison of different types of gold–carbon composite electrode for detection of arsenic(III)

A study has been conducted using abrasively modified basal and edge-plane graphite, carbon-paste, and carbon–epoxy electrodes to create gold–carbon composite electrodes. Using either nano or micro-sized gold particles their suitability for use in detecting arsenic(III) is assessed. It was found that gold arrays prepared from micron-sized particles gave the best performance for arsenic detection. In particular micron arrays produced in carbon-paste electrodes with an easily renewable surface work well for detection of arsenic, producing a detection limit of 5(±2)×10^–9 mol L^–1, with a high sensitivity of 10(±0.1) A mol^–1 L.     

Degradation diagnosis of lithium-ion batteries using AC impedance technique in fixing the state of charge of an electrode

A sustainable society requires an increase in electrified vehicles(xEVs) with a low environmental impact. Among various types of xEVs, battery electric vehicles (BEVs) with lithium-ion batteries(LIBs) have received considerable research attention.     

Analysis of the Volmer–Krishtalic mechanism for the chlorine electrode reaction

The dependencies of the current density and surface coverage of the adsorbed intermediates on overpotential were established without kinetic approximations for the chlorine electrode reaction under the Volmer–Krishtalic mechanism. Tafelian regions were obtained which slope values cannot be derived from the use of the rate determining step criteria, such as 2.3026(2RT/3F) and 2.3026(RT/F), as well as two or three Tafel regions with different slopes in the same anodic or cathodic curve. The existence of limiting kinetic current densities was also demonstrated. Finally, the results obtained were analysed and discussed, comparing them with those obtained by the usual methods.     

Electrochemical behavior of C-(60) modified electrode in aqueous solutions

The construction of adsorptive type C60 modified electrode and its electrochemical reduction and oxidation behavior in aqueous solutions are described in this report. Four pairs of one-electron transfer reduction and oxidation cyclic voltammetry is obtained in aqueous solution containing 30% CH3CN and 2% (C2H5)4NOH. It is reported in this paper that the C60 modified electrode also catalyzes the electrochemical reduction of dissolved oxygen in 40% DMF and 2% (C2H5)4NOH aqueous solution and this might open a new field for the potential applications of C60 in electrochemistry and electroaualytical chemistry.