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1.
The faradaic impedance of the surface redox system benzo(c)cinnoline-dihydrobenzo(c)-cinnoline is studied experimentally in aqueous medium between pH 5 and 13. The variations of the impedance components are in good accord with the theoretical predictions. A V-shaped curve is found for log ks=f(pH) (ks=rate constant of the surface electrochemical reaction). It is estimated that the determination of rate constant values up to 2×104 s?1 on a mercury electrode is possible by this method. 相似文献
2.
In this work we have proposed a qualitative mechanism for the first two steps of the reduction of the dodecatungstic anion on a gold electrode using measurements of faradaic impedance. Two types of supporting electrolyte were chosen—sulphate and perchlorate. The effect of competition with adsorbed SO42? could be observed on the first reduction step. In both steps the charge transfer is related with homogeneous proton transfer reactions. 相似文献
3.
The effect of infiltrating on a La0.85Sr0.15MnO3/Ce0.9Gd0.1O1.95 11-layer electrochemical reactor with CeO2 and Ce0.8Pr0.2O2?δ was studied in propene oxidation at open-circuit voltage and under polarization as a function of reaction temperature. This work outlined the importance of catalytic and electrochemical properties of infiltrated material on the ability to increase propene conversion under polarization with good faradaic efficiency. Electrochemical impedance spectroscopy was used to study the effect of infiltration material on electrode properties. The infiltration of a mixed ionic and electronic conductor, like Ce0.8Pr0.2O2?δ , increased the electrode performance at low temperature but decreased the lifetime of the oxygen ion promoters on the catalyst/electrode surface, reducing the faradaic efficiency of the reaction. The infiltration of CeO2 provided high propene conversion at open circuit and high effect of polarization associated with good faradaic efficiency, especially at low temperature. 相似文献
4.
Dr. Piotr Połczyński Dr. Rafał Jurczakowski Dr. Adam Grzelak Dr. Evgeny Goreshnik Dr. Zoran Mazej Prof. Wojciech Grochala 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(19):4927-4930
The use of the boron-doped diamond electrode as a sufficiently stable electrode for electrochemical measurements/synthesis in liquid anhydrous hydrogen fluoride medium is reported. Electrooxidation of silver(I) has been studied in this solvent by using classical transient electrochemical methods and impedance spectroscopy. It has been found that faradaic currents related to silver(I) oxidation and the fluorine evolution reaction are reasonably separated at the potential scale, which allows efficient electrosynthesis of AgIIF2, a powerful oxidizer. Impedance spectroscopy measurements provide insight into complex mechanism of AgF2 formation. The procedure for electrosynthesis is provided for the first time in both galvanostatic and potentiostatic condition. 相似文献
5.
Mishuk V. Ya. Elkin V. V. Abaturov M. A. Alekseev V. N. Grafov B. M. 《Russian Journal of Electrochemistry》2002,38(9):959-964
The kinetics of electrode reactions with a rather severe influence of the EDL structure is studied by nonlinear second-order impedance spectroscopy. Polarization impedance spectra and potential dependences of a nonlinear impedance are obtained for the reaction of electroreduction of the ferricyanide anion on the cadmium and bismuth electrodes in surface-inactive supporting NaF and Na2SO4 electrolytes. The results of measurements for the reaction Eu3+ + e Eu2+ on the bismuth and mercury electrodes are presented. It is shown that such important parameters of EDL as the potential of zero charge and the second derivative of potential with respect to the charge of the electrode surface can be determined directly from experimental curves even under conditions of occurrence of a faradaic process. 相似文献
6.
The adsorption of urea on a polycrystalline copper electrode from 0.01 M NaClO4 solution has been studied by impedance spectroscopy and radiometric method. The dependence of the surface concentration of urea on the electrode potential and the bulk concentration was determined. From radiometric data, it follows that the adsorption of urea on the copper electrode takes place in the entire range of studied potentials where no faradaic processes occur. In this range, the process of adsorption is practically reversible with respect to the potential and the bulk concentration of urea. The experimental data were described by the Langmuir and the virial isotherms and the Gibbs energy of adsorption were calculated. The data of the urea adsorption on different electrodes have been compared and the role of the kind of the metal on the adsorption process was discussed. 相似文献
7.
Kurdakova V. V. Kondrat'ev V. V. Malev V. V. 《Russian Journal of Electrochemistry》2003,39(8):878-883
Films of indium(III) hexacyanoferrate are studied in nitrate solutions of lithium, sodium, potassium, and ammonium using cyclic voltammetry and faradaic impedance. Effect of the supporting-electrolyte cation on parameters of the equivalent circuit corresponding to the impedance spectra is analyzed. The charge transport at the electrode/film interface is shown to be slow. The cation bonding in a film is discussed. 相似文献
8.
《Journal of Electroanalytical Chemistry》1987,217(1):15-32
The expression of the current-potential relationship derived in Part I for simple one-step surface redox-electrode reactions of the species confined to electrode surfaces is applied to cyclic voltammetry and the method of faradaic impedance measurements. A method to obtain cyclic voltammograms is presented for a quasi-reversible or general case and equations for reversible and irreversible cyclic voltammograms are derived. The effect of the interaction parameters, W/RT and ΔW≠/RT, kinetic parameters, Λ and α, and coordination number z on the waveform of the cyclic voltammograms is discussed. An interesting feature in the voltammograms, i.e. the appearance of two peaks, is predicted when W/RT < −2.19 for z = 6 in spite of the simple one-step redox process. Furthermore, equations for the faradaic resistance and capacitance are derived and it is shown that the faradaic impedance is independent of the frequency of ac perturbation. 相似文献
9.
The ac admittance spectra of a smooth tungsten carbide (WC) electrode in a stirred H2-saturated 0.5 M H2SO4 solution were measured at hydrogen overpotentials from −0.15 to +0.25 V in the frequency range from 0.1 to 900 Hz, at a temperature of 80°C.An extended analysis of immitance spectra in diagrams of various coordinates led to an interpretation of the system under study at any potential in terms of a linear model which took into account the constant phase element behaviour of the electrode double layer and the presence of two parallel, activation-controlled faradaic processes: the hydrogen ionization/evolution process and an additional electrochemical adsorption reaction passivating the electrode surface for the hydrogen process.Computerized fitting of a rational equivalent circuit to the immitance spectra for all the potentials gave the dependences of the equivalent circuit elements on the potential. The fits proved that the mechanism of the faradaic processes taking place on the electrode is probably the same in the entire range of potentials. 相似文献
10.
B. M. Grafov 《Russian Journal of Electrochemistry》2009,45(9):1041-1044
Noise method for the analyzing of thermodynamic second-order fluctuations of the electrical double layer charge in complicated
electrochemical systems is developed. The method is based on the joint application of the Nyquist fluctuation-dissipation
theorem and Laplace transform. Second-order fluctuations of the free charge in the electrical double layer are studied under
the conditions when the weak-signal faradaic impedance of equilibrated electrode is determined by the diffusion impedance,
alongside with the slow-discharge resistance. It is shown that, unlike the high-order fluctuations, the level of thermodynamic
second-order fluctuations of the free charge does not depend on the mechanism of interaction of the thermodynamic system with
thermostat; it fully corresponds to the conceptions of the Gibbs statistical thermodynamics. 相似文献
11.
The electrochemical kinetic parameters of the V(II)/V(III) couple in HBr solutions of different concentrations were determined from the measurement of faradaic impedance as a function of time during the growth of the dropping mercury electrode. The same method of analysis was applied to the study of the effect of uncharged surfactants on the electrode reaction of Cd(II) in 1 M NaNO3 solutions. The rate constant of the vanadium system decreased with increasing concentration of HBr; this change of the rate constant was discussed in terms of the Frumkin double-layer effect. The relationship between the rate constant of Cd(II) and coverage of the surfactants was not linear, and followed the equation based upon Parsons' model of the blocking effect. The conditional rate constant of Cd(II) in the absence of surfactants was determined to be 0.6–1.1 cm s?1 from the dependence of the rate constant on the coverage. 相似文献
12.
Electrochemical Capacitors 总被引:4,自引:0,他引:4
The current literature sources on the electrochemical capacitors, which are divided into the film (dielectric), electrolytic, and supercapacitors, are reviewed. The supercapacitors are in turn subdivided into the double-layer capacitors, which use the EDL recharge on a highly-developed interfacial surface of electrodes; pseudocapacitors, where the charge is stored in a faradaic pseudocapacitance of sufficiently reversible redox reactions and the EDL capacitance; and hybrid capacitors, which employ a variety of electrodes. A macrokinetic theory of operation of double-layer capacitors is considered. Effect of various factors on the properties of electrodes utilized in supercapacitors is analyzed. A novel type of hybrid capacitor, which has a negative electrode of activated carbon cloth and a PbSO4/PbO2 positive electrode, is proposed. A theory of capillary equilibrium in hermetically sealed electrochemical capacitors is considered. Specific features of the application of voltammetric and impedance methods to studying electrochemical processes in supercapacitors are revealed. Characteristics of electrochemical capacitors and batteries are compared. 相似文献
13.
14.
V. V. Elkin A. I. Marshakov A. A. Rybkina M. A. Maleeva 《Russian Journal of Electrochemistry》2011,47(2):136-146
The negative low-frequency capacitance that appears in interpretations of impedance of the iron electrode in weakly acidic
solutions is shown to arise in the case of interaction of two consecutive nonequilibrium flows that constitute a two-stage
anodic faradaic process of intermediate adsorption in the prepassivation potential range. The low-frequency capacitance is
negative throughout a potential range where the logarithm of rate constant vs. potential (logk vs. E) dependence has the higher slope for the limiting stage. The low-frequency capacitance becomes positive at higher anodic
potentials and for the other limiting stage. 相似文献
15.
A theoretical analysis of the “faradaic demodulation signal” caused by the non-linearity of the faradaic admittance is given for a plane, stationary electrode with a single step electrode process. It is assumed that mass transfer of the substances involved occurs by diffusion only. The theoretical conclusions are tested and confirmed by polarographic measurements with a dropping mercury electrode (DME). 相似文献
16.
A nanostructured manganese dioxide electrode material was prepared using a solid‐reaction route starting with MnCl2·4H2O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with 1 mol·L?1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured γ‐MnO2 and α‐MnO2 containing some bound water in the structure, which was characterized by X‐ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO2 electrode and the MnO2/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO2 electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in 1 mol·L?1 LiOH electrolyte. The MnO2/AC hybrid capacitor with 1 mol·L?1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability. 相似文献
17.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1651-1655
Bipolar electrochemistry is based on the gradient distribution of free‐electron density along an electrically isolated electrode, which causes a positive electrode potential at one end and a negative potential at the other, allowing for wide applications in analytical chemistry and materials science. To take full advantage of its wireless and high‐throughput features, various types of optical probes, such as pH indicators and fluorescence and electrochemiluminescence reagents, have often been used to indirectly monitor the interfacial electron transfer through chromogenic or fluorogenic reactions. Herein, we report the first probe‐free imaging approach that can directly visualize the distribution of the interfacial potential in bipolar electrodes, providing essential information for the validation and development of the theory and applications of bipolar electrochemistry. This approach is based on the sensitive dependence of surface plasmon resonance imaging on the local electron density in the electrode, which enables the direct mapping of potential with a spatial resolution close to the optical diffraction limit, a temporal resolution of 50 ms, and a sensitivity of 10 mV. In addition, in contrast to previous optical readouts that relied on faradaic reactions, the present work achieved the impedance‐based measurements under non‐faradaic conditions. It is anticipated that this technique will greatly expand the application of bipolar electrochemistry as a platform for chemical and biosensing. 相似文献
18.
Electrochemical characterization of gold cysteamine self-assembled monolayer, in situ functionalized with ethylenediaminetetraacetic acid (Au-CA-EDTA SAM), is described by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Osteryoung square wave voltammetry (OSWV). The results obtained by EIS and CV, in the presence of [Fe(CN)6]3−/4− redox probe, show that EDTA is successfully grafted to the surface of Au-CA electrode. Reproducible and reversible variation of the Rct and ΔEp as a function of solution pH show that Au-CA-EDTA SAM is stable in a wide range of pH and potentials. Accumulation of the Pb2+ and Cu2+ ions on the Au-CA-EDTA SAM electrode is investigated using faradaic currents or impedimetric effects measured by OSWV and EIS, respectively. These results reveal the presence of active complexing functional groups of EDTA on the surface, and thus, the formation of Au-CA-EDTA SAM electrode. The new sensor responds to the Pb2+ and Cu2+ separately and simultaneously in a wide linear range of concentrations. 相似文献
19.
The electrochemical activity towards the hydrogen evolution reaction of pressed powder electrodes (Ni---Zn and Ni---Al) was studied in alkaline solutions after leaching out the more active element. These electrodes displayed porous character, and electrochemical impedance spectroscopy was used to characterize surface porosity. The influence of overpotential, temperature, poisons, electrode composition and electrolyte concentration was studied and distinction criteria between faradaic and geometrical effects were formulated. Digital simulations of impedance values in different pore geometries were also carried out. The kinetic parameters of hydrogen evolution were determined. The main factor influencing the electrode activity seems to be the real surface area. 相似文献
20.
Polyaniline films are fabricated on an electrode of mixed indium and tin oxides (ITO) during the cathodic reduction of dioxygen in an aniline-containing solution. Their electrochemical properties are characterized by methods of cyclic voltammetry, faradaic impedance, and chronoamperometry. A quantitative treatment of results that are obtained by the last two methods leads to results that well agree with each other and makes it possible to reliably determine basic charge transport parameters. 相似文献