Koutecky-Levich equation electrode

The elimination of transport effects is not so readily achieved. One relatively simple procedure is to measure currents (/m) as a function of electrode angular velocity (co) using a rotating disc electrode. Currents free of diffusive transport effects (/k) can then be obtained by application of the Koutecky-Levich equation,... 

Figure 9 Use of the Koutecky-Levich equation to correct for diffusive transport effects on the anodic dissolution of Cu in 1 mol dm-3 NaCl recorded on a rotating disk electrode.

Salimi, A., Banks, C.E., and Compton, R.G. (2003). Ultrasonic effects on the electroreduction of oxygen at a glassy carbon anthraquinone-modified electrode. The Koutecky-Levich equation applied to insonated electrocatalytic reactions. Phys. Chem. Chem. Phys., 5, 3988-93. 

It is left as an exercise for the reader (Problem 9.10) to show that solving this equation for C oCy 0) and use of equations (9.3.23) and (9.3.38) lead to (9.3.39). For another rate-limiting process (e.g., diffusion of an electroreactant through a film coated on the electrode), the term k(E)Co(y — 0) would be replaced by the appropriate expression. This would yield an equation in the general form of the Koutecky-Levich equation, with the extrapolation to 0 allowing the determination of the kinetic parameter for that process [see, for example. Section 14.4.2]. 

The contribution of diffusion overpotential to the total overpotential can be achieved by an increase of convection near the electrode surface. In a very controlled manner this is possible with the rotating disc electrode. In the Koutecky—Levich equation the separation of diffusion contributions and charge transfer contributions to the overpotential was achieved. A general charge transfer reaction with exchange of n electrons was chosen. The Koutecky-Levich equation is... 

RDE is a commonly used technique for investigating the ORR in terms of both the electron transfer process on electrode surface and diffusion—convection kinetics near the electrode. To make appropriate usage in the ORR study, fundamental understanding of both the electron transfer process on electrode surface and diffusion—convection kinetics near the electrode is necessary. In this chapter, two kinds of RDE are presented, one is the smooth electrode surface, and the other is the catalyst layer-coated electrode. Based on the electrochemical reaction 0 + ne R), the RDE theory, particularly those of the diffusion—convection kinetics, and its coupling with the electron-transfer process are presented. The famous Koutecky—Levich equation and its... 

If the electrode is coated with a thin film such as Nafion, the reaction species has to diffuse through it to reach the electrode underneath. The Koutecky-Levich equation then becomes the following ... 

Typical examples discussed below can help us gain a better understanding of the application of RDEs. Jiang et al. [44] studied the ORR at a rotating disk electrode with multiple small potential steps. Figure 21.6 shows a serial of current-potential curves for the ORR at a HT-FeTPP/CoTPP/PG rotating disk electrode in an 02-saturated 0.5 M sulfuric acid electrolyte. With increasing rotation rate, the catalytic current increases. The kinetic analysis of the ORR at the catalyst coated RDE can be carried out by the Koutecky-Levich equation ... 

Kanzaki, Y., Tokuda, K., and Bruckenstein, S. (2014) Dissociation rates of weak acids using sinusoidal hydrodynamic modulated rotating disk electrode employing Koutecky-Levich equation. /. Electrochem. Soc., 161 (12), H770-H779. 

The mass transfer correction for a rotating disk electrode was obtained by rearranging the Koutecky-Levich equation (Eq. (9.46)), and is shown in the following equation ... 

Oct. 14, 1922, Kromeriz, then Czechoslovakia - Aug. 10, 2005, Berlin, Germany) Koutecky was a theoretical electrochemist, quantum chemist, solid state physicist (surfaces and chemisorption), and expert in the theory of clusters. He received his PhD in theoretical physics, was later a co-worker of -> Brdicka in Prague, and since 1967 professor of physical chemistry at Charles University, Prague. Since 1973 he was professor of physical chemistry at Freie Universitat, Berlin, Germany. Koutecky solved differential equations relevant to spherical -> diffusion, slow electrode reaction, - kinetic currents, -> catalytic currents, to currents controlled by nonlinear chemical reactions, and to combinations of these [i-v]. For a comprehensive review of his work on spherical diffusion and kinetic currents see [vi]. See also Koutecky-Levich plot. 

Koutecky-Levich plot — The diffusion-limited current fiim> diff at a -> rotating disk electrode is given by the -> Levich equation based totally on mass-transfer-limited conditions. The disk current in the absence of diffusion control, i.e., in case of electron transfer control, would be... 

The current i in this expression is obtained from the limiting current plateau region in Fig. 2.4. This equation is of quite general validity, and it can also be used to analyze voltammograms obtained for electrocatalysis at multilayered polymer-modified electrodes. Of course the heterogeneous modified electrode rate constant kME takes a different meaning. Thus we note that a plot of versus should produce a straight line, called a Koutecky-Levich plot, whose slope... 

Schmidt et al. used RDE to study the impact of the Nafion film thiekness on the mass transport resistance for HOR (Figure 11.10) [48]). They first deposited a thin layer of Pt/C on the surface of a glassy carbon disk, and covered the Pt/C layer with a thin layer of Nafion. The purpose of the thin Nafion film was to improve the adhesion of the catalyst on the electrode surface. An additional mass transport resistance was encountered due to the presence of this thin Nafion film, and Equation 11.21 applies. Figures 11.10(a) and 11.10(b) show the limiting HOR current densities with 15 and 0.1 pm-thiek Nafion films, respectively. Figure 11.10(c) shows the Koutecky-Levich plot for Nafion films of 0.1, 2.4, 3.6, and 15 pm thickness. Figure 11.10(d) shows the inverse of the Levieh intercept (ca )... 

In the present case this was determined to be is = 0.88 mA cm 2 for a substrate concentration of 1 mM from the intercepts of Koutecky-Levich plots for the oxidation of L-dopa at electrodes coated with identical PVP films to those used for the mediation experiments but which contained the non-mediating surrogate anion Fe(CN)63 instead of IrCle - in an effort to preserve morphology. The values of is for other substrate concentrations were calculated from the relevant equation in Figure 2. In favourable cases (see the mediated oxidation of catechol at a Nafion-Fe(bipy)3 coated electrode below), two distinct waves corresponding to direct and mediated reactions may be observed which greatly facilitates the deter- mination of is. 

The rotating disk electrode measurements for the nanoparticle-deposited diamond film under identical experiments conditions revealed that there was no well-defined limiting current for oxygen reduction, which merges with hydrogen evolution at -0.46 V. From the Koutecky-Levich (K-L) equation, the number of electrons n involved in the reduction was calculated to between 2... 

The Nation coating must protect the underlying sensor elements from compounds in the body, selectively transport O2 relative to glucose, and should preferably inhibit interfering species such as ascorbic acid (2,7J-7J). The permeability of Nation to several compounds was determined using a Nafion-coated rotating disk electrode (79). From plots of the inverse of the observed disk current as a fiuiction of the inverse of the square root of the rotation rate (a Koutecky-Levich plot) the permeability. Pm, was obtained. This value was determined for a series of Nation thicknesses, measured by ellipsometry, and the effective diffusion coefficients were obtained, according to equation 1. 

Sheng et al. [34] recently compared the rotating disk electrode (RDE) studies of the HOR in acid and alkaline and those for the carbon-supported Pt (Pt/C) for the first time. RDE studies are used to separate the current into its kinetic- and diffusion-based constituents, as shown by the Levich-Koutecky equation ... 

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