Cathodic-transfer coefficient

The notation of the transfer coefficients differs in many sources. Some texts use p or (1-P) in place of a. Others use a for the anodic transfer coefficient and p for the cathodic transfer coefficient. Transfer coefficients are typically close to... 

Anodic, cathodic transfer coefficient Dimensionless electrode potential Standard potential of the ion transfer Snrface (excess) concentration of species i, molm initial snrface (excess) concentration, molm Maximal snrface concentration, molm ... 

Figure 5. Measurement and analysis of steady-state i— V characteristics, (a) Following subtraction of ohmic losses (determined from impedance or current-interrupt measurements), the electrode overpotential rj is plotted vs ln(i). For systems governed by classic electrochemical kinetics, the slope at high overpotential yields anodic and cathodic transfer coefficients (Ua and aj while the intercept yields the exchange current density (i o). These parameters can be used in an empirical rate expression for the kinetics (Butler—Volmer equation) or related to more specific parameters associated with individual reaction steps.(b) Example of Mn(IV) reduction to Mn(III) at a Pt electrode in 7.5 M H2SO4 solution at 25 Below limiting current the system obeys Tafel kinetics with Ua 1/4. Data are from ref 363. (Reprinted with permission from ref 362. Copyright 2001 John Wiley Sons.)...

In DMSO solution, the standard rate constant and cathodic transfer coefficient of the Cd(II)/Cd(Hg) system decreased with increasing concentration of TEAP [65]. It was found that a chemical reaction, probably partial desolvation of the reactant, precedes the electron transfer, and Cd(II) is reduced according to the CEE mechanism. The kinetic parameters of this process were determined. 

The cadmium electrodeposition on the solid cadmium electrode from the sulfate medium was investigated [217]. The following kinetic parameters were obtained cathodic transfer coefficient a = 0.65, exchange current density Iq = 3.41 mA cm , and standard rate constant kg = 8.98 X 10 cm s . The electrochemical deposition of cadmium is a complex process due to the coexistence of the adsorption and nucleation process involving Cd(II) species in the adsorbed state. 

The electrochemical reaction ox(sin) + 2e- = red(sin) is first order with respect to the reactant ox. The cathodic transfer coefficient is 0.5. How many times is the excliange current density increased when the concentration of ox is increased ten times (Gokjovic)... 

To make Tafel plots (Figure 8.15) [124,125] subsequent to the subtraction of the ohmic losses (iR), the electrode overpotential, p, is plotted versus ln(.//./0). For systems controlled by standard electrochemical kinetics, the slope at a high overpotential gives the anodic and the cathodic transference coefficients, aA and ac, respectively, and the intercept gives the exchange current density, J0. 

As is perhaps to be expected, the double layer can also affect the values of the measured, i.e. apparent, charge transfer coefficients manifested in the slopes of the Tafel plots (Section 6.6). It is possible to show that, for the Stern model, and considering a cathodic transfer coefficient as example,... 

The exchange current and cathodic transfer coefficient for the PEVD system can be extracted from standard Tafel plots (Figure 40) as described in detail previously, and provide a measure of the nonpolarizability of the solid electrolyte/electrode interface. The values of Ig and at various temperatures are shown in Table 3. The activation energy of the exchange current can then be obtained from an Arrhenius... 

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