Faradaic Reaction Involving One Adsorbed Species with Subsequent Desorption

This type of reaction is observed for the underpotential deposition of hydrogen or metals. Unfortunately, the Langmuir isotherm is rarely found in practice, but for more complex isotherms the same impedance plots are observed only the potential dependence of the reaction parameters and Cp is different. In the presence of the 

Frumkin adsorption isotherm with a negative interaction parameter, discontinuous impedances might be observed [203, 204], 

The theory of the process where both Red and Ox species are adsorbed at the electrode surface was analyzed by Laviron [205] and Los and Laviron [206], Recently, such a case was studied experimentally for the redox couple azobenzene/hydrazobenzene at a mercury electrode by Prieto et al. [207] and the rate constants of the sequential protonation-electron transfer reactions were determined. The total impedance in this case is described by the circuit displayed in Fig. 2.35, but the rate constant is a more complex function of the electrode potential because the process involves two protonation and two electron transfer processes. 

2 Faradaic Reaction Involving One Adsorbed Species with Subsequent Desorption 

Let us consider now a more complex reaction where adsorbed species are electro-chemically desorbed in the second reaction  

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Faradaic Reaction Involving One Adsorbed Species with Subsequent Desorption the following equations are obtained ... 

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