The admittance of a simple electrocatalytic process coupled with an additional electrochemical adsorption reaction

Abstract

The admittance of the process ▪ which is under activation control, is analysed in stationary conditions for the case of coupling in parallel with an additional electrochemical adsorption reaction which influences the electrode activity for the main process. The whole system has two time constants. As its equivalent circuit, a two-time constant electrical RC circuit of a particular structure is proposed; this structure consists of two subcircuits coupled in parallel. The use of a multi-time constant RC equivalent circuit for a faradaic process results in most cases in an ambiguous interpretation of the process, since the majority of structures of such circuits have multiple solutions. The choice of the correct interpretation needs reference to arguments outside the scope of ac measurements. It is indicated that the above ambiguity does not appear if one relinquishes the use of equivalent circuits in the modelling of complex faradaic systems.