The study of the mechanism of an electrode reaction by first- and second-order techniques A theoretical approach

Abstract

Abstract The theoretical expressions for the faradaic admittance and the faradaic demodulation voltage are rewritten, introducing the thermodynamic restrictions proposed by Reinmuth in 1972 and without any specification of the mechanism of the electrode reaction.

The result is applied to general first-order kinetics of the type CECEC…etc. A treatment is also given in the case that one or more of the steps are of a higher order. Although the overall rate equation becomes extremely complex in such a case, it is shown that the expressions describing the faradaic admittance and the faradaic demodulation voltage are relative simple.

From some numerical examples it is made clear that, in general, by these methods discrimination between possible mechanisms can be realized on the basis of the potential dependences of the overall rate constant, operational transfer coefficient, irreversibility quotient and demodulation voltage. This work is believed to provide a framework for future quantitative studies of electrode reactions. Some ideas about its possible further elaboration are given.