The influence of ion pairing at the electrode/solution interface on the kinetics of heterogeneous electron transfer

Abstract

A model is developed for the accelerating effect of non-reacting ions adsorbed on the inner Helmholtz plane on the kinetics of electron transfer to a reactant which is also situated on the same plane near the electrode. It is assumed that the charge density of non-reacting ions around the reacting ion can be described by a two dimensional distribution function analogous to that used by Fuoss to describe ion pairing in the bulk of the solution. Kinetic equations are presented in which the discreteness-of-charge terms are explicitly included and the magnitude of these terms is estimated on the basis of a simple model. The estimates show that the acceleration of hydrogen ion in the presence of adsorbed iodide ions can be attributed to the electrostatic effect of the surrounding ionic atmosphere.