Theory of electron-transfer rates across liquid-liquid interfaces

Abstract

The theory developed in a previous paper for the geometry of the encounter complex, the reorganization energy, and the electron-transfer rate constant at a liquid-liquid interface is applied to existing data on the rate constant. To treat cyclic voltammetric (CV) studies of electron transfer across the interface, the nature of the encounters is examined and a bimolecular-type rate treatment is used. When one redox pair is in large excess, it has been pointed out that a single-phase CV analysis for diffusion/reaction can be utilized. In the present paper we avoid in this analysis the assumption that the second ("concentrated") phase is metallike. The experimental result deduced in this way for the true exchange current electron-transfer rate constant at the interface is compared with that estimated from the present theory of the rate constant, using metal-liquid electrochemical exchange rate constants. The type of agreement found is encouraging, considering the various approximations involved, and further experimental studies and tests would be of interest.