Development in charge transfer theory

Abstract

Basic problems of chemistry at interfaces are connected with the exploration of elementary processes of charge transfer. Multistep and chemical bond formation processes involved in such phenomena have been treated in terms of partial charge transfer models. Related developments since the mid-seventies are briefly addressed in the first part of this paper. These include: the extension of partial charge transfer models to semiconductors; quantum chemical studies of metal and semiconductor electrode processes; developments in the quantum theory of chemical conversion rates in condensed systems; calculation of electronic non-equilibrium related to semiconductor photoelectrochemistry; lastly a brief look is taken at charge transfer on biomembranes. With reference to these topics, the characteristics of λ-, l- and m-type charge transfer are once more explained. In the second part, the problem of chemical processes in electronic non-equilibrium has been taken up, strating from previously developed charge injection considerations. In order to accomplish a connection of quantum theoretical Franck-Condon transition models of chemical species conversion with electronic non-equilibrium of the surrounding medium, a radical reconsideration of basic kinetics proves to be inevitable, even in the limit of integral charge transfer. As a result, a new type of kinetic equations for charge transfer in electronic non-equilibrium has been introduced. The application of these kinetics to light-driven processes on semiconductor surfaces is outlined; as an example of multistep charge transfer, the hydrogen evolution sequence has been considered.