Similarities and Differences Between Electron and Proton Transfers at Electrodes and in Solution. Theory of a Hydrogen Evolution Reaction

Abstract

Depending on the initial energies, a proton transfer may proceed either via a saddle-point in a potential energy surface or by crossing from the reactants' to the products' valley before the saddle-point is reached. In the second path the analogy to weak-overlap electron transfers is pointed out. The present study is intended to unify previously divergent viewpoints, by showing how they are special cases of a more general picture. Expressions are obtained for the reaction rate in terms of the properties of the potential energy surface and of other properties of the system, using a hydrogen evolution reaction as an example.