Electrode kinetics with specifically adsorbed reactants: The reduction of some isothiocyanato complexes of Cr(III) on mercury electrodes

Abstract

A series of isothiocyanate complexes of chromium(III) have been studied with regard to their adsorption on mercury and the kinetics of their reduction in the specifically adsorbed state. Rate-potential data at a constant reactant coverage have been analyzed using a theoretical relation derived in a companion paper, and a clear correlation established between these kinetic parameters and the corresponding potential dependence of the adsorption free energies of the adsorbed reactants and products. These, in turn, are closely related to the electronic structure of the adsorbed complexes. Intrinsic transfer coefficients for electrontransfer reactions were evaluated. Some qualitative relationships between the adsorption parameters, relative reactivity and the rate-coverage dependence at constant potential were noted. Diffuse layer effects on the reduction rates of adsorbed reactants are also described.