A combined adsorption isotherm for intermediates formed in electrode reactions

Abstract

A new isotherm is proposed for adsorbed intermediates formed in a charge-transfer process. This combines the functional dependence of θ on E arising from charge-transfer with that from competition with the solvent. The resulting pseudocapacitance/potential relationship is derived and Tafel slopes calculated with the aid of this combined isotherm are discussed. A number of experimental investigations in which the Tafel slope varies with the size of the molecule or with the nature of the solvent are discussed, and the possible application of this approach to the understanding of the mode of adsorption of complex molecules on the surface is emphasized.