Site-binding model of the electrical double layer at the oxide/water interface

Abstract

A site-binding model of the oxide/aqueous electrolyte interface is introduced, in which it is proposed that the adsorbed counter ions form interfacial ion pairs with discrete charged surface groups. This model is used to calculate theoretical surface charge densities of the potential-determining (H+/OH–) ions and the potential at the Outer Helmholtz Plane, which are shown to be consistent with experimental data for oxides. An explanation is provided for the difference between silica and most other oxides in terms of the dissociation constants of the surface hydroxyl groups.