Effect of electrolyte on surface potential of haematite in aqueous electrolyte solutions

A method for determination of the surface potential Ψ 0 by single crystal metal oxide electrodes is demonstrated. Theoretical analysis of metal oxides using the surface complexation model was based on the general surface reaction equation. It was shown that the slope of Ψ 0 (pH) function should be lower than the Nernstian slope. This reduction was found to depend on the nature of the counterions and to be more pronounced at higher electrolyte concentrations. Quantitative analysis of the surface potential data enables evaluation of the ratio of surface concentrations of positive (protonated) to negative (deprotonated) surface sites, as well as activity coefficients of charged surface species. These data, along with data obtained by other methods, enable complete characterisation of the electrical interfacial layer at the metal oxide aqueous interface.