Crystal face specificity of fluoride adsorption on Ag electrodes: The (111) face

Adsorption of F- on the (111) face of Ag single-crystal electrodes was studied by capacitance measurements in mixed electrolyte solutions of general composition c NaF + (0.04 - c) KPF6. Results have shown that F- ions adsorb more strongly on the (111) face than on the (110) face, a fact which is explained in terms of lower ''hydrophilicity'' of the (111) surface. Adsorption has been found to conform to a virial isotherm with Delta(ad)G(0) increasing linearly and ion-ion interaction decreasing exponentially with the positive charge on the metal. The weaker ion-ion interaction on the (111) face with respect to the (110) face is explained in terms of higher partial charge transfer from F- to the (111) face owing to the higher electronegativity of the latter. Copyright (C) 1996 Elsevier Science Ltd.