Crystal face specificity of incipient oxidation of Ag single crystal electrodes in acidic aqueous solution

The onset of anodic oxidation of Ag single crystal face electrodes in acidic solution is investigated by means of capacitance and voltammetric curves. The potential of incipient oxidation is found to depend only slightly on the atomic density of the surface. On the other hand, a pre-monolayer oxidation peak is identified only for the (110) face in HClO4 while in H2SO4 it is suppressed. Results are interpreted in terms of anodic oxidation vs. anodic dissolution interference and anion adsorption vs. water oxidation competition. The behavior of the (110) face is explained on the basis of a model for water adsorption proposed for UHV experimental data. The higher reactivity of the (110) face toward water molecules supports the "hydrophilicity" scale of Ag crystal faces based on ionic and non-ionic adsorption data.