Optical and electrochemical study of cation adsorption on oxide layers on gold and platinum electrodes

It has been shown that the adsorption of Bi3+ and Tl+ cations occurs on oxide layers of Au and Pt electrodes in acid solutions. The initial stages of oxide formation and reduction are inhibited. The effect increases with increasing cation concentration, but diminishes with increasing anion concentration. The adsorption of cations originates in their interaction with the dipoles of the oxide species on Au and Pt surface. A hydrophilic nature of oxidized surface also facilitates this adsorption. Cations apparently affect the state of adsorbed water and decrease the lateral repulsion of oxide species and the electric field in the double layer. This causes a retardation of the place-exchange mechanism, leading to a stabilization of oxides, ie, their more irreversible reduction