Interactions dans les interphases électrodes polycristallines d'or/solutions acides: Influence de certains anions

Abstract

The interfaces between polycrystalline gold electrodes and solutions of sulfuric or perchloric acids, with or without tungstosilicic anions (DTS), were studied. The explored polarisation range was either limited to potentials lower than those of the oxydation of gold, or enlarged to these potentials. I/E curves and interface impedances in alternative current, have been measured. It has been possible to demonstrate that the existence of remaining adsorbed oxygen “in the electrode surface”, involves a change of the hydrogen evolution potential. This is to be considered for the study of the reduction of DTS anions on gold. Interactions between gold and water molecules strongly disturb anion adsorption in a 1 M H 2SO 4 medium. A step of gold preoxidation has been pointed out when the anions of the solution are not adsorbed (1 M HClO 4). The complex anion (DTS) is strongly adsorbed on the gold surface. Its adsorption is limited by interactions between these ions of high charge. DTS anion adsorption brings about the desorption of other anions, in a 1 M H 2SO 4 medium, thus allowing the partial preoxidation of the gold electrode.