Modulated reflectance spectroscopy and voltammetry of the sulphide/gold system

Abstract

The electroadsorption of sulphide species on gold and the growth of sulphur multilayers have been investigated by optical and electrochemical techniques in sodium tetraborate buffer as the supporting electrolyte (pH 7.0 and 9.2) at 25°C. Differential reflectance spectra indicate that the adsorption of sulphide begins inside the hydrogen evolution reaction (HER) region. The HER is catalysed by the presence of sulphide species on the electrode. During the growth of sulphur multilayers, soluble polysulphide species can be optically detected either as intermediates under diffusion-controlled kinetics or as products of a chemical reaction between sulphide ions and the deposited sulphur layer. The steep fall in the integral reflectance at 0.4 V (vs. SHE) is interpreted through the incorporation of light-absorbing polysulphides into the structure of the deposited sulphur layer.