The Chemisorption of 2,3-Dimercapto-n-Propane Sulfonate at the Au(111)-Electrode

Abstract

Abstract In this paper we report on the adsorption behaviour of 2,3-dimercapto-n-propan-sulfonate (DMPS) on the Au(111) electrode. DMPS is a water-soluble dithiol which is unstable in alkaline solution. The absorption decreases by 50 within two hours.The electrochemical behaviour is in accordance to that of other thiols, including monothiols. The interaction between sulfur and the Au(111) surface leads to a strong chemisorption in the double layer region which is limited by the reductive and oxidative desorption, respectively. The oxidative behavior (OD) of DMPS takes place simultaneously with the oxidation of the gold surface itself.We propose a mechanism for the OD which, in contrast to the well-known mechanism of the sulfur oxidation itself, includes the formation of a gold–sulfur complex. This OD mechanism acts like a corrosion and causes an increased roughness of the surface. Therefore, the charge consumed during the OD is exclusively due to the oxidation of Au0 to Au3+ in form of the complex and in form of the well-known Au2O3 oxide.