Adsorption of S2− and HS− ions on the (111) face of coinage metals: A quantum-chemical study.

The interactions of S 2− and HS − ions with gold, silver, and copper were studied by density functional theory using the cluster model of the metal surface. The geometrical and energy characteristics of the interactions of these ions with the surface metal atoms were evaluated. The S 2− ions form stronger chemical bonds with the surface metal atoms than HS − ions. A significant charge transfer from anion to metal occurs during the adsorption. The adsorbability increased in the series Ag < Cu < Au for both anions. The HS − ion showed greater ability to be transferred to the surface during the electrochemical adsorption due to the strong hydration of the S 2− ion. In alkaline media, however, the dissociation of the adsorbed HS − leads to its conversion to S 2−. [ABSTRACT FROM AUTHOR]