Theoretical Study of H2S Dissociation and Sulfur Oxidation on a W(111) Surface

Density functional theory calculations were employed to investigate the dissociative adsorption of molecular H2S on a W(111) surface. The energy minimum of the adsorbed H2S was identified to bind preferentially at the top site. The adsorption sites of other S moieties (SH and S) were also examined, and they were found predominately at the bridge sites between first and second layers and the bridge sites between second and third layers, respectively. The binding of H2S and its S-containing species is stronger on the W(111) surface than on other metal surfaces, such as Pd, Ni, Cu, Au, Ag, and Ir. The elementary reactions of successive abstraction of H from H2S on the surface were examined. We also extend our study to the oxidation reaction of the adsorbed S by adding gaseous oxygen to the surface, which will react with S and eventually form SO2 and then desorb from the surface. Our results show that the above H2S dissociation and sulfur oxidation reactions do not bear high energy barriers and the overall reactions are exothermic on the W(111) surface.