First-principles studies of H2S adsorption and dissociation on metal surfaces

Density functional theory calculations were employed to investigate the molecular and dissociative adsorption of H2S on the closed packed surfaces of a number of important noble metals (Ag(1 1 1), Au(1 1 1) and Cu(1 1 1)) and transition metals (Ir(1 1 1), Ni(1 1 1), Pd(1 1 1) and Pt(1 1 1)). Energy minima corresponding to adsorbed states were identified with H2S binding preferentially at the top sites. The adsorption of other S moieties (SH and S) was also examined. SH and S were found to prefer bridge sites and hollow sites, respectively. The binding of H2S and its S-containing dissociated species is stronger on the transition metals. The elementary reactions of abstraction of H from H2S to form a surface SH intermediate and abstraction of H from SH to form a surface S intermediate as model pathways for the dissociation of H2S were examined. Our results suggest that H2S decomposition on the aforementioned transition metal surfaces is more facile, both thermodynamically and kinetically.