First-principles study of H2S adsorption and dissociation on Mo(1 1 0)

Abstract

The dissociative adsorption of H2S on perfect and S-covered Mo(110) surfaces have been studied using density functional theory. Adsorption mechanisms of H2S, SH, S and H on both surfaces were analyzed and all possible potential energy profiles of H2S dissociation processes were mapped out. It indicated that H2S, SH, S, and H energetically favor the short bridge, long bridge, hollow, and hollow sites, respectively, on perfect surface, and favor the top, long bridge, hollow, and hollow sites, respectively, on S-covered surface. The first H2S dehydrogenation on clean surface has a barrier of 0.18–0.31eV, while it required a high energy barrier of 0.40–0.88eV on S-covered surface. The second dehydrogenation showed a lower barrier of 85meV on perfect surface, but a higher barrier of 0.29eV on S-covered surface. All these findings indicated that H2S can easily decompose on perfect Mo(110) surface, but the presence of atomic sulfur went against the H–S bond-breaking process both thermodynamically and kinetically. Finally, densities of electronics states and vibrational frequencies have been used to characterize the interactions between adsorbed species and the substrate.