First-principles study of H2S adsorption and dissociation on Mo(110)

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 0.18-0.31 eV, while it required a high energy barrier of 0.40-0.88 eV on S-covered surface. The second dehydrogenation showed a lower barrier of 85 meV on perfect surface, but a higher barrier of 0.29 eV 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. (C) 2015 Elsevier B.V. All rights reserved.