Insight into the adsorption and decomposition mechanism of H2S on clean and S-covered Au (100) surface: A theoretical study

Density functional theory (DFT) was employed to investigate the adsorption and decomposition of H2S on clean and S-covered Au (1 0 0) surface. Different kinds of possible modes of H2S, as well as HS, S and H adsorbed on both surfaces were considered. It was proposed that H2S prefers to adsorb on the top sites, HS and H adsorb preferentially on the bridge sites, while S atom is opt to occupy the hollow site. In addition, the optimum co-adsorption configurations for HS/H, H/S, H2S/S, HS/S, HS/HS and H/S/S were determined. It was revealed that the co-adsorbed species repel each other slightly on Au (1 0 0) surface and that co-adsorption tends to weaken the adsorbate-substrate interaction due to the presence of atomic sulfur. Finally, the pathways and transition states of H2S dissociation were also investigated. Through comparing the activation barrier on different surfaces, it was found that the presence of S atom can facilitate the first H-S bond scission and go against the second dissociation of HS species. The distinct differences between Au (1 0 0) and Au (1 1 1) surface suggest that the decomposition of H2S over Au-based catalyst is a structure-sensitive reaction. (C) 2014 Elsevier B.V. All rights reserved.