Insight into the adsorption and decomposition mechanism of H₂S on clean and S-covered Au (1 0 0) surface: A theoretical study

Highlights: • Dehydrogenation mechanism of H₂S on clean and S-covered Au (1 0 0) was firstly studied using periodic DFT calculations. • The optimized structures and adsorption energies were obtained. • The results give the performance of using atomic sulfur to modified Au (1 0 0) surface. • The energy barriers and reaction energies were calculated. - Abstract: 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