H₂S Adsorption on γ-Al₂O₃Surfaces: A Density Functional Theory Study

The structures and energetics of various adsorption modes of H 2 S on the surfaces of γ-Al 2 O 3 have been determined using periodic density functional theory. The calculations located in total 10 stable adsorption configurations of H 2 S on the dehydrated (100)E and (110)C as well as the hydrated (110)C surfaces of γ-Al 2 O 3, and their binding energies fall in the range of 12−35 kcal/mol, which is in good agreement with experiments. It was noticed that H 2 S prefers chemisorption on clean surfaces free of water, while physisorption becomes important in the presence of surface hydroxyl groups. The computed vibrational frequencies for the adsorbed H 2 S are consistent with the reported values in the literature although slightly overestimated. The variations of the OH stretching modes observed in this study can be properly accounted for in terms of the geometric and electronic structures of the OH groups, the presence of hydrogen bonds, and the surface reconstruction due to H 2 S adsorption.