Density Functional Theory Study of the Adsorption and Reaction of H2S on TiO2 Rutile (110) and Anatase (101) Surfaces

The adsorption and reaction of H 2 S on TiO 2 rutile (110) and anatase (101) surfaces have been investigated by using periodic density functional theory (DFT) in conjunction with the projected augmented wave (PAW) approach. Adsorption mechanisms of H 2 S, HS, and S on both surfaces were analyzed. It was found that H 2 S, HS, S, and H preferentially adsorb at the Ti 5c, O 2c, (Ti 5c ) 2, and O 2c sites, respectively, on the rutile surface, and at the Ti 5c, (Ti 5c ) 2, (−O 2c )(−Ti 5c ), and O 2c sites, respectively, on the anatase surface. Potential energy profiles of the adsorption processes on both surfaces producing H 2 and H 2 O were constructed using the nudged elastic band (NEB) method. Forming surface sulfur species by a complete O ↔ S exchange at the rutile surface is endothermic by 15.4 kcal/mol and requires a high energy barrier of 35.5 kcal/mol, while it is endothermic by 5.0 kcal/mol and requires a lower energy barrier of 12.4 kcal/mol at the anatase surface. The rate constants for the dehydrogenation and dehydration processes have been predicted.