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

Abstract

The adsorption and reaction of H₂S on TiO₂ 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 H₂S, HS, and S on both surfaces were analyzed. It was found that H₂S, 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 H₂ and H₂O 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.