Density Functional Theory Study of the Adsorption and Reaction of H(2)S on TiO(2) Rutile (110) and Anatase (101) Surfaces

Abstract

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 it lower energy barrier of 12.4 kcal/mol at the anatase surface. The rate constants for the dehydrogenation and dehydration processes have been predicted.