Interplay between H2S and Anatase TiO2(101) Surface: The Effect of Subsurface Oxygen Vacancy

The interaction between H2S and oxygen vacancy on the anatase TiO2(101) surface has been theoretically studied by using first-principles calculations. On one hand, it is found that the relative stability of the subsurface and surface V-O could be reversed by H2S adsorption, and the surface V-O becomes energetically more favorable than the subsurface V-O. Meanwhile, the adsorption of H2S also can efficiently facilitate V-O diffusion from the subsurface layer to the surface layer. On the other hand, the results show that both the subsurface and the surface V(O)s can facilitate the H2S dissociation. Subsurface V-O can facilitate the H2S dissociation directly. In contrast, the H2S dissociates on the surface with surface V-O by two indirect pathways. Specifically, after H2S dissociation on the surface with surface V-O, the adsorption of the two complete dissociative H2S are energetically more stable than that of the surface with subsurface V-O, and the sulfur atoms from H2S fill in the surface V-O site and form stable S-doped TiO2 surfaces. This conclusion reveals the essential interaction between H2S and a subsurface oxygen vacancy, which may provide a possible way to illuminate the origin of the photocatalytic activity of the anatase TiO2(101) surface, and offers a possible method to obtain the S-doped TiO2 surface.