Near-surface hydrogen dynamics in titania

The hydrogen interaction with the TiO2 (110) surface has been investigated using pseudopotential and PAW methods with addition of U Hubbard term. The hydrogen diffusion behavior and thermodynamic properties were calculated by means of full relaxation of structure in every step of bulk diffusion. The results show the existence of potential barriers close to every atomic layer, the trends of barriers and overall system energy lowering away from surface and the occurrence of preferential H sites within each interlayer basin. These findings go in favor of previously experimental findings of TiO2 low surface H coverage and observed easy diffusion of hydrogen from reduced surface into the TiO2 bulk or at least in near surface region.