Hydrogen interaction with the anatase TiO ₂(101) surface

The interaction of atomic hydrogen with the majority (101) surface of anatase TiO ₂ is studied using density functional theory calculations both with a standard semi-local functional and with the inclusion of on-site Coulomb repulsion terms. We investigate the energetics of different adsorption configurations at surface and subsurface sites and different coverages, from low to one monolayer, as well as diffusion pathways among the different sites and recombinative H ₂ desorption barriers. While H ₂ desorption is the energetically most favorable process, the diffusion of H into the subsurface is found to be at least equally favorable kinetically. It is further shown that subsurface oxygen vacancies on reduced anatase are favorable adsorption sites for hydrogen atoms.