Diffusion and Reaction of Hydrogen on Rutile TiO2(011)-2×1: The Role of Surface Structure

Abstract

Hydrogen adsorption and reaction on the rutile TiO2(011)-2×1 has been investigated by a combination of high-resolution scanning tunneling microscopy and density functional theory calculations. Hydroxyl formation on the reconstructed surface is weak, and hydroxyls have only been observed on one of the three different surface oxygen sites. Recombination of hydrogen and desorption of H2 is prevented by a large kinetic barrier. Instead, hydrogen is removed from the surface at elevated temperature by diffusion into the bulk. This is contrasted with photoinduced processes investigated by UV–irradiation under ultra high vacuum conditions, which leads to desorption of hydrogen from the surface, indicating a photoinduced lowering of the reaction barrier. Our studies are also compared to previous studies on the rutile TiO2(110) surface where different thermal and photoinduced processes have been reported. These differences are explained by three competing reaction pathways: (i) bulk diffusion, (ii) H2 recombination...