The hydroxylated and reduced rutile TiO2(011)-2 × 1 surfaces: A first-principles study

The hydroxylated and reduced rutile TiO2(011)-2 × 1 surfaces have been investigated by means of first-principles density functional theory calculations. For the H adsorption and O vacancy on the rutile TiO2(011)-2 × 1 surface, we investigated three different surface O sites. Based on the adsorption and formation energy calculations, we find that the top O is an energetically preferential site for the adsorption of H atom or the formation of O vacancy. The calculated electronic structures indicate that the energetically preferential O site cannot create a band gap state; only the O vacancy at the side O site gives rise to a Ti-3d like defect level at the edge of the conduction band. It is worth mentioning that all considered configurations of the H adsorption and O vacancy on the rutile TiO2(011)-2 × 1 surface obviously enhance the optical absorptions in the areas of infrared, not just the rutile TiO2(011)-2 × 1 surface only has a good absorption edge in the visible light region.