LAUSR

Recent experimental observations suggested that the presence of oxygen vacancies on TiO2 surfaces affects the adsorption mode of formic acid (Xu, M.; Catal. Today 2012, 182, 12). Here we use density functional theory and the hybrid density functional HSE06 form for the exchange–correlation functional to determine the atomic geometry and band structure of single molecules on TiO2(101) surfaces. We show that formic acid adsorbs dissociatively on both perfect and defective surfaces with no overlap between oxygen defect states and molecular states, leading to no change in the adsorption mode. We propose that both relaxation experienced by the surface atoms due to the presence of vacancies and molecule adsorption affect the electronic structure of the surface, leading to stabilization of the monodentate mode.