Hybrid density-functional calculations of formic acid on anatase TiO2 (101) surfaces

Abstract

Recent experimental observations suggested that the presence of oxygen vacancies on TiO2 surfaces affects the adsorption mode of formic acid. We use density-functional theory and the hybrid density-functional HSE06 form for the exchange-correlation functional to determine the structural properties and the 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 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 are responsible for the stabilization of the monodentate mode.