Effects of native defects on the electronic structure and photocatalytic activity in anatase TiO2 by first principles calculations

Abstract

The crystal structure, electronic structure, optical properties and photocatalytic activity of the native defects in anatase TiO2 were investigated based on the density-functional theory (DFT). The results show that oxygen vacancies (VO) have the lowest formation energy, and thus are easiest to form in the bulk structure. The conduction and valence band moves to the high or low energy region, and the energy gap becomes narrower for the native point defect models. In particular, oxygen interstitials (Oi) have a direct band gap, and new gap states appear in the band gap, which can be responsible for the high photocatalytic efficiency in anatase TiO2. The phenomenon of “impurity compensation” takes place for the oxygen and titanium interstitials. Ti vacancy (VTi) can promote the utilization of solar light by analyzing the absorption spectra. All the calculated results show that Oi and VTi are beneficial in improving the photocatalytic activity of TiO2 in the UV–visible light range.