First-principles study of effect of Si doping on anatase TiO2

In order to investigate the electronic structure and the effect on the photocatalytic activity of Si-doped anatase TiO2, first-principles calculations were carried out based on density-functional theory (DFT). Defect formation energy, energy band structure and density of states (DOS) of Si-doped anatase TiO2 were calculated and compared with the pure anatase TiO2. The results show that Si doping position is related to the preparation conditions, Si is likely to replace Ti under both Ti-rich and O-rich conditions. The lattice parameters and cell volume change to a certain extent after Si-doped TiO2 supercell takes geometry optimized. The distortion of Si-doped TiO2 supercell is helpful to separate the photo-generated electron-hole pairs, which could promote the photocatalytic activity. In substitutional Si to Ti-doped TiO2, the band gap decreases,, induce absorption edge shift to long-wave; in substitutional Si to O-doped and interstitial Si-doped TiO2, the band gap increases, induce absorption edge shift to shortwave. In different Si-doped supercell, the distribution of Si 3p and 3s states is different and cause different electronic structure. (authors)