Electronic and optical properties of S/I-codoped anatase TiO2 from ab initio calculations

• There are some hybridized states appearing in the band gap for codoping TiO2.
• The band gap of S/I-codoped system has a decline compared with the pure TiO2.
• The synergistic effect of S/I codoping TiO2 induces the redshift of absorption edge.
• Photocatalytic activity of S/I-codoped TiO2 were explained by the DFT calculations.

Electronic and optical properties of S-doped, I-doped, and S/I-codoped anatase TiO2 were successfully calculated and simulated using the density functional theory. The calculated results show that the overlap of S 3p and O 2p states leads to the band gap narrowing in S-doped system, and the band gap narrowing is not caused with the mix of I 5p and Ti 3d states. However, there are some hybridized states of S 3p and I 5p appearing in the forbidden gap of S/I-codoped anatase TiO2, and the band gap has a narrowing compared with the pure anatase TiO2. These results lead to a red-shift of optical absorption edge and reduce the recombination of photogenerated electron-hole pairs, which enhance the visible-light photocatalytic activity of S/I-codoped anatase TiO2.