Tailoring Band Structure of TiO2 To Enhance Photoelectrochemical Activity by Codoping S and Mg

Doping with foreign element is an effective method to narrow the band gap of TiO2. Here, the S doping and (S, Mg) codoping effects on the electronic structure and optical properties of the anatase TiO2 were investigated at the HSE06 hybrid functional level. The hybridization of the O 2p, Ti-t(2g), and S 3p states creates the intermediate band for the doped TiO2, which makes the absorption onset extend into the visible-light region. The introduction of Mg promotes the corporation of S into TiO2. The heavy doping with S further improves the absorption efficiency and eliminates the unoccupied intermediate band. The band alignment confirms that the (S, Mg) codoping with two O atoms substituted by S atoms in TiO2 is desirable for the overall water splitting.