Band gap engineering of SrTiO3 for water splitting under visible light irradiation

The electronic structures of pure, mono-doped (either Mo or N), and co-doped (Mo and N) SrTiO3 are calculated by first principles with the Tran-Blaha modified Becke-Johnson potential. Results show that the calculated band gap of SrTiO3 is improved from 1.87 to 3.27 eV by this new method, being in good agreement with the experimental value. Mo and N co-doping can prevent not only the partially occupied states from appearing at the band edge but also the two N atoms coupling. Therefore, the high activity of photocatalysis remains and the band edges are compatible with the redox potentials for water splitting. More importantly, the band gap of the most stable co-doped configuration is sharply narrowed to 2.07 eV. The defect formation energy calculations indicate that the co-doped systems are energetically favorable in Ti-poor and O-rich environments. These show that Mo and N co-doped SrTiO3 should be a good candidate for water splitting using sunlight.