Abstract Based on ab-initio calculations, the effect of Cu, N and S doping in anatase TiO 2 is investigated. Copper (Cu) doping in anatase TiO₂ reduces the band gap of pristine TiO₂ from 2.17 eV to 1.85 eV by introducing Cu 3d states near the valence band maximum. In Nitrogen doped TiO 2 , the isolated N 2p states appears just above the valence band maximum, which can promote the electron-hole recombination and may limit the photocatalytic efficiency. Sulfur (S) doping lowered the band gap from 2.17 to 1.89 eV. The nitrogen and sulfur co-doping significantly narrows the band gap (1.55 eV) by introducing N 2p and S 3p states above the valence band maximum. In Cu, S codoped TiO 2 , the distance between top of valence band and bottom of the conduction at gamma point is 1.86 eV. The narrow band gap of 1.80 eV in tri-doped model (CuNS@TiO 2 ) is attributed to the simultaneous creation of Cu 3d, N 2p, and S 3p states. The effective hybridization of Cu 3d, N 2p and S 3p with the host O 2p and Ti 3d states plays significant role in shifting the absorption edge toward visible regime. The optical absorption coefficient indicates that CuNS@TiO₂ exhibits the most promising absorption among the studied systems providing a suitable alternative photocatalyst working under visible light illuminations.
Khan et al. (Wed,) studied this question.