First-Principles Calculation of Cr/S Co-doped Rutile TiO₂

The electronic structures and optical properties of pure, Cr, S single- and Cr/S co-doped rutile TiO₂ were calculated by the first-principle plane wave pseudopotential method based on density functional theory. The calculated results indicate that the three different doping ways can lead to lattice distortion in the rutile TiO₂ and introduce local electronic states in the forbidden band of TiO₂. The local energy levels in the forbidden band of TiO₂ are mainly contributed by Cr-3d and S-3p orbital. Compared with pure TiO₂, the absorption edges (i.e. the edge of the main peak) of the doped TiO₂ have different blue shifts; however, the light response ranges of the doped systems are extended, especially in the case of Cr single- and Cr/S co-doped TiO₂. The extension of the visible light response range of the doped TiO₂ may enhance its visible light photocatalytic performance. In addition, the co-doped TiO₂ has a stronger oxidation ability, which may increase the catalytic efficiency of TiO₂.