Density functional theory of Ca/F co-doped anatase TiO2

Abstract

In order to understand the improved photocatalytic activity of Ca/F co-doped TiO2, the lattice parameters, energy band structures, density of states and absorption spectra of pure, Ca doped, F doped and Ca/F co-doped anatase TiO2 were calculated by first principles based on the density functional theory. It was found that the doping can result in lattice distortion of TiO2, especially the biggest lattice distortion was generated by the Ca/F co-doping. The forbidden energy band width of anatase TiO2 was broadened by Ca or F doping, while it was reduced by Ca/F co-doping. The calculated electronic density of states indicated that Ca doping provided contribution to the valence band of TiO2, and F doping resulted in the highest energy level occupied by electrons appeared in the conduction band. The energy band of TiO2 almost kept unchanged after Ca/F co-doping except the reduction of forbidden band width. Therefore, the experimentally obtained photocatalytic activity improvement of TiO2 co-doped with Ca and F may have resulted from the reduction of forbidden band width of TiO2.