First-principles study of dopants and defects in S-doped ZnO and its effect on photocatalytic activity

Electronic structure, optical properties and photocatalytic activity of S-doped ZnO are investigated by density functional theory (DFT). The configurations with the substitution of O by one and two S atoms in different positions (S _O, far-2S _O and near-2S _O) are considered, and zinc and oxygen vacancies introduced by S _O doping (S _O-V _Zn and S _O-V _O) are also considered. For S _O-doped ZnO, S _3p states locate above the top of the valence band and mix with O _2p states, leading to band gap narrowing, but the influence is slight with the increase of doping concentration. The imaginary parts of dielectric functions and absorption coefficients display that S atoms doping is not the critical factor for improving the photocatalytic activity. The absorption coefficient of introduced native defect (V _O and V _Zn) shows different features in low energy range. The existence of V _O in S _O-doped ZnO leads to a strong absorption in UV-light range and V _Zn plays a critical role in visible-light absorption, which may improve the photocatalytic activity of ZnO in the UV-visible light range, corporately.