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. (C) 2012 Elsevier B.V. All rights reserved.