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 (SO, far-2SO and near-2SO) are considered, and zinc and oxygen vacancies introduced by SO doping (SO–VZn and SO–VO) are also considered. For SO-doped ZnO, S3p states locate above the top of the valence band and mix with O2p 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 (VO and VZn) shows different features in low energy range. The existence of VO in SO-doped ZnO leads to a strong absorption in UV-light range and VZn plays a critical role in visible-light absorption, which may improve the photocatalytic activity of ZnO in the UV-visible light range, corporately.