Enhanced photochemical performance of hexagonal WO3 by metal-assisted S–O coupling for solar-driven water splitting

Abstract

Hybrid density functional calculations was used to comprehensively study the electronic structure of S-, Sn- and Pb-monodoped and (Sn, S)- and (Pb, S)-codoped hexagonal WO3 (h-WO3) in order to improve their visible light photocatalytic activity. Results indicate that the (Sn, S)- and (Pb, S)-codoped h-WO3 can realize a significant band gap reduction and prevent the formation of empty states in the valence band of h-WO3, while Sn/Pb-monodoped h-WO3 cannot, because in (Sn, S)- and (Pb, S)-codoping, the S-doping introduces the fully occupied S 3p states in the forbidden band gap of h-WO3 and the acceptor metals (Sn and Pb) would assist the coupling of the introduced S with its nearest O. In particular, the (Sn, S)-codoped h-WO3 has the narrowest band gap of 1.85 eV and highest reducing ability among the doped case. Moreover, the calculated optical absorption spectra show that (Sn, S)-codoping can improve the visible light absorption. In short, these results indicate that the (Sn, S)-codoped h-WO3 is a promising material in solar-driven water splitting.