Band Structure Tuning of TiO₂ for Enhanced Photoelectrochemical Water Splitting

Abstract

Doping with anion and cation impurities is an effective approach to tune the photoelectrochemical properties of TiO2. Here, we explore the Rh monodoping and (Rh + F) codoping effect on electronic structures and photocatalytic activities of anatase TiO2 by performing extensive density functional theory calculations. Upon Rh monodoping, the band gap of TiO2 can be effectively reduced. But this cationic dopant creates an unoccupied intermediate localized state within the band gap, which will act as photogenerated carrier recombination center, which reduces the photocatalytic efficiency. Fortunately, we find that the stable charge-compensated donor–acceptor pair (Rh + F) codoping in TiO2 can effectively reduce the band gap by forming a delocalized intermediate band within the band gap. Moreover, the band edge alignment in the (Rh + F) codoped TiO2 is desirable for water splitting. The calculated optical absorption curve of (Rh + F) codoped TiO2 verifies that it has significantly improved visible light absorption. These findings imply that the (Rh + F) codoped TiO2 is a promising visible light photocatalyst for water splitting.