Anatase TiO2 codoping with sulfur and acceptor IIB metals for water splitting

Abstract

Codoping is an effective method to improve the photoelectrochemical performance of anatase TiO2. In this work, through performing extensive hybrid density functional theory calculations, we explore the (Zn + S) and (Cd + S) codoping effects on the electronic structures and photocatalytic activities of anatase TiO2. Theoretical results clearly reveal that the coupling of the incorporated S dopant with the second-nearest neighboring O atom assisted by the acceptor metals leads to the fully occupied and delocalized intermediate bands within the band gap, which originate from the SO antibonding states (π∗). This kind of metal-assisted SO coupling can not only effectively reduce the band gap of TiO2, but also prevent the recombination of the photogenerated carriers. Moreover, the visible light absorption of anatase TiO2 is significantly enhanced via codoping, and both the reduction and oxidation potentials of water lie within the band gap of the (Zn + S) and (Cd + S) codoped anatase TiO2, which are desirable for photocatalytic water splitting. These theoretical findings imply that the metal-assisted SO coupling is an effectively approach to engineer the band structures and the visible light photoelectrochemical performance of semiconductors photocatalysts.