Second-generation photocatalytic materials:: anion-doped TiO2

Previous experimental studies describe an efficient photoresponse in the visible-light region for anion-doped TiO2. Doping with carbon, nitrogen, as well as sulfur, yields promising second-generation photocatalysis with TiO2. We present a theoretical investigation of substitutional anion doping in TiO2 and discuss doping effects on the electronic structure, and subsequently the photoactivity. The resulting bandgap narrowing predicted in this work is consistent with experimental observations. Furthermore, we discuss the effects of doping concentration on the localization properties of the valence band edge. Our systematic study of anion-doped TiO2 implies that the carbon-doped TiO2 is the most promising due to a significant overlap between the O 2p state and the carbon states near the valence band edge. Additionally, carbon dopants produce the largest valence band red shift of the three anion-doped TiO2 studied.