Theoretical study of metal-doped β-Ga2O3 photocatalysts for overall water splitting

Experimentally, Ca-doped beta-Ga2O3 was found to increase photocatalytic activity by about three times compared with undoped photocatalyst. However, the same host doped with La had minor influence on photocatalytic performance. Doping with Ti leaded to very low H-2 and O-2 evolution rate. In this work, effects of different metal dopants on photocatalytic performance of beta-Ga2O3-based photocatalyst have been explored using first-principles density functional theory calculations. Our calculated results suggest that energy states introduced by dopant Ca in the bandgap of beta-Ga2O3 are close to the valence band maximum. New states allow for efficient electron replenishment and thus reduce the probability of trapping electrons from the conduction band. In contrast, impurity states introduced by dopant Ti are significantly higher than the valence band maximum, which may become an isolated recombination center and thus badly decrease the rate of water-splitting reaction. Adding La had no effect on the electronic structure of beta-Ga2O3, which has seldom influence on photocatalytic activity.