An efficient strategy to enhance the photocatalytic activity of Ir-doped SrTiO3: a hybrid DFT approach

Abstract

Photocatalytic water splitting using sunlight is one of the most promising approaches to produce hydrogen, for which increasing focus has been directed towards band gap engineering of the existing photocatalysts, like SrTiO₃. A detailed theoretical study has been carried out to explain the variation of photoactivity of Ir-doped SrTiO₃ with the different oxidation state (+3 and +4) of Ir. The present study reveals that localized mid gap acceptor states are the main limiting factor for the +4 state, which is absent in the case of the +3 state. Furthermore, we have investigated the effect of codoping with B, Al, La, and Cr into Ir-doped SrTiO₃, which releases an extra electron to stabilise the +3 state, and at the same time to form a charge compensated system. To get knowledge about the relative feasibility of formation of various doped systems defect formation energies have been calculated. Finally, the ability to produce hydrogen has been verified by band edge alignment with respect to water redox levels. The present study reveals that although all these four codopant elements ensure the +3 state of Ir, they play differently in enhancing the photoactivity of Ir-doped SrTiO₃. Considering various aspects, it has been predicted that codoping of La into Ir-doped SrTiO₃ can significantly enhance the photocatalytic activity under visible light.