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Electronic and structural property modulation of SrTiO3 to make it an efficient photocatalyst for overall water splitting and CO2 conversion under visible light irradiation has been an effective strategy to meet the global energy demands. In this context, transition-metal doping has been one of the extensively implemented methods. However, the recent experimental investigations revealed that codoping is a more promising technique than monodoping. An intensive literature study on this issue motivates us to delve into the criteria for codopant selection by theoretical calculations, which eventually paves the way for catalyst design. The present study revealed that doping with only Ni into SrTiO3 is not sufficient enough to achieve photoactivities toward H2 generation and CO2 reduction at the desired level. It has also been explored that the Ni4+ state, which exists in Ni–SrTiO3 in the absence of any defect, is not preferred for achieving significant photoconversion efficiency. Interestingly, the Ni2+ state is found to be the preferred charge state. With the aim to stabilize Ni in the 2+ state, in the present work, we choose transition metals (Cr, W, and Mo), rare earth (La), and nonmetal (F) as codopants. The defect formation energy is evaluated to know the viability of doping. The band edge alignment with respect to water and CO2 redox levels has been analyzed in order to evaluate their water splitting and CO2 reduction performance.
Mantry et al. (Wed,) studied this question.