First principles study of the role of C in tuning the band gap of Al, Si-doped SrTiO3 to enhance photocatalytic activity

Abstract

This work demonstrates that C-assisted Al, Si-doping can effectively regulate the band structure of SrTiO3 for improving photocatalytic activity. The effects of (Al + C) and (Si + C) co-doping on electronic structure and optical properties of SrTiO3 are performed by first-principles calculations. It is found that the auxiliary effect of the C element on the two doped systems is different. The (Al + C) co-doping effectively passivates the impurity band in the Al mono-doping case, which leads to the expansion of the band gap. On the contrary, the (Si + C) co-doping induces an impurity band near the top of the valence band and narrows the gap, which is ascribed to the strong coupling between C and O atoms. The calculated light absorption curves imply that (Al + C) and (Si + C) co-doping are effective ways to expand the light response region. The further analysis of band edge alignments of both the two co-doped systems indicates that (Si + C) co-doped SrTiO3 is more favorable for water splitting.