Unraveling the mechanism of 720 nm sub-band-gap optical absorption of a Ta3N5 semiconductor photocatalyst: a hybrid-DFT calculation

Abstract

The Ta₃N₅ semiconductor photocatalyst possesses a 720 nm (about 1.72 eV) sub-band-gap optical absorption but the mechanism of this optical absorption is still controversial. In this study, the hybrid density functional theory calculations are performed to unravel the mechanism of 720 nm sub-band-gap optical absorption of Ta₃N₅. By studying the possible optical absorption initiated by the O_N impurity and the V_N defect, we find that the 720 nm sub-band-gap optical absorption of Ta₃N₅ may be ascribed to the electron transition from to . In addition, we propose that the 720 nm sub-band-gap optical absorption can be used to qualitatively evaluate the photocatalytic water splitting ability of Ta₃N₅.