The Ta3N5 semiconductor is a promising photocatalyst but its practical solar-to-hydrogen efficiency is low and the stoichiometric H2 and O2 evolution of Ta3N5 is still difficult. Recent experiments reveal that Ba-doped Ta3N5 presents excellent photocatalytic performance. In this study, density functional theory calculations are performed to unravel the effects of Ba–O codoping on the photocatalytic abilities of Ta3N5. The results reveal that the enhanced photocatalytic activities of the Ba–O codoped Ta3N5 is ascribed to the charge compensation between Ba and O, because the charge compensation induces the cathodic shift of the conduction band minimum of Ta3N5, thus improving the water reduction ability of Ta3N5.
