Effects of oxygen impurity concentration on the interfacial properties of Ta3N5/Ta5N6 composite photoelectrode: A DFT calculation

The metallic Ta5N6, which is generated during the preparation of semiconductor Ta3N5, interacts with Ta3N5 and forms the Ta3N5/Ta5N6 composite photoelectrode. The oxygen impurity is a natural defect in Ta3N5 and its concentration is probably correlated with the photoelectrochemical performance of Ta3N5/Ta5N6 composite photoelectrode. In this study, density functional theory calculations were performed to investigate effects of oxygen impurity concentration on the properties of Ta3N5/Ta5N6 interface. The results showed that the covalent bonding character became more obvious at the Ta3N5/Ta5N6 interface with the increase of oxygen concentration, leading to the strong connection between Ta3N5 and Ta5N6. The contact between Ta5N6 and oxygen doped Ta3N5 formed the Schottky junction. The built-in potential at the Ta3N5/Ta5N6 interface gradually increased with the oxygen concentration, suggesting that doping with high oxygen impurity concentration was harmful to electron transfer from Ta3N5 to Ta5N6.