Efficient Photocatalytic Oxygen Production over Nitrogen-Doped Sr4Nb2O9 under Visible-Light Irradiation

Photocatalytic water splitting is an appealing process for solar energy conversions yet it is often limited by the slow oxidation of water to oxygen half-reaction. Here we performed an investigation on N-doped Sr4Nb2O9 as a water oxidation photocatalyst. Our results show that N doping is an effective approach to improve the visible-light response of Sr4Nb2O9. Efficient photocatalytic oxygen production was observed after N doping, and the highest production rate of approximate to 27molh(-1) under visible-light irradiation corresponds to an apparent quantum efficiency of approximate to 0.31%. Clear anodic photocurrent can be generated under visible-light illumination, and the flat-band potential was determined to be approximate to-1.25V vs. Ag/AgCl at pH7. Theoretical calculations reveal that N doping introduces additional valence bands and is responsible for the visible-light response. Variations in light absorption and photo-oxidation performance can be controlled by modifying these valence band positions using different nitridation temperatures.