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

Graphical Catching the rays : Nitrogen doping is an efficient approach to endow the wide-band-gap semiconductor Sr 4 Nb 2 O 9 with visible-light responses. Efficient photocatalytic oxygen production from water is achieved with this N-doped Sr 4 Nb 2 O 9 under visible-light illumination, which is influenced strongly by synthetic conditions. DFT calculations reveal the critical role of nitrogen, which forms additional energy levels within the band gap of Sr 4 Nb 2 O 9 . 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 Sr 4 Nb 2 O 9 as a water oxidation photocatalyst. Our results show that N doping is an effective approach to improve the visible-light response of Sr 4 Nb 2 O 9 . Efficient photocatalytic oxygen production was observed after N doping, and the highest production rate of ∼27 μmol h −1 under visible-light irradiation corresponds to an apparent quantum efficiency of ∼0.31 %. Clear anodic photocurrent can be generated under visible-light illumination, and the flat-band potential was determined to be ∼−1.25 V vs. Ag/AgCl at pH 7. 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.