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

Abstract 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.