W-N Bonds Precisely Boost Z-Scheme Interfacial Charge Transfer in g-C3N4/WO3 Heterojunctions for Enhanced Photocatalytic H-2 Evolution

Exploring and achieving precise electron-transfer channels in the interface of Z-scheme heterojunctions are essential and have been considered as immense challenges. A strategy to precisely connect the valence band (VB) site of g-C3N4(CN) with the conduction band (CB) site of WO3through the tungsten-nitrogen (W-N) bond was developed to create a chemically bonded Z-scheme heterojunction photocatalyst. Because of this reason, the photogenerated electrons from the CB site of WO3could be accurately and directly injected into the VB site of CN, following the direct Z-scheme charge separation pathways. The photocatalytic hydrogen production rate of optimal CNWB was 482 μmol h-1, 4.3 times higher than that of CN/WO3without an N-W bond (CNWU). The CNWB also shows better photocatalytic hydrogen evolution activity than the previous CN/WO3systems. Theoretical and experimental results further confirm that the newly formed N-W bonds become metallic, which could act as atomic-level interfacial channels to precisely accelerate Z-scheme interfacial electron transfer and shorten the electron-transfer distance, thus substantially boosting photocatalytic H2generation. This work paves a way to design and synthesize the chemically bonded Z-scheme interface with atomic precision for interesting photocatalytic applications in the future.