W–N Bonds Precisely Boost Z-Scheme Interfacial Charge Transfer in g-C3N4/WO3 Heterojunctions for Enhanced Photocatalytic H2 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 WO3 through 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 WO3 could 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/WO3 without an N–W bond (CNWU). The CNWB also shows better photocatalytic hydrogen evolution activity than the previous CN/WO3 systems. 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 H2 generation. 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.