Facile one-pot synthesis of defect-engineered step-scheme WO3/g-C3N4 heterojunctions for efficient photocatalytic hydrogen production

Abstract

Constructing step-scheme (S-scheme) heterojunctions is one of the efficient strategies to enhance photocatalytic processes, but unfortunately their synthesis requires complex procedures. Here, we develop a facile methodology for one-pot synthesis of defect-engineered S-scheme WO₃/g-C₃N₄ heterojunctions. The as-synthesized sample (15.0WCN) exhibits a remarkable photocatalytic hydrogen generation rate (1034 μmol h⁻¹ g⁻¹), which is 1.7 and 4.5 times higher than that of normal S-scheme WO₃/g-C₃N₄ heterojunctions (15.0W + CN) and pure g-C₃N₄, respectively. We discover that surface oxygen vacancies can improve the separation efficiency of photogenerated carriers by acting as a mediator between the valence band of g-C₃N₄ and the conduction band of WO₃, while bulk oxygen vacancies mainly enhance visible light absorption through narrowing the band gap in the S-scheme system. In addition, our studies show that surface oxygen vacancies are more effective than bulk ones in S-scheme heterojunctions for photocatalytic hydrogen production. This work affords a new insight into coupling strategies of defect-engineering and S-scheme heterojunctions, which is helpful for designing other efficient photocatalytic systems.