Synergistic role of oxygen vacancies and heterojunction interface in g-C(3)N(4)/H(2)-annealed SrWO(4) for enhanced photocatalytic H(2) production.

Efficient separation of photogenerated charge carriers remains a critical challenge in the development of high-performance photocatalysts for solar-driven hydrogen production. Herein, a Z-scheme heterojunction composed of H-annealed SrWO (HSWO) and g-CN (CN) is constructed to simultaneously enhance carrier density and suppress electron-hole recombination. H annealing introduces oxygen vacancies into SrWO (SWO), which act as shallow defect states to increase the concentration of photogenerated carriers and extend their lifetimes, thereby providing a rich electron reservoir for hydrogen evolution. Upon coupling with CN, a Z-scheme heterojunction is formed, in which photogenerated electrons from HSWO recombine with holes in CN at the interface. Meanwhile, the electrons remaining in the conduction band of CN actively participate in the hydrogen evolution reaction (HER), while the holes preserved in HSWO maintain strong oxidation capability. This directional charge transfer pathway effectively promote separation while retaining strong redox ability. As a result, the CN/HSWO composites exhibits an excellent H evolution rate of 18.01 mmol·g·h under simulated solar irradiation, along with an apparent quantum yield of 11.4% and a solar-to‑hydrogen efficiency of 0.29%. This work demonstrates that combining Z-scheme heterojunction engineering with defect modulation offers an effective strategy for designing efficient and stable photocatalysts for solar-driven hydrogen production.