Fabrication of optimal oxygen vacancy amount in P/Ag/Ag₂O/Ag₃PO₄/ TiO₂ through a green photoreduction process for sustainable H₂ evolution under solar light

Defects engineering on photocatalysts such as oxygen vacancies (OVs) is an effective approach for improving photocatalytic hydrogen (H-2) evolution efficiency. In this study, OVs modified P/Ag/Ag2O/Ag3PO4/TiO2 (PAgT) composite was successfully fabricated via a photoreduction process by controlling the ratio of PAgT to ethanol (16, 12, 8, 6 and 4 g center dot L-1) under simulated solar light irradiation for the first time. Characterization methods confirmed the presence of OVs in the modified catalysts. Meanwhile, the OVs amount and their effects on the light absorption ability, charge transfer rate, conduction band and H-2 evolution efficiency of the catalysts were also investigated. The results indicated that the optimal OVs amount endowed OVs-PAgT-12 with the strongest light absorption, the fastest electron transfer rate and suitable band gap for H-2 evolution, leading to the highest H-2 yield (863 mu mol center dot h-1 center dot g(-1)) under solar light irradiation. Moreover, OVs-PAgT-12 exhibited a superior stability during cyclic experiment, indicating its great potential for practical application. Furthermore, a sustainable H-2 evolution process was proposed based on a combination of sustainable bio-ethanol resource, stable OVs-PAgT, abundant solar energy and recyclable methanol. This study would provide new insights into the design of defects modified composite photocatalyst for enhanced solar-to-hydrogen conversion.