Phosphotungstic Acid Clusters Decorated Znln 2 S 4 Nanoflowers as Molecular-Scale S-Scheme Heterojunctions for Simultaneous H 2 Evolution and Benzyl Alcohol Upgrading.

Simultaneous utilization of photogenerated electrons and holes to achieve overall redox reactions is attractive but still far from practical application. The emerging step (S)-scheme mechanism has proven to be an ideal approach to inhibit charge recombination and supply photoinduced charges with highest redox potentials. Herein, a hierarchical phosphotungstic acid (H ₃ PW ₁₂ O ₄₀ , HPW)@Znln ₂ S ₄ (ZISW) heterojunction was prepared through one-pot hydrothermal method for simultaneous hydrogen (H ₂ ) evolution and benzyl alcohol upgrading. The fabricated HPW-based heterojunctions indicated much enhanced visible-light absorption, promoted photogenerated charge transfer and inhibited charge recombination, owing to hierarchical architecture based on visible-light responsive Znln ₂ S ₄ microspheres, and S-scheme charge transfer pathway. The S-scheme mechanism was further verified by free-radical trapping electron spin resonance (ESR) spectra. Moreover, the wettability of composite heterojunction was improved by the modification of hydrophilic HPW, contributing to gaining active hydrogen (H ⁺ ) from water sustainably. The optimal ZISW-30 heterojunction photocatalyst indicated an enhanced hydrogen evolution rate of 27.59 mmol g ^-1  h ^-1 in benzyl alcohol (10 vol. %) solution under full-spectrum irradiation, along with highest benzaldehyde production rate is 8.32 mmol g ^-1  h ^-1 . This work provides a promising guideline for incorporating HPW into S-scheme heterojunctions to achieve efficient overall redox reactions.
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