Modulating Active Hydrogen Supply and O₂ Adsorption: Sulfur Vacancy Matters for Boosting H₂O₂ Photosynthesis...

Photocatalytic two-electron oxygen reduction reaction (2e^- ORR) represents a promising approach for H₂O₂ production. However, the lack of photocatalysts with appropriate O₂ adsorption and hydrogenation capabilities impedes the H₂O₂ production performance. Herein, we report the synthesis of Ni-doped ZnS hollow nanocubes with S vacancies (Ni-ZnS-Sv) as a dual-site 2e^- ORR photocatalyst for efficient H₂O₂ production. Experimental results and density functional theory calculations reveal the vital roles of Sv in modulating the electronic structures of Ni and S dual sites toward enhanced 2e^- ORR selectivity and activity. The atomically dispersed Ni sites with electron-rich state enable a Pauling-type (end-on) O₂ adsorption configuration and a modest binding strength of O₂ and OOH*, largely avoiding the O─O bond cleavage. Besides, the formation of electron-deficient S sites weakens the S─H_ads bond, facilitating *H_ads migration to adjacent Ni sites and accelerating the hydrogenation kinetics of O₂ to OOH* intermediate. As a result, the elaborately designed Ni-ZnS-Sv photocatalyst exhibits a high H₂O₂ yield of 5649.49 µmol g^-1 h^-1 under UV-vis light irradiation in pure water. Our work offers new insights into the design principles of high-performance photocatalysts for artificial H₂O₂ photosynthesis systems.