Defect-modulated oxygen adsorption and Z-scheme charge transfer for highly selective H₂O₂ photosynthesis in pure water.

Abstract

Solar-driven H₂O₂ production provides an eco-friendly and scalable alternative to conventional anthraquinone processes. However, its efficiency has been limited by the inefficient charge separation and poor selectivity for the two-electron oxygen reduction reaction (2e^- ORR). Here we report a Z-scheme heterojunction photocatalyst constructed by in-situ growth of sulfur-deficient ZnIn₂S₄ nanosheets onto UiO-66-NH₂ (a zirconium-based metal-organic framework). This heterojunction promotes efficient charge separation while retaining strong redox capability, and sulfur vacancies regulate O₂ adsorption into a configuration that suppresses O-O bond cleavage and favors 2e^- ORR. As a result, the composite achieves a high H₂O₂ production rate of 3200 μmol g^-1 h^-1 with 94.3% selectivity in pure water under ambient air and visible light. A continuous-flow prototype exhibits stable performance for over 200 h, and the generated H₂O₂ solution enables direct bacteria disinfection. Spectroscopic and theoretical analyses reveal the critical role of sulfur vacancies in optimizing O₂ activation. Our findings highlight a synergistic strategy of tuning charge dynamics and O₂ adsorption configurations for designing next-generation systems for sustainable H₂O₂ production and water disinfection.