MgIn2S4/COF S-scheme heterostructure for improved photocatalytic H2O2 production under pure water and air

Photocatalytic H₂O₂ production from O₂ and H₂O is an economical and environmentally sustainable approach. However, the reliance on sacrificial agents and pure O₂ greatly limits the practical application of numerous photocatalysts. Herein, a novel S-scheme photocatalyst composed of MgIn₂S₄ and covalent organic framework (COF) was developed toward efficient photocatalytic H₂O₂ evolution under pure water and air. MgIn₂S₄/COF (MC) S-scheme heterojunction was constructed by decorating MgIn₂S₄ nanosheets on hollow spherical COF using wet chemistry. The H₂O₂ yield of the optimal MC composite in pure water and air was 4.52 mmol⸱g⁻¹⸱h⁻¹ under pure water and air, which was separately 6.6 times and 9.4 times higher than that of pristine MgIn₂S₄ and COF. Photocatalytic mechanism characterizations confirmed that the continuous 2e⁻ O₂ reduction and 4e⁻ H₂O oxidation simultaneously occurred within this reaction system, and both ·O₂⁻ and e^– were pivotal intermediates for H₂O₂ evolution. The MC S-scheme heterojunction was advantageous to the effective separation and transfer of photogenerated electrons and holes, thereby enhancing the photocatalytic H₂O₂ production activity. This work offers important guidance for constructing high-efficiency COFs-based S-scheme heterojunction for H₂O₂ production.