Solar-driven H2O2 production by S-scheme heterojunction photocatalyst

Hydrogen peroxide (H₂O₂), as an essential and green chemical, is extensively used in energy and environmental applications. However, the production of H₂O₂ primarily relies on the anthraquinone method, which is an energy-intensive method involving multi-step reactions, producing harmful by-product wastes. Solar-driven H₂O₂ production, an alternative route for H₂O₂ generation, is a green and sustainable technology since it only utilizes water and oxygen as feedstock. However, the rapid recombination of charge carriers as well as insufficient redox capability limit the photocatalytic H₂O₂ production performance. Constructing step-scheme (S-scheme) heterojunction photocatalysts has been regarded as an effective strategy to address these drawbacks because it not only achieves spatially separated charge carriers, but also preserves redox capability of the photocatalytic system. This paper covers the recent advances of S-scheme heterojunction photocatalysts for H₂O₂ production in terms of basic principles, characterization techniques, and preparation strategies. Moreover, the mechanism and advantages of S-scheme heterojunction for photocatalytic H₂O₂ generation are systematically discussed. The recent S-scheme heterojunction designs, including inorganic-organic heterojunction, inorganic-inorganic heterojunction, and organic-organic heterojunction, are summarized. Lastly, the challenges and research directions of S-scheme photocatalysts for H₂O₂ generation are presented.