Metal oxide-based heterojunctions for photocatalytic hydrogen peroxide production: mechanism, progress, and challenges

Photocatalytic production of H₂O₂, as a sustainable and green route, has garnered widespread attention. Among various photocatalysts, metal oxides have emerged as research hotspots in photocatalytic H₂O₂ production in terms of their versatility including low cost, suitable band positions, good stability, easy synthesis, and biocompatibility. However, during photocatalysis, the fast recombination of photogenerated electron-hole pairs on the mono-component materials severely limits the photocatalytic property of H₂O₂ production. To address this critical issue, the design of metal oxide-based heterojunctions can not only significantly expedite the separation of photogenerated electron-hole pairs but also extend the light absorption range, provide more active sites, and achieve multifunctional synergistic catalysis, thereby enhancing the performance of photocatalytic H₂O₂ production. This review systematically summarizes the recent progress of metal oxide-based heterojunctions for H₂O₂ synthesis. Firstly, this review analyzes the catalytic mechanism of H₂O₂ and outlines the stepwise progression of various heterojunctions. The research advances of metal oxide-based heterojunctions in photocatalytic H₂O₂ production are comprehensively reviewed, such as metal oxide-conductor heterojunctions, metal oxide-C₃N₄ heterojunctions, metal oxide-metal oxide sulfide heterojunctions, metal oxide-metal sulfide heterojunctions, and metal oxide-organic framework heterojunctions. Especially, the structure-activity relationship of the photocatalysts is critically discussed. The challenges and future development directions in photocatalytic H₂O₂ production are also analyzed. This review will give insight into the metal oxide-based heterojunctions and hopes to provide a reference value for the future design of heterojunctions in effective H₂O₂ photosynthesis.