Sustainable H2O2 photosynthesis by sunlight and air

The photosynthesis of H2O2 is a promising green process that is expected to revolutionize industrial H2O2 synthesis. However, it is still far from application because of the limited performance of photocatalysts. In this study, benzyl alcohol (BA) is excited under UV light with a wavelength shorter than 400 nm after it forms an epoxy with dissolved oxygen to generate high-concentration H2O2 without a photocatalyst. An H2O2 yield of up to 176.43 mM·h−1 in aqueous solution is achieved, which is close to the yield required for commercial production. The by-product benzaldehyde (BD) accelerates H2O2 production in the early stage but consumes H2O2 in the later stage, where it is further converted to benzoic acid (BC). In this photoreaction, only air is employed as the oxidant, and sunlight provides the reaction energy; no photocatalyst is needed. This reaction, combined with a simple mild H2 reduction process using BD, can be used for green closed-loop H2O2 production without waste and by-product discharge, where BA is a recycled intermediate. This study provides a sustainable strategy for low-cost, low-energy H2O2 production with excellent application potential.