AQY Beyond Expectations: Hydrogen Radical-Enabled Photosynthesis of H2O2 under Mild Conditions

In this study, a promising high-efficiency H2O2 photosynthesis process using diphenylmethanol (DPM) as the substrate is reported to improve the practicality of attractive sunlight-driven catalyst-free H2O2 production. The acquired H2O2 yield reaches 109.57 mM·h–1 with an unexpected apparent quantum yield (AQY) of 56.62% at 20 °C, and sharply increases to 194.64 mM·h–1 with increasing AQY of 242.37% at 60 °C, which is close to that of the current anthraquinone method in the industry. Using the mixture system of DPM and 1-phenylethanol, the final H2O2 output concentration is 6386 mM, equivalent to 21.71 wt %. Such a process with industrial prospects is confirmed to be based on a newly found hydrogen radical mechanism rather than traditional hydrogen abstraction by oxygen. Direct homolysis of the benzylic C–H bond occurs under ultraviolet (UV) light irradiation and enables H2O2 generation after reacting with oxygen. The two benzene ring groups of DPM promote the reactivity of the benzylic C–H bond through an electron-withdrawing effect, and the product, benzophenone, enhances the photoreaction dynamics by its autocatalytic effect. These findings highlight the tremendous potential of catalyst-free H2O2 photosynthesis, offering a new pathway for sustainable green H2O2 production.