Proton reservoirs in polymer photocatalysts for superior H2O2 photosynthesis

Abstract

In H₂O₂ photosynthesis from water and O₂, a paradox occurs that the kinetically sluggish half-reaction of water oxidation performs as the proton source for the kinetically faster O₂ reduction, thus limiting the overall efficiency of the photoreaction. One possible approach to address this paradox is to incorporate surface sites of proton reservoirs into the photocatalyst, which helps balance the supply and demand of protons in the two half-reactions. As a proof of concept, by tuning the feeding ratio of precursors of quinone-amine polymers (QAPs), hydroquinone units were co-fabricated as proton reservoirs. The QAP with an enriched hydroquinone content exhibited a 3.5-fold increase in photocatalytic H₂O₂ production compared to that in the absence of hydroquinone. More impressively, distinct from the reported photosynthesis systems that mainly employed a pure O₂ atmosphere, the hydroquinone-enriched photocatalyst demonstrated more efficient utilization of O₂, allowing the direct use of air as an oxygen source for H₂O₂ synthesis. Owing to the adaptability to ambient conditions (air and natural water), the hydroquinone-enriched QAP has great potential in practical applications. This work reveals a specific strategy for optimizing H₂O₂ photosynthesis by modulating proton supplementation.