Boosting simultaneous proton transfer and oxygen activation in hydrogen peroxide photosynthesis via phosphoric...

The practical application of graphitic carbon nitride (g-C₃N₄) in photocatalytic hydrogen peroxide (H₂O₂) production is severely limited by weak oxygen adsorption and activation, together with inefficient proton conduction. Herein, a dual functional modification strategy for g-C₃N₄ is developed through phosphoric acid (H₃PO₄) treatment, which simultaneously introduces surface phosphate ([PO₄]^3-) groups and induces framework protonation, thereby synergistically optimizing the proton-coupled electron transfer (PCET) process. Combined experimental characterization and theoretical calculations demonstrate that modified [PO₄]^3- groups form a bridging POO configuration that promotes oxygen adsorption and activation. Meanwhile, protonation not only enriches surface proton availability but also constructs a hydrophilic proton transport network, markedly reducing the activation energy for proton conduction. These two functions operate cooperatively at neighboring sites, enabling efficient formation and stabilization of the key hydroperoxyl radical (∙OOH) intermediate and thereby favoring a highly selective two-electron oxygen reduction reaction (2e^- ORR) pathway. Consequently, the optimized 5CN-PH exhibits 3.7 times higher photocatalytic H₂O₂ production rate than that of pristine g-C₃N₄, which presents an effective strategy to overcome coupled kinetic limitations in photocatalysis through rational interfacial engineering.