Light-Induced Efficient Hydrogen Peroxide Production Mediated by an Integrated Catalytic Microenvironment on Carbon Quantum Dots

Proton-coupled electron transfer (PCET) has emerged as a promising strategy for boosting hydrogen peroxide (H2O2) production through the two-electron oxygen reduction reaction (ORR). To achieve efficient H2O2 production, a specific C═N–NH–C═O structure was engineered on CQDs through Schiff-base addition reaction, creating an ideal catalytic microenvironment within the molecule via the integration of a proton donor and oxygen adsorption site. Benefiting from that, the obtained benzohydrazide-modified CQDs (BD-CQDs) exhibited a H2O2 production efficiency of 1562 μmol g–1 h–1 even without an external oxygen supply and electron donor, nearly three times that of the pristine CQDs. Mechanism investigation verified that oxygen adsorption shifted from a side-on type to an end-on type after modification, and the O═O bond was stretched on the C═O adjacent to −NH–, improving H2O2 selectivity to 92.5%. Identification of active sites revealed that −NH– provided sustainable proton flux for PCET, while the C═N bridge boosted the charge separation and transfer. Owing to the spatial proximity within the integrated catalytic microenvironment, the proton transfer energy barrier was significantly decreased, thermodynamically favoring H2O2 production. BD-CQDs retained an efficiency of over 88% after five successive cycles or in an ionic environment, highlighting their practical application potential in photocatalytic energy conversion.