Boosted H2O2 Photosynthesis via Synergistic Tuning Electronic Structure and Interfacial O2 Transfer on Floatable Carbon Nitride Networks

Solar-driven photosynthesis of hydrogen peroxide (H2O2) from O2 and H2O offers an eco-friendly and sustainable route. Metal-free graphitic carbon nitride (CN) is capable of photocatalytic H2O2 production, yet its efficiency is limited by insufficient charge separation and slow O2 supply in conventional diphase systems. Herein, we graft cinnamylidene groups into CN to fabricate a hydrophobic CN nanolayer (CNCA/CF). The incorporated cinnamylidene groups with extended conjugated chains narrow the bandgap, promote photocarrier separation and improve 2e ORR selectivity. Benefiting from the hydrophobicity of CNCA/CF, it can stably float on water and construct a gas–solid–liquid triphase interface that enables rapid O2 diffusion and delivery. Moreover, floating CNCA/CF exhibits a high H2O2 output of 1370 μmol m−2 h−1 in a homemade reactor, 15.3-fold higher than that of pristine CN. Mechanistic studies demonstrated that H2O2 is generated through a sequential 2e ORR process involving ·O2− as the crucial intermediate. This work highlights a feasible strategy combining triphase interface optimization with electronic tuning, providing a new platform for the rational design of photocatalysts for H2O2 triphase photosynthesis.