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.