Synergy of Triphase Interface Engineering and Electronic Modulation of Carbon Nitride Networks for Continuous‐Flow Photosynthesis of H ₂ O ₂

Abstract Artificial photosynthesis of H ₂ O ₂ via 2e oxygen reduction reaction (ORR) by graphitic carbon nitride (CN) is a promising alternative to the energy‐consuming anthraquinone process, however, suffers from limited O ₂ supply, insufficient activity, and extra cost in post‐synthesis separation. To overcome these problems, this work reports a hydrophobic CN/carbon fiber networks based triphase continuous‐flow photoreactor for H ₂ O ₂ photosynthesis, which is enabled by surface chemical modification of CN nanolayer with benzyliamino group. The introduced benzyliamino group imparts hydrophobic surface, extended light absorption, improves charge separation, and favorable O ₂ adsorption and 2e ORR selectivity. Finite element simulation shows fast O ₂ supply at the triphase interface. H ₂ O ₂ production experiments demonstrate an impressive yield of 936 µmol m ⁻² h ⁻¹ when using pure water as proton source, which is >3‐fold higher than in liquid/solid two‐phase system. Systematical mechanism study discloses that O ₂ prefers to be adsorbed at the benzylamino group‐adjacent triazine structure due to the enriched local electron density, and then undergoes a sequential two‐step 1e ORR process to produce H ₂ O ₂ . The synergistic combination of triphase interface engineering and electronic modulation in continuous‐flow photosynthesis of H ₂ O ₂ in this work resolves multiple problems and provides a new avenue for designing advanced photocatalysis systems in liquid–solid–gas triphase reactions.