Concerted Proton‐Electron Transfer in an S‐Scheme PTA/g‐C ₃ N ₄ Heterojunction Enables Efficient H ₂ O ₂ Photocatalysis

ABSTRACT Photocatalytic synthesis of hydrogen peroxide (H 2 O 2 ) is a sustainable route for green chemical production and solar energy conversion, but its practical application is hindered by sluggish oxygen reduction reaction (ORR) kinetics, limited proton availability, and rapid charge recombination. Herein, we report an organic S‐scheme heterojunction photocatalyst (PTA/g‐C 3 N 4 ) that integrates concerted proton–electron transfer (CPET) with interfacial electric‐field regulation to address these challenges. Perylene tetracarboxylic acid (PTA) nanosheets are in situ anchored onto g‐C 3 N 4 via π‐π stacking, forming an intimate heterointerface that simultaneously establishes a built‐in electric field and provides carboxyl‐based proton‐relay sites. This cooperative interfacial design promotes efficient charge separation and facilitates the two‐electron ORR pathway. As a result, the PTA/g‐C 3 N 4 heterojunction achieves a high H 2 O 2 production rate of 2491 µmol g −1 h −1 , corresponding to 4.4‐ and 2.4‐fold enhancements over pristine g‐C 3 N 4 and PTA, respectively, while maintaining excellent cycling stability. Combined photoelectrochemical measurements, in situ spectroscopic analyses, isotope‐labeling experiments, and thermodynamic calculations reveal an S‐scheme charge‐transfer mechanism, in which electrons accumulated on g‐C 3 N 4 drive the selective two‐electron ORR, while PTA carboxyl groups facilitate CPET and stabilize key •O 2 − /•OOH intermediates. This work establishes a CPET–S‐scheme strategy for designing high‐performance organic photocatalysts for visible‐light‐driven H 2 O 2 synthesis.