Boosting Photocatalytic Hydrogen Peroxide Production via Multiscale Engineering O-Doped g-C₃N₄/CuO Nanosheets

Graphitic carbon nitride (g-C₃N₄) is a promising semiconductor for solar-to-chemical conversion, yet its practical application in hydrogen peroxide (H₂O₂) photosynthesis is severely limited by inefficient charge separation and rapid electron-hole recombination. Herein, we report a synergistic multiscale engineering strategy to construct O-doped g-C₃N₄/CuO (CuO/O─C₃N₄) heterostructures designed for highly efficient photocatalytic H₂O₂ production. By integrating atomic-level oxygen doping with interface-level CuO coupling, this strategy simultaneously regulates the intrinsic electronic structure of g-C₃N₄ and establishes an efficient interfacial charge-transfer pathway. The optimized CuO/O─C₃N₄-2 composite achieves a high H₂O₂ concentration of 3978 μmol L^-1 under visible-light irradiation in an acidic medium with HCOOH as a sacrificial agent, significantly outperforming pristine g-C₃N₄. Comprehensive characterizations and theoretical insights reveal that the dual-functionalization of oxygen-induced electronic modulation and CuO-mediated interfacial charge transfer synergistically promote carrier separation and facilitate the two-electron oxygen reduction reaction. This work provides a sophisticated paradigm for the rational design of g-C₃N₄-based systems toward sustainable solar-fuel production.