Enhanced molecular dipole moment driven charge separation accelerates Fe(II)/Fe(III) cycle in oxygen doped g-C3N4 microrods for scavenger-free photocatalysis-self-fenton degradation

A photocatalysis–self-Fenton system (PSFs) offers a viable solution to the continuous hydrogen peroxide (H 2 O 2 ) dosing and insufficient Fe 2 + regeneration challenges in conventional Fenton chemistry. An oxygen-doped g-C 3 N 4 microrod (OCNT)-based PSFs was synthesized via a facile oxalic acid-mediated supramolecular self-assembly route, enabling efficient pollutant degradation. In situ H 2 O 2 production was achieved through a two-electron oxygen reduction reaction (2e − -ORR), with photogenerated electrons accelerating Fe 2+ /Fe 3+ cycling and enhancing H 2 O 2 utilization. The system exhibited an apparent rate constant of 0.071 min −1 for tetracycline (TC) removal, 12.2- and 4.2-fold higher than pristine g-C 3 N 4 and a photo-Fenton system, respectively. Density functional theory (DFT) calculations and experimental results indicated that oxygen heteroatom doping increased the molecular dipole moment and optimized the band structure, while the one-dimensional microrod morphology exposed abundant active sites. These synergistic effects facilitated charge-carrier separation, improved interfacial mass transfer, and promoted the two-electron oxygen-reduction pathway, thereby accelerating Fe 2+ /Fe 3+ cycling and hole oxidation. The platform demonstrated broad pH adaptability, strong anti-interference capability, and long-term operational stability. This work provides an effective strategy for on-site H 2 O 2 generation and utilization in photocatalytic–Fenton systems for the degradation of organic contaminants.