Leveraging doping and defect engineering to modulate exciton dissociation in graphitic carbon nitride for photocatalytic elimination of marine oil spill

• P, O dopants and C defect engineering was adopted to modulate g-C 3 N 4 electronic structure firstly. • Synergistic formation of localized defect state by P, O and C v defects is beneficial to excitons dissocation. • POC V N exhibited superior photocatalytic activity for n-tetradecane degradation in seawater. Limited light absorption ability and rapid photogenerated electron-hole recombination severely impedes applications of g-C 3 N 4 . Herein, highly efficient point-defect engineering including dual dopants as well as vacancy was adopted to modulate the photo-induced exciton dissociation kinetics. Specifically, P, O dopants and carbon vacancy modified 3D honeycomb-like POC V N was fabricated through facile one-pot polymerization with (NH 4 ) 3 PO 4 as P, O precursors. The obtained POC V N catalyst exhibited superior photocatalytic degradation performance for n-tetradecane under visible light illumination (38.1 %), which was 4.6 and 1.8 times higher than that of bulk g-C 3 N 4 (8.2 %) and tubular g-C 3 N 4 (21.1 %), respectively. The suppressed recombination of electrons and holes contributed to the superior catalytic performance compared to pristine g-C 3 N 4 , single P and single O doping g-C 3 N 4 . Structural analysis demonstrated P atoms may replace C atoms of N-C = N, O atom located at P-O-C and carbon vacancies located at N = C-N 2 position at heptazine framework. Based on experimental and theoretical analysis, it was found P, O and C v defects prefer to accumulate together in 3-trizine ring, which is conductive to the formation of localized defect state in the band gap region. It resulted in high exciton dissociation efficiency, thus, more reactive radicals were generated. Based on this, degradation path, interference parameter, reactive radicals and toxicity evaluation were investigated deeply and systematically. This work shed light on non-metal green ecological remediation material for marine oil spill.