Engineering g-C3N4 with chlorine for efficient visible-light photocatalysis: Mechanistic insights into charge separation and pollutant degradation

With the rapid development of industrialization and urbanization, the removal of organic pollutants from water has emerged as a significant challenge. To overcome the limitations of traditional g-C 3 N 4 photocatalysts, including a wide bandgap and high carrier recombination rate, this study successfully synthesized chlorine-doped carbon nitride (ClCN) via an ammonium chloride pyrolysis self-doping method. The reduction in work function significantly improved charge separation efficiency, while the p orbitals of Cl introduced new energy levels near the valence band, facilitating electron delocalization and enhancing carrier migration. Experimental results demonstrated that the degradation efficiencies of Rhodamine B (RhB) and tetracycline hydrochloride (TC) by the optimized 3ClCN sample reached 99.8 % (k = 0.11465 min −1 ) and 82.5 % (k = 0.03179 min −1 ), respectively, markedly surpassing those of pristine g-C 3 N 4 . Cycling tests confirmed the excellent structural stability of the material, and active species trapping experiments indicated that h + and ·O 2 − played dominant roles in the degradation process. Density functional theory (DFT) calculations revealed that chlorine doping effectively narrowed the bandgap, thereby extending the visible light absorption range. Furthermore, the 3ClCN catalyst exhibited robust adaptability in complex water matrices, offering a highly efficient and stable solution for green water treatment technologies.