Electron bridging enhanced peroxydisulfate activation and 4-chlorophenol degradation enabled by doping carbon into graphitic carbon nitride

Abstract

The peroxydisulfate (PDS)-based advanced oxidation process (AOP) has attracted great attention as an effective technique for oxidatively decomposing organic pollutants. g-C₃N₄, an excellent photocatalyst, has been studied to activate PDS, but the rapid photogenerated electron-hole recombination severely impedes its photocatalytic performance. Herein, highly efficient point-defect engineering by doping atoms as well as vacancies was adopted to modulate photoinduced exciton dissociation kinetics. We successfully synthesized C-doped carbon nitride (xC-g-C₃N₄) by a one-step copyrolysis method using glucose and melamine as raw materials. C-doped carbon nitride can act as an electron bridge for electron transfer, leading to xC-g-C₃N₄ with a wider light absorption range (from 475 nm to 527 nm), narrower band gap (from 2.76 eV to 2.66 eV) and higher charge separation efficiency (from 3.79 μA/cm² to 3.22 μA/cm²). The enhanced visible light absorption performance and the reduced electron-hole pair recombination rate of xC-g-C₃N₄ can efficiently initiate PDS. The obtained xC-g-C₃N₄ catalyst exhibited superior photocatalytic activation performance of PDS for 4-CP degradation under visible light illumination. The degradation rate of 4-CP reached 88.3 %, with a total organic carbon (TOC) removal rate of approximately 87.9 %, which increased by 67.9 % and 160 %, respectively. This study highlights a new effective method of carbon doping in g-C₃N₄ for activating PDS in the degradation of 4-CP.