Nitrogen-doping coupled with cerium oxide loading co-modified graphitic carbon nitride for highly enhanced photocatalytic degradation of tetracycline under visible light

The increasingly serious pollution of antibiotics brings an enormous threat to the ecological environment and human health. Graphite phase carbon nitride (g-C3N4), as a popular photocatalytic material, is widely used in photocatalytic degradation of antibiotics in water. In order to make up for the shortage of g-C3N4 monomer, CeO2/N-doped g-C3N4 (CeNCN) composite photocatalysts co-modified with nitrogen doping and CeO2 loading were designed and synthesized with the idea of expanding visible light absorption and promoting photo generated carrier separation. CeNCN exhibits excellent photodegradation performance, the removal rate of tetracycline reached 80.09% within 60 min, which is much higher than that of g-C3N4 (CN) and N-doped g-C3N4 (NCN); and the quasi-first-order degradation rate constant is 0.0291, which is 7.86 and 2.29 times higher than CN and NCN. Electron spin resonance and free radical trapping experiments confirmed that h+, O-center dot(2)- and (OH)-O-center dot are the active substances in the photocatalytic system. After 5 cycles, the degradation efficiency of tetracycline still exceeds 75%, which indicates that CeNCN has good stability. This work proves that N-doping and CeO2 loading can effectively broaden the photoresponse range of g-C3N4, facilitate the separation of photogenerated electron hole pairs, and provide a reference for the construction of g-C3N4-based photocatalyst with high-efficiency photodegradation activity.