N-CQDs modified BiOBr with different nitrogen configurations synthesized from different precursors for efficient photocatalytic degradation of carbamazepine

In the realm of persistent pharmaceutical contaminants photodegradation, N-doped carbon quantum dots (NCQDs) modified bismuth-based photocatalysts have recently received a lot of interest. However, an in-depth understanding of the effect of both N chemical state and N chemical configuration on the photocatalytic activity was still lacking. Herein, three graphite/pyrrole N-doped CQDs with different contents were prepared by hydrothermal method to modify BiOBr (BNCs), respectively. The degradation kinetics of carbamazepine (CBZ) by BNC-eda (doped with 100 % pyrrole N, k = 0.363 min -1) was higher than that of BNC-trp (doped with 62 % pyrrole N and 38 % graphitic N, k = 0.099 min -1) and BNC-ur (doped with 58 % pyrrole N and 42 % graphitic N, k = 0.072 min -1) under visible-light irradiation. More importantly, the k of BNCs degrading CBZ showed a linear positive relationship with the percentage content of pyrrole-N in the corresponding N-CQDs with r2 = 0.9999. The characterization results showed that doping with pyrrole N rather than graphite N could be responsible for the increase in visible light absorption, the promotion of electron-hole separation and the generation of more superoxide radicals (center dot O2-) and singlet oxygen (1O2) in BNCs. Toxicity Estimation Software Tool program showed that the BNC-eda exhibited CBZ toxicity reduction performance. Overall, this study offered a useful method for designing excellent N-CQDs modified Bi-based photocatalysts for the treatment of pharmaceutical wastewater.