Influence of N-, S-, and B-doped carbon quantum dots modification on the photocatalytic degradation performance of ZnO

N-, S-, and B-doped carbon quantum dots (CQDs) were synthesised via a hydrothermal method, with N and S derived from cysteine, and B derived from boric acid. Then the CQDs were combined with ZnO to obtain a new type of surface-functionalised photocatalytic degradation materials. The photocatalytic degradation performance of these composites against various common organic pollutants and sulphonamide antibiotics was systematically studied. Results showed that CQDs modification enhanced photocatalytic efficiency and degradation rate. Doping with individual elements further improved performance, while co-doping with N, S, and B achieved the highest degradation rate. The degradation rate of rhodamine B reached 97.56 %. More importantly, the pH level had a remarkable influence on the photocatalytic activity of the composites with acidic conditions favouring the photocatalytic reaction. Free-radical trapping experiments indicate that ·O 2 – and ·OH played dominant roles in the photocatalytic process. In addition, the composites maintained good photocatalytic degradation performance after multiple cycles, demonstrating excellent stability.