Enhanced Photocatalytic Activity toward Organic Pollutants Degradation and Mechanism Insight of Novel CQDs/Bi₂O₂CO₃...

Novel carbon quantum dots (CQDs) modified with Bi₂O₂CO₃ (CQDs/Bi₂O₂CO₃) were prepared using a simple dynamic-adsorption precipitation method. X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were used to test the material composition, structure, and band structures of the as-prepared samples. Methylene blue (MB) and colorless phenol, as target organic pollutants, were used to evaluate the photocatalytic performance of the CQDs/Bi₂O₂CO₃ hybrid materials under visible light irradiation. Experimental investigation shows that 2⁻5 nm CQDs were uniformly decorated on the surface of Bi₂O₂CO₃; CQDs/Bi₂O₂CO₃ possess an efficient photocatalytic performance, and the organic matter removal rate of methylene blue and phenol can reach up to 94.45% and 61.46% respectively, within 2 h. In addition, the degradation analysis of phenol by high performance liquid chromatography (HPLC) proved that there are no other impurities in the degradation process. Photoelectrochemical testing proved that the introduction of CQDs (electron acceptor) effectively suppresses the recombination of e^--h⁺, and promotes charge transfer. Quenching experiments and electron spin resonance (ESR) suggested that ·OH, h⁺, and ·O₂^- were involved in the photocatalytic degradation process. These results suggested that the up-conversion function of CQDs could improve the electron transfer and light absorption ability of photocatalysts and ·O₂^- formation. Furthermore, the up-conversion function of CQDs would help maintain photocatalytic stability. Finally, the photocatalytic degradation mechanism was proposed according to the above experimental result.