The synergistic role of carbon quantum dots for the improved photocatalytic performance of Bi2MoO6

Novel carbon quantum dot (CQD) modified Bi2MoO6 photocatalysts were prepared via a facile hydrothermal process. The CQD modified Bi2MoO6 materials were characterized by multiple techniques. The CQDs with the average size of about 7 nm were distributed on the surface of Bi2MoO6 nanosheets. The photocatalytic activity of as-prepared CQD modified Bi2MoO6 materials was investigated sufficiently by the photodegradation of four different kinds of pollutants, such as ciprofloxacin (CIP), bisphenol A (BPA), tetracycline hydrochloride (TC), and methylene blue (MB). The improved photocatalytic activity was observed for CQD modified Bi2MoO6 samples compared with pure Bi2MoO6 under visible light irradiation. The CQD modified Bi2MoO6 photocatalysts with a CQD content of 2 wt% exhibited the optimum photocatalytic activity, which was found to increase by about 5 times than that of the pure Bi2MoO6 for the photodegradation of CIP. This improvement was attributed to the crucial role of CQDs, which acted as a photocenter for absorbing solar light, a charge separation center for suppressing charge recombination, and a catalytic center for pollutant photo-degradation. The main active species were determined to be (OH)-O-center dot and O-2(center dot-) by the ESR technique and analyzed by calculations as well as XPS valence spectra, and a possible photocatalytic mechanism was also proposed.