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

Abstract

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 and O^˙−₂ by the ESR technique and analyzed by calculations as well as XPS valence spectra, and a possible photocatalytic mechanism was also proposed.