Fabrication of a ternary BiOCl/CQDs/rGO photocatalyst: The roles of CQDs and rGO in adsorption-photocatalytic removal of ciprofloxacin

In this work, a ternary BiOCl/carbon quantum dots (CQDs)/reduced graphene oxide (rGO) composite photocatalyst with high removal efficiency of ciprofloxacin was fabricated. For BiOCl/CQDs/rGO-10, rGO greatly enhanced the adsorption capacity, while rGO and CQDs significantly improved the photocatalytic performance by enhancing the charge separation and charge injection, which were 3.8 and 8.4 times higher than those of BiOCl, respectively. Interestingly, the photon absorption rate of BiOCl/CQDs/rGO-10 was only 1.3 times higher than that of BiOCl, suggesting that CQDs and rGO could not improve the effective light absorption although they could enhance the light harvesting ability and demonstrating the enhancement in light harvesting ability was not an essential factor for improving photocatalytic activity. In addition, BiOCl/CQDs/rGO-10 displayed high stability and the photocatalytic mechanism of ciprofloxacin was also proposed. This work not only exhibited an excellent reference with outstanding adsorption-photocatalytic performance in application of water remediation, but also provided a new insight into the roles of CQDs and rGO in the adsorption and photocatalysis for CQDs or rGO based composite photocatalysts.