Ionic liquid-induced double regulation of carbon quantum dots modified bismuth oxychloride/bismuth oxybromide nanosheets with enhanced visible-light photocatalytic activity

The efficient separation of photoexcited electron-hole pairs acts as a significant factor and challenge for the enhanced photocatalytic activity of the photocatalyst. To pursue higher photocatalytic activity, carbon quantum dots (CQDs) modified bismuth oxychloride (BiOCl)/bismuth oxybromide (BiOBr) nanosheet photocatalyst has first been synthesized via an in situ ionic liquid-induced strategy. The bridge function of the ionic liquid ensures the uniform dispersal of CQDs on the surface of the BiOCl/BiOBr material. After the introduction of CQDs, the CQDs/BiOCl/BiOBr composite photocatalyst displayed enhanced photocatalytic activity for the photodegradation of several different types of organic contaminants such as rhodamine B, tetracycline hydrochloride, ciprofloxacin, and bisphenol A under the irradiation of visible light, and the BiOCl/BiOBr material loading with 5 wt% CQDs showed the best photocatalytic performance. The characterization results revealed that the introduction of CQDs could simultaneously improve the visible light absorption properties and separation efficiency of photoexcited electron-hole pairs. The electron spin resonance and radical quenching experiments demonstrated that during the photocatalytic reactions, holes and superoxide radicals were the main active species involved in the degradation of the contaminants, and the possible photocatalytic mechanism is presented. Therefore, this work provides an efficient pathway for the improved activity of the photocatalyst.