Ionic liquid-induced strategy for carbon quantum dots/BiOX (X = Br, Cl) hybrid nanosheets with superior visible light-driven photocatalysis

A novel one-step ionic liquid induced strategy has been reported for the controlled synthesis of carbon quantum dots (CQDs)/BiOX (X = Br, Cl) hybrid nanosheets with tunable CQDs loading contents. Such synthetic process allows the CQDs well dispersed on the surface of BiOX nanosheets. Three different types of pollutants, such as phenol rhodamine B (RhB), antibacterial agent ciprofloxacin (CIP) and endocrine disrupting chemical bisphenol A (BPA) were chosen to evaluate the photocatalytic activity of CQDs/BiOX composite nanosheets. They show very interesting CQDs loading content and X composition-dependent photocatalytic activity with 3 wt% CQDs/BiOBr nanosheets showing the highest photocatalytic activity (much better than pure BiOBr nanosheets) for the degradation of RhB, CIP and BPA under visible light irradiation. The results reveal that there are three factors in promoting the photocatalysis of 3 wt% CQD/BiOBr nanosheets: high visible light absorbance, high separation efficiency of photo-induced electrons and holes and lower resistance. The active species trap experiments and electron spin resonance (ESR) reveal that during the photocatalytic process, hole and O2− become the dominant species for the degradation of pollutants. The unique strategy demonstrated here can be extended to other hybrid nanosheet systems, making it possible to design and tune advanced photocatalysts for other important chemical and catalytic reactions.