Carbon Quantum Dots Induced Ultrasmall BiOI Nanosheets with Assembled Hollow Structures for Broad Spectrum Photocatalytic Activity and Mechanism Insight

Carbon quantum dots (CQDs) induced ultrasmall BiOI nanosheets with assembled hollow microsphere structures were prepared via ionic liquids 1-butyl-3-methylimidazolium iodine ([Bmim]­I)-assisted synthesis method at room temperature condition. The composition, structure, morphology, and photoelectrochemical properties were investigated by multiple techniques. The CQDs/BiOI hollow microspheres structure displayed improved photocatalytic activities than pure BiOI for the degradation of three different kinds of pollutants, such as antibacterial agent tetracycline (TC), endocrine disrupting chemical bisphenol A (BPA), and phenol rhodamine B (RhB) under visible light, light above 580 nm, or light above 700 nm irradiation, which showed the broad spectrum photocatalytic activity. The key role of CQDs for the improvement of photocatalytic activity was explored. The introduction of CQDs could induce the formation of ultrasmall BiOI nanosheets with assembled hollow microsphere structure, strengthen the light absorption within full spectrum, increase the specific surface areas and improve the separation efficiency of the photogenerated electron–hole pairs. Benefiting from the unique structural features, the CQDs/BiOI microspheres exhibited excellent photoactivity. The h⁺ was determined to be the main active specie for the photocatalytic degradation by ESR analysis and free radicals trapping experiments. The CQDs can be further employed to induce other nanosheets be smaller. The design of such architecture with CQDs/BiOI hollow microsphere structure can be extended to other photocatalytic systems.