Water hyacinth powder-assisted in-situ fabrication of visible light responsive CQDs/BiOCl heterojunctions with exceptional photocatalytic detoxification performance

As a typical Bi-based photocatalyst, BiOCl has been received increasing attention because of its many advantages. However, poor visible light response ability and high recombination rate of photoexcited charge pairs significantly inhibit the intense application of BiOCl, therefore, it is considerable to develop a strategy to overcome the inherent shortcomings of BiOCl to boost its photocatalytic properties. The former works have strongly affirmed that coupling carbon quantum dots (CQDs) with BiOCl to construct heterojunctions is a practical method to boost the photoactivity of BiOCl. In this demonstration, water hyacinth powder was used to provide raw material for CQDs, and CQDs/OVs-BiOCl heterostructures were in-situ fabricated through a solvothermal synthesis. The successful modification of CQDs on BiOCl and the formation of abundant oxygen vacancies (OVs) were confirmed by several analytical methods. The test results of photoelectric property reveal that CQDs/OVs-BiOCl has faster photogenerated charge separation rate than the reference BiOCl. Photoactivity of all the samples was examined by destruction of rhodamine B (RhB) and defluorination of perfluorooctanoic acid (PFOA). The CQDs/OVs-BiOCl heterostructures exhibit the ascendant photocatalytic destruction activity. Among them, the degradation efficiency of RhB over 1%CQDs/OVs-BiOCl under visible light irradiation is 2.6 folds of that of over the reference BiOCl. Besides, the defluorination rate of PFOA on 1%CQDs/OVs-BiOCl under UV light irradiation is 1.4 times of that of on BiOCl. The cyclic experimental results solidly prove that the CQDs/OVs-BiOCl samples have outstanding stability and good application prospect. Free radical detection experiments reveal that 1%CQDs/OVs-BiOCl reaction system produces more active species than the reference BiOCl system, and ·O2- is the most important active substance. Additionally, the total organic carbon (TOC) test strongly demonstrate that RhB can be effectively mineralized into inorganic small substances on 1%CQDs/OVs-BiOCl under light shine. Based on the results of all the characterizations, a photocatalytic improvement mechanism for CQDs/OVs-BiOCl was reasonably elaborated. This work provides a new approach to obtain CQDs to modify BiOCl, which not only improves the photocatalytic degradation activity of BiOCl, but also achieves the purpose of use waste to treat waste.