Metal-free CQDs introduced g-C3N4 nanosheets with enhanced photocatalytic reduction performance of uranium (VI)

The use of visible light to convert soluble U(VI) to insoluble U(IV) is a promising strategy for removing radioactive pollution. In this work, we used the top-down strategy to make carbon quantum dots and calcined with melamine to obtain carbon quantum dot modified carbon nitride (CD-C3N4) composite photocatalytic material. The introduction of carbon quantum dots encourages not only the separation of photogenerated electrons and holes, but also the capture of light through up-conversion photoluminescence activity. When the carbon quantum dots doping amount rate of 5% (CD5-C3N4), the energy gap was 2.2 eV, and the highest photocatalytic performance is shown. After irradiation for 120 min, the removal rate of U(VI) in the solution was 97.19%. Five photocatalytic cycle experiments show that the CD5-C3N4 had perfect reusability. Moreover, through the active species trap experiment, the possible mechanism of enhancing photocatalysis was proposed and analyzed. This research has a broad application prospect in the field of radioactive pollution purification, and is of great significance for the design of other CQDs-based photocatalysts in radioactive contamination treatment.