Implanting N-doped CQDs into rGO aerogels with diversified applications in microwave absorption and wastewater treatment

In this work, water-soluble nitrogen-doped carbon quantum dots (N-CQDs) were synthesized by a one-step hydrothermal method, and then implanted into graphene aerogels to obtain N-CQDs/rGO composites. Herein, N-CQDs, as connection sites and channels in rGO, can effectively promote electron jumping and migration and greatly enhance the conduction loss of rGO. As expected, the composites exhibit excellent microwave absorption performance with ultra-wide effective absorption bandwidth of 7.36 GHz and ultra-high minimum reflection loss (RLmin) of −69.42 dB at an ultra-low filler loading of 5 wt%. An ultra-low bulk density of the N-CQDs/rGO composite reach as 4.24 mg/cm3. Actually, the outstanding performance of microwave absorption is attributed to the specific surface morphology and porous structure, enhanced conduction loss and good impedance matching. Meanwhile, the as-synthesized composites display the typical selective adsorption ability for dyes in the wastewater, where the maximum adsorption capacity for methylene blue (MB) dyes is 261 mg/g. Briefly, the study provides a new approach on the comprehensive environmental application of CQDs/graphene composites with both high-performance microwave absorption and high-efficiency removal of organic dyes in the wastewater.