Construction of three-dimensional hierarchical porous nitrogen-doped reduced graphene oxide/hollow cobalt ferrite composite aerogels toward highly efficient electromagnetic wave absorption

The development of graphene-based composites with low density, robust absorption, wide bandwidth and thin thickness remained a great challenge in the field of electromagnetic (EM) absorption. In this work, nitrogen-doped reduced graphene oxide/hollow cobalt ferrite (NRGO/hollow CoFe2O4) composite aerogels were constructed by a solvothermal and hydrothermal two-step route. Results demonstrated that the as-fabricated composite aerogels had the ultralow density and a unique three-dimensional (3D) network structure, and lots of hollow CoFe2O4 microspheres were almost homogeneously distributed on the wrinkled surfaces of lamellar NRGO. Moreover, superior EM absorbing capacity could be achieved by modulating the ferrite structure, addition amounts of hollow CoFe2O4 and thicknesses. It was noteworthy that the NRGO/hollow CoFe2O4 composite aerogel with the addition amount of ferrite of 15.0 mg possessed the minimum reflection loss of -44.7 dB and maximum absorption bandwidth of 5.2 GHz (from 12.6 to 17.8 GHz) at a very thin thickness of 1.8 mm and filling ratio of 15.0 wt.%. Furthermore, the possible EM attenuation mechanism had been proposed. The results of this work would be helpful for developing RGO-based 3D composites as lightweight, thin and highly efficient EM wave absorbers.