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.

开发具有低密度、强吸收、宽带宽和薄厚度的石墨烯基复合材料仍然是电磁（EM）吸收领域的一大挑战。在这项工作中，通过溶剂热和水热两步法构建了氮掺杂还原氧化石墨烯/空心钴铁氧体（NRGO/空心CoFe ₂ O _{4 ）复合气凝胶。}结果表明，制备的复合气凝胶具有超低密度和独特的三维（3D）网络结构，以及大量的空心CoFe ₂ O _{4 。}微球几乎均匀地分布在层状NRGO的褶皱表面上。此外，通过调节铁氧体结构、空心CoFe ₂ O ₄的添加量和厚度，可以获得优异的EM吸收能力。值得注意的是，NRGO/空心 CoFe ₂ O ₄添加量为 15.0 mg 铁氧体的复合气凝胶在 1.8 mm 的极薄厚度和 15.0 wt.% 的填充率下具有 -44.7 dB 的最小反射损耗和 5.2 GHz（从 12.6 到 17.8 GHz）的最大吸收带宽. 此外，还提出了可能的 EM 衰减机制。这项工作的结果将有助于开发基于 RGO 的 3D 复合材料作为轻质、薄且高效的电磁波吸收器。