CoFe2O4/porous carbon nanosheet composites for broadband microwave absorption

It is highly desirable yet challenging to develop high-performance microwave absorption materials with lightweight, thin thickness, and strong absorption capability over broad frequency ranges by simple and cost-effective methods. Herein, we design an ultralight (~54 mg cm−3) magnetic-carbon hybrid material to achieve superior microwave absorption performances. By instantaneous freezing-induced self-assembly of Fe3+, Co2+-glucose complexes on a cheap and water-removable template (i.e., NaCl), the as-made composite features 3D hierarchical porous structure and nanosheet-like carbon pore walls embedded with nanocrystalline CoFe2O4. The chemical composition can be controlled by simply altering the ratio of Co2+ (Fe3+) and glucose. Benefitting from the structural and compositional advantages, the optimized composite absorber exhibits a minimum reflection loss value of − 52.29 dB at a thin thickness of 2.0 mm and an effective absorption bandwidth reaching 5.36 GHz (12.64–18 GHz) at a low filler loading of 20 wt%. The microwave absorption mechanism survey reveals that the weak surface reflection and strong dissipation capacity induced by nanosheet-like pore walls combined with the multiple internal reflections caused by 3D hierarchical porous structure contribute to robust impedance matching and strong microwave attenuation ability. This work may offer new insights for designing highly effective magnetic-carbon microwave absorbers with low density and wide absorbing frequency.