Rational Construction of Hierarchically Porous Fe–Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption

Highlights Hierarchically porous Fe–Co/N-doped carbon/rGO (Fe–Co/NC/rGO) composites were successfully prepared. Macropores, mesopores, and micropores coexisted in the composites. Hierarchically porous Fe–Co/NC/rGO showed effective bandwidth of 9.29 GHz. Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge. Here, a novel Fe–Co/N-doped carbon/reduced graphene oxide (Fe–Co/NC/rGO) composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Co-based metal organic frameworks (Co-MOF) on the sheets of porous cocoon-like rGO followed by calcination. The Fe–Co/NC composites are homogeneously distributed on the sheets of porous rGO. The Fe–Co/NC/rGO composite with multiple components (Fe/Co/NC/rGO) causes magnetic loss, dielectric loss, resistance loss, interfacial polarization, and good impedance matching. The hierarchically porous structure of the Fe–Co/NC/rGO enhances the multiple reflections and scattering of microwaves. Compared with the Co/NC and Fe–Co/NC, the hierarchically porous Fe–Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design. Its minimum reflection loss (RL min ) reaches − 43.26 dB at 11.28 GHz with a thickness of 2.5 mm, and the effective absorption frequency (RL ≤ − 10 dB) is up to 9.12 GHz (8.88–18 GHz) with the same thickness of 2.5 mm. Moreover, the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm. This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.