Unique nanoporous structure derived from Co3O4–C and Co/CoO–C composites towards the ultra-strong electromagnetic absorption

The development of a strong absorption and low filler loading microwave absorbers that aims to solve the electromagnetic pollution is still a serious challenging. Herein, novel dual-configuration nanoporous Co3O4–C and Co/CoO–C composites were prepared via hydrothermal and high-temperature pyrolysis methods. Results demonstrated that micromorphology and electromagnetic properties of as-synthesized composites could be regulated by tuning the pyrolysis temperature, and the formed porous structure can be explained by kirkendall effect. Furthermore, the reflection loss of Co3O4–C material annealed in air at 400 °C (A-400) and Co/CoO–C material annealed in N2 at 900 °C (N-900) with an ultra-low filler content of 5 wt% can be reached to −51.8 dB at 15.8 GHz and −55.7 dB at 6.3 GHz, respectively. The exceptional microwave absorption performances can be attributed to multiple reflection and scattering, interface polarization effect and good impedance matching. Such achievements indicate that cobalt (oxide)-carbon nanocomposites could be a promising candidate for designing and fabricating lightweight and high-efficient microwave absorbers.