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.