Onion skin-derived hierarchical carbon/hollow CoFe2O4 composite with effective microwave absorption in multi-band

The absorption of multi-band electromagnetic waves is still a challenging project in the field of microwave absorption. Herein, onion skin-derived hierarchical carbon/hollow CoFe2O4 composite was successfully prepared through an in-situ growth method. The OC-CFO composite exhibits excellent microwave absorption performance with a minimum reflection loss of −53.54 dB at 2.46 mm and a maximum effective bandwidth of 4.92 GHz at 1.7 mm. It is notable that with varied thicknesses, OC-CFO can achieve strong absorption in multi-band. The excellent performance can be attributed to the synergistic effect of the conduction loss, polarization loss, magnetic loss and impedance matching. This work further facilitates the development of biomass-derived carbon materials with multi-band microwave absorption properties.