Carbon-CoFe2O4 composite with hierarchical porous structure for efficient microwave absorption

Biomass-derived carbon materials have drawn great attention in various fields with low cost and good sustainability. In this paper, carbon-CoFe 2 O 4 (C/CoFe 2 O 4 ) composites with natural hierarchical and gradient porous structure are prepared by hydrothermal and carbonization methods from corn stalks. The effect of the CoFe 2 O 4 precursor content on the microwave absorption (MA) performance is studied and the sample with CoFe 2 O 4 at concentrations of 20 mmol/L exhibits the best MA performance. The minimum reflection loss of the composites can reach a value of −56.78 dB at a thickness of 2.50 mm, and the effective absorption bandwidth of the composites can be up to 8.00 GHz at the thickness of 2.25 mm. The MA mechanism of the composite is mainly attributed to the good impedance matching and multiple attenuation characteristics. This work presents an efficient MA material and simultaneously facilitates the productive utilization of agricultural waste corn stalks.