Hierarchically Porous Hemp-Derived Carbon Supported CoFe Alloy Nanoparticles for High-Efficiency Electromagnetic Wave Absorption

Herein, a lightweight and efficient CoFe alloy/biomass carbon composite (CoFe@hemp-C) is synthesized via a scalable grinding-assisted impregnation and one-step pyrolysis process, utilizing agricultural hemp stalk residue as the carbon precursor. This strategy enables the in-situ formation of uniformly dispersed CoFe nanoparticles within a hierarchically porous carbon matrix derived from the natural hemp structure.

Benefiting from the conductive carbon network, abundant heterogeneous interfaces, and multilevel porous architecture, the composite exhibits enhanced conduction loss, interfacial polarization, dipolar polarization, and multiple scattering effects. The incorporation of CoFe alloy nanoparticles further increases the density of heterogeneous interfaces and polarization centers, thereby promoting dielectric attenuation. As a result, the optimized CoFe@hemp-C achieves a minimum reflection loss of −53.5 dB and an effective absorption bandwidth of 4.9 GHz at a thickness of 2.5 mm.