Construction of cotton derived carbon fiber@FeNi nanoparticle/porous carbon sponge for boosting electromagnetic wave absorption

Abstract Carbon‐based sponge materials have attracted massive attention as electromagnetic wave (EMW) absorber candidates due to their lightweight and excellent electromagnetic (EM) attenuation capability. However, the high cost, complex fabrication process and limited EMW absorption bandwidth restrict their application. Herein, a hierarchical three‐dimensional (3D) cotton derived carbon fibers coated with core–shell structure FeNi nanoparticle@porous carbon (CCF/FeNi@PC) from MOF precursor were successfully constructed by coprecipitation and one‐step pyrolysis methods. By regulating carbonization temperature, optimizing the electromagnetic parameters, outstanding electromagnetic absorption (EMA) performance was achieved. The CCF@FeNi/PC synthesized at 900 °C demonstrates a −64.5 dB minimum reflection loss (RL min ) at 15.39 GHz, and the effective absorption bandwidth (EAB) is 5.08 GHz when the thickness is only 1.9 mm. Notably, the maximum EAB (EAB max ) was extended 8.18 GHz at 2.96 mm for FeNi‐800. The excellent microwave absorption performance is attributed to the synergistic effect of enhanced dielectric loss and magnetic loss, good impedance matching as well as hierarchical multiple scattering and reflection of EMWs. The obtained CCF@FeNi/PC composites provide a novel and promising strategy for constructing lightweight low‐cost efficient microwave absorption materials.