Preparation of high-absorption electromagnetic wave absorption materials by loading hollow Fe3O4 onto porous carbon derived from corncobs

In this study, a green and eco-friendly hollow Fe₃O₄/corncob porous carbon composite was successfully produced by recycling corncob, an agricultural byproduct. It was a low-density, high-absorption, and thin electromagnetic wave (EMW) absorbing material. Overall, corncob porous carbon (CPC) with a porous structure was prepared using the one-step activated charring method. Hollow Fe₃O₄ was grown in-situ on the surface of the CPC, resulting in the formation of hollow Fe₃O₄/CPC composites. The lightweight, porous structure of CPC and the hollow structure of Fe₃O₄ were combined to form a low-density hollow Fe₃O₄/CPC composite material. This composite exhibited excellent EMW absorption performance, with a minimum reflection loss of −43.17 dB and an effective absorption bandwidth of 3.3 GHz at a relatively thin thickness of 1.5 mm. Based on these findings, a plausible EMW absorption mechanism was proposed that the interface polarization, magnetic losses, and dielectric losses due to the synergistic interaction between hollow Fe₃O₄ and CPC. This work provides a new direction for the development of low-cost, eco-friendly, and high-performance biomass-based EMW absorbing materials.