Cocklebur-inspired 3D Co/CoO/RGO/CNT crosslinked heterostructures for highly efficient electromagnetic wave absorption

Electromagnetic functional materials are playing an increasingly vital role in electromagnetic interference shielding, stealth protection, and information security. Carbon nanotubes (CNTs), owing to their unique structure and outstanding electromagnetic properties, have attracted widespread attention. Here, a 3D Co/CoO/RGO/CNT crosslinked heterostructure was fabricated by in-situ growth of CNTs on Co(CO₃)₀·₅(OH)·0.11H₂O precursors that were crosslinked with reduced graphene oxide through a combined hydrothermal and chemical vapor deposition strategy. The resulting interconnected conductive heterostructures significantly enhanced electron transport, interfacial polarization, and impedance matching. Notably, the optimized composites achieved a minimum reflection loss of −23.95 dB with an effective absorption bandwidth of 4.2 GHz (at 10 wt% filler loading and 2.17 mm thickness), fully covering the X-band. Furthermore, the study of heterointerfaces between different components and their underlying loss mechanisms provides critical insights into the electromagnetic wave absorption behavior and guides the rational design of advanced structural materials. Density functional theory simulations were also employed to investigate the electronic structure and charge distribution at the Co–CoO and Co–CNT interfaces. The simulation results reveal that charge redistribution and the formation of interface dipoles contribute to enhanced dielectric and magnetic losses, offering a microscopic explanation for the superior microwave absorption performance.