Construction of Co/Biomass-Derived Carbon Composites for Enhanced Microwave Absorption Performance

The key to strong microwave absorption is not merely the presence of multiple loss mechanisms but rather their synergistic optimization alongside precise impedance matching. Here, we report a novel binary composite based on activated carbon derived from a longan shell (ACL) decorated with Co nanoparticles, forming a three-dimensional, interconnected porous carbon structure. By integrating the conductive carbon framework with magnetic Co nanoparticles, this design generates abundant interfacial polarization sites, improved charge separation, as well as enhanced dielectric-magnetic coupling. The three-dimensional structure not only prolongs the transmission path of incident waves through multiple reflections and scattering but also optimizes impedance matching, thereby enhancing overall microwave absorption. Benefiting from this synergistic structure, the ACL@Co (activated carbon derived from a longan shell with Co particles) composites exhibit excellent microwave absorption, with a minimum reflection loss of −40.64 dB at 13.50 GHz, a wide effective bandwidth of 6.3 GHz, and a remarkably thin absorber thickness of only 1.8 mm. This work demonstrates the cost-effective utilization of biomass-derived carbon for the fabrication of high-performance magneto-dielectric heterojunction microwave absorbers.