Magnetic Pinning and Multi-scale Polarization Enhance Microwave Absorption of Vacancy-Rich CoFe₂O₄/Lignin-Derived Carbon Nanofiber Composites

The development of cost-effective and high-performance carbon-based electromagnetic wave (EMW) absorbent has attracted much attention, while achieving complete impedance matching of the material with tunable magnetic and dielectric properties remains a challenge. In this study, vacancy-rich CoFe₂O₄/lignin-derived N-doped carbon nanofiber composites (CFO@LCF) are obtained as a novel EMW absorption material, in which the synergy of magnetic pinning and multi-scale polarization is achieved by cascade effects originated from the size modulation of encapsulated magnetic CoFe₂O₄ particles, and the defects in both CoFe₂O₄ and lignin-derived carbon to enhance the EMW dissipation. In addition, the conduction loss is promoted at the same time by the three-dimensional (3D) interconnected conductive carbon nanofiber network, and meanwhile, the magnetic loss facilitated by strong magnetic coupling and pinning effect occurs at the particles. Specifically, the optimal CFO@LCF sample shows superior EMW absorption performance with a minimum reflection loss of − 49.25 dB at the matching thickness of 2.08 mm, and an effective absorption bandwidth of 6.54 GHz covering the whole Ku band. The superior performance confirms its application potential, and also suggests an innovative biomass valorization pathway for the development of next-generation carbon-based EMW absorbent.