Dual regulation of composition and bio-inspired structure in Co9S8/porous carbon nanofibers for broadband microwave absorption

To address the escalating challenge of electromagnetic pollution, a dual regulation strategy integrating compositional optimization with bio-inspired structural engineering is proposed to fabricate Co9S8-doped porous carbon nanofiber (Co9S8/PCNF) composites via electro-blowing spinning, carbonization, and sulfidation. The resulting composites exhibit a bio-inspired hierarchical architecture, comprising internal honeycomb-like porous skeleton that forms a three-dimensional (3D) conductive network to boost conductive loss, and surface fluffy carbon nanotubes that establishes a gradient-impedance transition to suppress surface reflection. Meanwhile, this integrated honeycomb-fluffy configuration further promotes multiple scattering and excites multi-scale cavity resonance, synergistically enhancing electromagnetic energy dissipation. The introduced Co9S8 nanoparticles not only introduce weak magnetic loss through natural and exchange resonance to optimize impedance matching and achieve dielectric-magnetic synergy, but also catalyze the in-situ growth of fluffy carbon nanotubes on the fiber surface. Furthermore, N, S, O heteroatoms doping induces lattice distortion and disordered defects, generating local dipoles and causing dipole polarization loss. As a result, the optimized Co9S8/PCNF-2 achieves a broadband effective absorption bandwidth (EAB) of 4.2 GHz (7.2-11.4 GHz) at a thin thickness of 3.0 mm, with a minimum reflection loss (RLmin) of -32.6 dB. This study highlights the effectiveness of synergistically regulating composition and bio-inspired structure for developing advanced, lightweight, and broadband absorbers.