F/N dual doping and defect engineering to optimize impedance matching of carbon nanofibers for boosting...

To tackle the increasingly severe issue of electromagnetic (EM) pollution, the development of high-efficiency microwave absorbing materials (MAMs) with excellent impedance matching and outstanding attenuation capacity is essential. Elemental doping and defect engineering are widely recognized strategies for tuning impedance matching in the design of ideal MAMs. However, achieving facile and efficient element doping in carbon absorbers still remains a major challenge. Herein, a novel F-doped flexible carbon nanofiber (FCNF) was fabricated as an ideal absorber via heteroatom doping and defect engineering to regulate the interfacial microstructure to modulate the defect and charge configuration, thus facilitating impedance matching between the nanofibers and free space, enhancing charge movement, and generating abundant active sites for dipole polarization. Crucially, room-temperature plasma etching endows the flexible carbon nanofibrous membrane with rich conductive pathways, abundant heterointerfaces, and optimized electronic configurations, concurrently realizing lightweight integration and extended absorption bandwidth. Consequently, FCNFs successfully drive the polarization-dominated multiple loss mechanisms, realizing a minimum reflection loss (RL_min) of -49.0 dB at a small thickness of 1.6 mm with a corresponding effective absorption bandwidth (EAB, RL < -10.0 dB) of 3.8 GHz (14.2-18.0 GHz). FCNFs also display a fascinating EAB of 5.9 GHz (12.1-18.0 GHz) at 1.8 mm, basically covering the Ku band. This work introduces a combined strategy of defect engineering and surface modification tailored for carbon nanofibrous microwave absorbers, which enables the multi-step attenuation mechanisms to be precisely regulated.