Chitin-derived-carbon nanofibrous aerogel with anisotropic porous channels and defective carbon structures for strong microwave absorption

With the increasing use of microwaves, the functional design of carbon-based microwave absorbers has gained attention toward overcoming severe electromagnetic pollution, owing to the lightweight and broadband ab-sorption properties of these absorbers. The key functions for realizing strong microwave absorption include good impedance matching to the impedance of free air, moderate conductive loss, and high polarization loss. How-ever, it remains challenging to incorporate these complex functions into a single microwave absorber. Herein, the tailoring of anisotropic porous channels and defective carbon structures within chitin-derived carbon nano -fibrous aerogels is proposed to overcome this challenge. Honeycomb-like anisotropic porous channels were fabricated by the unidirectional freeze drying of crab-shell-derived chitin nanofiber/water suspensions. There-after, temperature-controlled carbonization was performed to tailor the defective carbon structures. Anisotropic porous channels and the as-tailored N-and O-doped defective carbon provide good impedance matching and high polarization loss, respectively. Both strategies moderate the conductive loss. The resulting aerogel had strong microwave absorption of-82.2 dB at 8.9 GHz and-92.8 dB at 11.6 GHz when the incident microwave radiation was parallel and perpendicular to the anisotropic channels, respectively. This performance surpasses that of state-of-the-art carbon-based microwave absorbers. These findings could guide the fabrication of high-performance and sustainable microwave absorbers.