Construction of hierarchical carbon fiber Aerogel@Hollow Co₉S₈ polyhedron for high-performance electromagnetic wave absorption at low-frequency

The development of low-frequency electromagnetic wave absorption materials faces considerable obstacles due to intense coupling of wave impedance and electromagnetic dissipation capacity. Herein, a novel hierarchical structure composed of 3D interconnected carbon fibers aerogel loaded with hollow cobalt (Co)-sulfide polyhedrons (CFA@HCS) is designed. Typical 3D interconnected carbon fibers derived from bamboo cellulose fiber aerogel serve as a skeleton to support the Co₉S₈ with a hollow structure. The electromagnetic parameters of the composite are effectively modified by combining the carbon-based skeleton with the hollow Co₉S₈. The coupling interaction of the electromagnetic characteristics at low frequency can be significantly improved. Accordingly, the minimum reflection loss (RL_min) of CFA@HCS with 15 wt% filler loading reaches −53.6 dB at 3.36 GHz and its effective absorption bandwidth can cover almost all the S and C bands (3.04–8 GHz). In addition, the minimum reduction of the radar cross section (RCS) reaches –22.6 dB m² when the incidence theta is −60°. This work demonstrates that low-frequency EMW absorption could be improved by constructing hierarchical composites of carbon fiber/transition metal sulfide.