Biomass-derived 3D magnetic porous carbon fibers with a helical/chiral structure toward superior microwave absorption

Herein, a catalytic self-deposition (CSD) strategy is proposed to build 3D magnetic porous carbon fibers with a complex helical/chiral structure (MHPFs) toward ultralight and low-frequency microwave absorption unprecedentedly. Different from energy-intensive chemical vapor deposition (CVD) method, the binary composition of cobalt-encapsulated carbon nanotube arrays (CNTAs) and hierarchical pore structure are manipulated by adjusting the CSD technology without exogenous carbon and reducing atmosphere. Micro-/nano-scale structures, 0D/1D integration effects, dielectric/magnetic loss mechanisms, and extraordinary 3D helical/chiral configuration endow MHPFs with remarkable microwave absorption properties. The minimum reflection loss (RL_min) of MHPFs-900 (900 stands for the carbonization temperature) at a low frequency (6.3 GHz) reaches astronomical −61.08 dB. The effective absorption bandwidth (EAB, RL < −10 dB) ranges from 5.4 GHz to 7.5 GHz at a loading of 5%. Notably, at a matching thickness of 2.00 mm, the ultrawide EAB covers 6.2 GHz (11.6–17.8 GHz), while the RL_min exceeds −30.06 dB. Moreover, even with an ultralow filler loading of 2.5%, the absorber still exhibits satisfactory RL_min and broad EAB of −45.04 dB and 4.5 GHz (8.2–12.7 GHz). The results might shed light on the economical and high-producing preparation of advanced microwave absorption materials.