Controlled Synthesis of HPCFs@FeCoNi@NC from Biomass Fiber with Excellent Electromagnetic Wave Absorption Properties Over a Broad Spectrum EAB and Magnetic Contents

A sustainable, template-free self-assembly synthesis was used to fabricate biomass-based, highly efficient HPCFs@FeCoNi@NC (HPCFs refer to helical/chiral porous carbon fibers at 700 and 800 °C carbonization temperatures, and NC is accredited to N-doped porous carbon structures) as electromagnetic wave absorbers (EMAs). The synthesis of HPCFs@FeCoNi@NC as an EMA circumvents prerequisite tiresome treatments, laborious work, high energy-intensive chemical fabrication, and precursors (e.g., MOF-74) and other organic binders (PVA, PVB, H₄DOT, etc.). The fabricated EMA exhibits top-notch electromagnetic wave (EMW) absorption capabilities with improved reflection loss (RL) across a broad spectrum, achieving efficient absorption bandwidth (EAB, RL ≤ −10 dB), covering 0.90–7.00 GHz over 3.00–18.00 GHz at a 1.00–6.00 mm matching thickness. Noticeably, HPCFs₇₀₀@FeCoNi@NC_2b as an EMA has gained an RL of −86.16 dB over 11.60 GHz, with the EAB covering 9.60–13.80 GHz (4.20 GHz) at a matching thickness of 2.60 mm. Furthermore, HPCFs₈₀₀@FeCoNi@NC_2b achieved an RL of −86.28 dB with an EAB of 2.20 GHz (covering 8.70–10.90 GHz) at a 2.44 mm matching thickness and 9.60 GHz. The EMA’s improved RL over a broad-spectrum EAB is accredited to its unique structural morphology, better dissipation/attenuation mechanisms of EMW, additional loss mechanisms, and so on. Likewise, the EMA’s ability to dissipate/attenuate EMW across low and high frequencies (3.00–18.00 GHz) makes it a novel contender for futuristic applications.