One-Pot Cation Exchange−Polymerization Enables FeCoNi-Rich Hollow Magnetic Nanotubes for Boosted Low-Frequency Electromagnetic Wave Absorption

Abstract The rational engineering of magnetic-dielectric absorbers embedded with abundant FeCoNi alloy nanoparticles holds great promise for low-frequency electromagnetic wave (EMW) absorption. However, developing a synthetic approach that simultaneously achieves well-dispersed nanoparticles and a hollow architecture while enabling facile processing remains challenging and merits in-depth exploration. Herein, a one-pot cation-exchange-polymerization engineering strategy is developed to prepare hollow magnetic-dielectric absorbers. During high-temperature pyrolysis, the in situ formation of FeCoNi alloy nanoparticles and the generation of polydopamine-derived N-doped carbon protrusions occur simultaneously, generating numerous alloy-carbon heterointerfaces and polar functional groups that enhance magnetic-dielectric synergy. The optimized sample exhibits a minimum reflection loss (RLmin) of −67.4 dB at 5.2 GHz and an effective absorption bandwidth (EAB) of 1.89 GHz, highlighting its effective low-frequency EMW absorption performance. Overall, this work provides a promising strategy for the fabrication of low-frequency EMW absorbers.