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Page 10 of 13 Wu et al. Soft Sci 2024;4:42 https://dx.doi.org/10.20517/ss.2024.51

Figure 8. EMW absorption mechanism diagram of CoFe/Co@NC heterostructure. EMW: Electromagnetic wave; NC: nitrogen-doped
carbon.

its interior. Due to the multiple reflections and scattering between its large number of nanosheets [51,52] , the
transmission path of EMWs is greatly increased, thereby enhancing EMW attenuation. Many
heterogeneous interfaces are formed between hollow CoFe alloy nanospheres and NC nanosheets, metallic
Co nanospheres and NC nanosheets, nanosheets and cube blocks, which will lead to significant interface
polarization. Furthermore, many NC nanosheets are assembled to form a 3D conductive network, thereby
enhancing the conduction loss in the absorber. Electron migration and jumping between nanospheres and
between nanospheres also contribute to conduction losses. At the same time, the electronegativity of N
heteroatoms is different from that of C atoms, so doping numerous N atoms in the carbon matrix will
induce dipole polarization. Combining these dielectric behaviors, CoFe/Co@NC exhibits outstanding
dielectric loss characteristics. On the other hand, the abundant magnetic nanospheres in the heterostructure
promote the exhibition of exchange resonance characteristics. Many adjacent nanospheres also generate
eddy current losses, which enhance the magnetic loss characteristics. Therefore, CoFe/Co@NC
heterostructure has outstanding EMW absorption performance due to the synergistic effect of interfacial
polarization, multiple reflections, conduction loss, dipole polarization, exchange resonance and eddy
current loss.