Hollow engineering of HCNs@CoFe₂Se₄-QDs with quantum dots toward ultra-broadband electromagnetic wave absorption

Hollow engineering is considered to be an essential subfield in promoting electromagnetic (EM) wave absorption intensity and realizing the lightweight characteristics. However, the enhancement of effective absorption bandwidth (EAB) still faces huge challenges. Herein,HCNs@CoFe₂Se₄-QDs with superior EM wave absorption intensity and ultra-broadband EAB are produced by using tightly arranged SiO₂ spheres as the hard-templates. Specifically, the removal of SiO₂ templates inevitably results in the formation of hollow cavity, which is favorable to optimize the impedance matching and increase the absorption intensity. Besides, the incorporation of selenium powder effectively increases the numbers of heterogeneous interfaces by forming CoFe₂Se₄ quantum dots (QDs) during the pyrolysis process, leading to strengthened interfacial polarization and ultra-broadband EAB. As results, the superior EM wave attenuation with a minimum reflection loss of -67.6 dB and an EAB of 11.4 GHz is achieved with only 20 wt% filler ratio. This design concept of hollow engineering with magnetic QDs provides us an inspiration in optimizing EM wave absorption intensity and simultaneously promoting absorption bandwidth.