Hierarchical CoFe₂O₄@PPy hollow nanocubes with enhanced microwave absorption

Ferries are appearing as attractive microwave absorption (MW) materials due to outstanding magnetic properties, simple preparation process, structure stabilization and low price, but poor impedance matching and low conductivity have limited their extensive applications. In this work, hierarchically hollow CoFe₂O₄/polypyrrole nanocubes (CoFe₂O₄@PPy HNCs) with enhanced electromagnetic characteristics for MW absorption are fabricated by combining self-sacrificing template and in-situ polymerization route. The CoFe₂O₄@PPy composites were characterized by XRD, FTIR, XPS, SEM, and TEM. The results verify that PPy are coated equably on the surface of CoFe₂O₄ nanocubes to form a unique hierarchically hollow structure. Moreover, the electromagnetic characteristics can be adjusted by regulating PPy proportion. The outcomes demonstrate that the as-prepared CoFe₂O₄@PPy composites has outstanding MW absorbing ability. The desirable microwave absorption is achieved in the composite of CF@PPy-2, where the minimum reflection loss (RL) reaches − 43.85 dB at 9.7 GHz with a thickness of 3.0 mm and broad effective bandwidth (RL ≤ −10 dB) of 5.7 GHz can be achieved at 2.0 mm thickness. This is because the moderate PPy coating endows CoFe₂O₄@PPy composites with improved impedance matching and multiple loss mechanisms. In view of its excellent MW absorbing performance, hierarchical CoFe₂O₄@PPy HNCs is expected to be potential MW absorbers for extensive applications.