Rational design of hierarchical yolk-double shell Fe@NCNs/MnO₂ via thermal-induced phase separation toward wideband microwave absorption

Rational design of yolk-shell architectures with synergistic effect are vital for improving microwave attenuation ability, but still face challenges. In this work, we employ the thermal-induced phase separation engineering and redox strategy to fabricate hierarchical yolk-double shell Fe@NCNs/MnO₂, in which magnetic Fe units are individually confined in N-doped carbon nanocubes (NCNs) cavity and hierarchical MnO₂ nanosheets are intimately anchored on NCNs surface. It is found that the phase separation process between Prussian blue and poly-dopamine is significantly determined by the thermal-induced inward contraction owing to their different thermal stabilities and independent crystal structures. As results, the hierarchical composites exhibit matched impedance and wideband microwave absorption owing to the internal cavity architectures, multiple hetero-interfaces, dielectric-magnetic synergistic effect and hierarchical conformations. The minimum reflection loss reaches −46.7 dB with 3.3 mm thickness, and more importantly, the effective bandwidth (<-10 dB) achieves as strong as 10.8 GHz at 3.1 mm. This work opens up a novel and meaningful thinking for the construction of yolk-double shell architectures and the synthesized hierarchical composites can be used as promising candidates in addressing electromagnetic pollution.