Polypyrrole-Coated Composites of Flower-Shaped NiCo₂O₄/Co₃O₄ Nanosheets for Microwave Absorption

A 3D flower-like nickel–cobalt oxide/cobalt oxide @ polypyrrole (NiCo 2 O 4 /Co 3 O 4 @PPy) nanocomposite with a core–shell heterostructure was successfully prepared based on the morphology optimization and multicomponent composite strategy. By changing the ratio of PPy, full absorption of multiple bands can be achieved at different thicknesses of the optimized ternary composite. The RL min of NCO/Co 3 O 4 @PPy-2 can achieve −60.27 d B at a thickness of 2.9 mm, which covers the entire X-band with a filler loading of 10%. The maximum effective absorption bandwidth reached 5.25 GHz. The excellent absorption performance is attributed to the electromagnetic synergy effects and impedance matching between NiCo 2 O 4 /Co 3 O 4 and PPy. Therefore, the construction of a 3D core–shell flower heterostructure is an effective strategy for large-scale preparation of NiCo 2 O 4 -based high-performance absorbers, paving an inspirational route for the study of the electromagnetic wave absorption mechanism of hierarchical composite absorbers.