Facile Preparation of Snowflake‐Like MnO 2 @NiCo 2 O 4 Composites for Highly Efficient Electromagnetic Wave Absorption

Snowflake‐like MnO 2 @NiCo 2 O 4 composites were successfully fabricated by employing crossed snowflake‐like MnO 2 nanorods as cores and one‐dimensional (1D) NiCo 2 O 4 nanoneedles as shells. Impressively, the MnO 2 @NiCo 2 O 4 composites exhibited a highly efficient electromagnetic wave (EMW) absorbing capability, and the minimum reflection loss (RL) value reached −58.4 dB at 6.8 GHz for a thickness of 4.0 mm. The reasons for the improved EMW absorption capability of snowflake‐like MnO 2 @NiCo 2 O 4 composites were analyzed. The unique core–shell structure, good impedance matching, and high dielectric loss were all found to be important contributors. Moreover, the interfacial polarization mainly stemmed from the heterostructure, a microcurrent generated from the 1D MnO 2 nanorods and NiCo 2 O 4 nanoneedles under alternating electromagnetic fields, and the synergistic effect from the different components were all beneficial to improve the EMW absorption performance. These results demonstrated that snowflake‐like MnO 2 @NiCo 2 O 4 composites could be utilized as promising materials for practical EMW absorbing applications.