Tunable Impedance of Cobalt Loaded Carbon for Wide‐Range Electromagnetic Wave Absorption

Abstract Impedance matching modulation of the electromagnetic wave (EMW) absorbers toward broad effective absorption bandwidth (EAB) is the ultimate aim in EMW attenuation applications. Here, a Joule heating strategy is reported for preparation of the Co‐loaded carbon (Co/C) absorber with tunable impedance characteristics. Typically, the size of the Co can be regulated to range from single‐atoms to clusters, and to nanocrystals. The varied sizes of the Co combined with different graphitization degrees of carbon can result in different relative input impedances and electromagnetic loss, leading to the tunable EMW absorption properties of the Co/C absorber. By meticulously coalescing the different prepared Co/C, the working frequency can be easily tuned, covering K u , X, and C bands. Furthermore, the Co/C demonstrates a high EMW attenuation due to its unique dielectric loss capability and magnetic loss characteristics. The abundant interfaces of Co/C can also contribute to the enhanced interfacial polarization for improving EMW attenuation. This work demonstrates the importance of optimizing the metal and carbon interaction to the impedance matching toward wide EAB of the EMW absorbers.