Space confinement engineering and temperature optimization strategy to design yolk-shell FeCo@Air@C towards ultrabroad electromagnetic wave absorption

Metal organic frameworks are broadly used as promising precursors or templates for the fabrication of carbon-based derivatives owing to their exceptional porosities, structural diversities, and large specific surface areas. In this study, a facile method was reported to construct yolk-shell FeCo@air@C nanocomposites via annealing FeCo-prussian blue analogues (PBA)@phenolic resin (PR) precursor at different temperatures under Ar atmosphere. The introduction of PR effectively reinforced the stability of FeCo-PBA microstructure during carbonization process and played a confining role in preventing the serious agglomeration of FeCo nanoparticles. By adjusting the pyrolysis temperature, different categories of yolk-shell FeCo@air@C nanocomposites had been selectively established. Amongst, the FeCo@air@C obtained at 600 °C exhibited the superior electromagnetic wave absorption performances with a minimum reflection loss of -68.3 dB at the thickness of 2.44 mm and an ultrabroad effective absorption bandwidth of 8.2 GHz at 3.20 mm. Interestingly, its corresponding radar cross section value exhibited excellent radar stealth property in the practical applications. Therefore, the results elucidate that the combination of space confinement engineering and temperature optimization strategy is an indeed advanced method to regulate the electromagnetic wave absorption performances of magnetic carbon-based materials derived from FeCo-PBA.