Hollow Porous Bowl-like Nitrogen-Doped Cobalt/Carbon Nanocomposites with Enhanced Electromagnetic Wave Absorption

A unique hollow porous bowl-like nitrogen-doped cobalt/carbon nanocomposite (HBN-Co/C) composed of Co nanoparticles anchored in N-doped porous carbon was designed for enhancing electromagnetic microwave absorption (EMA). The inner cavities of the HBN-Co/C could be regulated to match the impedance and permittivity between the absorber and air, leading to a precise adjustment of the EMA performance. More importantly, the existence of inner cavities decreases the extra multi-interface promoted interfacial polarization and overall density. The synergetic effects of the multicomponents, multiple reflections, and scatterings promoted strong interfacial polarization and facilitated impedance matching. As a result, the HBN-Co/C nanocomposites displayed excellent EMA performance, for which the minimum reflection loss was −42.3 dB at 13.3 GHz with a thickness of only 1.9 mm. The effective absorption bandwidth below −10 dB was up to 5.1 GHz (12.9–18.0 GHz) when the thickness was 1.7 mm. This work provides a facile design and synthesis strategy of novel lightweight electromagnetic wave absorbers with broadband and strong absorption.