Ultrathin high-performance electromagnetic wave absorbers with facilely fabricated hierarchical porous Co/C crabapples

Extremely strong electromagnetic wave (EMW) absorption with a minimum reflection loss (RL) of -56.9 dB at 9.3 GHz at an absorber thickness of only 1.92 mm was observed for the hierarchical porous cobalt (Co)/carbon (C) crabapples, lab-made via a facile solvothermal reaction coupled with a following carbon reduction treatment. At an ultrathin thickness of 1.4 mm, the hierarchical porous Co/C crabapples (50 wt% filling content) provided 90% EMW absorption over a broad bandwidth of 5.9 GHz. A broad bandwidth of 5.8 GHz at 2.0 mm thickness was still achieved at a low filling ratio of 30 wt% filler content. This broad-band EMW absorption resulted from the synergy of cobalt and carbon with a significantly improved impedance matching level. The strong magnetism of cobalt endowed the composites with strong absorption ability and thin absorber thickness. The unique porous structural features also contributed to the enhanced EMW absorption by inducing multi-scatterings. The hierarchical porous Co/C crabapples with high absorbing performance together with ultrathin absorber thickness can be applied as a promising EMW absorption material.