High-Performance Microwave Absorption of MOF-Derived Core-Shell Co@N-doped Carbon Anchored on Reduced Graphene Oxide

Nanocomposites of MOF-derived N-doped-carbon-wrapped cobalt anchored on reduced graphene oxide (Co@NC@RGO) have been successfully fabricated for use as microwave absorption materials. A unique core-shell nanostructure with cobalt nanoparticles as core and N-doped graphitized carbon as shell was grown on the surface of laminated reduced graphene oxide (RGO). An enhanced synergistic effect between magnetic and dielectric components can be readily achieved by changing the dispersion of Co@NC nanoparticles on RGO. The as-synthesized microspheres are composed of numerous nanoscale core-shell Co@NC units, which combined magnetic Co cores with intrinsically contributing magnetic loss and N-doped graphitized carbon providing a pathway for electron transfer as well as transition between magnetic Co cores and high electrical conductivity of RGO. The resulting Co@NC@RGO composites exhibit excellent reflection loss (RL) values and effective absorption bandwidths. The optimized Co@NC@RGO-3 minimum RL (RLmin) value could reach −46.5 dB at 9.4 GHz with a thickness of 3.5 mm. Tuning the thickness from 1.5–5 mm, the effectivity absorption frequency range could achieve up to 14.3 GHz (from 3.7 to 18 GHz). The excellent microwave absorption performance may be attributed to the magnetic loss, dielectric loss and interfacial polarization.