Through the reduction process involving Co3O4/reduced graphene oxide and acetylene, core/shell structured Co/carbon nanotube–graphene nanocomposites were synthesized on a large scale. Because of their special structure, high attenuation constant and good complementarity between magnetic loss material and dielectric loss material, the obtained Co/carbon nanotube–graphene nanocomposites exhibited very attractive microwave absorption. An optimal reflection loss (RL) of up to −65.6 dB at 12.4 GHz was observed with a thickness of 2.19 mm, and RL values below −20 dB were obtained in almost the entire frequency range. Therefore, a simple approach was proposed to explore the high-performance microwave-absorbing materials as well as expand the fields of application of graphene-based materials.
