Paramagnetic CoS2@MoS2 core-shell composites coated by reduced graphene oxide as broadband and tunable high-performance microwave absorbers

Abstract Nowadays, developing microwave absorbers with tunable and high-efficiency electromagnetic absorbing performance is still facing many challenges, in spite of their wide applications in civilian and military roles. Here, flower-like CoS 2 @MoS 2 core-shell microspheres coated by reduced graphene oxide (rGO) is designed and synthesized by a facile hydrothermal method. The formation of typical flower-like core-shell microspheres is attributed to the combined effect of CoS 2 microsphere and MoS 2 nanosheet during hydrothermal reaction process. Further, with the addition of graphene oxide, the wrinkled rGO nanosheet is successfully coated on the surface of flower-like CoS 2 @MoS 2 core-shell microspheres, forming a specific three-dimensional (3D) structure. The microstructure, morphology and chemical composition of the as-synthesized composites are characterized by XRD, Raman, XPS, SEM and TEM. Magnetic measurement shows that CoS 2 @MoS 2 microspheres exhibit paramagnetic behavior. The electromagnetic properties of CoS 2 @MoS 2 /rGO composites are measured by a vector network analyzer, where the unique flower-like core-shell structure and multiple interfaces, particular surface defects as well as the specific electric properties of CoS 2 , MoS 2 and rGO lead to the impressive microwave absorption properties. The effect of filler loading ratio on microwave absorption performance of the wax-based absorbers is analyzed in detail. It is noted that the sample with 20 wt% loading of CoS 2 @MoS 2 /rGO exhibits optimal reflection loss (RL) characteristics, where the minimum RL is -58 dB with a broad effective bandwidth of 6.24 GHz from 11.76 to 18 GHz at 2.4 mm. Apparently, the as-synthesized CoS 2 @MoS 2 /rGO composites can be acted as a lightweight and broadband microwave absorber with low filler loading. This work offers a new strategy to design high-performance and tunable microwave absorbers with individual microstructure and morphology using a facile, low-cost and environmental-friendly synthesis route.