Magnetic Dodecahedral CoC-Decorated Reduced Graphene Oxide as Excellent Electromagnetic Wave Absorber

Abstract

A two-step method has been adopted to synthesize cobalt nanoclusters in carbon (CoC)-decorated reduced graphene oxide (rGO) from graphene oxide (GO) and ZIF-67 as an excellent stable electromagnetic wave (EMW) absorber. Firstly, the electrostatic force between GO and Co2+ gave rise to in situ growth of ZIF-67 on GO (ZIF-67–GO). Then CoC–rGO was obtained by calcination of ZIF-67–GO hybrids. The ligand is introduced as the nitrogen source to GO. The crystal structure, chemical composition, and magnetic properties of CoC–rGO were investigated by x-ray powder diffraction analysis, Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and vibrating-sample magnetometry. The morphology was observed by scanning electron microscopy and transmission electron microscopy. By adjusting the ratio of GO to ZIF-67, the electromagnetic parameters of CoC–rGO can be optimized. It was found that the sample consisting of 10 wt.% CoC–rGO-2 in a paraffin matrix exhibited excellent EMW absorption performance, reaching a minimum reflection loss (RLmin) of −44.77 dB with thickness of 2.1 mm and an effective bandwidth (RL ≤ −10 dB) of up to 5.2 GHz at thickness of 1.8 mm. The results of this study open an effective and simple avenue for the design of EMW absorbers using metal–organic framework (MOF) and low-cost carbon materials.