Cerium oxide immobilized reduced graphene oxide hybrids with excellent microwave absorbing performance

Abstract

Microwave absorbing materials with high absorption over a broad bandwidth when they have a small thickness are strongly desired due to their widespread applications. Herein, cerium oxide immobilized reduced graphene oxide (CeO₂–rGO) hybrids with excellent microwave absorbing performance have been fabricated by a versatile one-step hydrothermal approach. Modern measurement techniques, including X-ray diffraction, Raman spectroscopy, electronic microscopy, X-ray photoelectron spectroscopy and vector network analysis, have been conducted to characterize the chemical composition, microstructure and electromagnetic performance of the as-obtained hybrids. Morphological analysis reveals that the CeO₂ nanocrystals are homogeneously immobilized onto the rGO surface without any significant agglomeration. Interestingly, significant enhancement in the microwave absorbing performance has been observed for all the CeO₂–rGO hybrids. For example, a CeO₂–rGO hybrid with a 10 : 1 mass ratio of CeO₂ to GO exhibits a minimum reflection loss (RL) of −45.94 dB, which is 73.35 times and 6.14 times that of the lone CeO₂ and rGO, respectively. Moreover, the CeO₂–rGO hybrid shows a broadband absorption feature with an effective absorption bandwidth (RL < −10 dB) of 4.5 GHz, and can be exploited for practical application in a frequency range of 3.68–18.00 GHz via tuning of the thickness. Investigation of the structure–property correlation indicates that such enhancements are attributed to conductive loss, polarization loss and multiple reflections which are mainly derived from the unique CeO₂–rGO based architecture. In addition, the higher oxygen vacancy concentration of CeO₂ in hybrids can promote electron transfer between CeO₂ and rGO, leading to microwave attenuation enhancement. It is expected that these CeO₂–rGO hybrids can be used as new microwave absorbers.