Currently, replacing expensive and short-lived materials for supercapacitors based on RuO ₂ with more cost-effective and high-performance materials that remain operational after a large number of cycles is a challenge. Cerium-based materials are the most attractive alternative because of cerium’s ability to quickly change oxidation state. This work proposes the synthesis of nanostructured graphene–ceria composite and studies its morphological features arising under the impact of oxygen-free graphene. The mechanism of formation of nano-ceria crystallites when the sol–gel transition occurs on the surface of graphene sheets is also considered. It has been proven that the introduction of 0.5–0.6 wt% graphene sheets into nano-ceria ensures the preservation of its single-phase state, while simultaneously increasing its dispersion. Using the dilatometry method, it has been determined that uniformly distributed sheets of oxygen-free graphene lead to a decrease in temperature of the beginning of composite sintering by 175°C compared with pure nano-ceria and increase the shrinkage value by two times, which, in turn, should promote better sintering. This study fills a gap in the synthesis and characterization of oxygen-free graphene composites, promising raw materials for small devices and large power plants.

A method is proposed for the synthesis of nanostructured composites based on graphene and CeO₂, which combines sol-gel and sonochemical methods. A feature of the method is that, when the graphene content is not more than 2 wt %, its uniform distribution in the volume of the material is achieved without the formation of an impurity phase. In addition, oxygen-free graphene with a sheet thickness of 3‒5 nm is used in the synthesis as a suspension obtained by ultrasonic exfoliation in an alkalized by KOH water-alcohol solution of dodecylamine. The formation of a composite in a mixed colloid occurs in such a way that the sol-gel transition and subsequent crystallization of nano-CeO₂ occur on the graphene sheets. However, chemical interaction of the latter and CeO₂ in the composite is not observed, which contributes to the preservation of the sp² electron system of graphene and, as a result, the preservation of its unique electronic properties. The graphene sheets form a layered structure of composite agglomerates, and isolated CeO₂ nanocrystals are incorporated into these differently oriented layers. It is determined that CeO₂ dispersion in the composite is higher than in pure CeO₂ nanopowder. Estimating the phase and chemical purity of the synthesized composite, it can be argued that the developed method for obtaining nanostructured powders based on graphene and CeO₂ is promising as the basis for an economical and environmentally friendly technology for the production of initial substances for fine-grained electrical ceramics.

A comparative study of the morphology, phase composition, and thermal behavior of nanocrystalline ceria powder and graphene-containing composites based on it, which were synthesized using two methods combining sol-gel and sonochemical techniques, has been carried out. In one case, ceria crystallization occurred on the oxygen-free graphene sheets as a result of the interaction of Ce-containing sol and few-layer graphene suspension in an N,N-dimethyloctylamine-aqua emulsion. In another case, the graphene sheets were deposited on ceria nanocrystallites by combining the suspensions of ceria and graphene in an isopropanol-aqua mixture. It was found that the introduction of less than 1 wt % graphene leads to a decrease in the sintering temperature of nanocrystalline ceria by 175°C if the composite was obtained from a Ce-containing sol, and by 212°C if a nanocrystallite ceria was used for this purpose. The shapes of the shrinkage curves and shrinkage rates of composites also differ, and in both cases there are significant differences from the data for pure nanocrystallite ceria obtained under the same conditions.