Facile synthesis of graphene-CeO₂ nanocomposites with enhanced electrochemical properties for supercapacitors

Abstract

Graphene-ceria (CeO2G) nanocomposites were prepared by using a low-temperature solution process with different weight percentages of graphene, and their electrochemical properties were investigated. Structural properties of the nanocomposites were studied by X-ray diffraction, Raman spectroscopy, and FTIR spectral analyses. FE-SEM and HRTEM images revealed a "wrinkled paper"-like morphology of the prepared composites. Elemental mapping images were recorded by using the FE-EPMA technique. XPS analyses revealed the binding states of different elements present in the composites. The composite with 5% graphene displayed a specific capacitance of 110 F g(-1), according to cyclic voltammetric studies, which is higher than that observed for pure CeO2 (75 F g(-1)). The significant increase in the specific capacitance suggests that the CeO2G is a promising material for supercapacitor applications.

Ce3+-ion, Surface Oxygen Vacancy, and Visible Light-induced Photocatalytic Dye Degradation and Photocapacitive Performance of CeO2-Graphene Nanostructures

“…From the intensity of the respective peaks, the concentration of Ce 3+ was comparatively higher in the sample analyzed compared to the peak intensity of pure-CeO 2 NPs. This confirms the presence of oxygen vacancy/defects in CeO 2 in the CeO 2 -Graphene nanostructure (1 mM) 54 . Figure S4(a) shows the fitted peak of C 1s at 284.6 eV, which corresponded to the value reported in the literature 46 .…”

“…As shown from the Ce 3+ 3d 3/2 peak, the intensity of Ce 3+ increased with increasing concentration (3 mM compared to the 1 mM CeO 2 -Graphene nanostructure). As indicated by XPS, the 1 mM and 3 mM CeO 2 -Graphene nanostructures contained a large number of defects and Ce 3+ oxidation states 44, 54 , which might lead to the formation of a surface state energy band of oxygen. Figure S4(b) exhibits the fitted peak of C 1s at 284.6 eV, which was well coordinated with the as-described value in the literature 46 .…”

“…The higher atomic weight percent of carbon clearly shows the presence of graphene sheets on which spherical-shaped CeO 2 NPs are decorated 54 . This was attributed to the combined effect of CeO 2 NPs and graphene, which imparted improved performance to the CeO 2 -Graphene nanostructure for photocapacitive and photocatalytic activities.…”

“…The 1 mM and 3 mM CeO 2 -Graphene nanostructures showed a single EPR signal at RT, which corresponds to oxygen vacancies, and was very small in the case of pure-CeO 2 NPs . Therefore, EPR showed that the 1 mM and 3 mM CeO 2 -Graphene nanostructures have characteristic paramagnetic properties and oxygen vacancies, which could impart visible light-induced photocatalytic activity 48, 52–54 . Figure 7 presents the schematic observations of the fluorite structure of CeO 2 along with oxygen vacancies and Ce 3+ at the lattice sites (Fig.…”

“…An opaque and single layer graphene sheet was clearly visible from the background of Fig. 8(a) 54 . A close observation from the HR-TEM image of the 1 mM CeO 2 -Graphene nanostructure displayed in Fig.…”