Size-controlled ceria nanocubes obtained via hydrothermal route for electrochemical capacitors

CeO2 nanocubes of various sizes were synthesized using a modified urea-assisted hydrothermal approach, and their electrochemical performances were investigated for supercapacitor applications. The formation of ceria nanocubes of various sizes were confirmed through TEM and XRD studies. The increased amounts of urea during the hydrothermal growth of ceria nuclei resulted in the joining of more nanocrystals, followed by sharing of common crystallographic orientations to form large crystals that led to well-developed crystallinity with increased size. The reversible redox transition between Ce4+ and Ce3+ in the crystal structure led to excellent electrochemical performance, reflected in cyclic voltammetry plots. The chronopotentiometry showed a coulombic efficiency greater than 90% at 1 A/g, a capacity of 25 C/g, and a capacitance of 88.71 F/g at 5 A/g for nanocubes of sizes 18-20 nm. Furthermore, the excellent cyclic stability found through multiple charge-discharge testing cycles indicated that the desired nanocube morphology of ceria could be used together with other metal oxides or carbon-allotropetype electrode materials for next-generation supercapacitors. (C) 2019 Elsevier B.V. All rights reserved.