Hexagonal CeO2 nanostructures: an efficient electrode material for supercapacitors

Abstract

Cerium oxide (CeO₂) has emerged as a new and promising pseudocapacitive material due to its prominent valance states and extensive applications in various fields. In the present study, hexagonal CeO₂ nanostructures have been prepared via the hydrothermal method employing cationic surfactant cetyl trimethyl ammonium bromide (CTAB). CTAB ensures a slow rate of hydrolysis to form small sized CeO₂ nanostructures. The role of calcination temperature on the morphological, structural, electrochemical properties and cyclic stability has been assessed for supercapacitor applications. The mesoscopic hexagonal architecture endows the CeO₂ with not only a higher specific capacity, but also with an excellent rate capability and cyclability. When the charge/discharge current density is increased from 2 to 10 A g⁻¹ the reversible charge capacity decreased from 927 F g⁻¹ to 475 F g⁻¹ while 100% capacity retention at a high current density of 20 A g⁻¹ even after 1500 cycles could be achieved. Furthermore, the asymmetric supercapacitor based on CeO₂ exhibited a significantly higher energy density of 45.6 W h kg⁻¹ at a power density of 187.5 W kg⁻¹ with good cyclic stability. The electrochemical richness of the CeO₂ nanostructure makes it a suitable electrode material for supercapacitor applications.