Comparison of the electrochemical performance of CeO2 and rare earth-based mixed metallic oxide (Ce0.9Zr0.1O2) for supercapacitor applications.

CeO2 and Ce0.9Zr0.1O2 are prepared from the sol-gel method to investigate and compare their electrochemical properties for supercapacitor applications. Structural, morphological, and elemental studies have been done for CeO2 and Ce0.9Zr0.1O2 by XRD, SEM, and EDX. Cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques are used to study the electrochemical performance of these materials. Doping enhances the electrochemical performance of the electrode, by improving the specific capacitance (~150%, 243 F g-1 from 96 F g-1) for the doped system @2 mV s-1 Vs. Ag/AgCl reference electrode in 2 mol L-1 KOH electrolyte solution. Ce0.9Zr0.1O2 shows only ~30% of capacitance degradation for a ten folds increase in current densities. Ce0.9Zr0.1O2 also shows 16% capacitance degradation after 800 cycles with excellent Columbic efficiency (~100%) @2 A g-1 current density. Partial replacement of Ce4+ ion (0.97 {\AA}) with Zr4+ ion (0.84 {\AA}) results in a decrease in lattice parameter, as confirmed by Rietveld refinement. Ce0.9Zr0.1O2 has provided good energy, and power density of 1.128 Wh kg-1and 112.5 W kg-1 respectively. Furthermore, better diffusivity of the Ce0.9Zr0.1O2 in KOH electrolyte (indicated using Randles-Sevcik equation-based analysis) is correlated with better electrochemical performance. These insights presented here clearly indicate that Zr doping into CeO2 results in a promising candidate material for electrochemical and supercapacitive applications.