Highly efficient asymmetric supercapacitor based on magnetic CeO2@γ-Fe2O3 composite and reduced graphene oxide electrodes

Abstract

The CeO2@γ-Fe2O3 nanocomposites with varying CeO2 content (0–50 mol%) were prepared by the sol-gel electrospinning. XRD analysis confirmed the phase transition from α-Fe2O3 to cubic γ-Fe2O3 with addition of Ce ions and dominant phase for 30, and 50% CeO2@γ-Fe2O3 nanocomposites was cubic CeO2. FESEM images revealed that the ribbon-like α-Fe2O3 convert to the CeO2@γ-Fe2O3 nanofibers. The EDS map images and FTIR confirmed the homogenous distribution of elements and chemical bonds, respectively. Interestingly, the induced phase transition resulted in superparamagnetic behavior of 10% CeO2@γ-Fe2O3. The supercapacitive performance of the CeO2@γ-Fe2O3 nanofibers grown on the nickel foam were examined by electrochemical analyzes. The 50% CeO2@γ-Fe2O3 electrode demonstrated the highest specific capacitance of 1169.3 F g−1 at a current density of 1 A g−1 and the capacitance retention of 89.7% after 1000 cycles at 7 A g−1. Additionally, asymmetric supercapacitor (ASC) was assembled using CeO2@γ-Fe2O3 and rGO as cathode and anode electrodes, respectively. The CeO2@γ-Fe2O3//rGO ASC displayed an energy density of 36.8 Wh kg−1 at a power density of 700 W kg−1, demonstrating its potential for use in energy storage systems.