Synthesis and Characterization of Ternary α-Fe₂O₃/NiO/rGO Composite for High-Performance Supercapacitors

Herein, pure α-Fe₂O₃, binary α-Fe₂O₃/NiO, and ternary α-Fe₂O₃/NiO/rGO composites were prepared by a hydrothermal method. The properties of the prepared materials were studied by powder X-ray diffraction, scanning electron microscopy, TEM, XPS, and Brunauer-Emmett-Teller techniques. The clusters of smaller α-Fe₂O₃ nanoparticles (∼30 nm) along with conducting NiO was freely covered by the rGO layer sheet, which offer a higher electrode-electrolyte interface for improved electrochemical performance. The ternary composite has shown a higher specific capacitance of 747 F g^-1@ a current density of 1 A g^-1 in a 6 M KOH solution, when compared with that of α-Fe₂O₃/rGO (610 F g^-1@1 A g^-1) and α-Fe₂O₃ (440 F g^-1@1 A g^-1) and the nanocomposite. Moreover, the ternary α-Fe₂O₃/NiO/rGO composite exhibited a 98% rate capability @ 10 A g^-1. The exceptional electrochemical performance of ternary composites has been recognized as a result of their well-designed unique architecture, which provides a large surface area and synergistic effects among all three constituents. The asymmetric supercapacitor (ASC) device was assembled using the ternary α-Fe₂O₃/NiO/rGO composite as the anode electrode (positive) material and activated carbon as the cathode (negative) material. The ASC device has an energy density of 35.38 W h kg^-1 at a power density of 558.6 W kg^-1 and retains a 94.52% capacitance after 5000 cycles at a 1 A g^-1 current density.