Electrochemical Investigation of Magnesium-Doped Copper Ferrite Nanostructures for Asymmetric Supercapacitor Applications

In this study, the synthesis of magnesium-doped copper ferrite, namely Cu_xMg_1−xFe₂O₄ (x = 1, 0.9, 0.7, and 0.5), is achieved using a facile microwave route, and the cubic crystalline structure, functional group, and nanostructured materials are discussed. The electrochemical studies of the magnesium-doped copper ferrite (MCF) are carried out by assembling a three-electrode conventional electrochemical cell with MCF samples as working electrode, a platinum wire as counter electrode, a silver (Ag)/silver chloride (AgCl) as reference electrode, and 2 M KOH aqueous solution as electrolyte. The study of the electrochemical performance of Mg-doped and undoped copper ferrite electrodes reveals that they show battery-type behavior with the transfer of two electrons (Mg to Mg²⁺) in 2 M KOH electrolyte in the potential window of 0.45 V to 0.35 V. Further, un-oxidized MgO oxidizes, leading to a quasi-conversion reaction. Additionally, the electrode (MCF) exhibits a greater specific capacity of 737.5 F g⁻¹ at 1 A g⁻¹. It is found that the MCF3 electrode retains 70% of its initial capacitance, which is higher than the CF electrode (33%), after 4000 continuous galvanostatic charge/discharge (GCD) cycles. An asymmetric supercapacitor cell is fabricated using MCF as the positive electrode, activated carbon (AC) as the negative electrode, 2 M KOH as the electrolyte, and polypropylene as the separator. The fabricated MCF//AC supercapacitor yields maximum specific energy of 62.61 W h kg⁻¹ at specific power of 1168 W kg⁻¹. These electrochemical features suggest that MCF is a feasible candidate material for developing supercapacitor electrodes.