Synthesis of mesoporous structured ZnMn₂O₄ nanoparticles as electrode for supercapacitor application

Spinel ZnMn₂O₄ has been gaining more attention in the realm of supercapacitor applications due to its accessibility, affordability, sustainability, high specific capacitance, and excellent rate capability. In this study, spinel ZnMn₂O₄ was synthesized using a rapid, eco-friendly citric acid-mediated sol–gel auto-combustion approach. A thorough study was conducted to correlate the phase structure, surface morphology, functional groups, oxidation states, specific surface area, and redox reaction of the electroactive species with their potential impact on the electrochemical behaviour of electrode material. The prepared spinel ZnMn₂O₄ electrode material showed an impressive specific capacitance value of 417.5 F g⁻¹ under low electrolyte concentrations and a current density of 1 A g⁻¹. In an aqueous electrolyte, the reaction kinetics of the supercapacitor become very fast and this is responsible for its high capacitance. An excellent coulombic efficiency of 87% was obtained for this electrode material even after 5000 cycles. The exceptional electrochemical performance is mainly attributed to the nanoparticles, which have a large reaction surface area, fast transfer of ions and electrons, high ionic conductivity, and excellent structural durability. These significant results emphasize the ZnMn₂O₄, potential as a supercapacitor material.