Comparative electrochemical performance of hydrothermally synthesized NiMnFeO4 and ZnMnFeO4 spinel ferrites for high-performance supercapacitors

Abstract

The pursuit of advanced supercapacitor technologies requires the development of cost-effective electrode materials with superior charge storage properties and long-term operational stability. In this work, NiMnFeO₄ and ZnMnFeO₄ spinel ferrites were synthesized via a controlled hydrothermal process and assembled directly onto nickel substrates for symmetric supercapacitor devices. The crystallographic structure, morphology, and surface characteristics of the prepared materials were examined using FESEM, HRTEM, XRD, and XPS analyses. Electrochemical evaluation in a two-electrode configuration demonstrated that the NiMnFeO₄-based device achieved a high specific capacitance of 222.04 F g⁻¹ at 0.5 A g⁻¹, while maintaining 86.67% of its initial capacitance after 5000 charge–discharge cycles. Compared to ZnMnFeO₄, the NiMnFeO₄ electrode exhibited lower equivalent series resistance and charge transfer resistance, indicating more efficient ion transport, improved electrical conductivity, and better utilization of active sites. The combination of multiple redox-active centers, nanostructured porosity, and a robust spinel framework contributes to its excellent rate capability and electrochemical stability, positioning NiMnFeO₄ as a promising material for high-performance and sustainable energy storage systems.