In Situ Synthesized Manganese Ferrite/Carbon Composite Nano-Material: A Novel Electrode Material for High-Performance Supercapacitors

This study presents an in situ synthesis of a novel manganese ferrite/carbon (MF/C) composite material via a citrate sol–gel route followed by calcination in an inert argon (Ar) atmosphere. The structural and morphological and porosity properties were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and N₂ gas physisorption analysis. Electrochemical evaluation of the MF/C in a 3 M KOH electrolyte in a three-electrode configuration showed a high specific capacity of 39.26 mAh g⁻¹ at 1 Ag⁻¹ and a rate capability of 69% at 5 Ag⁻¹ and an equivalent series resistance (ESR) of 0.798 Ω. Subsequently, an asymmetric hybrid supercapacitor device (MF/C//AC) was fabricated using MF/C as the positive electrode and human-derived activated carbon (AC) as the negative electrode. The assembled device exhibited remarkable performance, with a wide operating voltage window of 1.4 V, a high sweeping potential of 1 V s⁻¹, a specific capacity, energy, power and maximum power of 42.4 mAhg⁻¹, 16.35 Wh kg⁻¹, 1944 W kg⁻¹ and 236 kW kg⁻¹, respectively, and excellent capacitance retention of 92% after 15,000 charge–discharge cycles. The in situ preparation approach significantly reduced synthesis time and cost compared to conventional multi-step methods, as less equipment was required, while still achieving comparable or superior electrochemical performance to other supercapacitors in the literature.