Optimized electrospun MnFe₂O₄ nanofibers as promising electrode materials for supercapacitor applications: physical and electrochemical properties

Spinel-type MnFe₂O₄ nanofibers were fabricated using a sol–gel electrospinning technique followed by calcination at different temperatures (400, 500 and 600 °C). The resulting products were thoroughly investigated for their physical and electrochemical properties. XRD analysis revealed the presence of a secondary Fe₂O₃ phase alongside the initial cubic phase for electrospun fibers calcined at 600 °C. FESEM images showed that the as-spun fibers calcined at 400 °C had a hollow nanofiber morphology, which gradually converted to porous nanofiber with increasing calcination temperature. Optical studies indicated that the optical band gap decreased from 1.53 to 1.34 eV with an increase in calcination temperature. The sample calcined at 500 °C exhibited the best magnetic properties with a saturation magnetization of 44.2 emu g⁻¹ and a coercivity of 73.0 Oe. The electrochemical analysis revealed that the MnFe₂O₄ nanofibers calcined at 500 °C had the superior specific capacitance of 365 F g⁻¹ at 1 A g⁻¹ and retained 92.54% of its initial specific capacitance even after 3000 cycles, demonstrating good cycling stability. These results suggest that the MnFe₂O₄-500 °C electrode material is a promising candidate for pseudocapacitor applications.