Synthesis, structural and electrochemical characterization of Mn-doped NiFe₂O₄ nanocrystals as supercapacitor electrode: Exploring the effects of varying electrolytic cations and Mn-ion implantation

Transition metal oxides (TMO) have attracted significant attention in the field of electrochemical energy storage devices due to their unique electronic structure and enhanced redox chemistry. In this report, we have prepared a Mn-doped NiFe₂O₄ nanostructured electrode sample for supercapacitor potentials. Some surface-structural probing of the synthesized materials was carried out, and the results revealed the formation of nanosheet with a spinel cubic structure and the composition of corresponding elements. Raman and Fourier transform infrared spectroscopy (FTIR) spectra studies also reaffirmed the NiFe₂O₄ spinel structural integrity with both octahedral and tetrahedral sites. The electrochemical measurements of the fabricated electrodes revealed enhanced charge storage performance, depending on the intercalated electrolytic ions and Mn-dopant content. The findings indicate that the 5%Mn@NiFe₂O₄ exhibited the highest charge storage performance in KOH_(aq) electrolyte with specific capacitance/capacity values of 913 Fg⁻¹ / 91 mAhg⁻¹, accordingly, due to the synergistic interaction of the Mn-dopant and NiFe₂O₄ host material, coupled with the enhanced electrolyte cationic transport and electrode’s low charge transfer resistance in 1 M KOH. The results revealed that the electrochemical charge storage performance of the synthesized NiFe₂O₄ electrode material, can be improved via Mn-doping and optimization in electrolytic compositions.