A synergistic experimental and computational study on cation engineering in Mn-doped CoFe2O4 nanoparticles for high-performance supercapacitors

Spinel-type metal ferrites are promising candidates for supercapacitor electrodes due to their multiple redox-active sites, structural robustness, and tunable electronic properties. In this work, a synergistic experimental and computational approach is employed to engineer Mn-substituted cobalt ferrite, Mn_xCo_1-xFe₂O₄ (0 ≤ x ≤ 1), synthesized via a polyol-mediated solvothermal method. The Mott–Littleton defect model was utilized to evaluate substitution energetics and identify the most favorable doping concentration. Computational insights revealed that 75% Mn substitution (x = 0.75) minimizes defect formation energy and stabilizes the spinel lattice, guiding the experimental design. Structural characterization confirmed the formation of a cubic spinel phase, and FT-IR spectroscopy identified characteristic metal–oxygen vibrations at tetrahedral and octahedral sites. SEM imaging showed uniformly distributed spherical nanoparticles with diameters of 20–30 nm. Electrochemical analysis in a three-electrode setup demonstrated a significant improvement in capacitive behavior with increasing Mn content, with the x = 0.75 composition achieving the highest specific capacitance of 493 F g⁻¹ at 5 A g⁻¹. This study underscores the effectiveness of coupling atomistic modeling with materials synthesis for rational design of high-performance supercapacitor electrodes.