Interfacial coupling-driven enhancement of capacitance in MnFe₂O₄/NiO nanocomposites synthesized via sol–gel auto-combustion

The development and optimization of high-performance electrode materials are crucial for the progress of next-generation supercapacitors (SCs). Extending our previous study in which pure manganese ferrite (MnFe₂O₄, MF), nickel oxide (NiO, NO) and MnFe₂O₄/NiO (MF/NO₁–₄) nanocomposites (NCs) were prepared by sol–gel auto-combustion technique and extensively studied for their structural, morphological, optical, magnetic and photocatalytic properties; the present study is aimed to further investigation on its electrochemical performance. Detailed electrochemical studies ferroelectric, dielectric, AC conductivity (σAC), cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and current–voltage (I–V) analyses were performed without any modification. Ferroelectric characterization showed that the remanent (Pᵣ) and maximum polarization (Pmax) for MF and NO were 18.36 μC cm⁻²/4.12 μC cm⁻², respectively, whereas adding more MF significantly enhanced long-range ordering of Pmax up to 29.50 μC cm⁻². The dielectric analysis showed the composition-dependent enhancements and the AC conductivity followed Jonscher’s universal power law, indicating a better charge transport mechanism at higher frequency. It was found that the MF/NO-4 achieved a high specific capacitance of 450 F/g, which is 76.12% higher than the pristine material and excellent cyclic stability (74.6% after 2000 cycles) in GCD tests. CV results also confirmed its excellent pseudocapacitive performance (694 F/g). This work uniquely highlights an interfacial-coupling driven correlation between ferroelectric/dielectric behavior and electrochemical performance, which has not been reported previously for MF/NO-4 NCs. The superior electrochemical performance is attributed to the synergistic coupling of MF and NO phases, which promotes redox kinetics, ion diffusion, and structural integrity. This work indicates the potential use of MF/NO-4-based NCs as advanced electrode materials toward high-efficiency energy storage. Graphical Abstract