Integrated experimental and theoretical investigation of synthesis-controlled spinel-Hexa-ferrite nanocomposites for high-performance energy storage

A novel soft–hard ferrite nanocomposite system composed of Ni 0.55 Cu 0.2 Zn 0.25 Fe 2 O 4 (NCZFO) and SrFe 12 O 19 (SFO) was synthesized for supercapacitor and hydroelectric cell (HEC) applications using physical mixing and one-pot sol–gel auto-combustion methods. XRD with Rietveld refinement confirmed high phase purity, while Raman and FTIR analyses revealed strong interfacial interactions between the ferrite phases. FE-SEM showed improved grain uniformity and reduced agglomeration in one-pot composites. Electrochemical studies demonstrated enhanced performance for one-pot samples, achieving a specific capacitance of 1067.2 F/g at 10 mV/s for x = 0.5, with 88% capacitance retention after 5000 cycles, indicating excellent long-term electrochemical stability. HEC measurements further showed superior activity for the one-pot x = 0.5 sample, delivering an open-circuit voltage of 1.52 V, short-circuit current of 45 mA, and power output of 68.4 mW. The improved performance is attributed to synergistic interfacial effects, oxygen vacancies, and efficient ionic transport facilitating spontaneous water dissociation and redox reactions. Density functional theory calculations supported the experimental findings by confirming favorable electronic structure and enhanced charge transport. These results highlight the importance of synthesis optimization and compositional tuning for multifunctional ferrite-based energy storage and conversion devices.