Tailoring electrochemical properties of CoFe2O4 via Ru substitution for high-performance supercapacitor electrodes

In an effort to advance sustainable solutions for next-generation energy storage, this study presents a green synthesis strategy for ruthenium-doped cobalt ferrite nanoparticles (CoRu x Fe 2-x O 4 ; x = 0.10, 0.20, and 0.30), employing Moringa oleifera gum as a natural chelating agent. Through an eco-friendly sol–gel method, The obtained nanocrystalline spinel structures accompanied by trace amounts of RuO 2 , as verified by XRD, FESEM, and XPS characterizations. Raman spectroscopy confirms the preservation of the spinel framework and reveals Ru-induced local lattice distortion and modified metal–oxygen interactions, which correlate with the enhanced electrochemical response of the optimized composition. Ruthenium incorporation leads to progressive lattice expansion, improved particle dispersion, and enhanced surface chemistry enabling dominant surface-controlled capacitive charge storage with additional pseudocapacitive contributions arising from fast and reversible redox reactions. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) reveal that the x = 0.30 composition delivers an exceptional specific capacitance of 4320.5 F/g at 20 mV/s, attributed to synergistic surface-controlled charge storage, mixed-valence redox activity of Co/Fe species, and the presence of electroactive RuO 2 . These findings demonstrate the synergistic effects of Ru substitution and biopolymer-assisted synthesis in tailoring nanostructured ferrites for energy storage applications. The study underscores a sustainable approach toward designing high-capacity supercapacitor electrodes with superior electrical conductivity and charge transfer efficiency. Sustainable Ru-doped CoFe 2 O 4 Nanoferrites: Green Synthesis with Superior Charge Storage for Next-Generation Supercapacitor. • Ruthenium-substituted CoFe 2 O 4 nanoparticles were synthesized via a green sol–gel method using Moringa oleifera gum. • The sample with x = 0.30 achieved a high specific capacitance of 4320.5 F/g at 20 mV/s. • Ru substitution improved lattice structure, conductivity, and redox activity. • The material shows promise as a sustainable electrode for high-performance supercapacitors.