Structural, magnetic and electrochemical investigation of cobalt and zinc ferrite nanoparticles as potential electrode materials for supercapacitor applications.

This study investigates the structural, magnetic, and electrochemical properties of CoFe2O4 and ZnFe2O4 nanoparticles. Structural analyses confirmed the formation of a single-phase cubic spinel structure, while TEM revealed average particle sizes of ∼25 nm for CoFe2O4 and ∼18 nm for ZnFe2O4 nanoparticles. The low loop squareness observed for both systems suggests their potential suitability for high-frequency magnetic applications. XPS analysis showed that Co and Zn were present predominantly as Co2+ and Zn2+, respectively, while Fe was mainly present as Fe3+ in both ferrite samples. The electrochemical performance of the ferrite-modified electrodes was evaluated using DPV, CV, GCD, and EIS. The CoFe2O4 electrode exhibited a higher current response, lower charge-transfer resistance, and stronger pseudocapacitive behavior than ZnFe2O4. Its performance was further investigated in 0.1 M Na2SO4 and 0.1 M KOH. The alkaline electrolyte promoted faradaic charge-storage reactions, yielding a maximum Csp of 61.54 F g-1 at 0.125 A g-1 and indicating enhanced electrode-level electrochemical performance. Although the neutral electrolyte provided lower capacitance, it showed excellent stability over 5000 cycles. In KOH, the capacitance recovery was ∼99.50% after prolonged cycling. Overall, these results demonstrate the potential of CoFe2O4 nanoparticles as promising electrode materials for supercapacitor applications, based on their favorable electrode-level electrochemical characteristics.