Enhanced electrochemical properties of Ni2+/Fe3+ doped ZnCo2O4/rGO nanocomposite for superior supercapacitor performance

The work reports a Ni 2+ /Fe 3+ co-doped ZnCo 2 O 4 and their composites with reduced graphene oxide for supercapacitor electrodes. The XRD analysis revealed slight peak shifts indicating lattice strain without phase degradation. XPS results confirmed the presence of Zn 2+ , mixed Co 2+ /Co 3+ states, and the incorporation of Ni 2+ and Fe 3+ alongside Co 2+ and Co 3+ , with rGO bonding. Morphological studies showed reduced particle agglomeration, leading to a porous and rough surface beneficial for ion transport. Spectral studies supported the existence of strong metal‑oxygen bonds and oxide-rGO interactions. BET analysis indicated an increased surface area (81.05 m 2 /g) and mesopore development (∼19 nm). Kinetic analysis indicated a transition to surface-controlled charge storage, with the optimal co-doping showing the highest b-value (0.6618). Electrochemical performance demonstrated hybrid behavior with significant redox activity, achieving a specific capacitance of 1573 F/g at 5 mV/s and an energy density of 94 Wh/kg at a power density of 245 W/kg (three-electrode configuration). GCD measurements indicated a specific capacitance of 718 F/g at 1 A/g with prolonged discharge. The composite maintained 95% of its initial capacitance after 5000 cycles at 5 A/g, indicating excellent cyclic stability. This article gives great insight into the development of next-generation electrode materials appropriate for supercapacitor applications.