Recycling waste dry cells into sustainable supercapacitor electrodes <i>via</i> cobalt-doped zinc ferrite/rGO nanocomposite

This research introduces a sustainable strategy for supercapacitor fabrication by utilizing waste-dry cell battery-derived materials to simultaneously meet energy-storage demands and mitigate environmental concerns. Cobalt-doped zinc ferrite (Co_0.5Zn_0.5Fe₂O₄) (CZF) of spinel structure was synthesized using a hydrothermal method, and subsequently, 2D reduced graphene oxide (rGO) was derived from waste dry-cell batteries. The integration of the CZF/rGO nanocomposite was achieved <i>via</i> a straightforward sonication process, which was confirmed by a series of spectroscopic analyses, <i>viz.</i>, FTIR, SEM, EDX, XRD, XPS, TEM and BET analyses. The SEM observations together with BET surface area analysis revealed that the nanocomposite possesses a porous structure, which can effectively promote electrolyte ion transport while providing a large surface area for enhanced charge storage. The electrochemical behavior was investigated in a 2 M KOH electrolyte using a three-electrode system, where a glassy carbon electrode (GCE) served as the working electrode, through CV, GCD, and EIS. The CZF/rGO nanocomposite electrode exhibits a specific capacitance of 91 F g^-1 (0.13 F cm^-2) at 10 A g^-1, while maintaining a relatively low internal resistance of 1.9 Ω. Moreover, the assembled asymmetric device exhibits an energy density of 3.99 Wh kg^-1 at a power density of 450 W kg^-1. The device also shows good cycling stability, retaining 84.1% of the initial capacitance after 1000 cycles. These improvements arise from the combined contribution of CZF and rGO, providing abundant active sites, improved charge transport, and a high accessible surface area. Overall, the findings demonstrate that materials derived from waste can serve as promising and sustainable candidates for energy storage, with potential for practical supercapacitor devices demanding stable, fast-charging, and environmentally friendly electrodes.