Figure 4

CV curves, specific capacitance, galvanostatic charge–discharge curve, and Nyquist plots of electrodes. (a) CV curves of the as-prepared ZnO, graphene and the graphene-ZnO hybrid electrode at a scan rate of 5 mV s⁻¹ in 0.5 M Na₂SO₄ electrolyte solution. (b) Specific capacitance of ZnO, pristine graphene, and the graphene-ZnO hybrid electrode at different scan rates calculated from CV curves. (c) Galvanostatic charge–discharge curve of the graphene-ZnO hybrid electrode at a constant current density of 2.0 mA cm⁻². (d) Nyquist plots for ZnO, pristine graphene, and the graphene-ZnO hybrid electrode.