Electrodeposited CuO nanoparticles from e-waste to improve the performance of graphene/SiO2/NiO/V2O5-based supercapacitors

The development of flexible and high-performance energy storage devices is essential for next-generation portable electronics. In this work, flexible graphene (G)-based supercapacitors (SCs) were fabricated using electrodes based on a SiO2/NiO/V2O5 (SiNi) composite, which were decorated with copper oxide (CuO) nanoparticles (NPs) via electrodeposition. The electrodeposition was carried out using a copper ion electrolyte prepared by sulfuric acid leaching of e-waste (printed circuit boards from cell phones). The G/SiNi-SC device, fabricated using G/SiNi-E electrodes and without electrodeposited CuO NPs, delivered a specific capacitance of 235.71 F/g. The SC performance increased drastically after the electrodeposition of CuO NPs on the electrodes. In particular, the device assembled with G/SiNi-E electrodes and using an electrodeposition time of 3 min (G/SiNi3-SC) exhibited the best performance, showing a maximum capacitance of 614.73 F/g, representing an increase of 260.8% compared to the G/SiNi-SC device. Spectroscopic analyses (UV–Vis, Raman, and XPS) associated the improved electrochemical performance with the presence of oxygen vacancies and the coexistence of Ni2+, Cu2+, and V4+/V5+ redox species. Moreover, the G/SiNi3-SC device retained 92% of its capacitance after 1000 charge–discharge cycles and 85% after 1000 bending cycles, demonstrating both electrochemical and mechanical stability. These results highlight a sustainable and efficient route for designing flexible SCs by combining metal-oxide composites with e-waste-derived CuO, offering promising applications in portable energy storage.