ZnO-CuO nanoparticles enameled on reduced graphene nanosheets as electrode materials for supercapacitors applications

The current energy crisis situation, combined with the recent development of renewable energy resources, has promoted the development of energy storage materials for supercapacitors and rechargeable metal ion batteries. In this regard, metal oxide-based two-dimensional materials such as reduced graphene oxide nanocomposites have tremendous potential for the aforementioned purpose. The ZnO-CuO/rGO nanocomposites were designed and synthesized by a simple, cost-effective co-precipitation method. The structural and morphological analysis of synthesized nanomaterials ZnO, CuO, and ZnO.CuO/rGO nanocomposites were extensively characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Rama spectra, Brunauer-Emmett-Teller (BET) surface area, and thermogravimetric analysis (TGA). The XRD pattern results of ZnO nanoparticles show wurtzite structure, copper oxide nanoparticles show monoclinic phase structure, and ZnO-CuO/rGO composites show a mixture of wurtzite, monoclinic phase, and hexagonal structure. The surface morphology of the ZnO-CuO/rGO nanocomposite shows the spherical and hexagonal-shaped ZnO-CuO nanoparticles uniformly arranged on the surface of graphene oxide sheets. The binding energy values of the nanocomposite confirm the oxidation states of Zn, Cu, C, and O elements in ZnO-CuO/rGO presented in the XPS studies. The electrochemical activity of the ZnO-CuO/rGO nanocomposite in 1 M H2SO4 electrolyte exhibits a specific capacitance of 260.7 F/g at 0.5 A/g, high energy density, and excellent cycle stability. Even after 10,000 cycles, 98.7% of the initial supercapacitance remains. These findings suggest that the ZnO-CuO/rGO nanocomposite has a bright future as an electrode material in supercapacitors.