Facile synthesis of Cu2O/CuO/RGO nanocomposite and its superior cyclability in supercapacitor

A reduced graphene oxide (RGO)-based nanocomposite of redox counterpart of the oxides of Cu(I)-Cu(II) pair for Faradaic reaction, Cu2O/CuO/RGO, was controllably synthesized through a facile, eco-friendly one-step hydrothermal-assisted redox reaction of elemental Cu and graphene oxide (GO) without the addition of any other reagents. The resultant Cu2O/CuO/RGO nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). It is found that, when dealloyed nanoporous Cu was used as a Cu source, the uniform spherical Cu2O/CuO nanoparticles with double size scales (∼25 nm and ∼5 nm) were anchored on RGO sheets. This Cu2O/CuO/RGO nanocomposite redox counterpart exhibits improved rate capability and excellent cycling stability, i.e., only ca. 21.4% of the capacity was lost when the discharge current density increases from 1 A g−1 (173.4 F g−1) to 10 A g−1 (136.3 F g−1). Especially, the capacity remains almost unchanged (98.2%) after 100,000 cycles at 10 A g−1. The good electrochemical performance and simple accessibility prove that this Cu2O/CuO/RGO composite consisting of a pair of redox counterparts is a promising material for supercapacitor applications.