Synthesis of freestanding 2D CuO nanosheets at room temperature through a simple surfactant free co-precipitation process and its application as electrode material in supercapacitors

Abstract

In this report, freestanding two dimensional copper oxide nanosheets (2D CuO NS) of size 0.9–1.3 µm and thickness 3–4 nm has been synthesized at room temperature by a surfactant free one pot co-precipitation process. The as synthesized 2D CuO nanosheets are found to have higher band gap of 2.1 eV than bulk CuO, owing to the quantum confinement effect. Electrochemical properties of the 2D CuO nanosheets are studied using two electrode configuration where considerably high specific capacitance (120 F/g), high energy density (26 Wh/kg) and power density (960 W/kg) are observed. Further improvement in the electrochemical performance of the supercapacitor device has been achieved by decorating 2D CuO nanosheets on electrically conductive reduced graphene oxide (rGO). The specific capacitance and energy density of CuO NS/rGO nanocomposite is determined and found to be 235 F/g and 47 Wh/kg respectively which are significantly higher in comparison to that of pristine 2D CuO nanosheets. Moreover, the CuO NS/rGO nanocomposite also exhibit enhanced specific capacitance up to 438 F/g at a potential window between±1 V as observed from cyclic voltammetry study. The results clearly indicate that 2D copper oxide nanosheet based electrode materials are promising for applications in supercapacitor devices.