Pseudocapacitive performance of vertical copper oxide nanoflakes

Vertical copper oxide (CuO) nanoflakes have been formed by oxidation in NaOH solution. Their structural, surface morphology and oxidation states were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) respectively. Pseudocapacitive behavior of CuO nanoflakes was investigated by cyclic voltammetry and constant current charge–discharge test. CuO nanoflakes were vertically grown with high lateral aspect ratio and consist of monoclinic lattice as shown by the presence of two peaks close to 2θ = 35.6o and 38.7o in the XRD. Charge–discharge test gave a capacitance value of 190 F g− 1 in 1.0 M KOH electrolyte at 2 mA cm− 2 current density. The cycling test showed 67% stability after 2000 cycles and reduced specific capacitance from 190 F g− 1 to 125 F g− 1. Specific capacitance of CuO nanoflakes is higher than 26.44 F g− 1 of globular CuO at 2 mA cm− 2 as reported in literature due to enhanced specific surface area. Highlights ► CuO nanoflakes prepared by chemical oxidation in alkaline baths ► Porosity of nanoflakes enhanced electrochemical capacitance. ► Suitable for low cost binder-free supercapacitor electrode