Zinc oxide nanoparticles and activated charcoal-based nanocomposite electrode for supercapacitor application

Abstract

In the present work, zinc oxide (ZnO) nanoparticles (NPs) have been synthesized at room temperature using co-precipitation method for the use as an electrode material by forming a composite with activated charcoal (AC) powder for its application in electrochemical supercapacitor. For synthesizing of ZnO nanoparticles, dry zinc chloride (ZnCl2) and sodium hydroxide (NaOH) have been used as the initial precursors. The obtained ZnO nanopowder has been calcined at 400, 500 and 600 °C for 2 h. The nanoparticles have been characterized by powder X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The nanocomposite has also been investigated by synchrotron radiation-based X-ray photoelectron spectroscopy (XPES). Supercapacitor cells (symmetrical) have been fabricated by making use of different composition of zinc oxide (ZnO) nanoparticle-activated carbon (AC). Electrochemical properties of the prepared nanocomposite electrodes and fabricated supercapacitor cells have been characterized using a.c. impedance, cyclic voltammetry (CV) and charge–discharge (CD) techniques by using 6 M KOH and 1 M NaOH as the electrolytes. The optimized composition is 1:1 (mass ratio) of ZnO and activated charcoal, and 600 °C for 2 h is an optimized temperature for synthesis of nanoparticles. The specific capacitance of the supercapacitor cells is stable up to 2000 cycles at 100 mV cm−2, which show that the device has good electrochemical reversibility and cycle life with 6 M KOH and 1 M NaOH electrolyte.