Deep eutectic solvent mediated nanostructured copper oxide as a positive electrode material for hybrid supercapacitor device

Abstract

Metal oxides have received significant attention for various applications over the last few decades due to their better structural, morphological, and electrochemical properties. Herein, a green approach is introduced for the synthesis of nanostructured CuO using a choline chloride urea (CCU)-based deep eutectic solvent (DES) method. The effects of varying reaction times upon the surface morphological and electrochemical properties of the CuO are examined. In particular, the CuO sample obtained at 12 h of reaction time is shown to exhibit a porous nanograin-like surface morphology with a grain size of less than 20 nm and an excellent specific capacity (Cs) of 176 mAh g−1 at a scan rate of 5 mV s−1. Further, the practicability of the CuO-based electrode is demonstrated by the fabrication of a CuO//activated carbon (AC) hybrid supercapacitor device. The CuO//AC shows a noteworthy electrochemical performance, with a Cs of 82 mAh g−1, specific energy of 35.86 Wh kg−1, a specific power of 2017 W kg−1, and a long-term stability of 98% after 2000 cycles.