College of Humanities and Sciences, Department of Mathematics and Sciences, Ajman University , PO Box 346, Ajman, United Arab Emirates
Aneela Tahira
Institute of Chemistry, Shah Abdul Latif University Khairpur Mirs , Sindh, Pakistan
Muhammad Ali Bhatti
Centre for Environmental Sciences, University of Sindh Jamshoro , 76080, Sindh, Pakistan
Imran Ali Halepoto
Institute of Physics, University of Sindh , Jamshoro, 76080, Pakistan
Gulzar Ali
Institute of Chemistry, University of Sindh , Jamshoro, 76080, Pakistan
Ihsan Ali Mahar
Institute of Chemistry, University of Sindh , Jamshoro, 76080, Pakistan
Irum Naz
Institute of Chemistry, University of Sindh , Jamshoro, 76080, Pakistan
Aqeel Ahmed Shah
Wet Chemistry Laboratory, Department of Metallurgical Engineering, NED University of Engineering and Technology , University Road, Karachi, 75270, Pakistan
Abdul Ghaffar Solangi
Institute of Chemistry, Shah Abdul Latif University Khairpur Mirs , Sindh, Pakistan
The development of new energy conversion and storage technologies has contributed to the widespread use of renewable energy. However, new methodologies for electrochemical energy storage systems remain to be developed. This study presents a facile, low-cost, scalable, and environmentally friendly method for the synthesis of nickel oxide (NiO) nanostructures by hydrothermal methods using lotus root extract. The different volumes of lotus root extract were tested on NiO nanostructures (sample 1, sample 2) using 1 ml and 2 ml amounts of the extract, respectively. Therefore, phytochemicals from lotus extract have influenced the surface morphology, crystal quality, optical band gap, electrical conductivity, and surface active sites of NiO nanostructures. Sample 2 of the NiO nanostructures was found to be highly active for oxygen evolution reaction (OER) and showed an overpotential of 380 mV at 10 mA cm ^−2 and a durability of 30 h at 10 mA cm ^−2 . Furthermore, sample 2 of NiO has shown specific capacitance of 1503.84 F g ^−1 at 2 A g ^−1 as well as cycling stability over a period of forty thousand GCD cycles. The percentage specific capacitance retention were highly improved up to 100.6%. An asymmetric energy storage device has been constructed using NiO sample 2 as the anode electrode material, demonstrating excellent specific capacity of about 1113 C g ^−1 at 5 A g ^−1 . For the asymmetric supercapacitor device, a power density of 20000 W kg ^−1 and an energy density of 245 Wh kg ^−1 were obtained. In a study of cycling stability for 40000 GCD cycles, it was observed that the asymmetric device retained 96.86% of its specific capacitance. A significant contribution was made to the electrochemical performance of sample 2 of NiO by phytochemicals derived from lotus extract.
