Zea mays lea silk extract mediated synthesis of nickel oxide nanoparticles as positive electrode material for asymmetric supercabattery

We synthesized NiO nanoparticles (NPs) using a simple, cost effective, eco-friendly and sustainable green synthesis route mediated by maize (Zea mays L.) dry silk extract. Structural characterizations by X-ray diffraction (XRD) and higher resolution transmission electron microscope (HRTEM) show that the NiO NPs have a cubic (fcc) structure (space group: Fm3m) with spherical and quasi spherical NPs of average diameter of 10-20 nm. The supercabattery properties of the NiO NPs were studied using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) cycles and electrochemical impedance spectros-copy (EIS). A capacity of 54C g(-1) was obtained a scan rate of 5 mV s(-1) and capacity retention of 60% after 2000 GCD cycles. Asymmetric supercabattery devices were developed using activated carbon and NiO NPs as the negative and positive electrode respectively. The device with positive electrode to negative electrode mass ratio of 1:1 gave superior electrochemical energy storage capabilities compared to others giving a specific capacity of 29C g(-1) at a specific current of 0.25 A g(-1). Therefore, the synthesized NiO NPs obtained using Zea mays lea silk aqueous extract have potential application in electrochemical energy storage devices. (C) 2019 Elsevier B.V. All rights reserved.