Synthesis of nickel oxide/hydroxides and their nanocomposites with carbon materials for supercapacitor and gas sensing applications

Abstract

The goal of this thesis is to produce NiO- and Ni(OH)2-carbon based nanocomposites and explore their possible adoption as active electrode materials in supercapacitor and gas sensing applications. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and gas adsorption analyses were utilized to evaluate the structure and morphology of all samples in this study. The major aim of integrating carbon-based nanomaterials (graphene foam, graphene oxide and activated carbon) into Ni-based oxides and hydroxides in this study is to take advantage of their outstanding characteristics. These include good electrical conductivity, high corrosion resistance, large SSA, low-cost, good cyclic and temperature stability, as well as the capability to serve as a substrate for growth of other materials to form a suitable composite. The electrochemical evaluation as a potential supercapacitor electrode was employed in a three (3)-electrode configuration for the as-prepared Ni(OH)2/carbon based electrodes (NiOH)2/graphene foam and Ni(OH)2/graphene oxide electrodes) while the gas sensing characteristics of NiO/carbon-based electrodes were investigated using NCSM-CSIR gas sensing station controlled by a KEITHLEY pico-ammeter system. The electrochemical results of Ni(OH)2/carbon-based electrodes have demonstrated a superior electrochemical performance as compared to the pristine Ni(OH)2 electrodes with the results comparable and even better than some earlier related studies available in the literature. Similarly, NiO/carbonbased electrodes in the form of NiO/graphene foam and NiO/activated carbon electrodes both exhibited enhanced gas sensing properties in comparison to the pristine NiO electrode due to the increased specific surface area and electrical conductivity that are linked to its sensing response, response time and recovery time. Thus, the results obtained from these studies have clearly established the viability of these carbon-based nanomaterial composites as promising candidates for electrochemical supercapacitor and gas sensing applications.