Synthesis and optimization of nickel and maganese dioxide nanowires and nanostructured composite thin films for potential electrochemical applications

Kong, Ying Ying (2016) Synthesis and optimization of nickel and maganese dioxide nanowires and nanostructured composite thin films for potential electrochemical applications. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

The synthesis and characterization of nickel- and manganese oxide-based nanostructures as electrode materials for the fabrication of electrochemical devices have attracted increasing attention among researchers. Among major issues that need to be addressed include morphological and microstructural optimization of nanostructures in order to enhance their electrochemical properties for the fabrication of high-performance electrochemical devices. In this study, nickel and manganese dioxide nanowires were synthesized via the wet chemical reduction approach and the water-bathing hydrothermal route, respectively. The effects of synthesis parameters such as reaction temperature, the initial concentration of precursors, pH of reaction media, and reaction time on the morphology and dimensions of both nickel and manganese nanowires formed were investigated. Through modulating these synthesis parameters, nickel nanowires with controllable morphology and manganese dioxide nanowires of tunable dimensions were successfully synthesized and characterized. Nanostructured composite thin films were subsequently prepared from mixtures of manganese dioxide nanoparticles and nanowires as well as nickel nanowires by depositing directly onto a nickel-sputtered polyethylene terephthalate (PET) supporting substrate using the binder-free drop-coating technique. The morphological characteristics and electrochemical properties of these nanostructured composite thin films were characterized by various established material characterization techniques and cyclic voltammetry, respectively. Nanostructured composite thin films with an optimal composition comprising manganese dioxide nanoparticles and nanowires, as well as nickel nanowires were observed to exhibit satisfactory capacitive behaviors in mild aqueous Na2SO4 electrolyte. Further optimization of nanostructured composite thin films is envisaged via tailored microstructure iii and enhanced electrical conductivity generated with optimal combinations of electroactive manganese nanoparticles and nanowires, as well as conductive nickel nanowires. Optimized nanostructured composite thin films should, therefore, afford high potential utility as electrode materials in the fabrication of high-performance thin-film electrochemical devices such as electrochemical capacitors and rechargeable batteries.

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