A half cell of an electrochromic (EC) device has been used to determine theelectrochromic response of a nickel oxide film in nine different electrolytes. Six of thenine electrolytes were 0.1 M non-aqueous salts dissolved in equal weight % ofpropylene carbonate and ethylene carbonate. Three of them were lithium-based andthree of them tetrabutylammonium (TBA)-based. The last three electrolytes wereproton-based aqueous solutions of 1 M KOH, 0.1 M propionic acid and 0.1 Mphosphoric acid, respectively. The electrolytes were subjected to electrochemical measurements of cyclicvoltammetry and square wave voltammetry, both with simultaneous in-situ opticaltransmittance measurements in the visible region. Ex-situ optical measurements wereperformed in the UV-VIS-NIR (300-2500 nm) range and IR-spectroscopymeasurements in the 600 – 4000 cm-1range.To determine the performance of the nickel oxide films, the coloration efficiency (CE)is used as a figure of merit. The desired value is to achieve a high optical modulationwith as little amount of charge inserted/extracted as possible.The results show that neither lithium nor TBA has a significant impact on theelectrochromic (EC) response, compared with the protonic electrolytes. Anargument can be made that the intercalation of neither cation (lithium or TBA) is thereason behind the electrochromic behaviour of the nickel oxide. In KOH it is ratherthe OH- that transfer to the surface and attracts protons (H+) from the bulk nickeloxide that enhances the EC response. In both propionic and phosphoric acid, it is thereversible intercalation of protons (H+) into the porous nickel oxide that gives theelectrochromic response.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Stephen W. Sofie. Includes bibliographical references (leaves 98-103).

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This study reports on an electrochemical capacitive properties of nickel tetraaminophthalocyanine (NiTAPc), nickel tetraaminophthalocyanine incorporated with Nickel oxide (NiTAPc-NiO) and nickel oxide incorporated with multi-walled carbon nanotubes (NiO-MWCNT), using three different techniques known as successive ionic layer adsorption reaction (SILAR), electrodeposition and dip-dry. This study also reports on the effect of undoped polymer of poly-pyrrole on NiTAPc. The physical properties of the synthesised materials were investigated using SEM and EDX and the electrochemical properties were investigated using cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). The supercapacitive properties of NiTAPc film on nickel foam showed a maximum specific capacitance of 416.0 Fg-1, a maximum power density of 15.50x103 WKg-1 and a maximum specific energy of 66.0 WhKg-1. The NiO-MWCNT film on nickel foam gave a maximum specific capacitance of 1034.0 Fg-1, a maximum power density of 10.41x103 WKg-1 and a maximum specific energy of 132.0 WhKg-1. The NiTAPc-NiOE film on nickel foam was found to possess a maximum specific capacitance of 1117.0 Fg-1, a maximum power density of 20.48x103 WKg-1 and a maximum specific energy of 119.0 WhKg-1. The NiTAPc-NiOE-S film on nickel foam gave a maximum specific capacitance of 1279.0 Fg-1, a maximum power density of 26.96x103 WKg-1 and a maximum specific energy of 114.0 WhKg-1. Finally, the NiO mixed with an oxidant (NiOS-ox) film on nickel foam gave a maximum specific capacitance of 1403.0 Fg-1, power density of 14.44x103 WKg-1 and a maximum specific energy of 147.0 WhKg<sdup>-1. In addition, the electrodes were found to be very stable even after repetitive cycling. These electrodes have clearly proved that they may be suitable for use as potential supercapacitors. Further research is necessary to fully explore their supercapacitive behaviour in single cell (2-electrode)systems. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Chemistry / unrestricted

In this study, the carbon electrode of supercapacitor was fabricated by using mesocarbon microbeads. For finding the optimal processing parameters of carbon electrode, the effects of specific surface area of activated carbon, the amount of carbon black and binder, and various electrolytes on the capacitative properties of supercapacitor are investigated. To fabricate the composite electrode of supercapacitor, NiO and WO3 thin films were deposited respectively on the carbon electrode by electron beam evaporation. The influences of various scan rates of cyclic voltammograms (CV) on the characteristic of capacitance are studied. The charge-discharge efficiency and life time of the composite electrode are also discussed. Experimental results reveal that the optimum carbon electrode can be obtained using mesocarbon microbeads with high specific surface area (2685 m2/g) and larger pore volume (0.6 cm3/g) and adding 10 wt.% carbon black and 2wt.% binder. The specific capacitances of carbon electrodes in 1 M KOH and 1 M Et4NBF4 are 230.8 F/g and 221.5 F/g, respectively. Besides, the XRD and SEM results showed that NiO and WO3 thin films on composite electrode are sheet-liked crystal structure and stone-liked amorphous structure, respectively. The composite electrode exhibits better capacitance properties than those of carbon electrode at high scan rate by CV analysis. It reveals the promotion of the capacitative property of supercapacitor at higher power density and the improving of the decay property in capacitance at high scan rate. Finally, in the test of charge-discharge efficiency and life time, the charge-discharge efficiency is near 100% after 5000 cycles and it still retains good adhesion between electrode material and substrate.

Fundamental studies on the mechanisms and kinetics of reduction of dense synthetic nickel oxide have been carried out in H2-N2 and H2-H2O mixtures. The influences of temperature, hydrogen partial pressure, and hydrogen-steam ratio on the reduction process were systematically investigated. The kinetics of the reduction process were followed metallographically by measuring the advance of the nickel product layer. The microstructures of the reduction products and their changes during heating were characterized using a high resolution scanning electron microscopy. In H2-N2 mixtures and H2-H2O mixtures with low steam content, it was found that the initial reduction rates were first order with respect to hydrogen partial pressure. In both sets of mixtures, it was found that the progress of NiO reduction was not a monotonic function of temperature. A minimum rate of advancement of NiO reduction was observed in the temperature range 700oC – 800oC depending on the hydrogen partial pressures and reduction time. A number of distinctly different nickel product microstructures, originating at the Ni-NiO interface were observed under various reduction conditions, namely coarse fibrous nickel with fissures, fine porous nickel-planar interface, large porous nickel-irregular interface and dense nickel product layer. The microstructures of reduction product were found to change with temperature and time. It was found that heating the coarse fibrous nickel structure resulted in a re-crystallization, grain growth and densification of nickel product. When the heat treatments were carried out on the porous nickel structures, the number of pores decreases with increasing temperature and time, which was accompanied by the increase in the pore sizes. The microstructures and kinetics of the reduction of nickel oxide were found to be a function of temperature, gas composition and reaction time. The study provides strong evidence for a link between the reduction kinetics and the changes in the reduction product microstructures. Mechanisms and kinetics of the reduction of nickel oxide have been discussed by considering reduction conditions, information on the structures and elementary processes involving in the reduction process.

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No presente trabalho foram preparados eletrodos formados por filmes finos de níquel e óxido de níquel sobre um substrato de Ti. Estes eletrodos foram preparados pelas metodologias de decomposição térmica de precursores poliméricos; método sol-gel e eletrodeposição com a finalidade de investigar a influência da metodologia de preparação sobre sua atividade catalítica. Foram avaliadas as variáveis relacionadas ao processo de preparação dos eletrodos como, por exemplo, a temperatura e a atmosfera de calcinação, além de diferentes métodos de eletrodeposição. A caracterização dos eletrodos foi realizada por técnicas de difração de raios-x; microscopia eletrônica de varredura e voltametria cíclica. Os resultados obtidos indicaram que as metodologias utilizadas proporcionaram a preparação de eletrodos com alta área superficial devido à formação de morfologias contendo trincas, fissuras e microrrachaduras. Por meio destas análises foi possível obter um quadro amplo do comportamento destes eletrodos. Os eletrodos preparados pelas três metodologias foram utilizados no estudo da eletrooxidação do furfural, que foi realizado através de cronopotenciometria. Os produtos foram analisados por CLAE (Cromatografia Líquida de Alta Eficiência) com intuito de analisar a eficiência dos eletrodos na eletrooxidação. Os resultados obtidos foram satisfatórios sendo que os eletrodos preparados pela metodologia de sol-gel apresentaram um maior rendimento na formação de ácido furóico. / In the present work we prepared electrodes formed by thin nickel and nickel oxide films on a Titanium substrate. These electrodes were prepared by thermal decomposition of polymeric precursors, sol-gel method and electroplating arming at investigate the influence of the preparation methodology on their catalytic activity. The parameters related to the electrodes preparation process had been investigated. These parameters included temperature and atmosphere calcinations, beyond different methods of electroplating. The electrodes characterization were carried out by x-ray diffraction, scanning electronic microscopy and cyclic voltammetry. The results indicate that the used methodologies provided the preparation of electrodes with high superficial area due to the formation of cracked and porous morphologies. he electrodes prepared by the different methodologies were used in the furfural eletrooxidation study, which was carried out by chronopotentiometry. The products were analyzed by HPLC (High Performance Liquid Chromatography) to verify the electrodes efficiency in the eletrooxidation. The obtained results had been satisfactory and the electrodes prepared by sol-gel method present a higher efficiency for furoic acid formation.