<p> Cathodic electrodeposition method has been developed for the fabrication of manganese oxide films for application in electrochemical supercapacitors (ES). The manganese oxide films prepared from KMn04 and NaMn04 aqueous solution showed an increasing deposition yield with the deposition time. The deposition rate decreases with increasing the concentration of deposition precursor. The obtained films were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), thermogravimetric and differential thermal analysis (TGA/DTA). The SEM observations revealed uniform films of highly porous nanostructure on different substrates. The capacitive behavior of the deposits was investigated by cyclic voltammetry and chronopotentiometry method in 0.1M NaS04 aqueous solutions. As prepared deposits exhibited pseudocapacitive behavior in the potential window of 0-1.0 V versus SCE with excellent cyclability. A maximum specific capacitance (SC) of 353 Fig was obtained for the 45 μg/cm2 film deposited from KMn04 solution on stainless steel foil, at a scan rate of 2 m V /s in the 0.1 M Na2S04 solution. It was found that the SC decreased with increasing deposit thickness and scan rate. No significant effect was obtained on the films prepared from 20 mM KMn04 on stainless steel after heat treatment at various temperatures. The capacitance of as-prepared electrode did not change by changing the electrolyte from Na2S04 to K2S04 solutions. However, higher capacitance values were observed by using electrolyte with higher concentration. Different structures of manganese oxides were obtained when different deposition precursors were used. No significant difference in capacitive behavior was found between the films prepared from different deposition precursor. However it was concluded that conductivity of the film is key in determining the performance of the electrodes. The effect of substrates on the electrochemical behavior has also been investigated by using stainless steel and nickel foils. </p> / Thesis / Master of Applied Science (MASc)

This dissertation explores cathodic electrodeposition mechanisms that describe the synthesis of redox-active electrode materials. Several interesting elements are known to deposit at negative potentials (e.g., Mo, Re, Se), and by extending this work, we can tailor the growth of new binary systems (e.g., MoxRe₁₋xOy, MoxSe₁₋xOy) that have enhanced optical and electronic properties. To grasp the subtleties of deposition and understand how the growth of a particular phase is influenced by other species in solution, several analytical methodologies are used to thoroughly characterize film deposition, including chronocoulometry, voltammetry, nanogravimetry, UV-Visible spectroelectrochemistry, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and inductively coupled plasma mass spectrometry (ICPMS). Chapter 1 is a general introduction that discusses the growth of redox-active metal oxides and alloys with an emphasis on tuning the composition to enhance material performance. Chapter 2 proposes a mechanistic pathway for the deposition of rhenium films from an acidic perrhenate (ReVIIO₄⁻) solution containing both metallic and oxide components. Unlike many other metal anions, it was observed that ReVIIO₄⁻ adsorbs to the electrode surface prior to reduction. As such, ReVIIO₄⁻ is ideally situated to be a redox-active mediator for other electrochemical reactions, and in Chapter 3, this dissertation explores how ReVIIO₄⁻ increases the deposition efficiency of Mo oxide deposition. Depth profiling XPS supported by electrochemical studies demonstrated that Mo and Re deposit separately to form an inhomogeneous material, MoxRe₁₋xOy (0.6 < x ≤ 1.0). Over a limited potential range from –0.3 V to –0.7 V (vs Ag/AgCl) the rhenium mole fraction increases linearly with the applied voltage. Chapter 4 explores the deposition of MoxSe₁₋xOy, and in this case, the incorporation of Mo species in solution shifts the deposition of Se⁰ to more positive potentials. Depending on the applied potential used, voltammetry experiments suggest that a small amount of Mo (<5%) reduces to the zero-valent phase to yield the photosensitive alloy, MoxSey. Chapter 5 discusses future work and presents preliminary data describing the deposition of Se⁰ on ITO using adsorbed ReVIIO₄⁻ as a redox mediator. / text

This work deals with issues of thin films, their behaviour in different enviroments and protection of theese films against unwanted degradation processes. Metal thin films are made by special physical or chemical methods in the presence of vacuum. Deposition is performed on properly cleaned substrate made of different materials, for example glass, ceramics or another metal. Theese films degrades under the influence of moisture, heat and other. There are several types of films on different bases made to prevent thin films against degradation.