This thesis presents the fabrication of transparent conductive Boron-Doped CVD diamond (BDD) thin film with the appropriate processing parameters. The BDD shows the transmittance in the visible wavelength and good electrical conductivity. The depositing rate of Diamond films yields 0.37 £gm per hour with Hydrogen, Argon, Methane and oxygen as gas sources, and B(OCH3)3 was used as the doping source. Microwave plasma chemical vapor deposition (MWCVD) was performed for the BDD deposition. Also, PECVD was applied to grow diamond-like Carbon (DLC) film on silicon as substrate. Through systematical experiments, the influence of carrier gas flow rates of B(OCH3)3, the variation of ratio of Argon, and growth pressure of BDD on the transmittance in the visible light and electrical conductivity has been studied. In addition, dc bias was applied to synthesize diamond films and extend long depositing time shows the stable growth rate of diamond films. The thickness of BDD films increases and acquired more than 60% optical transmittance. BDD samples were analyzed by Raman Spectroscopy for the diamond quality, N & K Analyzer for the film thickness and optical properties. Van Der Pauw I-V Measurement and Hall Measurement were analyzed p-type diamond films carrier mobility, carrier concentration, electrical resistivity. By increasing Argon and applying negative dc bias can improve the growth rate and transmittance of diamond films. And the quality of diamond films could be improved by the coating of DLC on Si substrates. This work has achieved fabricating a transparent conducting BDD successfully.

The fabrication and characterization of boron-doped diamond microelectrodes for use in electrochemical detection coupled with capillary electrophoresis (CE-EC) is discussed. They exhibited low and stable background currents and sigmoidally shaped voltammetric curves for cysteine, cystine and Fe(CN)63-/4- . Evaluation of the CE-EC system and the electrode performance were accomplished using a 10 mM borate buffer, pH 8.8, run buffer, and a 70-cm-long fused-silica capillary (10-mm i.d.) with seven sulfur-containing amino acids (methionine, cysteine, cystine, homocysyeine, homocystine, glutathionine, glutathionine disulfide) as test analytes. Reproducible separation (elution time) and detection (peak current) of seven sulfur-containing amino acids were observed with response precisions of 5% or less.

The current treatment of water contaminated with organic compounds includes adsorption, air stripping, and advanced oxidation processes. These methods large quantities of water and require excessive energy and time. A novel treatment process of concentrating and then electrochemically oxidizing compound would be a more feasible practice. This research investigated the oxidative destruction of perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate (PFBS) and trichloroethene (TCE) at boron-doped diamond film electrodes and the adsorption of PFOS and PFBS on granular activated carbon and ion exchange resins.Experiments measuring oxidation rates of PFOS and PFBS were performed over a range in current densities and temperatures using a rotating disk electrode (RDE) reactor and a parallel plate flow-through reactor. Oxidation of PFOS was rapid and yielded sulfate, fluoride, carbon dioxide and trace levels of trifluoroacetic acid. Oxidation of PFBS was slower than that of PFOS. A comparison of the experimentally measured apparent activation energy with those calculated using Density Functional Theory (DFT) studies indicated that the most likely rate-limiting step for PFOS and PFBS oxidation was direct electron transfer. The costs for treating PFOS and PFBS solutions were compared and showed that PFOS is cheaper to degrade than PFBS.Screening studies were performed to find a viable adsorbent or ion exchange resin for concentrating PFOS or PFBS. Granular activated carbon F400 (GAC-F400) and an ion exchange resin, Amberlite IRA-458, were the best methods for adsorbing PFOS. Ionic strength experiments showed that the solubility of the compounds affected the adsorption onto solid phases. Regeneration experiments were carried out to determine the best method of recovering these compounds from the adsorbents; however, the compounds could not be effectively removed from the adsorbents using standard techniques.The electrochemical oxidation of trichloroethene (TCE) at boron-doped diamond film electrodes was studied to determine if this would be a viable degradation method for chlorinated solvents. Flow-through experiments were performed and showed TCE oxidation to be very rapid. Comparing the data from the DFT studies and the experimentally calculated apparent activation energies the mechanism for TCE oxidation was determined to be controlled by both direct electron transfer and oxidation via hydroxyl radicals.

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Several electrochemical processes are modeled at process levels and atomic scales. Processes are presented for acid generation and ion exchange media regeneration, along with corresponding process models. Transport and reaction processes in individual ion exchange beads are also modeled. Acids of mild strength (pH = ~1-2) are generated from electrolyte solutions and their strength is effectively modeled as a function of time. The regeneration of ion exchange media is also modeled, to close agreement with measurements, and the process model is reconciled with a model for solute flux from an individual ion exchange bead. Together, the models show that the "gentle" regeneration process is controlled by the plating rate. Processes interior to the particle are controlled by diffusion, but all processes are faster than the characteristic time for plating. In a separate process, an electrochemical method is used to produce hypochlorite for disinfection. The process generates perchlorate as a toxic byproduct. Density function theory is used to construct an atomic-scale model of the mechanism for producing perchlorate, as well as the aging of the boron-doped diamond anode used in the process. The mechanism shows that the boron-doped diamond surface plays an important role in chemisorbing and stabilizing radicals of oxychlorine anions, allowing the radicals to live long enough to react and form higher ions like perchlorate. Wear mechanisms that occur on the anode are shown to oxidize and etch the surface, changing its chemical functionality over time. As the surface ages, the overpotential for water oxidation is decreased, decreasing the efficiency of the electrode.

The experimental work discussed in this thesis explores the effects of metal modification on the electroanalytical ability of boron doped diamond electrodes. Boron doped diamond (BDD) electrodes have found increased application to electroanalysis in the past two decades, yet relatively little of the literature is focused on metal, nano and microparticle modification of the substrate. In this thesis three metals have been used to modify the BDD electrode; bismuth, antimony and nickel. Bismuth and antimony nanoparticle modified BDD electrodes were directly compared to unmodified BDD and a bulk bismuth electrodes in the determination of trace levels of cadmium and lead using anodic stripping voltammetry. In both instances, the modified electrode allowed for the simultaneous determination of each analyte that was otherwise unattainable at the unmodified BDD electrode. The nickel modified BDD (Ni-BDD) electrode was used in the determination of organic analytes, namely glucose, methanol, ethanol and glycerol. The nickel nano and microparticle electrodes gave the characteristic Ni(OH)₂/NiOOH redox couple in alkali pH, the oxidised form of which (NiOOH) catalysed the oxidation of the organic analytes. The chapter on glucose sensing with the Ni-BDD electrode is preceded by an extensive literature review on the advances of non-enzymatic glucose sensing, and the application of catalytic metals and nanomaterials in this field. Throughout the course of this DPhil, there has been a collaborative project between Asylum Research and myself within the Compton group to develop a commercial electrochemical atomic force microscope (EC-AFM) cell. The aim was to produce an adaptable EC-AFM cell capable of dynamic electrochemical experiments whilst simultaneously or instantaneously acquiring an AFM image of the modified surface, in-situ. This project was successful, and the EC-AFM cell has contributed to a number of chapters in this thesis, and has now been commercialised.

A couple of processes for electrosynthetic production of expendable reagents, namely acids, bases, and oxidants, from the native salt content of raw waters and industrial wastes were investigated, and the composition of mixed acids and bases made of sodium sulfate or sodium chloride salts were predicted using a model predicated on conservation principles, mass action relations, and Pitzer equations. Electrodialysis with bipolar membranes (BMED) was used to produce acids and bases in a single pass. Product concentration was limited only by the salt content of the feed water. The current efficiency for acid production was slightly higher than that for base, but neither dropped below 75%. Acid and base current utilization showed the same trends with respect to feed salt content and flow velocity, with higher efficiency at higher feed salt concentrations and flow velocities. Operating the BMED stack near the limiting current density of the bipolar membrane (BLCD) or above the limiting current density of the diluate compartment (LCD) decreased current efficiency and increased electrical power dissipation. Electrodialytic acid and base production was approximately10 times cheaper than the chemicals' f.o.b. unit costs as quoted on Alibaba.com. The mechanism and cost of on site peroxodisulfuric acid production by electrolysis of sulfuric acid solutions with boron doped diamond film anodes was investigated experimentally and with molecular dynamics (MD) and density functional theory (DFT) simulations. The cost of on site peroxodisulfate production was approximately 4 times less expensive than purchasing a 25 lb bag. It was shown that direct discharge of sulfate species produces sulfate radicals, which subsequently combined to form peroxodisulfuric acid. The likely hood of these reactions was dependent on electrode surface condition. Sulfate radicals could also be produced in solution by reaction with hydroxyl radicals generated by water discharge.

This research investigated the mechanism, kinetics and feasibility of nitrate, arsenate, and trichloroethylene inactivation on zerovalent iron (ZVI), mixed-valent iron oxides, and boron doped diamond film electrode surfaces, respectively. Nitrate ( ) is a common co-contaminant at sites remediated using permeable reactive barriers (PRBs). Therefore, understanding nitrate reactions with ZVI is important for understanding the performance of PRBs. This study investigated the reaction mechanisms of with ZVI under conditions relevant to groundwater treatment. Tafel analysis and electrochemical impedance spectroscopy were used to probe the surface reactions. Batch experiments were used to study the reaction rate of with freely corroding and cathodically protected iron wires. The removal kinetics for the air formed oxide (AFO) were 2.5 times slower than that of water formed oxide (WFO).This research also investigated the use of slowly corroding magnetite (Fe3O4) and wustite (FeO) as reactive adsorbent media for removing As(V) from potable water. Observed corrosion rates for mixed valent iron oxides were found to be 15 times slower than that of zerovalent iron under similar conditions. Electrochemical and batch and column experiments were performed to study the corrosion behavior and gain a deeper understanding on the effects of water chemistry and operating parameters, such as, empty bed contact times, influent arsenic concentrations, dissolved oxygen levels and solution pH values and other competing ions. Reaction products were analyzed by X-Ray diffraction and XPS to determine the fate of the arsenic.This research also investigated use of boron doped diamond film electrodes for reductive dechlorination of trichloroethylene (TCE). TCE reduction resulted in nearly stoichiometric production of acetate. Rates of TCE reduction were found to be independent of the electrode potential at potentials below -1 V with respect to the standard hydrogen electrode (SHE). However, at smaller overpotentials, rates of TCE reduction were dependent on the electrode potential. Short lived species analysis and density functional simulations indicate that TCE reduction may occur by formation of a surface complex between TCE and carbonyl groups present on the surface.

<p>The primary goals of this research were to investigate the electrochemical behavior of carbon nanostructures of varying morphology, identify morphological characteristics that improve electrochemical capacitance for applications in energy storage and neural stimulation, and engineer and characterize a boron-­doped diamond (BDD) electrode based electrochemical system for disinfection of human liquid waste. </p><p>Carbon nanostructures; ranging from vertically aligned multiwalled carbon nanotubes (MWCNTs), graphenated carbon nanotubes (g-­CNTs) to carbon nanosheets (CNS); were synthesized using a MPECVD system. The nanostructures were characterized by using scanning electron microscopy (SEM) and Raman spectroscopy. In addition to employing commonly used electrochemical techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), a new technique was developed to evaluate the energy and power density of individual electrodes. This facilitated comparison of a variety of electrode materials without having to first develop complex device packaging schemes. It was found that smaller pore size and higher density of carbon foliates on a three-dimensional scaffold of carbon nanotubes increased specific capacitance. A design of experiments (DOE) study was conducted to explore the parametric space of the MWCNT system. A range of carbon nanostructures of varying morphology were obtained. It was observed that the capacitance was dependent on defect density. Capacitance increased with defect density.</p><p>A BDD electrode was characterized for use in a module designed to disinfect human liquid waste as a part of a new advanced energy neutral, water and additive-free toilet designed for treating waste at the point of source. The electrode was utilized in a batch process system that generated mixed oxidants from ions present in simulated urine and inactivated E. Coli bacteria. Among the mixed oxidants, the concentration of chlorine species was measured and was found to correlate to the reduction in E. Coli concentration. Finally, a new operating mode was developed that involved pulsing the voltage applied to the BDD anode led to 66% saving in energy required for disinfection and yet successfully reduced E. Coli concentration to less than the disinfection threshold.</p> / Dissertation