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Electrochemical analysis using mercury electrodes has been a prominent methodology since the beginning of voltammetry, however, due to its toxic nature their use is being slowly phased out in favour of environmentally friendlier alternatives. In this thesis, carbon electrodes feature heavily as a means to provide a cheaper and non-toxic approach to voltammmetric sensing. Pulse techniques have been used for the sensitive detection of commonly studied analytes, including antimony and iron. A simple fabrication of a vibrating electrode is presented by modifying a commercially available vibrating toothbrush with platinum foil as a means to enhance mass transport for electroanalytical work. Finally, pH determination at carbon electrodes is investigated. Carbon electrodes have been proposed as a simple sensor for pH determination by exploiting the pH sensitive nature of surface quinone groups intrinsic within carbon edge-plane like sites. Using this approach, both EPPG and GC electrodes are suggested as new materials for pH determination and can be used in aqueous solutions over the pH range 1.0 to 13.0, as a cheap and simple alternative to the classic glass electrode.

Fuel cell is a device that can directly convert chemical energy into electrical energy. For low-temperature fuel cells, catalysts are required. Fuel cells using Pt-based or other non-biological materials as catalysts are known as conventional fuel cells. Inspired from Nature, enzymes can be used as catalysts in fuel cells known as enzyme-based fuel cells. The conventional and enzymatic fuel cells share the same underlying electrochemical principles, while enzyme-based fuel cells have their intrinsic advantages and disadvantages due to enzyme properties. The objective of this thesis is to investigate the current/voltage/ power/stability capabilities of enzyme-based membrane-less H2 fuel cells in order to design the enzymatic fuel cells with improved performance. This thesis presents a facile, effective method for the construction of 3D porous carbon electrodes. The 3D porous carbon electrodes are constructed by compacting suitable carbon nanomaterials into discs. The 3D porous carbon electrodes, with large roughness, high specific surface area, and optimized pore size distribution, are able to increase the loading density of enzymes, that is, reaction sites per unit geometric electrode area. The high loading density of enzymes can result in the high current/power density of the enzyme-based membrane-less H2 fuel cells. Moreover, the large enzyme loading can bring about the improvement in fuel cell stability because current becomes limited by mass transport of dissolved gases rather than enzyme immobilization so that neither inactivation nor desorption of enzymes would influence the current output. Based on one type of 3D porous carbon electrodes, the maximum power density of enzyme-based membrane-less H2 fuel cells has increased to the mW•cm2 level by at least one order of magnitude and the half-life has also increased from several hours to one week. This thesis presents a method for the increase in power density otherwise limited by low cathodic currents due to meagre O2 in non-explosive H2-rich H2-air mixtures. The power density of enzyme-based membrane-less H2 fuel cells can be increased by re-proportioning cathode/anode geometric area ratio to balance the cathodic and anodic currents under such an unusual H2-air mixture. This thesis also demonstrates that the 3D porous carbon electrode can improve the apparent O2 tolerance of anodic catalysts – hydrogenases, which are very important for the fuel cell performance. The degrees of apparent O2 tolerance for both O2-tolerant and O2-sensitive [NiFe]-hydrogenases are greatly increased based on the 3D porous carbon electrodes, so that even an O2-sensitive [NiFe]-hydrogenase can be used as an anodic catalyst in the enzyme-based membrane-less H2 fuel cell under a non-explosive H2-rich H2-air mixture. This thesis presents a design of a test bed in which series and parallel connections of sandwich-like electrode stacks can be varied. The fuel cell test bed has demonstrated low-loss interconnects and efficient stack configuration. Operated under a non-explosive H2-air mixture containing only 4.6% O2 at 20 °C, the maximum volume power density of the fuel cell test bed exceeds 2 mW•cm3, capable of powering electronic gadgets, which is a good demonstration of electricity that originates from the buried active sites of enzymes and is transmitted by long-range electron hopping in accordance with Marcus theory.

The ever increasing demand of petroleum in the transport sector has led to depletion of low cost/low risk reserves, increased levels of pollution, and greenhouse gas emissions that take a heavy toll on the environment as well as the national economy. There is an urgent need to use alternative energy resources along with an efficient and affordable energy conversion system to arrest environmental degradation. Polymer electrolyte fuel cells (PEFCs) show great promise in this regard - they use hydrogen gas as a fuel that electrochemically reacts with air to produce electrical energy and water as the by product. In a fuel cell electric vehicle (FCEV), these zero tail pipe emission systems offer high efficiency and power density for medium-heavy duty and long range transportation. However, PEFC technology is currently challenged by its limited durability when subjected to harsh and adverse operating conditions and transients that arises during the normal course of vehicle operation. The hydrogen-based fuel cell power train for electric vehicles must achieve high durability while maintaining high power efficiency and fuel economy in order to equal the range and lifetime of an internal-combustion-engine vehicle. The technology also needs to meet the cost targets to make FCEVs a commercial success. In this dissertation, one of the degradation phenomena that severely impede the durability of the system has been investigated. In scenarios where the cell becomes locally starved of hydrogen fuel, “cell reversal” occurs, which causes the cell to consume itself through carbon corrosion and eventually fail. Carbon corrosion in the anode disrupts the original structure of the electrode and can cause undesirable outcomes like catalyst particle migration, aggregation, loss of structural and chemical integrity. A comprehensive study using advanced electrochemical diagnostics and high resolution 3D imaging was performed and a new understanding to extend PEFC life time and robustness, by implementing engineered materials solutions, has been achieved. This will eventually help in making fuel cell systems more efficient, durable and economically viable, in order to better harness clean energy resources.

Le travail de thèse présenté dans ce mémoire, est consacré à l'étude des nouveaux matériaux d'électrodes pour l'électrolyse de l'eau en milieu alcalin. L'objectif de ces études est de développer de nouveaux électrocatalyseurs à base de métaux non nobles, capables d'améliorer les cinétiques de réactions intervenant dans la décomposition de l'eau : l'évolution de l'hydrogène (HER) et l'évolution de l'oxygène (OER). L'amélioration des performances catalytiques se traduit par une diminution des surtensions de réaction et donc de l'énergie nécessaire à la production de l'hydrogène. Pour cela, nous avons choisir de réaliser des électrodes à base de nanoparticules de nickel et de cobalt pour l'HER et de nanoparticules de cobaltites de cobalt, Co3O4, pour l'OER. La mise au point de plusieurs méthodes innovantes de formulation des électrodes (dépôt par électrophorèse « réactive » et électrodes composites à base liant organique fonctionnel) a permis la réduction des surtensions des réactions. Pour une densité de courant de 100 mA cm-2, une surtension cathodique de -286 mV est nécessaire avec les électrodes composites à base de nanoparticules de nickel, -238 mV pour une électrode en Co obtenue par électrophorèse et une surtension anodique 323 mV pour une électrode composite à base de nanoparticules de Co3O4. Une étude électrochimique approfondie de l'HER a été réalisée sur différentes morphologies de nanoparticules de nickel. / The PhD work, presented in this manuscript, is devoted to the study of new electrode materials for alkaline water electrolysis.The aim of this study is to develop new electrocatalysts based on non-noble metals. These catalysts are designed to improve the kinetics of the reactions involved in the water splitting: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The improvement of catalytic reaction results in the decrease of the overpotentials and therefore the saving of energy needed for hydrogen production. To do that, nickel and cobalt nanoparticles were used for HER, and Co3O4 nanoparticles for OER. The development of several innovative methods for electrode formulation (deposition by electrophoresis and composites electrodes based on a functional organic binder) reduced the overpotential reactions. For a current density of 100 mA cm-2, -286 mV of cathodic overpotential is needed for composites electrodes based on nickel nanoparticles, -238 mV for a Co-based electrode made by electrophoresis and 323 mV of anodic overpotential for a Co3O4 -based composite electrode. A detailed electrochemical study was made for HER on various morphologies of nickel nanoparticles.

O uso do hidrogênio produzido pela água como vetor energético pode ser uma das soluções encontradas para evitar emissões de poluentes por ser uma energia limpa e renovável. Produzir o hidrogênio por intermédio de uma célula eletrolítica a membrana trocadora de prótons (PEMEC) é uma alternativa vantajosa, pois a forma sólida da membrana garante uma densidade de corrente elétrica maior comparada à eletrólise alcalina convencional, além de outras vantagens, como por exemplo, a relativa facilidade para manutenção. Os estudos presentes neste trabalho partiram da configuração de uma célula a combustível a membrana trocadora de prótons (PEMFC), entretanto, os dois tipos de células necessitam de materiais e catalisadores diferentes. Testes revelaram que placas bipolares de grafite da PEMEC não podem ser usadas, tampouco as de grafite cobertas com níquel devido à forte corrosão ocorrida na região anódica. A eletrólise por uma PEMEC é possível, no entanto, a escolha de materiais para a região anódica define a confiabilidade do método. Os aços inoxidáveis da série 3XX apresentaram os melhores resultados com níveis comerciais de produção de 75 a 85 mL.cm-2.min-1 de H2 em temperatura ambiente, com potencial de -1,9 V. Fizeram-se experimentos em PEMEC de aço AISI 310 que mostraram bom desempenho, mas ocorrendo corrosões e inviabilizando a continuidade do processo após 6h de operação. Análise por espectroscopia de impedância eletroquímica (EIE) na PEMEC desse aço foi feita para se estudar o aumento resistivo dos componentes da célula ao longo de uma sequência de eventos em um processo corrosivo do ânodo. / The use of hydrogen produced by water as energy vector can be one of the solutions to prevent emissions of pollutants because it is a clean and renewable energy. To produce hydrogen through a proton exchange membrane electrolytic cell (PEMEC) is an advantageous alternative, because the membrane as a solid structure ensures a higher electrical current density compared to conventional alkaline electrolysis, among other advantages, such as a relative ease of maintenance. The studies in this work started from the configuration of a proton exchange membrane fuel cell (PEMFC), however, both cell types require different materials and catalysts. Tests revealed that graphite bipolar plates cannot be used in PEMEC, either nickel coated graphite due to heavy corrosion in the anodic region. Electrolysis by a PEMEC is possible, however, the choice of materials for the anode region defines the reliability of the method. The 3XX series stainless steel showed the best results with commercial production levels from 75 to 85 mL.cm-2.min-1 H2 at room temperature, with a potential of -1.9 V. Experiments were made in PEMEC steel AISI 310 which showed good performance to produce H2, but as the corrosion occurred, the process become inadequate after 6 hours of operation. Analysis by electrochemical impedance spectroscopy (EIS) in this PEMEC with bipolar steel plates was made to study the increase of the cell components resistances along a sequence of events in a process of anode corrosion.

Este trabalho apresenta o estudo do comportamento eletroquímico de cinamatos de metila sulfenilados: o 3-feniltio-3-fenil-propenoato de metila, 2-feniltio-3-fenil-propenoato de metila, 3-fenil-3-etiltio-propenoato de metila e 2-etiltio-3-fenil-proenoato de metila. Está incluído a síntese dos substratos, a voltametria e as eletrólises preparativas, abrangendo oxidações e reduções eletroquímicas. As sínteses de três dos quatro ésteres selecionados partiram de um mesmo intermediário, o 3-fenil-propinato de metila, através de reações de Michael e radicalares com etanotiol e tiofenol. O 2-etiltio-3-fenil-propenoato de metila foi obtido a partir do ácido 2-etiltio-acético. As reduções catódicas foram feitas usando-se cela dividida, acetonitrila ou DMF anidros como solventes, mercúrio como eletrodo de trabalho, atmosfera inerte e potencial fixo. Em alguns casos foi utilizado uma mistura de acetonitrila com metanol como solvente, e também cela de compartimento único. Houve uma distinção entre os produtos obtidos das eletrólises dos cinamatos α e β-sulfenilados. Para os primeiros, predominou a saída do grupo do enxofre, formando cinamato de metla, ácidos cinâmico, éster de partida hidrogenado, ciclopentanonas e adipatos de metila acíclicos. Os outros dois α-isômeros não mostraram a mesma facilidade de quebra da ligação carbono-enxofre, levando a produtos de hidrólise, ciclopentanonas e derivados de hexanoatos que mantiveram os grupos sulfenilados As oxidações anódicas foram feitas em celas de compartimento único e separados, usando platina como eletrodo de trabalho, atmosfera inerte e corrente controlada. A maior parte dos experimentos ocorreu em meio reacional prótico (acetonitrila/metanol), fornecendo ésteres di e trimetoxilados, α e β-ésteres e tioacetais (com etiltio e feniltio) / This work presents the studing of electrochemical behavior of sulfenyl cinnamates: the 3-phenyl-3-phenylthio-propenoic methyl ester, 2-phenyl-3-phenyl-propenoic methyl-ester, 3-phenyl-3-ethylthio-propenoic methyl ester, 2-ethylthio-3-phenyl-propenoic methyl ester. The overall plane includes the synthesis of substrates, the cyclic voltammetry and the preparative eletrolysis, enclosing the reductions and oxidations. The synthesis of the three among the four chosen esters came from the same compound, the 3-phenyl-propenoic methyl ester, by Michael and radicals reactions with ethanethyol and thiophenol. The 2-ethylthio-propenoic methyl ester was achieved from the 2-ethylthio-acetic acid. The cathodic reductions werw carried out in divided glass cells, dry acetonitrile or DMF as solvents, mercury as work electrode, inert atmosphere and controlled potential. In some cases, was used a mixture of acetonitrile and methanol and only one experiment was performed in undivided cell. The products formed in β and α-sulfenyl substrates were not equal, because to the first the main role was the cleavage of the sulfur-carbon bond, giving methyl cinnamate ester, cinnamic acid, starting materials hydrogenateds, cyclopentanone and adipates derivatives. The others two isomers not exhibit the loss of sulfur group, forming hydrolisis products, cyclopentanones and hexanoates derivatives what keeping the sulfenyl groups. The anodic oxidations was carried out in divided and undivided glass cells, with platine as work electrode, inert atmosphere and controlled current Most of the electrochemicals reactions were run in protic reactional middle (acetonitrile/methanol), to furhter di and trimethoxylateds esters, β-keto-esters and thioketals (both ethyl and phenylthio).

This study gives the details about several experiments done in Eugene Mallove Laboratory for New Energy Research. Three experiments are presented and discussed in detail with different type of microscopes and mass spectrometry techniques. Also inspired by work done by Rolison and O'Grady [1], the other part of this study presents the variation of isotopic abundance after experiments on palladium cathode immersed in a heavy water electrolyte. This original inspiring paper has been published through proceedings of the first edition of International Conference on Cold Fusion held in Washington D.C. in 1989. In other words, both works provides similar evidence of an isotopic variation before and after low energy nuclear experiments. By measuring the variation in isotopic concentration, before and after electrolysis, these measurements provide insight for how the low energy nuclear phenomenon occurs. Scanning electron microscopes are used in the first part to provide high resolution, high magnification images of the electrodes. They show the morphology the topology of the cathode after experiment. An energy dispersive mass spectrometer is used to provide elemental composition of the cathode and provide a second independent measurement of elemental composition of the cathode. The presented isotopic measurements are made with a secondary ion mass spectrometer. [1]: D. Rolison & W. O'Grady - Mass/Charge Anomalies in Pd after electrochemical loading with deuterium - Section 10 in Proceedings: EPRI-NSF Workshop on Anomalous Effects in Deuterided Metals - (October 16-18, 1989) Washington, D.C.

<p>The current work focuses on the synthesis and characterization of nano-devices with potential application in alkaline electrolysis and secondary polymer lithium ion batteries.</p>

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1940. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed March 9, 2010) Includes bibliographical references (p. 45-46) and index (p. 47-52).