Anion exchange membrane fuel cells (AEMFCs) are an alternative to proton exchange membrane fuel cells (PEMFCs) with potential benefits that include low cost (i.e., platinum-free), facile electro-kinetics, low fuel crossover, and use of CO-resistant metal catalysts. Despite these advantages, AEMFCs have not been widely used because they require more highly conductive anion exchange membranes (AEMs) that do not exhibit impaired physical properties. Therefore, the issues that this research is dealing with are to maximize conductivity and to improve chemical stability. As model materials for these studies, I synthesize a series of multiblock copolymers with which polymer structures and morphologies can be easily controlled. Chapter 2 presents the synthesis and the chemical structure determination of the multiblock copolymers. With the objective of maximizing conductivity, an understanding of the impact of structural features such as organization, size, polarity and connectivity of ionic domains and channels within AEMs on ion/water transporting properties is necessary for the targeted and predictable design of an enhanced material. Chapters 3 to 5 describe three characterization techniques that reveal the role of these structural features in the transport process. Specifically, Chapter 3 demonstrates the possibility that the NMR relaxation times of water could be an indicator of the efficiency of ion channels. Low-temperature DSC measurements differentiate the state of water (i.e., bound water and free water) inside the membranes by measuring freezing temperature drop and enthalpy. Chapter 4 demonstrates that the number of water molecules in each state correlates with conductivity and suggests a major anion-conducting mechanism for the multiblock AEM systems. In Chapter 5, the measurement of the activation energy of diffusion characterizes ion transporting behavior that occurs on the sub-nanometer scale. For the characterization of the chemical stability of the AEMs under high pH conditions, I employ automated 1H NMR measurements as a function of time as well as diffusion-ordered NMR spectroscopy (DOSY) as shown in Chapter 6. Finally, I demonstrate that new multiblock copolymers are successfully utilized as an ionomer for a hybrid cell in Chapter 7. The properties of the polymer strongly influence overall cell performance. I believe that the combination of the techniques presented in this thesis will provide insight into the ion/water transporting mechanism in a polymer ion conductor and guidance for improving conductivity and the chemical stability of the AEMs.

Denna rapport består av information och data som har samlats in i syfte att kunna presentera en genomförbar konvertering av linfärjan Toras framdrivningssystem, som idag utgörs av dieselelektrisk drift, till bränslecellsdrift. Den bränslecell som behandlas i rapporten är PEMFC och är en bränslecellstyp som drivs av ren vätgas. Resultaten tjänar som en informationskälla för en potentiell konvertering och presenteras för Trafikverket, som ett alternativ i linje med Sveriges regerings mål att reducera mängden CO2 utsläpp på en nationell nivå. Informationen i rapporten har insamlats via mail- och telefonkontakt samt ett besök på Tora på plats i Stockholm. Ett genomförande av konverteringen är fullt möjligt men mer kostsamt än dieseldrift i dagsläget med avseende på höga bränsle- och inköpskostnader utav bränsleceller. Med framtidens hårdare utsläppskrav och eventuella förbud av fossila bränslen, så kanske vätgasen kan bli aktuell som bränsle, trots de höga kostnader som finns. / This report consists of the information and data collected in the purpose of presenting a viable option for a conversion from diesel-electric energy supply, to fuel cell energy supply for the propulsion of the cable ferry Tora. The fuel cell mentioned in this report is a PEMFC, which is powered by pure hydrogen. The result serves as a platform of information for a potential conversion and is presented to Trafikverket as an option that corresponds with the Swedish government’s goal of CO2 reduction on a national level. The information in this report was collected via email and telephone contact, and a visit to Tora in Stockholm. An implementation of the conversion is entirely possible but comes with a greater cost then diesel operation at the present time with regards to high fuel and purchase costs of fuel cells. With tomorrow's tougher emission requirements and possible ban on fossil fuels, then maybe hydrogen gas can be viable as fuel, despite the high cost.

This work focused on the study of three independent projects involving perovskite oxide materials and their applications as solid oxide fuel cell (SOFC) anodes and electrochemical oxygen sensors. The underlying theme is the versatility and tune-ability of the perovskite structure. Reactivity and conductivity (ionic as well as electronic) are modified to optimize performance in a specific application. The effect of Ce doping on the structure and the conductivity of BaFeO3 perovskite materials is investigated and the resulting materials are applied as oxygen sensors. The new perovskite family, Ba1-xCexFeO3-δ (x=0, 0.01, 0.03, and 0.05), was prepared via a sol-gel method. Powder XRD indicates a hexagonal structure for BaFeO3 with a change to a cubic perovskite upon Cerium doping at the A site. The solubility limit of Ce at the A site was experimentally determined to be between 5-7 mol %. Bulk, electronic and ionic conductivities of BaFeO3-δ and Ba0.95Ce0.05FeO3-δ were measured in air at temperatures up to 1000˚C. Cerium doping increases the conductivity throughout the entire temperature range with a more pronounced effect at higher temperatures. At 800˚C the conductivity of Ba0.95Ce.05FeO3-δ reaches 3.3 S/cm. Pellets of Ba0.95Ce.05FeO3-δ were tested as gas sensors at 500 and 700˚C and show a linear, reproducible response to O2. Promising perovskite anodes have been tested in high sulfur fuel feeds. A series of perovskite solid oxide fuel cell (SOFC) anode materials: Sm0.95Ce0.05FeO3-δ, Sm0.95Ce0.05Fe0.97Ni0.03O3-δ and Sm0.95Ce0.05Fe0.97Co0.03O3-δ have been tested for sulfur tolerance at 500°C. The introduction of the extreme 5% H2S enhances the performance of these anodes, verified by EIS and CA experiments. Post mortem analyses indicate that the performance XII enhancement arises from the partial sulfidation of the anode, leading to the formation of FeS2, Sm3S4 and S on the perovskite surface. Testing in lower concentrations of sulfur, more common in sour fuels, 0.5% H2S, also enhances the performance of these materials. The SCF-Co anode shows promising stability and an increase in exchange current density, io, from 13.72 to 127.02 mA/cm2 when switching from H2 to 0.5% H2S/99.5% H2 fuel composition. Recovery tests performed on the SCF-Co anode conclude that the open cell voltage (OCV) and power density of these cells recover within 4 hours of H2S removal. We conclude that the formation of metal sulfide species is only partially reversible, yielding an anode material with an overall lower Rct upon switching back to pure H2. Combining their performance in sulfur containing fuels with their previously reported coke tolerance makes these perovskites especially attractive as low temperature SOFC anodes in sour fuels. A new perovskite family Ba1-xYxMoO3 (x=0-0.05) has been investigated in regards to electrical conductivity and performance as IT-SOFC anode materials for the oxidation of H2. Refinement of p-XRD spectra as well as SEM imaging conclude that the solubility limit of Y doping at the A site is 5 mol%, beyond which Y2O3 segregation occurs. The undoped BaMoO3 sample has a colossal room temperature conductivity of 2500 S/cm in dry H2. All materials maintain metallic conductivity in the temperature range of 25-1000°C with resistance increasing with Y doping. The Ba1-xYxMoO3 (x=0, 0.05) materials exhibit good performance as SOFC anode materials between 500-800°C, with Rct values at 500°C in dry H2 of 3.15 and 6.33 ohm*cm2 respectively. The catalytic performance of these perovskite anodes is directly related to electronic conductivity, as concluded from composite anode performance.

Proton exchange membrane fuel cell (PEMFC) has been considered as one of the most promising energy conversion devices for the future in automotive applications. One of the major technical challenges for the commercialization of PEMFC is the effective start-up from subzero temperatures, often referred to as “cold start”. The major problem of PEMFC cold start is that the product water freezes when the temperature inside the PEMFC is lower than the freezing point. If the catalyst layer (CL) is fully occupied by ice before the cell temperature rises above the freezing point, the electrochemical reaction may stop due to the blockage of the reaction sites. However, only a few of the previous PEMFC studies paid attention to cold start. Hence, understanding the ice formation mechanisms and optimizing the design and operational strategies for PEMFC cold start are critically important. In this research, an experimental setup for the cold start testing with simultaneous measurement of current and temperature distributions is designed and built; a one-dimensional (1D) analytical model for quick estimate of purging durations before the cold start processes is formulated; and a comprehensive three-dimensional (3D) PEMFC cold start model is developed. The unique feature of the cold start experiment is the inclusion of the simultaneous measurement of current and temperature distributions. Since most of the previous numerical models are limited to either 1D or two-dimensional (2D) or 3D but only considering a section of the entire cell due to computational requirement, the measured distribution data are critically important to better understand the PEMFC cold start characteristics. With a full set of conservation equations, the 3D model comprehensively accounts for the various transport phenomena during the cold start processes. The unique feature of this model is the inclusion of: (i) the water freezing in the membrane electrolyte and its effects on the membrane conductivity; (ii) the non-equilibrium mass transfer between the water in the ionomer and the water (vapour, liquid and ice) in the pore region of the CL; and (iii) both the water freezing and melting in the CL and gas diffusion layer (GDL). This model therefore provides the fundamental framework for the future top-down multi-dimensional multiphase modelling of PEMFC. The experimental and numerical results elaborate the ice formation mechanisms and other important transport phenomena during the PEMFC cold start processes. The effects of the various cell designs, operating conditions and external heating methods on the cold start performance are studied. Independent tests are carried out to identify and optimize the important design and operational parameters.

Proton exchange membrane fuel cells are electrochemical devices which convert the chemical energy of hydrogen into electrical energy with a high efficiency. They are compact and produce a powerful electric current relative to their size. Different from the batteries they do not need to be recharged. They operate as long as the fuel is supplied. Fuel cells, therefore, are considered as one of the most promising options to replace the conventional power generating systems in the future. In this study five PEMFCs / namely EAE1, AOY001, AOY002, AOY003 and AOY004 were manufactured with different methods and in different structures. A test station was built to make the performance tests. Performances of the PEMFCs were compared by comparing the voltage-current (V-i) diagrams obtained during the initial tests at 25 &ordm / C of fuel cell and gas humidification temperatures. AOY001 showed the best performance among all PEMFCs with a current density of 77.5 mA/cm2 at 0.5 V and it was chosen for further parametric studies where the effect of different flow rates of H2 and O2 gases, gas humidification and fuel cell temperatures on the performance were investigated. It was found that increasing fuel cell and gas humidification temperatures increased the performance. Excess flow rate of reactant gases had an adverse effect on the performance. On the other hand increasing the ratio of flow rate of oxygen to hydrogen had a positive but limited effect. AOY001 delivered a maximum current density of 183 mA/cm2 at 0.5 V. The highest power obtained was 4.75 W

In this thesis, fuel cell systems are analysed thermodynamically and electrochemically. Thermodynamic relations are applied in order to determine the change of first law and second law efficiencies of the cells, and using the electrochemical relations, the irreversibilities occuring inside the cell are investigated. Following this general analysis, two simple solid oxide fuel cell systems are examined. The first system consists of a solid oxide unit cell with external reformer. The second law efficiency calculations for the unit cell are carried out at 1273 K and 1073 K, 1 atm and 5 atm, and by assuming different conversion ratios for methane, hydrogen, and oxygen in order to investigate the effects of temperature, pressure and conversion ratios on the second law efficiency. The irreversibilities inside the cell are also calculated and graphed in order to examine their effects on the actual cell voltage and power density of the cell. Following the analysis of a solid oxide unit cell, a simple fuel cell system is modeled. Exergy balance is applied at every node and component of the system. First law and second law efficiencies, and exergy loss of the system are calculated.

<p>The direct methanol fuel cell or DMFC is emerging as a promising alternative energy source for many applications. Developed and developing countries, through research, are fast seeking a cheap and stable supply of energy for an ever-increasing number of energy-consuming portable devices. The research focus is to have DMFCs meeet this need at an affordable cost is problematic. There are means and ways of making this a reality as the DMFC is found to be complementary to secondary batteries when used as a trickle charger, full charger, or in some other hybrid fuel cell combination. The core functioning component is a catalyst containing MEA, where when pure platinum is used, carbon monoxide is the thermodynamic sink and poisons by preventing further reactions at catalytic sites decreasing the life span of the catalyst if the CO is not removed. Research has shown that the bi-functional mechanism of a platinum-ruthenium catalyst is best because methanol dehydrogenates best on platinumand water dehydrogenation is best facilitated on ruthenium. It is also evident that the addition of other metals to that of PtRu/C can make the catalyst more effective and effective and increase the life span even further. In addition to this, my research has attempted to reduce catalyst cost for DMFCs by developing a low-cost manufacturing technique for catalysts, identify potential non-noblel, less expensive metallic systems to form binary, ternary and quarternary catalysts.</p>

This century has seen a phenomenal growth in energy demands and environmental pollution, which has given rise to a worldwide awareness for the need to address these issues immediately. / This thesis focuses on the fabrication of high performance electrocatalysts applied in fuel cells and developing appropriate advanced oxidation processes for environmental remediation. It has been shown that ultrasonic irradiation is a promising method of synthesizing nanometre sized metal colloids with specific properties. Sonophotocatalysis has proved to be an effective process for the degradation of organic pollutants / The synthesis of platinum monometallic and platinum-ruthenium bimetallic nanoparticles was successfully achieved by using sonochemical irradiation. A chemical method and a hybrid method were used to reveal and understand the process of Ru(III) reduction by sonochemistry. TEM images of the Pt and PtRu monometallic/bimetallic particles indicate typical diameters of less than 10 nm. An effort was made to investigate the influence of two different methods, namely simultaneous and sequential sonochemical reduction, on the structure and formation of PtRu bimetallic nanoparticles. It has been shown that the sequential reduction method produces a relatively higher yield of core-shell nanoparticles than the simultaneous reduction method. It has been concluded that Pt nanoparticles, which are formed first, play an important role in catalysing the formation of Ru nanoparticles. / A number of methods including chemical, sonochemical and radiolytic synthesis were used to fabricate platinum and platinum-ruthenium monometallic/bimetallic nanoparticles. Furthermore, the evaluation of the electrocatalytic performance of these particles was performed by using cyclic voltammetry. Simultaneous and sequential methods for the synthesis of PtRu were adopted to investigate their influence on the electrocatalytic performance of these bimetallic nanoparticles. thas been shown that simultaneous reduction is an effective means of fabricating high performance electrocatalytic PtRu catalysts. A number of experiments with different ratios of platinum to ruthenium ions in precursor solution were carried out to study the effect of the ruthenium composition in platinum-ruthenium electrodes. It has been found that the methanol oxidation ability of platinum-ruthenium bimetallic nanoparticles can change with the alternation of ratio of Pt(II) to Ru(III) in the precursor solution. Simultaneous radiolytic reduction has the potential to fabricate higher performance electrocatalytic bimetallic nanoparticles. / Although both photo-oxidation and sono-oxidation techniques are fascinating solutions to the environmental problems at hand, the critical limit of these individual processes is their low efficiency of environmental remediation. In my project, sonolysis and photocatalysis (sonophotocatalysis) have been simultaneously employed to degrade selective organic pollutants in aqueous environments, such as methyl orange, p-chlorobenzoic acid, p-aminobenzoic acid and p-hydroxybenzoic acid. Experiments have been carried out in order to improve the efficiency of sonophotocatalytic reactions to ensure that a substantial amount of the electrical energy is utilized in degrading the organic pollutants. / Methyl orange, an azo dye, was selected as the degradation target for sonophotocatalysis. An orthogonal array analysis method was employed to clarify the correlation between the efficiencies of sonolysis, photocatalysis and sonophotocatalysis and the various operation conditions studied. Emphasis was placed on investigating the influence of pH and the ultrasound parameters on these three advanced oxidation processes. It was of interest to find that the degradation of methyl orange originates from hydroxylation and demethylation processes preceding aromatic ring-opening. / Sonophotocatalysis was also applied in the degradation of three aromatic carboxylic acids, p-chlorobenzoic acid, p-hydroxybenzoic acid and p-aminobenzoic acid. Experiments were carried out in order to get a thorough understanding of the synergy effects produced by combining the two oxidation techniques. A number of advanced analytical techniques, such as HPLC and Q-TOF MS/LC, were employed to comprehensively monitor and analyse the sonophotocatalytic degradation process. It has been found that synergistic effects of the combined system have been identified with respect to the parent organic pollutant as well as its degradation products. Additionally, products were quantitatively analysed by a kinetic simulation method in order to understand the reaction mechanism. This method also allowed us to quantify the synergy effects. It was observed that the solution pH played a key role in determining the degradation rate and controlling the direction of the degradation reaction. Based on the analytical data gathered, the sonophotocatalytic degradation pathway of the aromatic carboxylic acids was established. The experimental results suggest that the sonophotocatalytic technique is likely to lead to a complete mineralization of organic pollutants in aqueous solutions.

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (p. 93-95).

Typescript. Includes vita and abstract. Includes bibliographical references (leaves 85-91). Also available online in Scholars' Bank.