Ion transport characteristics of fuel cell membranes.
Item
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Title
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Ion transport characteristics of fuel cell membranes.
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Identifier
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AAI9820593
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identifier
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9820593
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Creator
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Wu, Yaobang.
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Contributor
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Advisers: Steve G. Greenbaum | Thomas A. Zawodzinski, Jr
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Date
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1998
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Chemical | Energy
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Abstract
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Perfluorosulfonic Acid (PFSA) membranes are the most important polymer electrolytes for polymer electrolyte fuel cells (PEFCs) application. In this thesis, experimental studies of the transport properties of the PFSA membranes under various conditions have been carried out. Water uptake into the membranes at 30{dollar}\sp\circ{dollar}C and 80{dollar}\sp\circ{dollar}C was determined. Protonic conductivity of the membranes for immersed and partially hydrated samples at elevated temperatures was measured using an AC impedance method. Activation energies extracted from the conductivity temperature dependence suggested that there are two distinct proton transport mechanisms, depending on H{dollar}\sb2{dollar}O content. A low water content, diffusional motion of {dollar}\rm H\sb3O\sp+{dollar} molecules is the dominant proton transport mechanism, while the proton hopping mechanism is more significant at high water content. Electro-osmotic drag coefficients for the partially hydrated membranes at 80{dollar}\sp\circ{dollar}C were measured using a concentration cell. The drag coefficients is similar for several membrane samples over a quite wide range of water content. {dollar}\sp1{dollar}H, {dollar}\sp2{dollar}H and {dollar}\sp{19}{dollar}F NMR relaxation measurements were carried out at various pressures (up to 0.25 GPa) for several membranes with various water contents. The water diffusion coefficients in the membranes at elevated temperatures was measured by means of NMR pulsed-field gradient spin-echo method. Some transport parameters for the membranes in contact with methanol/water mixtures were determined. One of the main results is that both water and methanol diffusion coefficients in the membranes are practically the same over a wide methanol concentration (1m-16m).
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
