Title page for ETD etd-04112006-125700


Type of Document Dissertation
Author Hill, Melinda Lou
URN etd-04112006-125700
Title Polymeric and Polymer/Inorganic Composite Membranes for Proton Exchange Membrane Fuel Cells
Degree PhD
Department Macromolecular Science and Engineering
Advisory Committee
Advisor Name Title
McGrath, James E. Committee Chair
Davis, Richey M. Committee Member
Dillard, John G. Committee Member
Riffle, Judy S. Committee Member
Ward, Thomas C. Committee Member
Keywords
  • disulfonated copolymer
  • zirconium phosphate
  • poly(arylene ether sulfone)
  • polymer blend
  • proton exchange membrane
  • fuel cell
Date of Defense 2006-03-31
Availability restricted
Abstract
Several types of novel proton exchange membranes which could be used for both direct methanol fuel cells (DMFCs) and hydrogen/air fuel cells were investigated in this work. One of the main challenges for DMFC membranes is high methanol crossover. Nafion, the current perfluorosulfonic acid copolymer benchmark membrane for both DMFCs and hydrogen/air fuel cells, shows very high methanol crossover. Directly copolymerized disulfonated poly(arylene ether sulfone)s copolymers doped with zirconium phosphates and phenyl phosphonates were synthesized and showed a significant reduction in methanol permeability. These copolymer/inorganic nanocomposite hybrid membranes show lower water uptake and conductivity than Nafion and neat poly(arylene ether sulfone)s copolymers, but in some cases have similar or even slightly improved DMFC performance due to the lower methanol permeability. These membranes also show advantages for high temperature applications because of the reinforcing effect of the filler, which helps to maintain the modulus of the membrane, allowing the membrane to maintain proton conductivity even above the hydrated glass transition temperature (Tg) of the copolymer. Sulfonated zirconium phenyl phosphonate additives were also synthesized, and membranes incorporating these materials and disulfonated poly(arylene ether sulfone)s showed promising proton conductivity over a wide range of relative humidities. Single-Tg polymer blend membranes were studied, which incorporated disulfonated poly(arylene ether sulfone) with varied amounts of polybenzimidazole. The polybenzimidazole served to decrease the water uptake and methanol permeability of the membranes, resulting in promising DMFC and hydrogen/air fuel cell performance.
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