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Structure and Dynamics Influencing Proton Transport in Materials for High Temperature (120 °C) PEM Fuel Cells

Maalouf, Manale W.

Abstract Details

2011, Doctor of Philosophy, Case Western Reserve University, Chemical Engineering.

Polymer electrolyte membranes (PEM) constitute a central part of PEM fuel cells. While acting as an electron insulator and separator of reactants, it is also highly proton conductive. A typical PEMFC operates at 80 °C and high % relative humidity (RH). For a long time, Nafion has served as the ideal membrane for this application because of its favorable mix of properties. However, with the interest in operating PEMFC at elevated temperature (120 °C), Nafion is less suitable due to its reliance on water to facilitate such activity. Therefore, novel perfluorosulfonic acid (PFSA) membranes have been developed to meet the criteria of high proton conductivity under hot and dry (H & D) conditions. Efforts at 3M resulted in new type of PFSA membranes with low equivalent weight (EW) that are more conductive under H & D conditions. For some compositions, the conductivity of 3M membranes approaches that set by DOE for automotive applications. The first part of the following study aims at understanding the interaction of these membranes with water and how it is able to retain such high conductivity under almost anhydrous conditions. Membrane water sorption behavior and thermodynamics are measured. Moreover, nuclear magnetic resonance (NMR) spectroscopy is used to probe water motion inside membranes of various EW at different length scales. These results are coupled with proton conductivity measurements to reveal that low EW 3M PFSA membrane retains high water mobility at low degrees of hydration. This is influenced by the morphology and structure of such polymers, with a high density of side chains creating a convenient environment for proton mobility even with low water content.

Also, in the quest for proton transport facilitator to replace water under H & D conditions in conventional PEM, nitrogenous compounds, mainly 4,5-Dicyano-1,2,3-triazole (DCTz), are investigated. This study attempts to answer several questions about DCTz as a proton transfer mediator. Is it thermally stable at the target temperature of 120 °C? Is it proton conductive? Does it facilitate the proton transfer relay? Thermogravimetric analysis and differential scanning calorimetry (DSC) confirm the thermal stability of DCTz up to 180 °C. FTIR ATR and NMR spectroscopic techniques employed show that DCTz participates in proton exchange process.

Thomas A. Zawodzinski, PhD (Advisor)
J. Adin Mann, PhD (Committee Chair)
Jesse S. Wainright, PhD (Committee Member)
David A. Schiraldi, PhD (Committee Member)
334 p.

Recommended Citations

Citations

  • Maalouf, M. W. (2011). Structure and Dynamics Influencing Proton Transport in Materials for High Temperature (120 °C) PEM Fuel Cells [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1311010188

    APA Style (7th edition)

  • Maalouf, Manale. Structure and Dynamics Influencing Proton Transport in Materials for High Temperature (120 °C) PEM Fuel Cells. 2011. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1311010188.

    MLA Style (8th edition)

  • Maalouf, Manale. "Structure and Dynamics Influencing Proton Transport in Materials for High Temperature (120 °C) PEM Fuel Cells." Doctoral dissertation, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1311010188

    Chicago Manual of Style (17th edition)