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Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells

Sun, Che-Nan
http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477

Abstract Details

2011, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
A suite of experimental techniques have been adopted to characterize the fundamental properties of catalyst layers (CLs) and membrane materials for polymer electrolyte fuel cells (PFECs). Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) nitrogen adsorption have been conducted to investigate the microstructure including materials dispersion and porosity in CLs. We observed more ionomer in content results in a larger agglomerate size and the open pores wetted by ionomer are changing from completely to partially filled as ionomer loading varying from high to low. The increase of ionomer loading decreases the surface area and pore volume measured by nitrogen adsorption method. Water uptake isotherms of the ionomer in CLs have been created under well-controlled relative humidity (RH). The results indicate that the ionomer in CL with a higher ionomer loading can absorb more water at the given RH suggesting that the swelling behavior for the polymeric component is dependent on the structure of the ionomer. Water transport properties in CLs were measured as a function of water content through nuclear magnetic resonance (NMR) techniques at different length and time scale. We observed the water diffusion coefficient decreases more in the CLs than in the membrane at low water content. This observation is discussed with estimated tortuosity in the CLs. Moreover, thermal properties of CLs have been studied by modulated differential scanning calorimetry (MDSC) in an attempt to reveal polymer-Pt/C interactions. When compared with bulk Nafion, an exotherm feature is observed in the CLs only. Our investigation suggests that the feature is attributed to the interactions between sulfonate and functional groups on the carbon surface. Identical techniques also have been conducted on analyzing the membrane materials (3Mion) that is recently developed by 3M. 3Mion with low equivalent weight (EW) exhibits an unexpected high conductivity at low water content. Our observation suggests the water mobility in the membrane at both long and short scale is increased at low EWs and agrees with the trend for conductivity. We speculate that the water molecules can be influenced by more than one sulfonate at low EWs and therefore become more mobile.
Thomas Zawodzinski, Jr (Advisor)
Frank Ernst (Committee Chair)
Mark De Guire (Committee Member)
Pirouz Pirouz (Committee Member)
Materials Science
Nafion; ionomer; CLs; Pore

Recommended Citations

Citations

  • Sun, C.-N. (2011). Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477

    APA Style (7th edition)

  • Sun, Che-Nan. Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells. 2011. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477.

    MLA Style (8th edition)

  • Sun, Che-Nan. "Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells." Doctoral dissertation, Case Western Reserve University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477

    Chicago Manual of Style (17th edition)

case1295553477
432
© 2011, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.