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

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

Bibliographic Details
Main Author: Sun, Che-Nan
Language:English
Published: Case Western Reserve University School of Graduate Studies / OhioLINK 2011
Subjects:
Materials Science
Nafion
ionomer
CLs
Pore
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-case12955534772021-08-03T05:33:51Z Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells Sun, Che-Nan Materials Science Nafion ionomer CLs Pore 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. 2011-03-15 English text Case Western Reserve University School of Graduate Studies / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477 http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic Materials Science
Nafion
ionomer
CLs
Pore
spellingShingle Materials Science
Nafion
ionomer
CLs
Pore
Sun, Che-Nan
Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
author Sun, Che-Nan
author_facet Sun, Che-Nan
author_sort Sun, Che-Nan
title Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
title_short Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
title_full Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
title_fullStr Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
title_full_unstemmed Study of Transport Properties and Microstructure of Materials for Polymer Electrolyte Fuel Cells
title_sort study of transport properties and microstructure of materials for polymer electrolyte fuel cells
publisher Case Western Reserve University School of Graduate Studies / OhioLINK
publishDate 2011
url http://rave.ohiolink.edu/etdc/view?acc_num=case1295553477
work_keys_str_mv AT sunchenan studyoftransportpropertiesandmicrostructureofmaterialsforpolymerelectrolytefuelcells
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