Fuel cell membrane durability remains one of the key challenges limiting the wide scale adoption of fuel cell technology. Degradation in polymer electrolyte membrane (PEM) fuel cells limits the operational lifetime of the fuel cell and prevents the widescale adoption of fuel cell technology. This work contributes to characterizing the membrane structure and correlations to mechanical durability. In this study a selection of perfluorosulphonic acid (PFSA) ionomer membranes with expanded polytetrafluoroethylene (ePTFE) reinforcements were tested. The membranes differed mainly in the type of reinforcement layer and the thickness. The membranes were characterized by experiments in Nuclear Magnetic Resonance Spectroscopy, Fourier Transform Infrared Spectroscopy, Small Angle X-ray Scattering, Dynamic Mechanical Analysis and Mechanical Accelerated Stress Testing. The results showed that the greatest impact on membrane durability is the addition of a reinforcement layer, and through the addition/ changing of the reinforcement layer the mechanical strength of the membrane is influenced. The properties that had a positive correlation with increasing in situ mechanical strength were matrix domain spacing, ePTFE crystallinity, yield strength and elastic modulus. Overall, this work provides insight in designing new membranes for increased durability and longer lifetime.
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Thesis advisor: Kjeang, Erik
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