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Mécanismes de dégradation des membranes polyaromatiques sulfonées en pile à combustible

Abstract : Fuel cell development requires an improvement in the electrode-membrane assembly durability which depends on both the polymer used and the fuel cell operating conditions. The origin of the degradation can be either electrochemical, chemical and/or mechanical.

This study deals with the understanding of alternative membranes ageing mechanisms, i.e. non fluorinated membranes, such as sPEEK and sPI. For this kind of membranes, the first process is chemical. Understanding these mechanisms is the first essential step to develop more stable structures. An original approach is developed to overcome the analytical difficulties encountered with polymers. It consists in studying the degradation mechanism on model structures. Ageings are carried out in water, with H2O2 in some cases (identified as a cause of membrane chemical ageing in the fuel cell system), and at different temperatures. The approach consists in separating the different products formed by chromatography. Then they are identified (NMR, IR, MS) and quantified. This method allows us to establish the ageing mechanism. We show that the ageing of a sPEEK structure mainly results from an attack by end chains which spreads to the whole. This mechanism is confirmed on ex-situ and in-situ aged membranes. These two kinds of ageing lead to an important decrease in polymerisation degree (determined by SEC). Formation of the same degradation products is observed. In fuel cell, a heterogeneous degradation is noticed. It takes place mainly on the cathode side.

sPI are known for their high sensitivity to hydrolysis. Nevertheless, we highlight a limited degradation at 80°C due to the recombination of hydrolysed species at this temperature.
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https://tel.archives-ouvertes.fr/tel-00145619
Contributor : Carine Perrot <>
Submitted on : Thursday, May 10, 2007 - 9:37:24 PM
Last modification on : Wednesday, November 4, 2020 - 2:06:54 PM
Long-term archiving on: : Wednesday, April 7, 2010 - 1:20:48 AM

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  • HAL Id : tel-00145619, version 1

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Carine Perrot. Mécanismes de dégradation des membranes polyaromatiques sulfonées en pile à combustible. Matériaux. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00145619⟩

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