Water sorption–desorption in Nafion ® membranes at low temperature, probed by micro X-ray diffraction

• Published in: Journal of power sources Vol. 172; no. 2; pp. 587 - 596
• Main Authors: Pineri, Michel, Gebel, Gérard, Davies, Richard J., Diat, Olivier
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25-10-2007; Elsevier Sequoia
• Subjects: Applied sciences; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Glassy water; Ice crystals; Nafion ® membrane; PEMFC; PEMFC; Ice crystals; Glassy water; Nafion ® membrane; Polymer electrolytes; Membrane; Desorption; Ice; X ray diffractometry; Fuel cell; Low temperature; Nafion® membrane
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2007.05.037

Using a micro X-ray beam, the structure of a water swollen Nafion
® membrane, alone or in a membrane electrode assembly (MEA) designed for fuel cells, was studied upon cooling down to −70
°C. By scanning the membranes along their thicknesses, the water sorption–desorption process was investigated as a function of cooling/heating stages. From the scattering curves, it was deduced that the state of the water at a sub-zero temperature is glassy inside the membrane and ice crystals are observed only outside it. In the case of the MEA, this growth can be destructive since this formation is localised inside the active layers.