Pre-Stretched Low Equivalent Weight PFSA Membranes with Improved Fuel Cell Performance

Wenjing (Angela) Zhang, Ryszard Wycisk, Daniel L. Kish, Peter N. Pintauro

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Uniaxial stretching of recast perfluorsulfonic acid (PFSA) films was used to promote desirable morphological changes for 3M Company’s 825 equivalent weight (EW) and 733 EW PFSA polymers. Stretching to a draw ratio (DR) of four was followed by a high temperature annealing step in order for the morphological changes to be permanent. For 825 EW PFSA, stretching increased the polymer crystallinity by 22.5%, with a reduction in methanol permeability and a small increase in proton conductivity. In direct methanol fuel cell tests at 60◦C with 1.0 M methanol, the power density at 0.4 V with a DR = 4 stretched 825 EW membrane (72 mW/cm2) was considerably greater than that obtained with a solution-cast membrane (28 mW/cm2) or with a commercial Nafion 117 membrane (55 mW/cm2). For 733 EW PFSA, stretching promoted the formation of ordered ionic domains leading to an increase in proton conductivity. There was also a substantial increase in the polymer’s α-transition temperature and an improvement in membrane mechanical properties after stretching. The lifetime of a stretched 733 EW PFSA membrane (DR = 4) was extended by a factor of 3.5 as compared to that of a solution-cast film in an open circuit voltage humidity cycling test at 80◦C. © 2014 The Electrochemical Society
Original languageEnglish
JournalJournal of The Electrochemical Society
Volume161
Issue number6
Pages (from-to)F770-F777
ISSN0013-4651
DOIs
Publication statusPublished - 2014

Bibliographical note

This was Paper 730 presented at the Las Vegas, Nevada, Meeting of the Society, October 10–15, 2010.

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