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    Improved Fuel Cell Chemical Durability of an Heteropoly Acid Functionalized Perfluorinated Terpolymer-Perfluorosulfonic Acid Composite Membrane

    Year: 2023

    Journal: Journal of The Electrochemical Society, Volume 170, 2023-02, page 24505

    Authors: Kim, ChulOong; Wu, Ivy; Kuo, Mei-Chen; Carmosino, Dominic J.; Bloom, Ethan W.; Seifert, Soenke; Cullen, David A.; Ha, Phuc; Lindell, Matthew J.; Jiang, Ruichun; Gittleman, Craig S.; Yandrasits, Michael A.; Herring, Andrew M.

    Commercial proton exchange membrane heavy-duty fuel cell vehicles will require a five-fold increase in durability compared to current state-of-the art light-duty fuel cell vehicles. We describe a new composite membrane that incorporates silicotungstic heteroply acid (HPA), α-K8SiW11O40▪13H2O, a radical decomposition catalyst and when acid-exchanged can potentially conduct protons. The HPA was covalently bound to a terpolymer of tetrafluoroethylene, vinylidene fluoride, and sulfonyl fluoride containing monomer (1,1,2,2,3,3,4,4-octafluoro-4-((1,2,2-trifluorovinyl)oxy)butane-1-sulfonyl fluoride) by dehydrofluorination followed by addition of diethyl (4-hydroxyphenyl) phosphonate, giving a perfluorosulfonic acid-vinylidene fluoride-heteropoly acid (PFSA-VDF-HPA). A composite membrane was fabricated using a blend of the PFSA-VDF-HPA and the 800EW 3M perfluoro sulfonic acid polymer. The bottom liner-side of the membrane tended to have a higher proportion of HPA moieties compared to the air-side as gravity caused the higher mass density PFSA-VDF-HPA to settle. The composite membrane was shown to have less swelling, more hydrophobic properties, and higher crystallinity than the pure PFSA membrane. The proton conductivity of the membrane was 0.130 ± 0.03 S cm−1 at 80 °C and 95% RH. Impressively, when the membrane with HPA-rich side was facing the anode, the membrane survived more than 800 h under accelerated stress test conditions of open-circuit voltage, 90 °C and 30% RH. Heteropoly acid functionalized perfluorinated sulfonic acid - vinylidene fluoride material. Decrease in size of heteropoly acid clusters on hydration.. Composite membrane was more crystalline and hydrophobic compared to the control membrane. Chemical durability improvement with heteropoly acid-dense side of the membrane faced to anode.
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