Volume 89 Issue 44 | p. 35 | Concentrates
Issue Date: October 31, 2011

Fuel-Cell Membrane Degradation

Theoretical study points to destructive role of radical species
Department: Science & Technology
News Channels: Materials SCENE, JACS In C&EN
Keywords: fuel cell, polymer-electrolyte membrane, Nafion
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One route to attacking Nafion proceeds via hydrogen radicals.
Reaction scheme showing attack on Nafion via hydrogen radicals.
 
One route to attacking Nafion proceeds via hydrogen radicals.

Degradation of Nafion, a common fluoropolymer membrane used to separate electrodes and reactants in fuel cells, involves the reaction of H2, O2, and platinum to produce radical species that then attack the intact polymer rather than defect sites, reports a group led by Caltech’s William A. Goddard III (J. Am. Chem. Soc., DOI: 10.1021/ja2074642). Understanding how Nafion degrades is key to finding ways to make fuel cells work longer. Researchers have long believed that radical species play a role in Nafion damage, but how the radicals arise and react with the polymer has been uncertain. Using a theoretical analysis, Goddard and colleagues found that HO∂ forms from H2O2 produced at the surface of Pt, which is used as a catalyst in fuel cells. The researchers then observed that HO∂ can degrade the polymer in two ways: either by attacking C–S bonds or by reacting with H2 to form H∂, which attacks C–F bonds. The results point to ways to prevent membrane damage, such as by modifying catalysts to prevent H2O2 formation or creating polymers that are more resistant to radical attack, the authors say.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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