Issue Date: October 31, 2011
Fuel-Cell Membrane Degradation
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.
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