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Published June 15, 2013 | Supplemental Material
Journal Article Open

The effect of different environments on Nafion degradation: Quantum mechanics study


Degradation of the Nafion electrolyte in Proton Exchange Membrane Fuel Cells (PEMFCs) limits the lifetime, motivating development of materials that resist degradation. The mechanism for degradation of Nafion under fuel cell conditions remains uncertain. Studies of Nafion degradation in concentrated OH• environments, such as Fenton or vapor HOOH tests, show that the main chain significantly degrades in these conditions. However it has not been established whether this applies to fuel cell conditions. We have used quantum mechanics (Density Functional Theory with the B3LYP and M06 functionals) to determine the mechanism of Nafion degradation under both concentrated OH• and fuel cell conditions. These studies confirm that under concentrated OH• conditions Nafion degrades when peroxide radicals attack end groups (–COOH, –CF ═ CF2, –CF_2H); followed by degradation of Nafion along the polymer main chain, as proposed previously. However we find that under fuel cell conditions, Nafion degradation occurs along the polymer side chain starting with H• attacking the side chain groups such as the sulfonic acid, –SO_3^−. We find that it is easier for OH• to attack the main chain than H•, while vice versa, it is easier for H• radical to attack the side chain than OH•.

Additional Information

© 2013 Elsevier B.V. Received 19 November 2012. Received in revised form 22 February 2013. Accepted 26 February 2013. Available online 14 March 2013. This work was supported with funding from the Ford Motor Company and partially by the National Science Foundation under Grant CBET-1067848 (Program Manager: Dr. George Antos). We would like to thank Dr. Paul Resnick for fruitful discussions. The facilities of the Materials and Process Simulation Center used in this study were established with grants from DURIP-ONR, DURIP-ARO and NSF-CSEM.

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