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Ion chromatography and combustion ion chromatography were used to analyze fuel cell effluent water during open circuit voltage tests, revealing the dominant degradation mechanism of polymer chain end unzipping.

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What they did

System
MEC

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Abstract

Open circuit voltage tests were conducted on sixteen 3M Ionomer and eight Nafion™ NR211 membranes. Lifetime distributions were determined, and ion chromatography (IC) techniques were used to measure fluoride, sulfate, trifluoro acetate, and oxalate ions. Combustion Ion Chromatography (CIC) was used to determine the total organic fluoride (TOF) associated with water soluble membrane degradation fragments. The ratio of these products relative to the fluoride release rates were used to infer the likely degradation mechanism for each membrane. Peroxide attack at the sulfonic acid side chain was determined to be the least relevant reaction pathway while the long-proposed polymer chain end unzipping appears to be the dominant mechanism. Abstraction of the tertiary fluorine in the NR211 backbone and side chain is evident by organic fluoride release rates higher than can be explained by unzipping alone.

Key findings

  • Peroxide attack at the sulfonic acid side chain is the least relevant reaction pathway.
  • Abstraction of the tertiary fluorine in the NR211 backbone and side chain is evident by organic fluoride release rates higher than can be explained by unzipping alone.
  • The long-proposed polymer chain end unzipping appears to be the dominant mechanism.

Keywords

Ion chromatographyFluorideMembraneNafionSulfonic acidInorganic chemistry

Identifiers

DOI
10.1149/1945-7111/ac5d96
Journal
Journal of The Electrochemical Society
Year
2022