(117b) Effect of Calcium and Sodium Deposition on a Pemfc

Even in a low temperature fuel cell such as the Proton Exchange Membrane Fuel Cell (PEMFC) contaminants from bi-polar plates, sealants, and gaskets can leach into the membrane. Here a study of two ions is presented because these ions, sodium and calcium, are present in present-day materials. This study was focused on whether the ions deposit on the sulfonic sites within the membrane electrode assembly (as would be expected through an ion-exchange mechanism) and on whether equal normality poisonings of sodium and calcium (5 mM and 2.5 mM) would produce the same percentage of performance loss.

The results confirm the hypothesis of performance loss based on ion charge. This loss for both contaminants was 45 %. However, the data show an unequal recovery after a 48 hour period of constant voltage. This recovery corresponds to 17 % degradation for sodium and 25 % for calcium. Electron microscope results illustrate cationic buildup mainly around areas of high sulfonic sites.

The higher recovery for sodium may be characteristic of a monovalent cation contaminant as compared to divalent. Additional experiments are being performed in an effort to generalize the results for all monovalent and divalent cations.