(609c) Nafion-Based Anion Exchange Membranes for the Alkaline Fuel Cell

Polymer electrolyte membrane fuel cells (PEMFCs) are actively being explored to replace conventional power sources in automobiles and portable electronic devices. However, alkaline fuel cells (AFCs) have several key advantages over traditional PEMFCs, such as higher efficiencies at low temperatures and the ability to use non-precious metal catalysts (e.g., nickel) instead of platinum. Problems that have deterred the advancement of the AFC are electrolyte leakage (KOH(aq)) and electrode degradation due to carbonate crystal formation (due to carbon dioxide in the fuel) and adsorption onto the catalyst. Replacement of the liquid electrolyte with an anion exchange membrane (AEM) (a solid polymer film with immobile cations) has the potential to solve the current AFC problems. This would provide a fuel cell that is significantly more cost-effective than current PEMFCs. Recently, several research groups have demonstrated a working AEM-based AFC. However, there are still several scientific challenges that must be overcome to produce a high power density device with a long operational lifetime, such as poor chemical stability of the AEM under AFC conditions (high pH and >60ºC) and low hydroxyl ion conductivity of the AEM.

In this study, the synthesis of a new anion-exchange form of the Nafion membrane was demonstrated. Amination of the precursor form (perfluoroether branches terminated with ?SO2F) of Nafion was performed in contrast to the typical hydrolysis reaction, which produces the common cation-exchange form of Nafion terminated with sulfonic acid (?SO3H). Synthesis was confirmed with infrared spectroscopy and elemental analysis. The membranes were characterized with SAXS, TGA, DSC and DMA. In addition, ionic conductivities were measured using electrochemical impedance spectroscopy as a preliminary test for application in alkaline fuel cells.