(33c) Development of a Nanoporous Superacidic Proton Exchange Membrane

The performance of several types of fuel cells is limited by PEM performance, which has lead to a plethora of efforts to develop novel, high performance PEM materials. Standard materials used for such applications today are sulfonated perfluorcarbon polymers such as Nafion® whose greatest drawbacks include their poor performance at high temperatures (≳80°C) and/or when not well hydrated. Inorganic solid acids, including some nanoporous ceramic materials, have shown promise as potential proton exchange membrane materials. For this work, porous alumina membranes were coated with sulfated zircona. The resulting superacidic surface was found to enhance proton transport as measured using electrochemical impedance spectroscopy. These impedance results indicated a significantly different proton conduction mechanism from that observed in Nafion and similar polymers. The effects of coating parameters on pore size, proton conductivity, and methanol and formic acid crossover were examined. A simple membrane electrode assembly was also constructed to demonstrate the viability of this structure in a fuel cell.