Alcohol-Soluble, Sulfonated Poly(arylene ether)s: Investigation of Hydrocarbon Ionomers for Proton Exchange Membrane Fuel Cell Catalyst Layers

Abstract

Novel sulfonated poly(arylene ether)s, characterized as being highly sterically encumbered, were synthesized for investigation as the ionomer in proton exchange membrane fuel cell (PEMFC) catalyst layers. Catalyst-coated membranes were prepared via their incorporation into alcohol-based catalyst inks, devoid of the high-boiling, polar aprotic solvents typically required for hydrocarbon-based ionomer inks. Catalyst layers thicknesses increased from 8.5 to 9.1 μm when the hydrocarbon ionomer loading was increased from 20 to 40 wt%, but resulted in a 77% loss in pore volume for fully hydrated electrodes. The catalyst layers possessed similar electrochemical surface areas and net ionic conductivity, yet catalyst layers containing 20 wt% ionomer yielded the highest overall fuel cell performance and considerably outperformed catalyst layers prepared from inks that contained high-boiling solvents.