Application of Nano-Dispersed Ionomer to Prolong Lifetime of Polymer Electrolyte Membrane Fuel Cells

Abstract

In the late 1980s, the technique of impregnating ionomers (binders) into the electrodes of the fuel cells extended the proton transport pathway to the deep inside of the electrodes by forming lots of triple phase boundaries and also increased the durability by binding nano-sized catalysts physically. As a result of this technique, the amount of the catalyst used in the fuel cells is greatly reduced, and the performance can be greatly increased. In recent decades, catalysts for improving activity for oxygen reduction reaction (ORR) have been developed in several research groups. Although the activity of the catalysts has been remarkably improved, the catalysts do not exhibit such a high activity when it is applied to a practical fuel cells as membrane electrode assemblies (MEA) state. It has been argued that this is because the impregnated ionomer covers the surface of the catalyst and interferes with the mass transport of the gas (oxygen or etc.). Therefore, there is room for improvement in the performance of the MEA by improving the properties of conventional ionomers. In this study, we obtain an ionomer with improved properties by treating with a simple physical method, and apply it to practical fuel cells. As a result, we achieved high performance and durability, even though only the ionomer was replaced in MEA.