Membrane electrode assemblies

Abstract

Performance in solid polymer electrolyte fuel cells can be improved by varying the characteristics of the ionomer used in the electrode of a membrane electrode assembly. For instance, increasing the ionomer to catalyst ratio can allow for improved performance under drier operating conditions (e.g., when less humidified reactants or higher operating temperatures are used) or when starting up in below freezing conditions.

1. A cathode catalyst for a fuel cell comprising a catalytic material and an ionomer, wherein the ionomer is present in an amount of at least 15 weight percent. 
     
     
       2. The cathode catalyst of  claim 1  wherein the equivalent weight of the ionomer is less than about 1200. 
     
     
       3. A catalyst-coated membrane comprising the cathode catalyst of  claim 1 .