Ionic liquid as promotor to enhance the performance of oxygen reduction catalyst for fuel cell application

A secondary ionomer that enhances activity and stability of a cathode catalyst in a polymer electrolyte membrane fuel cell includes the ionic liquid, 1-methyl-2,3,4,6,7,8-hexahydro-1H-pyrimido[1,2-a]pyrimidin-9-ium 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonate ([MTBD][C.sub.4F.sub.9SO.sub.3]). When contacting the catalyst, [MTBD][C.sub.4F.sub.9SO.sub.3] enhances catalyst activity and stability more effectively than previously known ionomers, likely by preventing oxide formation and water adsorption at the catalyst surface. The disclosed secondary ionomer is thus most effective when completely coating the catalyst.