Design of fuel cell membranes for improving interface with catalyst layers

Proton conducting ionomer membrane is one of the key materials in polymer electrolyte fuel cells. An ionomer membrane has to have high proton conductivity, durability, and compatibility with electrocatalyst layer. While a number of researches on ionomer membranes have been carried out including state-of-the-art perfluorosulfonic ionomers and sulfonated hydrocarbon polymers, studies on the interface between the ionomer membrane and the catalyst layer are insufficient. In this article, a novel copolymer (SPAF) as a combination of perfluoroalkylene and sulfonated phenylene groups is described. Since this copolymer membrane contains the characteristic properties both as fluorinated and hydrocarbon ionomer membranes, it functions well in an operating fuel cell with good compatibility with the catalyst layer. Easy synthesis and molecular design flexibility are advantages of this emerging polymer.