Cross-linked poly(ether ether ketone) as a proton exchange membrane for fuel cell applications

Sulfonated poly(ether ether ketone) with pendant carboxylic acid groups was directly synthesized and used to prepare cross-linked polymer electrolyte membrane. The direct synthesis of the sulfonated polymer provided the opportunity to control the degree of sulfonation and the distribution of the sulfonic acid groups within the polymer. The pendant carboxylic acid groups were functionalized by unsaturated groups in order to produce a series of cross-linkable sulfonated poly(ether ether ketone). The cross-linking was employed to limit water uptake and improve the dimensional stability of the membrane. The obtained CSPEEK-20% membrane exhibited a high proton conductivity, a low methanol permeability and a good cell performance, suggesting that it is a promising candidate as a polymer proton exchange membrane for fuel cells operated at high temperature.