Long-term performance of polyetheretherketone-based polymer electrolyte membrane in fuel cells at 95 °C

Abstract

A poly(styrenesulfonic acid)-grafted polyetheretherketone (ssPEEK) polymer electrolyte membrane was developed by radiation grafting of ethyl styrenesulfonate (ETSS) onto PEEK film and subsequent hydrolysis. The long-term durability of the ssPEEK electrolyte membrane was tested in a fuel cell at 95 °C, during which it exhibited a lifetime of more than 1000 h and a slow voltage degradation of 18 μV h⁻¹ at a current density of 0.3 A cm⁻². After durability test, the catalyst layers were analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM); the polymer electrolyte membrane was investigated by determining the change in thickness, proton conductivity, and amounts of sulfonic acid groups. It was concluded that the degradation of performance in fuel cell was due to the thermal aging of the hydrocarbon polymer electrolyte membrane being exposed to the electrochemical environment with the pure oxygen acting as the oxidant gas, as well as the Nafion-based catalyst layer being subjected to high temperature for a long time, where the Pt catalyst was aggregated and sintered.