Performance and durability of fuel cell cathodes with a Nafion/FEP binder

Improving the cathode durability of a proton-exchange membrane fuel cell remains a critical goal when determining the proper composition and design of a fuel cell membrane-electrode-assembly (MEA). Previous studies have shown that incorporating hydrophobic PVDF into the cathode binder enhances carbon corrosion resistance by accelerating product water removal, albeit at the cost of reduced power density. As an alternative to PVDF, the present study uses Teflon™ FEP (fluorinated ethylene propylene) and Nafion™ perfluorosulfonic acid as the cathode binder with either Pt/C or platinum group metal-free (PGM-free) catalyst powders. Sprayed Pt/C powder electrode MEAs with a cathode and anode catalyst loading of 0.1 mg/cm 2 and a cathode binder containing 30 wt% FEP exhibit a high initial power output (higher than with a neat Nafion binder) and no power loss after a carbon corrosion voltage cycling test. A binder of 50/50 wt ratio Nafion/FEP stabilizes the power output of a PGM-free cathode MEA, where the power density is twice that of the best Nafion/PVDF binder. The improved MEA performance is attributed to FEP's hydrophobic properties, its minimal impact on Nafion's proton conductivity, and the ability of a commercial FEP dispersion to minimize catalyst and binder agglomerates. • FEP added to Nafion improves the initial fuel cell power output with Pt/C catalyst. • Nafion/FEP binder stops carbon corrosion with minimal power loss for a Pt/C cathode. • FEP added to Nafion stabilizes long-term power output with a PGM-free cathode. • FEP outperforms hydrophobic PVDF, with less carbon corrosion and higher power.