Nafion-Flourinated Ethylene-Propylene Resin Membrane Blends for Direct Methanol Fuel Cells

A series of Nafion/Teflon-flourinated ethylene-propylene resin (FEP) membranes, in thickness with FEP, were prepared by melt processing and hot pressing. The incorporation of FEP into the membranes strongly restricted swelling of the Nafion component of the blends and methanol permeability was greatly reduced. Blended membranes containing FEP worked best in a direct methanol fuel cell that operated at with ambient pressure air. The electrochemical performance of a thick 50/50 (w/w) Nafion/FEP blend with a methanol feed was equivalent to that of Nafion 117, with a maximum power density of but with a methanol crossover 1.54 times lower than Nafion 117. At methanol, the thick blended film outperformed Nafion 117 (a maximum power density of 69 vs with lower crossover). At methanol, the maximum power density with a thick 50/50 Nafion/FEP membrane was higher than that with Nafion 117. Significant cost savings can be realized when using the blended films rather than Nafion 117 in a direct methand fuel cell. A thick membrane with FEP uses 7 times less Nafion polymer, as compared to commercial Nafion 117.