Nafion-flourinated ethylene-propylene resin membrane blends for direct methanol fuel cells

series of Nafion/Teflon-flourinated ethylene-propylene resin (FEP) membranes, 50-100 mu m in thickness with 20-70 wt % 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 50 wt % FEP worked best in a direct methanol fuel cell that operated at 60 S C with ambient pressure air. The electrochemical performance of a 50 mu m thick 50/ 50 (w/w) Nafion/FEP blend with a 1.0 M methanol feed was equivalent to that of Nafion 117, with a maximum power density of 96 mW/cm(2) but with a methanol crossover 1.54 times lower than Nafion 117. At 5.0 M methanol, the 50 mu m thick blended film outperformed Nafion 117 (a maximum power density of 69 vs 47 mW/cm(2) with 1.85 times lower crossover). At 10.0 M methanol, the maximum power density with a 100 mu m thick 50/50 Nafion/FEP membrane (59 mW/cm(2)) was 6.5 times 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 50 mu m thick membrane with 50 wt % FEP uses 7 times less Nafion polymer, as compared to commercial Nafion 117. (c) 2006 The Electrochemical Society.