Polyphosphazene Membranes for PEMFCs

Fuel cell tests were performed at 22 °C without humidification of either the hydrogen or oxygen streams, and at 80 °C with full humidification of both gases (humidifiers were kept at 95 °C). The H2 and O2 gases were pressurized to 3 and 5 bar, 

The improved performance of the sulfonimide polyphosphazene MEA, compared with that of Nafion 117, was probably the result of the lower areal resistance of the former (the areal resistance is defined as the ratio of membrane thickness to proton conductivity). While the conductivity of the polyphosphazene membrane was approximately 60% that of Nafion 117 (at room temperature), its thickness was half that of Nafion 117. If temperature does not alter significantly the thickness to conductivity ratio, then the areal resistance of the sulfonimide MEA is estimated to be 15-20% less than that of Nafion 117. It should also be noted that there was no longterm stability analysis of the sulfonimide membranes. Such tests are critical in evaluating new membranes for fuel cells. 

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