The Effect of Differential Pressure Driven Tensile Stress on Chemical Degradation of Perfluorosulfonic Acid Membranes Using a Hydrogen Peroxide Vapor Flow Cell Test

A modified ex situ H 2 O 2 vapor flow cell test has been developed to study the effect of tensile stress on the chemical degradation of perfluorosulfonic acid membranes. The test cells compose of two flowfield plates with a membrane sandwiched in between. A N 2 gas stream with higher pressure is directed through one side while a lower pressure 30% RH N 2 stream with 175 ppm of H 2 O 2 vapor flows on the other. The test offers advantages which include the ability to test as-received production membranes utilizing the residual trace iron in the membrane as catalyst to generate hydroxyl radicals, good control of H 2 O 2 concentration, and versatile control of test conditions. While applying various tensile stresses from zero to the near creep-rupture strength of Nafion ® N211, we measure the fluoride emission rates (FER) at 90 °C/30%RH of both N211 and a chemically stabilized and mechanically reinforced state-of-the-art (SOA) 12 μm membrane. The FER of N211 is 10–15 times higher than that of the SOA membrane, showing the effectiveness of using cerium for chemical mitigation. The result also shows that the tensile stress expected during fuel cell operation has insignificant effect on the membrane chemical degradation rates compared with the effect of RH.