Hydrogen crossover cathode degradation

Figure 11.30. Hydrogen crossover rates through a Hyflon extraded membrane under OCV tested with different reactants. Electrode area = 25 cm Pt = 0.25 mg cm at either anode or cathode T = 70 °C RH = 50% for both anode and cathode membrane thickness = 50 pm ionomer equivalent weight = 870 g equiv [26]. (Reprinted from Journal of Power Sources, 171(1), Merlo L, Ghielmi A, Cirillo L, Gebert M, Arcella V, Resistance to peroxide degradation of H3rflon Ion membranes, 140-7, 2007, with permission from Elsevier.)...

Besides affecting the proton conductivity, the temperature can also influence the hydrogen crossover of PEM fuel cell membranes. During hydrogen crossover, hydrogen diffuses across the membrane from the anode to the cathode, leading to a lower fuel cell efficiency and degradation of the... 

Nation membrane degradation is often monitored by changes in gas crossover rate or fluoride-ion emission rate (PER) during the in situ test. Often, the low humidity conditions were combined with OCV testing in order to accelerate hydrogen peroxide formation in the cathode [89, 90]. 

The first step in the chemical degradation mechanism is the production of hydrogen peroxide, which may be produced as a by-product of the oxygen reduction reaction on the cathode, or may be produced chemically by crossover of either hydrogen or oxygen to the opposite electrode. The hydrogen peroxide reacts with metal ion contaminants (M"+) acting as Fenton s catalysts to produce very reactive hydroperoxy and peroxy radicals, as described by equation (1.35) and equation (1.36). 

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