Hydrogen crossover membrane degradation

Figure 1. Competing degradation mechanisms in PEM fuel cells. (CO hydrogen crossover rate ECA electrochemical area a membrane ionic conductivity.)...

Figure 10. RH cycling results in steady degradation of membrane strain-to-break, but little effect on the limiting current due to hydrogen crossover.36...

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]. 

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.)...

Galibiati et al. [147] observed gradually increased hydrogen crossover and short circuit current during continuous operation at 400 mA cm for 6000 h at 180 °C, which is an indication of membrane-related degradation. Post mortem analysis of membrane-electrode assemblies that had been operated at constant load of 200 mA cm at 150 °C, revealed considerable membrane thinning starting after about... 

As water is generated in the fuel cell reaction, dehydration is more serious at the flow field inlet. When membranes are exposed to dry conditions over a longer period, they can become brittle and develop crazes or cracks (Huang, 2006). This causes gas leakage or crossover, and then leads to the exothermic reaction of hydrogen and oxygen. Eventually, hot spots form, which will accelerate membrane degradation. Therefore, the drier the conditions, the shorter will be the life of the cell. 

In general, hydrogen crossover has a negative impact on fuel cells this includes reduced fuel efficiency, decreased fuel cell OCV [11], and accelerated degradation of the membrane and the CLs [81,83],... 

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... 

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