The durability and performance of fuel cells have a major impact on the most important challenges facing fuel-cell commercialization: cost, mass production, system integration, functionality and reliability. Longer-term testing with state-of-the-art LT PEMFC MEAs have shown a degradation rate over the first 1,000 h of-3.0% when fueled with simulated reformat containing 50 ppm CO and 3% air-bleed. The FC stack showed good and stable performance for at least 6,000 hours when exposed to a constant load of 0.3 A/cm~2, including >1400 operational start/stop cycles, of which 11 % where cold start-ups. However, tests also revealed that the most critical durability issues were related to BoP-component reliability to the extent that failure of one component resulted in damage to the PEM MEAs - the weakest link. Post mortem analyses of such failed MEAs and of their associated bipolar plates involved XPS, EDX, SEM and TEM. The most significant changes observed in the MEA were related to the appearance of a pronounced catalyst band within the membrane. EDX of this band showed a high Ru-content with Ru:Pt atomic ratios up to 90:10. This clearly shows that catalyst migration started from the anode side; probably a result of anode flooding leading to cell reversal.
展开▼
