Load-cycling degradation

The cell has passed the dynamic load cycling aging test when the acceptance criterion is met, for example, the cell degradation (rate) is below a specified value for the applied operating conditions [12]. 

Asano, K. et al. 2008. Degradation of Pt catalyst layer in PEFCs dming load cycling under pressmized conditions. Proton Exchange Membrane Fuel Cells 8, Pts 1 and 2 16 779-785. 

Fig. 9 Load-cycling degradation as a function of upper-limit voltage...

Figure 10 shows TEM images of an MEA following an open-circuit endurance test in which was supplied to the anode and to the cathode. The test conditions were a cell temperature of 90 C, 30% relative humidity, anode atmosphere of H, and cathode atmosphere of O. Similar to the results of the load-cycling test, it was found that platinum from the cathode catalyst layer dissolved and was redeposited in the electrolyte membrane. Under these test conditions, redeposited platinum particles were observed near the center of the electrolyte membrane. The position of redeposited platinum particles is determined by a balance between the mixed potential of the electrolyte membrane and the partial pressures of the anode and cathode O. It was estimated that platinum particles would be redeposited near the center of the electrolyte membrane under the conditions used in this test (Fig. 11). Chemical degradation of the electrolyte membrane was observed centered on the band of redeposited platinum particles. An analysis was made of the drain water discharged from the MEA during the test and fluoride ions were detected, which suggests that the electrolyte manbrane was partially decomposed (Ohma et al. 2007).

Voltage manipulation also has a large effect on suppressing idling degradation, similar to the effect described earlier for load-cycling degradation. It was found that... 

Fig. 10 Load-cycling degradation as a function of upper-limit voltage. (Reproduced with permission from Ohma et al. (2007), copyright 2(X)7, The Electrochemical Society, Inc.)...

The preceding section presented an analysis of certain degradation factors (start-stop operation, load cycling, idling, and impurity contamination) specific to automotive fuel cells and discussed possible solutions. The following degradation factors are especially important for improving MEA durability ... 

The stiffness of soil at cyclic loading conditions is even more specific and very often a hysteresis loop can be found during cyclic testing (e.g. cyclic triaxial testing). Multiple loading cycles can cause degradation of the soil strength. This has... 

However, this consideration not only depends on the structure characteristics but also on the ground motion applied to the stmcture. For example, if a strong-motion earthquake causes structural collapse after a few load cycles, component degradation is of minor significance compared to a situation where a long-duration earthquake exhibits many cycles before the structure fails. 

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