Abstract
System durability is crucial for the successful commercialization of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs). Besides conventional electrochemical cycling durability during long-term operation, the effect of operation in cold climates must also be considered. Ice formation during start up in sub-zero conditions may result in damage to the electrocatalyst layer and the polymer electrolyte membrane (PEM). Here, we conduct accelerated cold start cycling tests on prototype fuel cell stacks intended for incorporation into commercial FCEVs. The effect of this on the stack performance is evaluated, the resulting mechanical damage is investigated, and degradation mechanisms are proposed. Overall, only a small voltage drop is observed after the durability tests, only minor damage occurs in the electrocatalyst layer, and no increase in gas crossover is observed. This indicates that these prototype fuel cell stacks successfully meet the cold start durability targets for automotive applications in FCEVs.
| Original language | English |
|---|---|
| Pages (from-to) | 41111-41123 |
| Number of pages | 13 |
| Journal | International Journal of Hydrogen Energy |
| Volume | 47 |
| Issue number | 97 |
| Early online date | 19 Nov 2022 |
| DOIs | |
| Publication status | Published - 15 Dec 2022 |
Funding
CV measurements were conducted to investigate any changes in the ECSA during the cold start cycling test. The results are shown in Fig. 13 (b). Before the cycling test, the ECSA was 52.2 m2 g-Pt−1, and this dropped to 45.2 m2 g-Pt−1 after the test, corresponding to an ECSA retention of 86%. As mentioned previously, the repeated cold-start processes cause damage to the cathode catalyst layers. This damage is especially associated with carbon support corrosion, leading to a decrease in ECSA (as described in Fig. 11) in addition to the typical degradation mechanisms in normal and cold operation as described in the introduction section. According to our in-house database, there is an approximately linear correlation between retention of ECSA and retention of cell voltage after durability tests [41], within the measurement range of CV, as shown in Fig. 14. According to this empirical linear relationship, the ECSA retention of 86% measured here corresponds to a cell voltage retention of 98.3%. As such, the estimated cell voltage after the cold start cycling test is 813 mV, relative to a cell voltage of 827 mV at 0.2 A cm−2 before the cycling test. This empirical prediction is very close to the experimentally determined value of 807 mV at 0.2 A cm−2 in Fig. 7 (b). These results confirm sufficient durability of the cell stacks against cold start cycling.
Keywords
- cold start cycling durability
- degradation mechanism
- fuel cell electric vehicles
- fuel cell stacks
- hydrogen crossover
- polymer electrolyte fuel cells
