Quantifying key parameters to provide better understating of microstructural changes in polymer electrolyte membrane fuel cells during degradation: A startup/shutdown case study

Despite the great progress that has been made in improving the performance of polymer electrolyte membrane fuel cells (PEMFCs), they still suffer from the degradation of catalyst components. Multiple startup/shutdowns (SUSDs) of a fuel cell electric vehicle (FCEV) is one of the situations in which the catalyst and its support degradation can cause PEMFC failure. Hence, in this study, comprehensive quantification of key microstructural parameters was implemented to correlate the microstructural changes with performance data of SUSD samples. Pt loss from the cathode and particle size distribution, as well as cathode porosity and thickness changes, were quantified and discussed with respect to the electrochemical performance. The reported values indicated severe carbon corrosion and Pt degradation during an unprotected SUSD operation at 35 degrees C. Moreover, the elevation of the operating temperature to 70 degrees C exacerbated the degradation to the point that the cathode catalyst layer collapsed after a low number of cycles. After a protective protocol was implemented, microstructural and electrochemical characterization showed a significant decrease in carbon corrosion and Pt degradation. The structure-property-performance relationship confirmed and quantified the effects of unprotected SUSD opera-tion, but also showed how the protective protocol will preserve the microstructure of the PEMFC and hence improve its lifetime.

Automated summary

Despite progress in improving the performance of PEMFCs, catalyst degradation still remains a challenge. Startup/shutdowns of FCEVs can cause degradation and failure of PEMFCs. In this study, the correlation between microstructural changes and performance data of SUSD samples was quantified. Severe carbon corrosion and Pt degradation were observed during unprotected SUSD operation at 35 degrees C. However, after implementing a protective protocol, carbon corrosion and Pt degradation were significantly reduced, preserving the microstructure of the PEMFC and improving its lifetime.