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 °C. Moreover, the elevation of the operating temperature to 70 °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 operation, but also showed how the protective protocol will preserve the microstructure of the PEMFC and hence improve its lifetime. •Comprehensive microstructural characterization/quantification is executed on PEMFC.•Microstructural descriptors are related to degradation and performance in SUSD.•Microstructural degradation of unprotected SUSD was in line with performance loss.•Microstructural descriptors confirmed minor degradation in protected SUSD.