(Digital Presentation) Characterization Techniques to Evaluate the Ageing of Oer Based Reversal Tolerant PEFC Anodes during Start-up/Shut-Down Events

Abstract

Anode durability is a major aspect to achieve the ambitious durability targets of low temperature polymer electrolyte fuel cells (PEFCs) for transportation and stationary applications. The introduction of oxygen evolution reaction (OER) co-catalysts has been widely established to attain reversal tolerant anode catalyst layers (ACLs).1, 2 By the introduction of OER co-catalysts, the tolerance to gross fuel starvation events can be substantially improved and the fuel cell is effectively protected from severe damage.2 OER degradation by transient anode conditions has been reported recently, originating for example from start-up/shut down (SUSD) events.3 For the present work, two SUSD accelerated stress tests (ASTs) variants were developed to provoke substantial OER co-catalyst degradation while minimizing common cathode degradation by the so-called reverse-current effect. Advanced characterization techniques were developed to investigate the OER and hydrogen oxidation reaction (HOR) catalyst degradation. The results reveal a structural change within the anode catalyst layer and a substantial loss in reversal tolerance after PEFCs have been exposed to SUSD events. Furthermore, characterization methods are presented to investigate the crossover of IrO2 based OER co-catalyst from the anode to the cathode catalyst layer, promoted by transient anode conditions during start-up/shut-down. For state-of-the-art characterization methods to investigate the electrochemical surface area (ECSA) of platinum-based catalysts, the observed Iridium crossover was found to significantly affect the ECSA results. References T. Joo, L. Hu, B. K. Hong, J.-G. Oh and S. Litster, Journal of Power Sources, 472, 228439 (2020). T. R. Ralph, M. P. Hogarth, Platinum Metals Rev., 46(3) (2002). M. Fathi Tovini, A. M. Damjanovic, H. A. El-Sayed, J. Speder, C. Eickes, J.-P. Suchsland, A. Ghielmi and H. A. Gasteiger, J. Electrochem. Soc., 168(6), 64521 (2021). Figure 1