Tuesday, 31 May 2022
West Ballroom B/C/D (Vancouver Convention Center)
Non-Precious metal catalyst based on earth-abundant elements such as Iron- and nitrogen-doped carbon materials have been considered the most promising alternative for platinum-based catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells. Despite the significant advancement made in improving their activity, their viability as fuel cells catalysts is still questionable due by their relatively low durability. So far, deciphering the catalysts’ degradation mechanisms properly has been hampered by their undefined active-site structure. Herein, we used a molecular model catalyst, iron-phthalocyanine (FePc), featuring Fe-N4 active sites with resemblance to those in the more active pyrolyzed Fe-N-C catalysts, and thoroughly studied their degradation mechanisms. Based on XPS and the chronoamperometric measurements, three main demetallation processes are identified. The combination of the different iron oxidation states together with the oxygen species can direct to different degradation mechanisms. The decay rates obtained in the stability measurements, can establish what is mainly causing the loss of catalytic activity. Thereby, this model can aid in understanding the degradation mechanisms of state-of-the-art Fe-N-C and other platinum group metal-free oxygen reduction reaction fuel cells’ catalysts.