Degradation Effects in Ion-Pair Membrane-Based High-Temperature Proton Exchange Membrane (HT-PEM) Fuel Cells

Degradation studies were conducted of two different membrane electrode assemblies (MEAs), containing identical cathode electrocatalysts (Pt/C) and dissimilar anode electrocatalysts (Pt/C; different carbon support). They were subjected to identical durability tests in a rarely reported ion-pair membrane-based high-temperature proton exchange membrane fuel cell (HT-PEMFC). To elucidate the degradation mechanisms, the fresh MEAs and the degraded MEAs (MEA1 and MEA2), that had undergone a durability test, were characterized with comprehensive chemical, structural, and morphological analyses. Platinum dissolution and Pt particle growth were identified as the major contributors to the electrocatalyst degradation by reduction of the electrochemical surface area. X-ray photoelectron spectroscopy measurements exhibit subtle changes in the chemical state of Pt and C, suggesting corrosion of support carbon and redeposition of Pt on ordered carbon during HT-PEMFC operation. Additionally, significant membrane thinning, more pronounced in MEA2 (∼70% reduction) than in MEA1 (∼50% reduction), was observed, which was accompanied by reduced thermal stability and integrity of the membrane. The interplay between carbon corrosion, Pt crystallite growth, and membrane degradation constituted a self-reinforcing degradation loop in the studied HT-PEMFC MEAs.