Impact of cell temperature on cathode catalyst layer oxygen transport resistance and performance ageing under heavy-duty conditions

The operating temperature of polymer electrolyte membrane fuel cells for heavy-duty transport applications is a crucial parameter for materials durability. This work focuses on cathode catalyst layer ageing of commercial membrane electrode assemblies caused by an accelerated stress test representative of real heavy-duty operation. The adopted protocol was designed with a methodology previously validated and based on real vehicles data available in literature. Degradation studies were carried out on different samples, where the cell temperature was changed between 80 degrees C, 90 degrees C and 100 degrees C, without changing the other operating conditions, including the dew point of supplied gases. Results demonstrated a complex superimposition of degradation mechanisms, including electrocatalyst ripening and support oxidation, which affected high current performance and oxygen transport resistance ageing. At 100 degrees C a minor acceleration of electrocatalyst active area loss was observed. Larger performance loss and mass transport resistance increase were observed at increasing operating temperature, indicating larger impact of carbon corrosion. A dedicated and innovative analysis on the evolution of pressure independent oxygen mass transport resistance highlighted the alteration of ionomer thin-film resistance.