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 °C, 90 °C and 100 °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 °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.