Investigating Proton Exchange Membrane Fuel Cell Durability at Intermediate Temperatures (80 – 120 °C)

Abstract

For several applications the low operating temperature of 60-80 °C of proton exchange membrane fuel cells (PEMFCs) limit their potential use. Increasing this temperature above 100 °C would simplify the water management and increase the temperature of the produced heat which would allow for more effective cooling systems [1,2]. Further, increasing the operating temperature could potentially allow for other benefits, such as the employment of more affordable catalysts, as the reaction kinetics are enhanced at elevated temperatures. However, operating at higher temperatures can cause increased degradation on the utilized components [3].In this work we investigated how commercial proton exchange membrane electrode assemblies (MEA) aged at various temperatures when operating either using a load cycle (based on the New European Drive Cycle) or constant load. The state of health of the MEA was continuously monitored through cyclic voltammetry, electrochemical impedance spectroscopy, linear sweep voltammetry, CO-stripping measurements and polarization curves. The obtained ageing results were evaluated using a physics-based model using COMSOL to better understand what aging mechanisms were pronounced at higher operating temperatures. Finally, the aged MEA were characterized with SEM and TEM analysis.The results show that all samples underwent an ageing process and that the ageing was accelerated at higher temperatures, as can be seen in the figure . Further, the ageing was more pronounced at a higher load. The measurements showed that the main ageing is occurring at the cathode catalyst layer and a drastic reduction in the electrochemical active surface area of the catalyst was observed. The membrane properties were also altered by the ageing, and a minor reduction in the membrane conductivity was observed. Surprisingly, no significant increase in the hydrogen crossover was observed, suggesting that the elevated temperature does not cause significant pinhole formation.The results shed light on the rate and mechanisms for ageing at various temperatures and can be used to determine the cost and benefits of operating at elevated temperatures.