Study of Mechanical Properties of Membrane-Electrode Assemblies for Proton Exchange Membrane Fuel Cells By the Small-Punch Technique

Abstract

Mechanical properties of membrane-electrode assemblies (MEAs) for proton exchange membrane fuel cells (PEMFCs) have been studied with the small-punch technique. MEAs were operated according to a non-accelerated aging protocol, with changes in humidification and cell temperature. After operation, degradation of the MEA is reflected by a decrease in power density, increase in the internal resistance, and decrease in open circuit voltage. Small disks (8 mm diam.) were taken from different locations of the degraded MEA to test the mechanical properties by small-punch. The results show an increase in plastic deflection and a decrease in maximum load of degraded MEAs, that result in lower apparent Young modulus. The degradation is larger in the area close to oxygen outlet. SEM microscopy shows that degradation affects majorly to the fibers of the carbon cloth gas diffusion layer (GDL). Combined small-punch and SEM correlate the change in mechanical properties on aged MEA with carbon fibers degradation. Such GDL degradation must also be principal responsible for the increase in the internal resistance.