Accelerated Degradation of Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers: Mass Transport Resistance and Liquid Water Accumulation at Limiting Current Density with in operando Synchrotron X-ray Radiography

An SGL 29BC gas diffusion layer (GDL) was degraded (aged) in hydrogen peroxide. The impact of ageing was measured through deviations from pristine GDLs in terms of limiting current densities, oxygen mass transport resistances, and liquid water spatial distributions in the GDL. For dry and saturated cathode conditions (oxygen concentrations of 1% and 21%, respectively) the fuel cell containing the aged GDL reached limiting current densities that were up to 10.3% lower and experienced increases in oxygen mass transport resistance of up to 11.7% versus the pristine GDL. This performance reduction was attributed to a higher liquid water content (13% more at an oxygen concentration of 21%) in the aged GDL under the channel compared to the pristine GDL. In fuel cells built with aged and pristine GDLs, up to 200% more water was present in the GDL under the land compared to under the channel at limiting current operation.