D214 Analysis of Oxygen Transport Properties in Recast Ionomer Thin Film

Several studies have reported that oxygen transport in ionomer in a PEFC catalyst layer (CL) is the rate determining process. To understand oxygen transport phenomena in ionomer in detail, diffusion-limited currents were measured by using the model electrode which simulates the system near platinum in CL under various film thickness, relative humidity and equivalent weight conditions, and oxygen transport properties were examined in this report. The presence of transport resistance which does not depend on the film thickness, dissolution resistance at the interface, was confirmed from results. Furthermore, it was found that dissolution process for ionomer thin film in CL is the rate determining process and oxygen diffusivity and solubility improve with an increase in the water content of ionomer.