Effect of Flow Field Configuration on Oxygen Transport Resistances in Proton Exchange Membrane Fuel Cell Cathode

Abstract

Land-channel geometry is necessary for proton exchange membrane fuel cells to transport electron and at the same time to transport reactants/products. However, this configuration causes the difference in transport distance between the flow channel to the catalyst layer, and results in the non-uniform distribution of various factors, such as species concentration, current generation, and rate of degradation. In order to investigate the distributions of various parameters in the land-channel direction, a small-scale segmented cell with about 300-micron resolution was developed by the authors’ group, and successfully measured the current and high-frequency resistance distribution in the land-channel direction. Distribution of oxygen transport resistance from the flow channel to the catalyst layer was also measured using limiting current technique. The oxygen transport mechanism is completely different in the conventional flow field and in the interdigitated flow field. In the conventional flow field, the oxygen transport is mostly driven by the duffusion due to the concentration gradient. In the interdigitated flow field, on the other hand, the convective flow through gas diffusion layer (GDL) makes the diffusion distance shorter than the conventional flow field case, and therefore the lower oxygen transport resistance is expected. In this study the oxygen transport resistance distribution in land-channel direction is measured in two different flow field configurations, that is, conventional flow field and interdigitated flow field. The comparison of the results from these two flow fields reveals the impact of the convective transport through GDL on the oxygen transport resistance and on the distribution.