Analysis of Oxygen Transport Resistance Components and Water Transport Phenomena with Hydrophilic and Hydrophobic MPL in PEFC

This paper investigated the mechanism of water and oxygen transport phenomena in the vicinity of a micro-porous-layer (MPL). The influence of contact firmness between the MPL and a catalyst layer (CL) on the transport was evaluated quantitatively by analyzing oxygen transport resistance components. For the analysis, the limiting current method was extended to flooding conditions. These investigations were conducted with each of hydrophobic and hydrophilic MPLs. With low contact firmness, oxygen transport resistance inside the CL was high; there was ice layer at the MPL/CL interface, observed by the freezing method and cryo-SEM. These results suggested that the residual water at the MPL/CL interface blocks the oxygen transport and increases the oxygen transport resistance in the CL significantly. Furthermore, the analysis of oxygen transport resistance indicated that the hydrophilic MPL composed of carbon fiber has the role of draining condensed water from the CL to the MPL.