Electrical properties of bipolar plate and gas diffusion layer in PEFC

Abstract

This study investigated the electrical properties of the gas diffusion layer (GDL) and the bipolar plates that are key components of a polymer electrolyte fuel cell (PEFC). Observations of the contact condition between the GDL and a bipolar plate under compression showed no noticeable increase in contact area with increasing compression pressure above a level of 0.8 MPa. Contact resistance between the GDL and an Au-coated bipolar plate decreased with increasing Au coverage. However, the decrease in contact resistance relative to Au coverage was small, less than 1 mΩ cm2, at coverage of approximately 0.6 or higher. That is presumably attributable to the flow of electrons to the Au contact spot with little voltage loss in the in-plane direction of the GDL. One reason for that is the fact that sufficient contact with the GDL was secured, as indicated by the observation results. Additionally, the in-plane resistance of the GDL was markedly smaller than the contact resistance. The change in contact resistance relative to Au coverage was calculated for GDLs having different in-plane resistivities. The results revealed that the increase in contact resistance relative to Au coverage became smaller as the resistivity of the GDL decreased.