STUDY OF WATER TRANSPORT PHENOMENA IN POLYMER ELECTROLYTE FUEL CELLS IN THE THROUGH-PLANE DIRECTION

摘要

A polymer electrolyte fuel cell (PEFC) generates electricity from an electrochemical reaction. However, water accumulation in the gas diffusion layer (GDL) reduces the cell performance. Therefore, the membrane must be kept at the appropriate humidity level for proton conduction. Hence, water management in a PEFC is essential for operation, and it is important to understand the liquid water transport phenomenon in a PEFC. In this study, to clarify the water accumulation phenomenon in the GDL under PEFC operating conditions, neutron radiography was used to visualize and measure the water distribution in the through-plane direction of a small fuel cell. The experimentally and numerically determined 2D water distributions in the through-plane direction of the membrane in the PEFC were compared. The experimental results showed that water accumulation in the GDL under the land was greater than that under the channel during early PEFC operation. Water evacuation from the GDL to the channel occurred mainly around the land comers. The water saturation distributions predicted numerically were similar to the experimental results. The water accumulation rate of the experimental results was lower than that of the numerical results at the beginning of PEFC operation. This was more apparent at a lower current density of 158 mA/cm~2. The mole fraction of the vapor in the GDL under the land was higher than that under the channel, and it influenced the water accumulation in the GDL significantly.