Operating Temperature Effects on Water Transport Behavior in a Single Cell PEMFC

Abstract

Flooding and membrane dehydration are phenomena that must be avoided in a proton exchange membrane fuel cell (PEMFC) operation. It needs a sufficient knowledge about water transport behaviors. Electro-osmotic drag and back diffusion are the dominant water transport mechanisms through the membrane in PEMFC. In this study, the relative humidity (RH) profile along the channel at both anode and cathode sides have been recorded. The experiment was conducted in a single cell PEMFC with single serpentine flow field design. The water content profile was strongly influenced by RH profile thus in turn influenced the electro-osmotic drag coefficient, water diffusion coefficient and back diffusion flux. The operating temperatures of cell also influence those water transport behavior. The temperature was varied at 25, 40, 50 and 60 oC, while the pressure at the anode and the cathode was fixed at 1 bar. The higher the temperature, the smaller the water contents but with higher electro-osmotic drag coefficient, water diffusion coefficient and back diffusion flux. After all, the strategy of using saturated hydrogen and dry air in this study successfully prevents flooding and membrane dehydrating in the system – that are the major problems in PEMFC operation.