Separation Analysis of Electro-Osmosis and Diffusion of Water in Electrolyte Membrane of PEMFC under Low-Humidity Operation

To alleviate performance degradation of proton exchange membrane fuel cell (PEMFC) due to membrane dehydration during low-humidity operation, it is essential to understand and control water transports through electrolyte membrane. In this study, the water vapor and current distributions on the anode side of a PEMFC was firstly measured by using the effective visualization tool proposed in our previous work, and the net water transport coefficient was quantitatively estimated under low-humidity conditions. Furthermore, the electro-osmotic drag (EOD) coefficient of Nafion membrane was also measured based on hydrogen pumping method. Therefore, the electro-osmosis and back-diffusion of water through the electrolyte membrane in the operating PEMFC can be separately analyzed. Results revealed that the cathode inlet humidification promotes the back-diffusion of water rather than the electro-osmotic flow, and prevents the membrane dryout.