Measurement of diffusion coefficient and electro-osmotic coefficient of water at PEFC

Abstract

In order to grasp properly PEFC power generation performances, it is necessary to know data for water management, such as diffusion coefficient of water D and electro-osmotic coefficient nd of water through the membrane. In this study, we have measured D for both membrane electrode assembly (MEA) and gas diffusion layer (GDL), and nd for MEA used in our experiment by our own simple method under a wide range of relative humidity. Measured D for MEA was 1-10 × 10-3 cm2 s -1 and nd for MEA was 1.0-1.5. Comparison of our data with other published data shows that our measured data exists between the upper and lower published data. Measured D for GDL gave the approximate value of porosity divided by tortuosity of 0.21.