Experimental Determination of Electro-Osmotic Drag Coefficient in Nafion Membrane for Fuel Cells

Abstract

The electro-osmotic drag coefficient in Nafion 117 membrane is determined experimentally at different temperatures and water contents of the membrane. A pseudo-two-dimensional, steady-state diffusive model for water vapor transport through Nafion membrane based on nonequilibrium membrane/gas diffusion layer interface is presented to determine the electro-osmotic drag coefficient and average water content. For the membrane in contact with water vapor, the electro-osmotic drag coefficient increases with increasing water content or water activity in the membrane. At the same water activity, temperature does not show influence on the electro-osmotic drag coefficient in the membrane in contact with water vapor. For the membrane in contact with liquid water on both sides, the electro-osmotic drag coefficient in the membrane increases linearly with temperature. High-frequency resistances of the cells using Nafion 117 and 112 membranes are measured to evaluate the electro-osmotic drag coefficients obtained. The calculated membrane resistance based on a diffusive model agrees well with the experimental data under different operating conditions. (c) 2006 The Electrochemical Society.