Dynamic Water Transport through the Perfluorinated Sulfonic-Acid Membrane

Abstract

Proton exchange membrane (PEM) is essential material for the proton transport in a polymer electrolyte fuel cell (PEFC). Since relative humidity (RH) in a cell affects the effective proton conductivity and the effective oxygen diffusivity through the catalyst layer as well as the proton conductivity, the electroosmotic drag coefficient, the effective diffusivity of water, and the gas permeances of the PEM, water behavior which determines relative humidity is important. To estimate the PEFC performance over time, the dynamic change in the moisture content of the PEM is needed to know. In this study, the PEM is considered to consist of a bulk layer and skin layers on both sides of the bulk layer. The bulk layer effective diffusion coefficient and the skin layer water transfer coefficient were formulated from the experimental results measured by the steady-state permeation method and the unsteady-state sorption and desorption method.