Measurements of water uptake and transport properties in anion-exchange membranes

Abstract

This paper reports on the measured water uptake and water transport properties through an anion-exchange membrane, including the water diffusivity, the electro-osmotic drag (EOD) coefficient, and the mass-transfer coefficient of water at the cathode catalyst layer/membrane interface. The water uptake of the membrane in equilibrium with liquid water and water vapor at different values of relative humidity is measured at 30, 40 and 60 °C. The measured water uptake at each measured temperature is correlated in terms of the relative humidity. Like in Nafion ® membranes, the Schroeder’s paradox phenomenon is also found to exist in the anion-exchange membrane. The water diffusivity of the anion-exchange membrane shows the same order of 10 −10 m 2 s −1 as that of the Nafion ® membrane. The measured mass-transfer coefficient of water at the cathode catalyst layer/membrane interface falls in the range of 1.0 × 10 −6 to 1.0 × 10 −5 m s −1. The EOD coefficients measured at 30 °C and 40 °C are, respectively, 2.3 and 3.6.