Measurement of water content distribution in catalyst coated membranes under water permeation conditions by magnetic resonance imaging

The through-plane water content distribution in a polymer electrolyte membrane (PEM) and in catalyst coated membranes (CCMs) and the flux of water through these membranes were determined under water permeation conditions by means of magnetic resonance imaging and dew point measurements. The PEM or CCM was placed in an experimental cell and subjected to water permeation conditions with various water activities across the membrane. A comparison of the water content distribution and the water flux in the various samples showed that the PEM and CCMs have different water transport properties. These differences suggested that diffusion through the membrane and interfacial transport across the membrane–gas interface, which are the rate determining processes for water transport through the membrane, change depending on whether the membrane has a catalyst coating.