Modelling of alcohol and water diffusion in fuel cell membranes—Experimental validation by means of in situ Raman spectroscopy

In this work a multi-component transport model has been set up to describe the diffusion driven mass transport of water and methanol in fuel cell membranes. For a membrane in contact with liquid methanol and water on one side and conditioned air on the other, the corresponding differential equations and boundary conditions were derived in a polymer-related coordinate system taking into account the polymers three-dimensional swelling. Phase equilibrium parameters and unknown diffusion coefficients for Nafion^® 117 were obtained by comparing the simulation results to water and methanol concentration profiles measured with confocal Raman spectroscopy. The influence of methanol concentration, temperature and air flow rate was predicted by the model with a maximum relative mean deviation between measurement and simulation of 8.6% for methanol and 3.4% for water.