Mass transport measurements in membranes by means of in situ Raman spectroscopy—First results of methanol and water profiles in fuel cell membranes

In the scope of the presented work, the multi-component concentration profiles of water and methanol in Nafion®-membranes were measured. An innovative experimental set-up applying confocal micro-Raman spectroscopy was designed and constructed to investigate the mass transport of solvents in membranes, particularly for fuel cell applications. The membranes were spanned under a reservoir filled with a mixture of alcohol and water and were in contact with conditioned air on their bottom. By means of Raman spectroscopy, the solvent concentration profiles at different experimental conditions could be measured. The measured methanol concentration profiles changed with the air velocity across the membrane, the temperature and were dependent on the composition of the methanol–water mixture on top. The water concentration profiles showed a clear dependency on the air flow rate, but almost no dependency on the temperature and the composition of the methanol–water mixture.