Description:
<jats:p> The establishment of a fully renewable energy system is predicated on the use of hydrogen as a fuel. Polymer electrolyte membrane (PEM-) water electrolyzers for its generation and (PEM-) fuel cells for its reconversion will be essential components of such a system. In order for this to be economically feasible, however, their costs have to be reduced. The quantity of expensive materials utilized for the construction of cells, including platinum, iridium or titanium must be reduced and overall efficiency increased. The efficiency of these devices is a function of the electrochemical processes that take place in the electrodes and is inseparably tied to their structure. The structure can be affected by controlling various steps in the manufacturing progress. Aside from the chemical composition of the wet coat (consisting of the supported catalyst, Nafion<jats:sup>®</jats:sup>, solvents and additives) the drying plays a significant role during the self-organization progress in the catalyst layer. Therefore, the drying aspect is one of the main focuses of interest. </jats:p>
<jats:p>Nowadays the most commonly used catalyst-containing dispersions in the manufacturing of membrane electrode assemblies (MEAs) are based on a mixture of organic solvents. In order to clarify the drying process a test rig was constructed. By using a gas phase infrared spectrometer the drying can be monitored by analyzing the waste gas. The set up enables a wide range of conditions in terms of the temperature and the type of drying gas and its preloading. Furthermore, the contact time between the drying gases with the coated layer is adjustable. </jats:p>
<jats:p>As various substances differ in their boiling points a different drying rate is observed for each organic component inside the electrode layer. Consequently, the physical and chemical parameters of the solvent mixture which evaporates during the drying step change dramatically over time. The test rig gives time-resolved information about the selectivity of drying, and the drying rates of the single mixture components in general. The measurement system provides accurate and consistent results. The low measurement uncertainty (< 2% rel.) offers an ideal tool for observing slight modifications during the drying progress. </jats:p>