Electrodes for fuel cells with modern, nanostructured electrocatalysts are being developed under the coordination of ZSW in the German-French research project BRIDGE*, funded by the German Federal Ministry of Education and Research. The goal is to combine high activity and excellent mass transport properties with minimal precious metal requirements.
ZSW’s task is to optimise the performance characteristics of membrane electrode assemblies (MEAs) at high current densities by reducing mass transport losses in the catalyst layer. One approach is to optimise the catalyst ink employed in electrode production. This primarily consists of a dispersion of the catalyst powder and a proton-conducting polymer (ionomer) in a mixture of alcohol and water. The impact of the alcohol content and the type of alcohol on the size of the ionomer particles in the dispersion was investigated in a first series of experiments.
The figure above shows the strong dependence of the particle size in the ionomer dispersion on the concentration and type of alcohol in the dispersant. Furthermore, cathode catalyst inks of varying compositions were applied to electrolyte membranes using an ultrasonic nozzle. The figure below shows the resulting current-voltage curves and how the type of alcohol has a pronounced influence on the voltage at high current densities, where oxygen mass transport becomes the power-limiting factor.
* BRIDGE = Bridging the environmental Gap: promising catalyst materials to performant fuel cells Electrode.