Manufacture of Robust Catalyst Layers for the DMFC

摘要

Catalyst layers for fuel cells must have a complex structure in order to provide protonic and electronic conductivity as well as access of reactants at all reactive sites. This involves a highly porous structure which is often mechanically instable, especially when mass production processes are used. A feasible process should provide a catalyst layer in one coating step and must include relatively fast drying of the ink. We use different types of additives in order to provide such an ink. Inorganic particles which are much larger than the catalyst particles provide dimensional stability of the catalyst layer. Depending on their structure and surface, they can also be used to influence porosity or hydrophilicity of the layers and thus to optimise performance. Gel forming polymers are used to adjust the viscosity of the inks and as a binder they stabilize the catalyst layers. These effects can be obtained by using minimal quantities of polymers, thus avoiding problems of clogging pores or deactivating catalyst surfaces. As a result, catalyst inks can be adjusted to suit coating techniques like knife-coating or screen printing and catalyst layers are mechanically stable, thus avoiding long-term degradation due to crack formation or delamination.