Influence of 1-propanol/water ratio in catalyst inks for doctor-blade coated H2-PEMFC electrodes

In this study, we vary the 1-propanol/water and ionomer/carbon (I/C) ratios in catalyst inks with a high total solid content of 10 wt%. The influence of the ratios on the inks is analyzed via the processing properties, while the resulting electrodes are characterized using electrochemical hydrogen fuel cell tests. The 1-propanol/water ratio variation showed a stronger effect on the rheological and wetting properties and thus the coating qualities for low I/C inks than for high I/C inks. Different void volume fractions and electrode thicknesses are observed for the various ionomer contents and alcohol concentrations for the coated electrodes. In some cases, primarily in low I/C inks, significant differences in proton conduction and mass transport properties are observed by detailed electrochemical analysis. For some ink formulations these differences counterbalance each other, resulting in minimal net differences in the polarization curves. As a result, the interplay between ionomer concentration and alcohol content is shown to be non-straightforward and significant for optimizing the formulations of high solid weight content inks. • Low alcohol contents can result in worse proton conduction in the catalyst layer for high solid wt% content inks. • Low alcohol contents and I/C ratios can result in non-uniform coatings for high solid wt% content inks. • High alcohol contents can increase mass transport resistance at low I/Cs for high solid wt% content inks. • Varying ionomer and alcohol content can result in different electrode thicknesses and void volume fractions. • Rheological and wetting differences are more distinguishable at low I/C ratios for the different alcohol contents.