Low volatile organic compound (VOC) fuel cell inks: Effects of water content on ink microstructure and catalyst layer cracking

The dispersion medium in fuel cell catalyst ink formulations is typically a water–alcohol mixture with 20%–75% wt alcohol to enable ink processability, electrode coating uniformity, and device performance targets. However, from a manufacturing perspective, high concentrations of alcohol pose a flammability hazard that increases safety burden and capital cost by requiring the use of explosion-use proof equipment. Thus, in this study, the effect of increasing water content beyond 80% wt in catalyst inks is systematically investigated to reduce ink flammability. Increasing the ink water content in increments of 5% wt results in surprisingly dramatic variations in ink flow properties, ink microstructure, and catalyst layer cracking. We propose that the degree of cracking relates to catalyst particle packing efficiency. Despite these differences, catalyst and ionomer remain uniformly distributed throughout the catalyst layer in all formulations. Importantly, electrochemical testing shows that increasing ink water content beyond 80% wt can minimally impact device performance, demonstrating the feasibility of low VOC fuel cell electrodes for scaled manufacturing.