pH Matter (United States)

Hydrogen proton exchange membrane fuel cells are a key clean energy technology suited to address hard-to-abate carbon emission sources in medium- and heavy-duty transportation sectors such as trucks, rail, ships, and aviation. Researchers continue to develop novel, functionalized/modified, high-surface-area, and mesoporous carbon supported catalysts to enhance electrochemical performance and durability. However, these novel carbon supports, as well as platinum group metal-free catalysts, often require unique ink formulation methods due to differences in initial catalyst aggregate size, surface functional groups, and surface wettability. These factors affect the homogeneity of the catalyst ink, film coatings, and catalyst layer structure. As a result, determining sufficient ink mixing protocols requires trial-and-error verification. This work examines how different ink mixing strategies, such as probe sonication and low-to-high speed ball milling, affect the structure of the catalyst layer and the cell performance for an emerging functionalized high-surface-area carbon-platinum catalyst (COR-Cat-C4™ by pH Matter). A high-throughput ink drop ‘witness sample’ coating method was applied to image the catalyst structure through the mixing process and to determine the necessary duration for homogeneity. Using this approach and other characterizations, our study further evaluates the relationship between mixing intensity and the resulting aggregate size distribution. In turn, we attempt to correlate the resulting size distribution with electrode coating quality, morphology, transport properties, and fuel cell performance. The inks were characterized systematically and specific metrics have been identified for optimal coating both in terms of quality and functionality. Overall, we observe that smaller aggregates reduce free ionomer agglomerates, improve electrode film uniformity, and decrease the catalyst protonic resistance, leading to enhanced cell performance.This work was supported by the DOE Office of Energy Efficiency and Renewable Energy (EERE) under award number DE-EE0011348-001.