Analysis of crack formation during fuel cell catalyst ink drying process. Reduction of catalyst layer cracking by addition of high boiling point solvent

Cracks in the catalyst layers of fuel cells have an adverse effect on their mechanical durability. Therefore, it is necessary to clarify the mechanism of cracking in the catalyst layer to be able to take appropriate countermeasures. A reduction in the cracks in the catalyst layer by the addition of a high boiling point solvent (propylene glycol (PG)) to the catalyst ink is examined. The relationship between the change in solvent composition and the change in dispersion of platinum-supported carbon (Pt/C) particles during the catalyst ink drying process is investigated to experimentally clarify the cause of the formation of cracks in the catalyst layer. The change in the solvent composition during the ink drying process is examined by 1H NMR. Macroscopic changes such as cracks in the catalyst layers are examined using laser microscopy. Ultra-small angle X-ray scattering measurements are performed to analyze the dispersion of Pt/C particles on the order of several hundred nanometers. The analysis of these measurements indicates that a good dispersion solvent for Pt/C particles, such as PG, remains until the end of the drying process, so that Pt/C particle agglomeration is suppressed during the drying process and crack formation in the catalyst layer is inhibited.