Influence of Ethanol Decomposition on Dispersion of PEFC Catalyst Ink

To achieve high power density operation of polymer electrolyte fuel cells (PEFCs), it is required to realize higher performance catalyst layer. Because dispersion structure of catalyst ink strongly affects the catalyst layer structure, it is crucial to understand the dispersion mechanism of PEFC catalyst ink. Though water/ethanol solution is used as solvent of the catalyst ink, decomposition of ethanol by Platinum catalyst strongly affect dispersion of the catalyst ink. In this study, influence of ethanol decomposition on dispersion of catalyst inks were investigated. Among the decomposition byproducts of ethanol, results of rheology characteristics and direct observation by scanning electron assisted dielectric microscopy clearly showed that acetaldehyde has a significant impact on aggregation of catalyst ink. To reveal the mechanism of aggregation, particle size measurement and ionomer adsorption fraction measurement of the catalyst ink were carried out. The results suggested that the acetaldehyde impede adsorption of the ionomer on Platinum catalyst.