Rationalizing Catalyst Inks for PEMFC Electrodes Based on Colloidal Interactions

A preliminary kinetic model was developed for polymer electrolyte membrane fuel cell (PEMFC) catalyst inks in order to understand their particle stability. The Derjaguin Landau Verwey Overbeek (DLVO) model containing van der Waals attractive and electrostatic repulsive interaction energy was applied to the aqueous ink dispersions, while a modified DLVO type interaction containing a Coulombic term instead of the electrostatic term was applied to the non-aqueous dispersions. Solvents were compared based on their particle size distribution and stability ratios. Results show that the carbon black particles are stable in a higher dielectric medium whereas they tend to aggregate in a lower dielectric medium. A low ionic concentration for the aqueous medium also helped to improve the ink stability by providing a better electrostatic particle repulsion. Experiments conducted with ethyl acetate, iso-propanol and deionized water agree with the model predictions.