Probing Ionomer Interactions with Electrocatalyst Particles in Solution

The interaction between ionomer (ion-conducting polymer) and catalyst particles in porous electrodes of electrochemical energy-conversion devices is a critical yet poorly understood phenomenon that controls device performance. This interaction stems from the electrode precursor inks, which also governs porous-electrode morphology during formation. In this letter, we probe the origin interaction solution to unravel ionomer/particle agglomeration process. Quartz-crystal microbalance studies detail ionomer adsorption (with range charge densities) model surfaces under variety of solvent environments, isothermal-titration-calorimetry experiments extract thermodynamic binding information platinum- carbon-black nanoparticles. Results reveal conditions tested, binding to platinum similar carbon, suggesting adsorption to platinum-on-carbon inks likely dictated mostly by hydrophobic interactions with carbon surface. Furthermore, water-rich solvents (relative propanol) promote adsorption. Finally, ionomer dispersions change time, yielding dynamic interactions.