Materials Science

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


Thumbnail image of QCM ITC Chemrxiv.pdf

Supplementary material

Thumbnail image of QCM ITC SI chemrxiv.pdf
QCM ITC SI chemrxiv