Impact of dispersion characteristics on ionomer thin film properties

Ion-conducting polymers (ionomers) are an important component in the heterogenous electrodes (catalyst layers) of energy conversion devices such as fuel cells and electrolyzers. Ionomer facilitates mass transport to and from the catalyst sites in the electrodes, which are fabricated through solution-based processing methods. Despite empirical evidence on the role of solvents and processing on device performance, their effect on ionomer structure-property relationships remains unexplored. This talk focuses on the impact of dispersion’s solvent composition and processing on spin-cast ionomer thin films (<100 nm), which are used as model systems for catalyst ionomers. By characterizing the ionomer both in the dispersion state and after casting into a film on various supports, insights are gained into the factors controlling the structure-property changes in ionomer thin films. Dispersion characteristics observed by pH and x-ray scattering correlated to the changes in the thin film’s structure probed via in situ grazing-incidence x-ray scattering (GIXS), and hydration properties. These results provide insight into the phenomena governing ionomer dispersion structure and the resulting film properties.