Effect of Surface Hydrophilicity on the Formation of Nafion Thin Films Inside PEMFC Catalyst Layers: A Computational Study

Structure of Nafion inside Polymer Electrolyte Membrane Fuel Cells (PEMFC) catalyst layers is suspected to have a significant impact on the electrochemical activity and transport phenomena that determine the overall cell performances. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic character of these surfaces on the structural formation of the films has not been explored in details yet. Here, we report about our Molecular Dynamic computer simulations studies of the formation of Nafion thin films in contact with unstructured continuous surfaces, characterized by their global wetting properties only. We investigate changes of morphology and nanostructure of the perfluorosulfonic acid polymer as a result of water and polymer-surface affinities. Charge and water distributions are also analyzed. Possible impact of Nafion thin film self-assembly on the actual activity properties of realistic catalysts layers is shortly discussed.