  Structure of polymer electrolytes membranes, e.g., Nafion, inside fuel cell
catalyst layers has significant impact on the electrochemical activity and
transport phenomena that determine cell performance. 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/hydrophobic character of these
surfaces on the structural formation of the films and, in turn, on transport
properties, has not been sufficiently explored yet. Here, we report about
classical Molecular Dynamics simulations of hydrated Nafion thin-films in
contact with unstructured supports, characterized by their global wetting
properties only. We have investigated structure and transport in different
regions of the film and found evidences of strongly heterogeneous behavior. We
speculate about the implications of our work on experimental and technological
activity.
