Neutron Reflectometry (NR) was used to examine the interactions of Polymer Electrolyte Fuel Cell (PEFC) materials that comprise the triple-phase interface. Smooth, idealized layers of Nafion® on glassy carbon (GC) and Pt surfaces were used to experimentally model the PEFC electrode interfaces. Different multilayer structures of Nafion® were found in contact with the Pt or GC surfaces. These structures showed separate hydrophobic and hydrophilic domains formed within the Nafion® layer when equilibrated with saturated D2O vapor. A hydrophobic Nafion® region was formed adjacent to a Pt film. However, when Nafion® was in contact with a PtO surface, the Nafion® at the Pt interface became hydrophilic. The adsorbed oxide layer caused a long-range restructuring of the perfluorosulfonic acid (PFSA) polymer chains that comprise Nafion®. The thicknesses of the hydrophobic and hydrophilic domains changed to the same magnitude when the oxide layer was present compared to a thin hydrophobic domain in contact with Pt. A three-layer Nafion® structure was formed when Nafion® was in direct contact with GC. The findings in this research are direct experimental evidence that both the interfacial and long-range structural properties of Nafion® are affected by the material with which it is in contact. Evidence of physical changes of aged Nafion® films was obtained, and the results showed a permanent increase in the thickness of the Nafion® film and a decrease in scattering length density (SLD), which are attributed to irreversible swelling of the Nafion® film. The aging also resulted in a decrease in SLD of the GC substrate, which is likely due to either an increase in surface oxidation of the carbon or loss of carbon mass at the GC surface.