2021 Volume 64 Issue 7 Pages 329-334
The structures of polymer electrolyte membranes and binders and the distributions of water therein are important for designing new ion-conductive ionomers for polymer electrolyte fuel cells (PEFCs). To aid the understanding of the water distribution, neutron reflectometry was carried out at 80℃ and the relative humidity of 30–80%, simulating the conditions for the PEFC power generation on Nafion® films formed on SiO2/Si(100) and Pt/SiO2/Si(100) substrates. For Nafion films on a native SiO2 layer, the NR data were fit very well with a 4-layer model parallel to the substrate with different densities of Nafion and water. At the interface between the Nafion film and the SiO2 substrate, a 1-nm water-rich layer was observed under all conditions. For Nafion films on a Pt layer, the NR data were fit with a 3-layered model. The thin film structures of Nafion were very different on different substrates of SiO2 and Pt.
