(PEFC 15 Symposium Student Poster Award Winner) Heterogeneous Substrate Effects on Perfluorosulfonic-Acid Thin Films
Building off these previous results, we extend the study of ionomer thin films to heterogeneous substrates that begin to more closely resemble the complex nature of catalyst layers. Using standard nanofabrication techniques, mixed substrate interfaces are manufactured to study the substrate/film interaction and the propagation of interactions. Ionomer is spin-cast onto the substrates under various processing conditions. GISAXS is performed to determine the morphology under varying relative humidity and temperature. The morphological changes are correlated with swelling studies to begin to elucidate the structure/function/performance relationship. Varying the distance between interfaces and film thickness, we determine how far the interfacial effects propagate into either side of the heterogeneous substrate domains.
This work was funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231. The work utilizes beamline 7.3.3 at the Advanced Light Source, which is funded by DOE Basic Energy Sciences. We also acknowledge helpful discussions with Bryan McCloskey at University of California, Berkeley.
1. Page, K.A., et al., Confinement-driven increase in ionomer thin-film modulus. Nano Lett, 2014. 14(5): p. 2299-304.
2. Kusoglu, A., et al., Impact of Substrate and Processing on Confinement of Nafion Thin Films. Advanced Functional Materials, 2014. 24(30): p. 4763-4774.
Figure 1. Angle dependence of ionomer-peak intensity from GISAXS data for Nafion thin-films on different substrates. The inset shows the GISAXS profile for the Nafion on Pt sample and the integration angle. The figure clearly shows the anisotropy for the metallic substrates compared to the Si and carbon ones2.