Sublayered structures of hydrated Nafion® thin film formed by casting on Pt substrate analyzed by X-ray absorption spectroscopy under ambient conditions and neutron reflectometry at temperature of 80°C and relative humidity of 30-80%

Teppei Kawamoto, Makoto Aoki, Taro Kimura, Pondchanok Chinapang, Takako Mizusawa, Norifumi L. Yamada, Fumiya Nemoto, Takeshi Watanabe, Hajime Tanida, Masashi Matsumoto, Hideto Imai, Junpei Miyake, Kenji Miyatake, Junji Inukai

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The structures of polymer electrolyte membranes and catalyst layer binders and the distribution of water therein are important for designing new ion-conductive ionomers for polymer electrolyte fuel cells. To aid the understanding of the in-plane water distribution, neutron reflectometry (NR) was carried out on a Nafion® film with a thickness of 150 nm formed on a 20-nm Pt layer deposited on Si(100) with a native SiO2 layer. By means of ambient pressure X-ray absorption spectroscopy at room temperature in air, the Pt substrate was found to be metallic. For NR, the temperature was set at 80°C and the relative humidity at 30, 50 and 80%, simulating the conditions for power generation. Clear NR modulation was obtained under each condition. NR data were fit very well with a 3-sublayered model parallel to the substrate with different densities of Nafion and water. The influence of the Pt substrate was observed not only at the Nafion/Pt interface, but also on the thin-film structure. The water uptake in a Nafion film on Pt also differed from that on SiO2. At 80°C, the surface of the Pt substrate was proposed to be oxidized, and the Nafion/Pt interface was found to contain water, in contrast to the interface observed at room temperature.

Original languageEnglish
Pages (from-to)270-275
Number of pages6
JournalElectrochemistry
Volume87
Issue number5
DOIs
Publication statusPublished - 2019
Externally publishedYes

Keywords

  • Nafion Thin Film
  • Neutron Reflectometry
  • Platinum Substrate
  • X-ray Absorption Spectroscopy

ASJC Scopus subject areas

  • Electrochemistry

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