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*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 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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