著者

Shrivastava Udit N. Suetsugu Kota Nagano Shusaku Fritzsche Helmut Nagao Yuki Karan Kunal

出版者

Royal Society of Chemistry

雑誌

Soft Matter (ISSN:1744683X)

巻号頁・発行日

vol.16, no.5, pp.1190-1200, 2019-12-16

被引用文献数

21

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Nanometer thin films of Nafion ionomer interfacing with platinum form the functional electrode in many electrochemical devices including fuel cells and electrolyzers. To impart facile proton conduction in Nafion ionomer, sufficient hydration of Nafion ionomer is necessary to create a percolating network of water-filled nanometer sized hydrophilic domains that manifests as macroscopic swelling. This hydration behavior of ionomer thin films is poorly understood especially for films confined on electrochemically relevant Pt substrates. In this work, we present the evolution of hydration-dependent microscopic hydrophilic domains and macroscopic expansion of 55 nm thin Nafion film on a Pt substrate. The cross-correlation among the film macro-expansion from ellipsometry, the micro-expansion from GISAXS, and the water distribution from neutron reflectometry (NR), explains the observed non-affine behavior of the film which can be attributed to the randomly and spatially non-uniform distribution of water domains. A correlation between macroscopic factor (ε/τ) for protonic conductivity, and the domain size and swelling is presented for the first time. In addition, interfacial water between Pt and the ionomer interface estimated at 75% and 84% RH, and increase in domain size with RH, are discussed to explain increased activity and oxygen diffusivity with RH.