Self-assembly and transport limitations in confined nafion films

Miguel A. Modestino, Devproshad K. Paul, Shudipto Dishari, Stephanie A. Petrina, Frances I. Allen, Michael A. Hickner, Kunal Karan, Rachel A. Segalman, Adam Z. Weber

Research output: Contribution to journalArticlepeer-review

Abstract

Ion-conducting polymers are important materials for a variety of electrochemical applications. Perfluorinated ionomers, such as Nafion, are the benchmark materials for proton conduction and are widely used in fuel cells and other electrochemical devices including solar-fuel generators, chlor-alkali cells, and redox flow batteries. While the behavior of Nafion in bulk membranes (10 to 100s μm thick) has been studied extensively, understanding its properties under thin-film confinement is limited. Elucidating the behavior of thin Nafion films is particularly important for the optimization of fuel-cell catalyst layers or vapor-operated solar-fuel generators, where a thin film of ionomer is responsible for the transport of ions to and from the active electrocatalytic centers. Using a combination of transport-property measurements and structural characterization, this work demonstrates that confinement of Nafion in thin films induced thickness-dependent proton conductivity and ionic-domain structure. Confining Nafion films to thicknesses below 50 nm on a silicon substrate results in a loss of microphase separation of the hydrophilic and hydrophobic domains, which drastically increases the material's water uptake while in turn decreasing its ionic conductivity.

Original languageEnglish (US)
Pages (from-to)867-873
Number of pages7
JournalMacromolecules
Volume46
Issue number3
DOIs
StatePublished - Feb 12 2013

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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