FTIR-ATR Study of Water Distribution in a Short-Side-Chain PFSI Membrane

Maria-chiara Ferrari, Jacopo Catalano, Marco Giacinti Baschetti, Maria Grazia De Angelis, Giulio Cesare Sarti

Research output: Contribution to journalArticlepeer-review


Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to study in detail water vapor sorption in a short-side-chain perfluorosulfonic acid ionomer membrane suitable for use as electrolyte in proton exchange membranes fuel cells. The analysis of the membrane IR spectra, at different values of relative humidity (0.00-0.50) and at 35 °C, allows to identify four types of water molecules, characterized by decreasing strength of interaction with the polymer sulfonate groups. The actual concentration of the different water species inside the membrane was determined by calibrating the IR absorbance data with independent measurements of total water vapor uptake. The sorption of the different populations of water can be represented by Langmuir isotherms: the first population is directly attached to sulfonate sites, while the others form subsequent layers, adsorbed one onto the other in a shell-like structure. To describe the overall sorption behavior of the different populations, four adjustable parameters are required, which are consistent with literature data, thus supporting the validity of the physical model considered. © 2012 American Chemical Society.
Original languageEnglish
Pages (from-to)1901-1912
Number of pages12
Issue number4
Publication statusPublished - 28 Feb 2012


  • Absorbance data
  • Adjustable parameters
  • Independent measurement
  • Ionomer membranes
  • IR spectrum
  • Langmuir isotherm
  • Literature data
  • Perfluorosulfonic acid
  • Physical model
  • Proton exchange membranes fuel cells
  • Shell-like structures
  • Short side chains
  • Sulfonate groups
  • Total reflectance
  • Total water vapors
  • Water distributions
  • Water molecule
  • Water species
  • Water vapor sorption
  • Fourier transform infrared spectroscopy
  • Ion exchange membranes
  • Sorption
  • Water supply systems
  • Population statistics


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