FTIR-ATR study of water distribution in PFSI membranes

Maria Chiara Ferrari, Jacopo Catalano, Marco Giacinti Baschetti, Maria Grazia De Angelis, Giulio C. Sarti

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Water vapor sorption in a short-side-chain perfluorosulphonic acid ionomer membrane, suitable for use as electrolyte in Proton Exchange Membranes Fuel Cells, was studied in detail by using Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy. The analysis of the IR spectra of the membrane at different values of relative humidity (0.00-0.50) and at 35°C allowed to recognize four types of water molecules, characterized by decreasing strength of interaction with the sulphonate sites of the membrane. The concentration of each water population inside the membrane was then determined through calibration with independent measurements of water vapor uptake in the membrane. Two different sorption mechanisms were identified: a Langmuir-like adsorption (1st, 2nd, 3rd water population) and a Henry-like absorption (4th water population). In particular, the 1st population is strongly bound directly to sulphonate sites, while the 2nd and the 3rd ones form subsequently adsorbed layers; the 4th population is formed by mobile water molecules, which are not directly interacting with the acid sites. Only three adjustable parameters are required to describe the sorption behavior of the different populations, whose values are consistent with those reported in the literature, confirming the validity of the physical description presented.

Original languageEnglish
Title of host publication10AIChE - 2010 AIChE Annual Meeting, Conference Proceedings
Publication statusPublished - 1 Dec 2010
Event2010 AIChE Annual Meeting, 10AIChE - Salt Lake City, UT, United States
Duration: 7 Nov 201012 Nov 2010


Conference2010 AIChE Annual Meeting, 10AIChE
Country/TerritoryUnited States
CitySalt Lake City, UT


  • Acid site
  • Adjustable parameters
  • Adsorbed layers
  • Attenuated total reflectance
  • Fourier transform infrared
  • Independent measurement
  • Ionomer membranes
  • IR spectrum
  • Langmuirs
  • Mobile water
  • Proton exchange membranes fuel cells
  • Relative humidities
  • Short side chains
  • Sorption mechanism
  • Sulphonates
  • Water distributions
  • Water molecule
  • Water vapor sorption
  • Water vapor uptake
  • Adsorption
  • Atmospheric humidity
  • Fourier transforms
  • Fuel cells
  • Ion exchange membranes
  • Molecules
  • Water absorption
  • Water supply systems
  • Water vapor


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