The effect of relative humidity on the gas permeability and swelling in PFSI membranes

J. Catalano, T. Myezwa, M.G. De Angelis, M.G. Baschetti, G.C. Sarti

Research output: Contribution to journalArticlepeer-review

Abstract

The permeation of helium, oxygen and nitrogen in perfluorosulphonic acid ionomeric (PFSI) membranes with short and long side chains, namely Aquivion ® and Nafion ® 117, was studied in the relative humidity range between 0 and 90%, and at temperatures between 35 °C and 65 °C. The presence of humidity enhances, up to a factor of 100, the gas permeability in the membranes, due to the permeation of gas molecules in the hydrophilic domains: the enhancement is rather pronounced for O 2 and N 2, and less marked for He permeability. The relative permeability increase, P gas/P gas,0, shows a complex dependence on the relative humidity, as the water content in the membrane is itself a non linear function of this parameter. The water volume fraction in the membrane at each activity was accurately estimated from measurements of vapor-induced swelling, which indicate that the partial molar volume of water is smaller than its pure liquid value, in both membranes at 35 °C. When plotted against water volume fraction, the gas permeability increases exponentially in the range between 2% and 20%; the slope of the curve is higher for Nafion ® than for Aquivion ®, as it is reasonable due to their different microstructures. The ideal selectivity of the two membranes for He over N 2, O 2 over N 2 and He over O 2, decreases markedly with increasing water content in the membrane. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.
Original languageEnglish
Pages (from-to)6308-6316
Number of pages9
JournalInternational journal of hydrogen energy
Volume37
Issue number7
DOIs
Publication statusPublished - 2012

Keywords

  • Gas molecules
  • Hydrophilic domains
  • Nonlinear functions
  • Partial Molar volume
  • Permeability increase
  • Pure liquids
  • Relative humidity range
  • Relative permeability
  • Side-chains
  • Water swelling
  • Water volume fraction
  • Atmospheric humidity
  • Fuel cells
  • Gas permeability
  • Helium
  • Ionomers
  • Permeation
  • Water vapor
  • Gas permeable membranes

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