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

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

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 e...

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Bibliographic Details
Published in:International journal of hydrogen energy Vol. 37; no. 7; pp. 6308 - 6316
Main Authors: Catalano, J., Myezwa, T., De Angelis, M.G., Baschetti, M. Giacinti, Sarti, G.C.
Format: Journal Article Conference Proceeding
Language:English
Published: Kidlington Elsevier Ltd 01-04-2012
Elsevier
Subjects:
Alternative fuels. Production and utilization
Applied sciences
Controlled humidity
Energy
Exact sciences and technology
Fuel cells
Fuels
Gas permeability
Hydrogen
Ionomers
Membranes
PFSI membranes
Water swelling
Gas permeability
Water swelling
PFSI membranes
Controlled humidity
Ionomers
Fuel cells
Relative humidity
Measurement
Swelling
Hydrogen
Water gas
Helium
Membrane
Microstructure
Fuel cell
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Summary: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 O2 and N2, and less marked for He permeability. The relative permeability increase, Pgas/Pgas,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 N2, O2 over N2 and He over O2, decreases markedly with increasing water content in the membrane. ► We measure He, N2 and O2 permeability in Aquivion® and Nafion® at 35 °C and RH< 90%. ► We measure swelling versus RH in both membranes and estimate water volume fraction. ► The gas permeability increases with RH, more markedly for the slower gases N2 and O2. ► The ideal selectivity He/N2, He/O2, O2/N2 decreases with RH. ► The gas permeability enhancement is higher for Nafion® at water volume fractions >15%.
Bibliography:ObjectType-Article-2
SourceType-Scholarly Journals-1
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content type line 23
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2011.07.047