Chemical Surface, Thermal and Electrical Characterization of Nafion Membranes Doped with IL-Cations

Surface and bulk changes in a Nafion membrane as a result of IL-cation doping (1-butyl-3-methylimidazolium tetrafluoroborate or BMIM+BF4 and phenyltrimethylammonium chloride or TMPA+Cl-) were studied by X-ray photoelectron spectroscopy (XPS), contact angle, differential scanning calorimetry (DSC) an...

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Bibliographic Details
Published in:Applied sciences 2014-06, Vol.4 (2), p.195-206
Main Authors: Martinez, Maria del Valle, Yuso, de, Arango-Diaz, Ana, Bijani, Shanti, Romero, Virgina, Benavente, Juana, Rodriguez-Castellon, Enrique
Format: Article
Language:English
Subjects:
Cation exchanging
Chlorides
Contact
Contact angle
Differential scanning calorimetry
Electrolytes
Fuel cells
hydrophobic character
impedance spectroscopy
ionic liquids
Membrane separation
Membranes
Molecular weight
Nafion
Polymers
Thermal properties
X-ray photoelectron spectroscopy
XPS
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Summary:Surface and bulk changes in a Nafion membrane as a result of IL-cation doping (1-butyl-3-methylimidazolium tetrafluoroborate or BMIM+BF4 and phenyltrimethylammonium chloride or TMPA+Cl-) were studied by X-ray photoelectron spectroscopy (XPS), contact angle, differential scanning calorimetry (DSC) and impedance spectroscopy (IS) measurements performed with dry samples after 24 h in contact with the IL-cations BMIM+ and TMPA+. IL-cations were selected due to their similar molecular weight and molar volume but different shape, which could facilitate/obstruct the cation incorporation in the Nafion membrane structure by proton/cation exchange mechanism. The surface coverage of the Nafion membrane by the IL-cations was confirmed by XPS analysis and contact angle, while the results obtained by the other two techniques (DSC and IS) seem to indicate differences in thermal and electrical behaviour depending on the doping-cation, being less resistive the Nafion/BMIM+ membrane. For that reason, determination of the ion transport number was obtained for this membrane by measuring the membrane or concentration potential with the samples in contact with HCl solutions at different concentrations. The comparison of these results with those obtained for the original Nafion membrane provides information on the effect of IL-cation BMIM+ on the transport of H+ across wet Nafion/BMIM+ doped membranes.
ISSN:2076-3417
2076-3417
DOI:10.3390/app4020195