%0 Journal Article
%T Modification of Nafion Membranes by IL-Cation Exchange: Chemical Surface, Electrical and Interfacial Study
%A V. Romero
%A M. V. Mart¨ªnez de Yuso
%A A. Arango
%A E. Rodr¨ªguez-Castell¨®n
%A J. Benavente
%J International Journal of Electrochemistry
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/349435
%X Bulk and surface changes in two proton-exchange membranes (Nafion-112 and Nafion-117) as a result of the incorporation of the IL-cation n-dodecyltriethylammonium (or DTA+) by a proton/cation exchange mechanism after immersion in a DTA+ aqueous solution were analysed by impedance spectroscopy (IS), differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), and contact angle measurements performed with dry samples of the original Nafion and Nafion-DTA+-modified membranes. Only slight differences were obtained in the incorporation degree and surface chemical nature depending on the membrane thickness, and DTA+ incorporation modified both the hydrophobic character of the original Nafion membranes and their thermal stability. Electrical characterization of the dry Nafion-112 membrane was performed by impedance spectroscopy while different HCl solutions were used for membrane potential measurements. A study of time evolution of the impedance curves measured in the system ¡°IL aqueous solution/Nafion-112 membrane/IL aqueous solution¡± was also performed. This study allows us monitoring the electrical changes associated to the IL-cation incorporation in both the membrane and the membrane/IL solution interface, and it provides supplementary information on the characteristic of the Nafion/DTA+ hybrid material. Moreover, the results also show the significant effect of water on the electrical resistance of the Nafion-112/IL-cation-modified membrane. 1. Introduction As it is well known, ionic liquids are room temperature molten salts (RTILs) with very low vapour pressure and composed only of ions. These salts are characterized by weak interactions owing to the combination of a large cation and a charge-delocalized anion. Ionic liquids exhibit very interesting properties such as the solubilization of a large range of organic molecules and transition metal complexes or the possibility of their repeated use due to reduced environmental loss, while their good thermal stability tolerates reactive processes at high temperatures favouring a faster kinetic [1¨C4]. Various kinds of salts can be used to design an ionic liquid with tailoring properties for a given application, but typical IL-cations are imidazolium and quaternary ammonium salts, while hexafluorophosphate is a common anion. Due to their particular characteristics, the use of ILs in many areas of technology and science has increased lately and they can be used as solvents for organic reactions and catalysis, CO2 capture devices, selective separation of chemical species, dissolution of natural
%U http://www.hindawi.com/journals/ijelc/2012/349435/