Diffusivity and free anion concentration of ionic liquid composite polybenzimidazole membranes. Issue 42 (2nd August 2021)

• Record Type: Journal Article
• Authors: Barjola, Arturo; Escorihuela, Jorge; García-Bernabé, Abel; Sahuquillo, Óscar; Giménez, Enrique; Compañ, Vicente
• Is Part Of: RSC advances. Volume 11:Issue 42(2021)
• Page Start: 26379
• Page End: 26390
• Publication Date: 2021-08-02
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d1ra05364g
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : PBI composite membranes containing 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf2 ) at 1, 5, 10, 20 and 50 wt% have been prepared and the conductivity has been analyzed by electrochemical impedance spectroscopy. Abstract : In this article, PBI composite membranes containing the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf2 ) at 1, 5, 10, 20 and 50 wt% (named PBI-IL- x ) have been prepared by a casting method. The internal morphology of the membranes was analyzed by scanning electron microscopy (SEM), revealing that the incorporation of IL promotes the formation of porous channels. Thermal and mechanical stability was confirmed by thermogravimetric analysis (TGA) and tensile test measurements. The ionic transport through membranes was analysed by means of electrochemical impedance spectroscopy (EIS), showing a dependence on the IL loading, reaching a highest conductivity value of 1.8 × 10 −2 S cm −1 for the PBI-IL-50 membrane at 160 °C. The experimental results showed a Vogel–Fulcher–Tammann (VFT) type relation for the ionic conductivity with temperature and the calculated activation energies suggest that ionic conduction in the films can occur by both hopping and vehicle-type mechanisms. Eyring's absolute rate theory was also used to obtain activation enthalpy and entropy from the temperature dependence of the conductivity. Diffusivity and free ion number density were obtained by means of electrode polarization analysis to obtain more insight into the conduction in these composite membranes. Finally, the Debye length was calculated and related to both transport parameters.