Research on methanol permeation of proton exchange membranes with incorporating ionic liquids

Abstract

Methanol permeation and conductivity of membrane materials are important factors to evaluate the feasibility of application as proton exchange membranes (PEMs) in direct methanol fuel cell (DMFC). The methanol permeation values of these composite membranes based on ionic liquids of trifluoroacetic propylamine (TFAPA) and the disubstituted imidazolium cations with different anions were summarized, and the methanol permeation behaviors were investigated in this work. Although these polymer/ionic liquid composite membranes displayed satisfactory conductivities, the relative selectivity values of conductivity to methanol permeability were lower than the value of Nafion^® membrane. Moreover, polymerized ionic liquids (PILs) membranes showed the strong ability to hinder methanol permeation with a value around 10⁻¹¹ cm²/s at 10 M methanol solution. The maximum relative selectivity value reached (2.23–1.76) × 10⁶ S·s/cm³ for PVC-MIMCl membrane, which was near two orders of magnitude higher than the reported 2.47 × 10⁴ S·s/cm³ for Nafion-117 membrane at 2 M methanol solution.

Graphical abstract

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