Fuel cell electrolyte membranes based on copolymers of protic ionic liquid [HSO3-BVIm][TfO] with MMA and hPFSVE

Abstract

Polymeric ionic liquids (PILs) have recently been attracting great attention as new types of electrolytes for polymer exchange membrane fuel cells (PEMFCs), clean energy devices, due to their outstanding properties. In this work, the copolymerization of the ionic liquid (IL) 1-(4-sulphobutyl)-3-vinylimidazolium trifluoromethanesulphonate, [HSO3-BVIm][TfO], with methyl methacrylate (MMA) and perfluoro-3,6-dioxa-4-methyl-7-octene sulfonyl fluoride in its hydrolyzed form (hPFSVE), respectively, was performed for the preparation of structurally new IL copolymer membranes with enhanced conductive properties in comparison with the pristine PIL form. Membranes were synthesized through a facile photopolymerization method under UV radiation. The effect of temperature under wet and dry conditions on the ionic conductivities of the resulting membranes was analyzed. The performances of the new membranes were also assessed in a proton exchange fuel cell for power generation. Both poly([HSO3-BVIm][TfO]-co-MMA) and poly([HSO3-BVIm][TfO]-co-hPFSVE) electrolyte membranes offered high conductivity even in dry conditions (in the order 10−3 - 10−2 S cm−1). At low MMA and hPFSVE amounts (10 mol%), the ionic conductivity and power performances of the resulting membranes were enhanced in comparison with the membrane only constituted of the polymerizable IL showing the promising prospects of these ionic liquid-based copolymers as proton exchange membranes, with power outputs up to 45 mW cm−2.