Tuning the Hydrophobic Component in Reinforced Poly(arylimidazolium)-Based Anion Exchange Membranes for Alkaline Fuel Cells

A series of imidazolium-based aromatic copolymers were synthesized using fluorinated and non-fluorinated hydrophobic monomers. The quaternized copolymers were reinforced with the plasma-treated porous polyethylene substrate to provide flexible, homogeneous membranes. Cross-sectional SEM images revealed a triple-layer structure. The reinforced membranes exhibited phase-separated morphology as confirmed through TEM images. Among the membranes, QQP-MEIm-PE-containing quinquephenylene hydrophobic groups exhibited the most balanced properties (ion conductivity, mechanical strength, and alkaline stability). In particular, QQP-MEIm-PE exhibited excellent elongation properties with 24 MPa maximum stress and 205% elongation at break. A single H2/O2 fuel cell using the QQP-MEIm-PE membrane (1.26 meq g–1) and non-PGM-(Fe–N–C) cathode achieved 222 mW cm–2, which accounted for 888 mW mg–1Pt at 560 mA cm–2. Reasonable durability was confirmed with the membrane in the operating fuel cell.