Functionalized TiO₂ mediated organic-inorganic composite membranes based on quaternized poly(arylene ether ketone) with enhanced ionic conductivity and alkaline stability for alkaline fuel cells

In this work, quaternized poly(arylene ether ketone) (QPAEK)/functionalized TiO₂ (f-TiO₂) composite membranes were fabricated with different f-TiO₂ contents (1, 3, 5, 7, and 9 wt%), and the structure of the materials was characterized by ¹H NMR, ATR-FT-IR, XRD, XPS, and FE-SEM. The addition of f-TiO₂ enlarges the ion cluster in the membrane due to enhancing the interaction between the functional groups, and SAXS analysis revealed an extension of the ion domain size with an increase in the filler content (up to 5 wt%). In particular, the composite membrane with 5 wt% f-TiO₂ displayed the highest ion conductivity (74.6 mS cm⁻¹); such a result was attributed to the formation of water traps by the deliquescence of TiO₂ and enhanced interfacial interactions between the pure organic polymers and inorganic nanomaterials. This work proves that a composite membrane with an appropriate f-TiO₂ concentration is a promising candidate for application to anion exchange membranes.