High-temperature water-free proton conducting membranes based on poly(arylene ether ketone) containing pendant quaternary ammonium groups with enhanced proton transport

Poly(arylene ether ketone) containing pendant quaternary ammonium groups (QPAEKs) are anion-conducting polymers synthesized from benzylmethyl-containing poly(arylene ether ketone)s (PAEK-TM). Then QPAEK membranes doped with different concentrations of H3PO4 are prepared and evaluated as high temperature proton exchange membranes. The H3PO4 doping ability of quaternary ammonium groups in QPAEK system is found to be stronger than that of imidazole groups in polybenzimidazole system. The doping level of resulting QPAEK/H3PO4 composite membranes increases with both the concentration level of soaking H3PO4 solution and the ion exchange capacity. For example, the highest doping level of composite membranes is 28.6, which is derived from QPAEK-5 with an ion exchange capacity of 2.02 mmol g−1 saturated with concentrated phosphoric acid. A strong correlation between the doping level and the proton conductivity is observed for all the membranes. Besides their low cost, novel high temperature proton exchange membranes, QPAEK/H3PO4, show really high proton conductivity and possess excellent thermal and mechanical stability, suggesting a bright future for applications in high temperature fuel cell.

► Poly(arylene ether ketone)s with quaternary ammonium groups (QPAEKs) are prepared.
► QPAEK membranes are doped with H3PO4 as high temperature proton exchange membranes.
► QPAEK membranes show strong interaction with H3PO4.
► The doped membranes show great proton conductivity and excellent mechanical stability.
► The proton conductivity increases with quaternary ammonium group content.