Polymeric ionic liquids and piperidinium synergistically improve proton conductivity and acid retention of polybenzimidazole-based proton exchange membranes

Amino-type polybenzimidazole is prepared, then ionic liquid with three nitrogen positive sites ([CTDTr]Br 3 ) is polymerized into polymeric ionic liquids (PILs) by in-situ radical polymerization, and AmPBI-CTDTr-P x membranes were prepared by piperidinium (PPd) and [CTDTr]Br 3 combination to cross-linked with AmPBI. Following treatment with KOH and phosphoric acid (PA), the ion pairs (N + - H 2 PO 4 − ) generated in the composite membrane system can enhance proton conductivity and facilitate proton transport. The AmPBI-CTDTr-P x membranes shown exceptional PA retention as a result of the alkaline properties of both [CTDTr]Br 3 and PPd, which can engage in acid-base interactions with phosphoric acid. Specifically, the proton conductivity of AmPBI-CTDTr-P 5 at 180 °C is 129.7 mS cm −1 , which is 2.52 times that of pure membranes. Acid retention of AmPBI-CTDTr-P 5 at 80 °C/40 % RH and 160 °C are 64.4 % and 84 %.