HT-PEMs based on carbazole grafted polybenzimidazole with high proton conductivity and excellent tolerance of phosphoric acid

A set of grafted AmPBI-Car-X membranes based on amino polybenzimidazole (AmPBI) and 9-(4-Bromobutyl)-9H-carbazole (Car) have been synthesized. The membranes are applied to high temperature-proton exchange membranes (HT-PEMs). Due to its large volume and rigid structure, the obtained membranes can maintain enough mechanical strength and lower swelling while absorbing more phosphoric acid (PA). Among them, AmPBI-Car-10 has the best comprehensive performance. When its PA doping level (ADL) reaches 10.5, its proton conductivity is as high as 125.3 mS cm-1 under anhydrous conditions at 180 °C, which is 2.7 times compare with pristine AmPBI (47 mS cm-1). Moreover, AmPBI-Car-10 has a lower swelling ratio of 156.7%, which is lower than that of AmPBI while being doped with more PA. The power density of AmPBI-Car-X is higher than many reported membranes at 350 mA cm-2. It is worth noting that the conductivity of AmPBI-Car-10 membrane can still reach 94.9 mS cm-1 at 180 °C after the PA retention test under 160 °C non-humidity for 240 h.