Constructing stable continuous proton transport channels by in-situ preparation of covalent triazine-based frameworks in phosphoric acid-doped polybenzimidazole for high-temperature proton exchange membranes

Phosphoric acid (PA)-doped high-temperature proton exchange membranes (HTPEMs) suffer from low efficiency of proton transport and severe PA leakage. Constructing a stable continuous proton transport channel may be a promising method to address the above issues. Herein, a stable proton transport channel was constructed for the first time by in-situ preparing covalent triazine-based frameworks (CTFs) in polybenzimidazole under a mild trifluoromethanesulfonic acid (TFA) catalysis condition. The membranes were prepared with CTFs loading from 10% to 40%, and the properties of the membranes were characterized carefully. The membrane containing 30% CTFs showed some attractive properties, such as high conductivity (74.8 mS cm−1) under low PA doping level (167.1%), low volume swelling (71.8%), and high PA retention ability (89.5%). Importantly, under the same PA doping level, the single fuel cell assembled with the composite membranes showed a higher peak power density (534.4 mW cm−2) than that of poly [2,2′-(p-oxydiphenylene)-5,5′-benzimidazole] (OPBI) (325.2 mW cm−2). The results prove that constructing a stable proton transport channel can improve the properties of the membranes and the prepared membranes can potentially be used as HTPEMs.