High-performed composite OPBI membrane with ordered proton transport nanochannels for HT-PEMFC

Low phosphoric acid (PA) retention and conductivity are the inherent drawbacks for PA-doped polybenzimidazole (OPBI) membranes, which are applied in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In this work, we designed and synthesized a type of covalent organic framework linked with quaternary ammonium alkyl chains (COF-BQA) and organically combined it with OPBI to prepare composite membranes, which utilized strong ion-pair interaction between quaternary ammonium groups and H 2 PO 4 − to increase PA retention. Meanwhile, the composite membranes formed ordered microstructures to store PA and ordered ion transport nanochannels to increase proton conductivity. This synergistic effect showed that COF-BQA (5 %)-PA/OPBI could obtain good anhydrous proton conductivity of 121 mS cm −1 , high phosphoric acid retention of 70.1 %, good humidity cycle stability and high peak cell power density of 733.3 mW cm −2 , which was significantly better than that of pristine PA/OPBI.