Transfer-free in-situ synthesis of high-performance polybenzimidazole grafted graphene oxide-based proton exchange membrane for high-temperature proton exchange membrane fuel cells

The preparation of traditional graphene oxide (GO)-based proton exchange membrane (PEM) composites asks for multiple transfer steps due to the different solvent requirements of GO preparation and polymer synthesis. Moreover, GO is easy to agglomerate in polymer matrix, it is difficult to give full play to the excellent proton conductivity of single/few-layered nanosheets. Herein, a novel transfer-free in-situ method is developed to prepare poly(2,5-benzimidazole) (ABPBI)-grafted electrolytic graphene oxide (EGO) composites (ABPBI-EGO) for high-temperature (HT) PEM fuel cells applications. The process involves the in-situ electrochemical oxidation and exfoliation of graphite foil into single/few-layered EGO in Eaton's reagent and followed by in-situ synthesis of ABPBI-grafted-EGO composites in the same reagent. This strategy leads to a single or few-layered dispersion of EGO nanosheets in ABPBI matrix, thus significantly improving the physicochemical performance. By constructing fast proton-conducting channels through single/few-layered GO nanosheets, composite membranes without free phosphoric acid exhibit superior proton conductivities over the whole temperature range of 120–180 °C. ABPBI-0.5EGO composite membrane-based fuel cell achieves a power density of 349 mW/cm2 at 180 °C, which is nearly 2.3 times higher than the original ABPBI membrane. Thus, this transfer-free in-situ strategy shows great promise for developing high-performance HT-PEMs.