Achieving high power density and excellent durability for high temperature proton exchange membrane fuel cells based on crosslinked branched polybenzimidazole and metal-organic frameworks

The power density and durability of fuel cells strongly rely on the properties of high-temperature (100 °C–200 °C) proton exchange membranes (HT-PEMs). Phosphoric acid-doped polybenzimidazole (PA-PBI) membranes are one of the most promising materials for HT-PEMs. However, the performance and durability of PA-PBI membranes still need to be improved. In this work, crosslinked branched PBI was chosen as polymer matrix due to its excellent chemical stability and high conductivity. The metal-organic framework (MOF) UiO-66 was introduced to constructed proton transport channels in crosslinked branched PBI composite membranes. As a result, a high proton conductivity (0.100 S cm−1) of the composite membrane at relatively low PA uptake (126%) was obtained and the long-term stability was improved significantly. The best peak power density of 607 mW cm−2 at 160 °C under anhydrous conditions was achieved for the composite membrane-based MEA in a fuel cell test. The fuel cell exhibits excellent durability and only a slight decrease in the load voltage value (36.0 μV h−1) is observed. These results indicate that introducing UiO-66 MOF into cross-linked branched PBI membranes may provide a valid method towards developing high-performance HT-PEMs.