Fabrication of high performance high-temperature proton exchange membranes through constructing stable cation-rich domain in polybenzimidazole membrane

Improving the power density (≤ 700 mW cm-2) and long-term durability of fuel cells are crucial for promoting the practical application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In this study, a high-power density greater than 1000 mW cm-2 of fuel cell is obtained based on the designed polybenzimidazole (PBI) composite membranes containing cation-rich domains and stable two-phase interfaces. The newly designed membranes were fabricated by incorporating densely alkyl-bromide-functionalized polymer particles into the PBI membrane. The resulting composite membrane exhibited an improved mechanical strength of 12.6 MPa and high proton conductivity of 181.6 mS cm-1 at 160 oC. The power density of the corresponding composite membrane-based fuel cell reached 1090.5 mW cm-2 under a Pt loading of 0.6 mg cm-2 and H2/O2, without any humidification or backpressure at 160 oC, which is one of the most outstanding cell performances among all reported acid-doped high-temperature proton exchange membranes. Additionally, superior stability with a voltage decay rate of 0.0132 mV h-1 was observed in the long-term durability test. Thus, the proposed PBI composite membranes exhibit potential for use in HT-PEMFCs.