Polybenzimidazole enhance sulfonated polyimide composite proton exchange membrane with acid–base interaction

The article investigates the enhancement of sulfonated polyimide (SPI) composite proton exchange membranes through the integration of polybenzimidazole (PBI). SPI, known for its higher glass transition temperatures and diverse molecular structures, is a promising alternative to traditional Nafion membranes. However, SPI membranes often face challenges with mechanical strength and stability, particularly under high-temperature and high-humidity conditions. The study introduces a method for preparing SPI/PBI composite membranes using a solution casting technique, leveraging acid-base interactions to improve the mechanical properties and proton conductivity of the membranes. The results demonstrate that the SPI/PBI composite membranes exhibit significantly enhanced mechanical strength, oxidative stability, and resistance to water swelling. The tensile strength of the 3SPI/PBI composite membrane reached 106 MPa, which is 3.23 times that of the pure SPI membrane, while its swelling ratio was reduced to half that of pure SPI. Additionally, the proton conductivity of the composite membranes exceeded 0.01 S cm−1 across the tested temperature range. Theoretical calculations further support the strong binding interaction between SPI and PBI, highlighting the potential of SPI/PBI composite membranes for practical applications in proton exchange membrane technology.