PBI/Nafion/SiO2 hybrid membrane for high-temperature low-humidity fuel cell applications

A novel composite membrane for fuel cell applications was prepared by incorporating SiO2 in PBI/Nafion resin by the sol-gel method. Polybenzimidazole (PBI) was blended with Nafion to improve the membrane stability. The presence of PBI also improves the dimensional stability of the composite membrane over a wide range of hydration conditions. Being highly hygroscopic, SiO2 enhances water absorption and retention in the membrane which improves fuel cell performance under low relative humidity conditions. Scanning electron microscopy showed that the PBI and Nafion polymers can be blended uniformly. Energy dispersive X-ray spectroscopy confirmed the presence of SiO2 in the composite membrane. Thermal gravimetric analysis confirmed the improved thermal stability of the SiO2/PBI/Nafion membrane. Tensile strength, water uptake and swelling of the composite membrane were also measured at 60 °C and compared with Nafion. The fuel cell performance of the novel SiO2/PBI/Nafion composite membrane at 120 °C and 35% relative humidity significantly improved over a pure Nafion membrane of the same thickness.