Hydrogen/oxygen polymer electrolyte membrane fuel cells (PEMFCs) based on alkaline-doped polybenzimidazole (PBI)

When complexed with alkaline such as potassium hydroxide, sodium hydroxide or lithium hydroxide, films (40 mu m thick) of polybenzimidazole (PBI) show conductivity in the 5 × 10-5–10-1 S/cm-1 range, depending on the type of alkali, the time of immersion in the corresponding base bath and the temperature of immersion. It has been shown that PBI has a remarkable capacity to concentrate KOH, even in an alkaline bath of concentration 3 M. The highest conductivity of KOH-doped PBI (9×10-2 S cm-1) at 25°C obtained in this work is higher than the we had obtained previously as optimum values for H2SO4-doped PBI (5 × 10-2 S cm-1 at 25°C) and H3PO4-doped PBI ( 2 × 10-3 S cm-1 at 25°C). PEMFCs based on an alkali-doped PBI membrane were demonstrated, and their characteristics exhibited the same performance as those of PEMFCs based on Nafion® 117. Their development is currently under active investigation.