High performance porous polybenzimidazole membrane for alkaline fuel cells

• KOH-doped porous polybenzimidazole (pPBI) was made for alkaline fuel cells (AFC).
• The introduction of porosity created open paths for ion transfer and KOH absorption.
• The ionic conductivity of pPBI was three times higher than that of commercial FAA.
• Alkaline stability of pPBI was for 14 days, whereas, FAA degraded after 3 h.
• AFC single cell performance of pPBI was two times higher than that of commercial FAA.

In this study, a highly ion-conductive and durable porous polymer electrolyte membrane based on ion solvating polybenzimidazole (PBI) was developed for anion exchange membrane fuel cells (AEMFCs). The introduction of porosity can increase the attraction of electrolytic solutions (e.g., potassium hydroxide (KOH)) and ion solvation, which results in the enhancement of PBI's ionic conductivity. The morphology, thermo-physico-chemical properties, ionic conductivity, alkaline stability, and the AEMFC performance of KOH-doped PBI membranes with different porosities were characterized. The ionic conductivity and AEMFC performance of 70 wt.% porous PBI was about 2 times higher than that of the commercially available Fumapem® FAA. All KOH-doped porous PBI membranes maintained their ionic conductivity after accelerated alkaline stability testing over a period of 14 days, while the commercial FAA degraded just after 3 h. The excellent performance and good durability of KOH-doped porous PBI membrane makes it a promising candidate for AEMFCs.