Work

Sulfonated polybenzimidazole for low-alkalinity ion solvating membrane water electrolysis

Year: 2025

Type: article

Abstract: Ion solvating membranes based on polybenzimidazole (PBI) are alternatives to diaphragms in alkaline water electrolysers but can typically only operate with electrolyte concentrations of 15–30 wt% KOH. Sulfonation of the membrane broadens the operational range to 0.1 wt%–30 wt%; however, the swelling of sulfonated para -PBI means that crosslinkers are needed, complicating membrane fabrication and decreasing alkaline stability. Here we report a non-crosslinked PBI membrane with a 50% degree of sulfonation that shows a high room temperature conductivity in 1 M KOH of 135 mS cm −1 . We did not observe degradation in a 6-month alkaline stability test at 80 °C. Using this membrane in an anion-exchange membrane water electrolyser, we report a current density of 4.8 A cm −2 at 2 V (3 M KOH at 80 °C; Pt and NiFe electrode catalysts); the H 2 crossover to the O 2 side remained <2%. Using non-platinum group metal electrodes and a polyphenylene sulfide-reinforced membrane, a cell operated for >1,000 h without failure.

Source: Nature Energy

DOI: 10.1038/s41560-025-01876-9