Non-N-substituted crosslinked polybenzimidazole membranes for durable alkaline electrolysis

Polybenzimidazole (PBI)-based ion-solvating membranes have emerged as an alternative for alkaline water electrolysis. However, their long-term durability remains a critical challenge that hinders practical application. To address this issue, we report a non-N-substituted PBI-crosslinked membrane prepared using benzoxazine as a crosslinker. An electrolyzer cell employing the membrane with 20 wt.% crosslinker exhibited enhanced cell performance in 10 wt.% KOH solution at 60 °C compared to that shown by the pristine m-PBI-based cell, while maintaining the hydrogen crossover below 1% across the current density range of 0.3–1.2 A cm−2. Furthermore, the cell employing the crosslinked m-PBI membrane exhibited stable operation for over 1900 h, with hydrogen crossover remaining below 4% throughout the test. Notably, the increase rate of hydrogen crossover in the crosslinked membrane-based cell decreased nearly fourfold compared to that of the pristine m-PBI-based cell, demonstrating the effectiveness of crosslinking in enhancing cell durability. Polybenzimidazole-based ion-solvating membranes show promise for alkaline water electrolysis, but durability remains a challenge. Here, the authors show that a benzoxazine-crosslinked polybenzimidazole membrane improved electrolyzer durability and performance.