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<p>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 <i>para</i>-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<sup>−1</sup>. 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<sup>−2</sup> at 2 V (3 M KOH at 80 °C; Pt and NiFe electrode catalysts); the H<sub>2</sub> crossover to the O<sub>2</sub> side remained &lt;2%. Using non-platinum group metal electrodes and a polyphenylene sulfide-reinforced membrane, a cell operated for &gt;1,000 h without failure.</p>

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Sulfonated polybenzimidazole for low-alkalinity ion solvating membrane water electrolysis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月10日

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  • Muhammad Mara Ikhsan,
  • Chaeyeon Yang,
  • Kamal Ghotia,
  • Franz Egert,
  • Syed-Asif Ansar,
  • Olga Żurowska,
  • Maria Rózga,
  • Artur Michalak,
  • Mikkel Rykær Kraglund,
  • David Aili,
  • Hyun S. Park,
  • Fatemeh Razmjooei,
  • Dirk Henkensmeier

摘要

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 H2 crossover to the O2 side remained <2%. Using non-platinum group metal electrodes and a polyphenylene sulfide-reinforced membrane, a cell operated for >1,000 h without failure.