Understanding potassium hydroxide transport in anion-exchange-membrane water electrolysis via asymmetric feed

Anion exchange membrane water electrolysis (AEMWE) has been the focus of significant research as it combines the advantages of previous electrolysis technologies. One pressing problem is the use of potassium hydroxide (KOH) as the feed in AEMWE systems due to its role in performance degradation. Asymmetric operation is one way forward, but the transport of KOH within these systems has not been extensively studied. Herein, a comprehensive study of KOH transport via pH measurement in-operando is exhibited. We have shown that KOH crossover heavily impacts the AEMWE performance. Transport number of potassium ion (K + ) is calculated, indicating that K + significantly contributes to the current. Moreover, we have shown that different alkali cations behave differently under applied electric fields. These measurements shed light on apparent mass transport limitations when near-neutral anolyte is used. Thus, the importance of KOH transport is highlighted herein, and directly contributes to the understanding of AEMWE. • KOH crossover heavily impacts performance of asymmetric AEMWE. • Cations significantly contribute to current in asymmetric AEMWE systems. • Different alkali cations move differently through the membrane during operation. • Effluent pH correlates with mass transport limitation region in low pH conditions.