Highly durable alkaline water electrolyzer with branched poly(oxindole biphenylene) ion-solvating membrane

Abstract

Ion-solvating membranes (ISMs) offer a novel approach for high-rate alkaline water electrolyzers (AWEs), but device durability remains a major challenge for their practical application. Herein, we first found that the oxidation stability of ISMs in electrolyzers showed a significant effect on their long-term device durability, in addition to the alkaline stability. More importantly, both the operating temperature and the voltage have been observed as crucial factors affecting the oxidative stability of ISMs. While maintaining other excellent properties, the branching polymer chain in ISMs could further enhance their oxidative stability. As a result, a highly durable AWE with branched poly(oxindole biphenylene) (POBP) ISMs operated stably for over 15,000 h at 2.26 V and 60°C, representing the longest reported lifetime for ISM-based AWEs to date. These results provide significant guidance on how to reasonably design the polymer backbone and adjust the operating conditions to prolong the membrane’s lifetime in AWEs for practical applications.