Realizing Superior Durability of Water Electrolyzer Using Anion Exchange Membrane with an Interstitial Alkyl Chain: From a Single Cell to Large‐Sized 1‐cell Stack

Abstract Anion exchange membrane water electrolysis (AEMWE) has gained attention as an attractive alternative to alkaline and proton exchange membrane water electrolysis (PEMWE) due to its high efficiency and low hydrogen unit cost. However, the long‐term durability of AEMWE is ≈10 times lower than that of PEMWE, which typically operates for 40 000 h. Here, a new design strategy is presented for aryl ether‐free PFPBPF‐QA anion exchange membranes with interstitial alkyl chains in the conducting groups and polymer backbone. The rationally designed PFPBPF‐4‐QA, with a suitable ion exchange capacity, shows high ionic conductivity, mechanical properties, alkaline stability, and stronger membrane‐ionomer contact properties at the catalyst layers. A single AEMWE cell using PFPBPF‐4‐QA demonstrated a voltage decay rate of 2 mV kh −1 at 1.0 A cm −2 , which is significantly lower than that reported for AEMWEs and Nafion‐based PEMWEs. Additionally, a large‐sized 1‐cell AEMWE stack utilizing PFPBPF‐4‐QA with an active area of 63.6 cm 2 achieved an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh −1 for 2 000 h, with over 90% of the initial efficiency maintained for over 49 095 h based on an exponential fitting calculation.