A Poly(terphenyl quinuclidinium) Anion Exchange Membrane with Hydrophilic Crown Ether Units for Water Electrolysis

Poly(aryl quinuclidinium) polymers have increasingly gained attention due to their superior alkaline stability. In this work, we synthesized poly(aryl quinuclidinium) (PTCQ) AEMs that incorporate hydrophilic crown ether units within their main chains through the reaction of dibenzo-18-crown-6 with p-terphenyl and quinoline-2,3-dione hydrochloride under superacid catalysis. At 80 °C, the hydroxide conductivity of PTCQ-10 reaches as high as 185 mS cm−1. An appropriate amount of crown ether units also enables the membrane to achieve an elongation at break exceeding 25%, along with high water absorption and improved dimensional stability (WU 28.95%, SR 6.31% at 80 °C). Moreover, compared to aryl ethers that compromise the membrane's alkaline stability, the PTCQ-10 membrane incorporating crown ether units exhibited negligible conductivity loss after 3000 h of testing in 5 M KOH. In an AEMWE system utilizing a nickel alloy foam catalyst, after stable operation for 2000 h at 0.5 and 1.0 A cm−2 in 5 M NaOH solution at 80 °C, the membrane's chemical structure remains fully preserved. The results above indicate that AEMs incorporating hydrophilic crown ether units into the polymer backbone demonstrate potential for application in AEM-based electrochemical devices.