Alkaline Stability of Anion-Exchange Membranes

Sapir Willdorf-Cohen; Avital Zhegur-Khais; Julia Ponce-González; Saja Bsoul-Haj; John R Varcoe; Charles E Diesendruck; Dario R Dekel

doi:10.1021/acsaem.2c03689

Alkaline Stability of Anion-Exchange Membranes

ACS Appl Energy Mater. 2023 Jan 9;6(2):1085-1092. doi: 10.1021/acsaem.2c03689. eCollection 2023 Jan 23.

Authors

Sapir Willdorf-Cohen¹, Avital Zhegur-Khais¹, Julia Ponce-González², Saja Bsoul-Haj¹, John R Varcoe², Charles E Diesendruck^{3

4}, Dario R Dekel^{1

4}

Affiliations

¹ The Wolfson Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa3200003, Israel.
² School of Chemistry and Chemical Engineering, University of Surrey, GuildfordGU2 7XH, U.K.
³ Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa3200003, Israel.
⁴ The Nancy & Stephen Grand Technion Energy Program (GTEP), Technion-Israel Institute of Technology, Haifa3200003, Israel.

Abstract

Recently, the development of durable anion-exchange membrane fuel cells (AEMFCs) has increased in intensity due to their potential to use low-cost, sustainable components. However, the decomposition of the quaternary ammonium (QA) cationic groups in the anion-exchange membranes (AEMs) during cell operation is still a major challenge. Many different QA types and functionalized polymers have been proposed that achieve high AEM stabilities in strongly alkaline aqueous solutions. We previously developed an ex situ technique to measure AEM alkaline stabilities in an environment that simulates the low-hydration conditions in an operating AEMFC. However, this method required the AEMs to be soluble in DMSO solvent, so decomposition could be monitored using ¹H nuclear magnetic resonance (NMR). We now report the extension of this ex situ protocol to spectroscopically measure the alkaline stability of insoluble AEMs. The stability ofradiation-grafted (RG) poly(ethylene-co-tetrafluoroethylene)-(ETFE)-based poly(vinylbenzyltrimethylammonium) (ETFE-TMA) and poly(vinylbenzyltriethylammonium) (ETFE-TEA) AEMs were studied using Raman spectroscopy alongside changes in their true OH^- conductivities and ion-exchange capacities (IEC). A crosslinked polymer made from poly(styrene-co-vinylbenzyl chloride) random copolymer and N,N,N',N'-tetraethyl-1,3-propanediamine (TEPDA) was also studied. The results are consistent with our previous studies based on QA-type model small molecules and soluble poly(2,6-dimethylphenylene oxide) (PPO) polymers. Our work presents a reliable ex situ technique to measure the true alkaline stability of AEMs for fuel cells and water electrolyzers.