Fluorine‐Containing Poly(Fluorene)‐Based Anion Exchange Membrane with High Hydroxide Conductivity and Physicochemical Stability for Water Electrolysis

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-08, Vol.20 (32), p.e2400031-n/a
• Main Authors: Lim, Haeryang, Han, Gyeong Ho, Lee, Dae Hwan, Shin, Giwon, Choi, Jinhyuk, Ahn, Sang Hyun, Park, Taiho
• Format: Article
• Language: English
• Subjects: anion exchange membrane; Anion exchanging; aryl ether‐free polymer; Atomic structure; Commercialization; Dimensional stability; Electrolysis; Fluorine; fluorine‐containing structure; Glass transition temperature; Ion transport; Iron compounds; Membranes; morphology; Nickel compounds; Phase separation; Platinum metals; water electrolysis
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202400031

Improving the hydroxide conductivity and dimensional stability of anion exchange membranes (AEMs) while retaining their high alkaline stability is necessary to realize the commercialization of AEM water electrolysis (AEMWE). A strategy for improving the hydroxide conductivity and dimensional stability of AEMs by inserting fluorine atoms in the core structure of the backbone is reported, which not only reduces the glass transition temperature of the polymer due to steric strain, but also induces distinct phase separation by inducing polarity discrimination to facilitate the formation of ion transport channels. The resulting PFPFTP‐QA AEM with fluorine into the core structure shows high hydroxide conductivity (>159 mS cm−1 at 80 °C), favorable dimensional stability (>25% at 80 °C), and excellent alkaline stability for 1000 h in 2 m KOH solution at 80 °C. Moreover, the PFPFTP‐QA is used to construct an AEMWE cell with a platinum group metal (PGM)–free NiFe anode, which exhibits the current density of 6.86 A cm−2 at 1.9 V at 80 °C, the highest performance in Pt/C cathode and PGM‐free anode reports so far and operates stably for over 100 h at a constant current of 0.5 A cm−2. The novel poly(fluorene)‐based PFPFTP‐QA AEM containing fluorine atoms in the terphenyl core structure is reported. PFPFTP‐QA is the first poly(fluorene)‐based AEM that simultaneously demonstrates excellent mechanical properties, alkaline stability, favorable dimensional stability, and satisfactory hydroxide conductivity. Moreover PFPFTP‐QA‐based water electrolysis cell using a PGM‐free anode achieves a current density of 6.86 A cm−2 at 1.9 V.