Highly Durable Ether-Free Polyfluorene-Based Anion Exchange Membranes for Fuel Cell Applications

The preparation of anion exchange membranes (AEMs) with excellent chemical and dimensional stability and high conductivity faces several challenges. In the present work, a novel ether-free durable polyfluorene (PF) without fluorine-bearing pendant piperidinium groups was synthesized by the Suzuki cross-coupling reaction. Alkyl groups were introduced into the backbone of PF to enhance the solubility and flexibility of PF-based AEMs, and the transparent and flexible polymer membrane showed a high conductivity of 80.44 mS cm^-1 and excellent alkaline stability in 2 M KOH solution at 80 °C. Although the membrane possesses a high ion exchange capacity (IEC) (2.49 mequiv g^-1), it exhibits a low swelling ratio (9.4% at 80 °C), excellent mechanical properties, and dimensional stability. The H₂/O₂ single cell assembled with PFPE-Pi exhibited a maximum power density of 661 mW cm^-2 at a current density of 1280 mA cm^-2 at 80 °C. The present work provides a simple and effective strategy for the preparation of ether-free polyfluorene-based AEMs with high conductivity, excellent mechanical properties, and dimensional stability for application in alkaline fuel cells.