A novel aqueous synthesis of anion exchange membranes for fuel cells

This work reports an eco-friendly, economical, and straightforward fabrication of chitosan (CS)/poly(diallyldimethylammonium chloride) (PDDA) blended anion exchange membranes via an aqueous processing strategy, where CS dissolved in a KOH/urea/H₂O system forms the polymer matrix and PDDA acts as the hydroxide-ion conductor. Membranes are cast from solution and neutralized in KCl(aq) to form a gel film, followed by dehydration to form films. Robust hydrogen bond cross-linking facilitates lateral aggregation of chitosan chains, ensuring excellent component compatibility, low in-plane swelling (4.3–10.3 % at 80 °C), and favorable mechanical properties. The inherent hydrophilicity of CS and PDDA, imparts high through-plane swelling (45.0–150.1 % at 80 °C) and water uptake (142.5–327.2 % at 80 °C). High water uptake facilitates improved hydroxide conductivity (22.6–41.2 mS cm⁻¹ at 80 °C) and significantly enhances alkaline stability in hot KOH solutions (mass retention: 79.3–88.6 %; IEC retention: 70.6–73.9 %; conductivity retention: 76.8–86.1 %). The optimized PDDA@CS_7.0%-2 membrane achieves a peak power density of 180.0 mW cm⁻² at 325.2 mA cm⁻², demonstrating competitive performance among CS or PDDA-based AEMs.