Novel Alkaline Anion-exchange Membranes Based on Chitosan/Ethenylmethylimidazoliumchloride Polymer with Ethenylpyrrolidone Composites for Low Temperature Polymer Electrolyte Fuel Cells

Novel alkaline anion-exchange membranes composed of chitosan (CS) and 1-Ethenyl-3-methyl-1H-imidazoliumchloride polymer with 1-ethenyl-2-pyrrolidone (abbreviated as EMImC-Co-EP) are prepared by a combined thermal and chemical cross-linking technique. The hydroxide conductivity (σ_OH-), water uptakes, ion exchange capacity (IEC), thermal stability, mechanical property, oxidative stability and alkaline stabilities of CS/EMImC-Co-EP membranes are measured to evaluate their applicability in H₂/O₂ alkaline fuel cells (FC). The effects of thermal cross-linking temperature and membrane composition on membrane OH^- conductivity are studied using AC impedance technique. FTIR, SEM and TG analysis are used for structural characterization of these membranes. It is found that the OH^- conductivity of the membranes increases with temperature and exceeds 10^-2 S cm^-1 at 80 °C. The CS/EMImC-Co-EP membranes show excellent thermal stability with onset degradation temperature high above 200 °C. In particular, the high alkaline stability is achieved for the CS/EMImC-Co-EP membranes in hot 8.0 M KOH at 85 °C without losing their integrity and OH^- conductivity during 300 hours of evaluation, and also a relatively high oxidative stability. The membrane electrode assembly (MEA) fabricated with CS/EMImC-Co-EP (1:0.5 by mass) gives an initial power density of 21.7 mW cm^-2 using H₂ as the fuel and O₂ as oxidant at room temperature, on a low metal loading on both the anode and the cathode of 0.5 mg (Pt) cm^-2 at ambient temperature.