Fabrication of a High-Stability Cross-Linked Quaternized Poly(epichlorolydrin)/PTFE Composite Membrane via a Facile Route

A novel cross-linked quaternized composite anion-exchange membrane based on poly(epichlorohydrin) (PECH) was prepared by a facile route. First, PECH was cross-linked with 2-methylimidazole and combined with a poly(tetrafluoroethylene) (PTFE) membrane to form cross-linked PECH/PTFE (CPECH/PTFE). Then, CPECH/PTFE was quaternized by 1-methylimidazole to obtain cross-linked quaternized PECH/PTFE (CQPECH/PTFE). 1H NMR and Fourier transform infrared spectroscopic data indicated that CQPECH was successfully synthesized, and the CQPECH/PTFE membrane had a dense and homogeneous structure demonstrated by the field-emission scanning electron microscopy. The results showed that the use of 2-methylimidazole as the cross-link agent could avoid the solubility of the composite membrane in water and dimethyl sulfoxide. With an increase of 2-methylimidazole, the solubility of the PECH ionomer was decreased. M-3, one of the CQPECH/PTFE membranes, showed good thermal properties (stable below 250 °C under an N2 atmosphere), excellent mechanical strength (a tensile strength of 67.3 MPa), moderate water uptake of 45.3%, and very low swelling degree of 9.01% at 30 °C. Besides, M-3 showed a hydroxide conductivity of up to 27 mS/cm and good long-term stability in a 1 M KOH solution at 60 °C for 15 days. In addition, a single H2/O2 fuel-cell test using M-3 at 50 °C indicated a peak power density of 23 mW/cm2. These results suggested that the CQPECH/PTFE membrane had a good perspective for application in an alkaline fuel cell.