(42z) Preparing Alkaline Anion Exchange Membrane with Enhanced Hydroxide Conductivity Via Blending Imidazolium-Functionalized and Sulfonated Poly(ether ether ketone)

The development of alkaline anion exchange membrane (AEM) with both high ion conductivity and stabilities is of great significance for fuel cell applications. The ion conductivity of AEM is usually governed by three factors: 1) the amount of charge carriers in unit volume (IEC); 2) the ionic mobility of charge carriers; and 3) the morphology of ion channels. The low ion conductivity of AEM comes from the low inherent hydroxide ion mobility ratio, which is far lower than that of proton. Increasing the IEC of membrane has been demonstrated as a feasible way to enhance the hydroxide conductivity of AEMs. When utilized as the matrix of AEMs, most of functional polymers exhibited a positive correlation between IEC and hydroxide conductivity. In this study, a facile acid-base blending method is designed to improve AEM performances via increasing the IEC of membranes. Basic imidazolium-functionalized poly (ether ether ketone) with a high functionalization degree is employed as polymer matrix to pursue IEC as well as high hydroxide conductivity, meanwhile acidic sulfonated poly (ether ether ketone) (SPEEK) is employed as the cross-linking agent to enhance the stabilities of the blend membranes. Particularly, an in-situ Menshutkin/crosslinking method is exploited to prevent the flocculation in the preparation process of blend membranes. As a result, dense and defect-free blend membranes are obtained. The blend membranes exhibit high level of IEC up to 3.15 mmol g⁻¹, and consequently possess elevated hydroxide conductivity up to 31.59 mS cm⁻¹ at 30 °C. In addition, benefiting from the strong electrostatic interaction introduced by the acid-base blending, the stabilities and methanol resistance of blend membranes are enhanced.