Synthesis and Characterization of Composite Anion Exchange Membranes (AEM) Using Layered Double Hydroxides (LDH) with Ionic Liquids (IL) and Metal Organic Framework (MOF)

Abstract

Anion Exchange Membranes (AEM) are used in alkaline fuel cells, electrolysers and redox-flow batteries. The main disadvantage of AEM is the degradation of the ionomer in basic conditions and high temperature. The formation of composite offers several advantages, such as enhanced hydrolytic stability and improved mechanical properties. The composite anion-conducting membranes were made by dispersion of Mg/Al layered double hydroxide (LDH) in the polymeric matrix made by polysulfone (PSU) grafted with trimethylamine (TMA) and 1,4-diazabicyclo[2.2.2]octane (DABCO) [1]. They presented a reduced swelling and the mechanical properties in fully humidified conditions were enhanced. Furthermore, the membranes can be treated in alkaline conditions at 60 °C without losing their properties. The Zn/Al and Mg/Al LDH were also modified by adding ionic liquids (IL) in the inter-lamellar space showing an improved ionic conductivity (Figure 1) [2]. The LDH-IL fillers were added to PSU-DABCO and poly(2,6-dimethyl-1,4-phenylene)oxide DABCO (PPO-DABCO) membranes, the resulting properties were studied. For the composite with metal organic frameworks (MOF) we used UiO-66 [3], consisting of a cluster of [Zr6O4(OH)4] and 1,4-benzodicarboxylic-NH2, preliminary studies were achieved. Figure 1: Schematic of PSU-DABCO-LDH-IL (ZnAl- 1-butyl-3-methylimidazolium hydrogen sulphate).