Effect of LDH platelets on the transport properties and carbonation of anion exchange membranes

Abstract

We report on an extensive study on nanocomposite Anion Exchange Membranes (AEMs) based on tetramethylammonium Polysulfone ionomer and Layered Double Hydroxide (LDH) as nanofiller. The AEMs were investigated in both OH− and HCO3− forms, comparing swelling capacity and transport properties. Ionic conductivity measurements were performed both by Electrochemical Impedance Spectroscopy and Ziv and Dekel's method, while the water and ions mobility by 1H Pulse Field Gradient (PFG) NMR spectroscopy.One of the most serious problems to be addressed in AEMs fuel cell technology is that of the significant loss of performance when CO2 is present in the reaction oxidant gas (e.g., air) due to the phenomenon of carbonation. In this work, the carbonation kinetics of AEMs and the effect of LDH filler were addressed through 13C NMR spectroscopy (including diffusometry and relaxometry measurements). The presence of LDH platelets in the AEM significantly reduces the conversion rate of hydroxide groups. The interaction between the polymer chains and the anionic clay lamellae creates a suitable network that benefits the membrane's ionic conductivity, its mechanical properties (DMA tests), and finally reduces the rate of alkaline degradation.