Layered Double Hydroxides Containing an Ionic Liquid: Ionic Conductivity and Use in Composite Anion Exchange Membranes

Abstract

Zinc-aluminum layered double hydroxide (LDH) containing an ionic liquid, 1-butyl-3-methylimidazolium hydrogen sulfate (BmimSO 4 ), has been synthesized by a co-precipitation method. This strategy enabled the intercalation of the ionic liquid (IL) into the interlamellar space of LDH with the aim of increasing the ionic conductivity and reducing its dependence on water content. Pure and IL-intercalated LDHs have been characterized by Fourier-Transform Infrared (FTIR) spectroscopy and X-ray diffraction. Electrochemical Impedance Spectroscopy (EIS) measurements showed that the addition of IL enhanced the ionic conductivity of LDH by a factor of 15 at low humidity and by a factor of 9 at high humidity conditions. As a possible application, LDHs were dispersed as a guest filler in a composite anion exchange membrane (AEM) based on polysulfone-DABCO. In this case, the addition of IL remarkably improved the ionic conductivity of the membrane from 1.0 · 10 À9 to 2.4 · 10 À7 S/ cm at low humidity. At high humidity, the membranes reached a conductivity of 25 mS/cm at 25 8C in OH form. Stability tests of composite AEM confirmed the positive effect of LDH nanoparticles. Figure 1. Chemical formulas of a) LDH and b) 1-Butyl-3-methylimidazolium hydrogen sulfate (BmimSO 4 ).

Adsorption of heavy metals by layered double hydroxides grown in situ on Al foam

“…SEM micrographs of the LDH‐coated aluminum foam taken at different magnifications are shown in Figure 1B–D. The LDH coating presents the typical nanostructured morphology previously reported 12–14 using similar growth methods on thick aluminum foils. The aluminum surface is covered by the uncontrolled overgrowth of LDH nanoleaves, with a typical thickness of around 100 nm, which grow from screw dislocations of the basal nanoplatelets 14 …”

“…Zn-Al LDH coatings were grown on aluminum foam with approximate dimensions of 2 × 2 × 2 cm 3 (see Figure 1A), using a standard method for hydrothermal in-situ growth of LDH films. [12][13][14] All the chemicals used for LDH synthesis were purchased from Sigma-Aldrich and were used without further purification. Before immersion in the nutrient solution for LDH growth, the aluminum foams were cleaned with a 0.5% aqueous NaOH solution for 1 min in order to remove the oxide layer on the surface and then pretreated ultrasonically in deionized water and in ethanol for As it is shown in Figure 3, the signal of Cu 2p 3/2 was detected in both focal points of the sample, and this result proves that the copper ions are permeated inside the foam.…”

“…Zn‐Al LDH coatings were grown on aluminum foam with approximate dimensions of 2 × 2 × 2 cm 3 (see Figure 1A), using a standard method for hydrothermal in‐situ growth of LDH films 12–14 . All the chemicals used for LDH synthesis were purchased from Sigma‐Aldrich and were used without further purification.…”

Ionic Liquids as Delaminating Agents of Layered Double Hydroxide during In-Situ Synthesis of Poly (Butylene Adipate-co-Terephthalate) Nanocomposites

“…Besides the IL-anions, the presence of carbonate anions in all of the modified LDH (as well as in the pristine LDH) was confirmed by the FTIR band at ca 1360 cm −1 (Figure 1) [31]. The direct synthesis was found to be highly efficient and led to preparation of LDH with a much higher content of organic anions (see the TGA results bellow) compared to the regeneration method published in our last study [22].…”

Effect of Al substrate microstructure on layered double hydroxide morphology

“…Layered double hydroxides (LDHs) are 2D ionic lamellar materials [1,2]. These materials are quite interesting for industrial and medical applications owing to the possibility to exchange water molecules and several complex organic molecules within the inter-lamellar space [3]. LDHs have been employed as energy harvesting and conversion [4], anticorrosion coatings [2,5,6], catalysis [7], water treatment and purification [7], super hydrophobic surfaces [1], biomedical applications such as drug delivery and biosensors [8,9] and nanostructured-modified textiles [9].…”