Synthesis and characterization of layered double hydroxides with different cations (Mg, Co, Ni, Al), decomposition and reformation of mixed metal oxides to layered structures

Abstract

Three layered double hydroxides (LDH) [Mg1−xAlx(OH)2]x+(Am−)x/m]·nH2O and [MII 1−xMIII x (OH)2]x+(Am−)x/m]·nH2O (MII — Mg, Co, Ni; MIII — Al; A — CO3 2−) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of large particles with sharp edges along with a large amount of smaller particles

Highly active layered double hydroxide-derived cobalt nano-catalysts for p-nitrophenol reduction

“…Cobalt nanoparticles supported on layered double oxide nanodisks are prepared by thermal phase transformation [6,29,30,[43][44][45], involving two critical steps as illustrated in Figure S1 for no voids in LDH). XRD confirms that LDH has a hydrotalcite structure [14], as shown in Figure 1f.The XRD peaks for LDH are sharp, suggesting a LDH crystal can be as large as a single disk with micrometers in size.…”

Structure of oxides prepared by decomposition of layered double Mg–Al and Ni–Al hydroxides

“…XRD pattern of Mg-Al oxide calcined at 450-700 о С contains peaks of periclase-like phase with smaller interplanar spacings as compared to MgO and broad additional peak with maximum corresponding to interplanar distance in the range of 2.53−2.56 Å. In the most of the works description of the oxide structure come to nothing more than either MgO (periclase, NaCl structure type, space group Fm3m) or periclase-like structure modified by Al 3+ [8,9]. For example, with use of Rietveld refinement authors [10] determined that structure is periclase-like with substitution of Mg 2+ by Al 3+ ions.…”

Ammonium alcohol polyvinyl phosphate intercalated LDHs/epoxy nanocomposites

“…The spectrum of AAPP sample (Fig. 3a) shows -NH (3419 and 1409 cm -1 ), -OH (3126 cm -1 , hydrate complex), -C=O (1637 cm -1 ), C-O-P (1294 and 543 cm -1 ) and P-O (1087 cm -1 ) groups [17], indicating the presence of carbonate in the sample. The spectrum of LDHs-0 sample (Fig.…”

“…As shown in Fig. 2, the typical diffraction peaks at (003), 006), (009), (015), (018), (110) and (113) belong to LDHs (JCPDS22-0700) [17]. The LDHs are a mixture of hydroxide and carbonate.…”