Layered Double Hydroxides as the Unique Product of Target Ionic Construction for Energy, Chemical, Foods, Cosmetics, Medicine and Ecology Applications

Layered Double Hydroxide (LDH) is an α-modification of the M-host (M2+ ) hydroxide, in which some part of the M-host cations is replaced by M-guest cations (M3+ or M4+ ). The emerging excess positive charge is compensated by the intercalation of anions into the interlayer space, which also contains water molecules. LDHs exhibit anion exchange properties. Targeted ionic design of LDHs via combining three components (M-host, M-guest cations, intercalated anions) allows the creation of a very wide range of highly efficient electrochemical, electrocatalytic, electrochromic substances, catalysts, ion exchangers, sorbents, color pigments, pharmacological drugs, food, and cosmetic additives. In this review, the structure and areas of application of LDHs are considered from the perspective of the targeted ionic design of a substance for a specific application.

Synthesis of Carbon-Supported PdIrNi Catalysts and Their Performance towards Ethanol Electrooxidation

Direct ethanol fuel cells (DEFCs) have shown a high potential to supply energy and contribute to saving the climate due to their bioethanol sustainability and carbon neutrality. Nonetheless, there is a consistent need to develop new catalyst electrodes that are active for the ethanol oxidation reaction (EOR). In this work, two C-supported PdIrNi catalysts, that have been reported only once, are prepared via a facile NaBH₄ co-reduction route. Their physiochemical characterization (X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)) results show alloyed PdIrNi nanoparticles that are well dispersed (<3 nm) and exist in metallic state that is air-stable apart from Ni and, slightly, Pd. Their electrocatalytic activity towards EOR was evaluated by means of cyclic voltammetry (CV) and chronoamperometry (CA). Even though the physiochemical characterization of PdIrNi/C and Pd₄Ir₂Ni₁/C is promising, their EOR performance has proven them less active than their Pd/C counterpart. Although the oxidation current peak of Pd/C is 1.8 A/mgPd, it is only 0.48 A/mgPd for Pd₄Ir₂Ni₁/C and 0.52 A/mg_Pd for PdIrNi/C. These results were obtained three times and are reproducible, but since they do not add up with the sound PdIrNi microstructure, more advanced and in situ EOR studies are necessary to better understand the poor EOR performance.

A new synthetic route for the preparation of [Os3(CO)10(μ-OH)(μ-H)] and its reaction with bis(diphenylphosphino)methane (dppm): syntheses and X-ray structures of two isomers of [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] and [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)]

The triosmium cluster [Os3(CO)10(μ-OH)(μ-H)] containing bridging hydride and hydroxyl groups at a common Os-Os edge was obtained in good yield (ca. 75%) from the hydrolysis of the labile triosmium cluster [Os3(CO)10(NCMe)2] in THF at 67 °C. [Os3(CO)10(μ-OH)(μ-H)] reacts with dppm at 68 °C to afford the isomeric clusters 1 and 2 with the general formula [Os3(CO)8(μ-OH)(μ-H)(μ-dppm)] that differ by the disposition of bridging dppm ligand. Cluster 1 is produced exclusively from the reaction of [Os3(CO)10(μ-OH)(μ-H)] with dppm in CH2Cl2 at room temperature in the presence of added Me3NO. Heating cluster 1 at 81 °C furnishes 2 in a process that likely proceeds by the release of one arm of the dppm ligand, followed by ligand reorganization about the cluster polyhedron and ring closure of the pendent dppm ligand. The oxo-capped [Os3(CO)7(μ3-CO)(μ3-O)(μ-dppm)] (3) has been isolated starting from the thermolysis of either 1 or 2 at 139 °C. Reactions of [Os3(CO)10(μ-dppm)] with ROH (R = Me, Et) in the presence of Me3NO at 80 °C furnish [Os3(CO)8(μ-OH)(μ,η1,κ1-OCOR)(μ-dppm)] (4, R = Me; 5, R = Et). Clusters 1-5 have been characterized by a combination of analytical and spectroscopic studies, and the molecular structure of each product has been established by X-ray crystallography. The bonding in these products has been examined by electronic structure calculations, and cluster 1 is confirmed as the kinetic product of substitution, while cluster 2 represents the thermodynamically favored isomer.