Synthesis of finely disperse nickel particles by thermolysis of complex (N<Subscript>2</Subscript>H<Subscript>5</Subscript>)[Ni(NH<Subscript>2</Subscript>NHCOO)<Subscript>3</Subscript>] · H<Subscript>2</Subscript>O in organic liquids and refinement of crystal structure of this complex

The crystal structure of the complex (N₂H₅)[Ni(NH₂NHCOO)₃] · H₂O (I) was refined using X-ray diffraction data (obtained on an Apex X8 diffractometer, MoK _α radiation, 1830 F _hkl , R = 0.0182). The structure is built of complex anions [Ni(NH₂NHCOO)₃]⁻, cations N₂H₅⁺, and water molecules and is characterized by strong hydrogen bonds N-H…O, O-H…O, and N-H…N. The N₃O₃ coordination polyhedron around a Ni atom is a slightly distorted octahedron. The thermal decomposition of complex I was studied in high-boiling organic liquids. The feasibility of preparing non-pyrophoric nickel powders having particle sizes of up to 20 nm is shown.     

Crystal structure of [(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>P][Ni(B<Subscript>9</Subscript>C<Subscript>2</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]·CCl<Subscript>4</Subscript>

A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C₆H₅)₄P][Ni(B₉C₂H₁₁)₂]·CCl₄, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C₂₉H₄₂B₁₈PCl₄Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) ų, Z = 2, d _calc = 1.348 g/cm³. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R ₁ = 0.0466 for 3055 I _hkl ≥ 2σ _I of 23,655 reflections collected and 5618 independent I _hkl (Bruker X8 APEX diffractometer, λMoK _α).     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

Study of Acidic (Tetracaprolactam) Dodecamolybdosilicate of the Composition (C<Subscript>6</Subscript>H<Subscript>11</Subscript>NO)<Subscript>4.5</Subscript>Н<Subscript>4</Subscript>[SiМо<Subscript>12</Subscript>O<Subscript>40</Subscript>]

New caprolactam dodecamolybdosilicate of the composition (C₆H₁₁NO)_4.5Н₄[SiМо₁₂O₄₀] (I) is synthesized. Chemical and crystallographic analyses, NMR and IR spectroscopic studies are performed. Compound I is found to crystallize in the monoclinic system with the space group P2₁/n. Unit cell parameters are: a = 19.945(4) Å, b = 13.340(3) Å, c = 28.110(6) Å, β = 110.75(3)°, ρ_calc = 2.232 g/cm³, М = 2350.63, Z = 4, V = 6994(3) ų.     

Crystal Structure of Mononuclear Non-Heme Nikel(II) Octahedral Complex: [Ni(bqenH<Subscript>2</Subscript>)(bpy)](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>·0.125H<Subscript>2</Subscript>O

The crystal structure of a mononuclear Ni(II) complex [Ni(bqenH₂)(bpy)](ClO₄)₂·0.125H₂O 1 (where bqenH₂ is N,N′-bis(8-quinolyl)ethane-1,2-diamine, bpy = 2,2′-bipyridine) is reported here. The crystallographic data for 1 are as follows: monoclinic crystal system, P2_1/n space group, a = 17.3255(11), b = 10.6110(7), c = 34.328(2) Å, α = 90°, β = 93.9480(13)°, γ = 90°, V = 6295.8(7) ų, Z = 4, d_x = 1.541 mg/m³. The nickel(II) ion coordinates four N atoms of the tetradentate ligand bqenH₂ and two N atoms of the auxiliary bidentate 2,2′-bipyridine ligand, resulting in a slightly distorted NiN6 octahedron with two perchlorates serving as charge balancing counter anions. The overall structure of 1 is stabilized by the presence of water of crystallization in the crystal lattice. The crystal structure shows two symmetrically identical octahedral NiN6 units in its asymmetric unit. The extensive hydrogen bonding network resulting in a supramolecular architecture is observed due to the N–H?O, O–H?O, O–H?Cl, and N–H?Cl interactions.     

Reduction of Oxide Mixtures of (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + CuO) and (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> + Co<Subscript>3</Subscript>O<Subscript>4</Subscript>) by Low-Temperature Hydrogen Plasma

The paper presents experimental results pertaining to the reduction of oxide mixtures namely (Fe₂O₃ + CuO) and (Fe₂O₃ + Co₃O₄), by low-temperature hydrogen plasma in a microwave hydrogen plasma set-up, at microwave power 750 W and hydrogen flow rate 2.5 × 10^?6 m³ s^?1. The objective was to examine the effect of addition of CuO or Co₃O₄, on the reduction of Fe₂O₃. In the case of the Fe₂O₃ and CuO mixture, oxides were reduced to form Fe and Cu metals. Enhancement of reduction of iron oxide was marginal. However, in the case of the Fe₂O₃ and Co₃O₄ mixture, FeCo alloy was formed within compositions of Fe₇₀Co₃₀, to Fe₃₀Co₇₀. Since the temperature was below 841 K, no FeO formed during reduction and the sequence of Fe₂O₃ reduction was found to be Fe₂O₃ → Fe₃O₄ → Fe. Reduction of Co₃O₄ preceded that of Fe₂O₃. In the beginning, the reduction of oxides led to the formation of Fe–Co alloy that was rich in Co. Later Fe continued to enter into the alloy phase through diffusion and homogenization. The lattice strain of the alloy as a function of its composition was measured. In the oxide mixture in which excessive amount of Co₃O₄ was present, all the Co formed after reduction could not form the alloy and part of it appeared as FCC Co metal. The crystallite size of the alloy was in the range of 22–30 nm. The crystal size of the Fe–Co alloy reduced with an increase in Co concentration.     

Hydrothermal synthesis and crystal structure of a novel nickel(II) complex: [Ni(H<Subscript>2</Subscript>Bibzim)<Subscript>3</Subscript>Cl<Subscript>2</Subscript> · 2H<Subscript>2</Subscript>O] (H<Subscript>2</Subscript>Bibzim = 2,2-Bibenzimidazole)

A novel organic-inorganic hybrid compound based on weak intermolecular interactions formulated as Ni(H₂Bibzim)₃Cl₂ · 2H₂O (H₂Bibzim = 2,2-bibenzimidazole, formula, C₁₄H₁₀N₄) has been synthesized under hydrothermal conditions and characterized by elemental analysis, single-crystal X-ray diffraction analyses, and IR spectra. It crystallizes in the orthorhombic system, space group Pbcn, Z = 2, a = 20.8530(19), b = 15.7838(14), c = 12.3159(11) Å, V = 4053.7(6) ų, M _r = 1736.84, ρ_c = 1.423g/cm³, λ = 0.71073 Å, μ(MoK _α) = 0.664 mm^?1, F(000) = 1792, R = 0.0283 and wR = 0.0707 for 3746 observed reflections with I > 2σ(I). The complex is composed of mononuclear cations [Ni(H₂Bibzim)₃]²⁺, chlorine anions, and lattice water molecules, which are linked into a two-dimensional supramolecular architectures via hydrogen bonds and π-π-stacking interactions.     

Hydrogen Production by Steam Reforming of Ethanol Over Mesoporous Ni–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> Catalysts

This review paper reports the recent progress concerning the application of nickel–alumina–zirconia based catalysts to the ethanol steam reforming for hydrogen production. Several series of mesoporous nickel–alumina–zirconia based catalysts were prepared by an epoxide-initiated sol–gel method. The first series comprised Ni–Al₂O₃–ZrO₂ xerogel catalysts with diverse Zr/Al molar ratios. Chemical species maintained a well-dispersed state, while catalyst acidity decreased with increasing Zr/Al molar ratio. An optimal amount of Zr (Zr/Al molar ratio of 0.2) was required to achieve the highest hydrogen yield. In the second series, Ni–Al₂O₃–ZrO₂ xerogel catalysts with different Ni content were examined. Reducibility and nickel surface area of the catalysts could be modulated by changing nickel content. Ni–Al₂O₃–ZrO₂ catalyst with 15 wt% of nickel content showed the highest nickel surface area and the best catalytic performance. In the catalysts where copper was introduced as an additive (Cu–Ni–Al₂O₃–ZrO₂), it was found that nickel dispersion, nickel surface area, and ethanol adsorption capacity were enhanced at an appropriate amount of copper introduction, leading to a promising catalytic activity. Ni–Sr–Al₂O₃–ZrO₂ catalysts prepared by changing drying method were tested as well. Textural properties of Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst produced from supercritical drying were enhanced when compared to those of xerogel catalyst produced from conventional drying. Nickel dispersion and nickel surface area were higher on Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst, which led to higher hydrogen yield and catalyst stability over Ni–Sr–Al₂O₃–ZrO₂ aerogel catalyst.     

Synthesis of nanopowders and physicochemical properties of ceramic matrices of the LaPO<Subscript>4</Subscript>–YPO<Subscript>4</Subscript>–(H<Subscript>2</Subscript>O) and LaPO<Subscript>4</Subscript>–HoPO<Subscript>4</Subscript>–(H<Subscript>2</Subscript>O) systems

Sol-gel method was used to synthesize nanosize powders in the LaPO₄–YPO₄–(H₂O) and LaPO₄–HoPO₄–(H₂O) systems. Dense ceramic samples with high microhardness (up to 25 GPa) were formed from these powders by sintering at temperatures of up to 1600°C. The isomorphic capacity of the monoclinic LaPO₄ matrix for the second component (yttrium or holmium) simulating radioactive nuclides of the actinide-rare-earth fraction was found to be high. The composites are stable in aqueous solutions, which is indicated by the low concentration of lanthanum and yttrium ions during leaching test (~10^–7 g L^–1). The results obtained in the study can be used to develop new high-efficiency ceramic matrices for solidification of the actinide-rare-earth fraction of liquid wastes formed in processing of the spent nuclear fuel.     

Synthesis and spectral studies on NiS<Subscript>4</Subscript>, NiS<Subscript>2</Subscript>PN,NiS<Subscript>2</Subscript>P<Subscript>2</Subscript> chromophores: Single-crystal X-ray structure of [Ni(dbpdtc)<Subscript>2</Subscript>] (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate)

Three complexes of a dithiocarbamate ligand (dbpdtc = benzyl(4-(benzylamino)phenyl)dithiocarbamate), namely [Ni(dbpdtc)₂] (1), [Ni(dbpdtc)(NCS)(PPh₃)] (2) and [Ni(dbpdtc)(PPh₃)₂]ClO₄ (3) have been prepared. The complexes were characterized by IR, electronic spectroscopy and cyclic voltammetry. A single-crystal X-ray structural analysis was carried out for complex 1 and showed that the nickel is in a distorted square planar environment with a NiS₄ chromophore. For the two mixed ligand complexes, the thioureide ν _C–N values were shifted to higher wavenumbers compared to [Ni(dbpdtc)₂], suggesting increased strength of the thioureide bond due to the presence of the π-accepting phosphine. Electronic spectral studies suggest square planar geometries for the complexes. Cyclic voltammetry showed easier reduction of nickel(II) to nickel(I) in the mixed ligand complexes compared to [Ni(dbpdtc)₂].     

Synthesis,IR-spectroscopic study and crystal structure of tris(benzohydrazide)nickel(II) dichloride dihydrate [Ni(L)<Subscript>3</Subscript>]Cl<Subscript>2</Subscript> · 2H<Subscript>2</Subscript>O

Coordination compound [Ni(L)₃]Cl₂ · 2H₂O (L is benzohydrazide) has been synthesized and studied by IR spectroscopy and X-ray diffraction analysis. According to X-ray diffraction, one of the Cl^– ions is disordered over two nonequivalent positions. The crystals are monoclinic, a = 15.423(3) Å, b = 9.697(2) Å, c = 18.893(4) Å, ß = 105.99(3)°, space group P2₁/c, Z = 4. The structural units of the crystal are complex cations [Ni(L)3]2+, in which ligands L are coordinated to the central atom bidentately chelating the metal atoms through the O and N atoms of the hydrazide moiety (Ni–O 2.036(4), 2.051(5), 2.047(5); Ni–N 2.095(5), 2.089(6), 2.097(6) Å). The structural units of the crystal are joined together by cation–anion electrostatic interactions and hydrogen bonds, which involve both H₂O molecules, both Cl^– anions and the N atoms of chelate rings of the complex cation.     

Development of a Ni–Pd/CeZrO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for the effective conversion of methane into hydrogen-containing gas

The effects of the Pd content (0–1 wt %) and the synthesis method (joint impregnation with Ni + Pd and Pd/Ni or Ni/Pd sequential impregnation) on the physicochemical and catalytic properties of Ni–Pd/CeZrO₂/Al₂O₃ were studied in order to develop an efficient catalyst for the conversion of methane into hydrogen-containing gas. It was shown that variation in the palladium content and a change in the method used for the introduction of an active constituent into the support matrix make it possible to regulate the redox properties of nickel cations but do not affect the size of NiO particles (14.0 ± 0.5 nm) and the phase composition of the catalyst ((γ + δ)-Al₂O₃, CeZrO₂ solid solution, and NiO). It was established that the activity of Ni–Pd catalysts in the reaction of autothermal methane reforming depends on the method of synthesis and increases in the following order: Ni + Pd < Ni/Pd < Pd/Ni. It was found that, as the Pd content of the Ni–Pd/CeZrO₂/Al₂O₃ catalyst was decreased from 1 to 0.05 wt %, the ability for self-activation, high activity, and operational stability of the catalyst under the conditions of autothermal methane reforming remained unaffected: at 850°C, the yield of hydrogen was ~70% at a methane conversion of ~100% during a 24-h reaction.     

Crystal structures of chiral (R/S) (C<Subscript>8</Subscript>H<Subscript>11</Subscript>N)<Subscript>2</Subscript> · Zn(OAc)<Subscript>2</Subscript>

Two opposite configuration (R/S) of chiral complexes (C₈H₁₁N)₂ · Zn(OAc)₂ (Ia and Ib—L-(−)-) and D-(+)-isomer) were synthesized by a simple one-pot method. The crystal structures of Ia and ib determined by X-ray crystallography.     

Another Structure Type of Oxotris(oxalato)niobate(V): Molecular and Crystal Structure of Rb<Subscript>3</Subscript>[NbO(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>3</Subscript>]⋅2H<Subscript>2</Subscript>O

The compound Rb₃[NbO(C₂O₄)₃]⋅2H₂O (1) has been synthesized by two different methods and its exact chemical composition established. The niobium atom is heptacoordinated by oxygen atoms forming a distorted pentagonal bipyramid. Inspite of some similarities, the structure of 1 is not isotypic with the structure of (NH₄)₃[NbO(C₂O₄)₃]⋅H₂O.     

Crystalline β Modification of (BEDT-TTF)<Subscript>2</Subscript>Br<Subscript>0.12</Subscript>Cl<Subscript>1.88</Subscript>I

The structure of the crystalline β’ modification of a radical cation salt of bis(ethylenedithio)tetrathiafulvalene with mixed dihalogen iodide (BEDT-TTF)₂Br_0.12Cl_1.88I (I) was investigated by single crystal X-ray diffraction. Triclinic structure of I (space group , a = 6.638 Å, b = 9.779 Å, c = 12.920 Å; α = 87.24°, β = 79.10°, γ = 81.37°) was solved by direct methods and refined in a full-matrix anisotropic approximation to R = 0.030 using all 3897 measured independent reflections (CAD-4 automatic diffractometer, λMoK _α). In the crystal structure of I the mixed Cl*-I-Cl* anion occupies the inversion center i(000), its terminal atom having a composition Cl* = Cl_0.94Br_0.06. The semi-radical cation (C₁₀H₈S₈)^1/2+ has one of two ethylene groups disordered.Original Russian Text Copyright © 2004 by A. N. Chekhlov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 960–965, September–October, 2004.     

A comparative study of electrocatalytic performance of the M@Pt (M = Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>, Co and Ni) nanoparticles for direct ethanol fuel cells

In this study, we have successfully synthesized the M@Pt (M = Fe₃O₄, Co and Ni) nanoparticles catalysts through the sodium borohydride reduction method for a comparative studies of their electrocatalytic performance towards ethanol oxidation in acidic media. After the structure, surface morphology and chemical composition characterization of the synthesized core–shell nanoparticles, their electrocatalytic activities towards oxidation of ethanol in acidic media were studied in detail. We investigated the effect of the core element (Fe₃O₄, Co and Ni) on the electrochemical behaviour as well as the enhancement of the electrocatalytic activity for ethanol oxidation reaction. Overall, the obtained results show that the all of these electrocatalysts exhibited an enhanced activity than Pt-alone nanoparticles towards ethanol oxidation reaction. On the other hand, the comparative studies of their electrocatalytic performance show that the Ni@Pt nanoparticles present the best performance with the maximum electrocatalytic activity and stability.     

Redox Behavior and Transport Properties of Composites Based on (Fe,Ni)<Subscript>3</Subscript>O<Subscript>4 ± δ</Subscript> for Anodes of Solid Oxide Fuel Cells

The Fe–Ni–O system designed for producing bimetal-containing composite anodes of solid oxide fuel cells (SOFCs) was studied. The solubility of nickel in the structure of spinel (Fe,Ni)₃O_{4 ± δ} at atmospheric oxygen pressure is ~1/3. Moderate reduction at 1023 K and p(O₂) ≈ 10^–20 atm leads to partial decomposition of spinels, forming an electron-conducting phase (Fe,Ni)_1–yO and submicron bimetallic Fe–Ni particles on the oxide surface, which have potentially high catalytic activity. The electron conductivity has a thermally activated character and increases substantially during the reduction. In the anode conditions of SOFCs, the electric conductivity reaches 30–100 S/cm, while the thermal expansion coefficients are ~12 × 10^–6 K^–1, which ensures compatibility with solid electrolytes. At the same time, significant volume changes during the redox cycling (up to ~1% on the linear scale) necessitate the introduction of additional components such as yttria-stabilized zirconia (YSZ). The polarization resistance of the model composite anode of reduced Fe₂NiO_{4 ± δ} and YSZ deposited on the YSZ solid electrolyte membrane was ~1.8 Ohm cm² at 923 K in a 4% H_2–Ar–H₂O atmosphere.     

Oxidation of Adamantane with H<Subscript>2</Subscript>O<Subscript>2</Subscript>–CF<Subscript>3</Subscript>COCF<Subscript>3</Subscript> · 1.5 H<Subscript>2</Subscript>O in the Presence of VO(acac)<Subscript>2</Subscript>

The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)₂ to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.     

Physicochemical properties of (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>NH<Subscript>2</Subscript>Cl–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Composite solid electrolytes were synthesized from the organic salt dimethylammonium chloride (1–x)C₂H₈NCl–xAl₂O₃. Their physicochemical properties were studied. In the starting C₂H₈NCl salt, there is a phase transition at 39°C accompanied by an increase in conductivity by two orders of magnitude. The conductivity of the high-temperature phase is 9.3 × 10^–6 S/cm at 160°C. A differential scanning calorimetry study showed that the salt in the composites spreads over the oxide surface and at x > 0.6 the salt melting enthalpy decreases to zero. The conductivity of the resulting composites was studied by impedance spectroscopy. It was shown that heterogeneous doping leads to a sharp increase in ion conductivity to 7.0 × 10^–3 S/cm at 160°C and a decrease in the activation energy to 0.55 eV.     

Thermal decomposition kinetics of PrMO<Subscript>3</Subscript> (M = Ni or Co) ceramic materials via thermogravimetry

Thermogravimetric data using the non-isothermal kinetic models of Flynn and Wall and “Model-free Kinetics” were used to determine the activation energy to study the decomposition kinetics of the ligand groups with system’s metallic ions that takes part in the synthesis of PrMO₃ (M = Ni or Co). This activation energy was determined for the stage of highest decomposition of the organic matter to establish parameters in synthesis condition optimization and application of the proposed material.