Formation Of Nickel Research Articles

Biomass-Derived Nickel Phosphide Nanoparticles as a Robust Catalyst for Hydrogen Production by Catalytic Decomposition of C2H2 or Dry Reforming of CH4

Nickel is well recognized for its high catalytic activity in hydrogen production and hydrotreating, but it experiences severe deactivation upon coke formation. The development of a nickel-based catalyst that is resilient to deactivation while maintaining its signature high activity is therefore desirable. We demonstrate a simple but effective technique for the synthesis of nickel phosphide catalysts by impregnating nickel into carbonized natural cellulose fibers (NCFs) that naturally contain phosphorus. At a sufficient annealing temperature (1100 °C), the nickel particles react with phosphorus, forming Ni2P and Ni5P4 nanoparticles. Higher annealing temperatures (>1500 °C) promote the formation of single atom nickel, which greatly supplements the catalytic performance. Our nickel phosphide catalyst exhibits a markedly superior activity and stability in the synthesis of hydrogen by C2H2 decomposition and the dry reforming of methane (DRM) compared to the Ni/Al2O3 model catalyst. The sustained activity and s...

Formation and decomposition of Nickel(II) complexes with tridentate aminoether or aminoalcohol ligands

Tridentate aminoalcohol and aminoether ligands, iminodiethanol [H2(ide)] and bis(2-methoxyethyl)amine [bmoen], form mononuclear nickel(II) complexes, [Ni{H2(ide)}2][BPh4]2·3.5H2O (1), [Ni{H2(ide)}2][BPh4]2·BPh(ide)·(CH3)2CHOH (2), [Ni{H(ide)}{H2(ide)}][BPh4]·3CH3OH (3), and [Ni(bmoen)2][BPh4]2·H2O (4). In the decomposition procedure of 4 in dimethylformamide (dmf), mononuclear nickel(II) complexes, [Ni(bmoen)2(dmf)][BPh4]2·dmf (5), [Ni(bmoen)(dmf)3][BPh4]2·0.5H2O (6), and [Ni(dmf)6][BPh4]2 (7) were obtained. Since the crystal structures were unknown for 1, 4, and 6, each complex-cation structure was predicted on the basis of the term-splitting in the electronic spectra. The [Ni{H2(ide)}2]2+ complex cation in 1 and the [Ni(bmoen)2]2+ complex cation in 4 were predicted to be cis-fac structures, and the [Ni(bmoen)(dmf)3]2+ complex cation in 6 was predicted to be a fac structure. The predicted structures were consistent with the result of conformational analysis on the basis of the DFT calculation.

Formation of Oligo-Nuclear Carboxylate Nickel(II) Complexes with Nitrogen-Containing Ligands. Quantum-Chemical Simulation

Using the DFT method PBE0/6-31G(d, p) and taking into account the solvent, the formation of bi- and pentahedral Ni(II) complexes with carboxylate and N-containing ligands in the gas phase was studied, and ΔG° of their formation from simple compounds was estimated. The functional role of bridging groups and hydrogen bonds in the formation of polynuclear structures was revealed. A model of self-organization of penta-nuclear coordination compounds [NiII5(O2CR)8L2n(μ-OH)2]0 from binuclear complex [NiII2(O2CR)4Ln(μ-H2O)]0 was proposed, into the structure of which mononuclear NiII cations are embedding and promote proton transfer from bridging aqua ligands.

Thermodynamic and Spectroscopic (UV–Vis, FT IR) Studies of Solutions of CoCl2 (or NiCl2) in Diethylsulfoxide

Densitometry, UV–Vis and FT IR spectroscopy were used to study the complex formation of cobalt(II) chloride and nickel(II) chloride with diethylsulfoxide (DESO). The apparent molar volumes and partial molar volumes were determined for solvated ions in DESO. The complex formation of nickel(II) and cobalt(II) ions with DESO molecules via oxygen atom of SO group was revealed from the SO stretching band in the FT IR spectra. UV–Vis spectra show the coexistence of two types of complexes with DESO in solution. The results show that solvating ability of DESO is stronger than that of dimethylsulfoxide.

Effect of nickel nanopowder on lubrication behaviour of low-temperature grease in steel-steel tribosystem

ABSTRACTNickel nanoparticles with sizes from 12 to 34 nm were obtained by pyrolysis of nickel formate. They have been used as additives to the low-temperature grease (CIATIM-201). Studies of tribotechnical properties have shown that the CIATIM-201 with nickel additives at concentrations of 0.05 wt. % - 0.2 wt. % has the best antiwear and extreme pressure properties in comparison with pure grease. Friction surfaces were characterised by the methods of atomic-force microscopy AFM (PHYWE), 3D optical microscopy and indentation tests. The improvement of tribotechnical properties of grease is related to the process of micro-polishing, which leads to the formation of a structural layer with a high modulus of elasticity on the friction surface.

Catalytic Conversion of Atmospheric CO2 into Organic Carbonates by Nickel(II) Complexes of Diazepane-Based N4 Ligands.

Activation of CO2 and conversion into value-added products is an effective option to mitigate CO2 emission. The nickel(II) complexes [Ni(L1)](ClO4)2 1, [Ni(L2)](ClO4)2 2, and [Ni(L3)(CH3CN)2](Ph4B)2 3 of diazepane-based ligands [1,4-bis[(pyridin-2-yl-methyl)]-1,4-diazepane (L1), 1,4-bis[2-(pyridin-2-yl)ethyl]-1,4-diazepane (L2), and 4-bis[2-(quinoline-2-yl)-methyl]-1,4-diazepane (L3)] have been synthesized and structurally characterized. The complexes were employed as the catalysts for the conversion of atmospheric CO2 into organic carbonates in the absence of cocatalyst at 1 atm pressure. The single-crystal X-ray structures of 1 and 2 exhibit distorted square-planar geometry with almost identical Ni-N bond distances (1.891-1.946 Å). The geometry of the complexes rearranged into octahedral in acetonitrile, which was studied by paramagnetic 1H NMR and electronic spectra. The complexes selectively captured CO2 from the atmospheric air and readily converted epoxides into cyclic carbonates without any cocatalyst. They showed a maximum yield of 25% (TON, 500) using 1 atm air, which is drastically enhanced up to 89% (TON, 1780) using 1 atm pure CO2 gas. This is the highest catalytic efficiency reported for CO2 fixation using nickel-based catalysts to date. The CO2 fixation reaction without organic substrate showed the formation of carbonate-bridged dinuclear nickel(II) complexes. They showed characteristic absorption bands around 571-612 nm and were further confirmed by electrospray ionization mass spectrometry, IR, and single-crystal X-ray structures. The molecular structure of carbonate-bridged intermediates exhibited two Ni2+-centers with distorted square pyramidal geometries for 2a and 3a but distorted octahedral and square pyramidal geometries for 1a. The CO2 fixation reactions possibly proceeded via the formation of CO2-bound nickel species.

Redox states of nickel in zeolites and molecular account into binding of N2 to nickel(I) centers – IR, EPR and DFT study

Redox chemistry of nickel centers in high-silica ZSM-5 and BEA zeolites was investigated by a combined use of temperature-programmed reduction (TPR), electron paramagnetic resonance (EPR), and infrared (FTIR) spectroscopic techniques supported by quantum chemistry methods. The isolated nickel and nickel-oxo centers were identified and quantified by means of EPR using CO and NO probes and by IR using CO as a probe molecule. The nickel-oxo species gave rise to the nickel(I) centers upon reduction in CO. Their interaction with N 2 under low temperature led to the formation of nickel(I)–dinitrogen adducts. Attribution of the IR bands and identification of the structures of dinitrogen adducts were based on the coadsorption experiments of 14 N 2 and 15 N 2 isotopes and complementary density functional theory (DFT) calculations. Because of the presence of a mixed ligand ( 14 N 2 15 N 2 ) adduct, a structural dichotomy of possible formation of the geminal Ni(I)–(N 2 ) 2 and two coupled vicinal mono-adducts N 2 –Ni(I)⋅⋅⋅Ni(I)–N 2 was resolved. The isolated Ni(I)–N 2 and geminal Ni(I)–(N 2 ) 2 adducts were identified with confidence. A mechanism of N 2 bonding was accounted for by natural orbitals for chemical valence (NOCV) population analysis. Charge flow molecular channels due to the σ donation and π back-donation effects were established in a quantitative way. This allowed for unraveling the molecular background of the observed bathochromic shift of the stretching vibrations of all dinitrogen adducts. • Ni(II)-oxo and isolated Ni(I/II) centers undergo complex redox changes in zeolites. • Nickel speciation is controlled with protic/aprotic solution during ion exchange. • Nickel(I) forms isolated Ni(I)–N 2 and geminal Ni(I)–(N 2 ) 2 adducts. • Binding mechanism of N 2 by Ni(I) unraveled with charge flow σ and π channels.

Synthesis, structural characterization, DFT calculations and biological properties of mono- and dinuclear nickel complexes with tetradentate transformed ligands by aerobic oxidative-coupling reactions

Reaction of nickel chloride with acetylacetone bis(salicylhydrazone) (L) (prepared in situ by condensation of acetylacetone with salicylhydrazide) in methanol results in the formation of air-sensitive nickel (II) complex of symmetrical tetradentate Schiff base [NiII(L)] (1). Air oxidation of 1 leads to the formation of dinuclear species [NiII(L-L)NiII] (2) where the ligand (L-L)4– is formed by oxidative C-C coupling at the central methylene group of the acetylacetone fragment of (L)2–. The same reaction in methanol/pyridine solution leads to oxidative C-N coupling forming a mesoionic [NiII(L-Py)](3). The use of Nickel acetylacetonate in methanol/pyridine or DMSO solution under aerobic conditions provide [NiII(L-O)(py)2](4), [NiII(L-O)(DMSO)2](5). In this case, the ligand (L)2– is partially oxidized to form (L-O) which is formed by oxidation of the central methylene group. The molecular structure of 1–5 have been determined by X-ray crystallography. The first three complexes 1, 2 and 3 have a square-planar geometry, while, 4 and 5 adopt octahedral geometry. In vitro antioxidant activities of compounds 1, 4 and 5 were evaluated against DPPH radical and hydrogen peroxide and were compared with standard antioxidant, ascorbic acid. Our results reveal that the three compounds exhibit excellent radical scavenging activities. DFT calculations have been performed on complexes 1–5 using the BP86 and B3LYP functionals to provide a complete rationalization of their structures and to describe their electronic structures elucidating the fundamental spin state and the Metal-Ligand interaction type.

Nickel(II)-Catalyzed [5 + 1] Annulation of 2-Carbonyl-1-propargylindoles with Hydroxylamine To Synthesize Pyrazino[1,2-a]indole-2-oxides in Water.

An atom-economical and practical method for the efficient synthesis of various pyrazino[1,2-a]indole-2-oxides was developed through a nickel(II)-catalyzed [5 + 1] annulation of 2-carbonyl-1-propargylindoles with hydroxylamine in water without using an organic solvent. The reaction involved an initial condensation of 2-carbonyl-1-propargylindoles with hydroxylamine to afford oxime intermediates, which then underwent a nickel(II)-catalyzed 6-exo-dig cyclization. Preliminary studies showed that (n-Bu)4NI served as a phase transfer catalyst and promoted the formation of active nickel(II) species. More importantly, the nickel(II) salt and phase transfer catalyst-in-water could be recycled seven times, and a gram scalable product was easily obtained in good yields through a filtration and washing protocol.

Local electrochemistry of nickel (oxy)hydroxide material gradients prepared using bipolar electrodeposition

Nickel (oxy)hydroxide materials gradients were prepared using bipolar electrochemistry. A correlated microscopy approach, using scanning electron microscopy and scanning electrochemical cell microscopy, was used to study the local morphology and electrocatalytic activity of the nickel (oxy)hydroxide materials gradient. It was found that bipolar electrodeposition led to the formation of discrete nickel (oxy)hydroxide particles, while energy dispersive X-ray spectroscopy and local electrochemical surface area measurements showed that the amount of nickel on the surface increased with increasing deposition overpotential. An apparent turnover frequency was calculated for the oxygen evolution reaction as a function of electrode position enabling local electrocatalytic activity to be quantified. This new approach, combining bipolar electrochemistry with local electrochemical measurements, enables the screening of electrocatalytic materials gradients generated across the surface of heterogeneous bipolar electrode substrates.

DIMETILGLIOXIMA: un reactivo químico con 100 años de historia

La dimetilglioxima (diacetildioxima o butano-2,3-dioxima), dmgH2, es uno de los quelatos de uso más extendido en química de coordinación y analítica. La reacción de formación del bis(dimetilglioximato) de níquel(II), reportada por Lev A. Chugaev (Tschugaeff) en 1905, constituye una de las primeras pruebas específicas para la identificación cualitativa de un metal de transición. Desde entonces, y por más de un siglo, la dimetilglioxima adquirió importancia como un notable agente quelante, y sus compuestos complejos se han venido utilizando en áreas como la química inorgánica, catálisis, electroquímica, ciencia de materiales, entre otras. En este artículo, presentamos una breve revisión de la dimetilglioxima, los dimetilglioximatos metálicos y algunas de sus aplicaciones más representativas. La revisión indica que, además de su gran éxito como reactivo analítico para la determinación de metales, existen importantes estudios de los dimetilglioximatos metálicos como catalizadores de diversas reacciones, destacando la producción de hidrógeno molecular, una reacción de importancia por su impacto en la economía del hidrógeno y la química verde.

Application of nickel nanopowders of different morphology for the synthesis of highly porous materials by powder metallurgy

In this work, we studied the morphology of nickel nanopowders synthesized in various ways: by chemical-metallurgical method, by decomposition of nickel formate and by electroexplosive technology. A comparative analysis of the characteristics of these nanopowders has been carried out. A sample carrier was made from the powder synthesized by electroexplosive technology. A porous material with a gradient structure was created by modifying the pore surface of a sample carrier with catalytically active centers of copper oxide.

Formation and wear mechanism of nickel titanium intermetallics during heat treatment of nickel coating on Ti-6Al-4V substrate

ABSTRACTIn the present work, inter-diffusion of nickel and titanium and formation of Ni-Ti intermetallic compounds on Ti-6Al-4V substrate have been studied. Initially, nickel was electrodeposited on the alloy using a modified Watts bath solution at a current density of 2 A dm−2 for 1 h. The coated specimens were then heat treated for different durations at 750, 800 and 850 °C under argon atmosphere. The effects of temperature and time on the characteristics, hardness and wear resistance of intermetallic phases were investigated. The results showed that a multilayer structure was formed after heat treatment, an outer layer of residual nickel, an area of intermetallic layers with different compositions followed by a solid solution of Ni-Ti. It was also observed that an increase in time or temperature at first led to the formation of thicker intermetallic layers; however, after passing a critical point, the intermetallic layers seem to dissolve into the substrate. Furthermore, the wear rates of the diffusion treated samples were four times lower compared to Ti-6Al-4V alloy when sliding against AISI 52100 hardened steel.

Metallurgical Beneficiation of Iron Laterite Ores with the Formation of a Metallic Nickel–Cobalt Concentrate

A new process is developed for metallurgical beneficiation of iron laterite nickel-containing (limonite) ores with the formation of a metallic nickel–cobalt concentrate. This process includes reducing roasting of the ores with sulfur-containing additions in the temperature range 1100–1200°C, the fragmentation of the roasting product, and the magnetic separation of metallic and slag phases. The coarsening of metallic particles in roasting is shown to occur with the participation of a low-melting-point phase (iron oxysulfide Fe(O,S)). In this case, nickel and cobalt concentrate in a metallic phase in the form of an alloy with iron (ferronickel). At the optimum charge composition and reducing roasting parameters, ferronickel particles coalesce and grow to 40–100 μm, which creates favorable conditions for the subsequent beneficiation of the roasting product (cinder) by magnetic separation. After wet magnetic separation of a fragmented cinder, the extraction of nickel and cobalt into a magnetic fraction is 92 and 84%, respectively. When a poor limonite ore (1.03% Ni, 0.05% Co) is processed according to the developed technology, the synthesized metallic concentrate contains up to 8.3% Ni and 0.37% Co.

Using Nickel Nanopowders with Different Morphologies for Fabrication of Highly Porous Nickel Materials

We study the effects that the morphology of nickel nanopowders obtained by chemical metallurgy, nickel formate thermal decomposition, and wire electrical explosion has on the properties of porous samples fabricated from these nanopowders using the powder metallurgy method. Porous nickel samples are prepared from a mixture of nickel powder (30 vol %) and ammonium bicarbonate (70 vol %) by sintering in a flow of hydrogen at 700°C and under a pressure of 300 MPa. Samples fabricated from the nickel nanopowder obtained by the wire electrical explosion method have the highest total and open (65.8%) porosities. Samples fabricated from the other two types of nickel nanopowders have lower porosity.

Synthesis of Ni nanoparticles with controlled pyrophoricity and mean size

This study establishes that nickel formate decomposition in an argon flow at 209°C and subsequent processing of the obtained nanopowder in a hydrogen flow within a specified time interval, make it possible to control the pyrophoricity and average size of Ni particles.

Preparation of high-purity straight silicon nanowires by molten salt electrolysis

Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process. Using nickel formate as a metal catalyst precursor, straight silicon nanowires (65–150 nm in diameter) were directly prepared by electrolysis from the Ni/SiO2 porous pellets with 0.8 wt% nickel content in molten CaCl2 at 900 °C. Benefiting from their straight appearance and high purity, the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 mAh/g. In addition, the silicon nanowire/carbon composite exhibited excellent cycle performance, retaining 90.38% of the initial capacity after 100 cycles. Whilst further study on the charge storage performance is still ongoing, these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis, which is suitable for large-scale production.

Tribological and tribocorrosion behavior of nickel sliding against oxide ceramics

Nickel is widely used as a coating material in electroplating because of its good corrosion and wear resistance even at high temperature. Tribocorrosion has been identified as one of the main degradation mechanisms of nickel. This study evaluated the tribocorrosion behavior of pure nickel in citrate buffer solution (pH 4.5) under controlled mechanical, chemical and electrochemical conditions as well as wear of pure nickel in dry condition sliding against alumina or zirconia balls, respectively. The results showed that the wear of nickel was higher in passive domain due to wear accelerated corrosion compared to that in the cathodic domain. Surprisingly, both alumina and zirconia were worn by nickel in tribocorrosion condition under passive potentials as well as in dry condition. However, in the cathodic domain, negligible wear was observed on the alumina and zirconia balls. The formation of mixed nickel and aluminum/zirconium oxides was proposed as the wear mechanism of alumina and zirconia.

In-situ growth of iron/nickel phosphides hybrid on nickel foam as bifunctional electrocatalyst for overall water splitting

The use of nonprecious metal-based materials as bifunctional electrocatalysts for overall water splitting is of great significance to design and utilize cost-efficient commercial clean energy devices. Herein we report a facile method for the in-situ growth of iron/nickel phosphides hybrid on nickel foam via direct phosphorization of nickel foam after treated by iron nitrate aqueous solution. The optimal sample exhibits superior hydrogen and oxygen evolution reaction activities with low overpotentials of 63 and 185 mV at 10 mA cm−2 and small Tafel slopes of 59 and 47 mV dec−1 in 1 M KOH, respectively. The corresponding two-electrode cell demands 1.567 V to achieve 10 mA cm−2 without iR compensation. It can deliver a large current density of around 113 mA cm−2 without decay during the electrolysis at 2 V for 24 h. The morphological, structural and component evolution of the as-prepared iron/nickel phosphides hybrid are systematically investigated. The synergistic effect between Ni2P and FeP and the formation of three-dimensional iron and nickel (oxy)hydroxides as real catalytic active sites play an important role in significantly improving the electrocatalytic activity. This work provides a further insight into the nickel foam-based bifunctional electrocatalysts for overall water splitting.

Reductive Binding and Ligand-Based Redox Transformations of Nitrosobenzene at a Dinickel(II) Core.

The metal-mediated activation of PhNO represents an important starting point for understanding the reactivity patterns of nitrosoarenes in biological systems and catalysis. Here we report that the pyrazole-based dinickel(II) dihydride complex [KL(NiH)2] (1) reacts with PhNO to eliminate dihydrogen concomitant with binding of the doubly reduced substrate in μ-κ(O):κ(N) mode in the bimetallic pocket of [KLNi2(PhNO)] (2). The addition of [2,2,2]cryptand leads to the ionic complex [K(crypt)][LNi2(PhNO)] (3). Structural and spectroscopic analyses evidence that interaction with the Lewis acidic K+ in 2 causes significant elongation and weakening of the substrate's N-O bond [ dN-O = 1.487(12) Å in 2 vs 1.374(4) Å in 3]. Complex 2 (or 3) reacts with [FeCp*2][PF6] to give LNi2(PhNO) (4), which is shown by electron paramagnetic resonance and IR spectroscopies and density functional theory calculations to feature two low-spin d8 nickel(II) ions and a bridging (PhNO)•- radical anion ligand, with the out-of-plane π*(NO) being the singly occupied molecular orbital. Cyclic voltammetry and UV-vis spectroelectrochemical experiments show that 4 and the anion of 3 can be reversibly interconverted at very low potential ( E1/2 = -1.53 V vs Fc/Fc+). Protonation of 2 leads to the N-phenylhydroxylamine complex [LNi2(ONHPh)] (5) with a long N-O bond of 1.464(2) Å, and titration studies suggest a p Ka of around 23-25 in tetrahydrofuran. This allows one to derive a bond dissociation energy of 62-65 kcal mol-1 for the N-H bond of 5. Accordingly, 5 readily reacts with the phenoxy radical 2,4,6- tBu3C6H2O• to yield 4. This work demonstrates the reductive binding of PhNO without prior formation of unstable nickel(I) species and the redox noninnocence of the PhNO ligand in the less common μ-κ(O):κ(N) bridging mode. Thermodynamic data for H-atom-abstraction chemistry at the activated PhNO may be valuable for understanding the reactivity patterns of the transient but biologically relevant nitroxyl (HNO) ligand.