Showing papers on "Nickel published in 2010"

Nickel-borate oxygen-evolving catalyst that functions under benign conditions.

Abstract: Thin catalyst films with electrocatalytic water oxidation properties similar to those of a recently reported Co-based catalyst can be electrodeposited from dilute Ni2+ solutions in borate electrolyte at pH 9.2 (Bi). The Ni-Bi films can be prepared with precise thickness control and operate at modest overpotential providing an alternative to the Co catalyst for applications in solar energy conversion.

Monodisperse nickel nanoparticles and their catalysis in hydrolytic dehydrogenation of ammonia borane.

Abstract: Monodisperse nickel nanoparticles are prepared from the reduction of Ni(acac)2 with borane tributylamine in the presence of oleylamine and oleic acid. Without any special treatment to remove the surfactants, the as-synthesized Ni nanoparticles supported on the Ketjen carbon support exhibit high catalytic activity in hydrogen generation from the hydrolysis of the ammonia−borane (H3NBH3) complex with a total turnover frequency value of 8.8 mol of H2·(mol of Ni)−1·min−1. Such catalysis based on Ni nanoparticles represents a promising step toward the practical development of the H3NBH3 complex as a feasible hydrogen storage medium for fuel cell applications.

An Efficient Nickel Catalyst for the Reduction of Carbon Dioxide with a Borane

Abstract: Nickel hydride with a diphosphinite-based ligand catalyzes the highly efficient reduction of CO2 with catecholborane, and the hydrolysis of the resulting methoxyboryl species produces CH3OH in good yield. The mechanism involves a nickel formate, formaldehyde, and a nickel methoxide as different reduced stages for CO2. The reaction may also be catalyzed by an air-stable nickel formate.

Development and Validation of ReaxFF Reactive Force Field for Hydrocarbon Chemistry Catalyzed by Nickel

Abstract: To enable the study of hydrocarbon reactions catalyzed by nickel surfaces and particles using reactive molecular dynamics on thousands of atoms as a function of temperature and pressure, we have developed the ReaxFF reactive force field to describe adsorption, decomposition, reformation and desorption of hydrocarbons as they interact with the nickel surface. The ReaxFF parameters were determined by fitting to the geometries and energy surfaces from quantum mechanics (QM) calculations for a large number of reaction pathways for hydrocarbon molecules chemisorbed onto nickel (111), (100) and (110) surfaces, supplemented with QM equations of state for nickel and nickel carbides. We demonstrate the validity and accuracy of ReaxFF by applying it to study the reaction dynamics of hydrocarbons as catalyzed by nickel particles and surfaces. For the dissociation of methyl on the (111), (100), and stepped (111) surfaces of nickel, we observe the formation of chemisorbed CH plus subsurface carbide. We observe that th...

Adsorption of copper, nickel and lead ions from synthetic semiconductor industrial wastewater by palm shell activated carbon

Abstract: Granular activated carbon produced from palm kernel shell was used as adsorbent to remove copper, nickel and lead ions from a synthesized industrial wastewater.Laboratory experimental investigation was carried out to identify the effect of pH and contact time on adsorption of lead, copper and nickel from the mixed metals solution. Equilibrium adsorption experiments at ambient room temperature were carried out and fitted to Langmuir and Freundlich models. Results showed that pH 5 was the most suitable, while the maximum adsorbent capacity was at a dosage of 1 g/L, recording a sorption capacity of 1.337 mg/g for lead, 1.581 mg/g for copper and 0.130 mg/g for nickel. The percentage metal removal approached equilibrium within 30 min for lead, 75 min for copper and nickel, with lead recording 100 %, copper 97 % and nickel 55 % removal, having a trend of Pb 2+ values of 0.977, 0.817 and 0.978 for copper, nickel and lead respectively, which fitted the equilibrium adsorption process more than Freundlich model for the three metals.

New catalytic route: Hydrogels as templates and reactors for in situ Ni nanoparticle synthesis and usage in the reduction of 2- and 4-nitrophenols

Abstract: Nickel nanoparticles inside poly(2-acrylamido-2-methyl-1-propansulfonic acid) (p(AMPS)) hydrogel were prepared by reduction of Ni(II) ions absorbed within hydrogel network. TEM images confirmed that in situ formed nickel particle in p(AMPS) hydrogel networks are about 100 nm. These nickel metal nanoparticles containing hydrogel-composites were utilized as catalysts and reaction media for the reduction reactions of aromatic nitro compounds, 2- and 4-nitrophenols with aqueous NaBH 4 . The reduction rate constants at four different temperatures (30, 40, 50 and 60 °C) and activation parameters were calculated. The activation energies ( E a ) for 4- and 2-nitrophenols are 25.70 and 38.69 kJ mol −1 , respectively. It was found that these types of hydrogel-composite catalyst systems can be used repetitively up to five times with 100% conversion and only with 25% reduction in the initial reduction rate.

New Co-based γ-γ′ high-temperature alloys

Abstract: New cobalt-based alloys containing ordered L12 precipitates have been investigated. With additions of Cr, Mo, Ni, Re, Ta, and V to the ternary Co-Al-W system, two phase γ-γ′ microstructures have been established. Solidus and liquidus temperatures are 100°C–150°C higher than advanced nickel-based single-crystal alloys strengthened with the L12 phase. An anomalous rise in flow stress with temperature is observed. Single crystals have been solidified and partitioning during solidification is limited in the ternary system, suggesting a high resistance to convective instabilities. Oxidation at 900°C results in the formation of cobalt oxide. Following oxidation, an inner layer of Al2O3 is observed in uncoated Cr-containing alloys and Cr2O3 is observed in alloys subjected to chromization.

Bimetallic nickel aluminum mediated para-selective alkenylation of pyridine: direct observation of eta2,eta1-pyridine Ni(0)-Al(III) intermediates prior to C-H bond activation

Abstract: We have presented new amino-NHC Ni-Al complex mediated para C-H bond activation for pyridine and quinolin, and isolated for the first time the intermediate structure of a bimetallic eta(2),eta(1)-pyridine nickel aluminum complex prior to its C-H activation, which serves as key evidence for bimetallic catalysis.

Transition metal adatom and dimer adsorbed on graphene: Induced magnetization and electronic structures

Abstract: Geometries, electronic structures, and magnetic properties of transition metal $M$ adatom and dimer adsorbed graphene have been studied ($M=\text{Fe}$, Co, Ni, and Cu). With adatom adsorption, we confirm the previously reported stable adsorption site, and the adatoms are chemically bonded with graphene except the copper adatom. With dimer adsorption, we observed that the stable configurations are dependent on the exchange-correlation functional for the iron dimer and nickel dimer; while the stable configurations do not depend on the functional for the cobalt and copper dimer. The adsorption energy indicates the copper dimer can barrierlessly diffuse along the graphene C-C bonds. With iron or cobalt adatom adsorption, graphene becomes a half-metal which can be used as a spin-filtering material. The iron dimer adsorbed graphene is also a half-metal, but the cobalt dimer adsorbed graphene is not. Both local-density approximation and generalized gradient approximation yield consistent results for the nickel adatom adsorbed graphene, which is the system is semiconducting and nonmagnetic due to the strong binding between nickel and graphene. However, different exchange-correlation functionals lead to controversial results for the magnetic and transport properties of nickel dimer adsorbed graphene. The copper adatom adsorbed on graphene exhibits $1{\ensuremath{\mu}}_{B}$ local magnetic moment, but the dimer does not show any magnetism. These results show that graphene properties can be effectively modulated by transition metal adsorption and that the transition metal adsorbed graphene can serve as potential materials in nanoelectronics, spintronics, or electrochemistry.

Controlled Synthesis of Hierarchical Nickel and Morphology-Dependent Electromagnetic Properties

Abstract: Nickel nanomaterials with a wide range of morphologies and sizes, such as superfine nanoparticles, urchinlike chains, smooth chains, rings, and hexagonal Ni/Ni(OH)2 heterogeneous structure plates, are synthesized in a single reaction system by simply adjusting the reaction conditions. The morphology transformation mechanism is systematically investigated. Magnetic measurement of urchinlike chains, smooth chains, and rings shows that the saturation magnetization (Ms) decreases with reduced sample size, and remanent magnetization (Mr) decreases with increasing reaction temperature. Additionally, coercivity (Hc) of urchinlike chains which is apparently larger than that of bulk nickel depends more on size than on shape anisotropy according to spherical chain reversal magnetization model. Enhanced microwave absorption of Ni/Ni(OH)2 hexagonal plates compared with smooth chains and rings is due to the synergistic effect of magnetic loss and dielectric loss. Particularly, the urchinlike nickel chains exhibit a be...

Bimetallic Au-Ni nanoparticles embedded in SiO2 nanospheres: synergetic catalysis in hydrolytic dehydrogenation of ammonia borane.

Abstract: Gold-nickel nanoparticles (NPs) of 3-4 nm diameter embedded in silica nanospheres of around 15 nm have been prepared by using [Au(en)(2)Cl(3)] and [Ni(NH(3))(6)Cl(2)] as precursors in a NP-5/cyclohexane reversed-micelle system, and by in situ reduction in an aqueous solution of NaBH(4)/NH(3)BH(3). Compared with monometallic Au@SiO(2) and Ni@SiO(2), the as-synthesized Au-Ni@SiO(2) catalyst shows higher catalytic activity and better durability in the hydrolysis of ammonia borane, generating a nearly stoichiometric amount of hydrogen. During the generation of H(2), the synergy effect between gold and nickel is apparent: The nickel species stabilizes the gold NPs and the existence of gold helps to improve the catalytic activity and durability of the nickel NPs.

Synergy effect in the HDO of phenol over Ni–W catalysts supported on active carbon: Effect of tungsten precursors

Abstract: The aim of this study was to detect any synergistic effect between nickel and tungsten oxide species supported on activated carbon as well as to study the effect of tungsten precursor (silicotungstic (HSiW), phosphotungstic (HPW), and tungstic (HW) acids) on the activity of partially reduced Ni–W/AC catalysts in phenol hydrodeoxygenation (HDO). The catalytic tests were performed in a flow fixed-bed reactor set-up at a hydrogen pressure of 1.5 MPa, temperatures ranging from 423 to 573 K and weight hourly space velocities of 0.5 g phenol /(g catalyst h). Before reaction, the catalysts were heat treated in H 2 flow at soft conditions ( T = 673 K for 4 h). The XPS analysis of spent catalysts revealed that this pre-treatment led to W(VI) species and a mixture of metallic and NiO species. Moreover, XPS and HRTEM analyses of the spent catalysts indicated that the nickel incorporation into W/AC catalysts led to a substantial improvement in surface exposure of the metal oxide species. All catalysts were active in the HDO of phenol and the most active catalysts were those prepared from heteropolyacids (HPAs). Regardless of the tungsten precursor, after Ni incorporation to the base W/AC system, a large enhancement in catalyst performance was observed. Moreover, supporting Ni and W phases on AC induced some beneficial effect because of the lower coke formation on the surface of AC with respect to classical alumina support. Regardless of the reaction temperature, analysis of the products suggests that reaction occurs via two direction pathways: (I) a hydrogenation (HYD) of phenol's aromatics ring (main reaction route) leading to formation of cylohexane, cyclohexene, cyclohexanol and methylcyclopentane and (II) a direct cleavage of the C–O σ bond leading to benzene formation. Total elimination of the O-containing compounds was archived in the HDO reaction at 573 K over oxide Ni–W(P)/AC and Ni–W(Si)/AC catalysts.

The Nickel/Copper-Catalyzed Direct Alkylation of Heterocyclic C—H Bonds

Abstract: A general and straightforward protocol for the cross-coupling of non-activated alkyl halides with heterocyclic CH bonds has been developed. The transformation is chemo- and regioselective and many functional groups on both coupling partners are tolerated. The method employs cheap nickel/copper catalysts, and expands significantly the scope of CH functionalization.

Tetraaza‐macrocyclic cobalt(II) and nickel(II) complexes as electron‐transfer agents in the photo(electro)chemical and electrochemical reduction of carbon dioxide

Abstract: The potential of a number of tetraaza‐macrocyclic complexes of cobalt and nickel to mediate the photoreduction of carbon dioxide has been studied. Carbon monoxide and hydrogen are the main products, which result from illumination of an aqueous solution containing Ru(2, 2′‐bipyridine)2+ 3 as sensitizer, ascorbic acid as sacrificial eletron donor and a tetraaza‐macrocyclic complex as relay. Their ratio strongly depends upon the relay compound used. The complexes can be used as electrocatalysts for CO2 reduction at a mercury electrode since they lower the overpotential for CO2 reduction showing turnover numbers/hour of approximately 3. A minimum potential is required to induce reaction of electrocatalysts and CO2 (and H2O). Finally, the redox properties of the macrocyclic metal complexes at p‐GaP and p‐GaAs photocathodes in acetonitrile are compared with those observed at Pt.

A semi-empirical energy-level diagram for octahedral cobalt(II) complexes

Abstract: Methods of calculation for the parameters Dq and B from the ligand-field spectra of octahedral cobalt(II) compounds are discussed. A method of calculation is introduced, which considers the lowering of the 4T1g (F) state by spin-orbit splitting. This calculation is applied to the spectra of 43 octahedrally coordinated cobalt(II) compounds. With the aid of the spectral data an energy-level diagram is constructed, into which the absorption bands are fitted. Comparison of calculated Dq and B values with corresponding values for isomorphous nickel(II) compounds shows that - in general - the crystalfield parameter Dq is highest for cobalt, although the differences with nickel are less than 4 % in most cases. The calculated B values corresponds with those of Ni, with differences less than 1 % for many ligands.

The non-enzymatic determination of glucose using an electrolytically fabricated nickel microparticle modified boron-doped diamond electrode or nickel foil electrode

Abstract: A nickel modified boron-doped diamond (Ni-BDD) electrode or nickel foil electrode were used in the non-enzymatic determination of glucose in alkaline solutions. The Ni-BDD electrode was electrodeposited from a 1 mM Ni(NO3)2 solution (pH 5), followed by repeat cycling in KOH. Subsequent analysis utilised the Ni(OH)2/NiOOH redox couple to electrocatalyse the oxidation of glucose. Glucose was determined to limits of 2.7 μM with a sensitivity of 1.04 μA μM−1 cm−2 at the Ni-BDD electrode. The foil electrode was comparably sensitive achieving a limit of 1.8 μM but a relatively lower sensitivity of 0.67 μA μM−1 cm−2. SEM analysis of the electrodes found the Ni-BDD to be modified by a quasi-random microparticle assembly, with approximately 7.6 μg cm−2 of nickel present on the surface.

Synthesis of Graphene on Silicon Dioxide by a Solid Carbon Source

Abstract: We report on a method for the fabrication of graphene on a silicon dioxide substrate by solid-state dissolution of an overlying stack of a silicon carbide and a nickel thin film. The carbon dissolves in the nickel by rapid thermal annealing. Upon cooling, the carbon segregates to the nickel surface forming a graphene layer over the entire nickel surface. By wet etching of the nickel layer, the graphene layer was allowed to settle on the original substrate. Scanning tunneling microscopy (STM) as well as Raman spectroscopy has been performed for characterization of the layers. Further insight into the morphology of the layers has been gained by Raman mapping indicating micrometer-size graphene grains. Devices for electrical measurement have been manufactured exhibiting a modulation of the transfer current by backgate electric fields. The presented approach allows for mass fabrication of polycrystalline graphene without transfer steps while using only CMOS compatible process steps.

Nickel(ii) tetra-aminophthalocyanine modified MWCNTs as potential nanocomposite materials for the development of supercapacitors

Abstract: The supercapacitive properties of nickel(II) tetraaminophthalocyanine (NiTAPc)/multi-walled carbon nanotube (MWCNT) nanocomposite films have been interrogated for the first time and found to possess a maximum specific capacitance of 981 ± 57 F g−1 (200 ± 12 mF cm−2), a maximum power density of 700 ± 1 Wkg−1, a maximum specific energy of 134 ± 8 Wh kg−1 and excellent stability of over 1500 charge-discharge continuous cycling. Impedimetric study proves that most of the stored energy of the MWCNT-NiTAPc nanocomposite can be accessible at high frequency (720 Hz). When compared to MWCNTs modified with unsubstituted nickel(II) phthalocyanine (MWCNT-NiPc) or nickel(II) tetra-tert-butylphthalocyanine (MWCNT-tBuNiPc), MWCNT-NiTAPc exhibited superior supercapacitive behaviour, possibly due to the influence of nitrogen-containing groups on the phthalocyanine rings.