Showing papers on "Nickel published in 2012"

Hydrogen-evolution catalysts based on non-noble metal nickel-molybdenum nitride nanosheets.

Abstract: Hydrogen production through splitting of water has attracted great scientific interest because of its relevance to renewable energy storage and its potential for providing energy without the emission of carbon dioxide. Electrocatalytic systems for H2 generation typically incorporate noble metals such as Pt in the catalysts because of their low overpotential and fast kinetics for driving the hydrogen evolution reaction (HER). However, the high costs and limited world-wide supply of these noble metals make their application in viable commercial processes unattractive. Several non-noble metal materials, such as transition-metal chalcogenides, carbides, and complexes as well as metal alloys have been widely investigated recently, and characterized as catalysts and supports for application in the evolution of hydrogen. Nitrides of early transition-metals have been shown to have excellent catalytic activities in a variety of reactions. One of the primary interests in the applications of nitrides in these reactions was to use them in conjunction with low-cost alternative metals to replace group VIII noble metals. For example, the function of molybdenum nitride as a catalyst for hydrocarbon hydrogenolysis resembles that of platinum. The catalytic and electronic properties of transition-metal nitrides are governed by their bulk and surface structure and stoichiometry. While there is some information concerning the effect of the bulk composition on the catalytic properties of this material, there is currently little known about the effects of the surface nanostructure. Nickel and nickel–molybdenum are known electrocatalysts for hydrogen production in alkaline electrolytes, and in the bulk form they exhibited exchange current densities between 10 6 and 10 4 Acm , compared to 10 3 Acm 2 for Pt. Jaksic et al. postulated a hypo-hyper-d-electronic interactive effect between Ni and Mo that yields the synergism for the HER. Owing to their poor corrosion stability, few studies in acidic media have been reported.With the objective of exploiting the decrease in the overpotential by carrying out the HER in acidic media, we have developed a low-cost, stable, and active molybdenum-nitride-based electrocatalyst for the HER. Guided by the “volcano plot” in which the activity for the evolution of hydrogen as a function of the M H bond strength exhibits an ascending branch followed by a descending branch, peaking at Pt, we designed a material on the molecular scale combining nickel, which binds H weakly, with molybdenum, which binds H strongly. Here we report the first synthesis of NiMo nitride nanosheets on a carbon support (NiMoNx/C), and demonstrate the high HER electrocatalytic activity of the resulting NiMoNx/C catalyst with low overpotential and small Tafel slope. The NiMoNx/C catalyst was synthesized by reduction of a carbon-supported ammonium molybdate [(NH4)6Mo7O24·4H2O] and nickel nitrate (Ni(NO3)2·4H2O) mixture in a tubular oven in H2 at 400 8C, and subsequent reaction with NH3 at 700 8C. During this process, the (NH4)6Mo7O24 and Ni(NO3)2 precursors were reduced to NiMo metal particles by H2, and then they were mildly transformed to NiMoNx nanosheets by reaction with ammonia. The atomic ratio of Ni/Mo was 1/4.7 determined by energy dispersive X-ray spectroscopy (EDX) on the NiMoNx/ C sample. The transmission electron microscopy (TEM) images, as shown in Figure 1a, display NiMo particles that are mainly spherical. The high-resolution TEM image, as shown in the inset of Figure 1a, corroborated the presence of an amorphous 3 to 5 nm Ni/Mo oxide layer (see Figure S4 in the Supporting Information for resolved image), whereas NiMoNx is characterized by thin, flat, and flaky stacks composed of nanosheets with high radial-axial ratios (Figure 1b and Figure S5 in the Supporting Information for a magnified image). Figure 1c shows that some of the nanosheets lay flat on the graphite carbon (as indicated by the black arrows), and some have folded edges that show different layers of NiMoNx sheets (white arrows). The thickness of the sheets ranged from 4 to 15 nm. The average stacking number of sheets measured from Figure 1b is about [*] Dr. W.-F. Chen, Dr. K. Sasaki, Dr. J. T. Muckerman, Dr. R. R. Adzic Chemistry Department, Brookhaven National Laboratory Upton, NY 11973 (USA) E-mail: ksasaki@bnl.gov

Enhancing the Alkaline Hydrogen Evolution Reaction Activity through the Bifunctionality of Ni(OH)2/Metal Catalysts

Abstract: Active in alkaline environment: The activity of nickel, silver, and copper catalysts for the electrochemical transformation of water to molecular hydrogen in alkaline solutions was enhanced by modification of the metal surfaces by Ni(OH)(2) (see picture; I = current density and η = overpotential). The hydrogen evolution reaction rate on a Ni electrode modified by Ni(OH)(2) nanoclusters is about four times higher than on a bare Ni surface.

In Situ Raman Study of Nickel Oxide and Gold-Supported Nickel Oxide Catalysts for the Electrochemical Evolution of Oxygen

Abstract: An in situ Raman spectroscopic investigation has been carried out to identify the composition of the active phase present on the surface of nickel electrodes used for the electrochemical evolution of oxygen. The electrolyte in all cases was 0.1 M KOH. A freshly polished Ni electrode oxidized upon immersion in the electrolyte and at potentials approaching the evolution of oxygen developed a layer of γ-NiOOH. Electrochemical cycling of this film transformed it into β-NiOOH, which was observed to be three times more active than γ-NiOOH. The higher activity of β-NiOOH is attributed to an unidentified Ni oxide formed at a potential above 0.52 V (vs Hg/HgO reference). We have also observed that a submonolayer of Ni oxide deposited on Au exhibits a turnover frequency (TOF) for oxygen evolution that is an order of magnitude higher than that for a freshly prepared γ-NiOOH surface and more than 2-fold higher than that for a β-NiOOH surface. By contrast, a similar film deposited on Pd exhibits a TOF that is similar ...

Structure–Activity Correlations in a Nickel–Borate Oxygen Evolution Catalyst

Abstract: An oxygen evolution catalyst that forms as a thin film from Ni(aq)2+ solutions containing borate electrolyte (Ni–Bi) has been studied by in situ X-ray absorption spectroscopy. A dramatic increase in catalytic rate, induced by anodic activation of the electrodeposited films, is accompanied by structure and oxidation state changes. Coulometric measurements correlated with X-ray absorption near-edge structure spectra of the active catalyst show that the nickel centers in activated films possess an average oxidation state of +3.6, indicating that a substantial proportion of nickel centers exist in a formal oxidation state of Ni(IV). In contrast, nickel centers in nonactivated films exist predominantly as Ni(III). Extended X-ray absorption fine structure reveals that activated catalyst films comprise bis-oxo/hydroxo-bridged nickel centers organized into sheets of edge-sharing NiO6 octahedra. Diminished long-range ordering in catalyst films is due to their ostensibly amorphous nature. Nonactivated films display...

Recent progress in electrochemical hydrogen production with earth-abundant metal complexes as catalysts

Abstract: This perspective article reviews the recent important progress in electrocatalytic hydrogen production catalyzed by earth-abundant metal complexes. The catalysts are divided into two categories depending on the media used in the hydrogen-evolving reactions, with an emphasis on the types of acids employed. The catalysts used in the first category, which work in organic solutions, include nickel and cobalt complexes with base-containing diphosphine ligands, cobaloximes, cobalt tetrapyridine complexs, and [NiFe]- and [FeFe]-hydrogenase mimics. Molybdenum and cobalt pentapyridine complexes, as well as the cobalt bis(iminopyridine) complex reported very recently, are the most important examples of catalysts used in the second category, which work in aqueous solutions. The advantages and disadvantages of the different types of catalysts are discussed and the hydrogen-evolving mechanisms for the well-studied catalysts are illustrated. In addition, several molecular catalyst-modified electrodes for hydrogen production are described.

Graphene hydrogels deposited in nickel foams for high-rate electrochemical capacitors.

Abstract: Graphene hydrogel/nickel foam composite electrodes for high-rate electrochemical capacitors are produced by reduction of an aqueous dispersion of graphene oxide in a nickel foam (upper half of figure). The micropores of the hydrogel are exposed to the electrolyte so that ions can enter and form electrochemical double-layers. The nickel framework shortens the distances of charge transfer. Therefore, the electrochemical capacitor exhibits highrate performance (see plots).

Ni-based sol–gel catalysts as promising systems for crude bio-oil upgrading: Guaiacol hydrodeoxygenation study

Abstract: Catalytic hydrotreatment or hydrodeoxygenation (HDO) has been researched extensively with the crude bio-oil and its model compounds over conventional sulfided Ni(Mo), Co(Mo) catalysts and supported noble metal catalysts. These types of catalysts showed themselves unsuitable for the target HDO process, which resulted in an urgent need to search for a new catalytic system meeting such requirements as low cost, stability against coke formation and leaching of active components due to adverse effect of the acidic medium (bio-oil). In the present work a series of Ni-based catalysts with different stabilizing components has been tested in the hydrodeoxygenation (HDO) of guaiacol (2-methoxyphenol), bio-oil model compound. The process has been carried out in an autoclave at 320 °C and 17 MPa H2. The main products were cyclohexane, 1-methylcyclohexane-1,2-diol, and cyclohexanone. The reaction scheme of guaiacol conversion explaining the formation of main products has been suggested. The catalyst activity was found to rise with an increase in the active component loading and depend on the catalyst preparation method. The most active catalysts in HDO of guaiacol were Ni-based catalysts prepared by a sol–gel method and stabilized with SiO2 and ZrO2. According to TPR, XRD, XPS, and HRTEM, the high activity of these catalysts correlates with the high nickel loading and the high specific area of active component provided by the formation of nickel oxide–silicate species. The effect of temperature on the product distribution and catalyst activity in the target process (HDO) has been investigated as well. The catalysts were shown to be very promising systems for the production of hydrocarbon fuels by the catalytic upgrading of bio-oil.

Dodecyl sulfate-induced fast faradic process in nickel cobalt oxide–reduced graphite oxide composite material and its application for asymmetric supercapacitor device

Abstract: In this contribution, we report a facile preparation method of nickel cobalt oxide–reduced graphite oxide (NiCo2O4–rGO) composite material. A fast Faradic process has been realized by sodium dodecyl sulfate (SDS)-induced ultrasmall NiCo2O4 nanocrystals on rGO. As a result, this composite material gives a high specific capacitance of 1222 F g−1 at 0.5 A g−1 and 768 F g−1 at 40 A g−1, showing an outstanding rate capability. An asymmetric supercapacitor device with high energy and power densities has been successfully assembled based on NiCo2O4–rGO composite material and activated carbon. The optimized device shows a high energy density of 23.32 Wh kg−1 at a power density of 324.9 W kg−1. In addition, this asymmetric device shows good stability towards multistage current charge–discharge cycles.

Nickel-catalyzed C-H/C-O coupling of azoles with phenol derivatives.

Abstract: The first nickel-catalyzed C–H bond arylation of azoles with phenol derivatives is described. The new Ni(cod)2/dcype catalytic system is active for the coupling of various phenol derivatives such as esters, carbamates, carbonates, sulfamates, triflates, tosylates, and mesylates. With this C–H/C–O biaryl coupling, we synthesized a series of privileged 2-arylazoles, including biologically active alkaloids. Moreover, we demonstrated the utility of the present reaction for functionalizing estrone and quinine.

The role of the Auger parameter in XPS studies of nickel metal, halides and oxides

Abstract: The critical role of the Auger parameter in providing insight into both initial state and final state factors affecting measured XPS binding energies is illustrated by analysis of Ni 2p3/2 and L3M45M45 peaks as well as the Auger parameters of nickel alloys, halides, oxide, hydroxide and oxy-hydroxide. Analyses of the metal and alloys are consistent with other works, showing that final state relaxation shifts, ΔR, are determined predominantly by changes in the d electron population and are insensitive to inter-atomic charge transfer. The nickel halide Auger parameters are dominated by initial state effects, Δe, with increasing positive charge on the core nickel ion induced by increasing electronegativity of the ligands. This effect is much greater than the final state shifts; however, the degree of covalency is reflected in the Wagner plot where the more polarizable iodide and bromide have greater ΔR. The initial state shift for NiO is much smaller than those of Ni(OH)2 or NiOOH and the effective oxidation state is much less than that inferred from the average electronegativity of the ligand(s). Auger parameter analysis indicates that the bonding in NiO appears to have stronger contributions from initial state charge transfer from the oxygen ligands than that in the hydroxide and oxyhydroxide consistent with the considerable differences in the Ni–O bond lengths in these compounds with some relaxation of this state occurring during final state phenomena. The Auger parameter of NiOOH is, however, shifted positively, like the iodide, indicating greater polarizability of the ligands and covalency in this bonding. There is support for more direct use of relative bond lengths in interpreting differences between related compounds rather than more general electronegativity or similar parameters.

Reversible H2 addition across a nickel-borane unit as a promising strategy for catalysis.

Abstract: We report the synthesis and characterization of a series of nickel complexes of the chelating diphosphine-borane ligands ArB(o-Ph2PC6H4)2 ([ArDPBPh]; Ar = Ph, Mes). The [ArDPBPh] framework supports pseudo-tetrahedral nickel complexes featuring η2-B,C coordination from the ligand backbone. For the B-phenyl derivative, the THF adduct [PhDPBPh]Ni(THF) has been characterized by X-ray diffraction and features a very short interaction between nickel and the η2-B,C ligand. For the B-mesityl derivative, the reduced nickel complex [MesDPBPh]Ni is isolated as a pseudo-three-coordinate “naked” species that undergoes reversible, nearly thermoneutral oxidative addition of dihydrogen to give a borohydrido-hydride complex of nickel(II) which has been characterized in solution by multinuclear NMR. Furthermore, [MesDPBPh]Ni is an efficient catalyst for the hydrogenation of olefin substrates under mild conditions.

Raman and Infrared Spectroscopy of α and β Phases of Thin Nickel Hydroxide Films Electrochemically Formed on Nickel

Abstract: The present work utilizes Raman and infrared (IR) spectroscopy, supported by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to re-examine the fine structural details of Ni(OH)(2), which is a key material in many energy-related applications. This work also unifies the large body of literature on the topic. Samples were prepared by the galvanostatic basification of nickel salts and by aging the deposits in hot KOH solutions. A simplified model is presented consisting of two fundamental phases (α and β) of Ni(OH)(2) and a range of possible structural disorder arising from factors such as impurities, hydration, and crystal defects. For the first time, all of the lattice modes of β-Ni(OH)(2) have been identified and assigned using factor group analysis. Ni(OH)(2) films can be rapidly identified in pure and mixed samples using Raman or IR spectroscopy by measuring their strong O-H stretching modes, which act as fingerprints. Thus, this work establishes methods to measure the phase, or phases, and disorder at a Ni(OH)(2) sample surface and to correlate desired chemical properties to their structural origins.

Nickel-Catalyzed Carboxylation of Aryl and Vinyl Chlorides Employing Carbon Dioxide

Abstract: Nickel-catalyzed carboxylation of aryl and vinyl chlorides employing carbon dioxide has been developed. The reactions proceeded under a CO2 pressure of 1 atm at room temperature in the presence of nickel catalysts and Mn powder as a reducing agent. Various aryl chlorides could be converted to the corresponding carboxylic acid in good to high yields. Furthermore, vinyl chlorides were successfully carboxylated with CO2. Mechanistic study suggests that Ni(I) species is involved in the catalytic cycle.

Total Hydrogenation of Furfural over a Silica-Supported Nickel Catalyst Prepared by the Reduction of a Nickel Nitrate Precursor

Abstract: Gas-phase hydrogenation of furfural to tetrahydrofurfuryl alcohol is catalyzed by Ni/SiO2 with <4 nm Ni particle size, which is prepared by the reduction of supported nickel nitrate. The maximum yield is 94 %. The conversion of furfural to the furfuryl alcohol intermediate is less structure-sensitive. The subsequent step in which furfuryl alcohol is converted to tetrahydrofurfuryl alcohol is inhibited by the presence of furfural because furfural is more strongly adsorbed onto the catalyst surface than furfuryl alcohol. This step is strongly structure-sensitive and smaller turnover frequency (TOF) values are observed over Ni/SiO2 catalysts with a larger particle size.

Catalysis of nickel ferrite for photocatalytic water oxidation using [Ru(bpy)3]2+ and S2O8(2-).

Abstract: Single or mixed oxides of iron and nickel have been examined as catalysts in photocatalytic water oxidation using [Ru(bpy)(3)](2+) as a photosensitizer and S(2)O(8)(2-) as a sacrificial oxidant. The catalytic activity of nickel ferrite (NiFe(2)O(4)) is comparable to that of a catalyst containing Ir, Ru, or Co in terms of O(2) yield and O(2) evolution rate under ambient reaction conditions. NiFe(2)O(4) also possesses robustness and ferromagnetic properties, which are beneficial for easy recovery from the solution after reaction. Water oxidation catalysis achieved by a composite of earth-abundant elements will contribute to a new approach to the design of catalysts for artificial photosynthesis.

Nickel‐ and Cobalt‐Catalyzed Direct Alkylation of Azoles with N‐Tosylhydrazones Bearing Unactivated Alkyl Groups

Abstract: The functionalization of heteroaromatic compounds has received much attention from synthetic chemists because heteroaromatic cores are ubiquitously found in pharmaceuticals, biologically active compounds, and functional materials. The transition-metal-catalyzed cross-coupling reaction of heteroaryl halides or organometallic compounds is a powerful and reliable strategy to obtain functionalized heteroaromatic compounds. On the other hand, recent advances in the metal-mediated C H functionalization provide a complementary and potentially more efficient methodology to heteroaromatic compounds, because additional preactivation steps, such as the halogenation or stoichiometric metalation of the parent heterocycles, to prepare the coupling reagents can be avoided. Direct arylation, alkenylation, and alkynylation have been widely explored. However, the alkylation reaction is relatively challenging, 5] despite the fact that alkyl chains attached to aromatic nuclei are known to generally enhance lipophilicity and solubility, and to tune the aromatic p-stacking and p-conjugation of the corresponding oligomers and polymers. In particular, direct introduction of secondary alkyl side chains into heteroarenes remains elusive, probably because of the difficulty in controlling an undesired b-H elimination of an alkyl metal intermediate. A few successful examples with alkyl halides are still restricted in substrate scope to cyclic frameworks, such as cyclohexane and cyclopentane. A metal-catalyzed C H insertion approach with alkenes, and a copper-catalyzed alkylation with N-tosylhydrazones, which has very recently been reported by Wang and co-workers (see below), appear to be good alternatives, however, these processes are limited to activated systems, thus only enabling benzylation and allylation. Therefore, further developments for more general alkylation methodologies are strongly desired. Herein, we report nickeland cobalt-based catalysts for the direct alkylation of azoles with N-tosylhydrazones. The catalytic systems are compatible with various unactivated secondary alkyl groups, including cyclic and even more challenging acyclic alkyl groups. Our working hypothesis is inspired by our previous success in the nickel-catalyzed direct alkylation of azoles with primary alkyl halides and recent developments in the use of N-tosylhydrazones in cross-coupling reactions (Scheme 1). An initial base-assisted direct nickelation of a heteroarene provides a heteroaryl nickel species A. On the

Lithium Nickel Cobalt Manganese Oxide Synthesized Using Alkali Chloride Flux: Morphology and Performance As a Cathode Material for Lithium Ion Batteries

Abstract: Li(Ni(0.8)Co(0.1)Mn(0.1))O(2) (NCM811) was synthesized using alkali chlorides as a flux and the performance as a cathode material for lithium ion batteries was examined. Primary particles of the powder were segregated and grown separately in the presence of liquid state fluxes, which induced each particle to be composed of one primary particle with well-developed facet planes, not the shape of agglomerates as appears with commercial NCMs. The new NCM showed far less gas emission during high temperature storage at charged states, and higher volumetric capacity thanks to its high bulk density. The material is expected to provide optimal performances for pouch type lithium ion batteries, which require high volumetric capacity and are vulnerable to deformation caused by gas generation from the electrode materials.

Metal silicide, metal germanide, methods for making the same

Abstract: In one aspect, methods of silicidation and germanidation are provided. In some embodiments, methods for forming metal silicide can include forming a non-oxide interface, such as germanium or solid antimony, over exposed silicon regions of a substrate. Metal oxide is formed over the interface layer. Annealing and reducing causes metal from the metal oxide to react with the underlying silicon and form metal silicide. Additionally, metal germanide can be formed by reduction of metal oxide over germanium, whether or not any underlying silicon is also silicided. In other embodiments, nickel is deposited directly and an interface layer is not used. In another aspect, methods of depositing nickel thin films by vapor phase deposition processes are provided. In some embodiments, nickel thin films are deposited by ALD.

Removal of nickel (II) ions from aqueous solutions by biosorption on sugarcane bagasse

Abstract: The present study was undertaken to evaluate the feasibility of sugarcane bagasse for the removal of nickel from aqueous solution. Batch experiments were performed to study the biosorption of nickel on sugarcane bagasse sorbent considering the effect of contact time, initial concentration of nickel ions, pH of the solution and temperature. The sorption process was well explained with pseudo second-order kinetic model. The experimental maximum sorption capacity of sugarcane bagasse for nickel removal was approximately 2 mg/g at 25 °C and at pH 5. The biosorption data was fitted to Langmuir, Freundlich and Sips isotherm models. The Langmuir model showed better representation of data, with correlation coefficient greater than 0.99. The thermodynamics parameters were evaluated from the experimental data. The Gibbs free energy was determined to be negative, indicating the spontaneous nature of the sorption process. The results of the present study suggest that sugarcane bagasse waste can be used beneficially for nickel removal from aqueous solution.

Essential Roles and Hazardous Effects of Nickel in Plants

Abstract: Nickel is one of 23 metal pollutants of great concern to the environment and to human health (Sunderman 1992; Jarup 2003; Duda-Chodak and Baszczyk 2008). Nickel is the 24th most abundant element (twice as Cu) and comprises approximately 0.008% of the content of the earth’s crust; hence, it is a natural component of soil (parent material) and water (Alloway 1995; Hostýnek and Maibach 2002; Hedfi et al. 2007). Most of the earth’s nickel, however, is inaccessible, as it is locked in the iron–nickel molten core, which constitutes approximately 10% nickel. The second largest Ni deposits of the earth rest in the sea. It is estimated that the sea contains approximately eight billion tons of Ni, either dissolved in seawater or deposited in the seabed (Birch 1964; Stixrude et al. 1997). Soils may contain nickel levels as low as 0.2 mg kg−1 or as high as 450 mg kg−1. The average nickel content in soil is approximately 20 mg kg−1; however, the content level may vary greatly depending upon the mode of origin of the soil’s parent material (Assembly of Life Sciences 1975; Aubert and Pinta 1978; Wilson and Kordybach 2000). Because organic matter strongly absorbs some metals, particularly nickel, fossil fuels such as coal and oil may contain considerable amounts of nickel (Sigel et al. 2005). Moreover, Ni naturally occurs in a few plants (legumes) where it functions as an essential component of some enzymes (e.g., ureases) that are involved in nitrogen assimilation (Eskew et al. 1984; Brown et al. 1987a; Sakamoto and Bryant 2001).