Synthesis of nickel entities: From highly stable zerovalent nanoclusters to nanowires. Growth control and catalytic behavior (original) (raw)
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Catalysts, 2018
We have demonstrated a convenient method of synthesizing nickel nanowires (NiNWs), which could be easily tuned to produce materials with a carefully defined nanostructure. By varying the concentration of the Ni precursor, pH of the medium or reaction temperature, we directly affected the diameter of the formed product as well as the yield of the process. The obtained material consisted of straight bundles of NiNWs, which revealed powerful catalytic action for the reduction of nitroarenes to appropriate amine derivatives. A selection of substrates were employed and all of them were successfully converted into the corresponding aromatic amine despite the presence of different substituents on the aromatic ring with high yields, even in large scale reactions. The results showed that NiNW-based catalysts could constitute efficient catalytic systems for the synthesis of aryl amines at industrial levels.
The Synthesis and Use of Nano Nickel Catalysts
Journal of Nanoscience and Nanotechnology, 2019
The hydrazine reduction method was applied for the synthesis of nickel nanoparticles without using inert atmosphere and added surface active agents. The effect of the preparation temperature and the chemical quality of the metal sources as well as the solvents were studied. The generation of nanoparticles were studied primarily by X-ray diffractometry, but scanning and transmission electron microscopies as well as dynamic light scattering measurements were also used for the better understanding of the nanoparticles behaviour. The elevation of temperature was the key point in transforming Ni(OH) 2 into metallic nickel. By selecting the metal source, the obtained crystallite sizes could be tailored between 7 nm and 15 nm; however, the SEM and DLS measurements revealed significant agglomeration resulting in aggregates with spherical or Ni(OH) 2 resembling morphologies depending on the solvent used. The catalytic activities of the nanoparticles prepared were tested and compared in a Suzuki-Miyaura cross-coupling reaction.
Nanotechnologies in Russia, 2017
The peculiarities of the structure and catalytic behavior of nickel nanoparticles deposited onto an Al 2 O 3 surface by laser electrodispersion (LED) with subsequent activation in carbon monoxide atmosphere has been considered. The reduction of these nanoparticles by in situ treatment in a catalytic cell in Ar + 5% Н 2 atmosphere at 150-450°C has been studied using X-ray photoelectron spectroscopy (XPS). It is shown that formation of metal nickel starts by reduction in hydrogen at 300°C. A comparison of catalytic activity of the Ni/Al 2 O 3 systems in the catalytic oxidation of CO is carried out. It is found that the preliminary treatment of Ni/Al 2 O 3 sample by carbon monoxide leads to an increase in the catalyst efficiency and decrease in the reaction temperature by 50-100°C.
Preparation of nickel nanoparticles for catalytic applications
Inorganic Materials, 2010
Spherical oxidized nickel particles 15 to 200 nm in average size have been produced by a crucible less aerosol method involving metal vapor condensation in an inert gas flow and oxidation processes. The par ticles have been characterized by scanning electron microscopy, X ray microanalysis, X ray diffraction, BET surface area measurements, and vibrating sample magnetometry. The process parameters have been opti mized for the preparation of particles with tailored size, specific surface area, and saturation magnetization. A dc electric field applied to the condensation zone during the oxidation process reduces the size and increases the extent of oxidation of the particles. We have studied low temperature oxidation of carbon mon oxide and propane on nickel nanopowders differing in particle size and extent of oxidation. The nanoparticles with optimized characteristics have been shown to have a marked catalytic effect on these processes.
Scientific reports, 2016
Nitric oxide (NO) reduction pathways are systematically studied on a (111) facet of the octahedral nickel (Ni85) nanocluster in the presence/absence of hydrogen. Thermodynamic (reaction free energies) and kinetic (free energy barriers, and temperature dependent reaction rates) parameters are investigated to find out the most favoured reduction pathway for NO reduction. The catalytic activity of the Ni-nanocluster is investigated in greater detail toward the product selectivity (N2 vs. N2O vs. NH3). The previous theoretical (catalyzed by Pt, Pd, Rh and Ir) and experimental reports (catalyzed by Pt, Ag, Pd) show that direct N-O bond dissociation is very much unlikely due to the high-energy barrier but our study shows that the reaction is thermodynamically and kinetically favourable when catalysed by the octahedral Ni-nanocluster. The catalytic activity of the Ni-nanocluster toward NO reduction reaction is very much efficient and selective toward N2 formation even in the presence of hy...
From colloidal monodisperse nickel nanoparticles to well-defined Ni/Al2O3 model catalysts
Langmuir : the ACS journal of surfaces and colloids, 2017
In the past few decades, advances in colloidal nanoparticle synthesis have created new possibilities for the preparation of supported model catalysts. However, effective removal of surfactants is a prerequisite to evaluate the catalytic properties of these catalysts in any reaction of interest. Here we report on the colloidal preparation of surfactant-free Ni/Al2O3 model catalysts. Monodisperse Ni nanoparticles (NPs) with mean particle size ranging from 4-9 nm were synthesized via thermal decomposition of a zero-valent precursor in the presence of oleic acid. 5 wt % Ni/Al2O3 catalysts were produced by direct deposition of the pre-synthesized NPs on an alumina support, followed by thermal activation (oxidation-reduction cycle) for complete surfactant removal and surface cleaning. Structural and morphological characteristics of the nanoscale catalysts are described in detail following the propagation of the bulk and surface Ni species at the different treatment stages. Powder X-ray di...
NiO nanorings and their unexpected catalytic property for CO oxidation
Nanotechnology, 2006
Nickel oxide (NiO) nanorings were synthesized by controllable thermal decomposition of precursor Ni(OH) 2 nanoplates obtained via the reaction between Ni(NO 3 )·6H 2 O and NaOH under hydrothermal conditions. The process of their formation was investigated and an unexpected catalytic property of this novel-shaped material is reported for CO oxidation.
2013
One-dimensional transition metal nanostructures are of interest in many magnetic and catalytic applications. Using a combination of wet chemical synthesis, optical (infrared), and structural characterization methods (powder X-ray diffraction, scanning and transmission electron microscopy), we have investigated four paths to access 1D nickel nanostructures: (1) direct chemical reduction of a self-assembled nickel–hydrazine coordination complex, (2) thermal decomposition of the silica encapsulated nickel–hydrazine complex, (3) treatment of the silica encapsulated nickel–hydrazine complex with sodium borohydride followed by thermal annealing, and (4) electroless nickel plating using silica encapsulated nickel seed particles. We find that only route 1, which does not require a silica template, results in the formation of nickel nanorods, albeit some particle aggregation is observed. Routes 2 and 3 result in the formation of isotropic nickel structures under a reducing atmosphere. Route ...