Nickel Nanoparticle Catalyst Research Articles

Subeutectic growth of single-crystal silicon nanowires grown on and wrapped with graphene nanosheets: high-performance anode material for lithium-ion battery.

A novel one-pot synthesis for the subeutectic growth of (111) oriented Si nanowires on an in situ formed nickel nanoparticle catalyst prepared from an inexpensive nickel nitrate precursor is developed. Additionally, anchoring the nickel nanoparticles to a simultaneously reduced graphene oxide support created synergy between the individual components of the c-SiNW-G composite, which greatly improved the reversible charge capacity and it is retention at high current density when applied as an anode for a Li-ion battery. The c-SiNW-G electrodes for Li-ion battery achieved excellent high-rate performance, producing a stable reversible capacity of 550 mAh g(-1) after 100 cycles at 6.8 A g(-1) (78% of that at 0.1 A g(-1)). Thus, with further development this process creates an important building block for a new wave of low-cost silicon nanowire materials and a promising avenue for high rate Li-ion batteries.

Kinetics of the In-Situ Upgrading of Heavy Oil by Nickel Nanoparticle Catalysts and Its Effect on Cyclic-Steam-Stimulation Recovery Factor

Summary The effect of nickel nanoparticles on in-situ upgrading of heavy oil (HO) during aquathermolysis and the effect of this process on the recovery through cyclic steam injection were studied. High-temperature experiments were conducted with a benchtop reactor to study the kinetics of the reactions among oil, water, and sandstones in the presence and absence of the nickel nanoparticles. Eighteen experiments were conducted at three different temperatures and at three different lengths of time, and the evolved hydrogen sulfide during the reaction was analyzed. The kinetic analysis showed that nickel nanoparticles reduce the activation energy of the reactions corresponding to the generation of hydrogen sulfide by approximately 50%. This reaction was the breakage of C-S bonds in the organosulfur compounds of the HO. The maximal catalysis effect was observed to be at a temperature of approximately 270°C. Also, the simulated-distillation gas-chromatography (GC) analysis of the oil sample, after the aquathermolysis reactions, confirmed the catalysis effect of nickel nanoparticles. According to this analysis, by catalytic process, the concentration of the components lighter than C30 increased whereas the concentration of heavier components decreased. Next, the effect of the catalytic aquathermolysis on the recovery factor of the steam-stimulation technique was studied. The stimulation experiments consisted of three injection/soaking/production phases. The results showed that the nickel nanoparticles increased the recovery factor by approximately 22% when the nanoparticles were injected with a cationic surfactant and xanthan-gum polymer. This increase of recovery was approximately 7% more than that of the experiment conducted with the surfactant and polymer only.

A stable dual-functional system of visible-light-driven Ni(ii) reduction to a nickel nanoparticle catalyst and robust in situ hydrogen production

A stable hydrogen photogeneration system containing fluorescein as a photosensitizer with nickel(II) chloride as a catalyst precursor in basic solution was found to undergo in situ photoreduction of nickel(II) to zero-valent Ni nanoparticles to catalyze highly efficient hydrogen evolution under visible light irradiation.

Development of Metallic Nickel Nanoparticle Catalyst for the Decomposition of Methane into Hydrogen and Carbon Nanofibers

Metallic nickel nanoparticles were prepared primarily as catalysts for the thermal decomposition of methane to produce hydrogen. Nickel particle aggregates with controlled crystalline size and primary particle size were prepared first by the precipitation of nickel nitrate and oxalic acid in ethanol solution, followed by the thermal decomposition of nickel oxalate dihydrate under an oxygen-free atmosphere. The concentration of the reactants was found to play a critical role in the morphology and crystalline size of the nickel oxalate dihydrate and subsequently the resulting metallic nickel catalyst. The nickel oxalate dihydrate showed different crystalline sizes and morphologies including nanosheets, nanorods, and nanoneedles, depending on the concentration of the reactants. A series of decomposition atmospheres (CH4–N2 in different ratios) were used to investigate their effects on the morphology and crystalline size of the metallic nickel particles. The addition of CH4 in the gas stream during the nickel...

Size-controlled synthesis of a supported Ni nanoparticle catalyst for selective hydrogenation of p-nitrophenol to p-aminophenol

Abstract We reported a general strategy of size-controlled synthesis of supported nickel nanoparticle catalysts using electroless plating technique. The synthesis conditions (e.g. compositions of plating solution and plating temperatures) were optimized to promote plating rate, and nickel nanoparticles with 9 nm diameter and a narrow size distribution were highly dispersed on TiO 2 . The as-prepared Ni/TiO 2 catalyst showed high activity, selectivity and stability in the selective hydrogenation of p-nitrophenol to p-aminophenol.

Microstructural evolution of nickel nanoparticle catalysts supported on gadolinium-doped ceria during autothermal reforming of iso-octane

The microstructure and composition of a nanoparticle Ni catalyst supported on gadolinium-doped ceria (Ce1−xGdxO(4−x)/2) were studied using transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The support of the fresh catalyst exhibits a homogenous aggregation of crystalline grains, with sizes ranging between 20 nm and 50 nm. The crystalline structure of the fresh catalyst support is of the CeO2 phase, in which gadolinium atoms exist in a solid solution of CeO2. Nickel in the fresh catalyst is highly dispersed and forms granular crystals that are 5–30 nm in size on the surface of the ceria support. The support of the used catalyst exhibits a bimodal distribution of grains in which smaller grains have similar structure and morphology as those in the fresh catalyst, while the larger sized grains appear dull and exhibit nonfaceted crystal morphology resulting either from the sintering of a number of CeO2 grains or by the occupation of highly defective crystals of Ce2O3 and CeO phases. A thin amorphous layer of carbon also covers most of the larger grains in the used catalyst. The Ni particles could not be imaged by TEM in the used catalyst, but energy dispersive x-ray spectroscopy (EDX) detected their presence. The XPS analysis of the catalyst samples suggests the participation of lattice O atoms from the ceria support in the catalytic reaction. The XPS data also show the presence of carbonate species and a higher hydrocarbon concentration in the used catalyst.

Synthesis of alumina supported nickel nanoparticle catalysts and evaluation of nickel metal dispersions by temperature programmed desorption

The purpose of this study was to synthesize highly dispersed Ni/Al 2O 3 catalysts and to develop a suitable hydrogen-temperature programmed desorption (H 2-TPD) method for the determination of nickel metal surface area, dispersion, and crystallite sizes. Several highly dispersed Ni/Al 2O 3 catalysts with a Ni loading between 15 and 25 wt.% were synthesized. The reducibility of catalysts was determined by temperature programmed reduction (TPR) experiments. All catalysts exhibited a single reduction peak with a maximum rate of H 2 consumption ( T max in TPR) occurring below 450 °C. Three different H 2-TPD methods were employed to determine the amount of H 2 chemisorbed. In TPD-1, a 10% H 2/Ar mixture was used for catalyst pre-reduction and surface saturation by cooling down from T max in TPR to room temperature. In TPD-2, the catalyst surface after pre-reduction was flushed with Ar at T max in TPR + 10 °C. The TPD-3 was similar to the TPD-2, but used 100% H 2 instead of 10% H 2/Ar mixture. In all three TPD methods, the profiles exhibited 2 domains of H 2 desorption peaks, one below 450 °C, referred to as type-1 peaks, and attributed to H 2 desorbed from exposed fraction of Ni atoms, and the other above 450 °C, denoted as type-2 peaks, and assigned to the desorption of H 2 located in the subsurface layers and/or to spillover H 2. Flushing the reduced catalyst surface in Ar at T max in TPR + 10 °C in TPD-2 and TPD-3 removed most of the H 2 located in the subsurface layers/ spillover H 2. The amount of H 2 chemisorbed to form a monolayer on the reduced Ni/Al 2O 3 catalysts was determined quantitatively from the TPD peak areas of type-1 peaks in TPD-1, and from both type-1 and type-2 peaks in TPD-2 and TPD-3. The Ni metal surface area, dispersions and crystallite sizes were calculated from the chemisorption data and the values were compared with those obtained using the static chemisorption method. Both TPD-2 and TPD-3 gave chemisorption results similar to that obtained from the static method.