Nickel Salt Precursors Research Articles

The controlled NiO nanoparticles for dynamic ion exchange formation of unique NiS/CdS composite for efficient photocatalytic H2 production

Photocatalytic reaction of water is one way to achieve clean hydrogen energy and high-efficient photocatalysts are essential. A facile and controlled syntheses of NiS/CdS photocatalysts by tuning nickel precursors are presented for improving photocatalytic performance. Ni-containing nanoparticles were prepared from the calcination of nickel salt. Better than Ni and Ni/NiO (unable to transform to NiS completely), NiO nanoparticles serve as nickel precursor to construct NiS via ion exchange process and the tight heterojunctions between NiS and CdS are achieved. The formed NiS/CdS composite exhibits excellent photocatalytic performance for hydrogen production under visible-light irradiation, better than normal NiS/CdS photocatalyst from soluble nickel salt precursor. The present NiO precursor as template with high surface area provides contact sites for CdS and the dynamic formation of NiS, which is conductive to improving crystallinity of NiS and adjusting the heterostructures between NiS and CdS. Various characterizations verify the superiority of the controlled NiS/CdS heterostructures, including the improved light absorption, photoelectrochemical performances and photocatalytic stability. An effective way is provided to enhance photocatalytic activity of metallic sulfide photocatalysts through the regulating of nanoparticles precursors for cocatalysts.

Exploring the influence of nickel precursors on constructing efficient Ni-based CO2 methanation catalysts assisted with in-situ technologies

In this work, a series of Ni-based CO2 methanation catalysts were prepared with different nickel salt precursors. The Ni-AA catalyst with nickel acetylacetonate precursor displayed the highest activity among these catalysts. The in-situ diffused reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) and the online-tandem thermogravimetric mass spectrometry (TG-MS) were performed to investigate the intermediates of the catalyst calcination process. The superior performance of the Ni-AA catalyst could be derived from its special coordinating anion. Furthermore, the rapid deactivation of the Ni-S catalyst with nickel sulfate precursor was attributed to the generation of the Ni3S2 after reduction pretreatment. As for the Ni-Cl catalyst with nickel chloride precursor, its negligible activity could be owing to poisoning effect of the Cl− by the coverage of the catalyst surface. Therefore, the significant role of the metal salt precursor should be preferentially considered when designing the Ni-based catalysts and even other metal based heterogeneous catalysts.

Effect of Additives on Ni‐Based Catalysts for Hydrogen‐Enriched Production from Steam Reforming of Biomass

The catalytic steam reforming of biomass for hydrogen production is investigated in a fixed‐bed reactor. A suitable additive and precursor is found in various additives (cobalt, strontium, and lanthanum) and nickel salt precursors (nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate). Synthesized samples are characterized by X‐ray diffraction (XRD), NH3 temperature‐programmed desorption (TPD), H2 temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM). Results show that Co and La doping of the Ni/Al2O3 catalyst improves the dispersion of surface‐active particles and reduces the particle size, increasing H2 production. The hydrogen volume fraction of La‐modified catalysts with 10% Ni is 38.96%, which is higher than 30.39% for the unmodified Ni/Al2O3 catalyst. The lowest hydrogen yield of Ni–Sr/Al2O3 catalyst is 19.22%. This low catalytic activity is due to the reaction of Ni–Sr/Al2O3 with SiO2 found in biomass ash, which generates silicate without catalytic effect. The silicate melts and adheres to the catalyst surface at a high temperature, inhibiting the catalysis of nickel active sites. The maximum hydrogen yield obtained with nickel acetate as catalyst precursor is 51.41%, which is due to nickel acetate decomposing and forming more NiO in the amorphous state and improving the performance of catalyst.

Formation mechanisms for hierarchical nickel hydroxide microstructures hydrothermally prepared with different nickel salt precursors

Hierarchical nickel hydroxide nanostructures have been hydrothermally synthesized with only hexamethylenetetramine (HMT) as alkaline source and NiCl2, Ni(NO3)2 and NiSO4 as nickel source, respectively. All samples were verified to be of α-Ni(OH)2 phase. The samples produced with NiCl2 or Ni(NO3)2 resembled each other in structure and morphology: the flower-like porous microspheres with an interesting cavity-in-cavity structural characteristic. The product prepared with NiSO4, however, showed two kinds of structures with distinctly different characteristics. One was the flower-like porous microsphere; the other was like a microsphere of knitted brambles, which was probably first reported. The formation mechanisms were explored and attributed to the multiple roles of HMT and the effects of anions. Different from chloride and nitrate ions, sulfate ions could be adsorbed strongly on the surface of nickel hydroxide, which resulted in the formation of bramble-like structure units. This work suggested that combining the selections of alkaline source and anion could be helpful for controlling the structures and morphologies of transition metal hydroxides.

Band Propagation, Scaling Laws, and Phase Transition in a Precipitate System III: Effect of the Anions of Precursors.

In this third part of this work, we study the effect of the nature of the anion (nitrate, chloride, bromide, and sulfate) of the nickel salt precursor on the emerging Liesegang pattern in the nickel hydroxide/ammonia system in agar gel. We show that multiple Liesegang patterns, such as direct, irregular, revert, and pulse, can thereby result from such an effect. The microscopic analysis of the solids in the bands reveals that the different anions, present in the gel and previously thought of as spectator ions, interact chemically and variably with the crystalline solid in the leading band, thus affecting drastically the resulting pattern exhibited by the trailing bands. Moreover, we demonstrate that, in these four systems, the hydrotalcite-like α-Ni(OH)2 in the leading band redissolves to form the brucite-like polymorph β-Ni(OH)2 in the trailing bands via an Ostwald ripening mechanism. The macroscopic features of the various Liesegang patterns in the four anion systems as portrayed by the spacing and width laws are determined for various initial concentrations.

Metal Precursor Dependent Synthesis of NiFe2O4 Thin Films for High-Performance Flexible Symmetric Supercapacitor

Herein, we report the chemical synthesis of NiFe2O4 thin films forming nanosheet-, nanoflower-, and nanofeather-like morphologies using NiCl2·6H2O, Ni(NO3)2·6H2O, and NiSO4·6H2O nickel salt precursors, respectively, while using the same iron salt precursor. A nanostructure formation mechanism is proposed in detail using coordination chemistry theory. Interestingly, nanostructures of NiFe2O4 nanosheets revealed a maximum surface area of 47 m2 g–1, which was higher than those of nanoflowers and nanofeathers (25 and 11 m2 g–1). Similarly, the supercapacitive properties of the individual NiFe2O4 nanosheet-based electrode demonstrated maximum specific capacitance of 1139 F g–1, which is found to be better than that of NiFe2O4 nanoflowers (677 F g–1) and nanofeathers (435 F g–1) in 6 M KOH electrolyte. Furthermore, the symmetric device fabricated using NiFe2O4 nanosheet electrodes and PVA-KOH solid gel electrolyte shows higher specific capacitance of 236 F g–1 with 98% retention after 7000 cycles and higher spe...

High-Performance Hydrogen Evolution Electrocatalyst Derived from Ni3C Nanoparticles Embedded in a Porous Carbon Network.

In this letter, we report a facile self-foaming strategy to synthesize Ni3C nanoparticles embedded in a porous carbon network (Ni3C@PCN) by rationally incorporating a nickel salt precursor into the carbon source. As a novel hydrogen evolution reaction (HER) catalyst, the Ni3C@PCN shows superior catalytic activity with an onset potential of -65 mV, an overpotential of 262 mV to achieve 50 mA cm-2 current density, a Tafel slope of 63.4 mV/dec, and durability over 12 h in acidic media. The excellent performance of the novel 3D composite material along with its low-cost merits is suggestive of great potential for scalable electrocatalytic H2 production.

Preparation and Electromagnetic Absorption Performance of Ni-RGO

Electroless plating was utilized to deposit nickel nanoparticles on the reduced graphene oxide (RGO). By adjusting the nickel salt precursor concentration, three kinds of Ni-RGO with different nickel contents were synthesized, namely Ni-RGO-1, Ni-RGO-2 and Ni-RGO-5. Transmission electron microscopy and X-ray diffrac- tion were employed to study the surface morphology and crystal structure of as-prepared Ni-RGO. The electro- magnetic performance of graphene oxide and Ni-RGO was characterized. The results indicated that the permit- tivity of Ni-RGO was above 8, almost three times higher than that of pristine graphene oxide. Ni-RGO-1 exhib- ited the best electromagnetic wave absorption performance, although the concentration of nickel precursor is the lowest one among three samples. The minimal reflection loss was up to -24.5 dB for Ni-RGO-1 with a thickness of 2 mm.

A versatile ionic liquid-assisted approach to synthesize hierarchical structures of β-Ni(OH)2 nanosheets for high performance pseudocapacitor

This work describes a versatile hydrothermal approach to synthesize different types of hierarchical structures composed of single crystalline β-Ni(OH)2 nanosheets. We use the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BmimCl) as a structure directing agent, which allows the formation of films consisting of β-Ni(OH)2 nanosheets on the nickel foam substrate. It is found that the IL not only controls the formation of the sheet-like structure, but also promotes the growth of the nanosheets on the substrate, building an intimate contact between the active hydroxide film and the conducting metal foam. This IL agent is so effective that such a hierarchical film can also be obtained with different thickness and organization if different nickel salt precursor is used. When these film samples were applied as the electrode materials for pseudocapacitor, they exhibited promising capacitive properties with a high capacitance of about 700Fg⿿1 even at a high charge-discharge current rate of 5 Ag⿿1 for prolonged cycling.

Capacitance performance of nanostructured β-Ni(OH)2 with different morphologies grown on nickel foam

Nanostructured β-Ni(OH)2 with different morphologies are successfully grown on nickel foam using a template-free method by adjusting the anions of nickel salt precursors. The morphology is examined by scanning electron microscopy and the phase structure is analyzed by X-ray diffraction (XRD). The surface area is calculated with the Brunauer–Emmet–Teller (BET) model and the pore size distribution is determined with the Barett–Joyner–Halenda (BJH) method. The microstructure of β-Ni(OH)2 remarkably depends on the nickel salt precursors including Ni(NO3)2, NiCl2 and NiSO4. The electrochemical behaviours of β-Ni(OH)2 electrodes are investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy in 6moldm−3 KOH solution. Results show that the β-Ni(OH)2/Ni-foam electrode prepared with NiSO4 exhibits the largest specific capacitance (1025.3Fg−1 at a current density of 1.0Ag−1), best reversibility and lowest charge transfer resistance due to its largest porosity and surface area.

Effect of nickel salt precursors on morphology, size, optical property and type of products (NiSe or Se) in hydrothermal method

NiSe micro/nanocrystals with multiform morphologies, including particles, rods and flowers were prepared by hydrothermal method from different Ni salts: NiBr2, Ni(ClO4)2⋅6H2O, NiCl2⋅6H2O and NiSO4⋅6H2O. Se nanorods were produced simply by varying the nickel salts to Ni(CH3COO)2⋅H2O and Ni(NO3)2⋅6H2O. The process was performed at 180°C for 12h and cetyltrimethyl ammonium bromide (CTAB) and hydrazine hydrate (N2H4⋅H2O) used as surfactant and reductant, respectively. The samples were analyzed by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electronic diffraction (SAED) and X-ray energy dispersive spectroscopy (EDS). The synthesis was performed conveniently and safely.

Spontaneous Formation of Hierarchically Structured Curly Films of Nickel Carbonate Hydrate through Drying

Novel curly nickel carbonate hydrate film superstructures can be prepared for the first time via a facile drying process of the films formed on air/solution interface in the presence of double hydrophilic copolymer or polyelectrolyte additives. As-prepared curly film patches with average edge sizes of several hundred micrometers display adjustable curly features along different orientation. The coiling up degree of the film edges is strongly dependent on the polymer concentration in bulk solution. Most of these curly structures have a relatively smooth outer surface; however, the microstructures of the outer surface of curly films formed show porous network-like features. In addition, using different kinds of nickel salts can produce distinct curly film samples. A possible formation mechanism of the curly film structure has been proposed. The multiple interaction modes between nickel salt precursors and polymer can favor the self-organization of the film formed at the air/solution interface. This approach is expected to be extended for producing a variety of curly hierarchical structures.

Influences of different nickel salt precursors on the catalytic performance of the Ni/C catalysts for vapor-phase carbonylation of ethanol

Influences of different nickel salt precursors on the catalytic performance of the Ni/C catalysts for vapor-phase carbonylation of ethanol

Influence of Nickel Salt Precursors on the Hydrogenation Activity of Ni/γ-Al2O3 Catalyst

Abstract The structure and catalytic properties of the supported Ni/γ-Al 2 O 3 catalyst prepared with different nickel salt precursors for hydrogenation of a-pinene have been studied using X-ray diffraction, UV–VIS diffuse reflectance spectroscopy, temperature-programmed reduction, CO chemisorption, and microreactor tests. It has been shown that the catalytic hydrogenation activity of the Ni/γ-Al 2 O 3 catalyst increases with increasing Ni loading, and the catalytic activity of the nickel acetate-derived Ni/γ-Al 2 O 3 catalyst is much higher than that of the nickel nitrate-derived catalyst. The catalyst characterization results indicate that the different catalytic hydrogenation activity of Ni/γ-Al 2 O 3 prepared with different nickel salt precursors is correlated to the different ratio of Ni 2+ ions in the tetrahedral and octahedral vacancies of γ-Al 2 O 3 and the different reduction degree of the NiO/γ-Al 2 O 3 precursors. When the nickel ion loading is far below the dispersion capacity, the supported nickel ions preferentially incorporate into the tetrahedral vacancies of γ-Al 2 O 3 . With increasing nickel loading, the ratio of Ni 2+ ions that incorporate into the octahedral vacancies of γ-Al 2 O 3 increases. The dispersion capacity of nickel ions on γ-Al 2 O 3 derived from nickel acetate is lower than that of the sample derived from nickel nitrate due to the greater shielding effect of acetate anions than nitrate anions. Moreover, the ratio of octahedral Ni 2+ to tetrahedral Ni 2+ on the nickel acetate-derived sample is higher than that on the nickel nitrate-derived sample because of the lower density of octahedral vacancies on γ-Al 2 O 3 . As octahedral Ni 2+ ions are easier to be reduced to the metallic state than tetrahedral Ni 2+ ions, the catalytic activity of the Ni/γ-Al 2 O 3 catalyst prepared with the nickel acetate precursor is much higher than that of the catalyst prepared with the nickel nitrate precursor with the same nickel loading.

Characterization of nickel catalysts by chemisorption techniques, x-ray diffraction and magnetic measurements: Effects of support, precursor and hydrogen pretreatment

Two series of supported nickel catalysts were prepared by using alumina, silica and titania as supports and nickel nitrate or nickel chloride as impregnating salts. The catalysts, prereduced with hydrogen in the range 300–700°C, were characterized by adsorption of hydrogen and oxygen, X-ray diffraction (XRD) and magnetic methods. Strong effects of the nature of the support, of the nickel salt precursor and, in a few instances, of the reduction temperature on the adsorptive and textural properties of nickel catalysts were observed. For the series prepared from nickel nitrate, alumina support gave the highest dispersions of nickel, which varied only slightly with the reduction temperature, whereas the dispersion of titania-supported catalysts decreased significantly when the reduction temperature was increased. In contrast, the series prepared with nickel chloride always exhibited low metal dispersions which were nearly independent of the nature of the support and the reduction temperature. A strong decrease in hydrogen adsorption was observed on all samples prepared from nickel chloride. This decrease was recorded, for the nitrate preparation series, only on Ni/TiO 2 reduced at 500 and 700°C and on Ni/SiO 2 reduced at 700°C, which, in this instance, may be related to a strong metal-support interaction. On the other hand, oxygen chemisorption took place on all catalysts, allowing the determination of their metallic dispersion. Nickel crystallite sizes calculated from oxygen chemisorption were in good agreement with those determined from XRD and magnetic measurements, provided that the adsorption stoichiometry O/Ni s=2 is assumed for typical catalysts whereas O/Ni s = 1 should be applied to Ni/TiO 2 under the strong metal-support interaction state.

Joint studies by X-ray photoelectron spectroscopy and analytical electron microscopy of the dispersion of nickel oxide supported on silica and silica–aluminas

The dispersion of nickel oxide, NiO, supported on a series of silica and silica–alumina carriers covering the range 100–0 % SiO2 has been investigated by photoelectron spectroscopy (X.p.s.) and analytical electron microscopy (a.e.m.). The results show that according to the nature of the support, two situations may arise: (1) With NiO on SiO2, the active phase is present as badly dispersed NiO aggregates. No surface compound or dispersed phase can be detected. (2) With NiO on SiO2–Al2O3, the supported phase exists in two forms: NiO aggregates and a dispersed phase. Increasing the Al2O3 content of the carrier leads to an increase in the concentration of the dispersed phase and a decrease in the average size of NiO aggregates.The results were interpreted on the basis of the interaction between the nickel salt precursor and the support during impregnation and heat treatment.