Nickel Nitrate Solution Research Articles

Fabrication of a Ni/MgO Nanocomposite Catalyst by Exolution

Methane steam reforming reaction is the most important chemical process to produce hydrogen or synthesis gas. Hydrogen is heavily consumed for ammonia production, the cryogenics industry and methanol production. Recently, the hydrogen demand is expected to increase as fuel cells become more widely accepted and are used more in the near future. For effective production of hydrogen or synthesis gas, the role of the reforming catalyst becomes more significant. Especially, highly active and stable catalyst is necessary for an on-site reformer for fuel cell systems. In conventional technology, the methane steam reforming reaction is conducted on supported noble metals- (Pt, Pd, Rh, Ru, and Ir) or nickel-based catalysts at temperature up to 700~800°C and steam to methane rations between 2 and 4. However, these catalysts suffer from the deactivation by agglomeration and carbon deposition. Noble metal-based catalysts are less sensitive to carbon deposition than nickel-based catalyst. However, high cost and limited availability are major concern. In this study, nickel-based nanocomposite catalysts were fabricated by exolution process. The exsolution means the process to precipitate particles from solid solution by means of the heat treatment in a specially-controlled atmosphere. This process is distinguished from the infiltration in which particles are precipitated from solutions by evaporation. First, Mg1-xNixO solid solution powders were synthesized from aqueous magnesium and nickel nitrate solution by precipitation technique and then the powder was heat-treated in reducing atmosphere at 600 to 900°C. SEM and TEM images revealed that the nano-sized nickel particles were homogeneously dispersed in the Mg1-xNixO solid solution matrix and the size and morphology of nano nickel particles can be controlled by the heat-treatment condition. Catalytic activity for the methane steam reforming or methane particle oxidation reaction and durability of the Ni/Mg1-xNixO was investigated in terms of nickel contents and sizes. Figure 1

CeO2 - ZrO2 Catalysts for the Use of Biogas in IT-SOFC

SOFC technology is a valid approach to promote the transition from an oil based world economy to a carbon free society. For this purpose is demanding to develop SOFC anodes that operate at intermediates temperatures (550-700°C) and with renewable resources, such as biogas (60% CH4, 40% CO2) coming from fermentation of biomasses and agricultural wastes [1]. Biogas can be directly reformed into the anodic compartment or in an external reformer using appropriate catalysts, being active in the dry (DR) and oxidative dry (ODR) reforming [2,3]. As preliminary study, this work investigated the reactivity of defined ceria-zirconia compositions towards the dry reforming reaction under IT_SOFC conditions, with the aim to design a suitable anode directly fed with biogas. This requires to develop compositions able to reduce side reactions such as the reverse water gas shift, which consumes part of produced H2, methane cracking or Boudouard reactions that form carbon with a consequent deactivation of the catalyst. Considering this purpose mesoporous compositions, Ce0.8Zr0.2O2 (CZ80) and Ce0.8Zr0.13La0.5Nd0.2O2-x (LN_CZ80), were prepared with a proprietary surfactant assisted method [4]. The materials were used to prepare nickel-based catalysts with two different metal loadings. The effects of dopants and nickel content on the chemical-physical and catalytic properties of the materials were investigated. Fresh powders (500°C/4 h) were calcined at 800°C/3 h, then impregnated with a nickel nitrate solution up to obtain a metal loading of 3.5 and 7 wt% respectively, and the final catalysts were calcined at 800°C/3 h. All materials were extensively characterized by conventional techniques (X-Ray Diffraction, Temperature Programmed Reduction, B.E.T. and BJH methods). The dry reforming tests were performed in a fixed-bed quartz reactor at atmospheric pressure. The catalysts were diluted with quartz, and previously reduced at 800°C/1 h in a pure H2 flow. The reaction feed consisted of CH4/CO2 mixtures; small amount of N2 were used as internal standard. The reaction was studied in the temperature range between 600-700°C at 12000 h-1GHSV. Reactants and products were analyzed with a microgas-chromatograph equipped with a TCD, a molecular sieve and a polar PLOTQ columns. The catalytic tests were performed with two different CO2/CH4 ratios: 50/50 and 40/60. Figure below shows results obtained testing materials with the former mixture. It is possible to observe that in the range of temperature investigated the conversion of CO2 is always higher than the conversion of CH4. Ni-CZ80 is not active at low temperature even using a 7 wt.% metal loading, while the doped material shows an appreciable conversion also with a 3.5 wt% Ni amount. The presence of dopants contributes to increase the conversion of both reactants, obtaining conversion of 42% and 60% at 670°C respectively for CH4 and CO2 for supports loaded with 7 wt.% of nickel. Results obtained with a 40/60 CO2/CH4 ratio showed a similar trend, but we observed a large formation of carbon. These results suggest that the addition of La and Nd in the CZ80 lattice not only improves the surface basicity of support, activating CO2, but also enhances the nickel dispersion, thus favoring CH4 conversion. The modifications induced on the surface by dopants strongly influence the interplay between support, metal and gas: a lower Ni loading is necessary to obtain CH4 conversion at low temperatures. Further investigations are undergoing to investigate the behavior of these materials under ODR conditions [2,5]. The effects on carbon formation and on the endothermicity of DR will be studied in order to fully evaluate the potential application of these materials as anodic catalysts in IT-SOFC.

Low Ni-Containing Anodes Using Titanate-Based Perovskites for Methane Direct Internal Reforming Power Generation

Direct internal reforming SOFCs (DIR-SOFCs), which directly utilize hydrocarbons as fuels in the anode, can achieve high power generation efficiency due to chemical recuperation of the anodic reaction heat by endothermic reforming reactions. DIR-SOFCs often suffer from carbon deposition on the anode and the resultant severe degradation of power generation performance and stability [1]. Nickel contained in SOFC anodes as an electronic conductor acts as catalytic sites for carbon decomposition in the first step of hydrocarbon fuel conversion. Accordingly, these Ni-related issues can be lessened by reducing the Ni content in the anode. In this study titanate-based Ni-cermet anodes such as Ni-LaxSr1-xTiO3+ d (LST) have been investigated as an alternative anode to conventional Ni-YSZ cermets. LST is a mixed ionic and electronic conducting material with a relatively high electronic conductivity of the order of 10 S/cm2[2]. Ni-LST anodes were fabricated by a conventional method using a ball mill and by an impregnation method, and the stability as well as tolerance to carbon deposition of the anodes were evaluated. Titanate-based perovskites ware prepared via Pechini method. A desired amount of the respective nitrates and acetates were mixed with titanium isopropoxide and citric acid, and then dissolved in ethylene glycol. The mixture was heated to 150ºC on a hot stirrer to complete the polymerization of the mixture. The resultant powder was calcined in air at 800ºC for 3 h to form a perovskite oxide. The obtained powders were mixed with NiO particles at a desired ratio, and ball-milled for 24 h, followed by calcination at 1200°C for 5 h in air. The thus prepared cermets were pulverized into powder, and then mixed with polyethylene glycol to form slurry, with which an YSZ disk of 20 mm in diameter and 0.5 mm in thickness was painted in a circular shape of 6 mmφ as an anode using a screen. Then the disk was calcined at a desired temperature for 5 h in air. In addition, Ni cermets were prepared by an impregnation method. LST powders prepared by the Pechini method were impregnated with an aqueous solution of nickel nitrate on a steam bath at 80°C, dried, and then calcined at 1000 ºC in air for 2 h. Thus obtained Ni-LST powder was used to prepare the anode in the same manner as conventional cermets. Current-voltage characteristics of the anode was evaluated at 1000 ºC by feeding humidified H2 and dry O2 to anode and cathode, respectively, at 100 ml/min. Direct internal reforming power generation performance was measured by feeding steam-to-carbon ratio of 0.1 under constant current load of 200 mA/cm2. The durability of the cells was evaluated by AC impedance spectra measured under open circuit condition at 1000 ºC with a Princeton VersaSTAT3 in humidified H2 feed before and after the power generation at S/C = 0.1. Figure 1 shows current-voltage characteristics of SOFCs with Ni-LST and Ni-YSZ anodes prepared by the ball-mill and impregnation methods. The power generation characteristics of 60wt%Ni-LST prepared by the ball-mill method was slightly lower than that of 60wt%Ni-YSZ by the ball-mill method, but still high performance was observed over the 60wt%Ni-LST. On the other hand, when the nickel content was decreased to 40wt% in Ni-YSZ by the ball-mill, a significant deterioration of power generation characteristics was observed over the Ni-YSZ anode, while Ni-LST prepared by the impregnation method maintained power generation performance despite the low Ni content of 10wt%. The durability of 60wt%Ni-LST by the ball-mill method and 10wt%Ni-LST by the impregnation method was evaluated by feeding a steam-methane mixture at S/C = 0.1 at 1000 ºC under a constant current load of 200 mA/cm2. A gradual decrease in the terminal voltage appeared for 60wt%Ni-LST anode, and a large increase in the impedance was found on the impedance spectra after CH4/H2O direct reforming power generation. In contrast, 10wt%Ni-LST by the impregnation method exhibited a stable power generation characteristics under the low S/C of 0.1 and constant current load of 200 mA/cm2. The impedance became slightly smaller after the power generation.

Дослідження кінетики осадження нікелю з розчину

Background. In the nickel-containing catalysts production there is the technological stage of the intermediate insoluble nickel compounds. The studies of the nickel precipitation kinetics by the urea from the nickel nitrate solution were carried out that are useful for the design and characteristics calculation of these processes,Objective. The purpose is in constructing of mathematical model for the nickel precipitation process.Methods. A thermodynamic evaluation of possible reactions in solution was carried out. In isothermal conditions at the temperatures of 90 and 100 °C the kinetic curves of nickel precipitation from solutions were obtained at different initial concentrations. On the curves several sections were marked: the induction period and the main reaction period that are analyzed by different methods. The dependence of the induction period value from the conditions of the process was analyzed using multiple regression approach. The kinetic equation of first order reaction was chosen for the main period and the temperature dependence of the rate according to Arrhenius equation was determined.Results. It is established that the value of the induction period depends on the process temperature and the concentration of nickel, the regression equation was obtained. It is shown that the basic section of the precipitation process kinetic curves are described by the equation of the first order at the different initial concentrations of metal in all the investigated temperature range, reaction rate constant of the first order and the activation energy of the process were calculated.Conclusions. The proposed kinetic model of precipitation that consists of equations system for calculating the time of reaction was obtained. The value of the activation energy of the process indicates a kinetic stage of process tendency.

NiWS/Al2O3 hydrotreating catalysts prepared with 12-tungstophosphoric heteropolyacid and nickel citrate: Effect of Ni/W ratio

Effect of Ni/W ratio on Ni-CA-PW/Al2O3 hydrotreating catalysts prepared with 12-tungstophosphoric heteropolyacid (PW-HPA) and nickel citrate was investigated. For comparison, the reference samples were prepared using nickel salt of PW-HPA and co-impregnating solution of ammonium metatungstate and nickel nitrate. All synthesized catalysts were characterized by N2 physisorption, X-ray powder diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in hydrotreating of dibenzothiophene, naphthalene and quinoline. It was found that with the rise of Ni content in the prepared Ni-PW/Al2O3 catalysts the composition and morphological characteristics of the NiWS active phase species as well as their catalytic properties were changed simultaneously. Turnover frequency (TOF) number in all studied reactions increased with the decrease in both the average length of the NiWS phase species and Ni/W ratio in the (Ni)WS2 edges. Both NiW reference catalysts had active sites with lower TOF values than their counterparts prepared using PW-HPA and nickel citrate. The highest TOF values were achieved at moderate Ni/(Ni+W) ratio equal to 0.24. However, maximal conversions of the reactants were observed over the catalysts with higher Ni/(Ni+W) ratio equal to 0.33–0.45. The possible reasons of these changes are discussed in the paper.

Template-based synthesis of nickel oxide

Nanocrystalline NiO has been produced using a facile template-based synthesis from nickel nitrate solutions using cellulose as a template. Thus obtained oxides were studied by scanning electron microscopy, x-ray diffraction, Raman scattering spectroscopy, photoluminescence spectroscopy and confocal spectromicroscopy. The filamentary/coral morphology of the samples has been evidenced and is built up of agglomerated nanocrystallites with a size in the range of about 26-36 nm. The presence of two-magnon contribution in Raman scattering spectra suggests the existence of antiferromagnetic ordering at room temperature. Finally, the observed near-infrared photoluminescence band at 850 nm has been tentatively attributed to the defect-perturbed Ni2+ states at the surface.

Carbon periodic cellular architectures

The first carbon periodic cellular architectures derived from 3D printing, in the form of new tetrakaidecahedra meshes, are reported and investigated in this paper. They were prepared in hydrothermal conditions by a template method based on polymer periodic structures of the same geometry, and fabricated by a 3D printer using photocurable resin. Several formulations based on resorcinol–formaldehyde were tested, and the best ones were those using low concentrations of resorcinol at 150°C in a pressurised solution of nickel nitrate. After pyrolysis at 1000°C, catalytic graphitisation was demonstrated by TEM, XRD and Raman studies. The higher was the amount of nickel, the higher was the resultant graphitisation level. Mechanical tests were also carried out on such extremely lightweight periodic carbon structures, showing that these new materials present a much higher modulus than carbon foams of similar bulk densities.

Facile fabrication of various zinc-nickel citrate microspheres and their transformation to ZnO-NiO hybrid microspheres with excellent lithium storage properties.

Zinc-nickel citrate microspheres are prepared by a simple aging process of zinc citrate solid microspheres in nickel nitrate solution. As the concentration of nickel nitrate solution increases, the morphology of the produced zinc-nickel citrate evolves from solid, yolk-shell to hollow microspheres. The formation mechanism of different zinc-nickel citrate microspheres is discussed. After annealing treatment of the corresponding zinc-nickel citrate microspheres in air, three different ZnO-NiO hybrid architectures including solid, yolk-shell and hollow microspheres can be successfully fabricated. When applied as the anode materials for lithium ion batteries, ZnO-NiO hybrid yolk-shell microspheres demonstrate the best electrochemical properties than solid and hollow counterparts. After 200th cycles, ZnO-NiO hybrid yolk-shell microspheres deliver a high reversible capacity of 1176 mA h g−1. The unique yolk-shell configuration, the synergetic effect between ZnO and NiO and the catalytic effect of metal Ni generated by the reduction of NiO during discharging process are responsible for the excellent lithium storage properties of ZnO-NiO hybrid yolk-shell microspheres.

Fine-tuning B-site of a Chromite based Perovskite Catalyst for Steam Reforming of Glycerol

ABSTRACTThe perovskite catalysts La0.75Sr0.25Cr0.5X0.5O3±δ (where X= Mn, Fe and Co) were prepared by combustion synthesis and the influence of transition metals B-site substitution on the structural and catalytic properties of the catalysts in steam reforming of both pure and by-product glycerol to produce hydrogen-rich gases for utilization in solid oxide fuel cell was investigated. All the catalyst systems were found very active and selective with the Fe-substituted catalyst slightly more active. Hydrogen yield and coke suppression was better in the Mn-substituted catalyst which was also structurally more stable in fuel environment. Impregnation of Ni into the lattice structure of the pre-reacted both A-site and B-site stoichiometric catalysts from nickel nitrate solution and subsequent redox exsolution of Ni nano particles supported on the oxide surface of the materials has significantly improved the hydrogen yield by enhancing water-gas-shift reaction (WGSR). Thus, extent of the exsolution phenomenon observed in the materials followed the order LSCM > LSCC > LSCF.

Thermodynamic parameters of complexation reactions between nickel(II) ion and L-serine in aqueous solutions

A thermochemical study of coordination equilibria in the nickel(II) ions-L-serine system was carried out. The heats of reaction between solutions of an amino acid and nickel(II) nitrate at 288.15, 298.15, and 308.15 K and ionic strength of 0.25, 0.50, and 0.75 (KNO3) were measured. The heats of dilution of nickel nitrate solution in background electrolyte solutions were determined under identical conditions to make proper corrections. The results were processed with allowance for stepwise equilibria. The standard thermodynamic parameters of the complexation processes were calculated. The effect of temperature on heats of complexation reactions in the L-serine-nickel(II) ions was studied. The standard enthalpies of formation of NiSer+, NiSer2, and NiSer3− complexes in aqueous solutions were determined.

Deactivation of nickel catalysts in methane cracking reaction: Effect of bimodal meso–macropore structure of silica support

In this research, the pore characteristics of catalyst supports have been taken into consideration in order to prolong the life time of catalysts from coke deposition in methane cracking reaction. Consequently, the monomodal porous silica supports with straight pore (SBA-15) and sinusoidal pore (Xerogel-5) of similar mesopore size, and bimodal porous silica supports with straight pores (MCM-41) and sinusoidal pores (BPS-5) of different pore sizes were applied as the supports for nickel catalyst. An aqueous solution of nickel nitrate (Ni(NO3)2·6H2O) was used as the catalyst precursor and loaded onto the supports by using incipient wetness impregnation method. The performance and life time of the obtained catalysts in methane cracking reaction were investigated using a fixed-bed reactor at a temperature range of 500–650 °C at atmospheric pressure (CH4 diluted with N2 at a volume ratio of 1:4). The highest methane conversion and longest catalyst life time were obtained at a lower reaction temperature (500 °C) with Ni/BPS-5 catalyst, as its effective diffusion coefficient was approximately 8.5 times higher than that of Ni/Xerogel-5 catalyst. Moreover, the catalyst with straight pore (Ni/SBA-15) exhibited a slightly higher effective diffusion coefficient and catalytic performance than that with sinusoidal pore (Ni/Xerogel-5).

Performance Improvement of Hydrogen Peroxide Sensor via Cadmium Doped Nickel Oxide Modifying N-Silicon Electrode

Cadmium ion doping was carried out during electrochemically cathodic plating nickel hydroxide on platinum films coated n-silicon (Pt/n-n+-Si electrode) in 0.1 M nickel nitrate solution containing 0.035 M cadmium nitrate. The morphology and composition of the products were characterized by scanning electron microscope (SEM) and x-ray photoelectron spectroscopy (XPS), respectively. A two-electrode cell based on Cd-doped NiO/Pt/n-n+-Si electrode and a platinum counter has been used for determination of hydrogen peroxide in absence of reference electrode by photocurrent measurement at a zero bias. The emphasis is laid on that the cadmium doping remarkably improves the sensibility of the photoelectrochemical hydrogen peroxide sensor. Under optimizing conditions a sensitivity of 254.6 μA mM-1 cm-2 and a linear response range from 0.02 mM up to 0.12 mM with a determination limit of 2.0 μM were achieved in a potassium hydroxide (KOH) solution at pH =13.3.

An in situ colorimetric measurement study of electrochromism in the thin-film nickel hydroxide/oxyhydroxide system

Electrochromic thin-film ‘hydrous nickel oxide’ (nickel hydroxide) was deposited on fluorine-doped tin oxide (FTO)/glass substrates by galvanostatic electrochemical reduction at −0.1 mA cm−2 for 100, 400 and 800 s from aqueous 0.01 mol dm−3 nickel nitrate solution. Following transfer to aqueous 0.1 mol dm−3 potassium hydroxide, the transmittance and absorbance changes, colouration efficiencies and stability to multiple potential cycling were measured on reversibly electrochemically switching the transmissive light green (essentially ‘bleached’) ‘hydrous nickel oxide’ to the deep brown (‘coloured’) nickel oxyhydroxide redox state. The ‘hydrous nickel oxide’ (as deposited) films showed excellent transmittance modulation, achieving a maximum Δ%T of 83.2 at 432 nm, for the highest deposition time (800 s) studied. Colouration efficiency (CE) values were ∼30 cm2 C−1, with response times of 12.0 s (colouration) and 9.5 s (‘bleaching’). Using the Commission Internationale de l’Eclairage (CIE) system of colorimetry, the colour stimuli at rest, and on dynamically reversibly switching between the electrochromic redox states were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in hue and saturation occur, as shown by the track of the CIE 1931 xy chromaticity coordinates, together with a sharp decrease in luminance on oxidation. CIELAB L*a*b* coordinates were also used to quantify the colour of the electrochromic films. A combination of a low L*, and positive a* and b* values, quantified the perceived deep brown ‘coloured’ state.

Thermodynamic characteristics of complex formation by Ni2+ ions and glycylglycine in aqueous solutions of KNO3 at 288–308 K

Heat effects of the interaction between glycylglycine and nickel (II) nitrate solutions are measured by direct calorimetry at different pH values and metal: ligand ratios in the temperature range of 288.15 to 308.15 K. KNO3 is used as the background electrolyte. The heat effects of diluting the nickel nitrate solution in solutions of the background electrolyte are determined in order to make the appropriate corrections. The standard thermodynamic characteristics of complex formation by peptides and nickel (II) ions in aqueous solution are calculated. Standard enthalpies of the formation of complex particles NiPep+, NiPep2, and NiPep3− are determined for the first time.

Influence of CTAB on morphology, structure, and supercapacitance of β-Ni(OH)2

Cetyltrimethylammonium bromide (CTAB) was used as surfactants to modify the crystallization of β-Ni(OH)2 via a simple ammonia-evaporation/CTAB-induced method onto nickel foam by using a mixed aqueous solution of nickel nitrate, CTAB, and ammonia. Their structure and surface morphology are characterized by X-ray diffraction and scanning electron microscopy. The SEM images show changes in the microstructure of β-Ni(OH)2, and the XRD patterns exhibit a much higher relative diffraction intensity of (1 0 0) peaks with the addition of CTAB. The effects of CTAB content on the electrochemical behaviors of β-Ni(OH)2 are investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The results demonstrate that the modified β-Ni(OH)2 electrode has better electrochemical performance, such as better reaction reversibility, higher proton diffuse coefficient, higher specific capacity, and better cyclic stability. Importantly, when the CTAB content in the initial solution was 0.03 g, the results show a drastic improvement in the capacitive characteristics of β-Ni(OH)2 with a specific capacitance increases from 386 to 1,019 F g−1 at a high charging/discharging current density of 6 A g−1.

Paper spray ionization for ambient inorganic analysis

The feasibility of using paper spray ionization as an ambient ionization method for inorganic analysis was investigated. Aqueous solutions were spotted onto paper triangles and high voltage was applied to induce electrospray. In-source collision-induced dissociation assisted in breaking up clusters to produce mass spectra dominated by atomic ions and their corresponding oxides and hydroxides and high-resolution exact mass measurements were used to identify atomic ions in the presence of organic interferences. A feasibility test with a standard inductively coupled plasma mass spectrometry (ICP-MS) test mixture demonstrated detection of 21 of 23 elements as M(+•) or [M + OH](+). The two undetected elements (boron and lithium) were below the minimum detectable m/z setting for the time-of-flight mass spectrometer used for these experiments. Untreated filter paper showed residual contamination from group I and group II elements. Excellent linearity was observed over the concentration range 0.1-1000 ppm for nickel(II) nitrate solutions containing 10 ppm cobalt(II) nitrate as internal standard. The method was applied to the analysis of lead-free solder, a bismuth subsalicylate tablet, permanent magnet materials and lead chromate pigment in a three-cent US postage stamp issued in 1948. Paper spray ionization was successfully applied to qualitative inorganic analysis. Quantitative analysis was shown to be possible with the use of internal standards. Initial detection limits were much higher than for comparable inductively coupled plasma and glow discharge methods, ranging from the high parts-per-billion range to the low parts-per-million range. The detection limits for some elements were limited at low levels by the presence of interferences that were not separated by the resolving power of the mass spectrometer. Despite these limitations, the simplicity and potential portability of paper spray may find some applications for elemental analysis.

Determination of the “NiOOH” charge and discharge mechanisms at ideal activity

Optimization of electrodeposition conditions produced Ni(OH)2 deposits chargeable up to 1.84±0.02 e− per Ni on and the resulting nickel oxide/hydroxide active material could subsequently deliver 1.58±0.02 e− per Ni ion (462mAh/g) over a potential range <0.2V. The ability of the “NiOOH” active material to deliver an approximately ideal charge and discharge facilitated a coulometric and thermodynamic analysis through which the charge/discharge mechanisms were determined from known enthalpies of formation. The (dis)charge states were confirmed with in situ Raman spectroscopy. The mechanisms were additionally evaluated with respect to pH and potential dependence, charge quantities, hysteresis, and fluoride ion partial inhibition of the charge mechanism. The results indicate that the “NiOOH” (dis)charges as a solid-state system with mechanisms consistent with known nickel and oxygen redox reactions. A defect chemistry mechanism known for the LiNiO2 system also occurs for “NiOOH” to cause both high activity and hysteresis. Similar to other cation insertion nickel oxides, the activity of the “NiOOH” mechanism is predominantly due to oxygen redox activity and does not involve the Ni4+ oxidation state. The “NiOOH” was produced from cathodic electrodeposition of Ni(OH)2 from nickel nitrate solutions onto highly oriented pyrolytic graphite at ideal electrodeposition current efficiencies and the deposition mechanism was also characterized.

Hydrodechlorination of 1,2-dichloroethane on nickel loaded Beta zeolite modified by copper: Influence of nickel and copper state on product selectivity

Influence of copper addition to nickel containing zeolite on activity and product selectivity in the hydrodechlorination of 1,2-dichloroethane was investigated. Ni2.0SiBEA and Cu2.0Ni2.0SiBEA zeolites were prepared by a two-steps postsynthesis method which consist of (1) creation of vacant T-atom sites by dealumination of calcined BEA zeolite with nitric acid and then (2) impregnation of as resulting SiBEA with aqueous nickel nitrate solution or co-impregnation with aqueous nickel and copper nitrate solution, respectively. Calcination at 773K for 3h in air and then reduction at 873K over 3h in flowing 10% H2/Ar of Ni2.0SiBEA and Cu2.0Ni2.0SiBEA, with an isolated pseudo-tetrahedral Ni(II) and Cu(II) species incorporated into BEA framework, leads to formation of red-C-Ni2.0SiBEA and red-C-Cu2.0Ni2.0SiBEA catalysts with very well dispersed metal nanoparticles. The state of nickel and copper in catalysts after calcination, reduction and reaction was characterized by XRD, low-temperature N2 sorption, TPR and XPS. The red-C-Ni2.0SiBEA and red-C-Cu2.0Ni2.0SiBEA catalysts were active in hydrodechlorination of 1,2-dichloroethane with very high selectivity into ethylene (90 and 96% respectively), desired product of this reaction. Thus, the simultaneous introduction of copper and nickel ions in SiBEA in the second step of postsynthesis procedure allows obtaining bimetallic red-C-Cu2.0Ni2.0SiBEA catalyst with well dispersed, separated Cu and Ni particles with higher selectivity toward ethylene than red-C-Ni2.0SiBEA catalyst. TEM experiments have shown that after catalytic run a very small agglomeration of metal particles took place. According to TPH and XPS measurements chlorine containing species are present in spent zeolite catalysts.

Remarkable effect of postsynthesis preparation procedures on catalytic properties of Ni-loaded BEA zeolites in hydrodechlorination of 1,2-dichloroethane

Ni2.0SiBEA and Ni2.0HAlBEA zeolites were prepared by two different procedures: (i) a two-step postsynthesis method that consist of (1) creation of vacant T-atom sites by dealumination of HAlBEA (Si/Al=17) with nitric acid and then (2) impregnation of as resulting SiBEA (Si/Al>1300) with aqueous nickel nitrate solution and (ii) conventional wet impregnation of HAlBEA (Si/Al=17) respectively. The calcination of Ni2.0SiBEA and Ni2.0HAlBEA at 773K for 3h in air led to the formation of C-Ni2.0SiBEA and C-Ni2.0HAlBEA with appearance, for the former mainly pseudo-tetrahedral Ni(II) incorporated in BEA framework and for the latter, pseudo-tetrahedral and extra-framework octahedral Ni(II) as evidenced by XRD, DR UV–vis and XPS. After reduction at 873K for 3h in flowing 10% H2/Ar, red-C-Ni2.0SiBEA and red-C-Ni2.0HAlBEA were obtained and investigated as the catalysts in hydrodechlorination of 1,2-dichloroethane at 523–543K. The activity of the catalysts carried out at atmospheric pressure depended on the reaction temperature, nature of nickel species present in C-Ni2.0SiBEA and C-Ni2.0HAlBEA, acidity of zeolites, distribution and size of nickel nanoparticles present in red-C-Ni2.0SiBEA and red-C-Ni2.0HAlBEA catalysts. Selectivity to desired product – ethylene was very high for red-C-Ni2.0SiBEA (∼90%) and low for red-C-Ni2.0HAlBEA (maximally 30%). The latter catalyst promoted strongly formation of vinyl chloride (up to ∼70%). We have shown that prepared by two-step postsynthesis procedure red-C-Ni2.0SiBEA was more resistant to sintering during hydrodechlorination of 1,2-dichloroethane than red-C-Ni2.0HAlBEA prepared by conventional wet impregnation.

Preparation and electrochemical performances of nanostructured CoxNi1−x(OH)2 composites for supercapacitors

Nanostructured CoxNi1−x(OH)2 (x = 0, 0.053, 0.068, 0.116, 0.192) composites are synthesized via a simple template-free growth process onto nickel foam by using a mixed aqueous solution of nickel nitrate, cobalt nitrate and ammonia. Their structure and surface morphology are characterized by X-ray diffraction, energy dispersive X-ray spectroscopy and scanning electron microscopy. The SEM images show changes in the microstructure of β-Ni(OH)2 by the doping of cobalt. The effects of cobalt content on the electrochemical behaviors of β-Ni(OH)2 are investigated by cyclic voltammetries, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The results show that the Co0.116Ni0.884(OH)2 composite electrode exhibits a drastic improvement in the capacitive characteristics of β-Ni(OH)2 with a specific capacitance increase from 386.4 to 1082.6 F g−1 at a high discharging current density of 6 A g−1. This work suggests that the as-prepared Co0.116Ni0.884(OH)2 composite electrode has a promising future as higher charging/discharging rate materials for pseudo-supercapacitors.