Recent advances in metal oxide/hydroxide on three-dimensional nickel foam substrate for high performance pseudocapacitive electrodes

The high demand for long-lasting and portable energy storage devices with enhanced energy and power densities has attracted researcher's interest globally. The three-dimensional (3D) nickel foam is a promising electrode material for storing energy in various devices because they possess large surface area, are very conductive and enjoy a continuous permeable 3D system. This article provides a review and detailed information on the uses of 3D nickel foam-based electrodes with metal oxides/hydroxides of different morphologies for high-performance pseudocapacitors. We assess the limitations and future prospects of 3D nickel foam-based electrodes with metal oxides/hydroxides for industrial application towards enhancing pseudocapacitors' energy storage capability.     

DNA-templated nickel nanostructures and protein assemblies

We report a straightforward method for the fabrication of DNA-templated nickel nanostructures on surfaces. These nickel nanomaterials have potential to be applied as nanowires, as templated catalyst lines, as nanoscale magnetic domains, or in directed protein localization. Indeed, we show here that histidine-tagged phosducin-like protein (His-PhLP) binds with high selectivity to both Ni2+-treated surface DNA and DNA-templated nickel metal to create linear protein assemblies on surfaces. The association of His-PhLP with DNA-templated nickel ions or metal is reversible under appropriate rinsing conditions. Nanoscale DNA-templated protein assemblies might be useful in the construction of high-density protein lines for proteomic analysis, for example. Importantly, these nanofabrication procedures are not limited to linear DNA and can be applied readily to other self-assembled DNA topologies.     

On the encapsulation of nickel clusters by molecular nitrogen

The structures and energetic effects of molecular nitrogen adsorbates on nickel clusters are investigated using an extended Huckel model coupled with two models of the adsorbate-nickel interaction. The potential parameters for the adsorbates are chosen to mimic experimental information about the binding strength of nitrogen on both cluster and bulk surface phases of nickel. The first model potential is a simple Lennard-Jones interaction that leads to binding sites in holes defined by sets of near-neighbor nickel atoms. The second model potential has a simple three-body form that forces the model nitrogen adsorbates to bind directly to single nickel atoms. Significant rearrangement of the core nickel structures are found in both models. A disconnectivity graph analysis of the potential energy surfaces implies that the rearrangements arise from low transition state barriers and the small differences between available isomers in the nickel core.     

Partial oxidation of methane to syngas catalyzed by a nickel nanowire catalyst

A nickel nanowire catalyst was prepared by a hard template method,and characterized by transmission electron microscopy (TEM),N2 physical adsorption,X-ray photoelectron spectrometry (XPS),X-ray diffraction (XRD) and H2 temperature-programmed reduction (H2-TPR).The catalytic properties of the nanowire catalyst in the partial oxidation of methane to syngas were compared with a metallic Ni catalyst which was prepared with nickel sponge.The characterization results showed that the nickel nanowire catalyst had high specific surface area and there was more NiO phase in the nickel nanowire catalyst than in the metallic Ni catalyst.The reaction results showed that the nickel nanowire catalyst had high CH4 conversion and selectivities for H2 and CO under low space velocity.     

Electrochemical fluorination using porous nickel and foam nickel anodes

This work set out to examine the reasons behind some of the problems associated with ECF, namely, lack of reproducibility, low chemical yields, poor selectivity and low current densities, with a view to ameliorating these shortcomings and making the process more attractive to the chemical industry.The approach was to study the chemistry under controlled conditions of potential, reactant concentration, temperature, etc., and to analyse the results in terms of product structure, distribution and yield.Two distinct stages in the process were identified, i) the conditioning of the electrode, and, ii) the fluorination of the organic substrate.These stages are described in detail in relation to two model systems investigated, the fluorination of propene using porous and foam nickel anodes, and the fluorination of the octanoyl chloride using nickel foam anodes. The scales of experiments ranged from 100ml to 100 1 cell capacities.General conclusions are derived and recommendations made for the more efficient operation of the process.     

Studying the process of ionization of hydrogen in conditions of its forced delivery to a porous nickel oxide electrode

The hydrogen ionization process is studied experimentally on an industrial sintered nickel oxide electrode in models of sealed nickel-metal hydride batteries. It is shown that the hydrogen ionization rates that are reached during overcharge by high current densities in conditions of forced gas delivery into the electrode pores (up to 40 mA cm^?2) exceed the self-discharge rate of a nickel-hydrogen battery by two orders of magnitude. Up to 70% of hydrogen delivered into the compact assembly block undergoes ionization during forced charge of models of sealed nickel-metal hydride batteries with a closed hydrogen cycle. Two independent methods (potentiostatic and manometric) are used to determine the relationship between rates of hydrogen ionization with the degree of the electrode filling with gas and perform estimation of the process intensity at a unit reaction surface. It is established that, in conditions of forced gas delivery, practically all the hydrogen oxidation current is generated at the surface of the nickel oxide electrode beneath thin films of an electrolyte solution at the rate of 4–5 mA cm^?2. It is shown that the hydrogen oxidation rate on a nickel oxide electrode filled in part by gas is independent of the electrode potential, probably because of a tangible contribution made by diffusion limitations to the overall hampering of the process.     

A novel titanium-supported nickel electrocatalyst for cyclohexanol oxidation in alkaline solutions

A novel titanium-supported nickel electrode (Ni/Ti) is fabricated by a simple hydrothermal process using hydrazine hydrate as a reduction agent. Its electrocatalytic activity towards cyclohexanol oxidation has been investigated by cyclic voltammetry (CV), chronoamperometry (CA), quasi-steady state polarization and electrochemical impedance spectroscopy (EIS). Effects of various parameters such as potential scan rate and cyclohexanol concentration on the electro-oxidation of cyclohexanol are investigated. Results show that the Ni/Ti electrode behaves as an efficient catalyst for the electro-oxidation of cyclohexanol in basic media and its electrocatalytic activity towards cyclohexanol oxidation is higher than a nickel oxyhydroxide modified nickel electrode (NOMN). It is confirmed that during the anodic potential sweep the electro-oxidation of cyclohexanol follows the formation of NiOOH on the electrode surface and is then catalysed by NiOOH. The rate-determining step for cyclohexanol oxidation is the reaction between the high oxidation state nickel (Ni³⁺) and the adsorbed cyclohexanol on the surface of the Ni/Ti.     

Determination of corrosion current density on bulk nickel and nickel powder by the rate of cathodic depolarizer consumption

The method of “compensating additives” is used to determine the corrosion current of nickel and nickel powder in 0.5 M NaCl solution containing 0.01 M HCl. Comparing the corrosion currents measured on bulk nickel and nickel powder, the specific electrochemically active surface area of nickel powder is estimated.     

Nickel based electrocatalysts for oxygen evolution in high current density, alkaline water electrolysers

A number of nickel based materials are investigated as potential oxygen evolution catalysts under conditions close to those met in modern, high current density alkaline water electrolysers. Microelectrodes are used to avoid distortion of voltammetric data by IR drop even at the high current densities employed in such water electrolysers. High surface area nickel metal oxides prepared by cathodic deposition and mixed oxides prepared by thermal methods are considered. A mixed Ni/Fe oxide is the preferred electrocatalyst. The influence of hydroxide ion concentration and temperature on the voltammetry is defined. Preliminary stability tests in a zero gap cell with an OH(-) conducting membrane show no significant increase in overpotential during 10 days operation in 4 M NaOH electrolyte at a current density of 1 A cm(-2) at 333 K.     

Kinetics of nickel electroplating from methanesulfonate electrolyte

The overpotential of nickel ion electroreduction on the nickel and mercury electrodes is shown to increase in the following sequence of anions: ClO₄⁻,CH₃SO₃⁻, SO₄²⁻. On the nickel electrode, the overpotential of nickel evolution decreases as the pH^v increases from 1.5 to 4. This is associated with the increase in pH^s as the result of a parallel reaction of hydrogen evolution. It is shown that in contrast to mercury, the Tafel plots of the nickel electrode demonstrate a bend corresponding to the change in their slope from −0.044 to −0.132 V. This is accompanied by the lowering down of the reaction order in nickel ions from 2 to 1. A mechanism of nickel ion electroreduction that includes two parallel routes is proposed and substantiated by a model. In the low overpotential range, the predominant process is the electroreduction of nickel hydroxocomplexes, which is characterized by the strong dependence of the reaction rate on the potential and the concentration of electroactive species. For high overpotentials, the predominant process is the direct discharge of nickel aquacomplexes the rate of which depends weaker on the potential and the concentration of electroactive species.     

Surface modification of spherical nickel hydroxide for nickel electrodes

Electroless cobalt plating on spherical nickel hydroxide is tested in order to improve the conductivity of Ni(OH)₂ and the capacity of the electrode. The factors affecting the process of electroless cobalt plating are cobalt solution, temperature and pH, etc. The effects have been examined and the optimum process parameters have been obtained. The nickel hydroxide electrode which is made by nickel hydroxide deposited cobalt has excellent performance, the results showing that electroless cobalt plating on the surface of spherical nickel hydroxide particles is an effective method for modifying electrodes.     

Study of nickel nanoparticles supported on activated carbon prepared by aqueous hydrazine reduction

Nickel nanoparticles were obtained by the reduction in hydrazine aqueous media of nickel acetate as a precursor supported on activated carbon of high surface area. Classical catalysts using nickel acetate or nitrate were prepared for comparison. The catalysts were characterized by N(2) physisorption, H(2)-TPR, H(2)-adsorption, TPD, TEM, and XRD, and tested in the gas phase hydrogenation of benzene. Hydrazine catalysts were found much more active in benzene hydrogenation than corresponding classically prepared catalysts. Remarkably, their reactivity is comparable (turn-over frequency of 0.2001-0.2539 s(-1) at 393 K) to that of Pt classical catalysts supported on activated carbon in the same conditions. Evidence is given for the existence of the hydrogen spillover effect in benzene hydrogenation, not reported before in the literature. As a result of the hydrogen spillover effect, catalysts performances can be explained by a combination of surface metal atom reactivity, metal-support interaction strength, and specific surface area extent. Maximum effect is observed with hydrazine preparation method, for 1% Ni content and nickel acetate as a precursor. Unexpectedly, it was also found that hydrazine preparation increases the specific area of the catalysts.     

Nanoscale skeletal nickel catalysts prepared via ‘bottom up’ method

NiAl nanoparticles are of considerable importance because of interest in examining the effects of size, surface area, and composition on their physical and catalytic properties. Recently, a new method for the ‘bottom up’ wet chemical preparation of nickel aluminides has been reported. The ability to leach the aluminum from this system provides an entrance to the preparation of skeletal‐type metal catalysts similar to those produced in Raney‐type systems. Furthermore, it is believed that these nanoparticulate catalysts should provide high surface areas and high activities, while the presence of aluminum within the bulk of these catalysts provides additional stability. Here, we present the results of studies conducted on this system which compare their properties and behavior with traditional bulk Raney nickel systems. Additionally, we show that we are able to alter the properties of these nanoparticles by changing the stoichiometric ratio of nickel and aluminum. The properties of all systems have been analyzed through the use of nitrogen adsorption, X‐ray diffraction, and elemental analysis. Finally, the catalysts generated have been compared for their activity in the hydrogenation of butyronitrile. Copyright © 2002 John Wiley & Sons, Ltd.     

Novel in situ fabrication of chestnut-like carbon nanotube spheres from polypropylene and nickel formate

A novel in situ approach to mass fabrication of carbon nanotubes was reported. Composites of polypropylene (PP)/organomontmorillonite (OMMT)/nickel formate (NF) were prepared by mixing these components in a Brabender mixer at an elevated temperature. Chestnut-like carbon nanotube (CNT) spheres were in situ fabricated in high yields by heating the PP/OMMT/NF composites at 900 degrees C without adding any additional pre-synthesized nickel nanocatalysts. The products were studied by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and N2 adsorption-desorption measurements. The results showed that nickel nanoparticles were in situ produced, which catalyzed the formation of multiwalled carbon nanotubes (MWNTs) in an autoclave-like microreactor formed by OMMT. These in situ formed nickel nanoparticles were found to be more catalytically active than pre-synthesized nickel nanocatalysts, resulting in higher yields of CNTs. The obtained CNT spheres have a high surface area, which makes them a good catalyst support. Loading of metal nanoparticles was preliminarily tried, and Pt nanoparticles of ca. 2.65 nm in size were successfully deposited on CNTs. The applications of these nanocatalysts in chemical reactions are currently being studied in our laboratory.     

Electrodialysis performance when recycling dilute nickel solutions directly into a plating bath

This work was performed to determine membrane performance characteristics when using low current electrodialysis to recover and recycle nickel (salts) from dilute waste waters. Results showed that nickel at typical plating rinse concentrations (3000 p.p.m.) can be transferred electrically across commercially available membranes, and directly into a concentrated Watt's nickel plating bath (72,000 p.p.m.). Recovery at approximately 90% current efficiency was possible at current densities as low as 3.0 mA/cm². Nickel and co-transported water were routinely recycled as a relatively concentrated solution which would not cause dilution, since it was well above plating bath strength at all but the lowest current densities.     

Nanoparticles of nickel oxide and nickel hydroxide using lyophilisomes of fibrinogen as template

Stable lyophilisomes of fibrinogen at pH 7.5 have been prepared by the method of a rapid freezing–heating and annealing sequence. Reduction of the lyophilisomes of the nickel–fibrinogen complex coated on solid substrates and subsequent heating showed formation of nickel hydroxide and finally nickel oxide. Ultraviolet–visible spectroscopy has been used to monitor the thin films of pure fibrinogen microcapsules, as well as the subsequent nucleation and growth of nanoparticles within the supramolecular structure. Transmission electron microscopy showed initially a thread-like structure which disappeared on continued heating, resulting in nanoparticles ranging from 10 to 50 nm. Particle-size distribution of product was analyzed by using X-ray diffraction (XRD), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED), and Brunauer–Emmett–Teller (BET) N₂ adsorption. The results suggest that the NiO particles have a body-centered cubic structure and are well dispersed. The particle-size distribution ranges from 10 to 50 nm with an average particle size about 28 nm, and the specific surface area is 34 m²/g. Magnetic study carried out on the prepared nanoparticles showed a ferromagnetic behavior.     

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on NiO electrodes was studied by means of the galvanostatic transient method, mainly for oxalic acid. The oxalate or hydrogen oxalate anion or both were concluded to adsorb on the electrode. The adsorption was maximal at a potential less positive than the flat-band potential of the electrode, owing to preferential adsorption of hydroxyl anion in the region above the maximum adsorption potential. The quantity of adsorption was dependent on carrier concentration of the electrode, and high for the electrode of high carrier concentration. This phenomenon is connected to the charged condition of the electrode that when the maximum adsorption takes place, positively charged sites remain on the surface of the electrode which is charged negatively as a whole and the amount of the sites is much more different between the electrodes of different N than their bulk carrier concentrations. Adsorptions of malonic and succinic acid were distinctly low compared with that of oxalic acid. The adsorbability was in the order; oxalic acid>malonic acid>succinic acid. This order was in accord with the stability constants of nickel dicarboxylic acid chelates.     

Dual bimodal polyethylene prepared by intercalated silicate with nickel diimine complex

The ethylene polymerization was catalyzed by the intercalated montmorillonite with the nickel complex, [ArN?C(Me)? C(Me)?NAr]NiBr₂ (Ar = 2,6‐C₆H₃ (i‐Pr)₂). Polymer with low melting point and high molecular weight was produced at the early stage of polymerization followed by formation of polymer with high melting point and low molecular weight. It is proposed that the gallery of silicate lowers the propagation rate of polymerization and frequency of “chain walking” process of nickel complex anchored inside the gallery, which produces polymer with low molecular weight and low branching, whereas the nickel complex immobilized on the surface of silicate generates polymer with high molecular weight and high branching. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5506–5511, 2005     

CO2 reforming of methane over nickel catalysts supported on nanocrystalline MgAl2O4 with high surface area

In this paper dry reforming of methane (DRM) was carried out over nanocrystalline MgAl2O4-supported Ni catalysts with various Ni loadings. Nanocrystalline MgAl2O4 spinel with high specific surface area was synthesized by a co-precipitation method with the addition of pluronic P123 triblock copolymer as surfactant, and employed as catalyst support. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption, H2 chemisorption, temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), temperature- programmed desorption (TPD) and transmission and scanning electron microscopies (TEM, SEM) techniques. The obtained results showed that the catalyst support has a nanocrystalline structure (crystal size: about 5 nm) with a high specific surface area (175 m2 g-1) and a mesoporous structure. Increasing in nickel content decreased the specific surface area and nickel dispersion. The prepared catalysts showed high catalytic activity and stability during the reaction. SEM analysis revealed that whisker type carbon deposited over the spent catalysts and increasing in nickel loading increased the amount of deposited carbon. The nickel catalyst with 7 wt% of nickel showed the highest catalytic activity.     

Turkish perlite supported nickel oxide as the heterogeneous acid catalyst for a series of Claisen–Schmidt condensation reactions

Potentially active and eco-friendly solid acid catalysts have been synthesized by loading different weight percentages (10, 15, and 50) of nickel oxide on thermally activated Turkish perlite through the deposition-precipitation method. Structural features of prepared catalysts were analyzed using BET surface area analysis, X-ray diffraction, scanning electron microscope (SEM), SEM-EDX, transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), pyridine adsorbed FT-IR, UV-Vis diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. Pyridine adsorbed FT-IR analysis confirmed the presence of the optimum amount of Bronsted acidic sites in a catalyst having 15 wt. % loading of nickel oxide, which was tested for catalyzing a series of Claisen–Schmidt condensation of cyclohexanone and aromatic aldehydes to produce good isolated yield (90%–93%) of 2,6-bis(substituted benzylidene)cyclohexanones, significantly used in anti-tumor and cytotoxic activities. The high catalytic efficiency of the chosen catalyst remains almost intact up to six reaction cycles. On higher wt. % loading of nickel oxide, crystallite size increases along with agglomeration of larger nickel oxide particles on catalyst surface resulting in pore blockage and poor catalytic activity. Loading of NiO on the surface of thermally activated Turkish perlite was confirmed by SEM-EDX analysis, and TEM observations show that the particle size of the preferred catalyst was less than 50 nm. Based on results drawn from XRD, FT-IR, pyridine adsorbed FT-IR, UV-Vis DRS studies, model structures were proposed for Turkish perlite and all prepared catalysts. During this work, the catalytic potential of the preferred catalyst was compared with other previously reported catalysts, and it showed appreciable results. The formed products were further confirmed by their melting point and ¹H-NMR analysis.