Structure Of Nickel Research Articles

Magnetic structure of oxygen-deficient perovskite nickelates with ordered vacancies

The authors identify the magnetic structure of oxygen-deficient nickelates with density functional theory calculations and explain how arrangements of structural oxygen vacancies stabilize an antiferromagnetic ground state.

FORMATION AND ELECTROCHEMICAL PROPERTIES OF NICKEL AND COBALT TRANSITION METALS OXIDE FILMS

Films of cobalt oxide and nickel oxide on monocrystalline silicon substrates were obtained by electrochemical deposition from aqueous electrolyte solutions. Their structure and composition were studied by Raman microscopy and scanning electron microscopy. The results of the study by Raman spectroscopy showed that the obtained films are polycrystalline structures of cobalt (II, III) oxide and nickel (II) oxide, the crystalline perfection of which increases with an increase in the electrolyte temperature. It was found by scanning electron microscopy that nickel oxide films have a smoother surface, while cobalt oxide has a more developed structure consisting of lamellar crystals. The specific electrochemical capacity of cobalt oxide and nickel oxide films obtained under optimal conditions, measured by voltammetry, was 14.67 and 1634.08 F/g, respectively. The high specific electrochemical capacity of a nickel oxide film can be used to create efficient electrochemical devices and energy storage devices.

Effects of graphene oxide and current density on structure and corrosion properties of nanocrystalline nickel coating fabricated by electrodeposition

Protective coatings with superior corrosion resistance and enhanced mechanical properties are still greatly required when applied in challenging environments. In this paper, nickel-graphene oxide nanocrystalline coatings with uniform structure have been fabricated by co-electrodeposition technique. Effects of graphene oxide (GO) in plating solution and applied current density on structural, composition, crystallite size and corrosion-resistant properties of electrodeposited Ni-GO nanocrystalline coatings were compared and investigated systematically. The deposited coatings have a compact, crack-free, silver-gray appearance with lower surface roughness, exhibiting colonies-like morphology. The presence and uniform distribution of graphene oxide on the surface as well as inside nickel coating were confirmed. The crystallite size and crystal plane orientation have no significant alteration in the presence of graphene oxide. The preferred orientation of (200) crystal plane of pure Ni is changed to low energy (111) plane for Ni-GO composites. The average roughness Ra of Ni-GO is 3–5 nm. Ni-GO coating contains 2.6–3.9 wt% GO, 95.5–96.9 wt% Ni and some oxygen. With the increase of GO, the corrosion resistance first enhanced to a maximum at 0.2 g L−1 GO. When GO exceeds a certain value, agglomeration occurred, causing uneven dispersion of GO and heterogeneous coarse surfaces. The anti-corrosion capability was enhanced by the incorporation of GO due to the grain refinement and the uniform dispersion of impermeable GO. Current density could change the structure and anti-corrosive features of Ni-GO coating. The Ni-GO nanocrystalline coating possesses enhanced performance, which has a promising application prospect in harsh environments.

Constructing nickel–iron oxyhydroxides integrated with iron oxides by microorganism corrosion for oxygen evolution

Developing facile approaches for preparing efficient electrocatalysts is of significance to promote sustainable energy technologies. Here, we report a facile iron-oxidizing bacteria corrosion approach to construct a composite electrocatalyst of nickel–iron oxyhydroxides combined with iron oxides. The obtained electrocatalyst shows improved electrocatalytic activity and stability for oxygen evolution, with an overpotential of ∼230 mV to afford the current density of 10 mA cm−2. The incorporation of iron oxides produced by iron-oxidizing bacteria corrosion optimizes the electronic structure of nickel–iron oxyhydroxide electrodes, which accounts for the decreased free energy of oxygenate generation and the improvement of OER activity. This work demonstrates a natural bacterial corrosion approach for the facile preparation of efficient electrodes for water oxidation, which may provide interesting insights in the multidisciplinary integration of innovative nanomaterials and emerging energy technologies.

Exploring the mechanism of the excellent catalytic activity of NiFe-layered double hydroxides in oxygen evolution reactions by modifying the iron content

Layered double hydroxides are very promising catalysts for water splitting, in particular NiFe-layered double hydroxide, which has attracted significant attention due to its excellent catalytic activity in oxygen evolution reactions using alkaline electrolytes. In this work, samples with different molar ratios of Ni to Fe are prepared by a typical hydrothermal method to study the effect of iron on the catalytic properties of NiFe-layered double hydroxide. All the NiFe-layered double hydroxides exhibit much better oxygen evolution reaction activity than NiOOH, while increasing the iron content slightly affects the activity, which implies that only Fe ions at some specific site contribute to the oxygen evolution reaction activity. The NiFe-layered double hydroxide with a 4:1 molar ratio of Ni to Fe shows the best oxygen evolution reaction catalytic performance, and requires only an overpotential of 176 mV to afford a current of 10 mA cm−2 in 1.0 M KOH, and exhibits a much lower Tafel slope (51 mV dec−1). This work also studies the effect of iron on the electronic structure of nickel and reveals the mechanism behind the excellent oxygen evolution reaction catalytic properties of NiFe-layered double hydroxide.

Electrochemical performance of asymmetric device using the nickel–zinc organometallic structure

AbstractBimetallic metal–organic frameworks (BMOFs) have developed as novel candidates for electrodes due to their high‐performance energy storage applications. We attempted to develop a new three‐dimensional (3D) ordered structure of nickel–zinc MOFs (NZMOF), grown in situ on carbon cloth (NZMOF/CC) using a solvo‐hydrothermal strategy to increase the stored energy. A notable capacitance of 456.8 F/g was achieved for this electrode at 1 A/g. In addition, the NZMOF/CC//AC/CC assembled split‐cell asymmetric supercapacitor device (SASD) achieved an excellent energy and power densities of 38.54 Wh/kg and 750 W/kg, respectively, with a capacity retention of 87.27% after 5000 cycles, which is better than that of conventional supercapacitors. Additionally, this study is easy and controllable, providing a viable approach for fabricating hybrid electrode materials for high‐performance energy storage systems.

Designing and Tuning the Electronic Structure of Nickel–Vanadium Layered Double Hydroxides for Highly Efficient Oxygen Evolution Electrocatalysis

Designing and Tuning the Electronic Structure of Nickel–Vanadium Layered Double Hydroxides for Highly Efficient Oxygen Evolution Electrocatalysis

Assessing the correlated electronic structure of lanthanum nickelates

The series of nickel-oxide compounds LaNiO3 (formal Ni(d 7)), La2NiO4 (formal Ni(d 8)) and LaNiO2 (formal Ni(d 9)) is investigated by first-principles many-body theory, using a combination of density functional theory, self-interaction correction and dynamical mean-field theory. The characteristics of these different nickelates, in good agreement with available experimental data, is revealed by employing a compound-independent choice for the local Coulomb interactions. The dichotomy within the low-energy dominant Ni-e g sector of kind is rising with growing Ni(3d) filling across the series. An intermediate-coupling scheme for spin-polarized calculations is introduced, which leads to very weak Ni ordered moments for the infinite-layer compound LaNiO2 in contrast to the robust-moment system La2NiO4.

Electronic structure of higher-order Ruddlesden-Popper nickelates

We analyze the electronic structure of the recently synthesized higher-order nickelate Ruddlesden-Popper phases ${\mathrm{La}}_{n+1}{\mathrm{Ni}}_{n}{\mathrm{O}}_{3n+1}$ $(n=4--6)$ using first-principles calculations. For all materials, our results show large holelike Fermi surfaces with ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ character that closely resemble those of optimally hole-doped cuprates. For higher values of $n$, extra non-cuprate-like bands of ${d}_{{z}^{2}}$ orbital character appear. These aspects highlight that this Ruddlesden-Popper series can provide a means to modify the electronic ground states of nickelates by tuning their dimensionality. With their similarities and differences to the cuprates, this new family of materials can potentially shed light on the physics of copper-based oxides.

DNA binding and cleavage, BRCA1 gene interaction, antiglycation and anticancer studies of transition metal complexes of sulfonamides.

A series of 4-((4-methylphenylsulfonamido)methyl)cyclohexanecarboxylic acid (NaMSCCA) transition metal complexes [Cu(II), Zn(II), Ni(II), Mn(II), and Co(II)] have been synthesized by precipitation method. The characterization was done by physical techniques, FT-IR spectroscopy, mass spectrometry, and NMR spectroscopy. The molecular structures of nickel (II) AZ-3 and cobalt (II) AZ-5 complexes were determined by the X-ray diffraction technique and found to crystallize in the triclinic space group P-1. The coordination geometry around the central nickel (AZ-3) and cobalt (AZ-5) atoms was square planar bipyramidal. Molecular docking was performed with duplex DNA of sequence d(CGCGAATTCGCG)2 DNA to determine the probable binding mode of compounds. Then these synthesized compounds were used to perform DNA cleavage activity through the agarose gel electrophoresis method. Among the compounds, compounds AZ-1 and AZ-2 exhibited good nuclease activity. The DNA sequence of breast-cancer suppressor gene 1 (BRCA1) was amplified through PCR and interaction studies of compounds AZ-1 and AZ-2 were performed through gel electrophoresis and fluorescence emission spectroscopy. The expression analysis of the BRCA1 gene was also performed to quantify the expression relative fold change (2^-(∆∆CT)) after treatment with compounds. All synthesized compounds were evaluated for their antioxidant and antiglycation activities and AZ-2 exhibited excellent results. The molecular docking study of these compounds was performed against the protein structure of advanced glycation end products to support the experimental results. Anticancer activity of compounds was performed through MTT assay. Copper and zinc complexes depicted the highest anticancer activity against human breast adenocarcinoma (MCF7) and human corneal epithelial cell (HCEC) cell lines.

Additive manufacturing of Ti-Ni bimetallic structures

Bimetallic structures of nickel (Ni) and commercially pure titanium (CP Ti) were manufactured in three different configurations via directed energy deposition (DED)-based metal additive manufacturing (AM). To understand whether the bulk properties of these three composites are dominated by phase formation at the interface, their directional dependence on mechanical properties was tested. X-ray diffraction (XRD) pattern confirmed the intermetallic NiTi phase formation at the interface. Microstructural gradient observed at the heat-affected zone (HAZ) areas. The longitudinal samples showed about 12% elongation, while the same was 36% for the transverse samples. During compressive deformation, strain hardening from dislocation accumulation was observed in the CP Ti and transverse samples, but longitudinal samples demonstrated failures similar to a brittle fracture at the interface. Transverse samples also showed shear band formation indicative of ductile failures. Our results demonstrate that AM can design innovative bimetallic structures with unique directional mechanical properties.

Inside Back Cover: Atomic Bridging Structure of Nickel–Nitrogen–Carbon for Highly Efficient Electrocatalytic Reduction of CO2 (Angew. Chem. Int. Ed. 6/2022)

An atomic bridging structure of nickel–nitrogen–carbon active sites confined in porous carbon was revealed by Jintao Zhang and co-workers in their Research Article (e202113918). Uncovering the fundamental mechanism reveals a high potential for modulating bridging structures to enhance interfacial electrocatalytic reactions beyond carbon dioxide reduction.

Innenrücktitelbild: Atomic Bridging Structure of Nickel–Nitrogen–Carbon for Highly Efficient Electrocatalytic Reduction of CO2 (Angew. Chem. 6/2022)

Eine Brückenstruktur aus Nickel-Stickstoff-Kohlenstoff in porösem Kohlenstoff wurde von Jintao Zhang und Mitarbeitern in ihrem Forschungsartikel aufgedeckt (e202113918). Die Identifizierung des grundlegenden Mechanismus birgt ein hohes Potenzial für die Modulation von Brückenstrukturen für die elektrokatalytische CO2-Reduktion und andere Grenzflächenreaktionen.

Constructing Amorphous/Amorphous Heterojunction Structure in Nickel Borate/Boride Hybrid Nanosheets for Efficient Electrocatalytic Methanol Oxidation

Constructing Amorphous/Amorphous Heterojunction Structure in Nickel Borate/Boride Hybrid Nanosheets for Efficient Electrocatalytic Methanol Oxidation

Observation of the Formation Process of Fatigue Dislocation Structure in Micro-sized Ni Single Crystal

The purpose of this study is to diretly observe the formation process of characteristic fatigue dislocation structure in micro-sized nickel (Ni) single crystal specimens with a single slip orientation. Dog-bone shaped specimens with a cross-sectional area of 2 μm×2 μm were prepared by means of a focused ion beam processing system. Although tension-compression cyclic tests under a constant stress amplitude were performed on them, they were interrupted after different cycles (N = 1, 100, 1000 and 3500) and the inside was observed by a UHV-TEM after thinning. In the early stage of the test (N = 1 and 100), dislocations were rapidly multiplied. After N = 1000 where intrusions/extrusions appeared on the specimen surface, the dislocations gathered at the local areas. Then dislocation walls like those observed in a ladder-like structure in PSB was formed after N = 3500 cycle. This implies that vein, which is the important dislocation structure in fatigued bulk material, cannot be formed in micro-sized metals due to the tiny dimension.

Ni nanocatalysts supported on MIL-53(Al) for DCPD hydrogenation.

Metal organic frameworks (MOFs) with many unique advantages have drawn wide attention in the field of catalysis. However, the poor structural stability of MOFs limits its application. Heat treatment for MOFs can enhance its electrical conductivity and structural stability, which helps to improve the catalytic performance. Ni nanoparticles supported on MIL-53(Al) were synthesized through different heat treatment temperature. Catalysts with uniform distribution of active nickel and rich mesoporous structure were obtained by adjusting the heat treatment temperature to 500 °C. The results show this catalyst has the best hydrogenation activity and stability. Under the reaction conditions of 60 °C and 2 h, the conversion rate of DCPD is 100%, and the selectivity of endo-THDCPD is higher than 95%. After five cycles, the catalyst also show excellent stability and high activity, the conversion rate of DCPD is still 100%.

Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitrates.

The formation of different nickel and cobalt layered hydroxide phases by a variety of solution and solid-state synthesis methods has been investigated. Initially, preparative methods were refined to generate single-phase products from metal(II) nitrate hexahydrate starting materials which were then characterised by powder X-ray diffraction, vibrational spectroscopy and thermogravimetric analysis. As well as the brucite type β-M(OH)2 and the hydrotalcite-like [M(OH)2-x(H2O)x]x+ alpha-phases (where M = Ni, Co), two different hydroxynitrate phases were isolated with the generic formula M(OH)2-x(NO3)x with x = 0.67 and 1.0 (where M = Ni, Co). The reduction of symmetry of the nitrate anion from D3h to C2v allows the alpha-phases to be distinguished from the two different layered hydroxynitrate phases by both infrared and Raman spectroscopy through the loss of symmetry and concomitant splitting of the degenerate bands. The symmetric N-O stretch enables the two hydroxynitrate phases to be distinguished from one another through the sharp absorption bands at ca. 1000 cm-1 (x = 0.67) and ca. 1050 cm-1 (x = 1.0). The thermogravimetric analysis data of the phases showed key differences between the layered hydroxides, with anhydrous phases having singular weight losses over short temperature ranges and hydrated phases having multiple losses over more extended temperature ranges.

Solution combustion synthesis of Ni-based hybrid metal oxides for oxygen evolution reaction in alkaline medium.

Oxygen evolution reaction (OER) has arisen as an outstanding technology for energy generation, conversion, and storage. Herein, we investigated the synthesis of nickel-based hybrid metal oxides (NixM1−xOy) and their catalytic performance towards OER. NixM1−xOy catalysts were synthesized by solution combustion synthesis (SCS) using the metal nitrates as oxidizer and glycine as fuel. Scanning electron microscope (SEM) micrographs display a porous morphology for the hybrid binary NixM1−xOy, the common feature of combusted materials. X-ray diffraction (XRD) of NixM1−xOy depicted well-defined diffraction peaks, which confirms the crystalline nature of synthesized catalysts. The particle size of as-synthesized materials ranges between 20 and 30 nm with a mesoporous nature as revealed by N2-physisorption. The electrocatalytic performance of the as-prepared materials was evaluated towards OER in alkaline medium. Among them, NixCo1−xOy showed the best catalytic performance. For instance, it exhibited the lowest overpotential at a current density of 10 mA cm−2 (404 mV), onset potential (1.605 V), and Tafel slope (52.7 mV dec−1). The enhanced electrocatalytic performance of NixCo1−xOy was attributed to the synergism between cobalt and nickel and the alteration of the electronic structure of nickel. Also, NixCo1−xOy afforded the highest Ni3+/Ni2+ when compared to other electrocatalysts. This leads to higher oxidation states of Ni species, which promote and improve the electrocatalytic activity.

Molecular Structure of Nickel Octamethylporphyrin-Rare Experimental Evidence of a Ruffling Effect in Gas Phase.

The structure of a free nickel (II) octamethylporphyrin (NiOMP) molecule was determined for the first time through a combined gas-phase electron diffraction (GED) and mass spectrometry (MS) experiment, as well as through quantum chemical (QC) calculations. Density functional theory (DFT) calculations do not provide an unambiguous answer about the planarity or non-planar distortion of the NiOMP skeleton. The GED refinement in such cases is non-trivial. Several approaches to the inverse problem solution were used. The obtained results allow us to argue that the ruffling effect is manifested in the NiOMP molecule. The minimal critical distance between the central atom of the metal and nitrogen atoms of the coordination cavity that provokes ruffling distortion in metal porphyrins is about 1.96 Å.

Atomic Bridging Structure of Nickel-Nitrogen-Carbon for Highly Efficient Electrocatalytic Reduction of CO2.

To meet strategic applications, electrochemical reduction of CO2 into value-added chemical molecules would be improved by the rational design of advanced electrocatalysts with atomically dispersed active sites. Herein an electrospun-pyrolysis cooperative strategy is presented to not only modulate the porous structure of the carbon support for favorable charge and mass transfer, but also adjust the bridging structure of atomically dispersed metal species. Typically, the experimental results and theoretical calculations revealed that the unique chemical structure of binuclear nickel bridging with nitrogen and carbon atoms (namely Ni2 -N4 -C2 ) tunes the electronic nature of the d-states for the optimal adsorption of carbon dioxide and intermediates, thus inducing the substantial enhancement of CO2 reduction via the thermodynamically more favorable pathway. The identification of such a structure demonstrates the large space to modulate the atomic bridging status for optimizing electrocatalysis.