Carbon-coated Nickel Research Articles

Construction of carbon-coated nickel phosphide nanoparticle assembled submicrospheres with enhanced electrochemical properties for lithium/sodium-ion batteries

A hybrid based on nickel phosphide nanoparticle assembled submicrospheres coated with a glucose-derived carbon shell is synthesized from Ni-glycerate precursors through a carbon coating route and a subsequent calcination-phosphatization approach. Characterization results indicate that the synthesized submicrospheres have a diameter of ∼500 nm and are composed of nanoparticles as subunits with sizes ranging from 30 to 40 nm. Each sphere and its subunits are coated by a continuous carbon coating shell. The electrochemical performance of the material as an anode for reversible energy storage is investigated and evaluated. A comparative study of the lithium/sodium storage properties between the hybrid and pure nickel phosphide is carried out. The electrochemical results demonstrate that the hybrid fabricated electrode is a highly attractive anode for lithium- and sodium-ion batteries, exhibiting much better lithium/sodium storage properties compared to the nickel phosphide submicrospheres of the same construction. The reasons for the enhanced energy storage performance of the submicrospheres are explored by a series of comparison experiments based on morphology, structure, electrical conductivity, and kinetic property.

Rational design of integrated CuO@CoxNi1−x(OH)2 nanowire arrays on copper foam for high-rate and long-life supercapacitors

Rational electrode architectural design, favorable electrode composition, and versatile synthesis approach play a significant role in developing advanced electrodes for high-performance supercapacitor. In this work, we report a facile approach for fabricating 1D hierarchical CuO@CoxNi1−x(OH)2 nanowire arrays grown on 3D highly conductive copper foam. The optimized CuO@Co0.2Ni0.8(OH)2 electrode delivers an ultrahigh specific capacity of 374.7 mAh g−1 at 2 A g−1 with exceptional rate capability (301.7 mAh g−1 at 50 A g−1) and remarkable cycling stability (95.9% after 10 000 cycles at 50 A g−1). A flexible asymmetric solid-state supercapacitor (ASC) is fabricated using the optimized CuO@Co0.2Ni0.8(OH)2 as the positive electrode, activated carbon-coated nickel foam as the negative electrode, and polyvinyl alcohol/KOH gel as electrolyte. The flexible ASC operating with a potential window of 0–1.6 V delivers an energy density of 46.5 Wh kg−1 with a power density of 526.9 W kg−1. The ASC also exhibits excellent cycling stability with a capacity retention of 84.3% after 10 000 cycles at a current density of 7 A g−1.

Three-Dimensional Carbon-Coated Treelike Ni3S2 Superstructures on a Nickel Foam as Binder-Free Bifunctional Electrodes

Three-dimensional (3D) nanostructures are commonly endowed with numerous active sites, large specific surface area, and good mechanical strength, which make them as an efficient candidate for energy storage and conversion. Herein, by considering the advantages of 3D nanostructures, we successfully fabricated carbon-coated nickel sulfide on a nickel foam (C@NS@NF) with a unique 3D treelike superstructure via a two-step hydrothermal process. By virtue of its hierarchical superstructures, 3D treelike architecture, and carbon shell encapsulation, the as-fabricated carbon-coated Ni3S2 can be directly served as binder-free bifunctional electrodes for supercapacitor and hydrogen evolution reaction, where high specific areal capacitance (6.086 F cm-2 at 10 mA cm-2) for supercapacitors and low overpotential (92 mV at 10 mA cm-2) for the electrocatalyst have been demonstrated. These inspiring results of this material make it as a potential candidate for energy storage and conversion.

Structure and size dependence of the magnetic properties of Ni@C nanocomposites

Carbon-coated nickel (Ni) nanoparticles, Ni@C nanocomposites, have been synthesized using solid-state pyrolysis of nickel phthalocyanine and metal-free phthalocyanine (NiPc)x· (H2Pc)1−x solid solutions, 0⩽x⩽1. The Ni concentrations in carbon matrix (cNi) of the prepared samples continuously varied in the range of 0–3at.% (0–12wt.%). The average nanoparticle size varied within 4–40 nm range. All samples containing single domain Ni nanoparticles exhibit both ferromagnetic and superparamagnetic properties because of the wide range of size distribution. An abrupt drop of saturation magnetization has been observed with decrease in size of Ni nanoparticles from 40 nm to 12 nm. Nearly linear dependence of saturation magnetization on the nanoparticle surface/volume ratio can be interpreted as a result of contact interaction between Ni nanoparticles and the carbon matrix which provides an electron transfer from carbon matrix to nickel. However, further reductions in nanoparticle size increase magnetization growth of which can apparently contribute to the emergence of the giant paramagnetism due to large orbital moments of conductive electrons. The size effects and surface magnetic anisotropy in Ni@C nanocomposites are revealed in the measurements of coercive field, zero-field cooling (ZFC) susceptibility, blocking temperatures and ferromagnetic resonance spectra. Concentration dependencies of ferromagnetic and electron paramagnetic resonance parameters in Ni@C nanocomposites have also been investigated and their peculiarities highlighted. A correlation between concentration dependencies of FMR and SQUID magnetometry parameters, namely between the g-factor curves – geff, the resonance linewidth – ΔHFMR and coercive field – Hc, have been observed.

Carbon-Coated Nickel Nanoparticles: Effect on the Magnetic and Electric Properties of Composite Materials

Nickel nanoparticles coated with few layers of carbon have been embedded into the polydimethylsiloxane (PDMS) matrix in concentrations up to 11 vol %. Dielectric and magnetic properties of composite materials have been studied in wide frequency (20 Hz–1 MHz) and temperature (130–430 K) ranges. It was demonstrated that the temperature behavior of dielectric properties is determined by glass transitions in the PDSM matrix below 200 K and the Maxwell–Wagner relaxation above room temperature. The possibility of using fabricated composites on the basis of the PDMS matrix for producing a wide range of passive electromagnetic components, such as frequency-selective filters, wide-band detectors/sensors of a bolometric type, and even electromagnetic “black holes” is also discussed.

The design and performance of the nano-carbon based double layers flexible coating for tunable and high-efficiency microwave absorption

Nanocarbon-based materials are outstanding microwave absorbers with good dielectric properties. In this study, double-layer silicone resin flexible absorbing coatings, composed of carbon-coated nickel nanoparticles (Ni@C) and carbon nanotubes (CNTs), with low loading and a total thickness of 2 mm, were prepared. The reflection loss (RL) of the double-layer absorbing coatings has measured for frequencies between 2 and 18 GHz using the Arch reflecting testing method. The effects of the thickness and electromagnetic parameters of each layer and of the layer sequence on the absorbing properties were investigated. It is found that the measured bandwidth (RL ≤ − 10 dB) of the optimum double-layer structure in our experiment range achieves 3.70 GHz. The results indicated that the double coating structure composed of different materials has greater synergistic absorption effect on impedance matching than that of same materials with different loading. The maximum RL of S1 (5 wt% CNTs)/S3 (60 wt% Ni@C) double-layer absorbing coating composed of different materials (S1 and S3) was larger than the one achieved using either S1 or S3 alone with the same thickness. This was because double-layer coating provided a suitable matching layer and improve the interfacial impedance. It was also shown that absorbing peak value and frequency position can be adjusted by double-layer coating structure.

Controllable fabrication of Pt nanocatalyst supported on N-doped carbon containing nickel nanoparticles for ethanol oxidation

In this paper, platinum nanoparticles were deposited on a carbon carrier with the partly graphitized carbon and the highly dispersive carbon-coated nickel particles. An efficient electron transfer structure can be fabricated by controlling the contents of the deposited platinum. The high resolution transmission electron microscopy images of Pt2/Ni@CN-doped sample prove the electron transfer channel from Pt (1 1 1) crystal planes to graphite (1 0 0) or Ni (1 1 1) crystal planes due to these linked together crystal planes. The Pt3/Ni@CN-doped with low Pt contents cannot form the electron transfer structure and the Pt1/Ni@CN-doped with high Pt contents show an obvious aggregation of Pt nanoparticles. The electrochemical tests of all the catalysts show that the Pt2/Ni@CN-doped sample presents the highest catalytic activity, the strongest CO tolerance and the best catalytic stability. The high performance is attributed to the efficient electronic transport structure of the Pt2/Ni@CN-doped sample and the synergistic effect between Pt and Ni nanoparticles. This paper provides a promising method for enhancing the conductivity of electrode material.

Facile synthesis of N-doped carbon-coated nickel oxide nanoparticles embedded in N-doped carbon sheets for reversible lithium storage

In this work, we present a facile strategy for the synthesis of well-structured transition metal oxides based composites by the decomposition of nitrate and polyvinylpyrrolidone (PVP) followed by simple oxidation at a low temperature and using them as high performance materials for reversible lithium storage. As proofs of this simple strategy, three kinds of TMOs, namely NiO, Fe2O3 and Co3O4, based composites have been prepared with this simple strategy. The morphology and structure analyses indicate that TMOs nanoparticles with a size of 10 nm are tightly coated by the in situ formed graphene-like carbon shell and evenly dispersed in the microsized nitrogen-doped carbon sheets (C@TMOs@NCSs) derived from the PVP. As lithium storage materials, the as-prepared C@NiO@NCSs composites show excellent electrochemical performances in terms of cycle stability (651 mAh g−1 after 1500 cycles at 1 A g−1 and 518 mAh g−1 after 1400 cycles at 2 A g−1) and rate capability (400 mAh g−1 at 4 A g−1). Such superior electrochemical performance is attributed the well-structured composites with features of tight carbon coating layer, evenly dispersed TMOs nanoparticles and robust carbon supports.

Effects of Ni and carbon-coated Ni addition on the thermoelectric properties of 25Bi2Te3+75Sb2Te3 base composites

In this paper, we report the effect of nickel (Ni) and carbon coated nickel (C-Ni) on the thermoelectric and mechanical properties of 25Bi2Te3+75Sb2Te3 (GA) base composites. Ni and C-Ni powders were synthesized using pulse wire evaporation and mixed with 25Bi2Te3+75Sb2Te3 in a planetary ball mill. The morphology of the Ni and C-Ni powders and GA + x (x = none, Ni, or C-Ni) composites were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermoelectric properties of the GA + x (x = none, Ni, or C-Ni) composites shows that the addition of Ni increases the carrier concentration while the presence of C-Ni reduces the carrier concentration to a level comparable to the bare sample (x = 0). Subsequently, the Seebeck coefficient of the GA + C-Ni sample increases by about 18% more than in the bare sample. The thermal conductivity of the GA + Ni and GA + C-Ni samples was considerably lower at room temperature compared to the bare sample. The mechanical properties of the GA + Ni and GA + C-Ni composite samples show a three-fold improvement compared to the bare sample.

On polystyrene–block polyisoprene–block polystyrene filled with carbon-coated Ni nanoparticles

The manuscript focuses on the dispersion of magnetic nanoparticles within self-assembling block copolymers, on the preferential localization of nanoparticles and on the effect of their concentration on the magnetic properties of the nanocomposites and on the self-assembly features of the matrix. Carbon-coated nickel nanoparticles dispersed within polystyrene–block polyisoprene–block polystyrene have been investigated by Raman, X-ray, SQUID, differential scanning calorimetry, and electron microscopy. The effect of nanofiller on the self-assembly features of the block copolymer is reported. Preferential localization of nanofiller within the soft phase was noticed below 20 wt% nanofiller. Higher loadings with nanoparticles showed an uniform distribution of nanofiller within the block copolymer, consistent with the destruction of self-assembly. The effect of nanoparticles’ concentration on blocking temperature is discussed.

Carbon-Coated Nickel Phosphide Nanosheets as Efficient Dual-Electrocatalyst for Overall Water Splitting.

Low-cost and efficient electrocatalysts for overall water splitting are in high demand for a wide range of applications across renewable and clean energy. Here, we report a simple one-step synthesis of a three-dimensional (3D) carbon-coated Ni8P3 nanosheet array as bifunctional catalyst for both hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). The nanosheet array possesses low overpotentials, high current densities, and small Tafel slopes in both HER and OER and shows high electrocatalytic activities and long-term stability. The carbon layer with high electric conductivity serves not only as a protective layer to prevent Ni8P3 dissolution but also as an active layer to decrease the electrocatalysis overpotential. The nanosheet array has HER outstanding activity in both acid and alkaline media. Its superior performance in OER can be due to the synergistic interaction at the Ni8P3/NiOx heterojunction. Furthermore, cell voltage as low as 1.65 V can achieve 10 mA cm-2 current density for full water splitting in an alkaline water electrolyzer, indicating potential application of C@ Ni8P3 as bifunctional catalyst for clean and renewable energy utilization.

Theoretical calculation and experiment of microwave electromagnetic property of Ni(C) nanocapsules**Project supported by the Science and Technology Program of Guangdong Province, China (Grant Nos. 2014B010106005, 2013B051000077, and 2015A050502047) and the Science and Technology Program of Guangzhou City, China (Grant No. 201508030018).

With the combination of the dielectric loss of the carbon layer with the magnetic loss of the ferromagnetic metal core, carbon-coated nickel (Ni(C)) nanoparticles are expected to be the promising microwave absorbers. Microwave electromagnetic parameters and reflection loss in a frequency range of 2 GHz–18 GHz for paraffin-Ni(C) composites are investigated. The values of relative complex permittivity and permeability, the dielectric and magnetic loss tangent of paraffin-Ni(C) composites are measured, respectively, when the weight ratios of Ni(C) nanoparticles are equal to 10 wt%, 40 wt%, 50 wt%, 70 wt%, and 80 wt% in paraffin-Ni(C) composites. The results reveal that Ni(C) nanoparticles exhibit a peak of magnetic loss at about 13 GHz, suggesting that magnetic loss and a natural resonance could be found at that frequency. Based on the measured complex permittivity and permeability, the reflection losses of paraffin-Ni(C) composites with different weight ratios of Ni(C) nanoparticles and coating thickness values are simulated according to the transmission line theory. An excellent microwave absorption is obtained. To be proved by the experimental results, the reflection loss of composite with a coating thickness of 2 mm is measured by the Arch method. The results indicate that the maximum reflection loss reaches −26.73 dB at 12.7 GHz, and below −10 dB, the bandwidth is about 4 GHz. The fact that the measured absorption position is consistent with the calculated results suggests that a good electromagnetic match and a strong microwave absorption can be established in Ni(C) nanoparticles. The excellent Ni(C) microwave absorber is prepared by choosing an optimum layer number and the weight ratio of Ni(C) nanoparticles in paraffin-Ni(C) composites.

Metal organic framework derived magnetically separable 3-dimensional hierarchical Ni@C nanocomposites: Synthesis and adsorption properties

Design an effective absorbent that has high surface area, and perfect recyclable is imperative for pollution elimination. Herein, we report a facile two-step strategy to fabricate magnetically separable 3-dimensional (3D) hierarchical carbon-coated nickel (Ni@C) nanocomposites by calcinating nickel based metal organic framework (Ni3(OH)2(C8H4O4)2(H2O)4). SEM and TEM images illuminate that the nanocomposites were constructed by 8nm nickel nanoparticle encapsulated in 3D flake like carbon. The specific surface area of the obtained nanocomposites is up to 120.38m2g−1. Room temperature magnetic measurement indicates the nanocomposites show soft magnetism property, which endows the nanocomposites with an ideal fast magnetic separable property. The maximum adsorption capacity of the nanocomposites for rhodamine B is 84.5mgg−1. Furthermore, the nanocomposites also exhibit a high adsorption capacity for heavy metal ions. The adsorbent can be very easily separated from the solution by using a common magnet without exterior energy. The as-prepared Ni@C nanocomposites can apply in waste water treatment on a large-scale as a new adsorbent with high efficiency and excellent recyclability.

Template-directed synthesis of hierarchically mesporous superparamagnetic carbon-coated nickel nanoplates

This paper reports the preparation of carbon-coated nickel (Ni@C) nanoplates through an extension of stöber method and subsequent calcinating approach, in which Ni(OH)2 nanoplates were chosen as the templates. The obtained Ni@C nanoplates exhibit a uniform hexagonal core–shell structure with a size of 140nm and a thickness of 20nm shell. Ni@C nanoplates possess a high specific surface area and a hierarchical mesoporous structure (pores located in 3nm and 50nm). The magnetic hysteresis curve reveals that Ni@C nanoplates have a certain degree of magnetism with near-zero coercivities and low remanence, indicating superparamagnetic performance. Ni@C nanoplates own a promising potential for a magnetic catalyst.

Effects of particle size on the magnetic and microwave absorption properties of carbon-coated nickel nanocapsules

To study the effects of particle size on magnetic and microwave absorption properties, carbon-coated nickel (Ni/C) nanocapsules were prepared by an arc discharge method, where their particles size was adjusted by varying the arc current value from 40 to 100 A. The average particle size of the Ni/C nanocapsules increases from 25 to 53 nm while the thickness of carbon shells keeps independence with increasing the arc current value. The saturation magnetization and coercivity increase with increasing the particle size, due to the small size effect. The complex permittivity, dielectric loss and attenuation constant of paraffin-Ni/C composites are in inverse proportion to the particle size of Ni/C nanocapsules, ascribed to the larger interface area and more defects in the smaller nanocapsules. With the reduction of particle size of Ni/C nanocapsules, the peak of reflection loss (RL) at fixed absorber shifts to lower frequency and the bandwidth becomes broader, while the maximum RL of the composites can be achieved at thinner absorber layer. The phenomenon results from the bigger dielectric loss, larger attenuation constant and better impedance matching degree. The control of particle size is an effective way for adjusting the microwave absorption properties.

Magnetic Properties of Carbon-Coated Ni Nanoparticles Prepared by Solid-Phase Pyrolysis of Nickel-Phthalocyanine

Carbon-coated nickel nanoparticles with a mean diameter of 40nm were synthesized via solid-phase pyrolysis of nickel-phthalocyanine. The composition structure and morphology of samples were investigated by scanning and transmission electron microscopy, X-ray diffraction, Raman spectroscopy and energy-dispersive X-ray microanalysis. Magnetic characteristics of samples were measured with a vibrational magnetometer and a magnetic resonance spectrometer. The main mass of Ni ferromagnetic nanoparticles have a single-domain and a vortex (pseudo-single domain) structures. We also revealed superparamagnetic Ni nanoparticles (several percent) and carbon paramagnetic centers caused by defects in the carbon matrix. We determined the main magnetic characteristics of Ni nanoparticles, their temperature and field dependences as well as the parameters of ferromagnetic resonance spectra.

Efficient and Stable Carbon-coated Nickel Foam Cathodes for the Electro-Fenton Process

Carbon-coated nickel foam (C@NF) electrodes are prepared via a simple and effective method, hydrothermal-carbonization cycle coating process, characterized by scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) and employed as the electro-Fenton (E-Fenton) cathode for degrading dimethyl phthalate (DMP) in aqueous solution. For the sake of comparison, nickel foam (NF) electrode and the conventional E-Fenton cathode (graphite gas diffusion electrode (GDE)) are also tested and compared. Experimental results indicate that nickel leaching can be effectively controlled at C@NF4 cathode (4 times cycle coating process), having great significance for promoting the application of NF in E-Fenton system. Moreover, C@NF4 cathode still presents excellent and effective performance on DMP degradation. DMP can be completely degraded within 2h at −0.5V and the total organic carbon (TOC) removal reaches as high as 82.1 %, which is almost 3 times as high as that at graphite GDE. Futhermore, the current efficiency for H2O2 generation at C@NF4 is enhanced by 12 times compared to that at NF, and consequently the energy consumption during DMP degradation at C@NF4 is obvious lower than that at both NF cathode and graphite GDE. From the obtained results it can be deduced that C@NF4 is promising to be an attractive alternative E-Fenton cathode for removing organic pollutants in wastewater.

Direct growth of mesoporous carbon-coated Ni nanoparticles on carbon fibers for flexible supercapacitors

A solution method for direct growth of mesoporous carbon-coated nickel nanoparticles on carbon fibers is demonstrated for flexible supercapacitors.

Solvothermal Synthesis of Carbon-Coated Nickel Nanoparticles in Ionic Liquid

Carbon-coated nickel nanoparticles were synthesized by solvothermal method in 1-buty-3-methylimidazolium tetrafluoraborate ionic liquid. The obtained products are characterized by X-ray powder diffraction (XRD), Raman spectroscopy, infrared spectroscopy and transmission electron microscopy (TEM). The magnetic properties of carbon-coated nickel nanoparticles have been investigated by vibrating sample magnetometry (VSM). It was found that the carbon-coated nickel nanoparticles showed excellent magnetic properties. The present route may give researchers more choices for preparing other carbon-coated transition metal nanoparticles.

Phenylacetylene hydrogenation on Fe@C and Ni@C core–shell nanoparticles: About intrinsic activity of graphene-like carbon layer in H2 activation

Me@C nanocomposites were prepared by evaporation of overheated liquid drop of Me in the flow of inert gas containing a hydrocarbon. The resulting carbon-coated nickel and iron nanoparticles contain metal cores of about 5nm in size that are wrapped in a few layers of graphene-like carbon. Experimental data and theoretical results give evidence of the ability of carbon coating in nanocomposites Fe@C and Ni@C to H2 activation by dissociative adsorption due to the presence of space and structure defects and/or the presence of transition metal in subsurface layer. Since molecular hydrogen dissociation is the key step of hydrogenation reactions, both Ni@C and Fe@C provide high conversion of phenylacetylene (PA) (about 100%) during hydrogenation at the temperatures above 150 and 300°C, respectively. Fe@C provides excellent styrene (ST) selectivity: 86% at 99% PA conversion at 300°C. ST selectivity is moderate on Ni@C (about 60%) in the temperature range of 100–150°С and low at higher temperatures.