Ni-Co Alloy Research Articles

Size and Synergy Effects of Ultrafine 2.6 nm CoNi Nanoparticles Within 3D Crisscross N‐Doped Porous Carbon Nanosheets for Efficient Water Splitting

AbstractA non‐precious metal‐based catalyst for water electrolysis provides great promise for cost‐effective and highly efficient sustainable hydrogen production. It herein rationally synthesizes uniform superminiature CoNi nanoparticles (2.6 nm) embedded in 3D N‐doped randomly oriented and erected porous carbon nanosheets (CoNi@N‐PCNS). Taking advantage of the large specific surface area, expedited intermediate transport, and effectively exposed active sites of the hierarchical architecture, located CoNi nanoparticles yield a high atom utilization efficiency. Density functional theory calculations indicate that synergetic and cooperative interactions inside CoNi alloy modulate the d‐band center, leading to a moderate adsorption and desorption energy of reaction intermediates, further accelerating both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. Accordingly, the as‐synthesized CoNi@N‐PCNS catalyst establishes superb catalytic activities for HER and OER, revealing overpotentials of 71.2 and 263.8 mV at 10 mA cm−2, respectively. Remarkably, when assembled as a two‐electrode electrolyzer, a satisfying cell voltage of 1.59 V at 10 mA cm−2, and superior stability are demonstrated, highlighting great promise toward water electrolysis.

Engineering of nickel, cobalt oxides and nickel/cobalt binary oxides by electrodeposition and application as binder free electrodes in supercapacitors

Cobalt oxide, nickel oxide and cobalt/nickel binary oxides were synthesised by electrodeposition. To fine tune composition of CoNi alloys, growth parameters including voltage, electrolyte pH/concentration and deposition time were varied. These produced nanomaterials were used as binder free electrodes in supercapacitor cells and tested using three electrode setup in 2 MKOH aqueous electrolyte. Cyclic voltammetry and galvanostatic charge/discharge were used at different scan rates (5–100 mV/s) and current densities (1–10 A/g) respectively to investigate the capacitive behaviour and measure the capacitance of active material. Electrochemical impedance spectroscopy was used to analyse the resistive/conductive behaviours of these electrodes in frequency range of 100 kHz to 0.01 Hz at applied voltage of 10 mV. Binary oxide electrode displayed superior electrochemical performance with the specific capacitance of 176 F/g at current density of 1 A/g. This hybrid electrode also displayed capacitance retention of over 83% after 5000 charge/discharge cycles. Cell displayed low solution resistance of 0.35 Ω along with good conductivity. The proposed facile approach to synthesise binder free blended metal electrodes can result in enhanced redox activity of pseudocapacitive materials. Consequently, fine tuning of these materials by controlling the cobalt and nickel contents can assist in broadening their applications in electrochemical energy storage in general and in supercapacitors in particular.

The Effect of Al and Ti Additions on Solid Solution Strengthening and Precipitation Hardening in CoNiFe Medium-Entropy Alloys.

The effect of Al and Ti additions on the microstructure and properties of CoNiFe alloys was studied in this paper. The investigations were conducted on four specially designed and produced arc furnace alloys (from 3 to 5 components, with medium to high entropy). Samples in various states were analyzed, i.e., as-cast, after homogenization, after solution heat treatment, and after solution heat treatment and aging. The obtained samples were characterized by: SEM observations, EDS, XRD, TEM analyses, and finally, hardness measurements. The solid solution strengthening coming from the addition of 5 at. pct. Al was negligible, while the effect from the 5 at. pct. of Ti addition was significant. The precipitation hardening effect related to the presence of the (CoNi)3Ti phase caused by the Ti addition is comparable with the total effect of the Al and Ti addition, which caused the precipitation of (NiCo)3AlTi.

CoNi Alloy Nanoparticles Confined in N-Doped Porous Carbon as an Efficient and Versatile Catalyst for Reductive Amination of Levulinic Acid/Esters to N-Substituted Pyrrolidones

CoNi Alloy Nanoparticles Confined in N-Doped Porous Carbon as an Efficient and Versatile Catalyst for Reductive Amination of Levulinic Acid/Esters to <i>N</i>-Substituted Pyrrolidones

Binary CoNi and Ternary FeCoNi Alloy Thin Films as High-Performance and Stable Electrocatalysts for Oxygen Evolution Reaction

Binary CoNi and Ternary FeCoNi Alloy Thin Films as High-Performance and Stable Electrocatalysts for Oxygen Evolution Reaction

Improving the Sulfurophobicity of the NiS-Doping CoS Electrocatalyst Boosts the Low-Energy-Consumption Sulfide Oxidation Reaction Process.

Producing sulfur from a sulfide oxidation reaction (SOR)-based technique using sulfide aqueous solution has attracted considerable attention due to its ecofriendliness. This study demonstrates that NiS-doped cobalt sulfide NiS-CoS-supported NiCo alloy foam can deliver the SOR with superior electrocatalytic activity and robust stability compared to reported non-noble metal-based catalysts. Only 0.34 V vs RHE is required to drive a current density of 100 mA cm-2 for the SOR. According to the experiment, the catalyst exhibits a unique sulfurophobicity feature because of the weak interaction between sulfur and the transition metal sulfide (low affinity for elemental sulfur), preventing electrode corrosion during the SOR process. More impressively, the chain-growth mechanism of the SOR from short- to long-chain polysulfides was revealed by combining electrochemical and spectroscopic in situ methods, such as in situ ultraviolet-visible and Raman. It is also demonstrated that electrons can transfer straight from the sulfion (S2-) to the active site on the anode surface during the low-energy-consumption SOR process. This work provides new insight into simultaneous energy-saving hydrogen production and high-value-added S recovery from sulfide-containing wastewater.

Preparation and characterization of Ni-Co-TiN/CeO2 composite coating by jet electrodeposition for improved mechanical and anti-corrosion properties

The Ni-Co alloy was coated with Ni-Co-TiN/CeO2 by Jet electrodeposition to enhance the properties of Nickel-Cobalt (Ni-Co) alloy. The morphologies, texture orientation, microhardness, coating adhesion, wear resistance, and corrosion resistance of Ni-Co-TiN/CeO2 composite coatings were characterized. The influences of concentration of mixed particles (micron-TiN and nano- CeO2) on microstructural, surface properties, mechanical properties and anti-corrosion performance of the composite coatings were studied. The addition of nano-mixed particles changed the morphology of Ni-Co-TiN/CeO2 composite coating from large cellular protrusion structures to fine granular structures, the mechanical properties and anti-corrosion performance of Ni-Co-TiN/CeO2 composite coatings were improved. The composite coating exhibited superior microhardness, bonding force, wear resistance and anti-corrosion performance, when the concentration of mixed particles was 4 g l−1. This work contributed to the development of a variety of micro- and nanoparticle phase-enhanced metal-based composite coatings.

Electrodeposition of Ni-Co Alloys from Ionic Liquids and Their Electrocatalytic Properties

Amorphous and nanocrystalline Ni-Co alloys have been deposited on FTO glass in ethylammonium nitrate (EAN), a protic ionic liquid (PIL). In a first step, the physicochemical properties of EAN with Ni2+ and Co2+ salts have been studied as well as the electrochemical behavior of these metal cations in the PIL in order to optimize the electroplating process (Fig. 1). It was shown that when the electrodeposition of Co, Ni and Ni-Co alloys was performed on FTO glass in EAN at 60 ℃ in an oxygen-free environment, nanocrystalline Ni-Co alloys with different atomic ratios were obtained, depending on both the deposition potential and the ion concentration in solution.The electrocatalytic properties of these materials were then investigated towards the hydrogen evolution reaction (HER). It was shown that the addition of Co in Ni-based alloys can promote the HER, and most notably, amorphous Ni-Co alloys show lower overpotential or reaction rate. This work provides a new route to prepare nanocrystalline and amorphous Ni-Co alloys with different ratio in PIL for practical applications in electrocatalysis such as water splitting. Figure 1

Elemental Fe conditioning for the synthesis of highly selective and stable high entropy catalysts for CO2 methanation

High entropy oxides (HEOs) with high stability and designability have demonstrated excellent catalytic performance in CO2 hydrogenation. However, it is challenging to combine high methane selectivity and high stability of HEOs using an equimolar design strategy. In this study, a non-equimolar design strategy was used to fix the Cr, Co, Mn and Ni elements and adjust different Fe molar amounts to prepare a highly crystalline HEO at 900 °C. After H2 reduction, the catalyst (HEO-4-900/H2) achieved 72.9% CO2 conversion and 98.8% methane selectivity at atmospheric pressure and 400 °C, and maintained a high methane selectivity of over 97% after 100 h stability test. The catalytic activity was influenced by the amount of Fe. Increasing the amount of Fe could precisely regulate the crystallinity and oxygen defects of the crystal, improve the catalyst stability, reduce the interaction between the Co-Ni alloys and HEOs, and allow the catalyst to contain more Co-Ni active sites and more abundant oxygen vacancies. This study demonstrates the considerable potential of HEOs for CO2 methanation, and provides a new design idea for further stimulating highly active CO2 methanation HEOs catalysts.

Lignite-char-supported highly dispersed ultrasmall Ni-Co alloy for stably dry reforming of methane at low temperature

Lignite, abundant in oxygen-containing functional groups, can disperse metal ions through an ion-exchanging method to prepare highly dispersed metal catalysts. Herein, we prepared the Ni-Co bimetallic catalysts using this method and tested their activity and stability in the dry reforming of methane reaction. The Ni0.05-Co0.1 with Ni/Co mass ratio of 1:10 exhibited superior performance due to its higher specific surface area (386 m2/g), smaller metallic particle size (4.85 nm), better dispersion and moderate basicity (0.023 mmol/g), showing the best activity at 650 °C, 2400 mL.h−1.g−1 and atmospheric pressure, with a conversion of 71.5% for CH4, 82.8% for CO2, and a molar ratio of H2/CO of 0.73. Additionally, the catalyst maintained a stable activity throughout a continuous 30 h test at 650 °C, 7200 mL.h−1.g−1 and 0.3 MPa. Overall, this study demonstrates that lignite-char-supported Ni-Co alloy catalysts show great potential for DRM reaction particularly at relatively low temperature and elevated pressure.

Ni-Co alloy catalyst derived from NixCoy/MgAl2O4 via exsolution method for high coke resistance toward dry reforming of methane

The dry reforming methane (DRM) reaction, which directly utilizes the two major greenhouse gases as reactants and produces syngas (a mixture of H2 and CO), is a promising method to achieve carbon neutrality. In this study, we developed a series of Ni–Co alloy catalysts with varying ratios using the exsolution method and explored the optimal Ni/Co ratio for DRM. By incorporating Co as a secondary metal and precisely controlling its proportion, the catalysts exhibited improved activation balance in CH4 and CO2, excellent resistance to coking, and the efficiency of the reaction pathway. Notably, the Ni4Co1 catalyst exhibited excellent coke resistance with the lowest coking rate of 0.2 μgcoke·gcat−1h−1, which was only 0.34% of the monometallic Ni catalyst. The origin of coke resistance of catalysts was investigated through in-situ DRIFT and found that the appropriate ratio of Co leads to the formate-intermediate dominant pathway that is more favorable for anti-coking. Furthermore, the catalysts exhibited reversible exsolution properties, as confirmed by cyclic of calcination–reduction. The findings of this study offer valuable insights into the fabrication of high-performance DRM catalysts utilizing the exsolution-driven alloying technique.

Carbon nanotube modified hierarchical NiCo/porous nanocomposites with enhanced electromagnetic wave absorption

The rational modulating of the microstructure in magnetic carbon-based composites is crucial to optimize the electromagnetic wave (EMW) absorption performance. It is challenging for EMW absorbers to simultaneously achieve optimal minimum reflection loss (RLmin) and a broadband effective absorption bandwidth (EAB). In this paper, carbon nanotubes (CNTs)-modified NiCo/CNTs nanosheets were effectively prepared as a new EMW absorption material utilizing NiCo-containing metal-organic framework (MOF) as a sacrificial precursor. As expected, NiCo/CNTs-650 demonstrated both a broadband EAB of 7.04 GHz and the RLmin of − 58.14 dB at 15.9 GHz with a thickness of 2.0 mm. Furthermore, NiCo/CNTs-650 is capable of achieving 30.2 dB m2 RSC (radar cross section) reduction under an incident angle of 7° via CST, while NiCo/CNTs-70015 % achieved a reduction of 39.47 dB m2 at 0 °. These performances outperformed that other CNTs-decorated MOF-derived hierarchical composites previously described. NiCo/CNTs-650 combines the synergistic effects of magnetic loss provided by zero-dimensional (0D) NiCo alloy, dielectric attenuation realized by one-dimensional (1D) CNTs, and optimized impedance matching through two-dimensional (2D) nanosheets with abundant hierarchical interfaces. These studies provide a specialized route for the manufacture of mixed-dimensional hierarchical EMW absorbents with high performance.

Dimensional Engineering of Hierarchical Nanopagodas for Customizing Cross‐Scale Magnetic Coupling Networks to Enhance Electromagnetic Wave Absorption

AbstractDimensional engineering of appropriate structure is an effective approach to achieve high‐performance electromagnetic (EM) wave absorption for magnetic materials. However, controllable modulation of the material configuration and a comprehensive understanding of the relationship between structure and loss mechanism remain challenging. Herein, magnetic CoNi pentagonal nanopagodas (PNPs) are ingeniously tailored using a competition orientation strategy, in which high‐density PNPs with sharp corners/edges and hierarchical structure are rooted in situ on the surface of CoNi alloy microsphere. This unique configuration of PNPs originates from the orientation growth of CoNi fivefold twins, which can be effectively regulated by manipulating metal ratio and evolves into flake‐, serrated thorn‐, prismoid‐, and blocks‐like morphologies. Optimized CoNi microspheres with high‐density PNPs exhibit a broad absorption bandwidth of 6.82 GHz at only 1.8 mm thickness. Cross‐scale magnetic coupling networks strengthen magnetic loss ability, magnetocrystalline defects induce dielectric polarization enhancement, which are intuitively confirmed by Lorentz off‐axis electron holography and geometric phase analysis. The underlying mechanism of enhanced magnetic interaction in sharp structure is clearly deciphered by micromagnetic simulation. This study provides methodological guidance for dimensional engineering in fabricating hierarchical magnetic structure and significant insights into the morphology‐dependent loss mechanism for magnetic EM absorption materials.

Highly efficient and selective hydrodeoxygenation of guaiacol to cyclohexanol over a rod-like CoNi-C catalyst

Selective hydrodeoxygenation (HDO) of guaiacol is a green and sustainable method to produce cyclohexanol. However, developing an economically efficient and highly selective non-precious metal catalyst for the HDO reaction remains a significant challenge. Here, we synthesized rod-like CoNi alloy catalysts via calcination a precursor of CoNi-BTC metal–organic framework (MOF). And a selectivity up to 94.9% can be achieved for cyclohexanol under mild reaction conditions. According to the analysis of characterization, the specific surface area and pore size had a dual impact on the catalyst activity calcinated at different temperatures. The synergistic effect of the CoNi alloy also led to an enhanced hydrogen adsorption capability of the catalyst, resulting in a significant enhancement in catalytic activity compared to the monometallic catalyst. This article provides a reference for the rational design of alloy MOF materials for catalyzing high-performance HDO of guaiacol.

Functionally constructed magnetic-dielectric mineral microspheres for efficient thermal energy storage and microwave absorption

Electromagnetic interference (EMI) and equipment heat dissipation problems are becoming increasingly prominent in advanced applications such as modern wireless communications, driverless cars, and portable devices. Multifunctional composites with efficient energy storage, conversion, and microwave absorption are urgently needed. We reported an effective strategy to construct attapulgite (ATP), carbon nanotubes (CNT), and NiCo alloys composite mineral microspheres (ACNC). Urchin-like TiO2 was coated on the surface of ACNC to form composite microspheres (ACNCT), which was compounded with paraffin (P-ACNCT) to prepare thermal energy storage and microwave absorption integrated material. The urchin-like TiO2 morphology possesses unique advantages in encapsulating paraffin. The results show that the melting and solidification enthalpy of the P-ACNCT reaches 111.6 J/g and 108.1 J/g, respectively, which indicates excellent thermal energy storage capacity. Combining a dielectric TiO2 shell with a magnetic composite microsphere core can produce a core–shell microsphere mechanism that allows for adjustable reflection loss and promotes impedance matching. The effective microwave absorption bandwidth of P-ACNCT can reach 5.76 GHz when the thickness is only 1.6 mm in the 2–18 GHz range. P-ACNCT is significant for synchronous microwave absorption and thermal energy regulation of advanced electronic equipment.

Effects of Bromide Ions in Anomalous Codeposition of Ni-Co Alloys with a Sulfamate Based Electrolyte

Alloy electrodeposition of Ni-Co alloys is known to show an anomalous codeposition behavior, which the concentration of cobalt in the deposited alloy is higher than the concentration of cobalt ions in the electrolyte. In this study, the cobalt content in the alloy is increased from 30 at% to 60 at% through introduction of bromide ions into a sulfamate bath, while addition of chloride ions does not give any significant influences to the alloy. The bromide ions are found to promote the reduction of cobalt ions but inhibit the reduction of nickel ions. Effects of the pH are also investigated to provide possible explanation to the phenomenon observed, and the anomalous codeposition behavior becomes more obvious in a more acidic electrolyte.

Influence of temperature on the electrochemical formation of a Ni-Co alloy under an applied external magnetic field

Influence of temperature on the electrochemical formation of a Ni-Co alloy under an applied external magnetic field

Binary NiCo nanoalloys and single-atoms implanted nitrogen-doped carbon nanotubes as highly efficient, robust electrocatalyst for overall water splitting

Finding robust, high-efficiency, noble-metal-free electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) particularly at a low overpotential is a crucial endeavor for water electrolyzer-based green H2 harvesting, but challenges remain. Fortunately, atomically dispersed metal catalysts hold great potential for OER and HER owing to the exclusive electronic structure and maximized atom utilization, however, the insufficient population of reactive sites and unfortunate electrical conductivity seriously limit their performance. Herein, we rationally designed and synthesized a single-atom catalyst consisting of atomic Co and Ni with NiCo alloys encapsulated nitrogen-doped carbon nanotubes (N-CNTs). The NiCo-N-CNTs catalyst annealed at 900 °C (NiCo-N-CNTs-900) displays ultralow overpotential of 210 mV and 54 mV at 10 mA/cm2 for OER and HER, respectively, which are attributed to the robust synergistic effects of Ni/Co single atoms and NiCo nanoalloys. Furthermore, NiCo-N-CNTs-900 electrode exhibits higher mass activity of 2188 A/gNiCo and 468.75 A/gNiCo and turnover frequency of 0.679 O2 s−1 and 0.285 H2 s−1 for OER and HER, respectively, which is much better than those of commercial RuO2 and Pt/C catalysts. We further employed the NiCo-N-CNTs-900 as both anode and cathode catalyst for constructing a two-electrode electrolyzer, generating a current density of 10 mA/cm2 at a low cell voltage of 1.483 V, surpassing the benchmark Pt/C//RuO2 pair. This work not only provides a robust and effective non-precious metal catalyst but also a facile, efficient method to fabricate atomically dispersed metal atoms integrated with alloys for clean hydrogen production and beyond.

Effects of deposition current density, time and scanning velocity on scanning jet electrodeposition of Ni-Co alloy coating

Jet electrodeposition has superior application prospects in the preparation of nanostructured alloy coatings, which is suitable for high current density deposition and has selective deposition characteristics. The purpose of this work is to clarify the combined effect of multiple factors on the properties of alloy coatings prepared by jet electrodeposition. The L16 made by Taguchi orthogonal array was used in the experiment. The work studied the influence of process parameters such as deposition time (t), current density (i) and scanning velocity (v) on the properties of NiCo alloy coatings prepared on 304 stainless steel, which was set as the substrates. Material deposition rate (MDR), coating microhardness and coating surface roughness (SRa) were selected as the test indicators to characterize the coating properties. Analysis of Variance (ANOVA) was done to analyze the experimental data. The results indicated that current density had the greatest effect on MDR, coating microhardness and coating surface roughness, followed by deposition time and scanning velocity. The optimal parameters combination was selected, listed as follows: deposition time 20 min, current density 70 A·dm−2 and the scanning velocity 10 mm·s−1. The coating microhardness was 532.40 HV, coating SRa was as low as 85 nm, adhesion between coating and substrate was as high as 26.12 N and self-corrosion current density was 5.718 × 10−3 μA·cm−2 under the optimal parameters combination, which showed good performance. This processing method can guide the preparation of NiCo alloy coatings by jet electrodeposition, while the good performance exhibited by the coating can provide a reference for the anti-corrosion and wear-resistant treatment of marine equipment and textile machinery.

High-loading magnetic nanocrystals well-dispersed onto carbon nanosheet honeycombs as ultralight and broadband microwave absorbers

Homogenously and densely dispersing small-sized magnetic particles into hierarchically porous carbon matrices is essential yet challenging for high-performance carbon-based microwave absorbers with balanced impedance matching and strong attenuation ability. Herein, we propose a general and scalable strategy by direct pyrolysis of solid polyvinylpyrrolidone (PVP) dissolved with metal (i.e., Fe, Co, and Ni) nitrates to prepare carbonaceous-magnetic hybrid absorbers. Benefiting from coordination interactions of carbonyl group-rich PVP molecules toward metal ions and the thermal foaming effect of PVP, the optimized CoNi-based composite material possesses a honeycomb-like architecture built by ultrathin (<2 nm) carbon nanosheets embedded with a high-loading (>50 wt%) of ultrafine CoNi alloy nanocrystals (an average size of ∼20 nm). Such structural characteristics endow the absorber with an ultralow tap density of 87.0 mg cm−3 and excellent microwave absorption performance with a superior reflection loss of −51.4 dB at a thickness of 2.6 mm and an effective absorption bandwidth of 7.2 GHz (10.5−17.7 GHz). Moreover, this synthesis methodology is universally applicable and can easily be extended to prepare carbon honeycomb composite absorbers decorated with other magnetic nanocrystals.