Ni Core Research Articles

Zinc Vaporization Induced Formation of Desired Ni Nanoparticles Coated with Ultrathin Carbon Shells for Efficient Electrocatalytic H2 Production Coupling with Methanol Upgrading.

The integration of the hydrogen evolution reaction (HER) with the methanol oxidation reaction (MOR) has been demonstrated to be a viable strategy for the energy-saving generation of H2 and value-added formate, which relies primarily on highly active and cost-effective bifunctional electrocatalysts. Herein, an efficient electrocatalyst consisting of controllable Ni nanoparticles (NPs) coated with ultrathin graphitic carbon shells was obtained by the pyrolysis of a Ni-Zn metal-organic framework. Intriguingly, we found that zinc vaporization not only resulted in the relatively small Ni NPs but also ultrathin carbon shells (≤3 layers). The density functional theory simulations confirmed that these ultrathin carbon shells significantly influenced electrocatalytic activity by facilitating electron transfer from the Ni core to the carbon shell. The optimized Ni1(Zn)@C demonstrated high catalytic activity for both HER and MOR, and only a low potential of 97 mV at 10 mA cm-2 was required for HER and 1.48 V at 30 mA cm-2 for MOR. In a two-electrode electrocatalytic cell measurement, a cell voltage of 1.63 V was observed at 10 mA cm-2 in the presence of methanol, 240 mV lower than that without methanol.

Elemental Distribution and Melting Characteristics of FeNi nanoparticles on W(110) surfaces

In this report we describe new findings on the structure, composition and thermal stability of FexNi1−x nanoparticles, synthesized via a magnetron sputtering source and deposited on a clean W(110) surface. The elemental distribution of the nanoparticles was determined by energy dispersive X-ray (EDX) and electron energy loss spectroscopy (EELS). The melting behavior of the nanoparticles was studied under UHV by scanning tunneling microscopy (STM) upon heating. Notably, it has been observed that the nanoparticle’s core is characterized by an enrichment of Ni atoms, while the shell shows a higher amount of Fe atoms. Specifically, in the case of Fe0.75Ni0.25 and Fe0.25Ni0.75, where a Ni core is surrounded by a Fe shell, all nanoparticles completely liquefy after heating at 540 K. In contrast, the Fe0.50Ni0.50 nanoparticles, which exhibit a homogeneous distribution of both elements, only begin to melt around 540 K.

High coke resistance Ni-based CH4/CO2 reforming catalysts with strong spatial confinement effect: Effect of CeO2 shell thickness

Ni-based catalysts show promise as candidates for the dry reforming of methane (DRM), yet the susceptibility to sintering and carbon deposition is a major obstacle to industrialization. This work demonstrates a mesoporous Ni-based catalyst with a thickness-tailorable CeO2 shell for enhanced spatial confinement effect for the DRM. The Ni-MCM-41@xCeO2 catalysts are prepared at various CeO2 shell thickness through a two-step hydrothermal reaction. The kinetic studies have shown that the Ni-MCM-41@2CeO2 catalyst has the lowest activation energy, producing a high conversion of CH4 and CO2 as high as around 80 % at 700 °C. Our characterizations reveal that the Ni core is tightly confined in the mesoporous skeleton of MCM-41 and within a CeO2 shell. The Ni-MCM-41@2CeO2 catalyst is able to sustain high activity for more than 10 h of operation, with a remarkably reduced carbon deposition (0.28 %) as compared with a conventional Ni-Ce/MCM-41 catalyst (8.77 %). Furthermore, the density functional theory (DFT) calculation supports that the CeO2 shell layer significantly reduces dissociation potential barrier for CH4 and CO2, hence enhancing the catalytic activity of the DRM.

MFe2O4 (M: Cu, Ni)/SnS2magnetic Core-Shell Heterostructure for Photocatalytic H2 Generation and Environmental Remediation

Overgrowing demand for sustainable energy sources and environmental remediation has driven extensive research in the field of photocatalysis. This study presents a hydrothermal synthesis of a novel MFe2O4 (M: Cu, Ni)/SnS2 magnetic core-shell heterostructure. The engineered heterostructure combines the unique properties of MFe2O4 (M: Cu, Ni) magnetic crystal as a core with SnS2 nanosheets as a shell, aiming to exploit type-2 heterojunction properties to improve effects for improved photocatalytic performance. The structural chemistry, phase formation, and crystal orientation of the prepared material are investigated using various analytical techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman, and FTIR Spectroscopy. FE-SEM analysis reveals a well-defined core-shell morphology with intimate interfaces between MFe2O4 (M: Cu, Ni) crystals and SnS2 nanosheets. Photocatalytic efficiency is assessed through the industrial dye degradation process. The influence of the heterostructure's structural features on the photocatalytic activity is explored through density function theory, emphasizing the role of the core-shell interface and the magnetic properties of MFe2O4 (M: Cu, Ni) cores. The chemistry between the magnetic core and the shell in the heterostructure is demonstrated to be crucial for optimizing charge carrier dynamics and promoting surface reactions. Photocatalytic H2 generation under artificial simulated sunlight irradiation in the presence of MFe2O4 (M: Cu, Ni)/SnS2 core-shell heterostructure is demonstrated. This study not only presents a novel MFe2O4 (M: Cu, Ni)/SnS2 heterostructure for photocatalytic H2 generation but also provides valuable insights into the intricate relationship between structural chemistry and photocatalytic efficiency. The engineered heterostructure shows promising potential for applications in sustainable energy production and environmental remediation, contributing to the ongoing efforts towards a cleaner and more sustainable future.

Dynamical investigation of NinAgm (n + m = 147, 309, 561) nanoalloys with core–shell orderings

ABSTRACT The structures and dynamical properties of core–shell bimetallic Ni-Ag nanoalloys varying with different sizes and compositions have been studied using Monte Carlo (MC) and Molecular Dynamic (MD) simulations. We have considered the compositions in which the size of the core increases while the total number of atoms is fixed. In this sense, two (Ni13Ag134, Ni55Ag92), three (Ni13Ag296, Ni55Ag254, Ni147Ag162) and four (Ni13Ag548, Ni55Ag506, Ni147Ag414 and Ni309Ag252) compositions were considered for 147, 309 and 561 atoms, respectively. Highly symmetric Mackay icosahedral structures with centred symmetric cores appear for these specific sizes and compositions. Also, smaller Ni atoms tend to occupy the core and Ag atoms prefer to segregate to the surface of the nanoalloy due to its lower surface and cohesive energy. Then, the lowest energy structures obtained by Basin Hopping MC simulations were used as initial configurations for melting simulations. The transitions between different chemical ordering patterns with increasing temperature are possible in these systems while they are still in the solid state. Although there are clear differences in the melting process of the compositions with increasing size of the core, for all cases, surface melting occurs indicating that the Ag shell melts before the inner Ni core.

Selective Electrochemical CO2 Reduction tuned by N Configuration on graphitic Shells of Nickel Particles

AbstractDespite of high conductivity and reducing ability, transition metal nanoparticles tend to aggregate and unavoidably impact the selectivity during the proton‐coupled reduction process of CO2RR. New strategy to regulate and utilize the electronic property of transition‐metal particles allows for effective tuning of eCO2RR activity. Through simple creation of N‐doped carbon shells surrounding Ni nanoparticles and controlling the amount and arrangement of the N atoms, successful and long‐lasting electrochemical reduction of CO2 was accomplished. The inherent HER activity was almost completely suppressed. It exhibited FECO above 90 % in a 500 mV potential window, with the optimal up to 96.5 % at −0.78 V vs RHE. In flow cell electrolysis, a current density of 289.4 mA/cm2 was achieved with Faradic efficiency of 96.4 % towards CO. The results of control experiments using different catalysts imply that electron transfer between Ni core and shells was significantly influenced by the property of N atoms. High content of graphitic nitrogen is crucial for the catalytic performance.

FeO4-Type Active Sites Grown on Fe-Doped Ni Core Surfaces during the Initial Oxygen Evolution Reactions: Fe-Doping Effect?

FeO₄-Type Active Sites Grown on Fe-Doped Ni Core Surfaces during the Initial Oxygen Evolution Reactions: Fe-Doping Effect?

An interpretation for the components of 2p 3/2 core level x-ray photoelectron spectra of the cations in some inverse spinel oxides

In an effort to reconcile the various interpretations for the cation components of the 2p 3/2 observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p 3/2 core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p 3/2 core levels of NiFe2O4 thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles Ni x Co1−x Fe2O4 (x = 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe2O4 thin film. Surface-to-bulk core level shifts are also observed in CoFe2O4 and NiCo2O4 thin films but not as significantly as in NiFe2O4 thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.

Practical operating flexibility of a bifunctional freestanding membrane for efficient anion exchange membrane water electrolysis across all current ranges

AbstractThis study explores a symmetric configuration approach in anion exchange membrane (AEM) water electrolysis, focusing on overcoming adaptability challenges in dynamic conditions. Here, a rapid and mild synthesis technique for fabricating fibrous membrane‐type catalyst electrodes is developed. Our method leverages the contrasting oxidation states between the sulfur‐doped NiFe(OH)2 shell and the metallic Ni core, as revealed by electron energy loss spectroscopy. Theoretical evaluations confirm that the S–NiFe(OH)2 active sites optimize free energy for alkaline water electrolysis intermediates. This technique bypasses traditional energy‐intensive processes, achieving superior bifunctional activity beyond current benchmarks. The symmetric AEM water electrolyzer demonstrates a current density of 2 A cm−2 at 1.78 V at 60°C in 1 M KOH electrolyte and also sustains ampere‐scale water electrolysis below 2.0 V for 140 h even in ambient conditions. These results highlight the system's operational flexibility and structural stability, marking a significant advancement in AEM water electrolysis technology.

Self-supporting honeycomb coaxial carbon fibers: A new strategy to achieve an efficient hydrogen evolution reaction both in base and acid media

The electrocatalytic reaction mainly occurs on the surface of the electrocatalyst, while the active substances inside the electrocatalyst do not participate in the catalytic reaction. Therefore, core layer electrocatalysts with coaxial structures face lower utilization rates and a significant decrease in the number of exposed active sites, which in turn affects the electrocatalytic activity. Here, a novel one-dimensional (1D) honeycomb coaxial carbon nanofibers with MoC shell and Ni core layer (denoted as [Ni/C]@[MoC/C]-PCNFs) have been successfully prepared by pyrolysis of coaxial precursors fibers of [Ni(acac)2/PAN/PS]@[MoO2(acac)2/PAN]. The core layer of [Ni/C]@[MoC/C]-PCNFs) has a multi-channel honeycomb-like structure due to the pyrolysis of PS. The specific surface area of [Ni/C]@[MoC/C]-PCNFs (143.1 m2g−1) is more than twice that of the coaxial fibers with solid core structures (denoted as [Ni/C]@[MoC/C]-CNFs, 60.2 m2g−1). Simultaneously, the heterostructure formed between MoC and Ni, allowing for the adjustment of the electronic structure, acceleration of electron transfer and optimization of the electrocatalytic HER performance. The optimized self-supporting [Ni/C]@[MoC/C]-PCNFs exhibit the best catalytic activity for HER in both alkaline and acidic solutions, requiring only 84 and 160 mV to drive a current density of 10 mA cm−2. In addition, [Ni/C]@[MoC/C]-PCNFs catalyst exhibits good stability in both acidic and alkaline electrolytes. This core layer multi-channel coaxial structure designing provides an effective strategy for improving the electrocatalytic performance of catalysts.

In-situ preparation of Ni@ZrO2 nanocapsules powder by DC arc plasma for internal electrode of MLCC

Zirconium oxide-coated Ni nanocapsules (Ni@ZrO2 NCs) were in-situ fabricated by DC arc plasma in a nitrogen atmosphere. The co-evaporation of a target mixture consisting of coarse ZrO2 and Ni powders resulted in the formation of Ni@ZrO2 core-shell nanocomposites (NCs). The high energy states of excited ions (Ni3+, Zr4+, O2−, N2+, etc.) within the arc plasma region were recorded in real time by online optical emission spectroscopy (OES), which becomes visible evidences of the energy conditions for the fabrication of Ni@ZrO2 NCs. These nanocapsules underwent preferential formation of zirconium oxide species based on the oxygen potential rule, followed by the nucleation and subsequent growth processes. The Ni@ZrO2 NCs exhibited improved oxidation resistance, with an onset temperature for sintering approximately 40 °C higher than that of pristine Ni nanoparticles (NPs). Additionally, these NCs displayed an appropriate shrinkage rate, with a volume change of about 7.1% at 1200 °C. The symbiotic relationship between the ZrO2 shell and the Ni core within each nanoparticle suggests enhanced interfacial stability, rendering these NCs a promising material for the advancement of multi-layer ceramic capacitors (MLCCs).

Core‐shell Ni/NiO heterostructures as catalytic cathodes enabling high‐performance zinc bromine flow batteries

AbstractZinc bromine flow batteries (ZBFBs) are well suited for stationary energy storage due to their attractive features of high energy density and low cost. Nevertheless, the ZBFBs suffer from low power density and limited efficiency owing to the relatively severe polarization of the Br2/Br− redox couple. Herein, a three‐dimensional (3D) hierarchical composite electrode based on core‐shell Ni/NiO heterostructures anchored on graphite felt (Ni/NiO@GF) is designed to promote the kinetics of the Br2/Br− couple, so as to improve the power density and efficiency of the ZBFB. In this design, the highly conductive carbon felt and Ni cores provide a composite electrode with a 3D electron transporting framework to guarantee excellent electronic conductivity, while the NiO shells possess great absorption ability to Br2 and brilliant catalytic activity for the Br2/Br− redox reaction to reduce the electrochemical polarization. As a result, an enhanced ZBFB with Ni/NiO@GF electrode shows an outstanding energy efficiency of 86% at 20 mA cm−2 and can be operated at a current density of up to 160 mA cm−2 with a respectable energy efficiency of 67%. These results exhibit a promising strategy to fabricate catalytic electrodes for high‐performance ZBFBs.

Solar light driven atomic and electronic transformations in a plasmonic Ni@NiO/NiCO3 photocatalyst revealed by ambient pressure X-ray photoelectron spectroscopy.

This work employs ambient pressure X-ray photoelectron spectroscopy (APXPS) to delve into the atomic and electronic transformations of a core-shell Ni@NiO/NiCO3 photocatalyst - a model system for visible light active plasmonic photocatalysts used in water splitting for hydrogen production. This catalyst exhibits reversible structural and electronic changes in response to water vapor and solar simulator light. In this study, APXPS spectra were obtained under a 1 millibar water vapor pressure, employing a solar simulator with an AM 1.5 filter to measure spectral data under visible light illumination. The in situ APXPS spectra indicate that the metallic Ni core absorbs the light, exciting plasmons, and creates hot electrons that are subsequently utilized through hot electron injection in the hydrogen evolution reaction (HER) by NiCO3. Additionally, the data show that NiO undergoes reversible oxidation to NiOOH in the presence of water vapor and light. The present work also investigates the contribution of carbonate and its involvement in the photocatalytic reaction mechanism, shedding light on this seldom-explored aspect of photocatalysis. The APXPS results highlight the photochemical reduction of carbonates into -COOH, contributing to the deactivation of the photocatalyst. This work demonstrates the APXPS efficacy in examining photochemical reactions, charge transfer dynamics and intermediates in potential photocatalysts under near realistic conditions.

Facile Synthesis of Multifunctional Ni(OH)2-supported Core-shell Ni@Pd Nanocomposites for the Electro-oxidation of Small Organic Molecules.

In the domain of proton exchange membrane fuel cells (PEMFCs), the development of efficient and durable catalysts for the electro-oxidation of small organic molecules, especially of alcohols (methanol, ethanol, ethylene glycol, et al.) has always been a hot topic. A large number of related electrocatalysts with splendid performance have been designed and synthesized till now, while the preparation processes of most of them are demanding on experimental operations and conditions. Herein, we put forward a facile and handy method for the preparation of multifunctional Ni(OH)2-supported core-shell Ni@Pd nanocomposites (Ni(OH)2/Ni@Pd NCs) with the assistance of galvanic replacement reaction (GRR) at room temperature and ambient pressure. As expected, the Ni(OH)2 substrate can prevent the aggregation of core-shell (CS) Ni@Pd nanoparticles (NPs) and inhibit the formation of COads and further prevent Pd from being poisoned. The synergistic effect between CS Ni@Pd NPs and Ni(OH)2 substrate and the electronic effect between Pd shell and Ni core contribute to the outstanding electrocatalytic performance for methanol, ethanol, and ethylene glycol oxidation in alkaline condition. This study provides a succinct method for the design and preparation of efficient Pd-based electrocatalysts for alcohol electro-oxidation.

Synthesis and sintering behaviors of core–shell Ni@CrOx nanocapsules as an internal electrode of MLCC

A chromium oxide-coated Ni nanocapsules (NCs) were successfully in-situ fabricated using a DC arc plasma in nitrogen atmosphere. Co-evaporation of the mixture target consisting of coarse Cr2O3 and Ni powders harvested the core–shell Ni@CrOx nanocapsules that obeyed preferential oxidization of elements according to their oxygen potentials and subsequent nucleation and growth processes. In comparison with pure Ni nanoparticles (NPs), the Ni@CrOx NCs exhibited an excellent oxidation resistance (∼40 °C increased), raised onset temperature of sintering, and appropriate shrinkage (∼6.8 % volume change at 1200 °C). The CrOx shell and Ni core have exhibited better compatibility in individual nanoparticles, potentially qualified as an ideal candidate material for the next generation of multi-layer ceramic capacitors (MLCCs).

TiO2 supported non-noble Ni-Fe catalysts for the high yield production of 2,5-dimethylfuran biofuel

The establishment of the future biorefinery schemes requires the sustainable conversion and valorisation of renewable bioresources into eco-friendly fuels and chemicals. To this end, 2,5-dimethylfuran (DMF) is a promising biofuel competitive to benchmarks like ethanol due to high-value intrinsic properties. It can be produced by the catalytic hydrogenation of the 5-hydroxymethylfurfural (HMF) platform molecule, one of the biobased intermediate chemicals derived from the abundant lignocellulosic biomass. We evidenced that bimetallic NiFe alloys supported on TiO2 are earth-abundant non-noble metal-based catalysts allowing the high yield production of DMF to be achieved. We showed that the preparation method and the reduction temperature of the catalyst are of prime importance, and are directly influencing the structure of the supported NiFe bimetallic particles and in consequence the catalyst behaviour. The highest yield to DMF is obtained on a catalyst prepared by co-impregnation and reduced at 500 °C, that features an unperfect core/shell structure of the NiFe alloy, with a partial Fe shell surrounding an Fe-enriched Ni core. The key-feature necessary for achieving high performance lies on the surface structure of the NiFe alloy that allows for an optimum availability of highly active Ni domains. The Ni atoms were maintained highly dispersed by the presence of Fe-containing surface phases. The specific surface structure is proposed to promote the HMF adsorption through the carbonyl group, while preventing from the hydrogenation of the aromatic furan ring to maintain high selectivity.

Evidence for Very Early Planetesimal Formation and 26Al/27Al Heterogeneity in the Protoplanetary Disk

We present a U-corrected Pb–Pb age of 4566.19 ± 0.20 Ma (1.11 ± 0.26 Myr after t 0) for the moderately volatile element rich, andesitic meteorite Erg Chech 002 (EC002). Our Al–Mg isochron defines a 26Al/27Al initial ratio of (8.65 ± 0.09) × 10−6 that corresponds to a 26Al/27Al ratio of × 10−5 for the parent body precursor at the time of solar system formation. Whereas the published bulk chemistry and our high-precision Ca isotope measurement correspond to those for inner solar system materials, the 26Al/27Al ratio overlaps that for outer solar system CI chondrites. This indicates that the carriers and/or processes responsible for the nucleosynthetic isotope compositions for inner and outer disk materials are different than those controlling the heterogeneous distribution of 26Al. A low μ 26Mg* initial value of −6.1 ± 1.7 ppm infers a source region with a subchondritic Al/Mg ratio until 1.1 Myr after t 0 such that melt generation must have immediately preceded its crystallization. With 26Al as the main heating source, a modeled temperature–time path for a 100 km radius parent body with our inferred 26Al abundance suggests that accretion must have occurred before 0.5 Myr after t 0 to reach melting temperatures at appropriate depths within 1.1 Myr. This requires that the parent body formed very early within the protoplanetary disk, consistent with predictions of rapid formation of planetesimals by streaming instabilities within high-density dust filaments during the earliest phase of the protoplanetary disk. Finally, an absence of initial Pb in this otherwise moderately volatile-rich achondrite implies Pb was effectively sequestered to the Fe–Ni core.

Confined magnetic vortex motion from metal-organic frameworks derived Ni@C microspheres boosts electromagnetic wave energy dissipation

Magnetic domain structure plays an important role in regulating the electromagnetic properties, which dominates the magnetic response behaviors. Herein, unique magnetic vortex domain is firstly obtained in the Ni nanoparticles (NPs) reduced from the Ni-based metal-organic frameworks (MOFs) precursor. Due to both the high symmetry spheres and boundary restriction of graphited carbon shell, confined magnetic vortex structure is generated in the nanoscale Ni core during the annealing process. Meanwhile, MOFs-derived [email protected] assembly powders construct special magnetic flux distribution and electron migration routes. MOFs-derived [email protected] microspheres exhibit outstanding electromagnetic (EM) wave absorption performance. The minimum reflection loss value of [email protected]–V microspheres with vortex domain can reach −54.6 ​dB at only 2.5 ​mm thickness, and the efficient absorption bandwidth up to 5.0 ​GHz at only 2.0 ​mm. Significantly, configuration evolution of magnetic vortex driven by the orientation and reversion of polarity core boosts EM wave energy dissipation. Magnetic coupling effect among neighboring [email protected] microspheres significantly enhances the magnetic reaction intensity. Graphitized carbon matrix and heterojunction Ni–C interfaces further offer the conduction loss and interfacial polarization. As result, MOFs-derived [email protected]–V powders display unique magnetic vortex, electronic migration network, and high-performance EM wave energy dissipation.

Preparation of porous TiNi intermetallic compound and the corrosion behavior in NaCl solution

Porous TiNi intermetallic compounds have a promising future as biomaterials, with some challenges for their corrosion resistance. In this work, TiNi intermetallic compound was prepared by reactive synthesis of elemental powders. The evolution of the microstructure and phase composition of TiNi at different temperatures was studied. And the electrochemical corrosion behavior of TiNi intermetallic compound in NaCl solution was investigated by electrochemical tests. The results show the formation of a core-shell structure during the sintering process, where Ni is the core and Ti2Ni, TiNi and TiNi3 are the shells. With uniform diffusion, a large pore replaces the Ni core due to the Kirkendall effect. TiNi intermetallic compound has a well-developed open pore structure with an open pore ratio of 50.98%. TiNi intermetallic compound exhibits better corrosion resistance compared to Ni and Ti, which can be attributed to the generation of passivation film on the surface.

Effect of microstructure on the thermo-power of thermoelectric composite of the Bi<sub>2</sub>Te<sub>3</sub> (matrix) + <i>x</i>Ni (filler) system

The patterns of effect of the ferromagnetic filler content on the features in the microstructure of “Ni core–shell NiTe2” inclusions, changes in the Seebeck coefficient and electron concentration in samples of the Bi2Te3 (matrix) + xNi (filler) composites with x = 0.00; 0.50; 0.85; 1.25 and 1.50 wt % have been found. It is shown that the Seebeck coefficient in the composites x = 0.50 and 0.85 exceeds the calculated values, which may be due to additional scattering of electrons by the magnetic moments of inclusion atoms.