Ultra-small Ni Nanoparticles Research Articles

Ultrafine Ni-MoOx Nanoparticles Anchored on Nitrogen-Doped Carbon Nanosheets: A Highly Efficient Noble-Metal-Free Catalyst for Ammonia Borane Hydrolysis.

The development of low-cost and high-efficiency catalysts for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) is still a challenging technology. Herein, ultrafine MoOx-doped Ni nanoparticles (~3.0 nm) were anchored on g-C3N4@glucose-derived nitrogen-doped carbon nanosheets via a phosphate-mediated method. The strong adsorption of phosphate-mediated nitrogen-doped carbon nanosheets (PNCS) for metal ions is a key factor for the preparation of ultrasmall Ni nanoparticles (NPs). Notably, the alkaline environment formed by the reduction of metal ions removes the phosphate from the PNCS surface to generate P-free (P)NCS so that the phosphate does not participate in the subsequent catalytic reaction. The synthesized Ni-MoOx/(P)NCS catalysts exhibited outstanding catalytic properties for the hydrolysis of AB, with a high turnover frequency (TOF) value of up to 85.7 min-1, comparable to the most efficient noble-metal-free catalysts and commercial Pt/C catalyst ever reported for catalytic hydrogen production from AB hydrolysis. The superior performance of Ni-MoOx/(P)NCS can be ascribed to its well-dispersed ultrafine metal NPs, abundant surface basic sites, and electron-rich nickel species induced by strong electronic interactions between Ni-MoOx and (P)NCS. The strategy of combining multiple modification measures adopted in this study provides new insights into the development of economical and high-efficiency noble-metal-free catalysts for energy catalysis applications.

Ultra-small Ni@NiFe2O4/TiO2 magnetic nanocomposites activated peroxymonosulphate for solar light-driven photocatalytic mineralization of Simazine

In the heterogeneous photocatalytic degradation of environmental contaminants the recovery, reuse of employed nanocatalyst was crucial and it is essentially required for the scale up applications. Besides, designing a magnetic material with heterojunction that can effectively oxidize the toxic organic contaminants to non-toxic substance under different reaction conditions including direct solar light irradiation remains a challenge. Considering the above facts, herein, we tailored heterojunction between the magnetic materials and non-magnetic materials with ultra-small Ni nanoparticles modified NiFe2O4/TiO2 nanostructures (Ni@NiFe2O4/TiO2 magnetic nanocomposites) through a simple sonochemical route. The Raman phonons at ∼ 540 cm−1 consistent to nickel metal nanoparticles and the spinel ferrites crystal structure confirmed the formation of Ni@NiFe2O4/TiO2 magnetic nanocomposites. The reduced optical bandgap of the resulting nanocomposites indicated the effective absorption of direct solar light irradiation when compared to the bare TiO2. Thus in-turn, enhanced the photocatalytic efficiency of simazine degradation in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 11.0 × 10–4 s−1) and augmented the activation of peroxymonosulphate (PMS) in the presence of Ni@NiFe2O4/TiO2 magnetic nanocomposites (k´= 32.5 × 10–4 s−1). Ni@NiFe2O4/TiO2 +PMS exhibited 3 folds enhanced efficiency in the presence of sunlight. The as-prepared NiFe2O4/TiO2 magnetic nanocatalysts were more stable and the efficiency of simazine oxidation was approximately same for the continuous five cycles at the optimized experimental conditions. The Ni@NiFe2O4/TiO2 magnetic nanocomposites preparation and the activation of PMS may promise the applications in an efficient wastewater treatment.

In-situ synthesis of ultra-small Ni nanoparticles anchored on palygorskite for efficient reduction of 4-nitrophenol

4-nitrophenol (4-NP) is an environmental pollutant with high toxicity and strong stability, which is difficult to degrade naturally. Reduction of 4-NP to 4-aminophenol (4-AP), an important chemical intermediate, is an economical and green method. The reduction process demands high-efficient catalysts, and ultra-small metal nanoparticles (NPs) are the great potential ones. Herein, ultra-small and monodisperse Ni nanoparticles (NiNPs) (5.1 nm) were successfully anchored on palygorskite (Pal), using nickel silicate (NiSi) as a welding-like joint, and the ultimate catalysts were NiNPs/NiSi/Pal nanocomposites. The NiNPs were in-situ reduced from the NiSi precursor, which was previously and in-situ grown on Pal. The size of NiNPs was adjustable by the NiSi precursor, while the size of the NiSi precursor was controlled by the etching degree cations of the crystal structure of Pal. The etching degree affected the amounts of octahedral released from Pal, and thus affected the amounts of freshly exposed SiO- bonds, which could capture Ni2+ ions, form SiONi bonds and promote the generation of NiSi. The as-prepared NiNPs/NiSi/Pal nanocomposites exhibited excellent catalytic activity for the reduction of 4-NP (52.67 × 10-3 s−1), and satisfactory recyclability. The excellent catalytic performance is mainly attributed to the full exposure of ultra-small NiNPs, which provides enough active sites and enables fast electron transfer between the catalysts and substrates. It is expected that the work could develop a new avenue for designation of ultra-small and monodisperse non-precious metal NPs, and contribute to the treatment of waste water containing 4-NP.

Ultrasmall metal (Fe, Co, Ni) nanoparticles strengthen silicon oxide embedded nitrogen-doped carbon superstructures for long-cycle-life Li-ion-battery anodes

A universal electrospray-carbonization approach to prepare ternary metal/SiO x /nitrogen-doped carbon (NC) superstructures is proposed, where metal (Fe, Co, Ni, CoNi, FeNi, FeCo and FeCoNi) and small SiO x nanoparticles (NPs) are homogeneously distributed in NC matrix. Metal greatly promotes the electrochemical activity and stability of the SiO x system, which can be considered as high-performance Li-ion-battery anodes. • Metal/SiO x /nitrogen-doped carbon superstructures are designed as LIB anodes. • Nitrogen-doped carbon inhibits the gathering of SiO x and relieves its strain. • Ultrasmall Ni nanoparticles and nitrogen-doped carbon improve the kinetics of SiO x . • The strategy to prepare multiple SiO x - or metal-based composites is universal. For silicon oxides (SiO x ) as a prospective Li-ion-battery anode material, the low inherent conductivity and huge volume fluctuation during cycling immensely limit their electrochemical performance. Herein, a universal electrospray-carbonization approach to prepare ternary metal/SiO x /nitrogen-doped carbon (NC) superstructures is proposed. Accordingly, metal (Fe, Co, Ni, CoNi, FeNi, FeCo and FeCoNi) nanoparticles (NPs) and small SiO x NPs derived from rice husks (RHs) are homogeneously distributed in the NC matrix. Metal (Fe, Co, Ni) NP-embedded NC frameworks avoid the accumulation, increase the conductivity and accommodate adequent volume expansion of SiO x NPs. This results in an enhanced rate capability and excellent cycle stability upon cycling. Besides, Ni/SiO x /NC (NSC) superstructures with ultra-small Ni NPs can exhibit better electrochemical kinetics for fast diffusion of ions and charge transfer and cyclability than Co/SiO x /NC (CSC) and Fe/SiO x /NC (FSC) composites. When NSC superstructures are employed as lithium-ion battery (LIB) anodes, superior specific capacities of 757.5 mA h g −1 at the 200th cycle, as well as superb long cyclability with discharge capacities of 665.0 mA h g −1 for 500 cycles at 500 mA g −1 and 116.3 mA h g −1 at the 5000th cycle, even at 10 A g −1 , are achieved. Furthermore, the easy and general approach for preparing multiple SiO x -, metal- or alloy-based superstructures paves the way for designing high-performance rechargeable batteries and electrocatalysts.

Stable and reusable Ni-based nanoparticles for general and selective hydrogenation of nitriles to amines

Silica supported ultrasmall Ni-nanoparticles allow for general and selective hydrogenation of all kinds of nitriles to primary amines under mild conditions. By calcination of a template material generated from Ni(ii)nitrate and colloidal silica under air and subsequent reduction in the presence of molecular hydrogen the optimal catalyst is prepared. The prepared supported nanoparticles are stable, can be conveniently used and easily recycled. The applicability of the optimal catalyst material is shown by hydrogenation of >110 diverse aliphatic and aromatic nitriles including functionalized and industrially relevant substrates. Challenging heterocyclic nitriles, specifically cyanopyridines, provided the corresponding primary amines in good to excellent yields. The resulting amines serve as important precursors and intermediates for the preparation of numerous life science products and polymers.

In Situ Fabrication of Ultrasmall Ni Nanoparticles from Ni(OH)2 Precursors for Efficient CO2 Reforming of Methane

Metal size is a critical structural parameter for Ni-based catalysts in CO2 reforming of methane. Herein, ultrasmall Ni nanoparticles (3.7 nm) were fabricated from Ni(OH)2 precursors on γ-Al2O3 nanoplates via a simple solution method followed by H2 reduction. The resultant Ni/Al2O3-IS catalyst showed competitive reforming performance. The turnover frequency reached 15.3 s–1 at 700 °C under atmospheric pressure. Methane (CH4) conversion declined marginally from 79.8 to 70.2% after 20 h of reaction. Characterization results reveal that high activity and good stability were endowed by the ultrasmall Ni size and superior coke resistance, respectively. A bifunctional reaction mechanism was identified on the Ni/Al2O3-IS catalyst, wherein the activation of the reactant molecules was facilitated near metal–support interfaces. This work offers a novel strategy to fabricate ultrasmall Ni particles and provides new insights into structure–activity relationships in CO2 reforming of methane.

Highly dispersed and ultra-small Ni nanoparticles over hydroxyapatite for hydrogenation of levulinic acid

Highly dispersed and ultra-small Ni nanoparticles over hydroxyapatite for hydrogenation of levulinic acid

Heterostructure design of Ni/C/porous carbon nanosheet composite for enhancing the electromagnetic wave absorption

The development of advanced electromagnetic wave (EMW) materials with high reflection loss (RL), wide effective absorption bandwidth (EAB), low filler loading and thin matching thickness is considered as an effective strategy to solve the EMW pollution in emerging areas. Nevertheless, it is still a tremendous challenge to design a reasonable structure and a proper composition to meet the requirements of advanced absorbing materials. Herein, a nanocomposite composed of nitrogen-doped (N-doped) biomass-derived carbon (BDC) and Ni/C nanosphere derived from Ni-MOF (MPC@Ni/C) has been designed and synthesized. The results show that the continuous conductive network can not only improve the conductive loss, but also provide the prospect for the reflection and scattering of EMW. Also, the petal-like MPC@Ni/C nanocomposite with a great quantity defects and heterogeneous interfaces delivers multi-polarization. At the same time, the ultra-small Ni nanoparticles and Ni/C nanospheres with good dispersion on carbon materials are beneficial toward dielectric-magnetic combination, resulting in impedance matching. Accordingly, the optimized MPC@Ni/C nanocomposite exhibits extraordinary microwave absorption performance. Precisely, when the filler loading is 20 wt%, the maximum RL of MPC@Ni/C reaches −73.8 dB and a corresponding EAB is up to 5.8 GHz with 2.2 mm thickness. This work fills the vacuum in the study of the nanocomposites composed of MOF derivatives and BDC. It provides a reference value for the synthetic strategies in designing high-performance absorbing materials.

Defect-rich Ni3Sn4 quantum dots anchored on graphene sheets exhibiting unexpected reversible conversion reactions with exceptional lithium and sodium storage performance

In the present study, a simple, ultrafast microwave irradiation procedure is employed to develop low-cost, zero-band-gap Ni3Sn4 quantum dots (~4–6 nm in size) with abundant nanopores. These quantum dots are uniformly anchored on reduced graphene oxide (rGO) sheets, which are then utilized as anode materials for both Li+ and Na+ storage. This rational defect engineering approach can cause unexpected, fully reversible conversion reactions and pseudocapacitive interfacial Li/Na storage mechanisms. The nanopores also offer unblocked pathways for Li+/Na+ ion transfer and significantly improve the electrical conductivity. Furthermore, the synergistic effects of ultrasmall Ni nanoparticles and rGO sheets solve the crucial challenges of coarsening Sn nanocrystals and severe volume changes that occur during repeated cycles, thereby delivering remarkable initial discharge capacities, excellent rate capability, and exceptional cyclic performance for ultradurable cycling in both the Li-ion and Na-ion batteries. More importantly, this simple, fast approach opens an effective avenue for the design and fabrication of various porous, defect-enriched nanomaterials for different applications.

Core-satellite ultra-small hybrid Ni@BT nanoparticles: A new route to enhanced energy storage capability of PVDF based nanocomposites

Polymer-based composites comprising of high dielectric constant ceramic nanoparticles are widely used in dielectric capacitors due to their excellent energy storage and processing properties. In this study, ultra-small Ni nanoparticles were used to fabricate core-satellite structured hybrid Ni@BT nanoparticles. Compared with BT/PVDF composites, the Ni@BT/PVDF nanocomposites exhibited the enhanced energy storage properties due to the low electric conductivity, small dielectric loss and improved breakdown strength. The maximum discharged energy density reached 9.55 J/cm3 for nanocomposites with 3 vol% Ni@BT at the electric field of 350 kV/mm, which was nearly eight times of commercial BOPP (1.2 J/cm3 at 640 kV/mm) and was around 208% compared to the pristine PVDF (4.58 J/cm3 at 340 kV/mm). The improved energy density of the nanocomposites could be attributed to the Coulomb-blockade effect of the introduced ultra-small Ni nanoparticles exactly. This work provides an effective approach to improve the energy storage property of dielectric nanocomposites.

Facile template-free synthesis of Ni-SiO2 catalyst with excellent sintering- and coking-resistance for dry reforming of methane

Ni-SiO2 catalysts were synthesized by facile template-free hydrothermal method with ammonia-assisted via using low-cost silica sol as precursor and successfully employed to dry reforming of methane reaction. It was found that ultra-small Ni nanoparticles around 3.2 nm rationally obtained with high dispersion. The strong metal-support interaction generated from the in-situ ammonia-assisted process further stabilized the Ni species during the DRM reaction. Furthermore, the high activity, stability and H2/CO ratio of Ni-SiO2 remained initial value even continued reacting at 700 °C for 30 h. Almost no visualization of metal growth and carbon deposition were observed on the spent catalyst.

Functionalized multi-walled carbon nanotubes supported Ni-based catalysts for adiponitrile selective hydrogenation to 6-aminohexanenitrile and 1,6-hexanediamine: Switching selectivity with [Bmim]OH

Functionalized multi-walled carbon nanotubes supported nickel-based catalysts were prepared and applied in adiponitrile (ADN) hydrogenation. The characterization results show that different functional groups such as NH2, COOH, OH on MWCNTs surface can effectively act on metal ions by electrostatic attractions and chemical interactions so as to provide nucleation sites, and N species in MWCNTs can act as active sites for Ni deposition due to the strong electronic interactions between N species and Ni so as to promote ultra-small Ni nanoparticles formation, decrease NiO reduction activation energy, increase zero-valent Ni amounts as well as Ni nanoparticles dispersion. Furthermore, the doped N increases the lewis basicity, which favors the formation of primary amine of 6-aminohexanenitrile (ACN) and 1,6-hexanediamine (HDA). Moreover, the basic ionic liquid [Bmim]OH may switch the selectivity by inhibiting nucleophilic addition of the primary amine to the α-carbon of aldimine via the stabilization of NH2 groups in the amino-imine intermediates so as to impede by-products formation. In addition, the mechanism for ADN hydrogenation in [Bmim]OH was studied by density functional theory calculations. Under optimized conditions, it gives 97.80% total selectivity to ACN and HDA at 95.34% ADN conversion over Ni/N-MWCNTs-800 in the presence of [Bmim]OH.

Ultra-small Ni-VN nanoparticles co-embedded in N-doped carbons as an effective electrode material for energy storage

As a class of emerging anode material, much attention has been dominated to vanadium nitride (VN) in view of its high specific capacitance, exceptional conductivity and proper operating potential window (OPW). Herein, ultra-small Ni nanoparticles (NPs) and VN NPs have been embedded in N-doped carbons (NCs) nanosheets as an anode material for supercapacitors (SCs), making the good use of the conductivity of Ni NPs and NCs nanosheets, as well as the excellent specific capacitance of VN NPs, the novel 3-Ni/VN/NCs-7 composite electrode exhibits an admirable specific capacitance of 236 F g−1 at 1 A g−1. Furthermore, the (−) 3-Ni/VN/NCs-7//CuCo2O4 (+) asymmetrical supercapacitor (ASC) and 3-Ni/VN/NCs-7 symmetrical supercapacitor (SSC) have been assembled, respectively. The (−) 3-Ni/VN/NCs-7//CuCo2O4 (+) ASC device shows a capacitance of 65 F g−1 at a large OPW of 1.8 V. More importantly, it achieves an energy density of 25 Wh kg−1 at 930 W kg−1 and a superb cycling stability (73.5% retention after 5000 cycles). Strikingly, the 3-Ni/VN/NCs-7 SSC device not only presents surpassing cycling behavior, but also possesses favorable energy density of 13.4 Wh kg−1 at a power density of 600 W kg−1, which is superior to most of the carbon-based materials.

Ultrasmall Ni nanoparticles embedded in Zr-based MOFs provide high selectivity for CO2 hydrogenation to methane at low temperatures

Highly monodisperse Ni NPs in UiO-66 give both excellent activity and selectivity for CO2 methanation at low temperatures.

Size-Tunable Ni Nanoparticles Supported on Surface-Modified, Cage-Type Mesoporous Silica as Highly Active Catalysts for CO2 Hydrogenation

In this study, ultrasmall Ni nanoparticles (Ni NPs) were controllably supported in the cage-type mesopores of −COOH-functionalized mesoporous silica SBA-16 (denoted as Ni(x)@S16C, where x is the Ni loading) via wet impregnation under alkaline conditions, followed by thermal reduction. The particle sizes of the Ni NPs ranged from 2.7 to 4.7 nm, depending on the Ni loading. Under the appropriate alkaline conditions (i.e., pH 9) deprotonation of the carboxylic acid groups on the cage-type mesopore surfaces endowed the effective incorporation of Ni2+ precursors via favorable electrostatic interactions, and thus well-dispersed Ni NPs confined in the cage-type mesopores of SBA-16 were achieved. The combination of the cage-type mesopores and the surface functionality provided dual beneficial features to confine the immobilized Ni NPs and to tune their particle sizes. The remarkably enhanced catalytic activities of the Ni(x)@S16C materials for CO2 hydrogenation and CH4 formation were demonstrated. The cage-type S...

A pH-responsive assembly based on upconversion nanocrystals and ultrasmall nickel nanoparticles

A hybrid assembly based on NaYF4:Yb3+,Er3+/Tm3+@NaYF4(core@shell) upconversion nanocrystals and ultrasmall Ni nanoparticles (abbreviated as core@shell@Ni) for rapid response towards pH in different PBS solutions.

A highly sensitive sensor for simultaneous determination of ascorbic acid, dopamine and uric acid based on ultra-small Ni nanoparticles

A highly sensitive sensor based on carbon-supported Ni nanoparticles (Ni/C) with ultra-small size was prepared for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The electrochemical response showed excellent electrocatalytic activity toward the oxidation of AA, DA and UA with three well defined oxidation peaks and larger peak separation. Meanwhile, using the ultra-small Ni nanoparticles modified electrode with differential pulse voltammetry (DPV) method, the linear response ranges for the determination of AA, DA and UA were 20–2400, 1–55 and 5–180μM in the coexistence systems of these three species under optimum condition and the detection limits (S/N=3) were 5, 0.05 and 0.1μM, respectively. Especially a much higher sensitivity for Ni/C modified electrode compared to other electrodes was also observed. Moreover, satisfactory results were achieved for the determination of AA, DA and UA in vitamin C tablet, DA hydrochloride injection, fetal bovine serum and human urine samples. The results demonstrated that the electrochemical sensor developed from the ultra-small Ni nanoparticles had advantages of high sensitivity and good selectivity for practical applications.

Ultrasmall superparamagnetic Ni nanoparticles embedded in polyaniline as a lightweight and thin microwave absorber

In this work, we have reported the preparation and lightweight and thin microwave absorbent application of ultrasmall Ni nanoparticles embedded in polyaniline (PANI).