Ni2P Nanoparticles Research Articles

ChemInform Abstract: A Facile Molecular Precursor Route to Metal Phosphide Nanoparticles and Their Evaluation as Hydrodeoxygenation Catalysts.

AbstractPhase‐pure Ni2P (I), Rh2P (II), and Pd3P (III) nanoparticles (NPs) are prepared in a one‐pot reaction using Ni(PPh3)2(CO)2 and PPh3 (1:4) or Rh(PPh3)2(CO)Cl or Pd(PPh3)4 in dry oleylamine and 1‐octadecene (320 °C, 2 h for (I); 300 °C, 1 h for (II) and (III)) followed by addition of CHCl3 and iPrOH to precipitate the NPs.

Template-free synthesis of Ni2P hollow microspheres with great photocatalytic and electrochemical properties

The hollow Ni2P microspheres were prepared using a facile one-step template-free solvothermal method. The products were characterized and the results showed that they were pure hexagonal Ni2P microspheres, made up of large amounts of Ni2P nanoparticles, and had an obvious inner space in the central of the microspheres. After being investigated, it was found that these Ni2P hollow spheres initially were some solid spheres, but after a specified time, they were converted to a hollow structure by an Ostwald ripening process, some even had a multi-wall hollow structure. Meanwhile, the as-prepared Ni2P hollow spheres showed a good photocatalytic degradation performance for Methylene Blue in aqueous solution. Electrochemical measurements turned out that the Ni2P hollow spheres have a great cycling performance. The initial discharge capacity capacity of is Ni2P hollow spheres up to 660 mAh g−1 and it always keep in about 300 mAh g−1 within 100 cycles at the current density of 100 mA g−1.

Evaluation of Silica-Supported Metal and Metal Phosphide Nanoparticle Catalysts for the Hydrodeoxygenation of Guaiacol Under Ex Situ Catalytic Fast Pyrolysis Conditions

A series of metal and metal phosphide catalysts were investigated for the hydrodeoxygenation of guaiacol under ex situ catalytic fast pyrolysis conditions (350 °C, 0.5 MPa, 12 H2:1 guaiacol, weight hourly space velocity 5 h−1). Ligand-capped Ni, Pt, Rh, Ni2P, and Rh2P nanoparticles (NPs) were prepared using solution-phase synthesis techniques and dispersed on a silica support. For the metal phosphide NP-catalysts, a synthetic route that relies on the decomposition of a single molecular precursor was employed. The reactivity of the NP-catalysts was compared to a series of reference materials including Ni/SiO2 and Pt/SiO2 prepared using incipient wetness (IW) impregnation and a commercial (com) Pt/SiO2 catalyst. The NP-Ni/SiO2 catalyst exhibited the largest reduction in the oxygen mol% of the organic phase and outperformed the IW-Ni/SiO2 material. Although it was less active for guaiacol conversion than NP-Ni/SiO2, NP-Rh2P/SiO2 demonstrated the largest production of completely deoxygenated products and the highest selectivity to anisole, benzene, and cyclohexane, suggesting that it is a promising catalyst for deoxygenation of aryl-OH bonds. The com-Pt/SiO2 and IW-Pt/SiO2 catalyst exhibited the highest normalized rate of guaiacol conversion per m2 and per gram of active phase, respectively, but did not produce any completely deoxygenated products.

New asymmetric and symmetric supercapacitor cells based on nickel phosphide nanoparticles

A facile one-pot solvothermal method has been developed to synthesize nickel phosphide (Ni2P) nanoparticles which were further assembled into new asymmetric and symmetric supercapacitor cells. The electrochemical properties of these assembled supercapacitor cells were investigated in 3.0 mol L−1 KOH electrolyte. Results show that the asymmetric supercapacitor cells based on Ni2P nanoparticles and activated carbon exhibited excellent electrochemical properties, i.e.: a stable electrochemical window of 0–1.5 V, higher energy density of 64.6 Wh kg−1 at a power density of 1029 W kg−1 and excellent cycling stability (95.1% capacitance retention). But the symmetric supercapacitor cells with Ni2P nanoparticles as positive/negative electrodes show narrower voltage window, lower specific capacitance and the resulted lower energy density which largely restricted the real application. Additionally, two asymmetric supercapacitor cells linked in series can be charged and then discharged to light a red light-emitting diode and drive a rotating motor. All these results demonstrate the asymmetric supercapacitor cells based on Ni2P nanoparticles and activated carbon have the promising potential application in the field of high-performance energy storage.

Preparation of Nickel Phosphide Hydrodesulfurization Catalysts Assisted by Supercritical Carbon Dioxide

AbstractTo meet the increasing demand for clean fuels, deep hydrotreatment reactions are required, and thereby, improvement of the performance of the catalysts is highly desired. Silica‐supported nickel phosphide (Ni2P) nanoparticles have been reported to be efficient catalysts for hydrodesulfurization (HDS) reactions. We propose herein an innovative preparation method assisted by supercritical carbon dioxide (scCO2) to produce highly active Ni2P nanoparticles combining small size and high reducibility. In addition, scCO2 promotes the formation of the Ni2P phase with respect to the less active Ni12P5 phase. Such phosphide catalysts exhibit high activity for the HDS of 4,6‐dimethyldibenzothiophene, with a rate constant up to one order of magnitude higher than that of non‐supercritical references and close to conventional alumina supported NiMoS catalyst.

Nickel phosphide nanoparticles-nitrogen-doped graphene hybrid as an efficient catalyst for enhanced hydrogen evolution activity

Development of hybrid catalysts with high activity, good stability and low cost is extremely desirable for hydrogen production by electrolysis of water. In this work, a hybrid composed of Ni2P nanoparticles (NPs) on N-doped reduced graphene oxide (NRGO) is synthesized via an in situ thermal decomposition approach for the first time and investigated as a catalyst for the hydrogen evolution reaction (HER). The as-synthesized Ni2P/NRGO hybrid exhibits an enhanced catalytic activity with low onset overpotential (37 mV), a small Tafel slope (59 mV dec−1), a much larger exchange current density (4.9 × 10−5 A cm−2), and lower HER activation energy (46.9 kJ mol−1) than Ni2P/RGO hybrid. In addition, the Ni2P/NRGO hybrid maintains its catalytic activity for at least 60′000 s in acidic media. The enhanced catalytic activity is attributed to the synergistic effect of N-doped RGO and Ni2P NPs, the charged natures of Ni and P, as well as the high electrical conductivity of Ni2P/NRGO hybrid. This study may offer a new strategy for improving the electrocatalytic activity for hydrogen production.

Ni2P-Graphite Nanoplatelets Supported Au–Pd Core–Shell Nanoparticles with Superior Electrochemical Properties

Nanoparticles of Au–Pd with core–shell structure were synthesized through the coreduction of HAuCl4 and Na2PdCl4 in aqueous media by using cetyltrimethylammonium chloride as a reducing agent. The morphology and structure of the core–shell NPs were confirmed by transmission electron microscopy, X-ray diffraction, and UV–vis spectroscopy. We further demonstrate that the core–shell structure is formed as a synergistic result of low interfacial energy and small lattice mismatch between Au and Pd, different redox potentials of PdCl42–/Pd and AuCl4–/Au, and low reduction rates of HAuCl4 and Na2PdCl4. The catalyst of Au–Pd core–shell nanoparticles supported on Ni2P–graphite nanoplatelets (Au@Pd/Ni2P-GNPs) exhibits a noticeably higher activity than Pd and Pt catalysts in electrochemical ethanol oxidation. Moreover, we show that the activity and stability of Au–Pd core–shell for ethanol oxidation can be significantly enhanced using Ni2P nanoparticles as a cocatalyst. The prepared Au@Pd/Ni2P-GNPs catalyst exhibits ...

The nature of active sites of Ni2P electrocatalyst for hydrogen evolution reaction

Nano-scaled Ni2P particles were synthesized by ligand stabilization method and applied for hydrogen evolution reaction (HER). X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray absorption fine structure (XAFS) spectroscopy were employed to examine structural properties of Ni2P nanoparticles. The electrocatalytic HER activity and stability for the Ni2P nanocatalyst were tested in 0.5M H2SO4, and the Ni2P electrocatalyst exhibited a low onset potential for the HER at around −0.02V vs. RHE, a little more negative compared to the Pt catalyst which shows almost 0V vs. reversible hydrogen electrode (RHE), and the Tafel slope of 75mV per decade, i.e. following Volmer step as a rate-determining step. Density functional theory (DFT) calculations for hydrogen adsorption over Ni2P surfaces (001) and (002) revealed that the hydrogen adsorption might occur via two reaction pathways: consecutive or simultaneous hydrogen adsorption. The consecutive hydrogen adsorptions on threefold hollow (TFH)-Ni site followed by on P(II) site on a Ni2P (001) surface led to a lower reaction barrier than simultaneous hydrogen adsorption. These results thus demonstrated that the Volmer step might follow consecutive adsorption mechanism over the Ni2P surface.

Nanostructured nickel phosphide supported on carbon nanospheres: Synthesis and application as an efficient electrocatalyst for hydrogen evolution

New electrocatalysts to replace noble metal catalysts for the hydrogen evolution reaction (HER) are highly desired to produce renewable and environmentally-friendly energy. In this work, nanostructured nickel phosphides supported on carbon nanospheres (CNSs) with different carbon content (Ni2P/CNSs-x, x = 10, 20, 40, 60) are synthesized by thermal decomposition using nickel acetylacetonate as nickel source and trioctylphosphine as phosphorus source in an oleylamine solution containing CNSs for the first time. The structure and morphology are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and N2 adsorption-desorption. Then the electrocatalytic properties of as-synthesized Ni2P/CNSs-x for the HER are studied. In addition, the Ni/CNSs-20 hybrid is synthesized and the electrocatalytic properties are studied. The results show that all the Ni2P/CNSs hybrids exhibit higher catalytic activity than the Ni/CNSs-20 hybrid. The catalytic activity of the as-synthesized Ni2P/CNSs hybrid can be enhanced by changing the carbon content. The superior catalytic activity is attributed to the coupling effect between the Ni2P nanoparticles and CNSs, the electronic effect of Ni, the ensemble effect of P, the large surface area, and the high electron conductivity of CNSs. This study paves the way for the design of HER electrocatalysts with high performance and low-cost that can be employed under acid conditions.

Ni₁₂P₅ nanoparticles decorated on carbon nanotubes with enhanced electrocatalytic and lithium storage properties.

Transition-metal phosphides (TMPs) have been proved to be of great importance in electrochemical energy conversion and Li-ion storage. In this work, we have designed a useful one-pot hot-solution colloidal synthetic route for synthesizing a new kind of unique hybrid nanostructures (the Ni12P5/CNT nanohybrids) by direct in situ growth of Ni12P5 nanocrystals onto oxidized multiwall carbon nanotubes (CNTs). The CNTs can improve the conductivity of the hybrids and effectively prevent the aggregation of Ni12P5 nanoparticles in the cycle process. When they are evaluated as a novel non-noble-metal hydrogen evolution reaction (HER) catalyst operating in acidic electrolytes, the Ni12P5/CNT nanohybrids exhibit an onset overpotential as low as 52 mV and a Tafel slope of 56 mV dec(-1) and only require overpotentials of 65 and 129 mV to attain current densities of 2 and 10 mA cm(-2), respectively. Moreover, they also exhibit enhanced electrochemical performance for lithium-ion batteries serving as an anode material; the Ni12P5/CNT nanohybrids show a high capacity, excellent cycling stability and good rate performance. Their unusual properties arise from a synergetic effect between Ni12P5 and CNTs.

One-step synthesis of nickel and cobalt phosphide nanomaterials via decomposition of hexamethylenetetramine-containing precursors

Dispersed pure phases of Ni2P and Co2P nanoparticles with high surface areas were prepared from one-step decomposition of hexamethylenetetramine (HMT)-containing precursors under an inert atmosphere. The solids before and after decomposition and the evolution of gas during the processes were studied by various characterization techniques. The HMT precursors underwent three decomposition stages: low-, moderate- and high-temperature stages. The formation of phosphides was observed at the high-temperature decomposition stage, in which Ni (Co) and P species were reduced by the decomposition products (C, H2 and CH4) of HMT to yield Ni (Co) phosphides, with the release of COx and H2O. Note that in contrast to the traditional H2-temperature-programmed reduction (H2-TPR) method, the HMT-based method produced CO as a major gas product rather than H2O. The better dispersions and higher surface areas of the as-prepared phosphide nanoparticles were achieved probably due to the mitigation of hydrothermal sintering.

Novel synthesis of dispersed molybdenum and nickel phosphides from thermal carbonization of metal- and phosphorus-containing resins

Dispersed pure phases of MoP and Ni2P nanoparticles supported by carbon were synthesized by carbonization of metal- and phosphorus-containing resins under an inert atmosphere. The solid products and the evolution of gases during the carbonization process were investigated by various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), N2 adsorption-desorption analysis, and mass spectrometry (MS). The resins underwent two carbonization stages: the low-temperature carbonization stage (<650 °C) and the high-temperature carbonization stage (≥650 °C). There was an initial reduction of Mo and Ni precursors in the low-temperature region. However, the formation of phosphides was observed in the high-temperature carbonization stage, in which Mo(Ni) and POx species were further reacted with the carbonization products (C, H2 and CH4) to yield Mo(Ni) phosphide. Note that compared with the traditional H2-temperature-programmed reduction (H2-TPR) method, this novel synthesis route produced a large amount of CO(x) besides H2O, leading to a lower water vapor pressure. In addition, the residual carbon produced from resin can play a role in bonding of nanoparticle aggregation. Therefore, the better dispersions and higher surface areas of the as-prepared phosphide nanoparticles were attributed to the mitigation of hydrothermal sintering and the intimate contact between phosphide nanoparticles and carbon species.

Metal–organic framework-derived nickel phosphides as efficient electrocatalysts toward sustainable hydrogen generation from water splitting

Ni-based metal–organic framework (MOF)-derived Ni2P nanoparticles exhibited high-performance for electrochemical HER, as manifested by a low overpotential and a large cathodic current density.

Bottom-Up Assembly of Ni2P Nanoparticles into Three-Dimensional Architectures: An Alternative Mechanism for Phosphide Gelation

The synthesis of Ni2P nanoparticle three-dimensional architectures using two different approaches is reported. The oxidation-induced sol–gel method involves chemical oxidation of surface phosphorus to form P–O–P linkages between particles in the gel network, similar to the mechanism originally reported for InP nanoparticles. The second method, metal-assisted gelation, occurs by cross-linking of pendant carboxylate functionalities on surface-bound thiolate ligands via metal ions to yield an interconnected particle network. The method of gel network formation can be tuned by changing the surface ligand terminal functionalities and the nature (oxygen-transferring or non-oxygen-transferring) of the oxidant. Both methods produce porous, high surface area materials with thermal stabilities above 400 °C.

One-step synthesis and graphene-modification to achieve nickel phosphide nanoparticles with electrochemical properties suitable for supercapacitors

A facile one-step method has been developed to synthesize nickel phosphide (Ni2P) nanoparticles which were further modified by graphene to form graphene-modified Ni2P nanocomposites. All of the synthesized samples were characterized in detail and investigated the corresponding electrochemical properties. Results show that the supercapacitor electrodes based on graphene-modified Ni2P nanocomposites exhibit better electrochemical properties compared to free Ni2P nanoparticles. When the loaded amount of graphene is 5% (wt%), the nanocomposite electrodes show higher specific capacitance, obviously improved cycle stabilization, better rate capability and higher energy density. This enhanced electrochemical behavior results from the graphene-modified Ni2P nanocomposite network structure which not only promotes efficient charge transport and electrolyte diffusion, but also prevents the volume expansion/contraction and corrosion of Ni2P nanoparticles. These encouraging findings demonstrate the possibility of graphene-modified Ni2P nanocomposites for applications in high-performance supercapacitors.

Ni2P nanoparticle films supported on a Ti plate as an efficient hydrogen evolution cathode.

In this communication, we report a two-step strategy for low-temperature construction of Ni2P nanoparticle films supported on a Ti plate (Ni2P/Ti). When used as an integrated hydrogen evolution cathode, the Ni2P/Ti electrode exhibits remarkable catalytic activity, superior stability and nearly 100% Faradaic efficiency in acidic solutions, and it needs overpotentials of 138 and 188 mV to afford current densities of 20 and 100 mA cm(-2), respectively.

Ni12P5 nanoparticles as an efficient catalyst for hydrogen generation via electrolysis and photoelectrolysis.

The exploitation of a low-cost catalyst is desirable for hydrogen generation from electrolysis or photoelectrolysis. In this study we have demonstrated that nickel phosphide (Ni12P5) nanoparticles have efficient and stable catalytic activity for the hydrogen evolution reaction. The catalytic performance of Ni12P5 nanoparticles is favorably comparable to those of recently reported efficient nonprecious catalysts. The optimal overpotential required for 20 mA/cm(2) current density is 143 ± 3 mV in acidic solution (H2SO4, 0.5 M). The catalytic activity of Ni12P5 is likely to be correlated with the charged natures of Ni and P. Ni12P5 nanoparticles were introduced to silicon nanowires, and the power conversion efficiency of the resulting composite is larger than that of silicon nanowires decorated with platinum particles. This result demonstrates the promising application potential of metal phosphide in photoelectrochemical hydrogen generation.

Control of Branching in Ni3C1–xNanoparticles and Their Conversion into Ni12P5Nanoparticles

Dendritic Ni3C1–x nanoparticles (NPs) with controlled branching have been synthesized through the thermolysis (230 °C) of nickel acetylacetonate using oleylamine as a reducing agent and 1-octadecene (ODE) as the solvent. Addition of trioctylphosphine (TOP) as a ligand inhibits formation of dendritic shapes and prevents incorporation of C, resulting in spherical Ni NPs. In comparison, when using octadecane (ODA) or trioctylphosphine oxide (TOPO) as the solvent, Ni NPs are obtained at 230 °C that have fewer, larger branches than when using ODE. Higher temperatures are required for incorporation of C from ODA or TOPO into Ni NPs, resulting in Ni3C1–x NPs. Therefore, the allyl group in ODE facilitates formation of Ni3C1–x NPs at lower temperatures. Conversion of dendritic Ni3C1–x NPs into Ni12P5 NPs after adding TOP and heating to 300 °C results in the formation of multiple voids in the branches, rather than yolk-in-shell structures or unfilled single voids observed for spherical NPs.

Effects of highly crumpled graphene nanosheets on the electrochemical performances of pseudocapacitor electrode materials

Highly crumpled graphene nanosheets (GS) with a BET surface area as high as 722.1 m2g−1 is prepared by a thermal exfoliation method. A systematical investigation is performed on the electrochemical performances of porous Ni2P/GS nanocomposite synthesized by the low temperature solid state reaction method. It is shown that Ni2P nanoparticles anchor on graphene sheets producing a porous structure and GS have beneficial effects on the electrochemical properties of Ni2P nanoparticles when investigated as pseudocapacitor materials. The novel Ni2P/GS composite electrode exhibits a superior specific capacitance of 1912 F g−1 and 888 F g−1 at current densities of 5 and 50mAcm−2, respectively. The specific capacitance decreases to 1473 F g−1 after 2500 cycles, suggesting its excellent cycling stability. It is confirmed that the GS with good electrical conductivity serve as a conducting network for fast electron transfer between the active materials and charge collector, as well as buffered spaces to accommodate the volume expansion/contraction during cycling, thus, leading to enhancement of the electrochemical properties of the Ni2P electrode.

Graphene-wrapped Ni2P materials: a 3D porous architecture with improved electrochemical performance

Ni2P/graphene hybrid with a 3D architecture has been successfully accomplished through a series of controlled chemical processes. In contrast to random mixture of Ni2P nanoparticles and graphene nanosheets, the architecture hybrid exhibits superior electrochemical stability because the Ni2P nanoparticles are firmly riveted on the graphene sheets. The 3D graphene network enhances the electrical conductivity over the 2D nanostructure. As anode materials for lithium-ion batteries, the graphene-wrapped Ni2P nanoparticles can deliver a reversible capacity of ~400 mAh g−1 after 30 cycles with nearly no fading and also exhibit a good rate performance. The graphene network can serve as a conducting network for fast electron transfer from all directions between the active materials and charge collector, and better buffer spaces to accommodate the volume expansion/contraction during discharge/charge process, which can be considered to contribute to the remarkable cyclic stability, thereby pointing to a new synthetic route to hybridizing graphene with active materials for advanced lithium ion batteries.