Generalized synthesis of metal phosphide nanorods via thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pump

We synthesized uniform-sized nanorods of transition metal phosphides from the thermal decomposition of continuously delivered metal-phosphine complexes using a syringe pump. MnP nanorods with dimensions of 8 nm x 16 nm and 6 nm x 22 nm sized were synthesized by the thermal decomposition of Mn-TOP complex, which was prepared from the reaction of Mn(2)(CO)(10) and tri-n-octylphosphine (TOP), using a syringe pump with constant injection rates of 10 and 20 mL/h, respectively. When Co-TOP complex, which was prepared from the reaction of cobalt acetylacetonate and TOP, was reacted in a mixture solvent composed of octyl ether and hexadecylamine at 300 degrees C using a syringe pump, uniform 2.5 nm x 20 nm sized Co(2)P nanorods were generated. When cobaltocene was employed as a precursor, uniform Co(2)P nanorods with 5 nm x 15 nm were obtained. When Fe-TOP complex was added to trioctylphosphine oxide (TOPO) at 360 degrees C using a syringe pump and then allowed to age at 360 degrees C for 30 min, uniform-sized FeP nanorods with an average dimension of 12 nm x 500 nm were produced. Nickel phosphide (Ni(2)P) nanorods with 4 nm x 8 nm were synthesized successfully by thermally decomposing the Ni-TOP complex, which was synthesized by reacting acetylacetonate [Ni(acac)(2)] and TOP. We measured the magnetic properties of these nanorods, and some of the nanorods exhibited different magnetic characteristics compared to the bulk counterparts.     

Highly Active Electrocatalysis of the Hydrogen Evolution Reaction by Cobalt Phosphide Nanoparticles

Nanoparticles of cobalt phosphide, CoP, have been prepared and evaluated as electrocatalysts for the hydrogen evolution reaction (HER) under strongly acidic conditions (0.50 M H₂SO₄, pH 0.3). Uniform, multi‐faceted CoP nanoparticles were synthesized by reacting Co nanoparticles with trioctylphosphine. Electrodes comprised of CoP nanoparticles on a Ti support (2 mg cm^?2 mass loading) produced a cathodic current density of 20 mA cm^?2 at an overpotential of ?85 mV. The CoP/Ti electrodes were stable over 24 h of sustained hydrogen production in 0.50 M H₂SO₄. The activity was essentially unchanged after 400 cyclic voltammetric sweeps, suggesting long‐term viability under operating conditions. CoP is therefore amongst the most active, acid‐stable, earth‐abundant HER electrocatalysts reported to date.     

Phase‐Controlled Synthesis of Transition‐Metal Phosphide Nanowires by Ullmann‐Type Reactions

Transition‐metal phosphide nanowires were facilely synthesized by Ullmann‐type reactions between transition metals and triphenylphosphine in vacuum‐sealed tubes at 350–400 °C. The phase (stoichiometry) of the phosphide products is controllable by tuning the metal/PPh₃ molar ratio and concentration, reaction temperature and time, and heating rate. Six classes of iron, cobalt, and nickel phosphide (Fe₂P, FeP, Co₂P, CoP, Ni₂P, and NiP₂) nanostructures were prepared to demonstrate the general applicability of this new method. The resulting phosphide nanostructures exhibit interesting phase‐ and composition‐dependent magnetic properties, and magnetic measurements suggested that the Co₂P nanowires with anti‐PbCl₂ structure show a ferromagnetic–paramagnetic transition at 6 K, while the MnP‐structured CoP nanowires are paramagnetic with Curie–Weiss behavior. Moreover, GC‐MS analyses of organic byproducts of the reaction revealed that thermally generated phenyl radicals promoted the formation of transition‐metal phosphides under synthetic conditions. Our work offers a general method for preparing one‐dimensional nanoscale transition‐metal phosphides that are promising for magnetic and electronic applications.     

Phase-selective synthesis of nickel phosphide in high-boiling solvent for all-solid-state lithium secondary batteries

Nickel phosphide particles were synthesized by thermal decomposition of a nickel precursor in a mixed solution of trioctylphosphine and trioctylphosphine oxide. The crystal phase and morphology of samples prepared by changing the solvents, the amount of trioctylphosphine as a phosphorus source, the reaction temperature, and the nickel precursor were characterized using X-ray diffraction and transmission electron microscopy. Spherical Ni(5)P(4) particles with diameters of 500 nm were obtained using nickel acetylacetonate as a nickel precursor at 360 °C for 1 h in trioctylphosphine oxide. NiP(2) particles with diameters of 200-500 nm were obtained using nickel acetate tetrahydrate at 360 °C for 5 h in trioctylphosphine oxide. All-solid-state cells were fabricated using NiP(2) particles as an active material and 80Li(2)S·20P(2)S(5) (mol %) glass-ceramic as a solid electrolyte. The Li-In/80Li(2)S·20P(2)S(5)/NiP(2) cell exhibited an initial discharge capacity of 1100 mAh g(-1) at a current density of 0.13 mA cm(-2) and retained a discharge capacity of 750 mAh g(-1) after 10 cycles.     

Synthesis, characterization, and self-assembly of pencil-shaped CoO nanorods

We synthesized uniformly sized, pencil-shaped CoO nanorods by the thermal decomposition of a cobalt-oleate complex, which was prepared from the reaction of cobalt chloride and sodium oleate. The diameters and lengths of the CoO nanorods were easily controlled by varying the experimental conditions, such as the heating rate and the amount of Co-oleate complex. The X-ray diffraction pattern revealed that the CoO nanorods have an extraordinary wurtzite ZnO crystal structure. These uniformly sized nanorods self-assembled to form both horizontal parallel arrangements and perpendicular hexagonal honeycomb superlattice structures. Reduction of the nanorods by heating under a hydrogen atmosphere generated either hcp Co or Co(2)C nanorods. Characterization of the CoO nanorods using X-ray absorption spectroscopy, X-ray magnetic circular dichroism spectroscopy, and magnetic measurements showed that they contain a small fraction of ferromagnetic Co impurities.     

Single-crystal colloidal nanosheets of GeS and GeSe

Narrow-band-gap IV-VI semiconductors offer promising optoelectronic properties for integration as light-absorbing components in field-effect transistors, photodetectors, and photovoltaic devices. Importantly, colloidal nanostructures of these materials have the potential to substantially decrease the fabrication cost of solar cells because of their ability to be solution-processed. While colloidal nanomaterials formed from IV-VI lead chalcogenides such as PbS and PbSe have been extensively investigated, those of the layered semiconductors SnS, SnSe, GeS, and GeSe have only recently been considered. In particular, there have been very few studies of the germanium chalcogenides, which have band-gap energies that overlap well with the solar spectrum. Here we report the first synthesis of colloidal GeS and GeSe nanostructures obtained by heating GeI(4), hexamethyldisilazane, oleylamine, oleic acid, and dodecanethiol or trioctylphosphine selenide to 320 °C for 24 h. These materials, which were characterized by TEM, SAED, SEM, AFM, XRD, diffuse reflectance spectroscopy, and I-V conductivity measurements, preferentially adopt a two-dimensional single-crystal nanosheet morphology that produces fully [100]-oriented films upon drop-casting. Optical measurements indicated indirect band gaps of 1.58 and 1.14 eV for GeS and GeSe, respectively, and electrical measurements showed that drop-cast films of GeSe exhibit p-type conductivity.     

Topochemical synthesis of cobalt oxide-based porous nanostructures for high-performance lithium-ion batteries

Two kinds of topochemical conversion routes from cobalt hydroxide precursors to cobalt oxide-based porous nanostructures are presented: pyrolysis in air and hydrothermal treatment by the Kirkendall diffusion effect. These cobalt hydroxide precursors were synthesized by a simple hydrothermal approach with sodium acetate as mineralizer at 200 °C. Detailed proof indicates that the process of cobalt hydroxide precursor growth is dominated by a nucleation, dissolution, renucleation, growth, and exfoliation mechanism. By the topochemical conversion processes several Co(3)O(4) nanostructures, such as cobalt oxide-coated cobalt hydroxide carbonate nanowires, cobalt oxide nanotubes, hollow cobalt oxide spheres, and porous cobalt oxide nanowires, have been synthesized. The obtained Co(3)O(4) nanostructures have also been evaluated as the anode materials in lithium-ion batteries. It was found that the as-prepared Co(3)O(4) nanostructures exhibited high reversible capacity and good cycle performance due to their porous structure and small size.     

Synthesis and characterization of colloidal ternary ZnCdSe semiconductor nanorods

For the synthesis of colloidal ternary ZnCdSe nanorods, CdSe nanorods were first prepared under a mixture of tetradecylphosphonic acid/trioctylphosphine oxide surfactants at 250 degrees C, and then ZnSe shell layer was grown onto CdSe nanorods at 180 degrees C, forming CdSeZnSe core/shell nanorods. Green-yellow emitting ternary ZnCdSe nanorods were obtained by a subsequent alloying process at 270 degrees C for 1-3 h through the diffusion of Zn ions into CdSe nanorods. The photoluminescence quantum yield (QY) of ZnCdSe nanorods was 5%-10%, which is higher than that from pristine CdSe nanorods (0.6%). The QY of these alloy nanorods depends on the alloying time and is discussed in terms of compositional disorders and defects produced by the alloying process. The Raman and time resolved photoluminescence spectroscopies were used to understand the detailed alloying process from CdSeZnSe core/shell to ZnCdSe alloy nanorods.     

Nanocrystals,Nanorods and other Nanostructures of Nickel,Ruthenium, Rhodium and Iridium prepared by a Simple Solvothermal Procedure

The solvothermal decomposition of nickel acetate in n-octylamine medium at 250 °C gives rise to nickel nanostructures while in a hydrocarbon medium NiO nanostructures are obtained. It has been possible to obtain nickel nanorods of 12–15 nm diameter by this means. By carrying out the reaction at a slightly higher temperature, ultra-thin single-crystalline sheets of nickel are obtained. The nanorods and the thin sheets, with the FCC structure, are both ferromagnetic at room temperature, with the nanorods exhibiting high coercivities. It has been possible to obtain ruthenium, rhodium and iridium nanostructures by carrying out the decomposition of the respective metal acetylacetonates in a hydrocarbon (decalin or toluene) or an amine (n-octylamine or oleylamine) around 300 °C. Nanorod formation is favored by linear long-chain amines. The method described by us to prepare the nanostructures of nickel, ruthenium, rhodium and iridium is simple and straightforward compared to the literature procedures, the preparation of single-crystalline thin sheets of nickel by such a solution route being noteworthy. The nanostructures prepared in the amine media could be readily dispersed in hydrocarbon solvents. Dedicated to Professor Dr. Günther Schmid     

Mesoporous Semimetallic Conductors: Structural and Electronic Properties of Cobalt Phosphide Systems

Mesoporous cobalt phosphide (meso‐CoP) was prepared by the phosphorization of ordered mesoporous cobalt oxide (meso‐Co₃O₄). The electrical conductivity of meso‐CoP is 37 times higher than that of nonporous CoP, and it displays semimetallic behavior with a negligibly small activation energy of 26 meV at temperatures below 296 K. Above this temperature, only materials with mesopores underwent a change in conductivity from semimetallic to semiconducting behavior. These properties were attributed to the coexistence of nanocrystalline Co₂P phases. The poor crystallinity of mesoporous materials has often been considered to be a problem but this example clearly shows its positive aspects. The concept introduced here should thus lead to new routes for the synthesis of materials with high electronic conductivity.     

Co3O4纳米催化剂催化CO的形貌效应：合成过程和催化活性

通过催化剂将CO转化为无毒气体仍然是目前减少CO污染的主要手段.随着纳米技术的快速发展,纳米催化剂因其在催化反应中呈现出的独特结构效应（如形貌效应、尺寸效应等）而受到人们的广泛关注.已有大量研究表明,纳米Co3O4作为一种非贵金属氧化物催化剂具有强烈的催化形貌效应,展现出优异的CO低温催化活性.因此,通过合理的设计来调控催化剂粒子的形貌,从而进一步改善催化剂的性能已成为近年来催化剂领域的重要研究方向.对于Co3O4纳米催化剂的可控制备,水热法具有反应温和、操作简便和产品形貌易控等特点.早期的研究主要围绕于Co3O4形貌的可控合成以及不同形貌Co3O4催化剂对其催化活性产生的影响,较少有对其形貌形成机制的报道.特别是在水热反应中,系统研究各反应参数对催化剂各异形貌的形成影响鲜有报道.
　　本文在前人的研究基础上,重点研究了水热反应过程中各主要反应参数对产品形貌控制的影响,绘制了一副不同形貌Co3O4材料的合成过程图,并研究了Co3O4纳米催化剂催化CO氧化的形貌效应.通过水热法先成功合成了三种不同形貌(纳米棒、纳米片和纳米立方)的碱式碳酸钴纳米粒子,然后将其焙烧得到了Co3O4纳米粒子.采用扫描电子显微镜(SEM),透射电子显微镜(TEM), X射线粉末衍射仪(XRD),程序升温还原(H2-TPR和CO-TPR),氮气吸附-脱附比表面积测试(BET),氧气程序升温脱附(O2-TPD), X射线光电子能谱(XPS)等表征手段研究了不同反应参数对纳米碱式碳酸钴前驱体形貌形成的作用和各异形貌Co3O4纳米粒子在催化CO氧化反应中催化性能的差异及原因.
　　结果表明, Co3O4较好地继承了碱式碳酸钴的形貌,在较低温度条件下(≤140°C),钴源(CoCl2或Co(NO3)2)是影响前驱体形貌的关键因素,反应时间只对粒子的尺寸产生较大影响.低温下, CoCl2作为钴源易诱导生产纳米棒状碱式碳酸钴,而Co(NO3)2则有利于纳米片状生成.当温度高于140°C后,无论何种钴源,最终均制得纳米立方体.表面活性剂CTAB对前驱体的均一性和粒子的分散性产生重要影响,加入CTAB后得到的产品尺寸更均一,形貌更加规整.对比于其他两种形貌的样品, Co3O4纳米片显示出更好的CO催化氧化活性.
　　 XPS结果表明,各形貌Co3O4纳米材料的表面组成存在明显差异,活性物种Co3+含量的不同是影响催化活性差异的重要原因. Co3O4纳米片具有更多的Co3+活性位,立方纳米Co3O4表面吸附氧含量较高, Co3O4纳米棒则暴露出相对更多的Co2+.因此,在三种形貌催化剂上CO氧化反应中, Co3O4纳米片表现出最优的催化活性,纳米立方次之,而纳米棒最差. H2-TPR, CO-TPR和O2-TPD等结果也表明, Co3O4纳米片拥有更强的还原性能和脱附氧能力,其次是纳米立方Co3O4.这与XPS结果一致,证实了不同形貌Co3O4纳米催化剂上暴露活性位的数量和表面氧物种的不同是造成彼此间催化CO氧化活性差异的重要原因.此外,通过稳定性测试发现Co3O4纳米片具有较高的催化稳定性,在水蒸气存在的情况下Co3O4纳米片逐渐失活,但随后在干燥条件下其催化活性又逐渐得到恢复.     

Morphology-controllable synthesis of cobalt oxalates and their conversion to mesoporous Co3O4 nanostructures for application in supercapacitors

In this work, one-dimensional and layered parallel folding of cobalt oxalate nanostructures have been selectively prepared by a one-step, template-free, water-controlled precipitation approach by simply altering the solvents used at ambient temperature and pressure. Encouragingly, the feeding order of solutions played an extraordinary role in the synthesis of nanorods and nanowires. After calcination in air, the as-prepared cobalt oxalate nanostructures were converted to mesoporous Co(3)O(4) nanostructures while their original frame structures were well maintained. The phase composition, morphology, and structure of the as-obtained products were studied in detail. Electrochemical properties of the Co(3)O(4) electrodes were carried out using cyclic voltammetry (CV) and galvanostatic charge-discharge measurements by a three-electrode system. The electrochemical experiments revealed that the layered parallel folding structure of mesoporous Co(3)O(4) exhibited higher capacitance compared to that of the nanorods and nanowires. A maximum specific capacitance of 202.5 F g (-1) has been obtained in 2 M KOH aqueous electrolyte at a current density of 1 A g(-1) with a voltage window from 0 to 0.40 V. Furthermore, the specific capacitance decay after 1000 continuous charge-discharge cycles was negligible, revealing the excellent stability of the electrode. These characteristics indicate that the mesoporous Co(3)O(4) nanostructures are promising electrode materials for supercapacitors.     

Glucose-derived carbon sphere supported CoP as efficient and stable electrocatalysts for hydrogen evolution reaction

Glucose-derived carbon sphere supported cobalt phosphide nanoparticles(Co P/C) were synthesized via a concise two-step method. The electrochemical measurement results indicate that the Co P/C prepared at 900 ℃ presents excellent electrocatalytic performance for hydrogen evolution reaction(HER). The overpotential at a current density of 10 m A cm~(-2) is 108 and 163 mV in 0.5 M H_2SO_4 and 1 M KOH, respectively, and maintains its electrocatalytic durability for at least 10 h. This work supplies a new field to challenge the construction of electrocatalysts for HER through using cost-effective carbon supported transition metal phosphides.     

CoP/Co_2P/C纳米材料用于全pH值电催化析氢

在氮气下一步退火含有植酸和钴的前驱体,合成了一种新型的CoP/Co2P/C复合纳米材料作为电催化剂,该催化剂在全pH值范围下表现出优异的电催化析氢活性和稳定性.在0.5mol/L的硫酸中,电流密度为10mA/cm~2时,过电位为135mV.在1mol/L KOH溶液中,CoP/Co_2P/C催化剂需要141 mV的过电位才能使电流密度达到10 mA/cm~2,在0.1mol/L磷酸盐缓冲溶液中,需要155mV的过电位才能使电流密度达到10mA/cm~2.这种优异的析氢活性主要归因于CoP/Co_2P纳米粒子和C层之间的协同作用.     

Rod-Like Co2P Nanostructures: Improved Synthesis, Catalytic Property and Application in the Removal of Heavy Metal

In this paper rod-like cobalt phosphide (Co₂P) nanostructures were successfully synthesized at a large scale via an improved water–ethanol mixed-solvothermal route. White phosphorus and cobalt dichloride were used as starting reactants, hexamethylenetetramine as the pH adjustor, sodium dodecyl benzene sulfonate as the surfactant. The reaction was carried out at 170 °C for 800 min. It was found that the morphology and crystallinity of Co₂P nanostructures could be tuned by the amount of hexamethylenetetramine. Experiments showed that the as-prepared Co₂P nanostructures owned good catalytic activity in the reduction of aromatic nitro compounds. Under the presence of 40 mg L^?1 Co₂P nanostructures, some aromatic nitro compounds, including 4-nitrophenol, 4-nitroaniline, 2,4-dinitrophenol, and 3,5-dinitrosalicylic acid, were fully reduced by NaBH₄ within 3–5 min. Also, the catalytic activities of Co₂P nanostructures could be affected by the morphologies of the final products. Furthermore, the as-obtained Co₂P nanostructures also exhibited good adsorption capacities for Pb²⁺ and Cu²⁺ ions in water resources, indicating that the as-prepared product had potential application in environmental treatments.     

Synthesis and characterization of 3D CoPt nanostructures

Cobalt platinum polypod-like nanostructures were synthesized by thermolytic reduction of Pt(acac)2 and Co(CH3COO)2 in oleylamine at 250 degrees C. The as-made CoPt nanopolypods are ferromagnetic, are soluble in nonpolar organic solvents, and reveal a coercive field of 525 and 1200 Oe at room temperature and 5 K, respectively.     

Phase diagrams of the ternary systems Mn, Fe, Co, Ni---Si---N

Phase equilibria in the ternary systems Mn, Fe, Co, and Ni---Si---N are investigated and isothermal sections at 900°C (Fe---Si---N, Ni---Si---N), at 1000°C (Mn---Si---N, Co---Si---N) and at 1150°C (Fe---Si---N) are presented. In the system Mn---Si---N, Si₃N₄ coexists with MnSiN₂, Mn₃Si, Mn₅Si₃, MnSi, and MnSi_2−x. In the systems Fe, Co, Ni---Si---N, Si₃N₄ coexists with all binary silicides but reacts rapidly with iron above 1120 ± 10°C, and cobalt and nickel above 1170 ± 10°C to form binary silicides and nitrogen gas.     

Synthesis and magnetic properties of Gd doped EuS nanocrystals with enhanced Curie temperatures

EuS nanocrystals (NCs) were doped with Gd resulting in an enhancement of their magnetic properties. New EuS and GdS single source precursors (SSPs) were synthesized, characterized, and employed to synthesize Eu(1-x)Gd(x)S NCs by decomposition in oleylamine and trioctylphosphine at 290 °C. The doped NCs were characterized using X-ray diffraction, transmission electron microscopy, and scanning transmission electron microscopy, which support the uniform distribution of Gd dopants through electron energy loss spectroscopy (EELS) mapping. X-ray absorption spectroscopy (XAS) revealed the dopant ions in Eu(1-x)Gd(x)S NCs to be predominantly Gd(3+). NCs with a variety of doping ratios of Gd (0 ≤ x < 1) were systematically studied using vibrating sample magnetometry and the observed magnetic properties were correlated with the Gd doping levels (x) as quantified with ICP-AES. Enhancement of the Curie temperature (T(C)) was observed for samples with low Gd concentrations (x ≤ 10%) with a maximum T(C) of 29.4 K observed for NCs containing 5.3% Gd. Overall, the observed T(C), Weiss temperature (θ), and hysteretic behavior correspond directly to the doping level in Eu(1-x)Gd(x)S NCs and the trends qualitatively follow those previously reported for bulk and thin film samples.     

Formation of hollow Ni2p nanoparticles based on the nanoscale Kirkendall effect

Colloidal hollow nanoparticles (NPs) of Ni2P have been prepared by a one-pot reaction from a mixture of nickel acetate, oleylamine, trioctylphosphine (TOP), and 1-octadecene. The mechanism to the hollow structure is related to the nanoscale Kirkendall effect. The process contains two important steps. First, oleylamine-stabilized Ni NPs were formed, which can protect them from TOP etching and slow down the inward diffusion of P atoms. Second, the solid-state reaction between the Ni NPs occurred when the TOP concentration and the reaction temperature were correctly adjusted.     

Chemical synthesis, structural characterization, optical properties, and photocatalytic activity of ultrathin ZnSe nanorods

Ultrathin ZnSe nanorods in the cubic phase have been synthesized by the reaction of selenium and zinc oleate for 30 min at 240 °C. These nanorods showed an average diameter of 2.4 nm, which is much smaller than the Bohr size of bulk ZnSe. Thus, they exhibited a remarkable quantum size effect in terms of their optical properties. The formation of the ultrathin nanorods could be attributed to the oriented attachment mechanism, which was supported by the structure of the nanorods and the control experiments. The ultrathin nanorods were transferred into an aqueous solution by ligand exchange. The performance of these nanorods as a catalyst was examined, using the photodegradation of methyl orange as a model reaction. It was found that the ultrathin nanorods possessed better photocatalytic activities than conventional ones.