Showing papers on "Phosphide published in 2007"
TL;DR: In this article, a quasi-topotactic intercalation mechanism was proposed, in which lithium is inserted into monoclinic binary MnP4 to form the cubic ternary Li7MnP4 phase.
Abstract: Lithium-ion rechargeable batteries are used as portable power sources for a wide variety of electronic devices, such as cellular phones, notebook computers, and camcorders. Intensive research efforts have been made over the past decade to increase the gravimetric and volumetric energy density of lithium ion batteries. At present, graphite (372 mAhg) is used as an anode material for lithium ion batteries, but higher capacity alternatives are being actively pursued. Among the many possible alternatives, a lot of work has been devoted to Sn-based oxide, Si-based composite, transition metal oxide, metal nitride and metal phosphide systems, due to their ability to react reversibly with large amounts of Li per formula unit. Although alloy-based systems have a higher energy density, they suffer from poor capacity retention, since a large volume change occurs during charge/discharge. Among these alternatives, a concept based on the quasi-topotactic intercalation mechanism was proposed, in which lithium is inserted into monoclinic binary MnP4 to form the cubic ternary Li7MnP4 phase. [10] Since then, Li insertion/extraction in transition metal phosphides has been investigated as a possible candidate for the anode material in lithium ion batteries. In these systems, commercial red P and transition metals were used to synthesize metal phosphides, but the energy density is reduced due to the heavy transition metals employed. If phosphorus were used for electrode materials, it would have a good energy density, but little is known about its electrochemical behavior, since commercial red P has an amorphous structure with a poor bulk conductivity and poor cyclability. Phosphorus, an element of the fifth group in the periodic table, has three main allotropes: white, red, and black. Among these modifications of allotropes, black phosphorus is thermodynamically the most stable, insoluble in most solvents, practically non-flammable, and chemically the least reactive form, and exists in three known crystalline modifications (orthorhombic, rhombohedral, and simple cubic), as well as in an amorphous form. Since orthorhombic black phosphorus was obtained from white phosphorus at 200 C and 1.2 GPa, many studies designed to synthesize black phosphorus have been reported. However, the basic concept of a high temperature and high pressure being required has not been changed, and black phosphorus still remains difficult to synthesize, and has the lowest commercial value of the three forms. Considering that orthorhombic black phosphorus exhibits a layer structure similar to that of graphite, which is currently used as an anode material for Li ion batteries, we developed a simple method of transforming commercially available amorphous red phosphorus into orthorhombic black phosphorus using a high energy mechanical milling (HEMM) technique at ambient temperature and pressure. It is known that the temperature during HEMM can rise above 200 C and the pressure generated can be of the order of 6 GPa. These conditions should be sufficient to transform red P into its high-pressure allotrope, the black phosphorus phase, at ambient temperature and pressure. Figure 1a shows the color photo image, XRD pattern, and TEM electron diffraction pattern showing a diffuse ring of red P, which confirms the amorphous nature of the red P. The sample prepared by HEMM corresponds to orthorhombic black P according to the XRD data and color photo image (Fig. 1b), and was also identified by high resolution TEM electron diffraction, and by its lattice spacing. Figure 2a and 2b show the voltage profiles of red P and black P, respectively. Their electrochemical behaviors are very different from each other. The discharge and charge capacities of red P are 1692 and 67 mAhg, respectively, and it cannot be used as an anode material since its charge capacity is negligible. Although black P shows an increased charge capacity of 1279 mAhg, the first cycle efficiency is only 57%. The electrochemical performance of Si as an anode material for Li ion batteries can be much improved using Si–carbon composites. Black P also has a low electronic conductivity inherited from its characteristic as a semiconductor. The electrochemical behaviors of the black P-carbon composite during the discharge/charge reaction with Li were excellent compared with the above two cases, as shown in Figure 2c. The first discharge and charge capacities are 2010 and 1814 mAhg, respectively, and the first cycle efficiency is about 90%, which is one of the highest reported. The good coulombic efficiency of the black P–carbon composite for the C O M M U N IC A IO N
707 citations
TL;DR: This paper reports a general strategy for synthesizing transition metal phosphides, including those with 4d and 5d transition metals that have not previously been reported as unsupported nanocrystals, and utilizes preformed metal nanoparticles as templates for generating metal phosphide nanocry crystals.
Abstract: Nanocrystals of metal phosphides, which can have useful catalytic, electronic, and magnetic properties, are known to be accessible by using trioctylphosphine (TOP) as a highly reactive phosphorus source. Here we report a general strategy for synthesizing transition metal phosphides, including those with 4d and 5d transition metals that have not previously been reported as unsupported nanocrystals. Unlike previously reported methods that involve direct decomposition of organometallic precursors, our method utilizes preformed metal nanoparticles as templates for generating metal phosphide nanocrystals. Metal nanoparticles are reacted with TOP in a hot solvent (290−360 °C) to form transition metal phosphides such as Ni2P, PtP2, Rh2P, PdP2, Pd5P2, and Au2P3. Furthermore, nanostructures such as hollow spheres can be easily made using a Kirkendall-type mechanism, which utilizes metal nanoparticles as reactive templates.
402 citations
TL;DR: In this paper, a solution-phase method with bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2] as the nickel source and trioctylphosphine (TOP) as the phosphorus source in the presence of the coordinating solvent trio-cyclohexine oxide (TOPO) was used.
Abstract: Discrete, unsupported nanoparticles of Ni2P have been prepared by using a solution-phase method with bis(1,5-cyclooctadiene)nickel(0) [Ni(COD)2] as the nickel source and trioctylphosphine (TOP) as the phosphorus source in the presence of the coordinating solvent trioctylphosphine oxide (TOPO). Ni2P nanoparticles prepared at 345 °C have an average crystallite size of 10.2 ± 0.7 nm and are capped with TOP and/or TOPO coordinating agents. The surface of the Ni2P nanoparticles can be modified by washing with CHCl3 or by exchanging TOP/TOPO groups with mercaptoundecanoic acid (MUA). The surface areas of these nanoparticles are on the order of 30–70 m2 g–1. As-prepared and MUA-capped nanoparticles undergo a phase transformation at 370 °C under reducing conditions, but CHCl3-washed Ni2P nanoparticles retain the Ni2P structure. CHCl3-washed and MUA-capped nanoparticles exhibit higher HDS catalytic activity than as-prepared nanoparticles or unsupported Ni2P prepared by temperature-programmed reduction of a phosphate precursor. The surface modifications have a clear effect on the catalytic activity as well as the thermal stability of Ni2P nanoparticles under reducing conditions.
124 citations
TL;DR: In this paper, Ni 2 P nanocrystal with dendritic morphologies was synthesized via a solvothermal reaction between nickel sulfate (Ni-source) and yellow phosphorous (P-source), in a mixture solution of glycol and water.
70 citations
TL;DR: In this article, a high surface area molybdenum phosphide (MoP) was successfully synthesized by combining citric acid (CA) and temperature-programmed reduction (TPR) (CA-TPR).
Abstract: A high surface area molybdenum phosphide (MoP) was successfully synthesized by combining citric acid (CA) and temperature-programmed reduction (TPR) (CA-TPR) method. Reduction of the precursor which was modified by citric acid produced Mol? with a high surface area of 122.0 m(2) g(-1) under optimum conditions. Fourier transform infrared (FTIR) results showed that the chelating interaction between the moderate amount of citric acid and the molybdenum ion was effective in suppressing the aggregation of Mo during drying through the formation of a molybdenum citrate, which was decomposed in calcination. Reduction of the precursor from the CA-TPR method showed an obvious decrease in degree of the aggregation of the MOP particles when compared to that from the conventional TPR method. The Mol? prepared by the CA-TPR method was characterized by X-ray diffraction (XRD), N-2 adsorption-desorption, TPR, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and CO adsorption microcalorimetry. An increase in reduction temperature led to the formation of MoP crystalline and a change of morphology. The increase of surface area in the reduction process was a result of the formation of pores. The porous MoP from the CA-TPR method had a higher CO chemisorption uptake than from the conventional TPR method, indicating that the high surface area MoP possessed more active sites. The preliminary testing showed that the high surface area MoP exhibited a superior activity for hydrazine decomposition with a conversion of 85%, which was much higher than the conventional Mol? of 55%. (c) 2006 Elsevier B.V. All rights reserved.
66 citations
TL;DR: In this paper, both supported and unsupported and Al2O3-supported molybdenum phosphides (MoP) were tested as catalysts for the decomposition of hydrazine (N2H4) in comparison with previously studied Mo2N catalysts.
60 citations
TL;DR: In this paper, the Li electrochemical reactivity of amorphous and crystalline VP2, synthesized by ball-milling and by 600 °C heat treatment, respectively, was investigated.
55 citations
1 Jan 2007
TL;DR: In this article, both supported and unsupported and Al2O3-supported molybdenum phosphides (MoP) were tested as catalysts for the decomposition of hydrazine (N2H4) in comparison with previously studied Mo2N catalysts.
Abstract: Unsupported and Al2O3-supported molybdenum phosphides (MoP) were tested as catalysts for the decomposition of hydrazine (N2H4), in comparison with previously studied Mo2N catalysts. The results showed that the activity increased with MoP loading on the MoP/Al2O3 catalysts and that the supported MoP catalysts were more stable during hydrazine decomposition compared with the supported Mo2N catalysts. FTIR results indicated that N2H4 decomposed on the Mo sites on the MoP, similar to the case of Mo2N. FTIR and microcalorimetric adsorption measurements showed that NH3 was adsorbed only moderately on the MoP catalyst, giving it better catalytic stability than the Mo2N, for which strong adsorption of NH3 blocked the active sites and led to a sharp decrease in activity.
52 citations
TL;DR: In this article, it is suggested that these next-nearest neighbor contributions induce a charge transfer between the two dissimilar metals via metal-metal bonding, which modifies the Madelung potential experienced at the photoemission site.
49 citations
TL;DR: A series of MCM-41-supported nickel phosphides with an initial Ni/P atomic ratio of 0.5−2 in the oxidic precursors were prepared by an in situ reduction method and characterized by X-ray diffraction (XRD), CO chemisorption, N2 adsorption and transmission electron microscopy.
Abstract: A series of MCM-41-supported nickel phosphides with an initial Ni/P atomic ratio of 0.5−2 in the oxidic precursors were prepared by an in situ reduction method and characterized by X-ray diffraction (XRD), CO chemisorption, N2 adsorption, and transmission electron microscopy. Their catalytic performances were evaluated in the hydrodenitrogenation (HDN) of quinoline and compared with MCM-41-supported Ni−Mo sulfide. The supported nickel phosphides with initial Ni/P ratios of 1 or 1.25 exhibited much higher HDN activity than the supported Ni−Mo sulfide. XRD patterns of both high-performance phosphide catalysts revealed that the active phase was Ni2P. It is indicated that the HDN of quinoline on the MCM-41-supported nickel phosphides exclusively proceeds via a pathway, which involves fully saturated intermediates. The cleavage of the C−N bond in the decahydroquinoline is the rate-determining step in the HDN of quinoline on the supported nickel phosphides. In addition, the effects of H2S (CS2 as the precursor)...
47 citations
TL;DR: A series of γ-Al2O3-supported molybdenum phosphide catalysts containing fixed Moloading and variable P amounts (1.5−9.6 wt %) were prepared by temperature-programmed reduction (TPR) from their oxide precursors in hydrogen.
Abstract: A series of γ-Al2O3-supported molybdenum phosphide catalysts containing fixed Mo-loading (9.9 wt %) and variable P amounts (1.5−9.6 wt %) were prepared by temperature-programmed reduction (TPR) from their oxide precursors in hydrogen. The effect of the P/Mo atomic ratio on the structure of the molybdenum phosphide materials was studied by SBET, XRD, HRTEM, TPD−NH3, H2 chemisorption, XPS, and 31P- and 27Al-MAS NMR techniques. The reactions involved in the transformation of oxide precursor to Mo−phosphide were followed by TPR. Specific surface areas of samples subjected to reduction at 1123 K were rather high (210−263 m2 g-1). These catalysts were tested in the gas-phase hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 553 K and 3.4 MPa. All Mo−phosphide catalysts were more active than a molybdenum sulfide sample with the same Mo-loading. The Mo−phosphide catalysts with P/Mo ratios of 1 and 1.1 were found to be the most active among the catalysts studied. The activity drop observed for higher P-loadi...
TL;DR: In this article, thin films of Ni 3 P ca. 400nm in thickness were obtained by electrodeposition on a stainless steel substrate and subsequent heating at 500°C in an argon or vacuum atmosphere.
5 Jan 2007
TL;DR: The 2,2-Dimethylpropylidyne)phosphine is the first compound with a phosphorus-carbon triple bond stable at room temperature as mentioned in this paper, and it is more likely to react as the analog of an alkine than of a nitrile.
Abstract: (2,2-Dimethylpropylidyne)phosphine is the first compound with a phosphorus-carbon triple bond stable at room temperature. Since the electronegativities of phosphorus (2.2) and carbon (2.5) differ substantially from the value of nitrogen (3.0), the compound is more likely to react as the analog of an alkine than of a nitrile. Thus far, the reactivity of the phosphine towards transition metal complexes with the metals in low oxidation states and towards organic 1,3-dipolar or Diels-Alder reagents, has been studied. With halides of main group and subgroup elements numerous insertion reactions have been observed; from the addition of lithium bis(trimethylsilyl)phosphide' 2tetrahydrofuran (THF) in 1,2-dimethoxethane (DME), lithium 3,5-di-tert-butyl-1, 2, 4-triphospholid' 3DME can be obtained.
TL;DR: In this paper, the phase composition and morphology of hollow spheres have been characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscope (SEM).
TL;DR: In this article, the use of methane as a reductant in the synthesis of binary transition metal phosphides was investigated and it was shown that reduction using methane could be a viable route to the preparation of high surface area phosphide catalysts.
TL;DR: In this article, a solution-mediated reaction of pre-formed metals with trioctylphosphine (TOP) at temperatures below 370 °C was proposed to synthesize a wide range of transition-metal and post-transition-metal phosphides.
Abstract: Metal phosphides can have important properties such as superconductivity, magnetoresistance, magnetocaloric behavior, catalytic activity, and lithium intercalation capacity, which make them useful for a variety of technological applications. Bulk metal phosphides usually require high temperatures and harsh reaction conditions to form, and metal phosphide nanocrystals can also be challenging to synthesize. Here we elaborate on a recently developed alternative approach for synthesizing metal phosphides, which involves the solution-mediated reaction of pre-formed metals with trioctylphosphine (TOP) at temperatures below 370 °C. This chemical conversion strategy is shown to be general and highly versatile, successfully forming a wide range of transition-metal and post-transition-metal phosphides using a range of both bulk and nanoscale metals as precursors. Metal nanocrystals, bulk powders, foils, wires, thin films, lithographically patterned substrates, and supported nanocrystals can all be converted to meta...
TL;DR: In this paper, the wetting of electroless nickel by the eutectic SnAgCu solder alloy was investigated in the as-deposited and annealed conditions.
Abstract: Wetting of electroless nickel by the eutectic SnAgCu solder alloy was investigated in the as-deposited and annealed conditions. In the as-deposited state, P content in the nickel had a minimal effect on the solderability of the electroless nickel. Upon annealing, numerous nickel phosphide particles precipitated out of the electroless nickel with a high-P content. The presence of these phosphide precipitates reduced the solderability of the electroless nickel both in terms of the wetting force and wetting kinetics. While weakening in the wetting force is related to the inferior contact condition, the slower wetting kinetics is explained in terms of the reduction in the dissolution rate of the electroless nickel from non-soluble phosphide particles. (c) 2007 Elsevier B.V. All rights reserved.
TL;DR: In this article, the indium phosphide (InP) was used to synthesize high-quality epitaxial nanometer-scale structures on non-single crystalline semiconductor surfaces formed on amorphous substrates.
Abstract: We demonstrated a route to synthesize high-quality epitaxial nanometer-scale structures on non-single crystalline semiconductor surfaces formed on amorphous substrates. We chose indium phosphide (InP) for a material of nanometer-scale structures and various hydrogenated silicon (Si:H) films for non-single crystalline semiconductor surfaces. With the presence of gold nanoparticles, the InP grew into nearly one-dimensional nanometer-scale structures, nanoneedles, with a wide base on one end and a sharp tip on the other end. The Si:H films and the prepared InP nanoneedles were studied in terms of their chemical, structural and optical properties.
TL;DR: In this article, the authors focus on gold phospide complexes derived from secondary phosphines, primary phosphines (PR2H), primary phosphine (PRH2), primary diphosphines (PH2(CH2)nPH2) or from PH3.
Abstract: The vast majority of gold complexes with five group-element donor ligands contain tertiary phosphines, although compounds with amine, arsine or stibine ligands are also known. Although phosphide ligands, which are formed by deprotonation of non-tertiary phosphines, are closely related to the former, they have been employed to a lesser extent, mainly due to their lower stability. Thus, the chemistry of phosphido-bridged derivatives of the main group elements1-3 or transition metals4-6 has been a matter of interest for various research groups in the last few years. While there are many phosphido complexes with metals, mainly of groups 67-12 or 10,13-20 the chemistry of gold derivatives has experienced less progress in this field of research in spite of the possible catalytic behaviour of diand polynuclear phosphido-bridged compounds.21 This is an interesting field of research, because the substitution of one or more protons by metal atoms allows the synthesis of homoor heteropolynuclear compounds in which the presence of a small bridging atom, such as phosphorus, may give rise to intermetallic contacts, which, as is known, are often responsible for surprising and interesting optical properties, such as luminescence, area with an increasing importance in the last years. This review focuses on gold phospide complexes derived from secondary phosphines (PR2H), primary phosphines (PRH2), primary diphosphines (PH2(CH2)nPH2) or from PH3. The moieties derived from all these complexes usually act as bridging ligands between more than one gold centre or between gold and other transition metal centres.
Patent•
11 May 2007
TL;DR: In this paper, a non carrier vanadium phosphide oxidation accelerant was proposed, which is made of pyrophosphoric acid vanadyl with small amount of phosphoric acid sulfate and amorphous substance.
Abstract: The invention relates to a non carrier vanadium phosphide oxidation accelerant, which is made of pyrophosphoric acid vanadyl with small amount of phosphoric acid sulfate and amorphous substance The atom ratio of phosphor and vanadium is 1 2, ratio surface area being 10-38m2/g As positive butagas to make reaction catalyst, it works within 360-400degC typical temperature interval, single stroke conversion rate being 41-99%, optional rate being 60-83%, with the max recovering rate reaching 70 2% This invention has publicized its making formula
TL;DR: In this article, the ion chemistry of tris(trifluoromethyl)phosphine has been investigated in a long cylindrical ion cyclotron resonance (ICR) cell.
Patent•
19 Sep 2007
TL;DR: In this paper, a method for chloro arene catalyzing hydrogenation and dechlorination is described, which is based on filling load nickel phosphide catalyst in the fixing bed reactor, airing the hydrogen gas into the reactor with an airspeed of 10-10000 h-1 and airing chlorobenzene, dichlorobenzenes, trichlorobenene or trich chlorobensene with an annealing rate of 0.01-10h-1 at normal atmosphere.
Abstract: The invention relates to a method for chloro arene catalyzing hydrogenation and dechlorination. The processing is as follows: filling load nickel phosphide catalyst in the fixing bed reactor; airing the hydrogen gas into the reactor with an airspeed of 10-10000 h-1 and airing chlorobenzene, dichlorobenzene or trichlorobenzene with an airspeed of 0.01-10 h-1 at normal atmosphere and in 200-400 DEG C for catalyzing hydrogenation and dechlorination. Said load nickel phosphide catalyst has silicon dioxide, alumina, HY molecule screen, zirconia, titanic anhydride or active carbon as carrier. The active component nickel exists in a phase of Ni2P, Ni12P5 or Ni2P. The nickel mass content in the catalyst is 5-25%. The advantages of the invention are that the catalyst has a good reacting activity and stability of hydrogenation and dechlorination and it achieves continuous application.
Patent•
9 May 2007
TL;DR: A nano-class nickel phosphide catalyst (Ni12P5) with low environmental pollution and low damage to human body is prepared through dissolving NiSO4.6H2O and NaH2PO4 in deionized water, adding oil phase and surfactant, stirring, heating to 140-160 deg.C, and reacting for at least 8 hr.
Abstract: A nano-class nickel phosphide catalyst (Ni12P5) with low environmental pollution and low damage to human body is prepared through dissolving NiSO4.6H2O and NaH2PO4 in deionized water, adding oil phase and surfactant, stirring, heating to 140-160 deg.C, and reacting for at least 8 hr.
TL;DR: In this article, the authors used the concept of topological charge stabilization to predict the relative stabilities of the cage structures in tris(chlorodimethylsilyl)methylsilane (1) and 1,1,2,2-tetrakis-1, 2-dimethyldisilane (2) with sodium/potassium arsenide Na3As/K3As.
Abstract: The reaction of tris(chlorodimethylsilyl)methylsilane (1) and 1,1,2,2-tetrakis(chlorodimethylsilyl)-1,2-dimethyldisilane (2) with sodium/potassium arsenide Na3As/K3As afforded decamethyl-2,3,5,6,7-pentasila-1,4-diarsabicyclo[2.2.1]heptane (3)and dodecamethyl-2,3,4,6,7,8,9-heptasila-1,5-diarsatricyclo[3.3.1.03,7]nonane (4). Compounds 3 and 4 were isolated from the reaction mixture by fractional crystallization and structurally characterized by single-crystal X-ray crystallography. The reaction of 1 with an excess amount of sodium/potassium phosphide (Na3P/K3P) afforded the cage-shaped anionsodium hexamethyl-2,4,6,7-tetrasila-1-phosphanido-3,5-diphosphabicyclo[3.2.1]octane (5), which reacts with chlorotrimethylsilane to form trimethylsilyl-substituted derivative 6. The molecular structures of 5 and 6 were established by X-ray crystallography. Cages 3–6 were also characterized by 29Si- and 31P NMR spectroscopy. Owing to indirect spin–spin coupling between the 29Si and 31P nuclei, the resonances of the 29Si nuclei in the spectra of 5 and 6 are only of first order approximately. To account for the observed preferences of the cage structures in these reactions, extensive B3LYP/6-31G* quantum chemical calculations of relative energies of bicyclo[2.2.2] and bicyclo[3.2.1] isomers of Si8H14, PSi7H13, P2Si6H12 and P3Si5H11 were conducted. On the basis of the computed charge distributions, the concept of topological charge stabilization was used to predict the relative stabilities. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
TL;DR: In this paper, a double mercury silver phosphide iodide Hg12Ag41P88I41 (1) was synthesized and its crystal structure was established and the characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P113−, which have been previously found in alkali metal compounds only.
Abstract: New double mercury silver phosphide iodide Hg12Ag41P88I41 (1) was synthesized and its crystal structure was established. Compound 1 crystallizes in the cubic system. The characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P113−, which have been previously found in alkali metal compounds only. The well-ordered P113− clusters form a system of polyhedra, which encapsulate various disordered α-AgI-type fragments.
TL;DR: In this paper, metal nanoparticles are reacted with trioctylphosphine (TOP) in a hot solvent (290−360 °C) to form transition metal phosphides such as Ni2P, PtP2, Rh2P and Au2P3.
Abstract: Nanocrystals of metal phosphides, which can have useful catalytic, electronic, and magnetic properties, are known to be accessible by using trioctylphosphine (TOP) as a highly reactive phosphorus source. Here we report a general strategy for synthesizing transition metal phosphides, including those with 4d and 5d transition metals that have not previously been reported as unsupported nanocrystals. Unlike previously reported methods that involve direct decomposition of organometallic precursors, our method utilizes preformed metal nanoparticles as templates for generating metal phosphide nanocrystals. Metal nanoparticles are reacted with TOP in a hot solvent (290−360 °C) to form transition metal phosphides such as Ni2P, PtP2, Rh2P, PdP2, Pd5P2, and Au2P3. Furthermore, nanostructures such as hollow spheres can be easily made using a Kirkendall-type mechanism, which utilizes metal nanoparticles as reactive templates.
TL;DR: In this article, a series of molybdenum phosphide catalysts from initial Mo/P molar ratios ranging from 0.6 to 2.6 were used for selective hydrogenation of acetonitrile.
TL;DR: In this paper, single crystals of ScPtP (orthorhombic, a = 6.437(1), b = 4.532 (1), c = 7.864(2) Å ) were investigated by single crystal X-ray diffraction.
Abstract: Single crystals of ScPtP (orthorhombic, a = 6.437(1), b = 4.291(1), c = 7.550(2) Å ) were grown by reaction of the elements in molten lead (1000 °C), whereas LaPtP (orthorhombic, a = 7.268(1), b = 4.532(1), c = 7.864(2) Å ) was prepared by heating mixtures of the elements at 900 °C. Both phosphides were investigated by single crystal X-ray diffraction. Their crystal structures belong to the TiNiSi-type (Pnma; Z = 4), but the positions of the Ni and Si atoms are exchanged. Therefore the Pt atoms are located in the centers of trigonal prisms and the P atoms are coordinated by four Pt atoms in the shape of distorted tetrahedra.
TL;DR: In this article, a quasi-topotactic intercalation mechanism was proposed, in which lithium is inserted into monoclinic binary MnP4 to form the cubic ternary Li7MnP4 phase.
Abstract: Lithium-ion rechargeable batteries are used as portable power sources for a wide variety of electronic devices, such as cellular phones, notebook computers, and camcorders. Intensive research efforts have been made over the past decade to increase the gravimetric and volumetric energy density of lithium ion batteries. At present, graphite (372 mAhg) is used as an anode material for lithium ion batteries, but higher capacity alternatives are being actively pursued. Among the many possible alternatives, a lot of work has been devoted to Sn-based oxide, Si-based composite, transition metal oxide, metal nitride and metal phosphide systems, due to their ability to react reversibly with large amounts of Li per formula unit. Although alloy-based systems have a higher energy density, they suffer from poor capacity retention, since a large volume change occurs during charge/discharge. Among these alternatives, a concept based on the quasi-topotactic intercalation mechanism was proposed, in which lithium is inserted into monoclinic binary MnP4 to form the cubic ternary Li7MnP4 phase. [10] Since then, Li insertion/extraction in transition metal phosphides has been investigated as a possible candidate for the anode material in lithium ion batteries. In these systems, commercial red P and transition metals were used to synthesize metal phosphides, but the energy density is reduced due to the heavy transition metals employed. If phosphorus were used for electrode materials, it would have a good energy density, but little is known about its electrochemical behavior, since commercial red P has an amorphous structure with a poor bulk conductivity and poor cyclability. Phosphorus, an element of the fifth group in the periodic table, has three main allotropes: white, red, and black. Among these modifications of allotropes, black phosphorus is thermodynamically the most stable, insoluble in most solvents, practically non-flammable, and chemically the least reactive form, and exists in three known crystalline modifications (orthorhombic, rhombohedral, and simple cubic), as well as in an amorphous form. Since orthorhombic black phosphorus was obtained from white phosphorus at 200 C and 1.2 GPa, many studies designed to synthesize black phosphorus have been reported. However, the basic concept of a high temperature and high pressure being required has not been changed, and black phosphorus still remains difficult to synthesize, and has the lowest commercial value of the three forms. Considering that orthorhombic black phosphorus exhibits a layer structure similar to that of graphite, which is currently used as an anode material for Li ion batteries, we developed a simple method of transforming commercially available amorphous red phosphorus into orthorhombic black phosphorus using a high energy mechanical milling (HEMM) technique at ambient temperature and pressure. It is known that the temperature during HEMM can rise above 200 C and the pressure generated can be of the order of 6 GPa. These conditions should be sufficient to transform red P into its high-pressure allotrope, the black phosphorus phase, at ambient temperature and pressure. Figure 1a shows the color photo image, XRD pattern, and TEM electron diffraction pattern showing a diffuse ring of red P, which confirms the amorphous nature of the red P. The sample prepared by HEMM corresponds to orthorhombic black P according to the XRD data and color photo image (Fig. 1b), and was also identified by high resolution TEM electron diffraction, and by its lattice spacing. Figure 2a and 2b show the voltage profiles of red P and black P, respectively. Their electrochemical behaviors are very different from each other. The discharge and charge capacities of red P are 1692 and 67 mAhg, respectively, and it cannot be used as an anode material since its charge capacity is negligible. Although black P shows an increased charge capacity of 1279 mAhg, the first cycle efficiency is only 57%. The electrochemical performance of Si as an anode material for Li ion batteries can be much improved using Si–carbon composites. Black P also has a low electronic conductivity inherited from its characteristic as a semiconductor. The electrochemical behaviors of the black P-carbon composite during the discharge/charge reaction with Li were excellent compared with the above two cases, as shown in Figure 2c. The first discharge and charge capacities are 2010 and 1814 mAhg, respectively, and the first cycle efficiency is about 90%, which is one of the highest reported. The good coulombic efficiency of the black P–carbon composite for the C O M M U N IC A IO N