SI22623A - Procedure for synthesis of quasi one-dimensional structures of dichalcogenides and transition metal oxides - Google Patents

Abstract

The subject of invention is a procedure for synthesis of quasi one-dimensional structures, i.e. nanowires, microwires and tapes of metal oxides of transition metals and quasi one-dimensional structures of transition metal dichalcogenides composed of fine crystallites of transition metal dichalcogenides. The reaction is run by the chemical reaction of quasi one-dimensional materials consisting of nanowires with a diameter below one micrometre, described with the formula M6CyHz, where y+z is greater than 8.2 and smaller or equal to 10, where M is a transition metal (Mo,W, Ta, Nb), C is a chalcogen (S, Se, Te)and H is a halogen (I), where the said quasi one- dimensional material is first heated in the air or otherwise in the presence of oxygen at an elevated temperature and is transformed into quasi one-dimensional metal oxides of transition metals, described with the formula MOx, where x is greater than 0.3 and smaller or equal to 3, where M is a transition metal (Mo,W, Ta, Nb) and O is oxygen; then a chemical transformation of the said quasi one-dimensional metal oxides follows in a quartz tube with a gas comprising an active reagent containing a chalcogen; the transformation takes place at an elevated temperature at which the active regent, containing a chalcogenide, exists in the vapour phase.

Description

Process for the synthesis of quasi-one-dimensional structures of dihalcogenides and transition metal oxides

Subject of the invention, the field of technology to which the invention belongs

The subject of the invention is a process for the synthesis of quasi one-dimensional structures, that is, nanowires, microspheres and strips of transition metal metal oxides and quasi-one-dimensional structures of transition metal dichalcogenides composed of tiny crystallites of transition metal dichalcogenides. The invention relates to the field of inorganic chemistry and chemistry of transition metal dichalcogenides. The invention relates to the synthesis of quasi one-dimensional structures of transition metal dichalcogenides composed of fine crystallites of transition metal dichalcogenides by a method of converting quasi-one-dimensional compounds with a sub-micron cross section of nanowires described by the formula M6C _y H _z , 8.2 <y + z <10, where M <6 + y <z <10 metal (Mo, W, Ta, Nb), C is chalcogen (sulfur (S), selenium (Se), tellurium (Te)); H is halogen (iodine (I)) by heating in the presence of oxygen and converting the resulting quasi-one-dimensional transition metal metal oxides in the presence of at least one chalcogen-containing reagent. This procedure enables the synthesis of quasi-one-dimensional structures of transition metal dichalcogenides composed of tiny crystallites of transition metal dichalcogenides, and the synthesis of quasi-one-dimensional structures of transition metal metal oxides.

The state of the art

Many transition metal dichalcogenides and transition metal oxides have considerable technological applications. Thus, e.g. M0S2, one of the transition metal dichalcogenides, is used in catalysis, for the desulphurisation of petroleum, and is also classified as a solid lubricant for use in vacuum and space technology and other applications where fluid use is restricted. Transition metal oxides are used inter alia as sensors of various gases, catalyst carriers and catalysts, and as cathode material in batteries.

-2 Nanotubes, fullerene-like nanostructures, nanowires, nanotubes and nanocumulons of transition metal dichalcogenides are interesting because of their special crystallographic morphology and interesting physical properties. M0S2 nanostructures are thus potentially of interest for use in a wide range of applications ranging from nanoelectronics, photocatalysis, nanotribology, solar cells, enzymes and hydrogen storage. The catalytic activity in hydrodesulfurization catalysis (HDS code) depends not only on the type of edges in the nanostructures and the coverage of sulfur, but also on the size of the nanostructures. The best catalytic capacity for HDS is expected for nanostructures with weak interaction with the carrier, type II, and with size where structural changes occur - described in Lauritsen V. J, Kibsgaard J., Helveg S., Topsoe H., Clausen SB, Laegsgaard E., Flemming B, B., Nature Nanotechnology, 58, Vol 2, Jan 2007. One of the widely used methods for the synthesis of transition metal dichalcogenide nanostructures is through precursor metal oxides of transition metals. The first inorganic transition metal chalcogenide nanotubes were synthesized using the metal oxide sulfurization method - described in Tenne R. et al, US Patent Base, US-P6,217,843 (Appl. No. 308663). The syntheses of fullerene-like MS2 nanostructures (M = Mo, W) are based on the sulfurisation of MO ₃ (M = Mo, W) in a reducing atmosphere at elevated temperatures (about 850 ° C). This technique is described in the following publications- described in Tenne, R; Margulis, L.; Genut, M.; Hodes, G. Nature 1992, 360, 444, Margulis, L.; Salitra, G.; Tenne, R.; Talianker, M. Nature, 365,113,1993; Hershfinlkel, M.; Gheber, LA; Volterra, V; Hutchison, JL; Margulis, L.; Tenne, RJ Am. Chem. Soc., 116, 1914, 1994. Feldman, Y.; Wasserman, E.; Srolovitz, DJ; Tenne, R. Science, 267, 222, 1995, in Feldman, Y.; Frey, GL; Homyonfer, M.; Lyakhovitskaya, V.; Margulis, L.; Cohen, H.; Hodes, G.; Hutchison, JL; Tenne, R. J Am. Chem. Soc., 118, 5362, 1996, Rothschild, A.; Frey, GL; Homyonfer, M.; Tenne, R.; Rappaport, M. Mat. Really. Innovat., 3, 145, 1999. Using a special apparatus under certain temperature conditions, a near-pure phase of fullerene-like nanoparticles can be obtained. - described in Tenne R.; (St Rehovot, IL); Feldman, Y.; (Ashdod, IL); Zak, A.; (Rehovot, IL); Rosentsveig, R.; (Rehovot, IL) United States Patent Application 20040018306. Several different methods have been used for the synthesis of nanowires and nanotubes of transition metal dichalcogenides via precursor oxides. With different acids, precursor molecules of ammonium heptamolybdate tetrahydrate can be converted under hydrothermal conditions at 140 ° C to 200 ° C into molybdenum trioxide with the morphology of nanotubes and nanopales. Using H2S / H2 at 600 C °, the oxides can be converted to M0S2 nanoparticles with conserved

-3 oxide morphology- described in Xiong Wen Lou and Hua Chun Zeng Chem. Mater., 14, 4781-4789, 2002. With a two-step synthesis-hydrothermal-gas reaction, they were able to prepare nanostructured material M0S2-M002, where MoS ₂ crystallites are on the surface of MoO ₂ . mostly in the form of up to 30 nm nanowires Measurements on the nanostructures indicate the increase in catalytic activity and selectivity described in Camacho-Bragado GA, Elechiguerra JL, Olivas A, Fuentes S, Galvan D, Yacaman MJ Jour. Catal. 234 (1): 182-190 AUG 15 2005. Polycrystalline MoS2 nano and micro-strips were synthesized by a two-step electrochemical / chemical synthesis method, where the precursor of MoO ₂ initially oriented in the electric field on the surface of the pyrolytic graphite. These nanowires were converted to MoS ₂ with H ₂ S at 900 ° C. The resulting bands had lengths up to lmm and consisted of parallel MoS ₂ particles with a structure similar to a conventional layered crystal - described in Li Q, Newberg JT, Walter EC, Hemminger JC, Penner RM ΝΑΝΟ LETTERS 4 (2): 277-281 FEB 2004. Nanoparticles with a diameter of about 20 nm MoS ₂ are formed at 24 μm hydrothermal method of aqueous solution (NH4) (6) Mo ₇ O ₂ 4 4H (2) O, C ₂ H ₄ NS and Na ₂ S ₂ O4 at 190 ° C. and the resulting product was then heated in further nitrogen - as described in Ota JR, Srivastava SK JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 6 (1): 168-174 JAN 2006.

ΜοΟβ nanoparticles with orthorhombic structure and about 10 nm in diameter were synthesized by electron transfer. These nanowires exhibit greater sensitivity to ammonia than conventional sol-gel sensoi - described in Gouma P (Gouma, P.), Bishop A (Bishop, A.), Yer KK (Yer, KK) RARE METAL MATERIALS AND ENGINEERING 35: 295- 298 Suppl. 3, DEC 2006. Oriented MOO3 nanowires of similar lengths and diameters were prepared in a two-step synthesis with temperature vaporization and oxidation described in Zhou J, Deng SZ, Xu NS, Chen J, She JC APPLIED PHYSICS LETTERS 83 (13): 2653-2655 SEP 29 2003. Macroscopic amounts of MoO ₃ nanostructures with different morphologies, such as nanotubes, nanotubes and nanoliths, have been chemically synthesized using H ₂ O ₂ and molybdenum. Li GC (Li, Guicun) - Described in Jiang L (Jiang, Li), Pang SP (Pang, Shuping), Peng HR (Peng, Hongrui), Zhang ZK (Zhang, Zhikun) JOURNAL OF PHYSICAL CHEMISTRY B 110 (48) : Anisotropic crystalline alpha MoO ₃ nanostructures were synthesized by decomposition and condensation of peroxymolybdic acid under hydrothermal conditions. The resulting nanostructures have a width of 200 to 300 nm, a thickness of 60 to 90 nm and a length of up to 10 micrometers. - described in Fang

-4L (Fang, Liang), Shu YY (Shu, Yuying), Wang AQ (Wang, Aiqin), Zhang T (Zhang, Tao) JOURNAL OF PHYSICAL CHEMISTRY C 111 (6): 2401-2408 FEB 15, 2007 Molybdenum crystals of the oxide were synthesized by acid decomposition of sodium molybdate under hydrothermal conditions. Under synthesis conditions, a well-oriented phase consisting of oriented crystallites along the direction up to several centimeters long can be obtained. This material is also useful as a starting material for molybdenum chalcogenides. - Described in Camacho-Bragado GA, Jose-Yacaman M APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING 82 (1): 1922 JAN 2006.

For use in catalysis, gas sensors, and elsewhere, where particle size and large active surface area are important, the form of transition metal dichalcogenides, e.g. M0S2 particles with a large active surface are simultaneously connected to one another in structures which would at the same time allow their easy removal from the liquid, desirable. It would also be a useful form of transition metal oxides of several millimeters in length, which are very difficult to synthesize with current synthesis techniques.

Several different techniques and pathways are known for the synthesis of quasi-one-dimensional structures (nanowires, microbes, and bands) of transition metal dichalcogenides composed of transition metal dichalcogenide crystallites and quasi-one-dimensional metal oxide structures of transition metals, but so far no method has been described for the synthesis of macroscopic amounts quasi-one-dimensional structures of transition metal dichalcogenides and transition metal oxides by chemical reaction of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M ₆ C _y H _z , 8.2 <y + z <10, where M is a transition metal ( Mo, W, Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I).

The object and object of the invention

The object and object of the invention is to synthesize quasi one-dimensional structures of transition metal dichalcogenides composed of interconnected fine crystallites of transition metal dichalcogenides and to synthesize quasi-one-dimensional structures of transition metal oxides.

-5Troubleshooting

According to the invention, the problem is solved by the method of synthesis of macroscopic quantities of quasi one-dimensional structures of transition metal dichalcogenides composed of small crystallites of transition metal dichalcogenides and synthesis of quasi-one-dimensional structures of transition metal oxides according to independent claims.

Description of the invention

The invention will be described by way of example and drawings. Pictures show:

FIG. 1: Schematic illustration of an embodiment of the conversion of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M ^ SiL to quasi-one-dimensional molybdenum oxides by heating in air in a zone furnace.

FIG. 2: Schematic illustration of an embodiment of sulfurization of quasi one-dimensional structures of molybdenum oxides in a zone gas furnace 1 consisting of argon, H ₂ S and H ₂ .

FIG. 3 Image of the resulting quasi-one-dimensional structures of transition metal oxides taken with a field emission microscope at field emission.

FIG. 4: Image of the resulting quasi-one-dimensional structures of transition metal oxides, taken with a field electron microscope on field emission.

FIG. 5: Electron microscopic image of a single nanowire taken with a field emission electron microscope.

FIG. 6: The electron deflection associated with Figure 4 demonstrating that the oxide phase MO5O14 is formed.

FIG. 7: Electron microscopic image taken with a field emission microscope on a field emission shows one nanowire after sulfurization.

FIG. Fig. 8: The electronic deflection of Figure 5, which proves that the material is completely converted to MoS ?.

-6Chemical conversion described in the embodiment is two-stage - first, the heating of the nanowires in air results in their conversion to metal oxides, and in the second stage, the conversion of these metal oxides formed from nanowires to the transition metal dichalcogenides.

The technical problem according to the invention is solved by chemical conversion of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M ₆ C _y H _z , 8.2 <y + z <10, where M is a transition metal (Mo, W , Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I). Chemical conversion of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M ₆ C _y H _z , 8.2 <y + z <10, where M is a transition metal (Mo, W, Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I), made in two stages, first in the stage of heating in the presence of oxygen, resulting in the transformation of nanowires into quasi-one-dimensional transition metal oxides, followed by the process of converting the formed oxides into transition metal dichalcogenides. The starting material in the form of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M6C _y H _z , 8.2 <y + z <10 is first heated in air, or in the presence of oxygen, at temperatures above 200 ° C and below 1800 ° C, preferably above 300 ° C and below 1800 ° C, as shown in Fig. 1. In this way, the quasi-one-dimensional structures of the transition metal oxides described by the formula MO _X are formed, 0.3 <x <3 where M is a transition metal (Mo, W, Ta, Nb).

The chemical conversion of quasi-one-dimensional oxides to the transition metal dichalcogenides takes place with the help of a chalcogen-containing active reagent, preferably H2S. A chemical reaction with an active reagent containing chalcogen results in the replacement of oxygen bound to the transition metal with chalcogen. The chemical conversion of the transition metal oxides is, in an embodiment, in a quartz tube with gas containing 98% by volume of argon as carrier gas, one volume percentage of H2 and one volume percentage of H2S as active reagent containing chalcogen. The reaction is carried out in an oven under conditions in which the active reagent containing the chalcogen is in the vapor phase, preferably at temperatures above 300 ° C, as shown schematically in Figure 2.

When converting quasi-one-dimensional materials made up of nanowires with a diameter of less than one micrometer according to the two-step process described, halogen replacement occurs, e.g.

-7 iodine with chalcogen, e.g. sulfur, and transformations in quasi one-dimensional structures of transition metal dichalcogenides composed of tiny crystallites of transition metal dichalcogenides.

The process for the synthesis of quasi-one-dimensional structures of transition metal metal oxides and quasi-one-dimensional structures of transition metal dichalcogenides composed of tiny crystallites of transition metal dichalcogenides is characterized in that the synthesis is carried out by chemical reaction of quasi-one-dimensional materials composed of sub-nanometers with nanometers with the formula M6C _y H _z , 8.2 <y + z <10, where M is a transition metal (Mo, W, Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I), wherein said quasi-one-dimensional materials are first heated in air or in the presence of oxygen at elevated temperature and converted into quasi-one-dimensional transition metal oxides described by the formula MO _X , 0.3 <x <3, where M transition metal (Mo, W, Ta, Nb), O is oxygen. Said quasi-one-dimensional materials are heated in the presence of oxygen at temperatures above 200 ° C and below 1800 ° C, preferably at temperatures above 300 ° C and below 1800 ° C. This is followed by the chemical conversion of the said quasi-one-dimensional metal oxides into a quartz tube with a gas containing an active reagent containing chalcogen. The chemical conversion of quasi-one-dimensional metal oxides into quasi-one-dimensional dihalcogenides of transition metals is carried out with a gas containing an active reagent containing chalcogen, the gas preferably containing 98% by volume of carrier gas, preferably argon, preferably one volume percent H ₂ and preferably one volume percent H ₂ S. The said chemical conversion takes place under conditions in which the active reagent containing the chalcogen in the vapor phase is preferably at temperatures above 300 ° C.

It is therefore a synthetic process for preparing oxides from basic nanowires and a synthetic procedure for nanowires of transition metal dichalcogenides composed of crystallites of transition metals from basic nanowires via oxides. The material of the transition metal dichalcogenides obtained by the process according to the invention is characterized in that they are in the form of quasi-one-dimensional transition metal dichalcogenides, i.e. nano, micro-wires and strips of transition metal dichalcogenides composed of tiny crystallites of transition metal dichalcogenides.

-8Example case

An exemplary example describes the synthesis of a quasi-one-dimensional structure of transition metal dichalcogenides by chemical conversion of quasi-one-dimensional materials composed of nanowires with a diameter below one micrometer described by the formula M ₆ C _y H _z , 8.2 <y + z <10, where M is a transition metal (Mo , W, Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I).

Quartz boat 1 weighed 50 mg of Mo6S ₂ l8 nanowires, which were synthesized directly from the elements as described in EP 1 541 528. Boat 1 with material 2 consisting of bundles of MogS ₂ l8 nanowires was placed in quartz tube 3 1000 mm long and 32 mm in diameter in a one-furnace 4 heated to 380 ° C. The material was heated at this temperature in air for two hours. Quartz tube 3 had a water-cooled trap 5 installed on one side. Trap 5 was used to collect the released iodine 7, while allowing air to access material 2 in boat 1. The schematic of the heating flow is shown in Figure 1. The mass of material generated. 8, consisting of quasi-one-dimensional structures of transition metal metal oxides, that is, nanowires, microspheres, and bands, was 27 mg.

Boat 1 with material 8, that is, with the resulting quasi-one-dimensional oxides of transition metals, was placed in a quartz tube 9 with a diameter of 34 mm, a wall thickness of 2 mm and a length of 1000 mm, closed at one end and equipped with a sash, which allowed the closure of tube 9 after the filing of boat 1 with material 8 and the simultaneous inlet 10 of gas or argon into the quartz tube 9. The quartz tube 9 also had a quartz outlet 11 for the gas outlet as shown in Figure 2.

The gas consisted of 98 volume percent argon, one volume percent H ₂ S and one volume percent H ₂ . First, the closed quartz tube 9 was blown through argon gas for 20 minutes and then for 15 minutes with gas. The flow of gas and argon was 40 cm ³ per minute. Quartz tube 9 was carefully inserted into a heated one-zone furnace 12, with constant blowing through gas flowing through inlet 10. The furnace temperature of boat 1 with material 8 was 860 ° C, as measured by thermocouple. After two hours of gas purging at an oven temperature of 860 ° C, quartz tube 9 was removed from the zone furnace 12.

-9 Quartz tube 9 was then left at room temperature for half an hour to cool. Throughout the whole process gas was purged through inlet 10. After half an hour, when the quartz tube 9 had cooled to a temperature below 50 ° C, the gas flow was closed and the boat 1 with the quasi-one-dimensional MoS ₂ material formed was taken from the quartz tubes 9. The weight of the quasi-one-dimensional MoS ₂ material was 30 mg. The oxidation and sulfarization phases were examined in several ways, as shown in Figures 3 to 8.

As Figure 3 shows by scanning electron microscopy (SEM). The resulting quasi-one-dimensional structures of transition metal oxides imaged by a transmission electron microscope on a field emission of Jeol 2010 F. are visible.

Figures 4, 5 and 6 are taken by TEM.

Figure 4 is a representation of the resulting quasi-one-dimensional structures of transition metal oxides and is taken with a field electron microscope on a field emission FE-SEM, Supra 35 VP, Carl Zeiss.

Figure 5 is an electron microscopic image of a single nanowire taken with a transmission electron microscope on a field emission of Jeol 2010 F and shows the polycrystalline structure and tiny crystallites growing perpendicular to the fiber direction.

Figure 6 shows the associated electronic deflection to Figure 4, proving that the oxide phase of MO5O14 is formed. Figure 6 is taken in such a way that the axis in the crystal is parallel to the electron beam.

Figure 7 is an electron microscopic image taken with a transmission electron microscope on a field emission of Jeol 2010 F and shows one nanowire after sulfurization. A polycrystalline structure is visible.

Figure 8 shows an electronic deflection of Figure 5, which proves that the material has been completely converted to MoS ₂ . It is evident from the variable intensity of the individual rings that the crystallites are not completely randomly oriented, but an orientation order is partially present between them.

Claims (4)

A method for the synthesis of quasi-one-dimensional structures of transition metal metal oxides and quasi-one-dimensional structures of transition metal dichalcogenides composed of fine crystallites of transition metal dichalcogenides, characterized in that the synthesis is carried out by chemical reaction of quasi-one-dimensional materials composed of nanometers with nanometers described by the formula M6C _y H _z , 8.2 <y + z <10, where M is a transition metal (Mo, W, Ta, Nb), C is chalcogen (S, Se, Te); H is halogen (I), wherein said quasi-one-dimensional material is first heated in air or otherwise in the presence of oxygen at elevated temperature and converted into quasi-one-dimensional transition metal oxides described by the formula MO _X , 0.3 <x <3, where M is a transition metal (Mo, W, Ta, Nb), O is oxygen .; this is followed by the chemical conversion of said quasi-one-dimensional metal oxides into a quartz tube with a gas containing an active reagent containing chalcogen, the process being carried out at elevated temperature. Process according to claim 1, characterized in that said quasi-one-dimensional materials are heated in the presence of oxygen at temperatures above 200 ° C and below 1800 ° C, preferably at temperatures above 300 ° C and below 1800 ° C. Process according to claim 1, characterized in that the chemical conversion of the quasi-one-dimensional metal oxides into the quasi-one-dimensional dihalcogenides of the transition metals is carried out with a gas containing an active reagent containing chalcogen, the gas preferably containing 98% by volume of carrier gas, preferably argon , preferably one volume percent H ₂ and preferably one volume percent H ₂ S. Process according to claim 1, characterized in that said chemical conversion takes place at elevated temperature under conditions in which the active reagent containing the chalcogen in the vapor phase is preferably at temperatures above 300 ° C.