Nano transition metal oxide, gas-phase synthesis method and application

Abstract

The invention provides a nano transition metal oxide and a gas-phase synthesis method and application thereof, and belongs to the technical field of metal oxides. The gas-phase synthesis method of the nano transition metal oxide comprises the following steps: respectively and continuously introducing transition metal carbonyl compound gas and ozone gas into a reaction device, so that the transition metal carbonyl compound gas and the ozone gas are subjected to oxidation reaction to obtain the nano transition metal oxide.

Description

Technical Field

[0001] The present invention relates to the technical field of metal oxides, and in particular to a nano transition metal oxide and a gas phase synthesis method and application thereof. Background Art

[0002] As primary energy reserves gradually decline and environmental problems become increasingly prominent, new energy development and energy storage innovation have become hot topics of global concern.

[0003] Transition metal oxides are abundant in reserves, have excellent physical and chemical properties, and are low in cost. They have become key materials in many fields such as catalysis, energy, environmental protection, and biomedicine. In particular, at the nanoscale, transition metal oxides are more widely used, such as as catalysts to promote the resource utilization of CO2 reforming, and as electrode materials to improve the performance of energy storage and conversion equipment. However, since the preparation of such materials usually involves high temperature or burning treatment, the size and properties of nanomaterials are relatively random, and the products show the characteristics of consistent batch properties. At the same time, the preparation process has the disadvantages of high energy consumption, complex process, poor continuity, and serious pollution. Summary of the invention

[0004] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present invention provides a nano transition metal oxide and a gas phase synthesis method and application.

[0005] According to an embodiment of one aspect of the present invention, a gas phase synthesis method of nano transition metal oxide is provided, comprising: continuously introducing transition metal carbonyl compound gas and ozone gas into a reaction device respectively, so that the transition metal carbonyl compound gas and the ozone gas undergo an oxidation reaction to obtain nano transition metal oxide.

[0006] According to an embodiment of the present invention, causing the transition metal carbonyl compound gas to undergo an oxidation reaction with the ozone gas includes: the transition metal carbonyl compound and oxygen atoms in the ozone gas form transition metal-oxygen-transition metal chemical bonds through bridging coordination.

[0007] According to an embodiment of the present invention, the nano transition metal oxide has a lattice structure or is amorphous.

[0008] According to an embodiment of the present invention, when the nano transition metal oxide has a lattice structure: the nano transition metal oxide includes nano nickel oxide, and the transition metal carbonyl compound gas includes gaseous nickel tetracarbonyl; when the nano transition metal oxide is amorphous: the nano transition metal oxide includes nano ferric oxide, and the transition metal carbonyl compound gas includes gaseous iron pentacarbonyl.

[0009] According to an embodiment of the present invention, the carrier gas of the transition metal carbonyl compound gas is an inert gas or clean air; and the concentration of the ozone gas is >3000 ppmv.

[0010] According to an embodiment of the present invention, when the nano transition metal oxide has a lattice structure, the temperature of the oxidation reaction is 10~50°C and the pressure is 1~1.1atm; when the nano transition metal oxide is amorphous: the temperature of the oxidation reaction is 10~70°C and the pressure is 1~1.1atm.

[0011] According to an embodiment of the present invention, the residence time of the transition metal carbonyl compound gas and the ozone gas in the reaction device is 2 to 5 seconds respectively.

[0012] According to another embodiment of the present invention, there is provided a nano transition metal oxide, which is prepared by the above-mentioned gas phase synthesis method.

[0013] According to an embodiment of the present invention, when the nano transition metal oxide has a lattice structure, the particle size of the nano transition metal oxide is 5-35 nm; when the nano transition metal oxide is amorphous, the particle size of the nano transition metal oxide is 4-18 nm.

[0014] According to another embodiment of the present invention, there is provided an application of the above-mentioned nano transition metal oxide in the fields of catalyst, electrochemical energy storage, preparation of electrode materials, and gas sensing technology.

[0015] According to an embodiment of the present invention, the present invention uses a transition metal carbonyl compound gas as a reaction precursor, and the reaction precursor has one or more carbonyl ligands bonded to a transition metal atom. The transition metal carbonyl compound gas and ozone gas are mixed in a reaction device to undergo an oxidation reaction, during which the transition metal central atom loses electrons and provides them to ozone molecules, so that the carbonyl ligands are separated to form corresponding transition metal oxides. As the oxidation reaction proceeds, the generated transition metal oxides aggregate or condense in the gas phase, and the obtained product has a nanoscale morphology, thereby forming a nano transition metal oxide. The nano transition metal oxide prepared by the gas phase synthesis method has a high purity, and the synthesis process of the gas phase synthesis method is simple, and the nano transition metal oxide can be continuously prepared directly by the gas phase, with a high yield.

[0016] According to the embodiments of the present invention, the present invention uses a relatively novel oxidation reaction process, and the raw materials are widely available and inexpensive. The gas phase reaction process is controllable and has stable performance. The method of the present invention does not involve high temperature (for example, greater than 70°C) heating, grinding and other energy-consuming processes. The operation is simple, and the product is nanoscale with good stability, which is suitable for low-cost industrial environmentally friendly production. The reaction preparation method provided by the present invention has good universality in the field of transition metals, is a new synthesis idea of ​​nano transition metal oxides, and is of great significance to the application field of nano transition metal oxides. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0018] Figure 1 A reaction mechanism diagram showing the preparation process of nano nickel oxide according to an embodiment of the present invention;

[0019] Figure 2 The reaction mechanism diagram of the preparation process of nano-iron trioxide according to the embodiment of the present invention is shown;

[0020] Figure 3 The X-ray diffraction spectrum of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown;

[0021] Figure 4 The scanning electron microscope image of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown, wherein a is a scanning electron microscope image of the nickel oxide nanoparticles, and b is a partial enlarged image of a;

[0022] Figure 5 The particle size distribution diagram of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown;

[0023] Figure 6 The X-ray diffraction spectrum of the ferric oxide nanoparticles prepared in Example 3 of the present invention is shown;

[0024] Figure 7 The X-ray electron spectrum calibration diagram of the ferric oxide nanoparticles and the ferric oxide sample prepared in Example 3 of the present invention is shown;

[0025] Figure 8 The transmission electron microscope image of the ferric oxide nanoparticles prepared in Example 3 of the present invention is shown, wherein a is a transmission electron microscope image of the ferric oxide nanoparticles, b is a partial enlarged image of a portion, and c is a partial enlarged image of another portion of a;

[0026] Fig. 9 The particle size distribution diagram of the ferric oxide nanoparticles prepared in Example 3 of the present invention is shown, wherein a is Figure 8 The particle size distribution diagram corresponding to the part b in the figure is Figure 8 The particle size distribution diagram corresponding to part c in the figure. DETAILED DESCRIPTION

[0027] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0028] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0029] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0030] Due to the high price of precious metal materials, it is difficult to use them widely in applications. Other metal oxides are required to replace them in related technologies. Transition metal oxides have excellent catalytic properties and are abundant in reserves, so they have great development potential.

[0031] One approach in the related art is to prepare the nanomaterial by first precipitating from the liquid phase and then depositing and burning it, or by first oxidizing the solid phase and then burning it. However, the high-temperature burning treatment makes the size and properties of the nanomaterials more random, and the energy consumption in the preparation process is high, the process is more complicated, the continuity is poor, and the pollution is more serious.

[0032] Another approach in the related art is to prepare transition metal oxides by liquid-solid multiphase synthesis, such as synthesizing precursors by hydrothermal reaction, electrochemical deposition, gel sedimentation, etc., and then obtaining nanoparticles through separation / washing, roasting and other procedures. This results in high synthesis cost, complex process, long reaction time, and poor uniformity of the obtained product.

[0033] In the process of realizing the concept of the present invention, it was found that by mixing transition metal carbonyl compound gas and ozone gas in a reaction device to cause an oxidation reaction, the transition metal central atom loses electrons to provide them to ozone molecules, causing the carbonyl ligand to detach, thereby forming a transition metal oxide.

[0034] Specifically, according to an embodiment of one aspect of the present invention, a gas phase synthesis method of nano transition metal oxide is provided, comprising: continuously introducing transition metal carbonyl compound gas and ozone gas into a reaction device respectively, so that the transition metal carbonyl compound gas and the ozone gas undergo an oxidation reaction to obtain nano transition metal oxide.

[0035] According to an embodiment of the present invention, by continuously passing transition metal carbonyl compound gas and ozone gas into the reaction device respectively, the metal central atom of the transition metal carbonyl compound loses electrons to provide to the ozone molecule, the carbonyl ligand is separated, and then a transition metal oxide is formed. Accompanied by the reaction, the obtained transition metal oxide is aggregated or condensed in the gas phase to form a nanoscale morphology. Without involving processes such as grinding, the operation is relatively simple, the repeatability is strong, the continuity is good, the size distribution of the obtained nano transition metal oxide is relatively uniform within the range, the yield is high, the energy consumption is low, and the tail gas is pollution-free, which is suitable for low-cost industrial environmental protection production.

[0036] According to an embodiment of the present invention, the transition metal carbonyl compound gas and the ozone gas undergo an oxidation reaction, including: the transition metal carbonyl compound and the oxygen atom in the ozone gas form a transition metal-oxygen-transition metal chemical bond through bridging coordination. The microscopic process of the oxidation reaction can be understood as follows: the transition metal carbonyl compound gas and the ozone molecule contact each other in the reaction device, the transition metal carbonyl compound gas receives the nucleophilic attack and bridging disturbance of the oxygen atom in the center of the ozone molecule, which helps to form the transition metal-oxygen-transition metal chemical bond, weakens the electronic interaction between the transition metal and the carbon atom, the carbonyl ligand captures the unbridged oxygen atom at the side of the ozone to form carbon dioxide gas and detaches, and the intermediate formed is further subjected to the nucleophilic attack or nucleophilic disturbance of the oxygen atom in the center of the ozone molecule, and then the intermediate continues to bridge epitaxially, resulting in more carbonyl ligand oxidation detachment and transition metal-oxygen bridging, thereby forming a transition metal oxide.

[0037] According to an embodiment of the present invention, the nano transition metal oxide has a lattice structure or is amorphous. It is understood that different prepared nano transition metal oxides have different microscopic morphologies, and the following will be described based on different morphologies.

[0038] It can be understood that when the nano transition metal oxide has a lattice structure, nickel oxide can be used as an example for introduction. Figure 1 The reaction mechanism diagram of the preparation process of nano nickel oxide in the embodiment of the present invention is shown. Figure 1 As shown, the microscopic process of the oxidation reaction can be understood as the contact between the carbonyl nickel gas molecules and the ozone molecules in the reaction device in the reaction system, the carbonyl nickel is subjected to the nucleophilic attack and bridging disturbance of the central oxygen atom of the ozone molecule to form a nickel-oxygen-nickel bridge bond, which weakens the electronic interaction between nickel and carbon atoms, and the carbonyl ligand captures the unbridged oxygen atom at the side of the ozone to form carbon dioxide gas detachment, and the formed carbonyl nickel-oxygen intermediate is further subjected to the nucleophilic attack and epitaxial bridging of the central oxygen atom of the ozone molecule, resulting in more carbonyl ligand oxidation detachment and nickel-oxygen skeleton bridging, forming a face-centered cubic structure of nickel oxide unit cells, the unit cells continue to grow epitaxially to become nickel oxide grains, the grains continue to flow and accumulate with the gas flow, and spontaneously precipitate nanoscale nickel oxide (NiO) particles with a regular lattice morphology.

[0039] It should be noted that nickel oxide, as a wide bandgap P-type semiconductor oxide, has excellent thermal stability and photoelectric properties in its nanoscale structure. In the related art, the preparation method of nickel oxide nanomaterials usually includes a method of first liquid phase precipitation, then deposition and burning, or a method of first solid phase oxidation, then burning. The burning in the above preparation process usually requires a high temperature of about 700°C, which makes the size and characteristics of the prepared nickel oxide nanomaterials more random and difficult to apply. In addition, the preparation process usually needs to be prepared in batches, and the nickel oxide nanomaterials prepared in different batches are more different, which has a great impact on the performance of the nickel oxide nanomaterials. At the same time, the preparation process has the disadvantages of high energy consumption, complex process, poor continuity and serious pollution. The gas phase synthesis method of the present invention has good continuity, avoids the addition of acid or alkali, and also avoids the above-mentioned high temperature burning treatment. It can form a nano morphology autonomously, while maintaining a high yield, has low energy consumption and simple operation. It can achieve continuous preparation under the same conditions, reduce the possible differentiation in the related technology, and has great application value and potential.

[0040] It can be understood that when the nano transition metal oxide is amorphous, for example, ferric oxide can be used as an example for introduction. Figure 2 The reaction mechanism diagram of the preparation process of nano-iron trioxide in the embodiment of the present invention is shown. Figure 2As shown, the microscopic process of the oxidation reaction can be understood as the contact and collision of carbonyl iron gas and ozone molecule gas. The positive charge effect of the central oxygen atom of the ozone molecule attracts the central iron atom, bridging to form an iron-oxygen-iron bridge bond. The electron interaction of the carbonyl coordination bonds of adjacent bridge bonds is disturbed, and the carbonyl ligand extracts the unbridged oxygen atom at the ozone end to form carbon dioxide gas and detaches. The central iron atom of the formed carbonyl iron-oxygen intermediate is again nucleophilically disturbed by the ozone molecule, and the molecular bridging and extension continue, resulting in the gradual oxidation and detachment of the carbonyl ligand. The assembly behavior of oxygen loading and carbonyl unloading continues until the bridging atoms accumulate and precipitate, and finally spontaneously form nanoscale stacked ferric oxide (Fe2O3) particles with no fixed shape.

[0041] Hematite (α-Fe2O3) has n-type semiconductor properties, and its advantages of low cost, corrosion resistance and high stability make it play an important role in the electrode materials of photoelectrochemical cells and the catalysts and sensing elements of sensors. It should be noted that the electrode materials prepared by doping with ferric oxide have obvious volume expansion, pulverization and degradation during the charge and discharge process, which limits its application. Related art finds that the volume expansion effect can be effectively improved by nano-Fe2O3, loading conductive current collectors and ion doping. For example, the hollowing and clustering of nano-Fe2O3 can increase the spatial volume and specific surface area of ​​the nanoparticles and optimize their electrochemical properties, which shows that nano-iron oxide has good prospects in the application of batteries. However, in the related art, the multiphase reaction of separation and calcination is mostly carried out, and the process is relatively energy-consuming, resulting in the problems of high energy consumption and complex process in the preparation process. The nano-iron oxide obtained by the gas phase synthesis method of the present invention has good dispersibility, relatively uniform particle distribution, good repeatability, and a relatively simple synthesis process, with low cost and sustainable industrial production application prospects.

[0042] In one embodiment, when the nano transition metal oxide has a lattice structure, the nano transition metal oxide includes nano nickel oxide, and the transition metal carbonyl compound gas includes gaseous nickel tetracarbonyl. The reaction process between gaseous nickel tetracarbonyl and ozone gas is shown in the following formula (1):

[0043] Formula (1).

[0044] In another embodiment, when the nano transition metal oxide is amorphous: the nano transition metal oxide includes nano iron trioxide, and the transition metal carbonyl compound gas includes gaseous pentacarbonyl iron. The reaction process between gaseous pentacarbonyl iron and ozone gas is shown in the following formula (2):

[0045] Formula (2).

[0046] According to an embodiment of the present invention, the preparation of nano transition metal oxides with different structures is achieved by using different transition metal carbonyl compounds. The gas phase synthesis method has the advantages of low energy consumption, continuity and good repeatability. The prepared nano-morphological product with a lattice structure can spontaneously form a dispersion characteristic on the nanoscale, and has a high purity and a good uniformity of particle size. After continuous preparation, it can be directly put into subsequent application processes, and the process is relatively simple; the prepared amorphous nano-product can spontaneously form a dispersion characteristic on the nanoscale, and has a high purity and a good uniformity of particle size, which provides a newer preparation method for amorphous nano-products.

[0047] According to an embodiment of the present invention, the carrier gas of the transition metal carbonyl compound gas is an inert gas or clean air, and the inert gas can be, for example, nitrogen or argon. Based on cost considerations, nitrogen is preferred. Clean air can be understood as a gas that has been purified to remove moisture, carbon dioxide and other impurity components that may affect the reaction, so that the prepared nano product is purer. It should be noted that in the process of using gaseous carbonyl iron to prepare ferric oxide nanoparticles, the carrier gas of gaseous carbonyl iron is preferably nitrogen. The carrier gas of ozone gas can be, for example, high-purity oxygen or clean air. Ozone gas can be prepared by high-voltage discharge of high-purity oxygen or clean air. The concentration of ozone gas is greater than 3000ppmv, for example, it can be 3200ppmv, 3400ppmv, 3600ppmv, 3800ppmv or 4000ppmv. The concentration of ozone gas is adjusted to the above range, which can provide enough active oxygen to efficiently and quickly oxidize transition metal carbonyl compounds, thereby helping to improve the reaction rate and yield.

[0048] According to an embodiment of the present invention, when the nano transition metal oxide has a lattice structure, the temperature of the oxidation reaction is 10-50°C, for example, 10°C, 20°C, 30°C, 40°C or 50°C. It should be noted that the melting point of carbonyl nickel is low and it is flammable and explosive. Therefore, the temperature of the oxidation reaction is adjusted to the above reaction to reduce the risk of the reaction system. The pressure is 1-1.1atm, for example, 1atm, 1.05atm or 1.1atm; when the nano transition metal oxide is amorphous: the temperature of the oxidation reaction is 10-70°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C or 70°C, and the pressure is 1-1.1atm, for example, 1atm, 1.05atm or 1.1atm. It can be understood that the transition metal carbonyl compound gas flow and the ozone gas flow are simultaneously introduced into the reaction device to carry out a gas phase oxidation reaction, and the deposited particle product is collected to obtain the nano transition metal oxide. Compared with the preparation methods in the related art, the synthesis method of the present invention is simple, and continuous preparation can be achieved at room temperature or slightly heated and at normal pressure or slightly pressurized, so that the reaction energy consumption is low. It can continuously prepare nano-shaped products while maintaining low costs, which is conducive to industrial promotion and application.

[0049] In the process of preparing nickel oxide nanoparticles using gaseous nickel tetracarbonyl, the molar ratio of the carbonyl nickel in the carbonyl nickel gas flow to the ozone in the ozone gas flow is 1: (1-8), for example, it can be 1: 1, 1: 3, 1: 5, 1: 7 or 1: 8; in the process of preparing nano iron oxide using gaseous iron pentacarbonyl, the molar ratio of the iron pentacarbonyl in the carbonyl iron gas flow to the ozone in the ozone gas flow is 1: (1-10), for example, it can be 1: 1, 1: 2, 1: 4, 1: 6, 1: 8 or 1: 10. Adjusting the molar ratio of the raw materials within the above range is helpful to achieve full oxidation of the transition metal carbonyl compound gas and improve the reaction efficiency.

[0050] According to an embodiment of the present invention, the residence time of the transition metal carbonyl compound gas and the ozone gas in the reaction device is 2 to 5 s, for example, 2 s, 3 s, 4 s or 5 s. It can be understood that the reaction device can be, for example, a reaction tube or a reaction ball, and the material of the reaction tube or the reaction ball can be, for example, inorganic glass or other inert non-metallic materials. The transition metal carbonyl compound gas can be continuously passed into the reaction tube or the reaction ball through a pipeline, and the reaction tube or the reaction ball can be understood as a closed reaction system. Ozone gas is synchronously and continuously passed into the reaction tube or the reaction ball through another pipeline, and an internal turbulent system is formed in the reaction tube or the reaction ball. The internal turbulence can be understood as making the transition metal carbonyl compound gas and the ozone gas mix more fully, forming a turbulent state of the mixed gas, and promoting full contact between the two. Further, the residence time can be understood as the time difference between the two gases from entering the reaction device to flowing out of the reaction device. As can be seen from the above, due to the strong oxidizing property of ozone, the two gases can be fully contacted and reacted quickly, and the process of continuous preparation is further realized by passing into the reaction tube or the reaction ball.

[0051] It should be noted that, as required, a diaphragm is coated at the outlet end of a reaction tube or a reaction ball or a ground glass with a small aperture is used to collect the generated nano transition metal oxide on the diaphragm. The diaphragm can be, for example, a Teflon membrane, a quartz sand chip, etc., and the quartz sand chip can be understood as a relatively thick filter membrane. In the process of carrying out the relevant experiments of the present invention, it is found that when the above-mentioned diaphragm is used to collect the nano transition metal oxide, the collected product is a nano granular product. If the ground glass with a small aperture is used to collect the nano transition metal oxide, the collected product can be columnar. Due to the use of different collection methods, the collected nano transition metal oxide has different shapes, so the present invention does not particularly limit the shape of the obtained nano transition metal oxide.

[0052] According to an embodiment of the present invention, the reaction tail gas can be recovered at the outlet of the reaction system as needed, and the transition metal carbonyl compound gas, ozone, carrier gas, etc. can be recovered and recycled. For example, when there is an excess of carbonyl iron gas, the carbonyl iron gas flow can be recovered and reused; and when there is an excess of ozone gas, the ozone gas flow can be recovered and reused.

[0053] It is understood that the transition metal carbonyl compound can be purchased commercially or prepared by itself as required.

[0054] Taking the preparation of gaseous carbonyl nickel from nickel powder as an example, the preparation process is as follows: Place metallic nickel in a reaction tube and introduce a hydrogen flow to remove the residual air in the reaction tube. Continue to introduce the hydrogen flow, raise the temperature from room temperature to 430-470°C at a heating rate of 25-35°C / min, and maintain the temperature at 430-470°C for reduction reaction, and the reaction time is 10-14h.

[0055] The hydrogen flow is continuously introduced, and after the reaction temperature is reduced to between 180 and 220° C., the hydrogen flow is stopped. A carbon monoxide flow is introduced, and the reaction is naturally cooled to 60 to 80° C. to prepare gaseous nickel tetracarbonyl.

[0056] According to an embodiment of the present invention, the flow rate of hydrogen gas is 100 mL / min, and the purity of hydrogen gas is 99.999%; the flow rate of carbon monoxide gas is 300 mL / min, and the purity of carbon monoxide is 99.999%.

[0057] Taking the preparation of gaseous pentacarbonyl iron as an example, the preparation process is as follows: Place dinonyl iron in a U-shaped glass tube and introduce nitrogen flow to remove the residual air in the U-shaped glass tube. Continue to maintain the nitrogen flow, and heat the temperature from room temperature to 120~130℃ at a heating rate of 25~35℃ / min to melt and crack the dinonyl iron. The gas flow collected at the rear end of the U-shaped glass tube is introduced into a low-temperature collection tube (0~20℃) to collect liquid pentacarbonyl iron. The reaction process is shown in the following formula (3):

[0058] Formula (3).

[0059] It should be noted that the collected pentacarbonyl iron is in liquid form. By using, for example, a nitrogen gas flow to purge the liquid surface of the liquid carbonyl iron, the volatilized gaseous pentacarbonyl iron is purged into the reaction device to facilitate control of the flow rate and / or flow rate of the gaseous pentacarbonyl iron entering the reaction device for subsequent oxidation reaction.

[0060] According to an embodiment of the present invention, the flow rate of nitrogen gas inflow is 300 mL / min, and the purity of nitrogen gas is 99.999%.

[0061] According to an embodiment of the present invention, taking the preparation of nano ferric oxide as an example, the iron atom in the center of gaseous carbonyl iron is "split and assembled" through the O3 positive charge excitation effect, so as to realize gas phase synthesis and precipitation of nano Fe2O3. This gas phase synthesis method involves that the reactants are all gaseous, the reactants have sufficient contact and collision space, the condensed particle products are easy to separate and collect, and the obtained nano Fe2O3 has the characteristics of uniform composition, scale and properties. The nano Fe2O3 obtained by the present invention has good stability and has a typical high specific surface area flocculent nanostructure.

[0062] Compared with the related art, the synthesis process of the present invention for preparing amorphous nano transition metal oxides is simple and can realize direct and continuous preparation of nano transition metal oxides. Taking ferric oxide as an example, the present method realizes a homogeneous oxidation process, realizes continuous synthesis of transition metal oxides at low energy consumption, and prepares and forms nano Fe2O3 by direct gas phase nucleation. The synthesis process is simple and is significantly different from other Fe2O3 micro-nano structures in related art in terms of synthesis mechanism, surface morphology, growth nucleation, etc.; the synthesis method provides a relatively novel oxidation reaction process, simplifies the multiphase synthesis process of transition metal oxides, and does not involve high-temperature heating (for example, about 700°C), grinding and other energy-consuming processes. The product presents a uniform nanoscale, good stability, high yield, and is suitable for low-cost industrial environmentally friendly production. It will be important in the fields of catalysts, electrochemical energy storage, electrode materials, etc.

[0063] According to an embodiment of the present invention, a nano transition metal with a lattice structure is prepared, and the preparation of nano nickel oxide is taken as an example. Under the excitation of the strong oxidant O3, the precursor gaseous tetracarbonyl nickel molecule undergoes complex coordination bond breakage, atomic addition recombination and molecular overflow, and finally spontaneously grows and accumulates to form nano nickel oxide. The reaction precursor of this gas phase reaction synthesis method maintains a gaseous state, which promotes the effective collision and oxidation reaction of tetracarbonyl nickel molecules and ozone molecules, and spontaneously agglomerates to form nano nickel oxide, which essentially reflects that the nano nickel oxide formed by gas phase molecular collision and reaction has high purity, high yield, good stability, and has a typical nano structure.

[0064] Compared with the related art, the synthesis process of the present invention for preparing nano transition metal oxides with lattice structure is simple, and can realize direct gas phase nucleation and continuous preparation of nano transition metal oxides. Taking nickel oxide (NiO) as an example, the NiO synthesized and prepared by the present method is significantly different from the NiO nanostructure of the related art in terms of synthesis mechanism, surface morphology, growth nucleation, etc. The raw materials selected by the present invention are widely available and low in price. The gas phase reaction process is controllable and has stable performance. It does not involve energy-consuming processes such as high-temperature heating (for example, about 700°C) and grinding. The operation is simple, and the obtained oxide nanoparticles are nanoscale, have good stability, high yield, and are suitable for low-cost industrial environmentally friendly production. The gas phase synthesis method provided by the present invention is suitable for the preparation of more nano transition metal oxides, and is a new synthesis idea of ​​transition metal oxides, which is of great significance to the application field of transition metal oxides.

[0065] According to another embodiment of the present invention, there is provided a nano transition metal oxide, which is prepared by the above-mentioned gas phase synthesis method.

[0066] According to the embodiments of the present invention, the prepared nano transition metal oxide has a relatively uniform nano size, high stability, purity and dispersibility, and is better suited for subsequent applications.

[0067] According to an embodiment of the present invention, when the nano transition metal oxide has a lattice structure: the particle size of the nano transition metal oxide is 5 to 35 nm, for example, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm or 35 nm; when the nano transition metal oxide is amorphous: the particle size of the nano transition metal oxide is 4 to 18 nm, for example, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm or 18 nm. It can be understood that the particle sizes of the two nanoparticles are both micro-nano-level, and the particle size distribution is narrow and uniform. In subsequent use, they have good dispersibility and can be well applied in a wide range of fields.

[0068] According to another embodiment of the present invention, there is provided an application of the above-mentioned nano transition metal oxide in the fields of catalyst, electrochemical energy storage, preparation of electrode materials, and gas sensing technology.

[0069] According to an embodiment of the present invention, in a nano transition metal oxide having a lattice structure, taking nickel oxide as an example, due to good uniformity and dispersibility, it has relatively excellent catalytic performance in subsequent use in catalysts, and its reserves are abundant, and it has good practical value in the photolysis of water and hydrogen evolution reaction. In terms of electrochemical energy storage and the preparation of electrode materials, it has a wide bandgap, a high theoretical capacity, and a large application potential. In addition, due to the thermal stability and photoelectric properties of nickel oxide, it is also widely used in the field of gas sensors. In amorphous nano transition metal oxides, taking ferric oxide as an example, by applying nano ferric oxide to the negative electrode material of lithium batteries, the volume expansion, differentiation and degradation during the charge and discharge process are reduced, and the applicable field of nano ferric oxide is broadened.

[0070] The present invention is further described below by embodiments and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined into other feasible embodiments at will.

[0071] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or homemade by recognized processing methods.

[0072] Embodiment 1:

[0073] Preparation of gaseous nickel tetracarbonyl from nickel powder:

[0074] Take 20g of metallic nickel powder and place it in a glass tube precursor reaction system. Pass a flow of H2 with a purity of 99.999% at a flow rate of 100mL / min and maintain it for 300s to completely displace the residual air in the gap between the inside of the glass tube and the metallic nickel powder.

[0075] Keeping the flow rate of H2 gas flow unchanged, the precursor reaction system was heated from room temperature to 450°C at 30°C / min. After isothermal reduction for 12 hours, the glass tube and the internal metal nickel powder were naturally cooled to 200°C while maintaining the original atmosphere conditions to completely reduce the inert nickel powder to active nickel powder, so that the more active nickel can further participate in the subsequent reaction.

[0076] After the precursor reaction system is cooled to 200°C, the H2 gas flow is replaced with a CO gas flow with a purity of 99.999% at a flow rate of 300 mL / min, and the precursor reaction system continues to be naturally cooled to completely displace the residual H2 in the gap between the inside of the glass tube and the metal nickel powder.

[0077] When the temperature of the precursor reaction system drops to 90° C., carbonyl nickel gas begins to be generated.

[0078] Preparation of nickel oxide nanoparticles from gaseous nickel tetracarbonyl:

[0079] The CO gas flow conditions were kept unchanged, the precursor reaction system was controlled at 60-80°C, and the precursor carbonyl nickel gas and CO carrier gas prepared by the precursor reaction system were simultaneously introduced into a glass reaction tube at room temperature and pressure (20°C, one atmosphere) together with an O3 gas flow at a flow rate of 60 mL / min to react and prepare NiO nanoparticles.

[0080] The black particles produced by the reaction were collected by filtering through a Teflon filter membrane to obtain self-generated nano-scale NiO nanoparticles.

[0081] The NiO nanoparticles prepared in Example 1 were characterized and analyzed. Figure 3 The X-ray diffraction (XRD) spectrum of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown. Figure 3 It can be seen that the diffraction characteristics of the products synthesized by the oxidation reaction under the conditions of excess reaction precursor Ni(CO)4 or excess O3 coincide with the peaks (111), (200), and (220) of the JCPDS NO.47-1049 NiO sample provided by the Joint Committee on Powder Diffraction Standards, that is, they are the same phase component NiO. The diffraction characteristic peaks have the diffraction characteristics of microcrystalline broad peaks, and the particle size is nanometer level.

[0082] Figure 4 The scanning electron microscope image of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown, wherein a is a scanning electron microscope image of the nickel oxide nanoparticles, and b is a local enlarged image of a. Figure 5 The particle size distribution diagram of the nickel oxide nanoparticles prepared in Example 1 of the present invention is shown. Figure 4~Figure 5 It can be seen that the NiO nanoparticles are spherical, with a particle size distribution of 16-32 nm. Combined with the transmission electron microscopy results of the preliminary experiment of the present invention, it can be obtained that the particle size distribution of the NiO nanoparticles is 5-35 nm.

[0083] Embodiment 2:

[0084] The preparation process of Example 2 is generally the same as that of Example 1, except for the following two aspects: first, in the process of preparing gaseous nickel tetracarbonyl, after the precursor reaction system is cooled to 200°C, the H2 gas flow is replaced with a CO gas flow with a flow rate of 100 mL / min. Second, in the process of preparing nickel oxide nanoparticles, the flow rate of the O3 gas flow is adjusted to 500 mL / min.

[0085] The NiO nanoparticles prepared in Example 2 were characterized and analyzed, and the characterization results were consistent with those in Example 1. Example 1 is an example in which Ni(CO)4 is in excess and O3 is in a small amount, and Example 2 is an example in which Ni(CO)4 is in a small amount and O3 is in excess. After comparison, the physical components and properties of the products of the two examples are the same. No residual O3 was detected in the tail gas component of Example 1, and no residual Ni(CO)4 was detected in the tail gas component of Example 2, indicating that the conversion efficiency of the oxidation reaction is nearly 100%, and the components and particle characteristics of the reaction products are not easily affected by the reaction conditions.

[0086] Embodiment 3:

[0087] Preparation of gaseous iron pentacarbonyl:

[0088] Take 10g of dinonyl iron carbonyl (Fe2(CO)9) powder and place it in a U-shaped glass tube precursor reaction system. Pass a N2 gas flow with a purity of 99.999% at a flow rate of 300mL / min and maintain it for 300s to completely remove the residual air in the gap between the inside of the glass tube and the dinonyl iron powder.

[0089] Keeping the N2 gas flow condition unchanged, the precursor reaction system was heated from room temperature to 125±5℃ at a heating rate of 30℃ / min and maintained for 30min to melt and crack the dinonyl carbonyl iron powder. The gas flow at the rear end of the U-shaped glass tube precursor reaction system was introduced into a low-temperature collection tube (bottom-in and top-out, 0~20℃) to collect liquid carbonyl iron (Fe(CO)5).

[0090] Preparation of FeO3 nanoparticles:

[0091] After adjusting the precursor reaction system to room temperature (15-50°C), the U-shaped glass tube precursor reaction system was sealed. The N2 gas flow conditions were kept unchanged, and the N2 gas flow direction was changed. The gaseous pentacarbonyl iron gas flow (nitrogen as carrier gas) was directly purged through the low-temperature collection tube with the O3 gas flow, and the gaseous pentacarbonyl iron gas flow (nitrogen as carrier gas) was introduced into the glass gas phase reaction tube at room temperature and pressure (20°C, one atmosphere) together with the O3 gas flow. The flow rate of the gaseous pentacarbonyl iron gas flow was maintained at 300 mL / min, and the flow rate of the synchronously introduced O3 gas flow was 60 mL / min, and Fe2O3 nanoparticles were prepared in the glass gas phase reaction tube.

[0092] The brown particles produced by the reaction were collected by filtering through a Teflon filter membrane to obtain native amorphous nano-scale Fe2O3 nanoparticles.

[0093] The Fe2O3 nanoparticles prepared in Example 3 were characterized and analyzed. Figure 6 FIG. 3 shows the X-ray diffraction spectrum of the ferric oxide nanoparticles prepared in Example 3 of the present invention. Figure 6 It can be seen that the diffraction pattern of the product synthesized by the oxidation reaction under the conditions of excess reaction precursor Fe(CO)5 or excess O3 is a double hump with a wide peak width, indicating that the product is an amorphous stacking structure.

[0094] Figure 7 The X-ray electron spectrum calibration diagram of the ferric oxide nanoparticles and the ferric oxide sample (purchased commercial product) prepared in Example 3 of the present invention is shown. Figure 7 It can be seen that the Fe2O3 nanoparticles prepared by the present invention ( Figure 7 FeO x ) spectrum and the Fe2O3 sample ( Figure 7 The energy spectrum of the a-Fe2O3 in the sample is highly coincident, and the peak position of the main peak anti-fold integral peak is consistent with that of the ferric oxide sample; this result is the same as the peak position of Fe2O3 mentioned in the related art, proving that the product prepared by the present invention is Fe2O3.

[0095] It should be noted that the ferric oxide sample used in the present invention is a high-purity commercial product.

[0096] Figure 8 The transmission electron microscope image of the ferric oxide nanoparticles prepared in Example 3 of the present invention is shown, wherein a is a transmission electron microscope image of the ferric oxide nanoparticles, b is a partial enlarged image of a portion, and c is a partial enlarged image of another portion of a; Fig. 9 The particle size distribution diagram of the ferric oxide nanoparticles prepared in Example 3 of the present invention is shown, wherein a is Figure 8 The particle size distribution diagram corresponding to the part b in the figure is Figure 8 The particle size distribution diagram corresponding to the c part in the figure. Figure 8~Figure 9 It can be seen that the Fe2O3 nanoparticles are spherical and the particle size distribution is 4~18nm.

[0097] Embodiment 4:

[0098] The preparation process of this embodiment 4 is generally the same as that of embodiment 3, except for the following three aspects: first, when the low temperature collection tube is introduced, the temperature of the low temperature collection tube is -3 to 5°C. Second, during the preparation of Fe2O3 nanoparticles, the flow rate of the O3 gas flow is adjusted to 800 mL / min. Third, the yellow-brown particles produced by the filtration reaction are filtered using a quartz sand core filter membrane.

[0099] The Fe2O3 nanoparticles prepared in Example 4 were characterized and analyzed, and the characterization results were consistent with those in Example 3. Example 3 is an example in which Fe(CO)5 is excessive and O3 is small, and Example 4 is an example in which Fe(CO)5 is small and O3 is excessive. After comparison, the physical components and properties of the products of the two examples are the same. No residual O3 was detected in the tail gas component of Example 3, and no residual Fe(CO)5 was detected in the tail gas component of Example 4, indicating that the conversion efficiency of the oxidation reaction is nearly 100%, and the components and particle characteristics of the reaction products are not easily affected by the reaction conditions.

[0100] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A gas phase synthesis method of nano transition metal oxides, characterized in that: include: The transition metal carbonyl compound gas and the ozone gas are respectively and continuously introduced into the reaction device so that the transition metal carbonyl compound gas and the ozone gas undergo an oxidation reaction to obtain nano transition metal oxides.

2. The gas phase synthesis method according to claim 1, characterized in that: The step of causing the transition metal carbonyl compound gas to undergo an oxidation reaction with the ozone gas comprises: The transition metal carbonyl compound and the oxygen atom in the ozone gas form a transition metal-oxygen-transition metal chemical bond through bridging coordination.

3. The gas phase synthesis method according to claim 1 or 2, characterized in that: The nano transition metal oxide has a lattice structure or is amorphous.

4. The gas phase synthesis method according to claim 3, characterized in that: In the case where the nano transition metal oxide has a lattice structure: The nano transition metal oxide includes nickel oxide nanoparticles, and the transition metal carbonyl compound gas includes gaseous nickel tetracarbonyl; When the nano transition metal oxide is amorphous: The nano transition metal oxide comprises iron oxide nanoparticles, and the transition metal carbonyl compound gas comprises gaseous iron pentacarbonyl.

5. The gas phase synthesis method according to claim 3, characterized in that: The carrier gas of the transition metal carbonyl compound gas is an inert gas or clean air; The concentration of ozone gas is >3000ppmv.

6. The gas phase synthesis method according to claim 4, characterized in that: In the case where the nano transition metal oxide has a lattice structure, The temperature of the oxidation reaction is 10-50°C and the pressure is 1-1.1 atm; When the nano transition metal oxide is amorphous: The temperature of the oxidation reaction is 10-70° C. and the pressure is 1-1.1 atm.

7. The gas phase synthesis method according to claim 3, characterized in that: The residence time of the transition metal carbonyl compound gas and the ozone gas in the reaction device is 2 to 5 seconds respectively.

8. A nano transition metal oxide prepared by the gas phase synthesis method according to any one of claims 1 to 7.

9. The nano transition metal oxide according to claim 8, characterized in that: In the case where the nano transition metal oxide has a lattice structure: The particle size of the nano transition metal oxide is 5 to 35 nm; When the nano transition metal oxide is amorphous: The particle size of the nano transition metal oxide is 4-18 nm.

10. Use of the nano transition metal oxide as claimed in claim 8 or 9 in the fields of catalyst, electrochemical energy storage, preparation of electrode materials and gas sensing technology.

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