Method for growing single-walled carbon nanotubes by using anoxic oxide-loaded metal catalyst

Abstract

The invention discloses a method for growing a single-walled carbon nanotube by using an anoxic oxide-loaded metal catalyst. According to the method, oxide powder with a high specific surface area is treated by virtue of various technical strategies, so that the oxygen vacancy-rich oxygen-deficient carrier is obtained. A salt solution containing metal ions is used as a precursor, and the supported metal catalyst is prepared by adopting a dipping and high-temperature calcination combined strategy. The oxygen vacancies can promote dissociation of water adsorbed on the surface, increase the content of electronegative hydroxyl on the surface of the carrier, facilitate attraction of metal cations and bonding to the surface of the carrier through chemical bonds, and meanwhile, the oxygen vacancies can enhance the activity of the metal nanoparticles. The high-quality single-walled carbon nanotube is grown on the oxygen-deficient oxide-loaded metal catalyst by using a chemical vapor deposition technology, and a material foundation is laid for the application of the carbon nanotube in the high-end field and the development of related industries.

Description

Technical Field

[0001] The invention relates to the technical field of single-walled carbon nanotubes, and in particular to a method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-loaded metal catalyst. Background Art

[0002] Carbon nanotubes are typical one-dimensional nanocarbon materials. Their unique tubular structure and excellent physical and chemical properties make them have broad application prospects in many fields such as nanoelectronics, composite materials, and chemical and biological sensing. Therefore, carbon nanotubes are included in the first batch of 15 cutting-edge materials in the "Guidelines for the Key Development of Frontier Materials Industrialization" issued by the Ministry of Industry and Information Technology in 2023. For example, carbon nanotubes can be used as conductive agents for lithium-ion batteries and significantly improve the energy density of batteries due to their excellent conductivity and the fact that they require less addition than traditional conductive agents (only 1 / 6 to 1 / 2). Single-walled carbon nanotubes (SWNTs) formed by curling single-layer graphene have advantages in chemical properties, conductivity, elastic modulus, etc. The large-scale preparation of SWNTs powder is a prerequisite for promoting its application in various fields. However, SWNTs products currently have problems such as low production capacity and high prices. my country's research on the large-scale preparation of SWNTs started late, and most of the SWNTs used for basic research and application rely on imports. Therefore, it is urgent to develop a large-scale preparation technology for high-purity SWNTs powders.

[0003] At present, the growth of SWNTs on supported catalysts by chemical vapor deposition is a common method in industry and laboratories. The supported catalyst is mainly composed of oxide carriers with high specific surface area and metal nanoparticles. The carrier can not only improve the dispersion of metal catalysts, but also provide sufficient space for the growth of SWNTs. However, the metal dispersion in supported catalysts is generally not high, the reduced metal particles are easy to agglomerate to form large-diameter particles, and the efficiency of nanoparticle catalytic growth is usually less than 5%, which limits the large-scale preparation of SWNTs. A large number of studies have shown that the dispersion and activity of metal nanoparticles not only depend on their own properties, but also are closely related to the components and surface properties of the carrier. In the traditional impregnation method, the oxide carrier and the precursor ions are only combined by van der Waals forces, which has problems such as poor dispersion and weak binding force, affecting the dispersion and binding of the metal on the carrier surface. Therefore, regulating the properties of the oxide carrier itself, improving the dispersion and anchoring effect of the carrier on the precursor ions, and enhancing the activity of catalyst nanoparticles is an effective way to prepare efficient supported metal catalysts.

[0004] Oxygen vacancies, as a common point defect, are widely present in oxides and affect the electronic structure and surface properties of the material. The methods for producing oxygen vacancies mainly include heat treatment, chemical reduction and plasma treatment. Oxygen vacancies can promote surface hydrolysis reactions, forming more negatively charged hydroxyl groups on the surface of the material, which can spontaneously repel anions, attract metal cations and bind to the surface of the material through chemical bonds. At the same time, oxygen vacancies can effectively reduce the nucleation barrier of SWNTs and promote preferential growth. Therefore, by using oxygen-deficient oxide carriers, the dispersion and anchoring effect of the carrier on metal ions can be improved, and the activity of catalyst particles can be enhanced, which is expected to prepare efficient supported metal catalysts and promote the large-scale preparation of SWNTs powders and their applications. Summary of the invention

[0005] Purpose of the invention: This project is driven by the demand for large-scale preparation of SWNTs and aims to develop efficient supported metal catalysts. Under the guidance of the mechanisms of the dispersion and anchoring of metal nanoparticles by oxygen-deficient oxides and the regulation of the activity of metal catalysts, a variety of processing technologies are used to prepare oxygen-deficient oxide carriers, combined with the impregnation method to prepare supported metal catalysts, and chemical vapor deposition technology is used to achieve large-scale preparation of SWNTs powders.

[0006] Technical solution: The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to the present invention comprises the following steps: (1) Using a variety of technical strategies, high specific surface area oxide powders are processed to prepare oxygen-deficient carriers rich in oxygen vacancies. Salt solutions containing metal ions are used as precursors to prepare supported metal catalysts through impregnation combined with high-temperature calcination strategies. Single-walled carbon nanotubes are grown on the catalysts using chemical vapor deposition technology.

[0007] Furthermore, the various technical strategies described in step (1) include heat treatment, chemical reduction, template strategy, and plasma.

[0008] Furthermore, in step (1), the oxide powder with a high specific surface area includes any one or more combinations of silicon oxide, aluminum oxide, and magnesium oxide.

[0009] Furthermore, in step (1), the salt solution containing metal ions is any one or more combinations of nitrates, chlorides, and acetylacetone complexes of transition metal ions.

[0010] Furthermore, in step (1), the impregnation combined with high temperature calcination strategy refers to regulating the type of carrier, the type of metal salt, the calcination temperature and the calcination time.

[0011] Furthermore, in step (1), the supported metal catalyst is composed of a composite of oxygen-deficient oxide powder and transition metal nanoparticles.

[0012] Furthermore, in step (1), the chemical vapor deposition technology refers to regulating the carbon source composition, gas flow rate, growth temperature and growth time.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: 1. It proposes an innovative method for regulating the structure of the oxide carrier itself, taking oxygen vacancy defects as the entry point, and based on the mechanism of action of oxygen vacancies, further improving the dispersion and anchoring effect of metal nanoparticles on the carrier and enhancing the reaction activity of catalyst particles. 2. The preparation of supported metal catalysts by impregnation combined with high-temperature calcination has the advantages of simple operation, high efficiency and speed, and a wide range of applications. 3. The chemical vapor deposition method has the advantages of low cost and strong controllability, and the SWNTs growth process is carried out under normal pressure conditions, with a short preparation time, which is conducive to the large-scale production and application of silicon-based composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is the Mg 1s spectrum of magnesium oxide before and after plasma treatment in Example 1; Figure 2 is the Raman spectrum of the grown sample before and after plasma treatment in Example 1, with an excitation laser of 633 nm; Figure 3 is the SEM image of the grown sample before and after plasma treatment in Example 1; Figure 4 is the thermogravimetric data of the grown sample before and after plasma treatment in Example 1; DETAILED DESCRIPTION

[0015] In order to make the contents of the invention of this application easier to understand, further explanation is provided below in conjunction with specific examples and drawings.

[0016] Embodiment 1: A method for growing single-walled carbon nanotubes using an oxygen-deficient magnesium oxide-supported cobalt metal catalyst comprises the following steps: (1) Place 5.0 g of magnesium oxide powder on the plasma equipment platform. In an air atmosphere, adjust the voltage to 100 V and the current to 3.0 A. Treat it in a glow discharge state for 0.5 h. Then turn off the power and cool it down to obtain magnesium oxide powder rich in oxygen vacancies.

[0017] (2) Dissolve 1.4 g Co(NO3)2·6H2O in deionized water to obtain a precursor solution. Then add 4.0 g magnesium oxide powder into the precursor solution and stir on a magnetic stirrer for 4 h. Then, place the impregnated sample in an oven at 100 °C for 24 h to completely dry it and grind it into powder.

[0018] (3) Place the catalyst in a quartz boat, and place the quartz boat in the middle of a dual-temperature zone slide-type chemical vapor deposition furnace. Connect the experimental device as required, set the furnace temperature program to 20 °C / min, and introduce argon gas at a flow rate of 500 sccm to remove the air in the device. After the sample temperature reaches the preset temperature of 800 °C, introduce methane carbon source gas at a flow rate of 50 sccm for 20 min. After the reaction is completed, turn off the methane gas and introduce argon gas. At the same time, stop heating and cool naturally to room temperature. Turn off the argon gas and take out the sample. Figure 1 The X-ray photoelectron spectroscopy in the image shows that the Mg 1s peak of the plasma-treated magnesium oxide powder moves toward a lower electron binding energy, indicating the presence of abundant oxygen vacancies. Next, the metal cobalt catalyst is loaded on the magnesium oxide powder before and after treatment to grow carbon nanotubes by chemical vapor deposition technology. Figure 2 The Raman spectrum of -1 The peaks of radial breathing modes (RBMs) of SWNTs were observed in the range, and the carbon tubes grown on the MgO support after plasma treatment had a larger G / D peak intensity ratio, which means better quality. Figure 3 The SEM images in the figure show that the density of SWNTs covered on the magnesium oxide support after plasma treatment is higher. Figure 4 The thermogravimetric data in the figure show that the plasma-treated magnesium oxide support has a greater weight loss after carbon nanotubes are grown, which means that more carbon nanotubes are grown.

[0019] Embodiment 2: A method for growing single-walled carbon nanotubes using an oxygen-deficient alumina-supported ruthenium metal catalyst comprises the following steps: (1) 3.0 g of alumina powder was placed in a vacuum tube furnace chamber, introduced into an argon atmosphere, the voltage was adjusted to 100 V, the current was adjusted to 3.0 A, and treated under glow discharge state for 0.5 h. After that, the power was turned off and the temperature was lowered to obtain alumina powder rich in oxygen vacancies.

[0020] (2) 0.1 g of RuCl3·3H2O was dissolved in deionized water to obtain a precursor solution. Then 2.0 g of magnesium oxide powder was added to the precursor solution and stirred on a magnetic stirrer for 4 h. The impregnated sample was then placed in an oven at 100 °C for 24 h to completely dry it and grind it into powder.

[0021] (3) Place the catalyst in a quartz boat, and place the quartz boat in the middle of a dual-temperature zone slide-type chemical vapor deposition furnace. Connect the experimental device as required, set the furnace temperature program to 20 °C / min, and introduce argon at a flow rate of 500 sccm to remove the air in the device. After the sample temperature reaches the preset temperature (600 °C-1000 °C), introduce carbon monoxide as the carbon source gas at a flow rate of 300 sccm for 30 min. After the reaction is completed, turn off the carbon monoxide gas and introduce argon. At the same time, stop heating and cool naturally to room temperature. Turn off the argon gas and take out the sample.

[0022] Embodiment 3: A method for growing single-walled carbon nanotubes using an oxygen-deficient magnesium oxide-supported nickel metal catalyst comprises the following steps: (1) 5.0 g of magnesium oxide powder was placed in a high-temperature tube furnace and argon gas was introduced at a flow rate of 500 sccm. After the temperature was raised to 600°C, it was treated in this state for 1.0 h. Then the power was turned off and the temperature was lowered to obtain magnesium oxide powder rich in oxygen vacancies.

[0023] (2) Dissolve 1.4 g Ni(NO3)2·6H2O in deionized water to obtain a precursor solution. Then add 4.0 g magnesium oxide powder into the precursor solution and stir on a magnetic stirrer for 4 h. Then, place the impregnated sample in an oven at 100 °C for 24 h to completely dry it and grind it into powder.

[0024] (3) Place the catalyst in a quartz boat, and place the quartz boat in the middle of a dual-temperature zone slide-type chemical vapor deposition furnace. Connect the experimental device as required, set the furnace temperature program to 20 °C / min, and introduce argon at a flow rate of 500 sccm to remove the air in the device. After the sample temperature reaches the preset temperature (700 °C-900 °C), introduce ethylene carbon source gas at a flow rate of 300 sccm for 20 min. After the reaction is completed, turn off the ethylene gas and introduce argon. At the same time, stop heating and cool naturally to room temperature. Turn off the argon and take out the sample.

Claims

1. A method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst, characterized in that: With the help of a variety of technical strategies, high specific surface area oxide powders are processed to prepare oxygen-deficient carriers rich in oxygen vacancies. Salt solutions containing metal ions are used as precursors, and supported metal catalysts are prepared through impregnation combined with high-temperature calcination strategies. Single-walled carbon nanotubes are grown on the catalyst using chemical vapor deposition technology.

2. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The various technical strategies described include heat treatment, chemical reduction, template strategy, and plasma.

3. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The oxide powder with high specific surface area includes any one or more combinations of silicon oxide, aluminum oxide and magnesium oxide.

4. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The salt solution containing metal ions is any one or more combinations of nitrates, chlorides and acetylacetone complexes of transition metal ions.

5. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The impregnation combined with high temperature calcination strategy refers to regulating the type of carrier, the type of metal salt, the calcination temperature and the calcination time.

6. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The supported metal catalyst is composited by oxygen-deficient oxide powder and transition metal nanoparticles.

7. The method for growing single-walled carbon nanotubes using an oxygen-deficient oxide-supported metal catalyst according to claim 1, characterized in that: The chemical vapor deposition technology refers to regulating carbon source components, gas flow, growth temperature and growth time.

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