CN114212774A - Efficient preparation method of single-walled carbon nanotube without metal catalyst residues - Google Patents

Efficient preparation method of single-walled carbon nanotube without metal catalyst residues Download PDF

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CN114212774A
CN114212774A CN202111538047.XA CN202111538047A CN114212774A CN 114212774 A CN114212774 A CN 114212774A CN 202111538047 A CN202111538047 A CN 202111538047A CN 114212774 A CN114212774 A CN 114212774A
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walled carbon
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carbon nanotube
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CN114212774B (en
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张莉莉
马瑞雪
刘畅
成会明
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Institute of Metal Research of CAS
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    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
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    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/78—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with alkali- or alkaline earth metals
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
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    • C01B2202/00—Structure or properties of carbon nanotubes
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    • Y02P20/584—Recycling of catalysts

Abstract

The invention relates to the field of controllable preparation of high-purity and high-density single-walled carbon nanotubes, in particular to an efficient preparation method of a single-walled carbon nanotube without metal catalyst residues. By adopting a chemical vapor deposition method, taking solid solution metal oxide as a catalyst precursor, and regulating and controlling the loading amount of active metal, the pretreatment condition of the catalyst and the growth process parameters of the carbon nano tube, on one hand, the high-activity metal catalyst is used for efficiently growing the carbon nano tube, on the other hand, the activity of the catalyst is regulated and controlled by regulating and controlling the interaction of the catalyst and a carrier, the catalyst is inactivated and separated from the carbon nano tube after the reaction is finished, and finally, a high-purity single-walled carbon nano tube sample without metal catalyst residue is obtained. Meanwhile, the solid solution catalyst has the characteristic of reproducibility, can realize the repeated growth of the carbon nano tube, and further improves the growth efficiency of the product. The invention directly and efficiently prepares the single-walled carbon nanotube without catalyst residue by utilizing the high activity of the metal catalyst and the interaction between the metal catalyst and the carrier.

Description

Efficient preparation method of single-walled carbon nanotube without metal catalyst residues
Technical Field
The invention relates to the field of controllable preparation of high-purity and high-density single-walled carbon nanotubes, in particular to an efficient preparation method of a single-walled carbon nanotube without metal catalyst residues.
Background
Due to its unique one-dimensional structure and excellent physicochemical properties, single-walled carbon nanotubes have been widely used in basic research and practical applications. Chemical Vapor Deposition (CVD) is the simplest and most effective method for controlling the growth of single-walled carbon nanotubes, and metal catalysts are widely used for the efficient growth of single-walled carbon nanotubes. However, the residual metal catalyst attached to single-walled carbon nanotubes has limited the study of its intrinsic properties (document 1Brukh, R., et al (2008). "Stabilizing single-walled carbon nanotubes by removal of residual metal catalysts", "Chemical Physics Letters 459(1): 149. 152.) and its application in the fields of electricity, magnetism, medicine, etc. (document 2 Lee, Y. -H., et al. (2006)" Magnetic catalyst catalysts and the infrared on the field electron emission spectroscopy analysis of low temperature carbon nanotubes. Applied Physics Letters 89(8): 083113). Although some non-metallic catalysts have been reported to grow single-walled carbon nanotubes, they are far less efficient than metallic catalysts.
At present, the preparation method of the carbon nano tube without catalyst residue has two methods of direct growth and post treatment. As a first method, Yan Zhang et al, Using volatile Pb as a catalyst, achieved the Direct Growth of randomly and horizontally aligned catalyst-free Single-Walled Carbon Nanotubes on a silicon substrate (document 3Zhang, Y., et al (2008). "Direct Growth of Single-Walled Carbon Nanotubes with out Metallic reagents by Using Lead as a catalyst" Chemistry of Materials 20(24): 7521-7525.). Carbon catalysts such as nanodiamond, C60Carbon nanotube chips have also been used as seeds for producing single-walled carbon nanotubes free of metal impurities (literature 4Sanchez-Valencia, j.r., et al (2014.) "Controlled synthesis of single-crystalline carbon nanotubes: Nature 512(7512): 61-64.). However, the yield of the carbon nanotubes prepared by the method is low, and the requirement of mass application cannot be met. The post-treatment method is to remove the residual catalyst by acid washing, short cutting, high temperature treatment, etc. of the prepared carbon nanotube, but the method inevitably introduces pollution and defects in the carbon nanotube sample, and it is difficult to completely remove the metal catalyst coated by the carbon layer, which is not good for the intrinsic property of the carbon nanotubeThe application of the method in high-end fields such as semiconductors is limited due to the exertion of the energy.
The direct growth of carbon nanotubes by using a high-activity metal catalyst is still an effective way for efficiently preparing high-quality carbon nanotubes, and how to recover and regulate the metal catalyst is the key point for realizing the preparation of the high-purity carbon nanotubes without catalyst residues.
Disclosure of Invention
The invention aims to provide an efficient preparation method of a single-walled carbon nanotube without metal catalyst residues, which solves the problem of influence of the catalyst residues on the intrinsic properties of the carbon nanotube, improves the utilization efficiency of the catalyst and obtains the single-walled carbon nanotube with high purity and high density.
The technical scheme of the invention is as follows:
a high-efficiency preparation method of a single-walled carbon nanotube without metal catalyst residues is characterized in that a metal oxide solid solution is used as a catalyst precursor, a chemical vapor deposition method is adopted, and the single-walled carbon nanotube without metal catalyst residues is prepared through growth and post-treatment, and the high-efficiency repeated preparation of the single-walled carbon nanotube without the catalyst residues is realized by utilizing the characteristic that the catalyst precursor is reproducible, and the specific steps are as follows:
(1) mixing catalytically active metal particles, which are metal atoms or metal ions, with an oxide carrier by using a physical and chemical method, and then carrying out high-temperature heat treatment to obtain a solid solution catalyst precursor loaded with active metals;
(2) putting the solid solution catalyst precursor into a quartz boat, carrying out reduction pretreatment in a CVD furnace to separate out active metal atoms to obtain catalyst nano particles, and then introducing a carbon source to grow the carbon nano tube;
(3) switching the carbon source into vacuum or inert atmosphere to terminate the growth of the carbon nano tube, cooling under the same condition, or introducing oxidizing atmosphere at lower temperature, and carrying out post-treatment on the product to obtain the single-walled carbon nano tube without catalyst residue;
and (4) repeating the step (2) and the step (3), and growing the carbon nano tube by using the catalyst precursor for more than two times to efficiently obtain the carbon nano tube without catalyst residues.
The high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue is characterized in that solute atoms or ions in the metal oxide solid solution are dissolved into a carrier under the driving of an external field, and the two modes of replacing atoms in the carrier or dissolving into the gaps of carrier atoms are included; or solute atoms or ions diffuse away from the carrier under the action of an external field and form nano-scale particles; solute atoms in the solid solution catalyst precursor are catalytically active metal atoms for carbon nanotube growth, including Fe, Co, or Ni.
The high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue is characterized in that: in one aspect, the catalyst is active in catalyzing the growth of single-walled carbon nanotubes; on the other hand, the catalyst has the regenerable characteristic, so that the growth of the single-walled carbon nanotube is realized for more than two times, and the use efficiency of the catalyst is improved.
The high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue regulates and controls the diffusion recovery capability of the catalytic active metal particles relative to the carrier to realize no metal catalyst residue, directly obtains the single-walled carbon nanotube by controlling the growth conditions through a one-step method, or indirectly obtains the single-walled carbon nanotube by introducing other energy action modes through a two-step method.
The efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue adopts a direct preparation method, adopts carbon-containing gas as a reducing agent and a carbon source at the same time, and grows the carbon nanotube for 3-5 min at the low temperature of 700-750 ℃ and the pressure of 5-8 kPa, wherein the carbon-containing gas comprises but is not limited to CO or ethanol steam; the two-step process is an indirect preparation process, in which the grown carbon nanotubes are post-treated, including but not limited to low-temperature oxidation, inert atmosphere annealing or electron beam irradiation, to dissolve the catalyst in the carrier.
According to the efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue, the diameter of the obtained single-walled carbon nanotube is distributed in the range of 0.5-3 nm, and no metal nanoparticles are left at two ends of the carbon nanotube.
According to the efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue, the catalyst precursor is metal oxide powder, a thin film or a processed commercial substrate, and has high-temperature stability, and a relatively stable crystal structure is kept at the growth temperature range of 700-1000 ℃ of the carbon tube.
According to the efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue, in the step (1), the loading amount of catalytic active metal in the catalyst precursor is within the range of 0.1-5 mol%.
In the high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue, in the step (2), the atmosphere for the reduction pretreatment of the catalyst precursor is carbon-containing atmosphere hydrogen, CO or ethanol steam; after reduction pretreatment, the size of the precipitated catalyst is within the range of 0.5-3 nm; controlling the growth process parameters of the carbon nano tube: the temperature is 700-900 ℃, and the time is 3-15 min.
The efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue comprises the step (3) of introducing air at a low temperature of 300-400 ℃ as an oxidizing atmosphere to carry out heat treatment on a product.
The design idea of the invention is as follows:
according to the method, solid solution metal oxide is used as a catalyst precursor, and the loading capacity of an active metal catalyst, the pretreatment condition of the catalyst, the growth process parameters (temperature, atmosphere, carbon source type and concentration) of the carbon nano tube and the like are regulated, so that the carbon nano tube efficiently grows by using the metal catalyst on one hand, the diffusion capacity of the catalyst relative to a carrier is regulated on the other hand, metal particles are separated from the carbon nano tube after the reaction is finished, and finally, a high-purity single-walled carbon nano tube sample without metal catalyst residues is directly obtained. Meanwhile, the reproducible characteristic of the solid solution catalyst is utilized to realize the multiple growth of the carbon nano tube and efficiently obtain the single-wall carbon nano tube without metal catalyst residues.
The invention has the advantages and beneficial effects that:
1. the invention provides a controllable and repeatable preparation method of single-walled carbon nano tubes without metal catalyst residues, which solves the problem of catalyst residues in the growth process of carbon nano tubes and improves the utilization efficiency of the catalyst.
2. The invention designs a solid solution catalyst system which can effectively regulate the precipitation and dissolution processes of the catalyst in a carrier.
3. The invention provides a plurality of post-treatment methods, which promote the catalyst to be dissolved into the carrier and reduce the residual rate of the metal catalyst in the carbon nano tube sample.
4. The single-walled carbon nanotube obtained by the invention has higher purity and density, and is expected to promote the application of the carbon nanotube in the fields of medical treatment, magnetics, electronics and the like.
Drawings
FIG. 1 is a schematic flow chart of the preparation of single-walled carbon nanotubes without metal catalyst residues.
FIG. 2 is a structural schematic diagram and a high-power transmission electron micrograph of a grown single-walled carbon nanotube without catalyst residues: (a) one end is sealed; (b) sealing two ends;
fig. 3, (a) a topographical view of a precursor of a catalyst before growing carbon nanotubes; (b) a topography of the grown carbon nanotubes; (c) controlling the condition to directly grow the morphology of the catalyst without catalyst residue on the carbon tube. (d) Controlling and preparing a morphology graph of the carbon nano tube without catalyst residue obtained by combining high-temperature annealing treatment.
FIG. 4 is a diagram of the process of dissolving metal catalyst nanoparticles into a carrier under the irradiation of electron beams.
FIG. 5 is a scanning electron micrograph and a Raman spectrum of a sample of the carbon nanotube after the first growth (a-c) and the second growth (d-f).
Detailed Description
In a specific implementation process, the device for growing the carbon nanotubes without catalyst residues comprises the following steps: a carbon nanotube growth system and a vacuum system. By adopting a chemical vapor deposition method, taking solid solution metal oxide as a catalyst precursor, regulating and controlling the loading capacity of active metal, the pretreatment condition of the catalyst and the growth process parameters (temperature, atmosphere, carbon source type, concentration and the like) of the carbon nano tube, on one hand, the high-activity metal catalyst is utilized to efficiently grow the carbon nano tube, on the other hand, the activity of the catalyst is regulated and controlled, the catalyst is inactivated and separated from the carbon nano tube after the reaction is finished, and finally, a single-walled carbon nano tube sample with high purity (the two end ports and the tube wall of the carbon nano tube are represented by a TEM, no catalyst is used, the theoretical purity can reach 100 percent) and high density (the yield of the repeatedly grown carbon tube can reach more than 1.4 times of that of one-time growth, and the sample is different depending on the growth conditions) without metal catalyst residue is obtained. Meanwhile, the reproducible characteristic of the solid solution catalyst is utilized to realize the multiple growth of the carbon nano tube and efficiently obtain the single-wall carbon nano tube without metal catalyst residues.
The invention adopts a solid solution catalyst precursor to carry out the high-efficiency preparation of the metal-free catalyst single-walled carbon nanotube, taking Co-MgO (metal-oxide) solid solution as an example, the specific preparation method of the catalyst precursor is as follows: putting basic magnesium carbonate in a muffle furnace (300-500 ℃) and heating for 1-2 hours to thermally decompose the basic magnesium carbonate to obtain magnesium oxide powder; dissolving a certain proportion of metal salt (cobalt nitrate) in water or ethanol solution, and then adding a proper amount of magnesium oxide powder to be fully and ultrasonically stirred uniformly; thirdly, placing the uniformly dispersed solution in an oven (60-90 ℃) for drying; fourthly, taking out the dried massive sample, grinding the massive sample into powder, and then putting the powder into a muffle furnace (800-1000 ℃) to sinter for 3-20 hours; and fifthly, grinding the sintered powder for 10-15 min again for growing the carbon nano tube. (reference: He, M., et al (2013). "Chiral-Selective Growth of Single-wave Carbon Nanotubes on Cotton-MismatchechedEpitaxy Cobalt nanoparticles" Scientific Reports 3(1):1460.)
As shown in fig. 1, the present invention provides a method for efficiently preparing single-walled carbon nanotubes without metal catalyst residues, which comprises the following specific steps:
directly controlling the preparation process: heating the tube furnace to a target temperature, after stabilizing for a period of time, pushing the quartz boat with the solid solution catalyst into a constant temperature area inside the furnace tube, vacuumizing a cavity of the furnace tube, introducing CO gas to stabilize the pressure in the tube at 5-8 kPa, keeping for 5min, closing the CO gas, evacuating residual CO in the tube, introducing Ar gas to raise the pressure in the tube to normal pressure, and pushing out the quartz boat for cooling.
Controlling the preparation and combining the post-treatment process: heating the tube furnace to a target temperature, stabilizing for a period of time, placing the quartz boat with the catalyst in a low-temperature region in the furnace tube, introducing 200-400 sccm of inert gas Ar for 5min to exhaust the air in the furnace tube, pushing the quartz boat into a constant-temperature region, continuing introducing argon for stabilization for 5min, introducing 200sccm of hydrogen for reduction, introducing ethanol by using 100sccm of argon as a carrier gas, growing the carbon nanotube by using 100sccm of argon as a buffer gas for 15min, closing the carbon source gas after the reduction, pushing the quartz boat out, and cooling under the protection of argon.
The following post-treatment methods are concretely: oxidizing a grown carbon nano tube sample at 300-400 ℃ for 10-30 min, and driving a catalyst to dissolve in a carrier through weak oxidation; secondly, placing the grown carbon nano tube sample in an inert atmosphere for heat treatment for 1-2 h, and dissolving the catalyst into the carrier through thermal diffusion drive; thirdly, irradiating the sample by electron beams in vacuum to promote the catalyst to be dissolved in the carrier.
The specific method for repeatedly preparing the carbon nanotube without catalyst residue for two or more times based on the first growth is the same as the first preparation method.
As shown in fig. 2, the single-walled carbon nanotube without metal catalyst residue prepared by the present invention has a structure with one end sealed or both ends sealed, and both ends have no catalyst residue.
The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples.
Example 1
In the embodiment, 100g of basic magnesium carbonate is placed in a muffle furnace for heat treatment at 400 ℃ for 1h to obtain magnesium oxide powder; dissolving 1.4g of cobalt nitrate in 50ml of water solution, uniformly stirring, weighing 4g of magnesium oxide powder, pouring the magnesium oxide powder into the cobalt nitrate salt solution, and ultrasonically stirring for 30 min; drying the mixed solution in an oven at 90 ℃, and grinding the obtained block into powder; calcining the powder in a muffle furnace at 1000 ℃ for 20h to obtain a Co-MgO solid solution catalyst with the Co content of 5 mol%; and grinding the sintered powder for 10-20 min for preparing the carbon nano tube. The morphology of the prepared solid solution catalyst is shown in figure 3(a), and the surface is smooth and has no particles.
Heating the tube furnace to 725 ℃ for stabilization for 30min, placing the quartz boat containing 2mg of solid solution catalyst in a constant temperature area in the furnace tube, vacuumizing the cavity of the furnace tube to 1Pa, introducing CO gas to stabilize the pressure in the tube to 7-8 kPa, keeping for 5min, closing the CO gas, evacuating the residual CO in the tube, introducing Ar gas to raise the pressure in the tube to normal pressure, pushing out the quartz boat for cooling.
The obtained carbon nanotubes were characterized by their morphology and catalyst residue rate by TEM, as shown in fig. 3 (c): sparser single-walled carbon nanotubes are grown, metal nanoparticles are hardly visible on the solid solution catalyst, and the diameter of the single-walled carbon nanotube is 1-3 nm.
Comparative example
In this example, a solid solution catalyst having a Co loading of 5 mol% as described in example 1 was used.
Heating the tube furnace to 700 ℃ and stabilizing for 30min, placing the quartz boat with 2mg of solid solution catalyst in a constant temperature area in the furnace tube, introducing 100sccm CO gas to normal pressure, keeping for 10min, closing the CO gas, switching to 300sccm Ar, pushing out the quartz boat and cooling.
The obtained carbon nanotubes were characterized by their morphology and catalyst residue rate by TEM, as shown in fig. 3 (b): the single-walled carbon nanotube is grown, the metal nanoparticles are more in residue and distributed on the carbon nanotube and the solid solution catalyst, and the diameter of the single-walled carbon nanotube is 0.5-3 nm.
Example 2
In this example, a Co-MgO solid solution catalyst having a metal loading of 2 mol% was prepared by the catalyst preparation method described in example 1.
Heating a tube furnace to 900 ℃, stabilizing for 30min, placing a quartz boat with a catalyst in a low-temperature region in the furnace tube, introducing argon of 200-400 sccm for 5min to exhaust air in the furnace tube, pushing the quartz boat into a constant-temperature region, continuing introducing argon for 5min, introducing hydrogen of 200sccm, reducing for 22min, introducing ethanol by using argon of 100sccm as carrier gas, growing carbon nanotubes by using argon of 100sccm as buffer gas for 15min, closing a carbon source gas after finishing, performing heat treatment under the protection of argon for 1.5h, and then pushing out for cooling.
The obtained carbon nanotubes were characterized by their morphology and catalyst residue rate by TEM, as shown in fig. 3 (d): more single-walled carbon nanotube bundles grow, metal nanoparticles are hardly visible on the solid solution catalyst, and the diameter of the single-walled carbon nanotube is 0.5-3 nm.
Example 3
In this example, a solid solution catalyst having a Co loading of 5 mol% as described in example 1 was used.
Heating the tube furnace to 900 ℃, stabilizing for 30min, placing the quartz boat with the catalyst in a low-temperature region in the furnace tube, introducing argon gas of 200-400 sccm for 5min to exhaust the air in the furnace tube, pushing the quartz boat into a constant-temperature region, continuing introducing argon gas to stabilize for 5min, introducing ethanol by using argon gas of 50sccm as carrier gas, introducing hydrogen gas of 100sccm to reduce and grow the carbon nanotube for 3min, closing the carbon source gas after the reduction, and pushing out under the protection of argon gas to reduce the temperature. Placing in a transmission electron microscope (environmental pressure is less than 10)-5Pa, electron beam dose:
Figure BDA0003413126470000061
) And irradiating the catalyst with electron beams for 10-20 min, as shown in FIG. 4, so that most of the metal nanoparticles are dissolved in the carrier. More single-walled carbon nanotube bundles grow, metal nanoparticles are hardly visible on the solid solution catalyst, and the diameter of the single-walled carbon nanotube is 0.5-3 nm.
Example 4
In this example, a solid solution catalyst having a Co loading of 5 mol% as described in example 1 was used.
Placing 2mg of solid solution catalyst in 5ml of ethanol solution, performing ultrasonic dispersion uniformly, sucking the catalyst suspension by using a dropper, dropwise adding the catalyst suspension on a 5mm by 5mm silicon wafer, and placing the silicon wafer in an oven for drying for later use. Heating the tube furnace to 900 ℃, stabilizing for 30min, placing the silicon wafer with the catalyst in a low-temperature region in a quartz boat, pushing the quartz boat into the furnace tube, exhausting air in the furnace tube after 5min by introducing 200-400 sccm argon, then pushing the quartz boat into a constant-temperature region, continuously introducing the argon for stabilizing for 5min, then introducing 200sccm hydrogen, reducing for 30min, introducing ethanol by using 100sccm argon as carrier gas, growing the carbon nanotube by using 100sccm argon as buffer gas for 15min, closing the carbon source gas after finishing, carrying out heat treatment under the protection of argon for 1.5h, and then pushing out for cooling. Scanning electron microscopy and Raman characterization of the silicon wafer on which the carbon nanotubes grow are shown in FIGS. 5 (a-c).
The above-mentioned step of growing carbon nanotubes is repeated, and the carbon nanotubes are grown for the second time by using the solid solution catalyst on the silicon wafer, and the obtained result is shown in fig. 5(d-f), and the scanning photograph and the raman spectrum both show that the density of the carbon nanotubes after the second growth is increased, which is about 1.4 times of the yield of the carbon nanotubes after the first growth. More single-walled carbon nanotube bundles grow, metal nanoparticles are hardly visible on the solid solution catalyst, and the diameter of the single-walled carbon nanotube is 0.5-3 nm.
The embodiment result shows that the invention directly and efficiently prepares the single-walled carbon nanotube without catalyst residue by utilizing the high activity of the metal catalyst and the interaction between the metal catalyst and the carrier, improves the utilization efficiency of the catalyst, avoids the influence of the metal catalyst residue on the performance of the carbon nanotube, and is expected to promote the practical application of the carbon nanotube in the fields of electronic devices, biological medical treatment and the like.

Claims (10)

1. A high-efficiency preparation method of a single-walled carbon nanotube without metal catalyst residues is characterized in that a metal oxide solid solution is used as a catalyst precursor, a chemical vapor deposition method is adopted, and the single-walled carbon nanotube without metal catalyst residues is prepared through growth and post-treatment, and the high-efficiency repeated preparation of the single-walled carbon nanotube without catalyst residues is realized by utilizing the reproducible characteristic of the catalyst precursor, and the specific steps are as follows:
(1) mixing catalytically active metal particles, which are metal atoms or metal ions, with an oxide carrier by using a physical and chemical method, and then carrying out high-temperature heat treatment to obtain a solid solution catalyst precursor loaded with active metals;
(2) putting the solid solution catalyst precursor into a quartz boat, carrying out reduction pretreatment in a CVD furnace to separate out active metal atoms to obtain catalyst nano particles, and then introducing a carbon source to grow the carbon nano tube;
(3) switching the carbon source into vacuum or inert atmosphere to terminate the growth of the carbon nano tube, cooling under the same condition, or introducing oxidizing atmosphere at lower temperature, and carrying out post-treatment on the product to obtain the single-walled carbon nano tube without catalyst residue;
and (4) repeating the step (2) and the step (3), and growing the carbon nano tube by using the catalyst precursor for more than two times to efficiently obtain the carbon nano tube without catalyst residues.
2. The method for efficiently preparing the single-walled carbon nanotube without the metal catalyst residue according to claim 1, wherein solute atoms or ions in the metal oxide solid solution are dissolved into the carrier under the driving of an external field, and the two modes comprise replacing atoms in the carrier or dissolving into gaps among carrier atoms; or solute atoms or ions diffuse away from the carrier under the action of an external field and form nano-scale particles; solute atoms in the solid solution catalyst precursor are catalytically active metal atoms for carbon nanotube growth, including Fe, Co, or Ni.
3. The method for efficiently preparing single-walled carbon nanotubes without residual metal catalyst according to claim 1, wherein the efficient preparation is embodied by: in one aspect, the catalyst is active in catalyzing the growth of single-walled carbon nanotubes; on the other hand, the catalyst has the regenerable characteristic, so that the growth of the single-walled carbon nanotube is realized for more than two times, and the use efficiency of the catalyst is improved.
4. The method for efficiently preparing single-walled carbon nanotubes without metal catalyst residues as claimed in claim 1, wherein the metal catalyst residues are realized by controlling the diffusion recovery ability of catalytically active metal particles relative to a carrier, and the single-walled carbon nanotubes are directly obtained by controlling the growth conditions in a one-step method, or are indirectly obtained by introducing other energy action modes in a two-step method.
5. The method for efficiently preparing the single-walled carbon nanotube without the metal catalyst residue according to claim 4, wherein the one-step method is a direct preparation method, carbon-containing gas is adopted as a reducing agent and a carbon source at the same time, the carbon-containing gas comprises but is not limited to CO or ethanol steam, and the carbon nanotube grows for 3-5 min at the lower temperature of 700-750 ℃ and the pressure of 5-8 kPa; the two-step process is an indirect preparation process, in which the grown carbon nanotubes are post-treated, including but not limited to low-temperature oxidation, inert atmosphere annealing or electron beam irradiation, to dissolve the catalyst in the carrier.
6. The method for efficiently preparing single-walled carbon nanotubes without metal catalyst residues as claimed in claim 1, wherein the diameter of the obtained single-walled carbon nanotubes is within the range of 0.5 to 3nm, and no metal nanoparticles are left at both ends of the carbon nanotubes.
7. The method for efficiently preparing single-walled carbon nanotubes without metal catalyst residues as claimed in claim 1, wherein the catalyst precursor is a metal oxide powder, a thin film or a treated commercial substrate, and has high temperature stability and maintains a relatively stable crystal structure in the carbon tube growth temperature range of 700 to 1000 ℃.
8. The method for efficiently preparing the single-walled carbon nanotube without the residual metal catalyst according to claim 1, wherein in the step (1), the loading amount of the catalytic active metal in the catalyst precursor is in the range of 0.1-5 mol%.
9. The method for efficiently preparing single-walled carbon nanotubes without metal catalyst residues according to claim 1, wherein in the step (2), the atmosphere for the reductive pretreatment of the catalyst precursor is a carbon-containing atmosphere of hydrogen, CO or ethanol vapor; after reduction pretreatment, the size of the precipitated catalyst is within the range of 0.5-3 nm; controlling the growth process parameters of the carbon nano tube: the temperature is 700-900 ℃, and the time is 3-15 min.
10. The method for efficiently preparing single-walled carbon nanotubes without residual metal catalyst as claimed in claim 1, wherein in the step (3), air is introduced at a low temperature of 300-400 ℃ as an oxidizing atmosphere to heat-treat the product.
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