CN114212774B - Efficient preparation method of single-walled carbon nanotubes without metal catalyst residues - Google Patents

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

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CN114212774B
CN114212774B CN202111538047.XA CN202111538047A CN114212774B CN 114212774 B CN114212774 B CN 114212774B CN 202111538047 A CN202111538047 A CN 202111538047A CN 114212774 B CN114212774 B CN 114212774B
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walled carbon
carbon nanotubes
carbon nanotube
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CN114212774A (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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    • C01—INORGANIC CHEMISTRY
    • 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
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/162—Preparation characterised by catalysts
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
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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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • 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
    • C01B32/158—Carbon nanotubes
    • C01B32/159—Carbon nanotubes single-walled
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/02—Single-walled nanotubes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/30—Purity
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/584—Recycling of catalysts

Abstract

The invention relates to the controllable preparation field of high-purity and high-density single-walled carbon nanotubes, in particular to a high-efficiency preparation method of a single-walled carbon nanotube without metal catalyst residues. The method is characterized in that a chemical vapor deposition method is adopted, solid solution metal oxide is used as a catalyst precursor, active metal loading, catalyst pretreatment conditions and carbon nanotube growth technological parameters are regulated and controlled, on one hand, a high-activity metal catalyst is utilized to grow carbon nanotubes efficiently, on the other hand, the activity of the catalyst is regulated and controlled through regulating and controlling the catalyst-carrier interaction, after the reaction is finished, the catalyst is deactivated and separated from the carbon nanotubes, and finally, a high-purity single-walled carbon nanotube sample without metal catalyst residues is obtained. Meanwhile, the solid solution catalyst has the characteristic of being renewable, can realize the multiple 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 of the metal catalyst and the carrier.

Description

Efficient preparation method of single-walled carbon nanotubes without metal catalyst residues
Technical Field
The invention relates to the controllable preparation field of high-purity and high-density single-walled carbon nanotubes, in particular to a high-efficiency preparation method of a single-walled carbon nanotube without metal catalyst residues.
Background
Single-walled carbon nanotubes have found wide application in basic research and practical applications due to their unique one-dimensional structure and excellent physicochemical properties. Chemical Vapor Deposition (CVD) is the simplest and effective method of controlling single-walled carbon nanotube growth, with metal catalysts being widely used to efficiently grow single-walled carbon nanotubes. However, the residual metal catalyst attached to the single-walled carbon nanotubes limits 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 use in the fields of electricity, magnetism, medicine, etc. (document 2 lee, y. —h.," et al (2006), "Magnetic catalyst residues and their influence on the field electron emission characteristics of low temperature grown carbon nanotubes.," Applied Physics Letters 89 (8): 083113.). Although some nonmetallic catalysts have been reported to grow single-walled carbon nanotubes, their efficiency is far lower than metallic catalysts.
At present, the preparation method of the carbon nano tube without catalyst residue comprises direct growth andand (5) two types of post-treatment. For the first method, yan Zhang et al used volatile Pb as a catalyst to achieve the direct growth of random 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 without Metallic Residues by Using Lead as a catalyst.," Chemistry of Materials (24): 7521-7525). Carbon catalysts such as nanodiamond, C 60 Carbon nanotube chips have also been used as seeds to produce single-walled carbon nanotubes free of metallic impurities (document 4Sanchez-Valencia, j.r., et al (2014), "Controlled synthesis of single-chirality carbon nanotubes.," Nature 512 (7512): 61-64). However, the yield of the carbon nanotubes prepared by the method is very low, and the requirements of macro applications cannot be met. The post-treatment method is to carry out acid washing, chopping, high-temperature treatment and the like on the prepared carbon nano tube to remove the residual catalyst, but the method inevitably introduces pollution and defects into the carbon nano tube sample, and the metal catalyst coated by the carbon layer is difficult to completely remove, which is not beneficial to exerting the intrinsic performance of the carbon nano tube and limits the application of the carbon nano tube in high-end fields such as semiconductors.
The direct growth of carbon nanotubes by using a high-activity metal catalyst is still an effective way to efficiently prepare high-quality carbon nanotubes, and how to recycle and regulate the metal catalyst is a key point for preparing high-purity carbon nanotubes without catalyst residues.
Disclosure of Invention
The invention aims to provide a high-efficiency preparation method of a single-walled carbon nanotube without metal catalyst residues, which solves the problem that the catalyst residues affect the intrinsic properties of the carbon nanotube and improves the utilization efficiency of the catalyst, thereby obtaining the single-walled carbon nanotube with high purity and high density.
The technical scheme of the invention is as follows:
the high-efficiency preparation method of the single-walled carbon nanotube without metal catalyst residue takes a metal oxide solid solution as a catalyst precursor, adopts a chemical vapor deposition method, prepares the single-walled carbon nanotube without metal catalyst residue through growth and post-treatment, and realizes the high-efficiency repeated preparation of the single-walled carbon nanotube without catalyst residue by utilizing the characteristic of renewable catalyst precursor, and the specific steps are as follows:
(1) The method comprises the steps of mixing catalytic active metal particles which are metal atoms or metal ions with an oxide carrier by using a physical chemistry method, and then carrying out high-temperature heat treatment to obtain a solid solution catalyst precursor loaded with active metal;
(2) Placing a solid solution catalyst precursor into a quartz boat, performing 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 carbon nanotubes;
(3) Switching a carbon source into vacuum or inert atmosphere to stop the growth of the carbon nano tube, cooling under the same condition, or introducing oxidizing atmosphere at a lower temperature, and performing post-treatment on the product to obtain the single-walled carbon nano tube without catalyst residues;
and (3) 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 obtain the carbon nano tube without catalyst residues.
The high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue comprises the steps that solute atoms or ions in a 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 the carrier atoms are included; alternatively, solute atoms or ions diffuse away from the carrier under the action of an external field and form nanoscale 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 metal catalyst residue is characterized in that: in one aspect, the catalyst has the activity of catalyzing the growth of single-walled carbon nanotubes; on the other hand, the catalyst has the characteristic of regeneration, realizes more than two times of growth of the single-walled carbon nanotubes, and improves the service efficiency of the catalyst.
According to the efficient preparation method of the single-walled carbon nanotube without the metal catalyst residue, the diffusion recovery capacity of the catalytic active metal particles relative to the carrier is regulated to realize the metal catalyst residue-free, the single-walled carbon nanotube is directly obtained by controlling the growth condition through a one-step method, or the single-walled carbon nanotube is indirectly obtained by introducing other energy action modes through a two-step method.
The high-efficiency preparation method of the single-wall carbon nano tube without metal catalyst residue comprises the steps of adopting a one-step method as a direct preparation method, adopting carbon-containing gas as a reducing agent and a carbon source, and growing the carbon nano tube for 3-5 min at a lower temperature of 700-750 ℃ and a pressure of 5-8 kPa, wherein the carbon-containing gas comprises but is not limited to CO or ethanol steam; the two-step method is an indirect preparation method, and the post-treatment of the grown carbon nanotubes is performed, wherein the post-treatment comprises, but is not limited to, low-temperature oxidation, inert atmosphere annealing or electron beam irradiation method, so that the catalyst is dissolved 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 within the range of 0.5-3 nm, and no metal nano particles remain at the 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 powder, thin film or treated commercial substrate of metal oxide, has high-temperature stability, and maintains a relatively stable crystal structure in a carbon tube growth temperature range of 700-1000 ℃.
In the high-efficiency preparation method of the single-walled carbon nanotube without the metal catalyst residue, 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 percent.
In the step (2), the atmosphere for the reduction pretreatment of the catalyst precursor is carbon-containing atmosphere hydrogen, CO or ethanol steam; after the reduction pretreatment, the size of the precipitated catalyst is within the range of 0.5-3 nm; controlling the technological parameters of carbon nanotube growth: the temperature is 700-900 ℃ and the time is 3-15 min.
In the step (3), air is introduced at a low temperature of 300-400 ℃ to serve as an oxidizing atmosphere, and the product is subjected to heat treatment.
The design idea of the invention is as follows:
according to the invention, solid solution metal oxide is used as a catalyst precursor, and the active metal catalyst loading, the pretreatment condition of the catalyst, the growth technological parameters (temperature, atmosphere, carbon source type and concentration) of the carbon nanotube and the like are regulated, so that on one hand, the carbon nanotube is efficiently grown by using the metal catalyst, on the other hand, the diffusion capacity of the catalyst relative to the carrier is regulated, and after the reaction is finished, metal particles are separated from the carbon nanotube, and finally, the high-purity single-wall carbon nanotube sample without metal catalyst residues is directly obtained. Meanwhile, the characteristic that the solid solution catalyst can be regenerated is utilized to realize the repeated growth of the carbon nano tube, and the single-wall carbon nano tube without metal catalyst residues is efficiently obtained.
The invention has the advantages and beneficial effects that:
1. the invention provides a controllable and repeatable preparation method of single-walled carbon nano without metal catalyst residue, which solves the problem of catalyst residue 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 various post-treatment methods, which promote the dissolution of the catalyst into the carrier and reduce the residual rate of the metal catalyst in the carbon nano tube sample.
4. The single-wall carbon nano tube obtained by the invention has higher purity and density, and is expected to promote the application of the carbon nano tube in the fields of medical treatment, magnetism, electronics and the like.
Drawings
FIG. 1 is a schematic flow chart of a process for preparing single-walled carbon nanotubes without metal catalyst residues.
FIG. 2 is a schematic structural diagram of a grown single-walled carbon nanotube without catalyst residue and a high power transmission electron microscope photograph: (a) one end is sealed; (b) sealing the two ends;
FIG. 3 (a) a topography of a procatalyst precursor for growing carbon nanotubes; (b) a topography after carbon nanotube growth; (c) And controlling the condition to directly grow the catalyst morphology graph after the carbon tube without catalyst residue. (d) And controlling and preparing the morphology graph of the carbon nano tube without catalyst residues, which is obtained by combining high-temperature annealing treatment.
FIG. 4 is a diagram showing the process of dissolving metal catalyst nano-particles into a carrier under the irradiation of electron beams.
FIG. 5 scanning electron microscope photograph and Raman spectrum of the carbon nanotube sample 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 nano tube without catalyst residues comprises: a carbon nanotube growth system and a vacuum system. The method is characterized in that a chemical vapor deposition method is adopted, solid solution metal oxide is used as a catalyst precursor, and the carbon nano tube is efficiently grown by utilizing a high-activity metal catalyst on one hand and the activity of the catalyst is regulated and controlled on the other hand by regulating and controlling the loading capacity of active metal, the pretreatment condition of the catalyst, the growth process parameters (temperature, atmosphere, carbon source type, concentration and the like) of the carbon nano tube, so that the catalyst is deactivated and separated from the carbon nano tube after the reaction is finished, and finally, a single-wall carbon nano tube sample without metal catalyst residues is obtained (the ports and the tube walls at the two ends of the carbon nano tube are characterized by TEM, the catalyst is not arranged, the theoretical purity can reach 100 percent, and the yield of the repeatedly grown carbon nano tube can reach more than 1.4 times of that of one-time growth, and is different depending on the growth conditions). Meanwhile, the characteristic that the solid solution catalyst can be regenerated is utilized to realize the repeated growth of the carbon nano tube, and the single-wall carbon nano tube without metal catalyst residues is efficiently obtained.
The invention adopts solid solution catalyst precursor to carry out high-efficiency preparation of metal-free catalyst single-wall carbon nano tubes, taking Co-MgO (metal-oxide) solid solution system as an example, the specific preparation method of the catalyst precursor is as follows: (1) placing basic magnesium carbonate into a muffle furnace (300-500 ℃) and heating for 1-2 hours to thermally decompose the basic magnesium carbonate to obtain magnesium oxide powder; (2) dissolving a certain proportion of metal salt (cobalt nitrate) in water or ethanol solution, then adding a proper amount of magnesium oxide powder, and fully and ultrasonically stirring uniformly; (3) placing the uniformly dispersed solution into an oven (60-90 ℃) for drying; (4) taking out the dried block sample, grinding into powder, and then putting the powder into a muffle furnace (800-1000 ℃) to sinter for 3-20 hours; (5) the sintered powder is ground again for 10-15 min for growing the carbon nanotubes. ( Reference is made to: he, m., et al (2013), "chip-Selective Growth of Single-Walled Carbon Nanotubes on Lattice-MismatchedEpitaxial Cobalt nanomarticles.," Scientific Reports 3 (1): 1460. )
As shown in FIG. 1, the invention provides a high-efficiency preparation method of single-walled carbon nanotubes without metal catalyst residues, which comprises the following specific preparation processes:
the preparation process is directly controlled: heating a tube furnace to a target temperature, stabilizing for a period of time, pushing a quartz boat containing a solid solution catalyst into a constant temperature area inside the furnace tube, vacuumizing a furnace tube cavity, introducing CO gas, stabilizing the pressure inside the tube at 5-8 kPa, keeping for 5min, closing the CO gas, pumping residual CO in the tube, introducing Ar gas, raising the pressure inside the tube to normal pressure, pushing the quartz boat out, and cooling.
Control the preparation and post-treatment process: heating a tube furnace to a target temperature, stabilizing for a period of time, placing a quartz boat with a catalyst in a low-temperature area inside the furnace tube, introducing 200-400 sccm inert gas Ar gas for 5min to exhaust air in the furnace tube, pushing the quartz boat into the constant-temperature area, continuing introducing argon gas for stabilizing for 5min, introducing 200sccm hydrogen gas for reduction, introducing ethanol by using 100sccm argon gas as carrier gas, using 100sccm argon gas as buffer gas for growing carbon nanotubes for 15min, closing carbon source gas after the completion, pushing out the quartz boat, and cooling under the protection of argon gas.
The post-treatment methods specifically comprise: (1) oxidizing the grown carbon nanotube sample at 300-400 ℃ for 10-30 min, and driving the catalyst to dissolve into the carrier through weak oxidation; (2) placing the grown carbon nano tube sample in inert atmosphere for heat treatment for 1-2 h, and dissolving a catalyst into a carrier through thermal diffusion driving; (3) the sample was irradiated with an electron beam in vacuo to promote dissolution of the catalyst into the support.
The specific method for preparing the carbon nano tube without catalyst residue based on the secondary and repeated times of the primary growth is the same as the primary preparation method.
As shown in FIG. 2, the structure of the single-walled carbon nanotube without the metal catalyst residue prepared by the invention is one-end sealing or two-end sealing, and the two ends have no catalyst residue.
The present invention will be described in more detail by way of specific examples, but the scope of the present invention is not limited to these examples.
Example 1
In this example, 100g of basic magnesium carbonate was placed in a muffle furnace at 400℃for heat treatment for 1 hour to obtain magnesium oxide powder; 1.4g of cobalt nitrate is dissolved in 50ml of water solution and stirred uniformly, 4g of magnesium oxide powder is weighed and poured into the salt solution of cobalt nitrate, and ultrasonic stirring is carried out for 30min; drying the mixed solution in an oven at 90 ℃, and grinding the obtained block into powder; placing the powder into a muffle furnace, and calcining at 1000 ℃ for 20 hours to obtain a Co-MgO solid solution catalyst with Co content of 5 mol%; grinding the sintered powder for 10-20 min to prepare the carbon nano tube. The morphology of the prepared solid solution catalyst is shown in fig. 3 (a), and the surface is smooth and particle-free.
Heating the tube furnace to 725 ℃ for stabilization for 30min, placing a quartz boat containing 2mg of solid solution catalyst in a constant temperature area inside the furnace tube, vacuumizing the cavity of the furnace tube to 1Pa, introducing CO gas to stabilize the pressure inside the tube at 7-8 kPa, maintaining for 5min, closing the CO gas, vacuumizing residual CO in the tube, introducing Ar gas to raise the pressure inside the tube to normal pressure, pushing out the quartz boat for cooling.
The morphology and catalyst retention rate of the obtained carbon nanotubes were characterized by TEM, as shown in fig. 3 (c): sparse single-wall carbon nanotubes are grown, and metal nano particles are hardly visible on the solid solution catalyst, and the diameter of the single-wall carbon nanotubes is 1-3 nm.
Comparative example
In this example, a solid solution catalyst having a Co loading of 5mol% as described in example 1 was used.
Heating the tube furnace to 700 ℃ and stabilizing for 30min, placing a quartz boat containing 2mg of solid solution catalyst in a constant temperature area inside the furnace tube, introducing 100sccm CO gas to normal pressure, keeping for 10min, switching off the CO gas to 300sccm Ar, pushing out the quartz boat and cooling.
The morphology and catalyst retention rate of the obtained carbon nanotubes were characterized by TEM, as shown in fig. 3 (b): single-wall carbon nanotubes are grown, the metal nano particles remain more, and the metal nano particles are distributed on the carbon nanotubes and the solid solution catalyst, and the diameter of the single-wall carbon nanotubes is 0.5-3 nm.
Example 2
In this example, a Co-MgO solid solution catalyst having a metal loading of 2mol% was prepared by the catalyst preparation method described in example 1.
Heating the tube furnace to 900 ℃, stabilizing for 30min, placing a quartz boat with a catalyst in a low-temperature area inside the furnace tube, introducing argon of 200-400 sccm for 5min to exhaust air in the furnace tube, pushing the quartz boat into the constant-temperature area, continuously introducing hydrogen for 200sccm after stabilizing for 5min, reducing for 22min, introducing ethanol by using 100sccm of argon as carrier gas, using 100sccm of argon as buffer gas to grow carbon nano tubes for 15min, closing carbon source gas after the completion, performing heat treatment for 1.5h under the protection of argon, and pushing out for cooling.
The morphology and catalyst retention rate of the obtained carbon nanotubes were characterized by TEM, as shown in fig. 3 (d): more single-wall carbon nanotube bundles are grown, and metal nano particles are hardly visible on the solid solution catalyst, and the diameter of the single-wall carbon nanotubes is 0.5-3 nm.
Example 3
In this example, a solid solution catalyst having a Co loading of 5mol% as described in example 1 was used.
Heating the tube furnace to 900 ℃, stabilizing for 30min, placing a quartz boat with a catalyst in a low-temperature area inside the furnace tube, introducing 200-400 sccm argon for 5min to exhaust air in the furnace tube, pushing the quartz boat into the constant-temperature area, continuing introducing argon for stabilizing for 5min, introducing 50sccm argon as carrier gas into ethanol, introducing 100sccm hydrogen to reduce and grow carbon nanotubes for 3min, closing carbon source gas after the completion, and pushing out and cooling under the protection of argon. Is placed in a transmission electron microscope (environmental pressure is less than 10) -5 Pa, electron beam dose:) The catalyst was irradiated with electron beam for 10 to 20min, as shown in fig. 4, it was seen that the metal nanoparticles were mostly dissolved in the support. More single-wall carbon nanotube bundles are grown, and metal nano particles are hardly visible on the solid solution catalyst, and the diameter of the single-wall carbon nanotubes is 0.5-3 nm.
Example 4
In this example, a solid solution catalyst having a Co loading of 5mol% as described in example 1 was used.
And (3) placing 2mg of solid solution catalyst in 5ml of ethanol solution, uniformly dispersing by ultrasonic, sucking the catalyst suspension by using a dropper, dripping the catalyst suspension onto a silicon wafer with the thickness of 5mm or less, and placing the silicon wafer in an oven for drying for later use. Heating a tube furnace to 900 ℃, stabilizing for 30min, placing a silicon wafer with a catalyst in a quartz boat, pushing the silicon wafer into a low-temperature area in the furnace tube, introducing 200-400 sccm of argon for 5min to exhaust air in the furnace tube, pushing the quartz boat into the constant-temperature area, continuing introducing argon for stabilizing for 5min, introducing hydrogen for 200sccm, reducing for 30min, introducing ethanol by using 100sccm of argon as carrier gas, using 100sccm of argon as buffer gas to grow carbon nano tubes for 15min, closing carbon source gas after the completion, performing heat treatment for 1.5h under the protection of the argon, and pushing out for cooling. The scanning electron microscope and the Raman characterization of the silicon chip for growing the carbon nano tube are shown in fig. 5 (a-c).
Repeating the above steps for growing carbon nanotubes, and performing secondary growth of carbon nanotubes by using a solid solution catalyst on a silicon wafer, wherein the obtained results are shown in fig. 5 (d-f), and the scanning photo and the raman spectrogram can show that the density of the carbon nanotubes after secondary growth is increased by about 1.4 times of the yield of the carbon nanotubes after the first growth. More single-wall carbon nanotube bundles are grown, and metal nano particles are hardly visible on the solid solution catalyst, and the diameter of the single-wall carbon nanotubes is 0.5-3 nm.
The results of the examples show that the invention can directly and efficiently prepare the single-walled carbon nanotube without catalyst residue by utilizing the high activity of the metal catalyst and the interaction of the metal catalyst with the carrier, thereby improving the utilization efficiency of the catalyst, avoiding the influence of the metal catalyst residue on the performance of the carbon nanotube and being expected to promote the practical application of the metal catalyst in the fields of electronic devices, biomedical treatment and the like.

Claims (8)

1. The efficient preparation method of the single-walled carbon nanotube without metal catalyst residue is characterized by taking a metal oxide solid solution as a catalyst precursor, adopting a chemical vapor deposition method, preparing the single-walled carbon nanotube without metal catalyst residue through growth and post-treatment, and realizing efficient and repeated preparation of the single-walled carbon nanotube without catalyst residue by utilizing the characteristic of renewable catalyst precursor, wherein the preparation method comprises the following specific steps:
(1) The method comprises the steps of mixing catalytic active metal particles which are metal atoms or metal ions with an oxide carrier by using a physical chemistry method, and then carrying out high-temperature heat treatment to obtain a solid solution catalyst precursor loaded with active metal;
(2) Placing a solid solution catalyst precursor into a quartz boat, performing 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 carbon nanotubes;
(3) The diffusion recovery capacity of the catalytic active metal particles relative to the carrier is regulated and controlled, so that the catalyst is dissolved into the carrier, and no metal catalyst residue is realized; specifically, a one-step method is adopted, a carbon source is switched into vacuum or inert atmosphere to stop the growth of the carbon nano tube, and the temperature is reduced under the same condition, so that the single-wall carbon nano tube without metal catalyst residues is directly obtained; or adopting a two-step method to indirectly obtain the single-walled carbon nanotube without metal catalyst residues by introducing other energy action modes;
and (3) 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 obtain the carbon nano tube without catalyst residues.
2. The method for efficiently producing single-walled carbon nanotubes free of metal catalyst residues according to claim 1, wherein the solute atoms or ions in the solid solution of the metal oxide are dissolved in the carrier under the driving of an external field, including both the replacement of atoms in the carrier and the dissolution into the interstitial spaces of the carrier atoms; alternatively, solute atoms or ions diffuse away from the carrier under the action of an external field and form nanoscale 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 efficient preparation method of the single-walled carbon nanotubes without metal catalyst residues according to claim 1, 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 CO or ethanol vapor, and the carbon nanotubes are grown for 3-5 min at a lower temperature of 700-750 ℃ and a pressure of 5-8 kPa; the two-step method is an indirect preparation method, and the post-treatment is carried out on the grown carbon nano tube, wherein the post-treatment comprises a low-temperature oxidation method, an inert atmosphere annealing method or an electron beam irradiation method.
4. The efficient preparation method of the single-walled carbon nanotubes without metal catalyst residues according to claim 1, wherein the obtained single-walled carbon nanotubes have diameters distributed within a range of 0.5-3 nm, and no metal nanoparticles remain at both ends of the carbon nanotubes.
5. The method for efficiently preparing the single-walled carbon nanotubes without metal catalyst residues according to claim 1, wherein the catalyst precursor is a powder, a thin film or a treated commercial substrate of a metal oxide, has high temperature stability, and maintains a relatively stable crystal structure in a carbon tube growth temperature range of 700-1000 ℃.
6. The efficient preparation method of the metal-free catalyst residue single-walled carbon nanotubes according to claim 1, wherein in the step (1), the loading amount of the catalytically active metal in the catalyst precursor is in the range of 0.1 to 5 mol%.
7. The efficient production method of metal catalyst residue-free single-walled carbon nanotubes according to claim 1, wherein in the step (2), the atmosphere for the reduction pretreatment of the catalyst precursor is a carbon-containing atmosphere of hydrogen, CO or ethanol vapor; after the reduction pretreatment, the size of the precipitated catalyst is within the range of 0.5-3 nm; controlling the technological parameters of carbon nanotube growth: the temperature is 700-900 ℃ and the time is 3-15 min.
8. The method for efficiently producing a single-walled carbon nanotube free of metal catalyst residue according to claim 1, wherein in the step (3), air is introduced as an oxidizing atmosphere at a low temperature of 300 to 400 ℃ to heat-treat the product.
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