Method for preparing fullerene tube through catalytic chemical vapor deposition

Abstract

The invention relates to the technical field of nano material preparation, in particular to a method for preparing a fullerene tube through catalytic chemical vapor deposition. A catalytic chemical vapor deposition method is utilized, carbon is orderly assembled at a certain temperature by means of a catalyst, reaction conditions influencing catalyst-carbon interface bonding are further controlled, and direct preparation of the fullerene tube from bottom to top is achieved. The fullerene tube is in a molecular form and is composed of hemispherical fullerene cap ends at the two ends and a carbon nano tube tubular structure in the middle section, the length-diameter ratio is larger than 1, the length is within or below the range of short carbon nano tubes, and the diameter is 0.4-3 nm. According to the method, the design of the catalyst and the control of the dynamic process of catalytic growth of the nano carbon material are taken as the core, the direct preparation of the quasi-one-dimensional fullerene tube is finally realized, the bottleneck that the controllable preparation method of the fullerene tube at the present stage is few and the existing method has more byproducts is broken through, and the method has the characteristics of good controllability, simple process, low cost, suitability for large-scale preparation and the like; and a new way is provided for realizing efficient and controllable preparation of the fullerene tube.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and is a method for preparing fuller tubes by catalytic chemical vapor deposition, applicable to high carbon atom number fuller tube materials required in fields such as catalysis, medicine, photovoltaics and nanoelectronic devices. Background Technology

[0002] Since their discovery, fullerenes have demonstrated excellent and unique properties in optics, electronics, and other fields, and have been widely applied in biomedicine, energy technology, and materials science. In 2020, a new chemically isolated tubular fullerene, the fuller tube (J. Am. Chem. Soc. 2020, 142, 15614−15623), was reported, initiating research into its properties and applications. Fuller tubes are a novel type of carbon allotrope intermediate between zero-dimensional fullerenes and one-dimensional carbon nanotubes. Their structure integrates hemispherical fullerene caps at both ends with a tubular structure of carbon nanotubes in the middle (e.g., [5,5] C). 130 -D 5h (1) The fuller tube is a tubular structure with 70 carbon atoms in the middle section and hemispherical fullerenes with 30 carbon atoms at each end (J.Am. Chem. Soc. 2023, 145, 25942−25947). It has the characteristics of well-defined molecular weight, good structural reproducibility, small aspect ratio and solubility in organic solvents. The band structure and unique catalytic active sites of the fuller tube enable it to exhibit excellent performance close to that of Pt / C catalysts in oxygen reduction electrocatalysis (Angew. Chem. Int. Ed. 2022, 61,e202116727). At the same time, it has shown good antibacterial activity against mycobacteria in the medical field (Cell Biochem Funct. 2024;42:e3963). Previous studies have shown that the cap-end symmetry and tube structure of fuller tubes can synergistically control electronic properties (J. Am. Chem. Soc. 2022, 144, 10825−10829). With increasing carbon number, fuller tubes exhibit varying energy level distributions and HOMO-LUMO band gap characteristics. This energy level tunability gives high-carbon-number fuller tubes a core advantage in energy level engineering. By designing and fabricating fuller tubes with energy levels highly aligned with target materials (such as photosensitizers, catalysts, and semiconductor interfaces), it is expected to significantly improve electron transfer efficiency and overall material performance, thereby achieving performance enhancement. Therefore, developing novel methods for preparing fuller tubes to directly obtain high-purity, high-carbon-number (C) fuller tubes is crucial. 100 Fuller tubes (and above) are expected to exhibit unique and superior performance in fields such as catalysis, photovoltaics, medical devices and nanoelectronic devices, promoting their practical applications.

[0003] The current mainstream method for preparing fuller tubes is to synthesize fullerene soot using an electric arc method or a flame combustion method, followed by extraction, chemical selective enrichment, and multi-stage separation and purification using high-performance liquid chromatography (HPLC) to achieve the preparation of high-purity, structurally well-defined fuller tubes. This method has two drawbacks: (1) the soot must be selectively reacted with aminopropanol to remove spherical fullerenes and increase the proportion of fuller tubes, requiring multiple HPLC purifications to obtain the tubes, resulting in a complex and costly process; (2) the synthesized carbonaceous products are mainly C. 60 / C 70 Similar to amorphous carbon, high-carbon-number fullerenes are present in low amounts and have a wide variety of isomers, resulting in a very small proportion of tubular fullerenes and extremely low yields of high-carbon-number fullerenes (C1 in 2500 mg of soot extract). 120 / C 130 The production rate is less than 50 micrograms, and it is difficult to obtain fuller tubes with higher carbon atom numbers (Acc. Chem. Res. 2024, 57, 15, 2154–2165), which limits in-depth research on its properties and exploration of its applications.

[0004] Patent CN1931717A discloses a method for preparing onion-shaped fullerene composite materials with uniform particle size. Using zeolite as a template and metallocene as a catalyst, onion-shaped fullerenes with encapsulated metals are prepared via chemical vapor deposition (CVD). The product is still onion-shaped fullerene, not fuller tubes, and the particle size is controlled by the pore size of the zeolite template. The product is a composite material, and pure carbon-phase fuller tubes cannot be obtained. Patent CN1598046A discloses a method for preparing onion-shaped fullerenes via chemical vapor deposition. Using nano-iron particles generated from the pyrolysis of ferrocene as a catalyst and acetylene as a carbon source, onion-shaped fullerenes are prepared via CVD. The product is a carbon-phase fullerene. 60 The core is a concentric spherical multi-layered shell structure. A single iron catalyst easily leads to excessive cracking of the carbon source, and amorphous carbon impurities are easily mixed into the product. Patent CN1344227A discloses a method and equipment for manufacturing fullerenes and nanotubes with more than 70 carbon atoms. It employs an arc discharge process to prepare a mixture of fullerenes and nanotubes in a multi-component hydrocarbon liquid by adjusting the current pulse. The product is a mixed system of fullerenes and nanotubes, requiring multiple complex post-processing steps such as boiling concentrated nitric acid treatment, low-speed centrifugation, and molecular sieve filtration. High-carbon-atom-number fullerenes (such as C...) 90 (Above) The yield is extremely low.

[0005] Therefore, it is necessary to develop a novel method for preparing fuller tubes, aiming to increase the proportion of fuller tubes in the original product while reducing complex subsequent chemical processing and separation steps. This would enable the exploration of the properties and applications of fuller tubes with higher carbon number atoms. Compared to existing fullerene preparation methods, developing a milder method allows for precise and controllable process parameters, facilitating structural control and large-scale preparation of the target product. This method not only provides new insights into the field of fuller tube preparation but also lays an important technological foundation for the large-scale preparation and application of high-performance nanomaterials. Summary of the Invention

[0006] To address the problems of low yield and complex purification and separation processes in existing technologies for preparing fuller tubes, the present invention aims to propose a method for preparing fuller tubes by catalytic chemical vapor deposition. First, a suitable method is selected to prepare a nanoscale catalyst. At a certain temperature, the catalyst comes into contact with a carbon source, catalyzing the decomposition of the carbon source to generate active carbon atoms, which are then reassembled on the catalyst surface, achieving the nucleation and growth of fuller tubes (similar to the growth mode of carbon nanotubes). By controlling the binding force between the catalyst and the generated tubular carbon structure, the two are separated in a timely manner. Simultaneously, the tubular carbon structure closes after separation, thus completing the preparation of fuller tubes.

[0007] The technical solution of this invention: A method for preparing fuller tubes by catalytic chemical vapor deposition (CVD) utilizes CVD to assemble carbon in an orderly manner with the aid of a catalyst, and further controls the reaction conditions affecting the catalyst-carbon interface bonding to achieve the direct bottom-up preparation of fuller tubes. The method includes the following steps: (1) Catalyst design and synthesis: Select catalyst and support types, and load catalyst precursor solvent or thin film onto the support by impregnation, co-precipitation, sol-gel method, ion exchange method, ion plating method or magnetron sputtering method to prepare supported catalyst; (2) Preparation of fuller tubes by catalytic chemical vapor deposition: The supported catalyst is placed in the reaction zone of a chemical vapor deposition tube furnace, and a carbon source is introduced under high temperature conditions. After a period of chemical vapor deposition, the reaction conditions affect the strength of the catalyst-carbon interface bonding, thereby catalytically preparing fuller tubes, which are distributed in different positions of the reaction system.

[0008] The method for preparing fuller tubes by catalytic chemical vapor deposition directly produces fuller tubes with a molecular morphology, consisting of hemispherical fullerene caps at both ends and a tubular structure of carbon nanotubes in the middle section. The aspect ratio is greater than 1, the length is within the range of short carbon nanotubes and not greater than 10 nm, and the diameter is between 0.4 and 3 nm.

[0009] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (1), the catalyst is one of a transition metal element, a transition metal mixture or a carbide alloy, and the catalyst particle size is between 0.4 and 5 nm, wherein the transition metal is iron, cobalt, nickel, gold, silver, copper, platinum, palladium, ruthenium, rhodium or tungsten.

[0010] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (1), the carrier is oxide powder, oxide substrate, molecular sieve, silicon wafer, carbon nanotube, graphene or boron nitride, wherein the oxide powder or oxide substrate is magnesium oxide, aluminum oxide, barium oxide, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide or zinc oxide.

[0011] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (1), the loading amount of the supported catalyst is as follows: when the support is oxide powder, molecular sieve or carbon nanotube, the loading amount of the catalyst is 0.01~5wt%; when the support is oxide substrate, silicon wafer, graphene or boron nitride, the thickness of the supported catalyst precursor is 0.01~1nm.

[0012] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (2), when a carbon source is introduced under high temperature conditions, the chemical vapor deposition temperature is 300~1000℃, and the carbon source is a carbon-containing gaseous precursor, a carbon-containing liquid vapor precursor, or a solid carrier carbon source; wherein, the carbon-containing gaseous precursor is one of carbon monoxide, ethylene, methane, acetylene, propane, propylene, or a mixture thereof with a carrier gas; the carbon-containing liquid vapor precursor is one of methanol vapor, ethanol vapor, benzene vapor, toluene vapor, xylene vapor, a mixture of carbon monoxide and water vapor; and the solid carbon source is one of graphite or amorphous carbon.

[0013] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (2), after a period of chemical vapor deposition, the growth time is 0.5~60min; when the carbon source used for chemical vapor deposition is a carbon-containing gaseous precursor, it does not contain a carrier gas and is directly introduced into the reaction zone, and the linear velocity of the carbon source in the reaction zone is 0.01~10cm / s; when the carbon source is a liquid vapor precursor, it is carried into the reaction zone by the carrier gas, and the linear velocity of the carrier gas in the reaction zone is 0.01~10cm / s; when the carbon source is a solid carbon source, it is directly placed in the reaction zone of the chemical vapor deposition tube furnace.

[0014] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (2), the reaction conditions affect the strength of the catalyst-carbon interface bonding. The reaction conditions refer only to the coordinated control of catalyst characteristics, carbon source linear velocity and reaction temperature. The strength of the catalyst-carbon interface bonding plays a role in the early stage of catalytic growth of nano-carbon materials, thereby achieving the closure of the fuller tube and its separation from the catalyst.

[0015] In the method for preparing fuller tubes by catalytic chemical vapor deposition, in step (2), the fuller tubes are distributed in different positions in the reaction system, including: on the supported catalyst support, on the wall of the chemical vapor deposition tubular furnace, or in the tail gas washing bottle.

[0016] The method for preparing fuller tubes by catalytic chemical vapor deposition, wherein the obtained fuller tubes are represented by the molecular formula: C A+B+nX A, B, n, and X are natural numbers. A and B are the number of carbon atoms at the two hemispherical fullerene caps A and B. nX is the number of carbon atoms in the tubular carbon structure in the middle section. n is the number of carbon atom bands in the middle section. X is the number of carbon atoms in the carbon atom band. X = X1 + X2 - X0. X1 and X2 are the number of carbon atoms required to achieve six-membered ring end capping at caps A and B. X0 is the number of carbon atoms that overlap when caps A and B are spliced ​​after six-membered ring end capping. Fuller tubes with different structures have different fullerene caps and carbon atom band numbers.

[0017] The design concept of this invention is: This invention utilizes a nanocatalyst to catalytically crack a carbon source at a certain temperature. The resulting carbon atoms are then reassembled by the catalyst to form a tubular carbon structure with a hemispherical fullerene at the top. The number of carbon atoms is increased by extending the tubular structure. By designing and selecting the catalyst, and synergistically controlling the temperature and carbon source linear velocity, the strength of the catalyst-carbon heterogeneous interface is controlled. This allows the hemispherical fullerene structure at the top and the tubular carbon nanotube structure in the middle section to detach from the catalyst in the later stages of growth, achieving tail-end closure. Finally, a fuller tube with hemispherical fullerenes at both ends and a tubular carbon nanotube structure in the middle section is prepared.

[0018] This invention utilizes catalytic chemical vapor deposition to orderly assemble active carbon atoms on a catalyst, designing and preparing catalysts with specific compositions and sizes. It optimizes the type of carbon source, carbon source linear velocity, and reaction temperature, controlling the strength of the heterojunction between the catalyst and carbon, thus achieving the direct preparation of fuller tubes. This invention can be used to prepare high-carbon-atom-number fuller tubes with different structures. In particular, the design and preparation of the catalyst composition and size have a significant impact on the preparation of fuller tubes. The catalyst composition is mainly platinum, nickel, and copper, but can be extended to other transition metal elements, mixtures, or carbide alloys, such as iron, cobalt, cobalt-nickel, copper-nickel, and cobalt-tungsten-carbon. The catalyst size is between 0.4 and 3 nm. Simultaneously, it is supported on oxide powders, oxide substrates, silicon wafers, carbon nanotubes, and solid carbon sources through methods such as impregnation, ion plating, and magnetron sputtering, ensuring catalytic activity while avoiding catalyst particle aggregation. In addition, the type of carbon source, the carbon source linear velocity, and the reaction temperature all play a key role in the preparation of Fuller tubes. The carbon source is mainly a carbon-containing gaseous or liquid vapor precursor, such as carbon monoxide, ethanol vapor, ethylene, methane, acetylene, a mixture of carbon monoxide and water vapor, etc. It can also be extended to other solid carbon sources, such as graphite and amorphous carbon.

[0019] The advantages and beneficial effects of this invention are: 1. This invention proposes a method for preparing fuller tubes via catalytic chemical vapor deposition. By catalytically decomposing the carbon source and reassembling active carbon atoms, the number of carbon atoms in the fuller tube is increased. By controlling the bonding force at the catalyst-carbon heterostructure interface, the generated carbon structure separates from the catalyst in a timely manner and spontaneously closes to directly prepare the fuller tube. This method contributes to a deeper understanding of the formation mechanism of fuller tubes, further clarifies the formation mechanism and key influencing factors of fullerenes, and propels the academic community to a new level in the understanding, synthesis, and application research of fullerenes.

[0020] 2. This invention achieves the catalytic chemical vapor deposition (CVD) preparation of fuller tubes under relatively mild reaction conditions, avoiding the problems of complex carbonaceous products, low fuller tube yields, and complex chemical post-processing associated with traditional preparation methods (such as arc methods and flame combustion methods) that require rapid preparation at extremely high temperatures over short periods. It offers advantages such as simple method, low cost, and more precise and controllable process parameters, facilitating the controllable and continuous preparation of the target product and demonstrating potential for large-scale fuller tube production. Furthermore, the production process is expected to be extended to the preparation of megafullerenes, providing valuable insights for fullerene preparation.

[0021] 3. The fuller tubes prepared in this invention are in molecular form, consisting of hemispherical fullerene caps at both ends and a tubular structure of carbon nanotubes in the middle. The symmetry of the caps and the length of the tube structure synergistically regulate the physical and chemical properties of the fuller tubes. Therefore, by preparing fuller tubes with different structures, the application requirements of fuller tube materials with different structures and properties in fields such as catalysis, medical devices and electronic devices can be met. At the same time, fuller tubes can be prepared on different supports, and different composite system products can be directly prepared according to the needs of different application scenarios.

[0022] In summary, this invention, starting with the preparation of fuller tubes, employs a catalytic chemical vapor deposition method to control the catalytic nucleation and growth kinetics of nano-carbon materials, achieving the direct preparation of fuller tubes. This overcomes the bottleneck of limited controllable preparation methods and numerous byproducts in existing methods, resulting in high product purity and reduced complex post-chemical processing and separation procedures. This method is low-cost, simple, and highly controllable, suitable for continuous and large-scale production, providing a new approach for the efficient and controllable preparation of fuller tubes with specific structures. Attached Figure Description

[0023] Figure 1 High-resolution transmission electron microscopy (TEM) images of the prepared fuller tubes. In Example 1, image a shows a fuller tube directly prepared by catalytic decomposition of magnesium oxide-supported platinum nanoparticles at 600°C; image b shows a fuller tube sample prepared in Example 1 loaded onto graphene after extraction and enrichment; the arrows indicate the prepared fuller tubes.

[0024] Figures 2-3 The total ion chromatogram and mass spectrum corresponding to specific time periods were analyzed by liquid chromatography-mass spectrometry (LC-MS) of the prepared Fuller tubes. Figure 2 The total ion chromatogram is obtained from the analysis performed by liquid chromatography-mass spectrometry. Figure 3 In the middle, above is Figure 2 The mass spectra corresponding to the total ion chromatogram analyzed by chromatography-mass spectrometry in the range of 0–0.646 min are shown below. Figure 2 The total ion chromatogram analyzed by chromatography-mass spectrometry corresponds to the mass spectrum in the range of 0.646 to 6 min.

[0025] Figure 4 Transmission electron microscope images of fuller tubes prepared on different supports. In Example 2, a and b show fuller tubes prepared by catalytic cracking of carbon monoxide with platinum nanoparticles supported on carbon nanotubes at 600°C, and fuller tubes prepared by catalytic cracking of ethanol with platinum nanoparticles supported on hexagonal boron nitride sheets at 550°C, respectively.

[0026] Figure 5 Control group experiment. In the figure, a is a transmission electron microscope (TEM) image of the carbon-coated deactivated large particle catalyst prepared under unoptimized reaction conditions; b is a TEM image of the carbon nanotubes prepared under unoptimized reaction conditions; and c is the laser Raman spectrum of the product prepared under condition b (laser wavelength λ = 532 nm). Detailed Implementation

[0027] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, a further detailed description is provided below in conjunction with the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a full understanding of this invention. However, this invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this invention. Therefore, this invention is not limited to the specific embodiments disclosed below.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] Example 1

[0030] In this embodiment, a platinum catalyst supported on magnesium oxide is used to prepare fuller tubes: Catalyst Synthesis: A porous magnesium oxide support was prepared by high-temperature calcination (600℃, 6h) in a muffle furnace using basic magnesium carbonate pentahydrate as the precursor. Nano-platinum catalyst was supported using an impregnation method: the catalyst precursor chloroplatinic acid hexahydrate (H₂PtCl₆·6H₂O) was dissolved in deionized water to form a homogeneous solution with a concentration of 0.01 mol / L. Magnesium oxide powder was quantitatively added at a platinum loading of 0.5 wt%, and the mixture was magnetically stirred for 12h to achieve full adsorption. After the system was allowed to settle and separate into layers, the supernatant was removed. After balancing, the mixture was centrifuged (10000 rpm, 1h, 10℃). The resulting solid phase was sequentially freeze-dried (-50℃, 48h), heated to dry (180℃, 12h), and calcined at high temperature (1000℃, 20h) to finally obtain the platinum-magnesium oxide catalyst.

[0031] Catalytic chemical vapor deposition (CVD) preparation: In a CVD tube furnace, the reaction zone temperature was set to 600℃. Ethanol vapor was transported to the reaction system (ethanol pre-saturated in a 30℃ isothermal bubbler) via an argon carrier gas flow (40 sccm) for 30 min to establish a carbon source atmosphere. Subsequently, a platinum-magnesium oxide catalyst was introduced, and growth was carried out in this atmosphere for 10 min, followed by cooling to obtain fuller tubes prepared by magnesium oxide-supported platinum nanoparticle catalysis.

[0032] Structural characterization of directly prepared fuller tubes: Figure 1 Figure a shows a two-dimensional projection of a transmission electron microscope image. As can be seen from the figure, multiple ellipsoidal monolayer nanostructures (with an inner diameter distribution of 0.69~0.9 nm and a length distribution of 0.69~2.1 nm) are attached to a magnesium oxide substrate. This carbon structure is intermediate between fuller tubes and carbon nanotubes, indicating that fuller tubes were catalytically prepared by chemical vapor deposition.

[0033] Structural characterization of purified fuller tubes: o-xylene was added to the prepared sample for fuller tube extraction. After thorough soaking and sonication, 1 mol / L hydrochloric acid solution was added and magnetically stirred for 10 min. The mixture was then allowed to separate into layers; the supernatant was the solution containing the fuller tubes. This supernatant was dropped onto graphene and characterized under a transmission electron microscope. Figure 1 As shown in b, fuller tubes can be observed on the graphene support, indicating that the prepared sample is a fuller tube and has been extracted into an organic solvent. The inner diameter of the fuller tube is 0.69~0.85nm, the length is 0.69~2.45nm, and the number of carbon atoms is 60~210, which corresponds to the mass spectrometry detection results (e.g., the number of carbon atoms in fuller tubes A and B is approximately 200 and 210, respectively), proving that this method can prepare fuller tubes with different numbers of carbon atoms.

[0034] like Figures 2-3 The results of liquid chromatography-mass spectrometry characterization of the purified Fuller tubes are shown.

[0035] Analysis of the total ion chromatogram and its corresponding mass spectrum using liquid chromatography-mass spectrometry (LC-MS) confirmed that the prepared product was a high-carbon-number fuller tube. Analysis of the mass spectrum corresponding to the total ion chromatogram from 0 to 0.646 min using LC-MS revealed that small carbon cluster molecules predominated, with fuller tubes accounting for a smaller proportion. The product with m / z = 1199.7 was a C444 fuller tube. 100 m / z=1347.8 could be C 112 H3(C) 112 (The product of the hydrogen addition reaction of the fuller tube). Fuller tubes with higher carbon numbers show very weak signals and account for a very small proportion. As the flow time increases, the mass spectrum corresponding to the total ion chromatogram from 0.646 to 6 min, analyzed by chromatography-mass spectrometry, shows an increase in the signal and proportion of high-carbon-number fuller tubes (possibly due to the adsorption of the fuller tubes by the stainless steel capillary of the liquid chromatograph, causing small clusters to elute and be detected first, while high-carbon-number fuller tubes elute and are detected after a period of time). For example, various peaks of high-carbon-number fuller tubes appear (peaks with a mass-to-charge ratio m / z greater than 1199.7 correspond to C... 100 (Fuller tube). Where m / z = 1728.4 is C 144 m / z=1801.4 is C 150 Other signals may indicate (addition reactions of the Fuller tube with hydrogen, oxygen, etc.): m / z=1505 indicates C. 124 O, m / z = 1579.4 is C 130 OH3, m / z = 1875.5 is C 156 H3, m / z = 1950.5 is C 162 H6, m / z=2024.5 is C 168 H8 indicates that this method successfully prepares high-carbon-atom-number fuller tubes. The method utilizes both direct preparation and purified fuller tube products for characterization. In this embodiment, the yield of fuller tubes per batch is related to the size of the tubular furnace and the amount of supported catalyst used; after multiple preparations, the yield can reach the mg level.

[0036] Example 2

[0037] In this embodiment, the type of catalyst support was changed, and a fuller tube was prepared using a platinum catalyst supported on carbon nanotubes. The structure characterization is as follows: Catalyst synthesis: Carbon nanotubes prepared by floating catalytic chemical vapor deposition (FCCVD) were used as catalyst supports. The carbon nanotubes were ultrasonically dispersed in anhydrous ethanol to form a dispersion with a concentration of 4 mg / mL. The catalyst precursor chloroplatinic acid hexahydrate (H2PtCl6·6H2O) was dissolved in ethanol to form a precursor solution with a platinum loading of 0.8 wt%. The precursor solution was loaded onto the surface of carbon nanotubes by impregnation. After ultrasonication, the catalyst was vacuum dried (70℃, 12 h) and subjected to tube furnace heat treatment (Ar atmosphere, heating to 400℃ at 5℃ / min and holding for 30 min) to remove residual organic matter and chloride ions on the surface, thus obtaining the platinum-carbon nanotube catalyst.

[0038] Catalytic chemical vapor deposition preparation: In a CVD tube furnace, the reaction zone temperature was set to 600℃, and a CO (20 sccm) gas flow was introduced. After maintaining the above conditions for 30 min to build a stable saturated atmosphere for the carbon source, the platinum-carbon nanotube catalyst was placed in a quartz boat and introduced into the CVD tube furnace. After growing in this atmosphere for 10 min, it was taken out and cooled to obtain fuller tubes prepared by catalysis of platinum nanoparticles supported on carbon nanotubes.

[0039] like Figure 4 As shown in a, the prepared product was characterized under a transmission electron microscope. After changing the catalyst support, the transmission electron microscope also showed that the fuller tubes adhered to the carbon nanotubes, indicating that the method of preparing fuller tubes by catalytic chemical vapor deposition has a certain universality for the preparation of fuller tubes by loading the catalyst on different supports.

[0040] Example 3

[0041] In this embodiment, the type of catalyst support was changed, and a fuller tube was prepared using a platinum catalyst supported on hexagonal boron nitride. The structure of the fuller tube is characterized as follows: Catalyst synthesis: 3-6 layers of hexagonal boron nitride atomic layers were adhered from the bulk hexagonal boron nitride using a tape peeling method, and then transferred to the through-holes of the silicon wafer using a dry polydimethylsiloxane-assisted transfer method. A platinum catalyst layer with a thickness of about 0.03 nm was deposited on the silicon wafer with the transferred few layers of boron nitride by ion plating to obtain a platinum-boron nitride catalyst.

[0042] Fuller tubes were prepared by chemical vapor deposition: The reaction zone temperature was set to 550℃ in a CVD tube furnace. Ethanol vapor (pre-saturated with ethanol in a 30℃ constant-temperature bubbler) was transported to the reaction system via an argon carrier gas flow (40 sccm) for 30 min to establish a carbon source atmosphere. Subsequently, a platinum-boron nitride catalyst was introduced, and growth was carried out in this atmosphere for 10 min followed by cooling to obtain fuller tubes prepared by hexagonal boron nitride-supported platinum nanoparticle catalysis.

[0043] like Figure 4As shown in b, the prepared product was characterized under a transmission electron microscope. Discretely distributed fuller tubes could also be observed on the boron nitride support, indicating that this method has a certain universality for preparing fuller tubes on catalysts supported on different supports.

[0044] Comparative Example 1: Large catalyst particles forming carbon coatings cannot be used to prepare fuller tubes. The loading of the magnesium oxide-supported platinum catalyst in Example 1 was increased to 2 wt%, the carbon source was increased to argon gas carrier (200 sccm), and ethanol vapor was delivered to the reaction system (ethanol pre-saturated in a 30°C constant temperature bubbler). Other conditions and steps were the same as in Example 1.

[0045] like Figure 5 As shown in Figure a, the prepared sample was characterized under a transmission electron microscope. After the catalyst loading was increased, no fuller tubes were found under the transmission electron microscope. It was observed that large catalyst particles were deactivated by carbon coating, which confirmed that catalyst particles of appropriate size are required to prepare fuller tubes.

[0046] Comparative Example 2: The product is a single-walled carbon nanotube with a large aspect ratio. The carbon source conditions in Example 1 were changed to 50 sccm of methane being delivered to the reaction system, and the catalyst was changed from platinum to nickel. Other conditions and procedures remained the same as in Example 1. The prepared sample was characterized using a transmission electron microscope and a 532 nm laser Raman spectrometer.

[0047] like Figure 5 As shown in b, after changing the carbon source and catalyst, no fuller tubes were found under transmission electron microscopy, but carbon nanotubes with a large aspect ratio were observed. Figure 5 As shown in c, the Raman spectroscopy results also indicate the formation of carbon nanotubes, which confirms that only the appropriate carbon source and catalyst design and selection can achieve the preparation of fuller tubes; otherwise, other products will be formed.

[0048] The results of the examples and comparative examples demonstrate that this invention proposes a novel method for preparing tubular fullerenes (fuller tubes). Utilizing catalytic chemical vapor deposition, active carbon atoms are orderedly assembled on a catalyst, and the heterogeneous interface between the catalyst and carbon is further controlled to achieve the direct preparation of fuller tubes. This method solves the problems of low yield and low output associated with traditional methods. The proportion of fuller tubes in the product of this method is significantly higher than that of traditional arc or flame methods, and the yield can reach the mg level. It reduces complex post-chemical processing and separation processes, offers milder reaction conditions and more precisely controllable process parameters, and possesses continuous production capabilities. With a continuous supply of catalyst and carbon source, it holds promise for large-scale fullerene preparation. The fuller tube preparation method proposed in this invention contributes to a deeper understanding of the formation mechanism of fuller tubes, further clarifies the formation mechanism and key influencing factors of fullerenes, and propels the academic community's understanding, synthesis, and application research of fullerenes to a new level.

[0049] This invention is not limited to the above-described embodiments and comparative examples. Various modifications and improvements made to this solution by those skilled in the art under the framework of this invention should be protected by the claims of this invention.

Claims

1. A method for preparing fuller tubes by catalytic chemical vapor deposition, characterized in that, Using catalytic chemical vapor deposition, carbon is assembled in an orderly manner with the aid of a catalyst. Further control of reaction conditions affecting the catalyst-carbon interface bonding is achieved to directly prepare fuller tubes from the bottom up. The process includes the following steps: (1) Catalyst design and synthesis: Select catalyst and support types, and load catalyst precursor solvent or thin film onto the support by impregnation, co-precipitation, sol-gel method, ion exchange method, ion plating method or magnetron sputtering method to prepare supported catalyst; (2) Preparation of fuller tubes by catalytic chemical vapor deposition: The supported catalyst is placed in the reaction zone of a chemical vapor deposition tube furnace, and a carbon source is introduced under high temperature conditions. After a period of chemical vapor deposition, the reaction conditions affect the strength of the catalyst-carbon interface bonding, thereby catalytically preparing fuller tubes, which are distributed in different positions of the reaction system.

2. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, The directly prepared fuller tubes exhibit a molecular morphology, consisting of hemispherical fullerene caps at both ends and a tubular structure of carbon nanotubes in the middle. The aspect ratio is greater than 1, the length is within the range of short carbon nanotubes and not greater than 10 nm, and the diameter is between 0.4 and 3 nm.

3. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (1), the catalyst is one of a transition metal element, a transition metal mixture or a carbide alloy, and the catalyst particle size is between 0.4 and 5 nm. The transition metal is iron, cobalt, nickel, gold, silver, copper, platinum, palladium, ruthenium, rhodium or tungsten.

4. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (1), the carrier is an oxide powder, an oxide substrate, a molecular sieve, a silicon wafer, a carbon nanotube, graphene, or boron nitride, wherein the oxide powder or oxide substrate is magnesium oxide, aluminum oxide, barium oxide, silicon dioxide, titanium dioxide, zirconium oxide, cerium oxide, or zinc oxide.

5. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 4, characterized in that, In step (1), the loading amount of the supported catalyst is as follows: when the support is oxide powder, molecular sieve or carbon nanotube, the loading amount of the catalyst is 0.01~5wt%; when the support is oxide substrate, silicon wafer, graphene or boron nitride, the thickness of the supported catalyst precursor is 0.01~1nm.

6. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (2), when a carbon source is introduced under high temperature conditions, the chemical vapor deposition temperature is 300~1000℃. The carbon source is a carbon-containing gaseous precursor, a carbon-containing liquid vapor precursor, or a solid carrier carbon source. Among them, the carbon-containing gaseous precursor is one of carbon monoxide, ethylene, methane, acetylene, propane, propylene, or a mixture thereof with the carrier gas; the carbon-containing liquid vapor precursor is one of methanol vapor, ethanol vapor, benzene vapor, toluene vapor, xylene vapor, a mixture of carbon monoxide and water vapor; and the solid carbon source is one of graphite or amorphous carbon.

7. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (2), after a period of chemical vapor deposition, the growth time is 0.5~60 min; when the carbon source used for chemical vapor deposition is a carbon-containing gaseous precursor, it does not contain carrier gas and is directly introduced into the reaction zone, and the linear velocity of the carbon source in the reaction zone is 0.01~10 cm / s; when the carbon source is a liquid vapor precursor, it is carried into the reaction zone by the carrier gas, and the linear velocity of the carrier gas in the reaction zone is 0.01~10 cm / s; when the carbon source is a solid carbon source, it is directly placed in the reaction zone of the chemical vapor deposition tube furnace.

8. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (2), the reaction conditions affect the strength of the catalyst-carbon interface. The reaction conditions refer only to the coordinated control of catalyst characteristics, carbon source linear velocity and reaction temperature. The strength of the catalyst-carbon interface plays a role in the early stage of catalytic growth of nano-carbon materials, realizing the closure of the fuller tube and its separation from the catalyst.

9. The method for preparing fuller tubes by catalytic chemical vapor deposition according to claim 1, characterized in that, In step (2), the fuller tubes are distributed in different locations in the reaction system, including on the supported catalyst support, on the wall of the chemical vapor deposition tubular furnace, or in the tail gas washing bottle.

10. The method for preparing fuller tubes by catalytic chemical vapor deposition according to any one of claims 1 to 9, characterized in that, The obtained Fuller tube is represented by the molecular formula: C A+B+nX A, B, n, and X are natural numbers. A and B are the number of carbon atoms at the two hemispherical fullerene caps A and B. nX is the number of carbon atoms in the tubular carbon structure in the middle section. n is the number of carbon atom bands in the middle section. X is the number of carbon atoms in the carbon atom band. X = X1 + X2 - X0. X1 and X2 are the number of carbon atoms required to achieve six-membered ring end capping at caps A and B. X0 is the number of carbon atoms that overlap when caps A and B are spliced ​​after six-membered ring end capping. Fuller tubes with different structures have different fullerene caps and carbon atom band numbers.

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