Preparation method of defect-rich single-walled carbon nanotube

Abstract

The preparation method of the defect-rich single-walled carbon nanotube comprises the following preparation steps: step (1): dissolving iron nitrate nonahydrate in deionized water, putting the iron nitrate nonahydrate and an aluminum foil into a porcelain boat, heating a reaction furnace to 600-1000 DEG C in an air atmosphere, reacting for 0.5-1 hour, and cooling to room temperature to obtain a hercynite catalyst with catalytic activity; and (2) putting the hercynite catalyst into a tubular furnace, heating to 800-1000 DEG C in an inert gas atmosphere, introducing H2 to react for 20-60 minutes, then introducing CH4 to react for 20-60 minutes, then stopping the reaction, and continuously cooling in the inert gas atmosphere to obtain the defect-rich single-walled carbon nanotube. According to the method disclosed by the invention, the active nanoparticles are formed by high-temperature calcination and induction of conversion of a catalyst crystal structure, so that the problems that active metal particles are easy to generate coalescence and the nanoparticles are difficult to keep a small-particle state in the prior art are solved, and the preparation of the defect-rich single-walled carbon nanotubes is realized.

Description

Technical Field

[0001] This invention belongs to the field of new materials, specifically relating to a method for preparing single-walled carbon nanotubes. Background Technology

[0002] Carbon nanotubes are one-dimensional, hollow cylindrical structures that can be considered as tubular objects formed by rolling up graphite sheets. They are classified into multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Due to their excellent electronic and mechanical properties, carbon nanotubes have been widely used in composite materials such as rubber and conductive pastes. For specific applications, defect-rich single-walled carbon nanotubes are ideal materials.

[0003] Chemical vapor deposition (CVD) synthesis methods based on solid-supported catalysts have become attractive due to their low cost, good controllability, and potential for large-scale synthesis with controlled structures. Researchers have developed various supported catalysts for the growth of single-walled carbon nanotubes. However, in existing single-walled carbon nanotube preparation processes, metal catalysts are prone to melt agglomeration during high-temperature calcination, leading to catalyst particle growth and deactivation. Therefore, current techniques generally aim to improve catalytic activity by reducing catalyst size and density. However, single-walled carbon nanotubes grown from smaller catalysts have lower defect rates, which is detrimental to further loading. Thus, existing techniques struggle to achieve the growth of defect-rich single-walled carbon nanotubes. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing defect-rich single-walled carbon nanotubes, which reduces the aggregation of active metal particles and achieves the preparation of defect-rich single-walled carbon nanotubes.

[0005] The technical solution of this invention is: (1) Dissolve ferric nitrate nonahydrate in deionized water, place it and aluminum foil in a ceramic boat, heat the reaction furnace to 600-1000℃ in an air atmosphere, react for 0.5-1h and then cool to room temperature to obtain an iron-aluminum spinel catalyst with catalytic activity. The preparation method of the catalytically active iron-aluminum spinel catalyst in step (1) is as follows: Add ferric nitrate nonahydrate to deionized water and stir at 400-800 r / min for 10-20 min to completely dissolve the metal salt. Then transfer 2-5 ml of the ferric nitrate aqueous solution to an alumina ceramic boat and place the aluminum foil inside the boat. The mass ratio of the nonahydrated ferric nitrate to deionized water is 1~20:1; The aluminum foil has a size of 15*30*2~20*40*50mm; The aluminum foil contains more than 99.35% Al. The dimensions of the porcelain boat are 50*28*15~80*40*16mm; The aluminum foil is placed inside the ceramic boat: the aluminum foil can be located at any position in the solution, either at the bottom, inside, or on the surface.

[0006] (2) The iron-aluminum spinel catalyst was placed in a tube furnace and heated to 800-1000℃ under an inert gas atmosphere. H2 was introduced and reacted for 20-60 min, followed by CH4 and reacted for 20-60 min. The reaction was then stopped and cooled under a protective atmosphere to obtain single-walled carbon nanotubes.

[0007] The temperature in step (2) is 800-1000℃, for example, it can be 850℃, 870℃, 900℃, 920℃, 950℃, 970℃ or 1000℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. In step (3), the H2 reaction time is 20-60 min, for example, it can be 20 min, 23 min, 25 min, 27 min, 30 min, 33 min, 35 min or 40 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. In step (3), the CH4 reaction time is 20 to 60 minutes, for example, it can be 20 minutes, 23 minutes, 25 minutes, 27 minutes, 30 minutes, 33 minutes, 35 minutes or 40 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0008] This invention obtains an Fe-Al spinel catalyst by placing aluminum foil and an aqueous solution of an active metal salt in a ceramic boat and then calcining it using CVD. Fe ions are immobilized within the crystal space constructed from Al and O. During reduction, the Fe ions escape from the metal-containing catalyst, forming catalytically active nanoparticles. On one hand, the reduced metal nanoparticles rapidly catalyze the growth of SWCNTs, preventing agglomeration and deactivation due to metal nanoparticle accumulation. On the other hand, due to the strong interaction between the metal oxide and the nanoparticles, the metal nanoparticles exhibit thermal stability at high temperatures, thus possessing catalytic activity. This method is more economical and environmentally friendly for product separation and purification. In summary, the strong interaction and catalyst escape mechanism allow the catalyst nanoparticles to remain in a small particle state, enabling the preparation of defect-rich single-walled carbon nanotubes. Attached Figure Description

[0009] Figure 1 The X-ray diffraction pattern of the iron-aluminum spinel catalyst prepared in Example 1 of this invention; Figure 2The Raman spectroscopy results are for the single-walled carbon nanotubes prepared in Example 1 of this invention. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0012] This invention provides a method for producing defect-rich single-walled carbon nanotubes, comprising the following steps: (1) Dissolve ferric nitrate nonahydrate in deionized water, place it and aluminum foil in a ceramic boat, heat the reaction furnace to 600-1000℃ in an air atmosphere, react for 0.5-1h and then cool to room temperature to obtain an iron-aluminum spinel catalyst with catalytic activity. (2) The iron-aluminum spinel catalyst was placed in a tube furnace and heated to 800-1000℃ under an inert gas atmosphere. H2 was introduced and the reaction was carried out for 20-60 min, followed by CH4 and the reaction was carried out for 20-60 min. The reaction was then stopped and the mixture was cooled under a protective atmosphere to obtain single-walled carbon nanotubes. The preparation method of the catalytically active iron-aluminum spinel catalyst in step (1) is as follows: Add ferric nitrate nonahydrate to deionized water and stir at 400-800 r / min for 10-20 min to completely dissolve the metal salt. Then transfer 2-5 ml of the ferric nitrate aqueous solution to an alumina ceramic boat and place the aluminum foil inside the boat. The mass ratio of the nonahydrated ferric nitrate to deionized water is 1~20:1; The preferred dimensions of the aluminum foil are 15*30*0.10~20*40*0.2mm; The aluminum foil contains more than 99.35% Al. The dimensions of the porcelain boat are 50*28*15~80*40*16mm; The aluminum foil is placed inside the ceramic boat: the aluminum foil can be located at any position in the solution, either at the bottom, inside, or on the surface.

[0013] The preferred mass ratio of ferric nitrate nonahydrate to deionized water in step (1) is 10:1; The preferred size of the aluminum foil in step (1) is 15*30*0.2mm; The preferred dimensions of the porcelain boat in step (1) are 50*28*15mm; In step (1), the preferred heating temperature of the reactor is 1000℃, and the calcination time is 0.5h. The preferred heating rate in step (2) is 10℃ / min; In step (2), the reaction temperature is 1000℃, H2 is introduced and reacted for 20 min, followed by CH4 being introduced and reacted for 40 min. In step (2), the inert gas flow rate is 300 sccm, the H2 flow rate is 100 sccm, and the CH4 flow rate is 40 sccm. This invention induces a transformation in the crystal structure of a catalyst through high-temperature calcination, forming active nanoparticles, thereby achieving the formation of defect-rich single-walled carbon nanotubes.

[0014] This invention obtains an Fe-Al spinel catalyst by placing aluminum foil and an aqueous solution of an active metal salt in a ceramic boat and then calcining it using CVD. Fe ions are immobilized within the crystal space constructed from Al and O. During reduction, the Fe ions escape from the metal-containing catalyst, forming catalytically active nanoparticles. On one hand, the reduced metal nanoparticles rapidly catalyze the growth of SWCNTs, preventing agglomeration and deactivation due to metal nanoparticle accumulation. On the other hand, due to the strong interaction between the metal oxide and the nanoparticles, the metal nanoparticles exhibit thermal stability at high temperatures, thus possessing catalytic activity. This method is more economical and environmentally friendly for product separation and purification. In summary, the strong interaction and catalyst escape mechanism allow the catalyst nanoparticles to remain in a small particle state, enabling the preparation of defect-rich single-walled carbon nanotubes.

[0015] Example 1 This embodiment provides a method for producing defect-rich single-walled carbon nanotubes, including the following steps: (1) Take 100mg Fe(NO3)3·9H2O, dissolve it in 10ml deionized water and stir evenly. Transfer 3ml of the solution to a ceramic boat, place an aluminum foil with a size of 15*30*0.10mm inside the solution, heat the reaction furnace to 1000℃ in an air atmosphere, set the heating program to 10℃ / min, and cool to room temperature after reacting for 1h to obtain a catalytically active iron-aluminum spinel catalyst. (2) Place the calcined metal catalyst from step (1) into a quartz boat and place the quartz boat into the CVD furnace. In the middle, connect the experimental apparatus as required, set the furnace heating program to 10℃ / min, and introduce Ar at a flow rate of 200 sccm to purge the air in the apparatus. After the sample temperature reaches 1000℃, introduce H2 at a flow rate of 200 sccm for 2 min. After the reaction is complete, turn off H2 and introduce CH4 at a flow rate of 40 sccm for 20 min. After the reaction is complete, stop heating and start cooling until the sample temperature reaches room temperature. Turn off Ar and finally take out the sample, which is a defect-rich single-walled carbon nanotube.

[0016] Figure 1 X-ray diffraction pattern of the iron-aluminum spinel catalyst; Figure 2 The image shows the Raman spectrum of the product prepared in Example 1.

[0017] Example 2 This embodiment provides a method for producing defect-rich single-walled carbon nanotubes, including the following steps: (1) Take 100mg Fe(NO3)3·9H2O, dissolve it in 10ml deionized water and stir evenly. Transfer 3ml of the solution into a porcelain boat, place an aluminum foil with a size of 15*30*0.10mm inside the solution, heat the reaction furnace to 660℃ in an air atmosphere, set the heating program to 10℃ / min, and cool to room temperature after reacting for 1h to obtain a catalytically active iron-aluminum spinel catalyst. (2) Place the calcined metal catalyst from step (1) into a quartz boat, place the quartz boat in the middle of the CVD furnace, connect the experimental device as required, set the furnace heating program to 10℃ / min, and introduce Ar at a flow rate of 200 sccm to purge the air in the device. After the sample temperature reaches 1000℃, introduce H2 at a flow rate of 200 sccm for 2 min. After the reaction is complete, turn off H2 and introduce CH4 at a flow rate of 40 sccm for 20 min. After the reaction is complete, stop heating and start cooling until the sample temperature reaches room temperature. Turn off Ar and finally take out the sample, which is a defect-rich single-walled carbon nanotube.

[0018] Comparative Example 1 The porcelain boat containing ferric nitrate aqueous solution and aluminum foil in step (1) was dried at 80°C. All other preparation steps were the same as the experimental process in Example 1.

[0019] Because it has not undergone air calcination, Fe-Al spinel catalyst cannot be formed, and defect-rich single-walled carbon nanotubes cannot be grown.

[0020] Comparative Example 2 The liquid precursor prepared in step (1) was placed in a tube furnace to directly grow single-walled carbon nanotubes. All other preparation steps were the same as those in Example 1.

[0021] Because it has not undergone air calcination, Fe-Al spinel catalyst cannot be formed, and defect-rich single-walled carbon nanotubes cannot be grown.

[0022] In summary, through comparative analysis of the products in Examples 1-2 and Comparative Examples 1-2, it can be determined that the formation of iron-aluminum spinel requires a high-temperature environment. Sufficient calcination in an air atmosphere above 600°C is crucial for activating the catalytic activity of the catalyst. Without this step, no long-term defective single-walled carbon nanotubes will form.

[0023] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing defect-rich single-walled carbon nanotubes, characterized in that, The preparation steps include the following: Step (1): Dissolve ferric nitrate nonahydrate in deionized water, place it and aluminum foil in a ceramic boat, heat the reactor to 600-1000℃ in an air atmosphere, react for 0.5-1h, and then cool to room temperature to obtain an iron-aluminum spinel catalyst with catalytic activity. Step (2): Place the iron-aluminum spinel catalyst in a tube furnace and heat it to 800-1000℃ in an inert gas atmosphere. Then, introduce H2 and react for 20-60 min, followed by introducing CH4 and reacting for 20-60 min. Then, stop the reaction and continue to cool in an inert gas atmosphere to obtain defect-rich single-walled carbon nanotubes. The preparation method of the catalytically active iron-aluminum spinel catalyst in step (1) is as follows: Add ferric nitrate nonahydrate to deionized water and stir at 400-800 r / min for 10-20 min to completely dissolve the metal salt. Then transfer 2-5 ml of the ferric nitrate aqueous solution to an alumina ceramic boat and place the aluminum foil inside the boat. The mass ratio of the nonahydrated ferric nitrate to deionized water is 1~20:1; The aluminum foil has dimensions of 15*30*0.10~20*40*0.2mm; The aluminum foil contains more than 99.35% Al. The dimensions of the porcelain boat are 50*28*15~80*40*16mm; The aluminum foil is placed inside the ceramic boat: the aluminum foil can be located at any position in the solution, either at the bottom, inside, or on the surface.

2. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, In step (1), the mass ratio of ferric nitrate nonahydrate to deionized water is 10:

1.

3. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, The aluminum foil in step (1) has a size of 15*30*0.2mm.

4. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, The porcelain boat in step (1) has dimensions of 50*28*15mm.

5. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, In step (1), the furnace is heated to 1000℃ and calcined for 0.5h.

6. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, The heating rate in step (2) is 10℃ / min.

7. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, In step (2), the reaction temperature is 1000℃, H2 is introduced and reacted for 20 minutes, followed by CH4 being introduced and reacted for 40 minutes.

8. The method for preparing defect-rich single-walled carbon nanotubes according to claim 1, characterized in that, In step (2), the inert gas flow rate is 300 sccm, the H2 flow rate is 100 sccm, and the CH4 flow rate is 40 sccm.

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