A hybrid-arranged carbon nanotube, its preparation method and application

Abstract

The present invention belongs to the technical field related to the preparation of nanomaterials, and discloses a hybrid arrangement of carbon nanotubes and its preparation method and application. The preparation method includes the following steps: S1: sequentially deposit an Al2O3 buffer layer and an Fe catalyst layer on a Si substrate or a SiO2 substrate, and then perform argon plasma etching; S2: perform the first annealing on the substrate, and after cooling, expose it to an oxygen-containing atmosphere to oxidize Fe; S3: perform the second annealing on the substrate, and then introduce H2, Ar, and C2H4 into the reaction chamber, and a hybrid arrangement of carbon nanotubes can be grown on the substrate through water-assisted chemical vapor deposition. By improving the process of the preparation method, the product obtained by the present invention is a hybrid arrangement of carbon nanotubes. Compared with a carbon nanotube array with a single orientation arrangement of horizontal or vertical orientation, it has a vertically oriented channel and a hierarchical pore structure, and has better performance when applied to energy storage devices.

Description

Technical Field

[0001] The present invention belongs to the technical field related to the preparation of nanomaterials, and more specifically, relates to a hybrid arrangement of carbon nanotubes and a preparation method and application thereof. Background Art

[0002] As a typical one-dimensional nanomaterial, carbon nanotubes exhibit important potential in the fields of energy storage (such as lithium-ion batteries, supercapacitors), catalytic carriers, gas adsorption and separation, etc. due to their high specific surface area, excellent electrical conductivity and mechanical properties. The traditional methods for preparing carbon nanotubes mainly include chemical vapor deposition, arc discharge method and laser ablation method. The carbon nanotubes prepared by chemical vapor deposition have a single structure, including horizontally or vertically oriented array structures. Among them, the horizontally arranged carbon nanotubes usually extend parallel to the substrate to form a dense conductive network, but the porosity is relatively low (<30%). The vertically arranged carbon nanotubes are usually arranged perpendicular to the substrate in an orderly manner to form nano-scale open channels, but the aggregation between the tube bundles is serious, reducing the connectivity between the pores. The arc discharge method uses a high current to evaporate a graphite electrode in an inert gas to generate multi-walled carbon nanotubes. The product usually presents a disordered entangled morphology, with a wide diameter distribution (10 nm to 100 nm), and is accompanied by a large amount of amorphous carbon impurities. The laser ablation method can prepare single-walled carbon nanotube bundles by bombarding a metal-doped graphite target with pulsed laser, but their arrangement direction is random, and the specific surface area is limited by the bundle aggregation effect. In addition, the template method (such as anodic aluminum oxide template) can regulate the carbon tube diameter through confined growth, but the template removal process is prone to cause structural collapse and it is difficult to achieve orientation control.

[0003] The above traditional methods generally have the problem of structural singularity, or are limited by a single orientation arrangement, resulting in limited mass transfer efficiency, or are restricted by disordered entanglement, reducing the connectivity of the conductive network. At the same time, they lack the ability to in-situ construct multi-level pores, seriously restricting the performance breakthrough of carbon nanotubes in the fields of energy storage, catalysis, etc. Especially under the development trend of miniaturization of new energy devices and extreme working conditions, single-structure carbon nanotubes can no longer meet the requirements of multi-functional integration. Summary of the Invention

[0004] In view of the above deficiencies or improvement requirements of the prior art, the purpose of the present invention is to provide a hybrid arrangement of carbon nanotubes and its preparation method and application. By improving the process of the preparation method, first, the Si substrate coated with Al2O3 and Fe is subjected to plasma etching, and the substrate is treated by a two-step annealing process. In this way, the carbon nanotubes generated by water-assisted chemical vapor deposition are hybrid arrangement carbon nanotubes. Compared with the carbon nanotube arrays with a single orientation arrangement of horizontal or vertical orientation, they have vertical oriented channels (as shown in the examples later, the diameter of the vertical oriented channels is 70 nm to 200 nm), and have a hierarchical pore structure (that is, they have micropores, mesopores and macropores at the same time), and have better performance. The hybrid arrangement carbon nanotubes obtained by the present invention have both vertical oriented channels and hierarchical pore structures, which can ensure the rapid transport of ions and improve the charge storage density, and are particularly suitable for use as electrodes in low-temperature supercapacitors (the low-temperature temperature can especially be -100 °C to -30 °C).

[0005] To achieve the above object, according to one aspect of the present invention, a method for preparing a hybrid arrangement of carbon nanotubes is provided, including the following steps:

[0006] S1: Magnetron sputtering method is used to sequentially deposit an Al2O3 buffer layer and an Fe catalyst layer on a Si substrate or a SiO2 substrate, and then argon plasma etching is carried out to roughen the Fe catalyst layer;

[0007] S2: The substrate obtained by processing in step S1 is heated in a flowing mixed gas of H2 and Ar for the first annealing, and after cooling, it is exposed to an oxygen-containing atmosphere to oxidize Fe;

[0008] S3: The substrate obtained by processing in step S2 is heated in a flowing mixed gas of H2 and Ar for the second annealing, and then H2, Ar and C2H4 are introduced into the reaction chamber, and hybrid arrangement carbon nanotubes can be grown on the substrate by water-assisted chemical vapor deposition.

[0009] As a further preference of the present invention, the annealing temperature used for the first annealing in step S2 is 750 °C to 780 °C, and the annealing time is 225 s to 350 s; in the flowing mixed gas of H2 and Ar, the gas flow ratio of H2 and Ar is 4:1;

[0010] The annealing temperature used for the second annealing in step S3 is 750 °C to 780 °C, and the annealing time is 225 s to 350 s; in the flowing mixed gas of H2 and Ar, the gas flow ratio of H2 and Ar is 4:1.

[0011] As a further preference of the present invention, in step S1, the etching time of argon plasma etching is 5 minutes to 30 minutes, and the etching power range is 5 W to 40 W.

[0012] As a further preference of the present invention, in step S2, the oxygen-containing atmosphere is air;

[0013] The exposure to the oxygen-containing atmosphere is specifically placing in air for at least 30 minutes.

[0014] As a further preference of the present invention, in step S3, the flow rate ratio of H2, Ar and C2H4 gases used in the water-assisted chemical vapor deposition is 2:7:4, the water vapor concentration is 75 ppm, and the growth time of the water-assisted chemical vapor deposition is 22 minutes to 35 minutes.

[0015] In another aspect of the present invention, the present invention provides a mixed arrangement of carbon nanotubes prepared by the above preparation method.

[0016] As a further preference of the present invention, the mixed arrangement of carbon nanotubes has a vertically oriented channel, and the diameter of the vertically oriented channel is 100 nm to 200 nm.

[0017] In yet another aspect of the present invention, the present invention provides an application of the above mixed arrangement of carbon nanotubes as an electrode material in an energy storage device.

[0018] As a further preference of the present invention, the application is at a temperature of -100 °C to 20 °C.

[0019] In still another aspect of the present invention, the present invention provides an application of the above mixed arrangement of carbon nanotubes as an electrode material in promoting the capacity retention rate of an energy storage device under low-temperature conditions, and the low-temperature conditions are -100 °C to -50 °C.

[0020] Through the above technical solution conceived by the present invention, different from the carbon nanotubes generated by the water-assisted chemical vapor deposition after the one-step annealing process of the Si substrate coated with Al2O3 and Fe in the prior art, the preparation method of the present invention needs to first perform plasma etching on the Si substrate coated with Al2O3 and Fe to change the roughness of the catalyst layer. Then, two-step annealing treatment is also required. An oxidation operation needs to be carried out before the second annealing treatment (wherein, the first annealing can form uniformly distributed catalyst nanoparticles, the oxidation operation can oxidize the catalyst nanoparticles and anchor them on the buffer layer, and the second annealing can reactivate the catalyst nanoparticles and achieve a distributed state of a focused state of isolation), and finally, water-assisted chemical vapor deposition is carried out to generate a mixed arrangement of carbon nanotubes.

[0021] Correspondingly, different from the horizontally or vertically oriented single - oriented carbon nanotube array structures prepared in the prior art, the carbon nanotubes obtained by the method of the present invention are mixed - arranged carbon nanotubes. On the one hand, they have both vertically - grown nanotube bundles and randomly - oriented nanotube bundles at the same time. The randomly - oriented nanotube bundles serve as a lateral framework to support the vertically - grown nanotube bundles. On the other hand, the mixed - arranged carbon nanotubes also have vertically - oriented channels and a hierarchical pore structure with micropores, mesopores, and macropores simultaneously. As shown in the following examples, the diameter size of the vertically - oriented channels d in the mixed - arranged carbon nanotubes can be distributed in the range of 70 nm to 200 nm. Due to the differences in the structures of the carbon nanotube materials, the mixed - arranged carbon nanotubes in the present invention are more suitable as electrode materials in extremely low - temperature environments compared with the single - oriented carbon nanotube array structures in the prior art. The working temperature of the corresponding device can be as low as - 100 °C and can maintain a high capacity in an extremely low - temperature environment (of course, it can also be used as an electrode material at room temperature of 20 °C; that is to say, the working temperature range can be from - 100 °C to 20 °C).

[0022] Before growing carbon nanotubes by the method of the present invention, the Si substrate deposited with Al2O3 and Fe is first etched to increase the surface roughness, improve the migration potential energy of metal atoms, and inhibit the aggregation or combination between metal particles. After the first annealing, the Si substrate is taken out and exposed to air to oxidize the Fe catalyst nanoparticles and "anchor" them on the buffer layer. Then, the second annealing is carried out to re - activate the Fe catalyst nanoparticles, realizing the distribution of aggregated and isolated states. The carbon nanotubes grown from the aggregated Fe catalyst nanoparticles show vertical growth due to the strong van der Waals force interaction. While the carbon nanotubes grown from the isolated Fe catalyst nanoparticles show random - direction growth due to the weak van der Waals force, thus obtaining mixed - arranged carbon nanotubes with a vertically - oriented channel structure and a hierarchical pore distribution.

[0023] Specifically, the present invention can achieve the following beneficial effects.

[0024] 1. The mixed - arranged carbon nanotubes obtained by the present invention have vertically - oriented channels and a hierarchical pore structure, which can improve the electrochemical performance of energy - storage devices. Taking the following examples as an example, the specific capacitance of the supercapacitor assembled with the mixed - arranged carbon nanotubes is 31.6 F / g at 20 °C, which is 184% higher than that of the vertical carbon nanotube array. Even at - 100 °C, the specific capacitance of this supercapacitor is still 30.2 F / g, and the capacitance retention rate is as high as 95.6%.

[0025] 2. The present invention can especially obtain mixed - arranged carbon nanotubes, the diameter size of whose vertically - oriented channels is distributed in the range of 70 nm to 200 nm, and which have a hierarchical pore structure with micropores, mesopores, and macropores simultaneously.

[0026] 3. The mixed-alignment carbon nanotubes prepared by the method of the present invention greatly improve the ion transport efficiency. Taking Example 1 hereinafter as an example, the tortuosity of the ion transport path of the mixed-alignment carbon nanotubes is 1.20, which greatly reduces the tortuosity of the ion transport path and realizes fast ion transport (the tortuosity of the ion transport path of the vertical carbon nanotube array obtained in Comparative Example 1 is 2.76).

[0027] 4. The mixed-alignment carbon nanotubes prepared by the method of the present invention can provide more charge adsorption sites and significantly improve the capacity of the electrode material.

[0028] In summary, the present invention obtains a carbon nanotube material with a synchronous realization of a multi-structure mixed alignment, which changes the practice of separately regulating the alignment direction and pore structure in the traditional process, realizes the synchronous design and precise control of both, and promotes the application of carbon-based materials in the fields of efficient energy storage and the like. Description of the Drawings

[0029] Figure 1 It is a schematic process diagram of the preparation method of the mixed-alignment carbon nanotubes in the present invention.

[0030] Figure 2 It is the SEM diagram of the carbon nanotubes prepared in Example 1, Example 2 and Comparative Example 1, wherein Figure 2 (a) therein corresponds to the mixed-alignment carbon nanotubes prepared in Example 1, Figure 2 (b) therein corresponds to the mixed-alignment carbon nanotubes prepared in Example 2, Figure 2 (c) therein corresponds to the vertical carbon nanotube array prepared in Comparative Example 1.

[0031] Figure 3 It is the constant current charge and discharge curves of the electrodes prepared from the carbon nanotube materials prepared in Comparative Example 1, Example 1 and Example 2 at -100°C to 20°C; wherein, Figure 3 (a) therein corresponds to the vertical carbon nanotube array prepared in Comparative Example 1, Figure 3 (b) therein corresponds to the mixed-alignment carbon nanotubes prepared in Example 2, Figure 3 (c) therein corresponds to the mixed-alignment carbon nanotubes prepared in Example 1.

[0032] Figure 4 It is the capacity comparison diagram of the electrodes prepared from the mixed-alignment carbon nanotube materials prepared in Example 1 and Example 2 and the electrode prepared from the vertical carbon nanotube array prepared in Comparative Example 1 at -100°C to 20°C.

[0033] Figure 5 It is the tortuosity comparison diagram of the ion transport paths of the mixed-alignment carbon nanotubes prepared in Example 1 and Example 2 and the vertical carbon nanotube array prepared in Comparative Example 1. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] As Figure 1 shown, in the preparation method of the hybrid-aligned carbon nanotubes in the present invention, first, a Si substrate coated with Al2O3 and Fe is etched by reactive ion etching (Al2O3 is an intermediate buffer layer, located on the upper surface of the Si substrate and in direct contact with the Si substrate; Fe is located above the Al2O3 layer), then a first annealing treatment is carried out, after which it is taken out and placed in the air (for example, placed for 30 minutes), and then a second annealing is carried out, and subsequent water-assisted chemical vapor deposition growth is directly carried out after the end of the second annealing (the growth time can be 22 minutes).

[0036] The following are specific embodiments.

[0037] Example 1

[0038] It includes the following steps:

[0039] (1) First, a 30-nm-thick Al2O3 buffer layer is deposited on a clean Si substrate by magnetron sputtering, and then a 2-nm-thick Fe catalyst layer is deposited. It is placed in the reaction chamber of a reactive ion etching instrument and etched by argon plasma. During the etching process, the Ar flow rate is 30 sccm, the etching time is 5 minutes, and the etching power is 30 W, making the Fe thin film of the catalyst layer rough.

[0040] (2) The Si substrate obtained in step (1) is placed in a tube furnace and heated to 750 °C in H2 (800 sccm) and Ar gas (200 sccm) for the first annealing, and the annealing time is 300 s, which makes the catalyst layer form uniformly distributed Fe nanoparticles on the surface. After cooling, the annealed Si substrate is removed from the tube furnace and exposed to the air for 30 minutes of oxidation treatment, so that the catalyst Fe nanoparticles are oxidized and "anchored" on the Al2O3 buffer layer. After oxidation, the Si substrate is placed in the tube furnace again and annealed for the second time at 750 °C in H2 (800 sccm) and Ar gas (200 sccm), and the annealing time is 300 s.

[0041] (3) After annealing treatment, without moving the sample and still keeping the sample in the tube furnace, then use Ar, H2 and C2H4 (where the Ar gas flow rate is 350 sccm, the H2 gas flow rate is 100 sccm, and the C2H4 gas flow rate is 200 sccm) to carry out water-assisted chemical vapor deposition at 1 atm, control the water vapor concentration to be 75 ppm (the water vapor is introduced in the form of water-carrying argon; the same below), grow the mixed-alignment carbon nanotubes using C2H4 as the carbon source at 750 °C, and the growth time is 22 minutes.

[0042] The SEM image of the obtained mixed-alignment carbon nanotubes is as Figure 2 shown in (a) of [reference], the randomly oriented nanotube bundles act as a lateral framework to support the vertically grown nanotube bundles, forming vertical-oriented channels and a hierarchical pore structure, and the diameter of the vertical-oriented channels is 100 nm - 200 nm. Further detection shows that the thickness of the mixed-alignment carbon nanotubes is 500 μm, the porosity is 98.8%, and the specific surface area is 487 cm 2 / g. The pore diameters include micropores (<2 nm), mesopores (3 - 4 nm), and macropores (>50 nm). It is denoted as the "d: 100 - 200 nm" sample.

[0043] Example 2

[0044] It includes the following steps:

[0045] (1) First deposit a 30-nm-thick Al2O3 buffer layer on a clean Si substrate by magnetron sputtering, and then deposit a 2-nm-thick Fe catalyst layer. Place it in the reaction chamber of the reactive ion etching instrument and etch it through argon plasma. During the etching process, the Ar flow rate is 30 sccm, the etching time is 5 minutes, and the etching power is 20 W to make the Fe thin film of the catalyst layer rough.

[0046] (2) The same as step (2) of Example 1.

[0047] (3) The same as step (3) of Example 1.

[0048] The SEM image of the mixed-alignment carbon nanotubes prepared in this example is as Figure 2 shown in (b) of [reference], the randomly oriented nanotube bundles act as a lateral framework to support the vertically grown nanotube bundles, forming vertical-oriented channels and a hierarchical pore structure, and the diameter of the vertical-oriented channels is 70 nm - 120 nm. Further detection shows that the thickness of the mixed-alignment carbon nanotubes is 501 μm, the porosity is 98.7%, and the specific surface area is 525 cm 2 / g. The pore diameters include micropores (<2 nm), mesopores (3 - 0 nm), and macropores (>50 nm). It is denoted as the "d: 70 - 120 nm" sample.

[0049] By comparing Example 1 with Example 2, it is not difficult to see that when preparing the hybrid-aligned carbon nanotubes of the present invention, the diameter size of the vertical orientation channels of the hybrid-aligned carbon nanotubes can be regulated by adjusting the reactive ion etching power.

[0050] Comparative Example 1

[0051] This comparative example is to prepare a vertical carbon nanotube array, without using argon plasma etching and without using two-step annealing (only using one-step annealing), including the following steps:

[0052] (1) First deposit a 30-nm-thick Al2O3 buffer layer on a clean Si substrate by magnetron sputtering, and then deposit a 2-nm-thick Fe catalyst layer.

[0053] (2) Put the above Si substrate into a tube furnace, introduce H2 and Ar (the total gas flow rate is 1000 sccm, where the Ar gas flow rate is 800 sccm and the H2 gas flow rate is 200 sccm), and heat the tube furnace to 750 °C within 800 s.

[0054] (3) After the tube furnace is heated to 750 °C, perform annealing in a gas atmosphere of H2 and Ar (the total gas flow rate is 1000 sccm, where the Ar gas flow rate is 200 sccm and the H2 gas flow rate is 800 sccm), and the annealing time is 300 s.

[0055] (4) Set the growth temperature to 750 °C and the water vapor concentration to 75 ppm. Use Ar, H2, and C2H4 (where the Ar gas flow rate is 350 sccm, the H2 gas flow rate is 100 sccm, and the C2H4 gas flow rate is 200 sccm) to perform water-assisted chemical vapor deposition at 1 atm to grow a vertical carbon nanotube array, and the growth time is 22 minutes.

[0056] The SEM image of the product obtained in this comparative example is as shown in Figure 2 (c). It can be seen that the product is a vertical carbon nanotube array, but the tube bundles are relatively dense and there are almost no macropores. Further detection shows that the thickness of the vertical carbon nanotube array obtained in this comparative example is 502 μm, the porosity is 98.7%, the specific surface area is 470 cm 2 / g, and the pore diameter is mainly concentrated in mesopores (34 nm), with basically no micropores and no macropores.

[0057] Performance detection:

[0058] In addition, in order to characterize the electrochemical performance of energy storage devices in extremely low temperature environments, the hybrid-aligned carbon nanotubes with different vertically oriented channel diameters prepared in Example 1 and Example 2 and the vertically aligned carbon nanotube array prepared in Comparative Example 1 were used to fabricate electrodes for testing. The specific operations are as follows: The hybrid-aligned carbon nanotubes with different vertically oriented channel diameters and the vertically aligned carbon nanotube array were used as electrode materials respectively, and the electrolyte used was a mixed electrolyte (i.e., a mixed solution of 1 M MeEt3NBF4, DOL, and acetonitrile) to assemble supercapacitors (the supercapacitors only differed in electrode materials, and other components and detailed parameter conditions were all the same). The temperature range for testing was from 20 °C to -100 °C, and the constant current charge-discharge curves of the hybrid-aligned carbon nanotube electrodes with different vertically oriented channel diameters and the vertically aligned carbon nanotube array were tested at -100 °C to 20 °C. The potential was 2.7 V and the current density was 1 A / g. The results are as Figure 3 shown. As can be seen from Figure 3 (a) in, for the vertically aligned carbon nanotube array of Comparative Example 1, as the temperature decreased from 20 °C to -100 °C, its charge-discharge time significantly gradually shortened. For the hybrid-aligned carbon nanotubes with a vertically oriented channel diameter d of 70 - 120 nm prepared in Example 2 (i.e., the "d: 70 - 120 nm" sample), as Figure 3 (b) in shows, the trend of its charge-discharge time gradually shortening with the decrease in temperature was alleviated. For the hybrid-aligned carbon nanotubes with a vertically oriented channel diameter d of 100 - 200 nm prepared in Example 1 (i.e., the "d: 100 - 200 nm" sample), as Figure 3 (c) in shows, with the decrease in temperature, the change in charge-discharge time was the smallest.

[0059] According to Figure 3 the constant current charge-discharge curves, the capacities of the devices assembled with the hybrid-aligned carbon nanotubes obtained in Example 1 and Example 2 and the vertically aligned carbon nanotube array obtained in Comparative Example 1 at different temperatures were calculated, as shown in Table 1 and Figure 4As shown, it is not difficult to see that compared with the product of Comparative Example 1, the products of Example 1 and Example 2 can promote the capacity retention rate of the energy storage device at -50°C to -100°C (among which, the effect of Example 1 is the best). At 20°C and -100°C, the capacities of the devices assembled with the vertical carbon nanotube arrays of Comparative Example 1 are 11.1 F / g and 2.6 F / g respectively (the capacity at -100°C decreased by 76.6% compared with that at 20°C), the capacities of the devices assembled with the hybrid-aligned carbon nanotubes of Example 2 are 19.8 F / g and 12.5 F / g respectively (the capacity at -100°C decreased by 36.9% compared with that at 20°C, and the decrease rate decreased significantly), and the capacities of the devices assembled with the hybrid-aligned carbon nanotubes of Example 1 are 31.6 F / g and 30.2 F / g respectively (the capacity at -100°C only decreased by 4.4% compared with that at 20°C, and the decrease rate is almost negligible). Thus, it can be seen that the device assembled with the hybrid-aligned carbon nanotubes with d of 100 - 200 nm in Example 1 has the largest capacity in the temperature range from 20°C to -100°C, and the capacity retention rate is as high as 95.6%:

[0060]

[0061] In addition, referring to the known methods in the prior art (e.g., Pouraghajan, F.; Knight, H.; Wray, M.; Mazzeo, B.; Subbaraman, R.; Christensen, J.; Wheeler, D. Quantifying Tortuosity of Porous Li-Ion Battery Electrodes: Comparing Polarization-Interrupt and Blocking-Electrolyte Methods. J. Electrochem. Soc. 2018, 165, A2644. DOI: https: / / doi.org / 10.1149 / 2.0611811jes.), the tortuosity of the ion transport paths of the vertical carbon nanotube arrays in Comparative Example 1 and the hybrid-aligned carbon nanotubes in Examples 1 and 2 at room temperature can be calculated, and the results are as Figure 5 shown. The tortuosity of the ion transport path of the vertical carbon nanotube arrays in Comparative Example 1 is the largest, which is 2.76; the tortuosity of the ion transport paths of the hybrid-aligned carbon nanotubes in Examples 2 and 1 are 1.80 and 1.20 respectively. Thus, it can be seen that the "d: 100 - 200 nm" sample has more suitable vertically oriented channels, greatly reducing the tortuosity of the ion transport path and improving the capacity of the device.

[0062] The above embodiments are only examples. The thickness of the mixed-arrangement carbon nanotubes can be adjusted by the growth time. According to actual needs, the thickness of the mixed-arrangement carbon nanotubes can also take other values (for example, other thicknesses within the range of 200 μm to 1000 μm). The gas flow ratios of H2, Ar, and C2H4 and the water vapor concentration used in the water-assisted chemical vapor deposition growth of the mixed-arrangement carbon nanotubes can all be adjusted according to the actual situation. In addition to the Si substrate, a SiO2 substrate can also be used.

[0063] In addition, the micropores, mesopores, and macropores appearing in the present invention satisfy the conventional definitions. The pore diameter of the micropores is less than 2 nm, the pore diameter of the mesopores is between [2 nm, 50 nm], and the pore diameter of the macropores is >50 nm.

[0064] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should all be included within the protection scope of the present invention.

Claims

1. A preparation method of hybrid-arranged carbon nanotubes, characterized in that, It includes the following steps: S1: Deposit an Al2O3 buffer layer and an Fe catalyst layer on a Si substrate or a SiO2 substrate in sequence by magnetron sputtering method, and then perform argon plasma etching to roughen the Fe catalyst layer; S2: Heat the substrate obtained in step S1 in a flowing mixed gas of H2 and Ar for the first annealing, and after cooling, expose it to an oxygen-containing atmosphere to oxidize Fe; S3: Heat the substrate obtained in step S2 in a flowing mixed gas of H2 and Ar for the second annealing, and then introduce H2, Ar, and C2H4 into the reaction chamber, and aligned multi-walled carbon nanotubes can be grown on the substrate by water-assisted chemical vapor deposition.

2. The preparation method according to claim 1, wherein For the first annealing in step S2, the annealing temperature is 750 °C to 780 °C, and the annealing time is 225 s to 350 s; in the flowing mixed gas of H2 and Ar, the gas flow ratio of H2 to Ar is 4:1; For the second annealing in step S3, the annealing temperature is 750 °C to 780 °C, and the annealing time is 225 s to 350 s; in the flowing mixed gas of H2 and Ar, the gas flow ratio of H2 to Ar is 4:

1.

3. The preparation method according to claim 1, characterized in that, In step S1, the etching time of argon plasma etching is 5 minutes to 30 minutes, and the etching power range is 5 W to 40 W.

4. The preparation method according to claim 1, wherein, In step S2, the oxygen-containing atmosphere is air; The exposure to the oxygen-containing atmosphere is specifically placing it in air for at least 30 minutes.

5. The preparation method according to claim 1, characterized in that, In step S3, the gas flow ratio of H2, Ar, and C2H4 used in the water-assisted chemical vapor deposition is 2:7:4, the water vapor concentration is 75 ppm, and the growth time of the water-assisted chemical vapor deposition is 22 minutes to 35 minutes.

6. The aligned multi-walled carbon nanotubes prepared by the preparation method according to any one of claims 1-5.

7. The hybrid-arranged carbon nanotubes according to claim 6, wherein The aligned multi-walled carbon nanotubes have vertically oriented channels, and the diameter of the vertically oriented channels is 100 nm to 200 nm.

8. The application of the aligned multi-walled carbon nanotubes according to claim 6 or 7 as an electrode material in an energy storage device.

9. The application according to claim 8, wherein, The application is at a temperature of -100 °C to 20 °C.

10. Use of the hybrid-arranged carbon nanotubes as an electrode material according to claim 6 or 7 in promoting the capacity retention rate of an energy storage device under low-temperature conditions, characterized in that, The low temperature condition is -100 °C to -50 °C.

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