CVD in-situ growth graphene carbon nanotube composite material and preparation method thereof

Abstract

The invention relates to the technical field of nanometer material synthesis, and discloses a CVD in-situ growth graphene carbon nanotube composite material and a preparation method thereof. The preparation method comprises the following steps: step 1, introducing carbon source gas I into a metal material template with a foam structure, and growing three-dimensional graphene by chemical vapor deposition; 2, defects are introduced into the surface of the graphene obtained in the step 1; and 3, introducing a carbon source gas II, and performing chemical vapor deposition on the surface of the graphene obtained in the step 2 to grow a carbon nanotube in situ, thereby obtaining the composite material. The obtained composite material is good in microscopic network structure stability and not prone to collapse, the growth consistency of the carbon nanotubes is good, and the composite material can be prepared on a large scale and applied to energy storage devices.

Description

Technical Field

[0001] The invention relates to the technical field of nano material synthesis, and in particular to a CVD in-situ grown graphene carbon nanotube composite material and a preparation method thereof. Background Art

[0002] Graphene-carbon nanotube composites have potential application prospects in energy storage devices. At present, the preparation methods of graphene-carbon nanotube composites mainly include chemical vapor deposition and solution assembly. Among them, the CVD method has become a hot topic of research because of its strong controllability and high quality of the prepared composite materials. For example, the invention patent applications with publication numbers CN117736580A, CN103303901B, CN108461305A, CN113044830A, etc. all disclose the process of preparing graphene-carbon nanotube composites by CVD. In addition, Zhang et al. (Zhang Ning, Preparation of three-dimensional graphene / carbon nanotube composites and research on their capacitance properties, Chongqing University, master's thesis) transferred the graphene film grown by CVD on the surface of copper foil to a substrate deposited with a metal catalyst, and further prepared a graphene-carbon nanotube composite by CVD growth.

[0003] However, the existing CVD method for preparing graphene-carbon nanotube composites still has the following shortcomings: 1. Insufficient conductive network construction: The existing method is difficult to grow CNTs uniformly on three-dimensional graphene, which affects the efficiency of electron transmission. 2. Insufficient structural stability: The composite materials prepared by the existing CVD method are prone to collapse during long-term use, resulting in attenuation of electrochemical performance. 3. Complex preparation process and high cost: The existing CVD method is difficult to accurately control the growth position and density of carbon nanotubes, which affects the consistency of the composite material and limits large-scale preparation and application.

[0004] Therefore, it is urgent to develop new preparation methods to overcome the above challenges. Summary of the invention

[0005] The technical problem to be solved by the present invention is to develop a new method for preparing three-dimensional graphene carbon nanotube composite materials, so as to overcome the problems of insufficient structural construction, insufficient structural stability, complex preparation process and high cost of graphene carbon nanotube composite materials prepared by existing CVD methods.

[0006] To solve the above problems, the present invention first provides a method for preparing a CVD in-situ grown graphene carbon nanotube composite material, comprising the following steps: Step 1: introducing carbon source gas I into a metal material template having a foam structure to grow three-dimensional graphene by chemical vapor deposition; Step 2, introducing defects on the surface of the graphene obtained in step 1; Step 3: introducing carbon source gas II to chemically vapor deposit and grow carbon nanotubes on the surface of the graphene obtained in step 2 to obtain a composite material.

[0007] Compared with the prior art, the graphene-carbon nanotube composite material prepared by the present invention has the following significant advantages: the graphene presents a three-dimensional structure and forms a close bond with the carbon nanotubes, so that the obtained composite material has high stability. The structure constructs a microscopic network of three-dimensional graphene + one-dimensional carbon nanotubes, ensuring good mechanical strength and conductivity, and effectively preventing material collapse. In addition, the growth consistency of carbon nanotubes is high, which can achieve large-scale preparation and meet the needs of industrial applications.

[0008] In one possible implementation, the metal material template with a foam structure in step 1 is selected from at least one of nickel foam, iron foam, copper foam, cobalt foam, iron-nickel alloy foam, copper-iron alloy foam, iron-cobalt alloy foam, copper-nickel alloy foam, cobalt-nickel alloy foam, copper-cobalt alloy foam, iron-nickel-copper alloy foam, cobalt-nickel-copper alloy foam, cobalt-nickel-copper alloy foam, and iron-nickel-cobalt alloy foam; In a possible implementation, the carbon source gas I in step 1 chemical vapor deposition is a low molecular weight hydrocarbon.

[0009] In a possible implementation, the temperature of the chemical vapor deposition in step 1 is 800-1200° C., the flow rate of the carbon source gas I is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

[0010] In the above scheme, a metal material substrate with a foam structure is selected as a template for CVD growth of graphene, and the multi-dimensionality and multi-contact surface of the foam can be used to grow three-dimensional graphene. These metal materials with foam structures can be 3D printed structures, metal meshes, or nickel, iron, copper, and cobalt sacrificial templates with porous structures. The CVD process in step one involves multiple key parameters, including but not limited to: the growth temperature is controlled at 800-1200 ° C to regulate the number and quality of graphene layers; the gas flow rate range is usually set to 10-200 sccm to optimize the carbon source supply rate; the deposition time can be adjusted according to the required thickness, generally between 5-60 min. In addition, the chamber pressure (1-100 Torr), the carrier gas type (hydrogen, argon or helium) and their ratio need to be controlled to optimize the crystallinity and uniformity of graphene. The protective atmosphere can make the grown three-dimensional graphene products less contaminated, high in purity, and good in consistency. If there are other key process conditions that affect the graphene growth quality or the performance of the composite material, the relevant parameters can be further optimized to improve the controllability and applicability of the material.

[0011] In one possible implementation, in step one, a reducing gas is introduced before chemical vapor deposition to activate the foam material template, and the reducing gas is a hydrogen-carrying nitrogen and / or hydrogen-carrying argon atmosphere, and the hydrogen content of the reducing gas is 1-25%.

[0012] Through the above technical solution, hydrogen reduction and activation of the template increases the surface cleanliness of the template and the surface roughness, making it more suitable for growing three-dimensional graphene products. The role of hydrogen is to provide a reducing environment, promote the activation of the template and the high-quality growth of graphene, while nitrogen or argon can be used to regulate the gas phase environment, reduce the carbon deposition rate and optimize the structural uniformity of the material.

[0013] In a possible implementation, step one further includes the steps of purging and vacuum treating the CVD system before activating the material template having the foam structure.

[0014] In a possible implementation, the defects introduced in step 2 are formed by high temperature oxidation etching on the surface of the graphene obtained in step 1 to form defect active sites.

[0015] In a possible implementation, the operation of high temperature oxidation etching is: placing the graphene material obtained in step 1 in air, oxygen or O2 / N2 mixed gas, cutting off the supply of hydrogen, introducing inert gas at the same time, heating and oxidation etching at 800-1200°C for 5-60 min. Heat treatment at a temperature range of 800-1200°C can remove surface organic matter or regulate surface chemical properties and roughness, forming an oxide layer that is conducive to subsequent carbon source deposition.

[0016] In a possible implementation, the carbon source gas II in step three is low molecular weight hydrocarbons.

[0017] In a possible implementation manner, in step three, the temperature of chemical vapor deposition is 800-1200° C., the gas flow rate is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

[0018] In the above technical solution, low molecular hydrocarbons are preferably hydrocarbon gases such as methane, acetylene, ethylene, propane, etc. that are suitable for CVD processes to ensure high-quality growth of carbon nanotubes. The growth temperature is 800-1200 °C to optimize the morphology and quality of carbon nanotubes; the gas flow rate is 10-200 sccm to regulate the growth rate and carbon source supply; the deposition time is 5-60 min to control the length and density of carbon nanotubes. In addition, the chamber pressure (1-100 Torr), carrier gas type (such as argon, hydrogen, helium) and their ratio need to be optimized to ensure a stable growth environment and suppress non-uniform deposition.

[0019] The present invention also provides a CVD in-situ grown graphene carbon nanotube composite material, which is prepared by the above-mentioned preparation method and is applied to energy storage devices.

[0020] The beneficial effects of the present invention are: The present invention uses a metal material with a foam structure as a template matrix to prepare a composite material in which the graphene is a three-dimensional graphene structure, and then catalytically grows one-dimensional carbon nanotubes on the surface of the three-dimensional graphene with defects to obtain a three-dimensional graphene-carbon nanotube composite material. The whole process is simple and controllable to operate, and the structure and arrangement of the graphene and the carbon nanotubes can be accurately controlled. The obtained composite material has good consistency and can be prepared and applied on a large scale.

[0021] The CVD process of the present invention has low temperature and simple steps, which reduces manufacturing difficulty and cost and is suitable for large-scale preparation and application.

[0022] An efficient "three-dimensional + one-dimensional" conductive network is constructed in the composite material prepared by the present invention, which improves the specific capacity, cycle stability and rate performance of the material and has broad application prospects in energy storage devices.

[0023] The three-dimensional graphene-CNTs composite material obtained by the present invention has a specific capacity of 35.2 F / g, which is significantly better than single graphene or CNTs materials. It can still maintain a high specific capacitance under high current density, and the material has excellent rate performance, which is suitable for high-power energy storage devices. After 10,000 cycles, the capacitance retention rate reaches 99%, and the cycle stability is enhanced, which can greatly improve the life of the energy storage device. CNTs grown in situ by CVD provide an efficient electron transmission channel, improve the overall conductivity and ion diffusion capacity of the material, and reduce the charge transfer resistance. By optimizing the CVD growth parameters, the controllable growth of CNTs on the graphene matrix is ​​achieved, the consistency and repeatability of the material are guaranteed, the preparation cost is reduced, and the potential for industrial application is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a microscopic morphology diagram of the three-dimensional graphene of the present invention; Figure 2 is a microscopic morphology diagram of the carbon nanotube of the present invention; Figure 3 A microscopic morphology diagram of the three-dimensional graphene-carbon nanotube composite material of the present invention; Figure 4 is the XRD diagram of the three-dimensional graphene-carbon nanotube composite material of the present invention; Figure 5 A Raman spectrum of the three-dimensional graphene-carbon nanotube composite material of the present invention; Figure 6This is a transmission electron microscope picture of the three-dimensional graphene-carbon nanotube composite material of the present invention, in which Gr represents graphene and CNT represents carbon nanotube; Figure 7 The specific capacity performance test results of the three-dimensional graphene-carbon nanotube composite material of the present invention; Figure 8 This is the cyclic stability test result of the three-dimensional graphene-carbon nanotube composite material of the present invention. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0026] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0027] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0028] The present invention discloses a method for preparing a CVD in-situ grown graphene carbon nanotube composite material, comprising the following steps: Step 1: Use a metal material substrate with a foam structure as a template, and chemically clean the template before growth to remove the surface oxide layer, improve its catalytic activity and graphene nucleation density. Use nitrogen or argon to purge the system, then perform vacuum treatment, and then introduce hydrogen carrier gas to activate the substrate, that is, gradually increase the temperature to 800-1200 ° C, and introduce hydrogen at a flow rate of 10-200 sccm to activate the foam substrate for 5-60 min; the hydrogen carrier gas is a hydrogen-carrying nitrogen and / or hydrogen-carrying argon atmosphere, and the proportion of hydrogen in the reducing gas is 1-25%. Then, at a high temperature of 800-1200 ° C and a pressure of 1-100 Torr, carbon source gas I is introduced, preferably at 950-1050 ° C, and high specific surface area three-dimensional graphene is grown by chemical vapor deposition. The flow rate of carbon source gas I is controlled at 10-200 sccm to regulate the carbon supply rate and avoid excessive deposition. The deposition time is in the range of 5-60 min. The carbon source gas I is preferably a low molecular hydrocarbon, more preferably at least one of methane, acetylene, ethylene and propane. Hydrogen / argon or hydrogen / nitrogen mixed gas can be introduced as needed, that is, in addition to the aforementioned carbon source and hydrogen, argon or nitrogen is introduced as a protective atmosphere to adjust the gas composition to optimize the growth environment and inhibit the formation of amorphous carbon, thereby improving the crystallization quality of graphene. The grown three-dimensional graphene is also cooled to room temperature under the protection of an inert gas atmosphere.

[0029] Step 2: Introduce defects on the graphene surface obtained in step 1 by high temperature oxidation etching, form defect active sites on the graphene surface, and increase the growth sites of carbon nanotubes; the specific operation includes placing the prepared three-dimensional graphene material in an oxidizing atmosphere, and heating it in the temperature range of 800-1200 ° C. The oxidation time can be adjusted according to the required conditions, usually between 5-60 minutes. This process can effectively adjust the surface roughness and defect concentration of graphene, thereby optimizing the subsequent growth uniformity and bonding strength of carbon nanotubes.

[0030] Step 3: introduce carbon source gas II, and chemically vapor deposit carbon nanotubes on the surface of the graphene obtained in step 2 to obtain a composite material. The flow rate of carbon source II gas is 10-200 sccm, the deposition temperature is 750-900 ° C, the deposition pressure is 1-100 Torr, and the deposition time is 5-60 min. During the deposition of carbon nanotubes, argon gas is introduced as a protective atmosphere, and the ratio of carbon source and argon gas flow is adjusted to ensure a stable growth environment and inhibit non-uniform deposition; by adjusting the flow rate and growth time of carbon source gas II, the density and diameter of CNTs are accurately controlled. The larger the flow rate of carbon source gas II, the longer the growth time, the greater the density of CNTs, and the larger the diameter. Carbon source gas II is preferably a low molecular hydrocarbon, more preferably at least one of methane, acetylene, ethylene, and propane.

[0031] XRD (X-ray diffraction) was used to determine the phase composition of the composites.

[0032] SEM / TEM (scanning electron microscopy / transmission electron microscopy) was used to analyze the microstructure of the composite materials and the distribution of CNTs.

[0033] Raman spectroscopy was used to determine the graphene defect density and the carbon structure of CNTs.

[0034] The capacitance decay was evaluated by medium- and long-term cycle testing in 1M H2SO4 or 1M Na2SO4 electrolyte.

[0035] The characterization and test results of the composite materials are shown in Figure 1-Figure 8 As shown. Figure 1-3 , Figure 6 It can be seen from the microscopic morphology that the composite material is composed of graphene and carbon nanotubes. The carbon nanotubes are distributed on the three-dimensional graphene surface. The composite material microscopic three-dimensional + one-dimensional conductive network is successfully constructed with good stability and consistency. Figure 4-5 The results also prove that the composite material is composed of graphene and carbon nanotubes. Figure 7 The test results show that the specific capacity of the composite material reaches 35.2 F / g, which is significantly better than single graphene or CNTs materials. Figure 8 It can be seen from the cycle stability test results that a high specific capacitance can still be maintained under high current density, the material has excellent rate performance, the capacitance retention rate reaches 99% after 10,000 cycles, and the cycle stability is enhanced.

[0036] The composite material prepared by the preparation method of the present invention can be applied to energy storage devices, and can greatly increase the life of the energy storage devices.

[0037] The present application is further described in detail below in conjunction with specific embodiments.

[0038] Example 1

[0039] This embodiment provides a preparation method of a CVD in-situ grown graphene carbon nanotube composite material: Step 1: Select nickel foam as the template and pre-treat it in the CVD system to ensure the cleanliness and activation effect of the substrate, so as to facilitate the growth of high-quality three-dimensional graphene. The specific operations are as follows: 1. Purge system: At room temperature, introduce 200 sccm nitrogen into the CVD reaction chamber for 15 min to remove residual gas and impurities in the chamber to ensure the stability of the reaction environment.

[0040] 2. Vacuum treatment: After the purge is completed, the CVD system is vacuumed to reduce the pressure in the chamber to 10 -3Torr to further remove moisture and impurities to prevent impurities from affecting the growth quality of graphene.

[0041] 3. Substrate activation: After the vacuum treatment is completed, the temperature is gradually raised to 800 °C, and hydrogen is introduced at a flow rate of 10 sccm to activate the foam nickel substrate for 5 minutes. The role of hydrogen is to remove the surface oxide layer, optimize the surface state of nickel, and improve the nucleation density and growth uniformity of graphene.

[0042] 4. Three-dimensional graphene growth: Subsequently, methane is introduced as a carbon source at a high temperature of 800 °C, and the CVD growth pressure is maintained at 1-100 Torr, and the growth time is 5 min to obtain a three-dimensional graphene structure with high porosity and high specific surface area. The methane flow rate is controlled at 10 sccm to regulate the carbon supply rate and avoid excessive deposition; the growth time is 5 min. In addition to methane, hydrogen / argon or hydrogen / nitrogen mixed gas can be introduced as needed, that is, in addition to the aforementioned carbon source and hydrogen, argon or nitrogen is introduced as a protective atmosphere, and the gas composition is adjusted so that the proportion of hydrogen in the hydrogen carrier gas is 1%, so as to optimize the growth environment and inhibit the formation of amorphous carbon, thereby improving the crystallization quality of graphene.

[0043] Substrate activation pretreatment: Nickel foam can be chemically cleaned before growth to remove the surface oxide layer and improve its catalytic activity and graphene nucleation density.

[0044] After the growth is completed, it needs to be cooled in an inert nitrogen environment to prevent the graphene layer structure from being affected by thermal stress and causing uncontrollable defects.

[0045] Step 2: High temperature oxidation etching is used to introduce defect structures on the graphene surface obtained in step 1 to increase the nucleation and growth sites of carbon nanotubes. The specific operation includes placing the prepared three-dimensional graphene material in an oxidizing atmosphere and heating it within a temperature range of 800 ° C. The oxidation time can be adjusted according to the required conditions, usually within 5 minutes. This process can effectively control the surface roughness and defect concentration of graphene, thereby optimizing the subsequent growth uniformity and bonding strength of carbon nanotubes.

[0046] Step 3: On the graphene surface obtained in the previous step, methane is decomposed by CVD method at a temperature of 750 ° C in a hydrogen atmosphere to grow carbon nanotubes. The gas flow rate is 10 sccm to regulate the growth rate and carbon source supply; the deposition time is 5 minutes to control the length and density of the carbon nanotubes. In addition, it is necessary to optimize the chamber pressure to 1 Torr, introduce argon as a protective atmosphere, and adjust the ratio of carbon source and argon gas flow to ensure a stable growth environment and inhibit non-uniform deposition. By adjusting the flow rate and growth time of the carbon source gas-methane gas, the density and diameter of CNTs can be precisely controlled. The larger the flow rate of carbon source gas II, the longer the growth time, the greater the density of CNTs, and the larger the diameter.

[0047] The graphene carbon nanotube composite material prepared in Example 1 can still maintain a high specific capacitance at high current density, and the material has excellent rate performance. After 10,000 cycles, the capacitance retention rate reaches 99%, and the cycle stability is enhanced.

[0048] Example 2

[0049] This embodiment provides a preparation method of a CVD in-situ grown graphene carbon nanotube composite material: Step 1: Select nickel foam as the template and pre-treat it in the CVD system to ensure the cleanliness and activation effect of the substrate, so as to facilitate the growth of high-quality three-dimensional graphene. The specific operations are as follows: 1. Purge system: At room temperature, introduce 200 sccm nitrogen into the CVD reaction chamber for 15 min to remove residual gas and impurities in the chamber to ensure the stability of the reaction environment.

[0050] 2. Vacuum treatment: After the purge is completed, the system is vacuumed to reduce the pressure in the chamber to 10 -3 Torr to further remove moisture and impurities to prevent impurities from affecting the growth quality of graphene.

[0051] 3. Substrate activation: After the vacuum treatment is completed, the temperature is gradually raised to 1200 °C, and hydrogen is introduced at a flow rate of 200 sccm to activate the foam nickel substrate for 60 minutes. The role of hydrogen is to remove the surface oxide layer, optimize the surface state of nickel, and improve the nucleation density and growth uniformity of graphene.

[0052] 4. Three-dimensional graphene growth: Subsequently, methane was introduced as a carbon source at a high temperature of 1200 °C, the methane flow rate was controlled at 10 sccm, and the CVD growth pressure was maintained at 1-100 Torr. The growth time was controlled at 60 min to obtain a three-dimensional graphene structure with high porosity and high specific surface area.

[0053] In addition to methane, a hydrogen-carrying argon mixed gas can be introduced as needed to optimize the growth environment and inhibit the formation of amorphous carbon, thereby improving the crystallization quality of graphene; hydrogen accounts for 25% of the hydrogen carrier gas.

[0054] Substrate activation pretreatment: Nickel foam can be chemically cleaned before growth to remove the surface oxide layer and improve its catalytic activity and graphene nucleation density.

[0055] After the growth is completed, it needs to be slowly cooled in a low-flow hydrogen environment to avoid the graphene layer structure being affected by thermal stress and causing uncontrollable defects.

[0056] Step 2: High temperature oxidation etching is used to introduce microporous structures on the surface of the graphene obtained in step 1 to increase the nucleation and growth sites of carbon nanotubes. The specific operation includes placing the three-dimensional graphene material prepared in step 1 in an oxidizing atmosphere of oxygen, and performing heat treatment at a temperature range of 1200 ° C for an oxidation time of 60 min. This process can effectively regulate the surface roughness and defect concentration of graphene, thereby optimizing the subsequent growth uniformity and bonding strength of carbon nanotubes.

[0057] Step 3: On the graphene surface obtained in the previous step, ethylene is decomposed by CVD at 900°C in a hydrogen / nitrogen atmosphere to grow carbon nanotubes. The ethylene gas flow rate and growth time are adjusted to precisely control the density and diameter of CNTs.

[0058] The graphene carbon nanotube composite material prepared in Example 2 can still maintain a high specific capacitance at high current density, and the material has excellent rate performance. After 10,000 cycles, the capacitance retention rate reaches 99%, and the cycle stability is enhanced.

[0059] Example 3

[0060] This embodiment provides a preparation method of a CVD in-situ grown graphene carbon nanotube composite material: Step 1: Select nickel foam as the template and pre-treat it in the CVD system to ensure the cleanliness and activation effect of the substrate, so as to facilitate the growth of high-quality three-dimensional graphene. The specific operations are as follows: 1. Purge system: At room temperature, introduce 200 sccm nitrogen into the CVD reaction chamber for 15 min to remove residual gas and impurities in the chamber to ensure the stability of the reaction environment.

[0061] 2. Vacuum treatment: After the purge is completed, the system is vacuumed to reduce the pressure in the chamber to 10 -3 Torr to further remove moisture and impurities to prevent impurities from affecting the growth quality of graphene.

[0062] 3. Substrate activation: After the vacuum treatment is completed, the temperature is gradually raised to 800 °C, and hydrogen is introduced at a flow rate of 10 sccm to activate the foam nickel substrate for 50 min. The role of hydrogen is to remove the surface oxide layer, optimize the surface state of nickel, and improve the nucleation density and growth uniformity of graphene.

[0063] 4. Three-dimensional graphene growth: Subsequently, methane was introduced as a carbon source at a high temperature of 950 °C, the methane flow rate was controlled at 100 sccm, and the CVD pressure was maintained at 10 Torr. The growth time was 30 min to obtain a three-dimensional graphene structure with high porosity and high specific surface area.

[0064] In addition to methane, hydrogen-carrying argon gas is introduced as needed to optimize the growth environment and inhibit the formation of amorphous carbon, thereby improving the crystallization quality of graphene; hydrogen accounts for 2% of the hydrogen carrier gas.

[0065] Substrate activation pretreatment: Nickel foam can be chemically cleaned before growth to remove the surface oxide layer and improve its catalytic activity and graphene nucleation density.

[0066] After the growth is completed, it needs to be cooled in an inert atmosphere to prevent the graphene layer structure from being affected by thermal stress and causing uncontrollable defects.

[0067] Step 2: High temperature oxidation etching is used to introduce defect structures on the graphene surface obtained in step 1 to increase the nucleation and growth sites of carbon nanotubes. The specific operation includes placing the prepared three-dimensional graphene material in an oxidizing atmosphere of O2 / N2 mixed gas, and performing heat treatment at a temperature range of 800°C, and the oxidation time is usually between 50 minutes. This process can effectively regulate the surface roughness and defect concentration of graphene, thereby optimizing the subsequent growth uniformity and bonding strength of carbon nanotubes.

[0068] Step 3: On the graphene surface obtained in the previous step, ethane is decomposed by CVD at a temperature of 750°C in a hydrogen carrier gas atmosphere to grow carbon nanotubes. The ethane gas flow rate and growth time are adjusted to accurately control the density and diameter of CNTs.

[0069] The graphene carbon nanotube composite material prepared in Example 3 can still maintain a high specific capacitance at high current density, and the material has excellent rate performance. After 10,000 cycles, the capacitance retention rate reaches 99%, and the cycle stability is enhanced.

[0070] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0071] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for preparing a CVD in-situ grown graphene carbon nanotube composite material, characterized in that: The steps include: Step 1: introducing carbon source gas I into a metal material template having a foam structure to grow three-dimensional graphene by chemical vapor deposition; Step 2, introducing defects on the surface of the graphene obtained in step 1; Step 3: introducing carbon source gas II to chemically vapor deposit and grow carbon nanotubes on the surface of the graphene obtained in step 2 to obtain a composite material.

2. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: The metal material template with a foam structure in step one is selected from at least one of nickel foam, iron foam, copper foam, cobalt foam, iron-nickel alloy foam, copper-iron alloy foam, iron-cobalt alloy foam, copper-nickel alloy foam, cobalt-nickel alloy foam, copper-cobalt alloy foam, iron-nickel-copper alloy foam, cobalt-nickel-copper alloy foam, cobalt-nickel-copper alloy foam, and iron-nickel-cobalt alloy foam.

3. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: The carbon source gas I in step 1 is low molecular weight hydrocarbons.

4. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: In step 1, the temperature of chemical vapor deposition is 800-1200°C, the flow rate of carbon source gas I is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

5. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: In step 1, before chemical vapor deposition, reducing gas is introduced to activate the metal material template with a foam structure. The reducing gas is a hydrogen-carrying nitrogen and / or hydrogen-carrying argon atmosphere, and the proportion of hydrogen in the reducing gas is 1-25%.

6. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 5, characterized in that: Step 1 also includes the steps of purging and vacuum treating the CVD system before activating the material template with the foam structure.

7. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: The second step of introducing defects is to form defect active sites on the surface of the graphene obtained in the first step by means of high temperature oxidation etching.

8. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 7, characterized in that: The operation of high temperature oxidation etching is as follows: placing the graphene material obtained in step 1 in air, oxygen or O2 / N2 mixed gas, cutting off the supply of hydrogen, introducing inert gas at the same time, and heating oxidation etching at 800-1200°C for 5-60 min.

9. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: The carbon source gas II in step three is low molecular weight hydrocarbons.

10. The method for preparing a CVD in-situ grown graphene carbon nanotube composite material according to claim 1, characterized in that: The temperature of the chemical vapor deposition in step three is 800-1200° C., the gas flow rate is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

11. A CVD in-situ grown graphene carbon nanotube composite material, characterized in that: The method is prepared according to any one of claims 1 to 10.

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