A graphene carbon nanotube composite material grown in situ by CVD and a preparation method thereof

Abstract

The application 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 one, introducing carbon source gas I into a metal material template with a foam structure, and performing chemical vapor deposition to grow three-dimensional graphene; step two, introducing defects on the surface of the graphene obtained in step one; step three, introducing carbon source gas II, performing chemical vapor deposition on the surface of the graphene obtained in step two to in-situ grow carbon nanotubes, and obtaining the composite material. The micro network structure of the obtained composite material is good in stability and is not easy to collapse; the growth consistency of the carbon nanotubes is good; the composite material can be prepared on a large scale and applied to energy storage devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial synthesis, in particular to a CVD in-situ grown graphene-carbon nanotube composite material and a preparation method thereof. BACKGROUND

[0002] Graphene-carbon nanotube composite materials have potential application prospects in energy storage devices. Currently, the preparation methods of graphene-carbon nanotube composite materials mainly include chemical vapor deposition (CVD) and solution assembly. Among them, the CVD method has become a research hotspot due to its strong controllability and high quality of the prepared composite materials. For example, the invention patent applications with publication numbers CN117736580A, CN103303901B, CN108461305A and CN113044830A all disclose the process of preparing graphene-carbon nanotube composite materials by CVD. In addition, Zhang et al. (Zhang Ning, Preparation and Capacitance Performance of Three-dimensional Graphene / Carbon Nanotube Composite Materials, Master's Thesis of Chongqing University) transferred the graphene film grown on the surface of a copper foil to a substrate on which a metal catalyst was deposited, and further prepared a graphene-carbon nanotube composite material by CVD growth.

[0003] However, the existing CVD method for preparing graphene-carbon nanotube composite materials still has many deficiencies, such as: 1. Insufficient conductive network construction: the existing method is difficult to grow CNTs uniformly on three-dimensional graphene, affecting the electron transmission efficiency. 2. Insufficient structural stability: the composite material prepared by the existing CVD method is prone to collapse during long-term use, leading to the decay 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, affecting the consistency of the composite material and limiting large-scale preparation and application.

[0004] Therefore, it is urgent to develop a new preparation method to overcome the above challenges. SUMMARY

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

[0006] To solve the above problems, the present application first provides a preparation method of CVD in-situ grown graphene-carbon nanotube composite material, comprising the following steps:

[0007] Step one, introducing carbon source gas I into a metal material template with a foam structure, and growing three-dimensional graphene by chemical vapor deposition;

[0008] Step two, introducing defects on the surface of the graphene obtained in step one;

[0009] Step three, introduce carbon source gas II, graphene surface chemical vapor deposition growth of carbon nanotubes, namely the composite material.

[0010] Compared with the prior art, the graphene-carbon nanotube composite material prepared by the application has the following significant advantages: the graphene presents a three-dimensional structure and is tightly combined with the carbon nanotube, so that the obtained composite material has high stability. The structure constructs a micro network of three-dimensional graphene + one-dimensional carbon nanotube, ensures good mechanical strength and electrical conductivity, and effectively prevents the collapse of the material. In addition, the growth consistency of the carbon nanotube is high, large-scale preparation can be realized, and the industrial application demand is met.

[0011] In a possible implementation, the metal material template with a foam structure in step one is selected from at least one of foam nickel, foam iron, foam copper, foam cobalt, 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-iron-copper alloy foam, iron-nickel-cobalt alloy foam.

[0012] In a possible implementation, the carbon source gas I for chemical vapor deposition in step one is a low-molecular hydrocarbon.

[0013] In a possible implementation, the temperature for chemical vapor deposition in step one is 800-1200 ℃, 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.

[0014] In the above scheme, a metal material substrate with a foam structure is selected as a template for CVD growth of graphene, and three-dimensional graphene can be grown by utilizing the multi-dimension and multi-contact surface of the foam. These metal materials with a foam structure can be a 3D printed structure, a metal mesh, or a nickel, iron, copper, or cobalt sacrificial template with a porous structure. The CVD process in step one involves multiple key parameters, including but not limited to: the growth temperature is controlled at 800-1200 ℃ to regulate the number of layers and the quality of graphene; the gas flow rate is generally 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 type of carrier gas (hydrogen, argon or helium) and its proportion need to be controlled to optimize the crystallinity and uniformity of graphene. The protective atmosphere can make the grown three-dimensional graphene product less contaminated, with high purity and good consistency. If there are other key process conditions that affect the quality of graphene growth or the performance of the composite material, the relevant parameters can be further optimized to improve the controllability and applicability of the material.

[0015] In a possible implementation, the foam material template is activated by introducing a reducing gas before chemical vapor deposition in step one, and the reducing gas is a hydrogen gas carrying nitrogen gas and / or a hydrogen gas carrying argon gas atmosphere, and the proportion of hydrogen gas in the reducing gas is 1-25%.

[0016] By the above technical solution, the hydrogen gas activated template has a higher surface cleanliness and a larger surface roughness, which is more suitable for growing three-dimensional graphene products. The hydrogen gas provides a reducing environment to promote the activation of the template and the high-quality growth of graphene, while the nitrogen gas or argon gas can be used to control the gas phase environment, reduce the carbon deposition rate, and optimize the structural uniformity of the material.

[0017] In a possible implementation, the CVD system is purged and vacuumed before the material template with a foam structure is activated in step one.

[0018] In a possible implementation, the introduction of defects in step two is to form defect active sites on the graphene surface obtained in step one by high-temperature oxidation etching.

[0019] In a possible implementation, the high-temperature oxidation etching operation is to place the graphene material obtained in step one in air, oxygen, or O2 / N2 mixed gas, cut off the supply of hydrogen gas, and introduce an inert gas, and heat and oxidize etch at 800-1200 ℃ for 5-60 min. The heat treatment in the temperature range of 800-1200 ℃ can remove surface organic matter or control the surface chemical properties and roughness, and form an oxidation layer that is conducive to the subsequent deposition of carbon source.

[0020] In a possible implementation, the carbon source gas II in step three is a low-molecular hydrocarbon.

[0021] In a possible implementation, the temperature of the chemical vapor deposition in step three is 800-1200 ℃, the gas flow is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

[0022] In the above technical solution, the low-molecular hydrocarbon is preferably a hydrocarbon gas suitable for CVD process, such as methane, acetylene, ethylene, propane, etc., to ensure the high-quality growth of carbon nanotubes. The growth temperature is 800-1200 ℃ to optimize the morphology and quality of the carbon nanotubes; the gas flow is 10-200 sccm to control the growth rate and carbon source supply; and the deposition time is 5-60 min to control the length and density of the carbon nanotubes. In addition, the cavity pressure (1-100 Torr), the type of carrier gas (such as argon, hydrogen, and helium), and their proportions need to be optimized to ensure a stable growth environment and inhibit non-uniform deposition.

[0023] The application also provides a graphene carbon nanotube composite material grown in-situ by CVD, which is prepared by the preparation method and applied to an energy storage device.

[0024] The application has the following advantages:

[0025] The application uses a metal material with a foam structure as a template matrix to prepare a composite material with three-dimensional graphene, and then catalytically grows one-dimensional carbon nanotubes on the three-dimensional graphene surface with defects, thereby obtaining a three-dimensional graphene-carbon nanotube composite material.

[0026] The CVD process of the application has a low temperature and simple steps, and reduces manufacturing difficulty and cost, and is suitable for large-scale preparation and application.

[0027] The composite material prepared by the application constructs an efficient three-dimensional and one-dimensional conductive network, improves the specific capacity, cycle stability and rate performance of the material, and has a wide application prospect in energy storage devices.

[0028] The three-dimensional graphene-CNTs composite material obtained by the application has a specific capacity of 35.2 F / g, which is significantly better than single graphene or CNTs material. The material still has a high specific capacity under a high current density, has excellent rate performance, and is suitable for high-power energy storage devices. The material has a capacity retention rate of 99% after 10,000 cycles, has enhanced cycle stability, and can greatly improve the service life of the energy storage device. The 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 transmission resistance. By optimizing the CVD growth parameters, the CNTs can be grown on the graphene matrix in a controllable manner, the consistency and repeatability of the material are ensured, the preparation cost is reduced, and the industrial application potential is improved. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The figure is a micro-morphology diagram of three-dimensional graphene of the application;

[0030] Figure 2 The figure is a micro-morphology diagram of carbon nanotubes of the application;

[0031] Figure 3 The figure is a micro-morphology diagram of three-dimensional graphene-carbon nanotube composite material of the application;

[0032] Figure 4 The figure is an XRD diagram of three-dimensional graphene-carbon nanotube composite material of the application;

[0033] Figure 5Raman spectrum of the three-dimensional graphene-carbon nanotube composite material of the present application;

[0034] Figure 6 Transmission electron microscope picture of the three-dimensional graphene-carbon nanotube composite material of the present application, wherein Gr represents graphene and CNT represents carbon nanotube;

[0035] Figure 7 Specific capacity performance test result of the three-dimensional graphene-carbon nanotube composite material of the present application;

[0036] Figure 8 Cycle stability test result of the three-dimensional graphene-carbon nanotube composite material of the present application. DETAILED DESCRIPTION

[0037] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application 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 application, and are not used to limit the parameter range described in the present application, and the reasonable changes derived therefrom are still within the protection scope of the claims of the present application.

[0038] It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and the values stated are approximations that are intended to be rounded to the nearest value that is consistent with the precision of the measurement. The endpoints of the ranges of values and the values stated are not to be construed as being limited to the precise values recited as endpoints or intermediate values. The application is thus meant to be construed in accordance with customary practice within the art.

[0039] Unless otherwise defined, all terms, symbols and other scientific terminology used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In some instances, terms are defined herein in accordance with a commonly used meaning in the art. Such definitions are not intended to limit the scope or applicability of the application. The techniques described or referenced herein are generally well known in the art and are practiced in accordance with conventional methods, unless otherwise indicated. Unless otherwise indicated, the use of commercially available kits and reagents, and the use of instruments are performed according to the protocols and parameters provided by the manufacturer.

[0040] The present application discloses a preparation method of a graphene-carbon nanotube composite material grown in situ by CVD, comprising the following steps:

[0041] Step one, using a metal material substrate with a foam structure as a template, the template is chemically cleaned 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 vacuum treatment, then introduce hydrogen carrier gas to activate the substrate, that is, gradually heat to 800-1200 ℃, and introduce hydrogen at a flow rate of 10-200 sccm, activate the foam substrate for 5-60 min; hydrogen carrier is hydrogen carrier nitrogen and / or hydrogen carrier argon atmosphere, the proportion of hydrogen in the reducing gas is 1-25%. Again, under high temperature of 800-1200 ℃, 1-100 Torr pressure, carbon source gas I is introduced, preferably 950-1050 ℃, to control the carbon supply rate to avoid excessive deposition, the deposition time is in the range of 5-60 min. Carbon source gas I is preferably low molecular hydrocarbons, more preferably at least one of methane, acetylene, ethylene, propane. Hydrogen / argon or hydrogen / nitrogen mixed gas can be introduced as needed, that is, in addition to the aforementioned introduction of carbon source and hydrogen, argon or nitrogen is introduced as a protective atmosphere to adjust the gas composition, optimize the growth environment and inhibit the formation of amorphous carbon, and improve the crystalline quality of graphene. The grown three-dimensional graphene is also cooled to room temperature under the protection of inert gas atmosphere.

[0042] Step two, introduce defects on the graphene surface 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 at a temperature of 800-1200 ℃, the oxidation time can be adjusted according to the required conditions, usually between 5-60 min. This process can effectively control the surface roughness and defect concentration of graphene, thereby optimizing the uniformity and bonding force of the subsequent carbon nanotube growth.

[0043] Step three, introduce carbon source gas II, chemical vapor deposition of carbon nanotubes on the graphene surface obtained in step two to obtain a composite material, the carbon source II gas flow is 10-200 sccm, the deposition temperature is 750-900 ℃, the deposition pressure is 1-100 Torr, and the deposition time is 5-60 min. During the deposition of carbon nanotubes, argon 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 precisely controlled, the greater the flow rate of carbon source gas II and the longer the growth time, the greater the density of CNTs and the larger the diameter. Carbon source gas II is preferably low molecular hydrocarbons, more preferably at least one of methane, acetylene, ethylene, propane.

[0044] XRD (X-ray diffraction) is used to determine the phase composition of the composite material.

[0045] SEM / TEM (scanning electron microscope / transmission electron microscope) is used to analyze the microstructure of the composite material and the distribution of CNTs.

[0046] Raman (Raman spectroscopy) is used to determine the defect density of graphene and the carbon structure of CNTs.

[0047] 1M H2SO4 or 1M Na2SO4 electrolyte is used for long-term cycle test to evaluate the capacitance decay.

[0048] The characterization results and test results of the obtained composite material are shown in Figures 1-8 The micro-morphology images of Figures 1-3 , Figure 6 can be seen that the composite material is composed of graphene and carbon nanotubes, the carbon nanotubes are distributed on the surface of three-dimensional graphene, the micro three-dimensional + one-dimensional conductive network of the composite material is successfully constructed, and the stability and consistency are good, and the results of Figures 4-5 also prove that the composite material is composed of graphene and carbon nanotubes, and the test results of Figure 7 show that the specific capacity of the composite material reaches 35.2 F / g, which is significantly better than single graphene or CNTs material. Figure 8 The cycle stability test results of

[0049] The composite material prepared by the preparation method of the application can be applied in energy storage devices, and can greatly improve the service life of the energy storage devices.

[0050] The application will be further described in detail below in combination with specific examples.

[0051] Example 1

[0052] This embodiment provides a preparation of a graphene carbon nanotube composite material grown in situ by CVD:

[0053] Step one, select foam nickel as a template, and perform pretreatment in a 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 operation is as follows:

[0054] 1. Purge the system: at room temperature, introduce 200 sccm of nitrogen into the CVD reaction cavity, and perform purging treatment for 15 min to remove residual gas and impurities in the cavity, and ensure the stability of the reaction environment.

[0055] 2. Vacuum treatment: After purging, the CVD system is vacuumed to reduce the pressure in the chamber to 10 Torr to further remove moisture and impurities, preventing impurities from affecting the quality of graphene growth. -3 Torr to further remove moisture and impurities, preventing impurities from affecting the quality of graphene growth.

[0056] 3. Substrate activation: After vacuum treatment, gradually heat to 800 ℃ and introduce hydrogen gas at a flow rate of 10 sccm to activate the nickel foam substrate for 5 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.

[0057] 4. Three-dimensional graphene growth: Subsequently, introduce methane as a carbon source at a high temperature of 800 ℃ and maintain the CVD growth pressure control at 1-100 Torr for 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 / hydrogen or hydrogen / nitrogen mixed gas can be introduced as needed, i.e., in addition to the aforementioned introduction of carbon source and hydrogen, argon or nitrogen is introduced as a protective atmosphere, adjusting the gas composition so that the hydrogen content in the hydrogen carrier gas is 1%, to optimize the growth environment and inhibit the formation of amorphous carbon, improving the crystalline quality of graphene.

[0058] Substrate activation pretreatment: The nickel foam can be chemically cleaned before growth to remove the surface oxide layer, improve its catalytic activity and graphene nucleation density.

[0059] After growth, cooling is required in an inert nitrogen atmosphere to avoid uncontrollable defects in the graphene layer structure due to thermal stress.

[0060] Step two: Introduce defect structures on the surface of the graphene obtained in step one by high-temperature oxidation etching 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 air and heating at a temperature of 800 ℃. The oxidation time can be adjusted according to the required conditions, usually between 5 min. This process can effectively control the surface roughness and defect concentration of graphene, thereby optimizing the growth uniformity and bonding force of subsequent carbon nanotubes.

[0061] Step three, grow carbon nanotubes on the graphene surface obtained in the foregoing steps by CVD method at a temperature of 750 DEG C in a hydrogen atmosphere. The gas flow is 10 sccm to regulate the growth rate and carbon source supply; the deposition time is 5 min to control the length and density of carbon nanotubes. In addition, the cavity pressure needs to be optimized to 1 Torr, argon 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 of carbon source gas, i.e., methane gas, and the growth time, the density and diameter of CNTs are accurately controlled. The greater the flow rate of carbon source gas II and the longer the growth time, the greater the density and diameter of CNTs.

[0062] The graphene carbon nanotube composite material prepared in Example 1 can still maintain a high specific capacitance under a high current density, has excellent rate performance, and has a capacitance retention rate of 99% after 10000 cycles, and enhanced cycle stability.

[0063] Example 2

[0064] This example provides a preparation of a graphene carbon nanotube composite material grown in situ by CVD:

[0065] Step one, select foamed nickel as a template and perform pretreatment in a 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 operation is as follows:

[0066] 1. Purge the system: at room temperature, introduce 200 sccm of nitrogen into the CVD reaction cavity and perform purging treatment for 15 min to remove residual gas and impurities in the cavity and ensure the stability of the reaction environment.

[0067] 2. Vacuum treatment: after purging, perform vacuum treatment on the system to reduce the pressure in the cavity to 10 -3 Torr to further remove moisture and impurities and prevent impurities from affecting the growth quality of graphene.

[0068] 3. Substrate activation: after vacuum treatment is completed, gradually heat to 1200 DEG C and introduce hydrogen at a flow rate of 200 sccm to activate the foamed nickel substrate for 60 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.

[0069] 4. Three-dimensional graphene growth: subsequently, introduce methane as a carbon source at a high temperature of 1200 DEG C, control the methane flow rate at 10 sccm, maintain the CVD growth pressure at 1-100 Torr, and control the growth time at 60 min to obtain a three-dimensional graphene structure with high porosity and high specific surface area.

[0070] In addition to methane, hydrogen gas can be introduced as needed to optimize the growth environment and inhibit the formation of amorphous carbon, improving the crystalline quality of graphene; the hydrogen content in the hydrogen carrier gas is 25%.

[0071] Substrate activation pretreatment: The foam nickel can be chemically cleaned before growth to remove the surface oxide layer and improve its catalytic activity and graphene nucleation density.

[0072] After the growth is completed, slow cooling in a low-flow hydrogen environment is required to avoid uncontrollable defects caused by thermal stress on the graphene layer structure.

[0073] Step two, introduce microporous structure on the surface of graphene obtained in step one by high-temperature oxidation etching to increase the nucleation and growth sites of carbon nanotubes. The specific operation includes placing the three-dimensional graphene material prepared in step one in an oxidizing atmosphere of oxygen and heat treating at a temperature of 1200 ℃ for an oxidation time of 60 min. This process can effectively control the surface roughness and defect density of graphene, thereby optimizing the growth uniformity and bonding force of subsequent carbon nanotubes.

[0074] Step three, grow carbon nanotubes by CVD method on the graphene surface obtained in the preceding steps at a temperature of 900 ℃ in a hydrogen / nitrogen atmosphere by decomposing ethylene. Adjust the ethylene gas flow and growth time to precisely control the density and diameter of CNTs.

[0075] The graphene carbon nanotube composite material prepared in Example 2 can still maintain a high specific capacitance under high current density, and the material has excellent rate performance, with a capacitance retention rate of 99% after 10000 cycles, and enhanced cycle stability.

[0076] Example 3

[0077] This example provides a preparation of a CVD in-situ grown graphene carbon nanotube composite material:

[0078] Step one, select foam nickel as the template and perform pretreatment in the CVD system to ensure the cleanliness and activation effect of the substrate, thereby facilitating the growth of high-quality three-dimensional graphene. The specific operation is as follows:

[0079] 1. Purge the system: at room temperature, introduce 200 sccm of nitrogen into the CVD reaction chamber and perform purge treatment for 15 min to remove residual gases and impurities in the chamber and ensure the stability of the reaction environment.

[0080] 2. Vacuum treatment: after the purge is completed, perform vacuum treatment on the system to reduce the pressure in the chamber to 10 -3 Torr to further remove moisture and impurities and prevent impurities from affecting the growth quality of graphene.

[0081] 3. Substrate activation: After the vacuum treatment is completed, gradually increase the temperature to 800 ℃, and introduce hydrogen gas at a flow rate of 10 sccm to activate the foamed 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.

[0082] 4. Three-dimensional graphene growth: Subsequently, introduce methane as a carbon source at a high temperature of 950 ℃, control the methane flow rate at 100 sccm, and maintain the CVD pressure control at 10 Torr, with a growth time of 30 min to obtain a three-dimensional graphene structure with high porosity and high specific surface area.

[0083] In addition to methane, hydrogen gas is introduced as needed to optimize the growth environment and inhibit the formation of amorphous carbon, improving the crystalline quality of graphene; the hydrogen content in the hydrogen carrier gas is 2%.

[0084] Substrate activation pretreatment: The foamed nickel can be chemically cleaned before growth to remove the surface oxide layer and improve its catalytic activity and graphene nucleation density.

[0085] After the growth is completed, cooling is required in an inert atmosphere environment to avoid the graphene layer structure from being affected by thermal stress and generating uncontrollable defects.

[0086] Step two: Defect structure is introduced on the surface of the graphene obtained in step one by high-temperature oxidation etching treatment 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 ℃, with an oxidation time usually between 50 min. This process can effectively control the surface roughness and defect concentration of graphene, thereby optimizing the growth uniformity and bonding force of subsequent carbon nanotubes.

[0087] Step three: Carbon nanotubes are grown on the graphene surface obtained in the preceding steps by CVD method at a temperature of 750 ℃ in a hydrogen carrier gas atmosphere by decomposing ethane. Adjust the ethane gas flow rate and growth time to precisely control the density and diameter of CNTs.

[0088] The graphene-carbon nanotube composite material prepared in Example 3 can still maintain a high specific capacitance under high current density, and the material has excellent rate performance, with a capacitance retention rate of 99% after 10000 cycles, and enhanced cycle stability.

[0089] In the description of the application, the description of the terms "one embodiment", "some embodiments", "in this embodiment", "specific example", or "some examples" and the like means that the specific features, mechanisms, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0090] The above description is merely a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to 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, It comprises the following steps: Step one, introducing carbon source gas I into the metal material template with foam structure, and growing three-dimensional graphene by chemical vapor deposition; Step two, introducing defects on the surface of graphene obtained in step one; Step three, introducing carbon source gas II, and growing carbon nanotubes on the surface of graphene obtained in step two by chemical vapor deposition to obtain the composite material; In step two, the graphene material obtained in step one is placed in air, oxygen or O2 / N2 mixed gas, and the supply of hydrogen is cut off, while inert gas is introduced, and the oxidation etching is heated at 800-1200 ℃ for 5-60 min.

2. The method according to claim 1, wherein the CVD graphene-carbon nanotube composite material is prepared in situ. The metal material template with foam structure in step one is selected from at least one of foam nickel, foam iron, foam copper, foam cobalt, 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-iron-copper alloy foam, iron-nickel-cobalt alloy foam.

3. The method according to claim 1, wherein the method is characterized by, The carbon source gas I in step one is a low molecular hydrocarbon.

4. The method according to claim 1, wherein the method is characterized by, The temperature of chemical vapor deposition in step one is 800-1200 ℃, 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 of claim 1, wherein the graphene-carbon nanotube composite material is prepared in-situ by CVD. In step one, a reducing gas is introduced to activate the metal material template with foam structure before chemical vapor deposition, the reducing gas is hydrogen carrying nitrogen and / or hydrogen carrying argon atmosphere, and the proportion of hydrogen in the reducing gas is 1-25%.

6. The method of claim 5, wherein the graphene-carbon nanotube composite material is prepared in-situ by CVD. Before activating the material template with foam structure in step one, the CVD system also includes the steps of purging and vacuum treatment.

7. The method according to claim 1, wherein the CVD graphene-carbon nanotube composite material is prepared in situ. The carbon source gas II in step three is a low molecular hydrocarbon.

8. The method of claim 1, wherein the graphene-carbon nanotube composite material is prepared in-situ by CVD. The temperature of chemical vapor deposition in step three is 800-1200 ℃, the gas flow rate is 10-200 sccm, the time is 5-60 min, and the pressure is 1-100 Torr.

9. A CVD in-situ grown graphene carbon nanotube composite material, characterized in that, Prepared by the preparation method of any one of claims 1-8.

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