CN114068927A

CN114068927A - Graphene carbon nanotube composite material and preparation method thereof

Info

Publication number: CN114068927A
Application number: CN202010771678.5A
Authority: CN
Inventors: 张锦; 孙丹萍; 林德武
Original assignee: Peking University
Current assignee: Peking University
Priority date: 2020-08-04
Filing date: 2020-08-04
Publication date: 2022-02-18
Anticipated expiration: 2040-08-04
Also published as: CN114068927B

Abstract

The invention provides a graphene carbon nanotube composite material and a preparation method thereof, wherein the preparation method comprises the following steps: granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, introducing a metal precursor, and cracking the metal precursor to form metal nanoparticles on the surface of the carrier to obtain microspheres; and adjusting the temperature of the reaction chamber to a second temperature, introducing a carbon source, and carrying out chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube so as to obtain the graphene carbon nanotube composite material. The composite material has a sea urchin-like structure, can be well dispersed in a solvent and a polymer, better exerts the synergistic effect of graphene and a carbon nano tube, has excellent comprehensive performance, and has good application prospects in the fields of electrochemical energy storage, biomedicine, composite reinforcement and the like.

Description

Graphene carbon nanotube composite material and preparation method thereof

Technical Field

The invention relates to the technical field of carbon material preparation, in particular to a graphene carbon nanotube composite material and a preparation method thereof.

Background

Ideal Carbon Nanotubes (CNTs) and Graphene (Gr), the basic structural units of which are all represented by sp²The hybrid carbon atoms form a honeycomb six-membered ring structure, and the honeycomb six-membered ring structure has excellent performances in the aspects of electric conduction, heat conduction, mechanical enhancement and the like. Meanwhile, the carbon nanotube and the graphene are greatly different on the microscopic scale, the carbon nanotube is a one-dimensional quantum material with an ultrahigh length-diameter ratio, and the graphene is a two-dimensional planar nano material with an ultrahigh diameter-thickness ratio, so that the carbon nanotube and the graphene have obvious difference in performance of electric conduction, heat conduction and mechanical enhancement.

Because the two materials have similarity in various properties and have intense competition, based on the property difference of the two materials, the graphene and the carbon nano tube are compounded to exert a synergistic effect, and the method becomes an effective idea for solving the defect of a single material. For example, as a conductive additive of a lithium ion battery, no matter graphene or carbon nanotube production enterprises, graphene-carbon nanotube composite conductive slurry is developed, and by constructing a multi-dimensional conductive network, internal resistance is reduced, and cycle performance and charge-discharge rate are improved. In the field of polymer composition, the combination of the carbon nanotube and graphene oxide which is a graphene derivative material is common, the binding force of a carbon material and a polymer matrix is improved by modifying functional groups on the surface of the graphene oxide, and meanwhile, the dispersion of the carbon nanotube is improved, so that the ground strength, the electricity and the thermal property of the carbon nanotube are better exerted. Therefore, the graphene and the carbon nano tube are widely concerned in the fields of preparation of the nano carbon material and application of electrochemical energy storage, biomedicine, composite enhancement and the like by compounding and exerting a synergistic effect.

The graphene and carbon nanotube composites can be classified into two categories according to the composite mode: one type is non-covalent action, such as physical mixing, and graphene and carbon nanotubes are mainly combined together through conjugation and are fixed in a cross way to form a disordered and intricate interpenetrating network; the other is covalent interaction, that is, graphene and carbon nanotubes have atoms in common, such as chemical vapor deposition in situ synthesis.

Physical mixing is generally carried out in a liquid phase, respective agglomeration structures of graphene and carbon nanotubes are opened through a strong mechanical action, not only is the process energy consumed, but also the raw material cost and the environmental cost are directly increased by a large amount of solvents, and the performance of the product is also reduced while the purity of the product is influenced by the addition of the surfactant (CN 110808375A). In addition, the original structure of the graphene or the carbon nanotube is inevitably damaged by the simple and extensive treatment process, the sheet diameter is reduced, the tube length is shortened, and the like.

Chemical vapor deposition direct synthesis can effectively avoid or weaken the above problems through a bottom-up assembly mode, but the control of the two structures and the precise control of the composite proportion are always the technical problems which need to be overcome by the method (such as Chinese patent applications CN110228805A, CN108069420A, CN106629672A and CN 110371956A).

Therefore, a new graphene carbon nanotube composite material and a preparation method thereof are needed to solve various problems in the prior art.

It is noted that the information disclosed in the foregoing background section is only for enhancement of background understanding of the invention and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.

Disclosure of Invention

The present invention is directed to overcome at least one of the above-mentioned drawbacks of the prior art, and provides a graphene carbon nanotube composite material and a method for preparing the same, so as to solve the problems of complex preparation process, high cost and low product quality of the graphene carbon nanotube composite material.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a preparation method of a graphene carbon nanotube composite material, which comprises the following steps: granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, introducing a metal precursor, and cracking the metal precursor to form metal nanoparticles on the surface of the carrier to obtain microspheres; and adjusting the temperature of the reaction chamber to a second temperature, introducing a carbon source, and carrying out chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube so as to obtain the graphene carbon nanotube composite material.

According to one embodiment of the invention, the graphene oxide dispersion liquid is a graphene oxide dispersion liquid with conductive particle intercalation, the conductive particles account for 1% -30% of the total mass of the graphene oxide and the conductive particles, and the conductive particles are selected from one or more of carbon black, ketjen black, onion carbon and fullerene.

According to one embodiment of the invention, the first temperature is between 100 ℃ and 700 ℃ and the second temperature is between 600 ℃ and 700 ℃.

According to one embodiment of the invention, the metal precursor is selected from one or more of metal carbonyl compounds, metallocene compounds selected from one or more of iron pentacarbonyl, di-iron nonacarbonyl, tri-iron dodecacarbonyl, nickel tetracarbonyl, chromium hexacarbonyl, dicobalt octacarbonyl and ferrocene.

According to one embodiment of the invention, after the carrier is placed in the reaction chamber, an inert carrier gas is introduced to suspend the carrier in the reaction chamber; wherein the inert carrier gas is one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300-1000 sccm.

According to one embodiment of the present invention, the carbon source is selected from one or more of hydrocarbons, alcohols, ethers, ketones, phenols and carbon monoxide; the time for introducing the carbon source is 1-60 min.

The invention also provides a graphene carbon nanotube composite material which has a sea urchin-like structure and comprises graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by aggregating carbon sheets formed by multi-layer reduced graphene oxide.

According to one embodiment of the invention, the graphene microspheres have nanopores inside, the particle size of the graphene microspheres is 0.1-100 μm, and the carbon sheet comprises 1-10 layers of reduced graphene oxide.

According to one embodiment of the present invention, the reduced graphene oxide is a reduced graphene oxide intercalated with conductive particles.

According to one embodiment of the present invention, the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube, the diameter of the carbon nanotube is 0.1nm to 15nm, and the length of the carbon nanotube is 10nm to 30 μm.

According to the technical scheme, the invention has the beneficial effects that:

the invention provides a graphene carbon nanotube composite material and a preparation method thereof, and the graphene carbon nanotube composite material with a sea urchin-like structure is obtained by constructing graphene microspheres as a growth template of carbon nanotubes, wherein the graphene microspheres are used as the growth fulcrum of the carbon nanotubes, so that the carbon nanotubes can be prevented from being tangled, and a stable mechanical support effect can be provided. The composite material can be well dispersed in a solvent and a polymer without adding a surfactant, so that carbon staggered structures with different dimensions, long range and short range are formed, and the synergistic effect of the carbon staggered structures and the long range and the short range is better exerted. The graphene carbon nanotube composite material prepared by the method has excellent comprehensive performance and has good application prospects in the fields of electrochemical energy storage, biomedicine, composite reinforcement and the like.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a flow chart of a process for preparing a graphene carbon nanotube composite according to an embodiment of the present invention;

FIG. 2 is a schematic view of a fluidized bed chemical vapor deposition apparatus for preparing a graphene carbon nanotube composite;

FIG. 3 is a scanning electron micrograph of the graphene carbon nanotube composite of example 1;

FIGS. 4a and 4b are transmission electron micrographs of the grapheme carbon nanotube composite of example 1, respectively;

FIG. 5 is a transmission electron micrograph of catalyst nanoparticles formed according to example 1;

FIG. 6 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 1;

FIG. 7 is a transmission electron micrograph of catalyst nanoparticles formed according to example 2;

FIG. 8 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 2;

FIG. 9 is a transmission electron micrograph of catalyst nanoparticles formed according to example 3;

FIG. 10 is a statistical distribution plot of the particle size of the catalyst nanoparticles formed in example 3;

FIG. 11 is a TEM image of the grapheme carbon nanotube composite of example 3;

FIG. 12 is a TEM image of the grapheme carbon nanotube composite of example 4;

FIG. 13 is a high-resolution transmission electron micrograph of a thin layer region on a carbon support microsphere of preparation example 1;

FIG. 14 is a high resolution TEM image of the upper thin layer region of the annealed microsphere after simulating the growth conditions of carbon nanotubes of example 6;

FIG. 15 is an X-ray photoelectron spectrum of the carbon support microsphere of preparation example 1;

FIG. 16 is an X-ray photoelectron spectrum of the annealed microspheres from the simulated carbon nanotube growth conditions of example 6.

Wherein the reference numbers are as follows:

100: quartz tube

200: bubbling tank

300: porous sieve plate

400: carrier

Detailed Description

The following presents various embodiments or examples in order to enable those skilled in the art to practice the invention with reference to the description herein. These are, of course, merely examples and are not intended to limit the invention. The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to yield one or more new ranges of values, which ranges of values should be considered as specifically disclosed herein.

Fig. 1 shows a flow chart of a process for preparing a graphene carbon nanotube composite material according to an embodiment of the present invention, and as shown in fig. 1, a method for preparing a graphene carbon nanotube composite material according to the present invention includes: granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier; the carrier is arranged in the reaction chamber; adjusting the temperature of the reaction chamber to a first temperature, introducing a metal precursor, and cracking the metal precursor to form metal nanoparticles on the surface of the carrier to obtain microspheres; and adjusting the temperature of the reaction chamber to a second temperature, introducing a carbon source, and carrying out chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube so as to obtain the graphene carbon nanotube composite material.

According to the invention, the composition of the carbon nano tube and the graphene can exert synergistic effect, and the defect of a single material is overcome. However, the existing composite mode has the problems of complex preparation process, high cost, difficult control of product quality and the like, so that the application of the composite mode has great limitation. The inventor of the invention finds that a graphene carbon nanotube composite material with a special assembly structure can be prepared by constructing graphene microspheres as a growth template of carbon nanotubes, and the composite material can be well dispersed in a solvent and a polymer without adding a surfactant to form a carbon staggered structure with different dimensions, long range and short range, so that the synergistic effect of the two can be better exerted.

Specifically, for the preparation of carbon nanotubes, the particle size of the catalyst is a key factor for controlling the diameter of the carbon nanotubes, and the particle size and distribution of the catalyst are determined by the quality of the catalyst carrier. Therefore, the graphene carbon nanotube composite material with the sea urchin-like structure can be obtained by firstly constructing a proper catalyst carbon carrier, namely a spherical material formed by aggregating carbon sheets formed by multiple layers of graphene oxide, depositing catalyst metal nanoparticles on the surface of the spherical carrier by adopting a specific process to ensure that the obtained catalyst has proper particle size and distribution, and then growing carbon nanotubes by chemical vapor deposition on the basis. The preparation method disclosed by the invention can control the structure of the obtained carbon nano tube according to actual needs by adjusting the technological parameters in the growth process, and meanwhile, the reduced graphene oxide microspheres with surface defects are also generated by reducing graphene oxide in the growth process of the carbon nano tube, so that the overall conductivity of the composite material can be ensured, and the dispersion of the catalyst metal nano particles is facilitated. In a word, the graphene carbon nanotube composite material with excellent comprehensive performance can be prepared by the method, and has good application prospects in the fields of electrochemical energy storage, biomedicine, composite reinforcement and the like.

The following describes the preparation process of the graphene carbon nanotube composite material of the present invention with reference to fig. 1.

Firstly, providing a graphene oxide dispersion liquid, and granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier.

The graphene oxide can be graphene oxide powder or a filter cake, or a graphene oxide pre-dispersion liquid which is pre-dispersed to a certain extent. Dispersing the graphene oxide in a solvent such as water, an aromatic solvent, or a solvent having not more than 3 carbon atoms (n)_C3) or less, for example, ethanol, propanol, etc. The concentration of the graphene oxide dispersion is 0.05mg/mL to 40mg/mL, for example, 0.05mg/mL, 0.1mg/mL, 1mg/mL, 10mg/mL, 15mg/mL, 20mg/mL, 30mg/mL, or the like. In order to disperse the graphene oxide better, a proper amount of surfactant, including but not limited to one or more of sodium dodecyl benzene sulfonate, polyvinylpyrrolidone, sodium lignosulfonate, polyvinyl alcohol, polydimethylsiloxane, gamma- (2, 3-epoxypropoxy) propyl trimethoxysilane (KH-560) and gamma-aminopropyltriethoxysilane (KH-550), can be added into the solvent.

In some embodiments, the graphene oxide dispersion of the present invention may also be a graphene oxide dispersion of conductive particle intercalation. The intercalation technology of the conductive particles enables the dispersion liquid to still maintain a higher specific surface after the solvent is removed, and the collapse and damage of the structure caused by agglomeration are avoided. On the basis, the solvent is continuously granulated and removed, so that the dried material forms a sphere-like structure with folds macroscopically while microcosmically not agglomerating, the active surface capable of being loaded by the catalyst is further exposed and fixed, and the efficiency and the quality of the catalyst loading are favorably improved.

Specifically, the preparation method of the conductive particle intercalated graphene oxide dispersion liquid comprises the following steps: and adding the conductive particle dispersion liquid into the graphene oxide dispersion liquid, and then fully mixing to obtain the graphene oxide dispersion liquid with the conductive particle intercalation.

The conductive particles are selected from one or more of carbon black, ketjen black, onion carbon and fullerene. The conductive particle dispersion liquid can be obtained by mixing and dispersing the conductive particle dispersion liquid with a soluble solvent according to a certain proportion. Wherein the solvent can be water, aromatic solvent, and carbon number not more than 3 (n)_C3) or less, for example, ethanol, propanol, etc. The conductive particles account for 1% to 30% of the total mass of the graphene oxide and the conductive particles, for example, 1%, 5%, 10%, 15%, 20%, 30%, and the like. Similarly, a suitable amount of a surfactant, including but not limited to one or more of sodium dodecylbenzene sulfonate, polyvinylpyrrolidone, sodium lignosulfonate, polyvinyl alcohol, polydimethylsiloxane, gamma- (2, 3-glycidoxy) propyltrimethoxysilane (KH-560), and gamma-aminopropyltriethoxysilane (KH-550), may also be added to the conductive particle dispersion.

In some embodiments, the dispersion of the graphene oxide and the dispersion of the conductive particles may be performed by a dispersion apparatus such as an ultrasonic dispersion apparatus, a high-speed dispersion tray, or an emulsifying machine. Further, the manner of fully mixing the graphene oxide dispersion liquid and the conductive particle dispersion liquid includes using a homogenizing treatment and/or a grinding treatment, and the mixing device may be a homogenizer, a centrifugal mill, or a combination thereof, but the present invention is not limited thereto. In the homogenizing treatment, the pressure of the homogenizing treatment is generally 1000bar to 1200bar, for example, 1000bar, 1100bar, 1150bar, 1180bar, 1200bar, etc., the flow rate is 0.1mL/s to 5mL/s, for example, 0.1mL/s, 0.8mL/s, 1mL/s, 2mL/s, 2.5mL/s, 3mL/s, etc., and the treatment time is 20min to 60min, for example, 20min, 30min, 50min, 55min, 60min, etc. And mixing to obtain a graphene oxide dispersion liquid of the conductive particle intercalation, and further granulating to remove the solvent to obtain the carrier.

Preferably, the desolventizing is carried out by a spray drying technique, which ensures that the material does not agglomerate microscopically, and simultaneously enables the material to take on a macroscopically wrinkled spheroidal or spherical structure, further exposing and fixing the active surface on which the catalyst can be supported. In some embodiments, the foregoing spray drying is conducted at a pressure of 0.1MPa to 0.5MPa, e.g., 0.1MPa, 0.3MPa, 0.4MPa, 0.5MPa, etc., at a flow rate of 800mL/h to 1500mL/h, e.g., 800mL/h, 900mL/h, 1000mL/h, 1200mL/h, 1500mL/h, etc., and at a temperature of 120 ℃ to 200 ℃, e.g., 120 ℃, 130 ℃, 150 ℃, 180 ℃, etc. Due to the low drying temperature, most of oxygen-containing groups of the material are reserved, a large number of active sites are provided for capturing the catalyst, and the efficiency and the quality of the catalyst loading are further improved.

Next, the carrier obtained as described above is placed in a reaction chamber, i.e., a tube furnace in a chemical vapor deposition apparatus. Generally, in order to stably suspend the carrier material in the reaction chamber, an inert carrier gas is required to be introduced; the inert carrier gas is selected from one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300sccm to 1000sccm, such as 300sccm, 350sccm, 400sccm, 500sccm, 600sccm, 780sccm, 900sccm, and the like.

And further, adjusting the temperature of the reaction chamber to a first temperature, introducing a metal precursor, and cracking the metal precursor to form metal nano particles on the surface of the carrier to obtain the microspheres.

Wherein the first temperature is 100 ℃ to 700 ℃, for example, 100 ℃, 200 ℃, 250 ℃, 300 ℃, 400 ℃, 450 ℃, 470 ℃, 500 ℃, 560 ℃ and the like, and the cracking temperature of the metal precursor affects the particle size of the obtained metal nanoparticles. Wherein, the higher the cracking temperature is, the larger the particle size is, the larger the tube diameter of the carbon nano tube obtained by catalysis is. Therefore, the tube diameter of the carbon nano tube can be regulated by regulating the cracking temperature of the metal precursor, and the proper required tube diameter size can be obtained.

In some embodiments, the aforementioned metal precursor may be one or more of a metal carbonyl compound, a metallocene compound selected from one or more of iron pentacarbonyl, iron nonacarbonyl, iron dodecacarbonyl, nickel tetracarbonyl, chromium hexacarbonyl, cobalt octacarbonyl, and ferrocene. The metal catalyst precursor may be a gaseous compound, a liquid compound or a solid compound, wherein, when the metal catalyst precursor is a liquid compound, the metal catalyst precursor may be introduced into the reaction chamber by bubbling or volatilizing an inert gas. When the precursor of the metal catalyst is a solid compound, the precursor can be directly put into a reaction chamber or be volatilized and then introduced into the reaction chamber. The formed metal nano-particles are formed by the corresponding metal after the precursor of the metal catalyst is cracked.

And finally, adjusting the temperature of the reaction chamber to a second temperature, introducing a carbon source, and carrying out chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube, thereby obtaining the graphene carbon nanotube composite material.

Wherein the second temperature is 600 ℃ to 700 ℃, for example, 600 ℃, 620 ℃, 650 ℃, 680 ℃, 690 ℃, etc. The carbon source may be one or more of a hydrocarbon, an alcohol, an ether, a ketone, a phenol, and carbon monoxide. The carbon source may be a gaseous carbon source, a liquid carbon source, or a solid carbon source. When the carbon source is a liquid carbon source, introducing the carbon source into the reaction chamber after bubbling or volatilizing by inert gas; when the carbon source is a solid carbon source, the carbon source can be directly placed into the reaction chamber or be volatilized and then introduced into the reaction chamber.

In some embodiments, the carbon source is introduced for a period of time ranging from 1min to 60min, such as 1min, 10min, 15min, 20min, 23min, 30min, 35min, 40min, 42min, 50min, and the like. The longer the carbon source is introduced, i.e., the longer the chemical vapor deposition reaction is, the multiwall carbon nanotube with longer tube diameter is generally obtained, whereas the single-wall carbon nanotube with shorter tube diameter is obtained by the shorter the carbon source is introduced. Therefore, the length and the shape of the carbon nanotube can be controlled by controlling the introduction time of the carbon source.

In the chemical vapor deposition reaction process, due to the high-temperature reduction reaction condition, the graphene oxide in the microspheres can be converted into reduced graphene oxide with excellent conductivity, and meanwhile, the integrity of the spherical structure is kept. In addition, the reduced graphene oxide has defects on the surface relative to the pure graphene, and the defects are more beneficial to the dispersion of the catalyst nanoparticles on the surface, so that the overall catalytic effect is improved.

The invention also provides a graphene carbon nanotube composite material obtained by the method, which has a sea urchin-like structure and comprises graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by aggregating multi-layer thin and flexible carbon sheets, the carbon sheets are formed by reducing and oxidizing 1-10 layers of few layers of graphene, and the inside of the graphene microspheres are provided with nano-pores with the particle size of 0.1-100 μm, such as 0.1 μm, 1 μm, 10 μm, 50 μm, 70 μm, 90 μm, 100 μm and the like.

In some embodiments, the reduced graphene oxide is a reduced graphene oxide intercalated with conductive particles, that is, the carbon sheets are composed of fewer layers of the reduced graphene oxide intercalated with conductive particles, each carbon sheet approximately comprises 1-10 layers of the reduced graphene oxide, wherein the higher the oxidation degree is, the thinner the number of layers of the graphene oxide is, and oxygen-containing groups on the surface provide more active sites to adsorb the conductive particles, so that stacking of the reduced graphene oxide sheet layers in the reduction process is inhibited, and on the other hand, more load sites can be provided for the catalyst, and the carrier utilization efficiency is improved.

The carbon nanotube may be a single-walled carbon nanotube or a multi-walled carbon nanotube, and has a tube diameter of 1nm to 15nm, for example, 1nm, 5nm, 6nm, 8nm, 10nm, etc., and a tube length of 10nm to 30 μm, for example, 10nm, 20nm, 30nm, 100nm, 1.5 μm, 2 μm, 10 μm, 25 μm, 28 μm, etc.

In conclusion, the graphene carbon nanotube composite powder material with a unique sea urchin-shaped structure is obtained through a specific process, and the graphene microspheres are used as the fulcrum of the growth of the carbon nanotubes, so that the carbon nanotubes can be prevented from being tangled, and a stable mechanical support effect can be provided. The material can be well dispersed in a solvent and a polymer without adding a surfactant, forms a carbon staggered structure with different dimensionalities, long range and short range, better exerts the synergistic effect of the two, and has good application prospect.

The invention will be further illustrated by the following examples, but is not to be construed as being limited thereto. Unless otherwise specified, reagents, materials and the like used in the present invention are commercially available.

Preparation example 1

This preparation example is intended to illustrate a method for producing a carrier according to an embodiment of the present invention.

1) And (3) taking 4g of graphene oxide and 500mL of deionized water, and uniformly blending the graphene oxide and the deionized water by a mechanical stirrer at the rotating speed of 3000rpm for 30min to prepare a graphene oxide coarse dispersion liquid of 8 mg/mL.

2) 0.05g of ketjen black and 20ml of deionized water were taken and uniformly blended by magnetic stirring at a rotation speed of 200rpm for 30min to prepare a crude dispersion of conductive particles.

3) And adding the coarse dispersion liquid of the conductive particles into the graphene oxide coarse dispersion liquid, and processing the graphene oxide coarse dispersion liquid by using an ultracentrifugal grinder, wherein the rotating speed of the ultracentrifugal grinder is 15000rpm, and the processing time is 20min, so as to prepare the graphene oxide mixed dispersion liquid with the conductive particle intercalation.

4) And (2) granulating the graphene oxide mixed dispersion liquid intercalated with the conductive particles by using spray drying equipment to remove a solvent, wherein the treatment pressure of the spray drying equipment is 0.2MPa, the treatment flow rate is 1500ml/h, the treatment temperature is 140 ℃, and finally the carbon carrier is prepared.

Preparation example 2

This preparation example is intended to illustrate a method for producing a carrier according to another embodiment of the present invention.

2) And (3) granulating the graphene oxide mixed dispersion liquid by using spray drying equipment to remove a solvent, wherein the treatment pressure of the spray drying equipment is 0.2MPa, the treatment flow rate is 1500ml/h, and the treatment temperature is 140 ℃, so that the carbon carrier is obtained.

Example 1

This example is used to illustrate the preparation method of the graphene carbon nanotube composite material of the present invention

Fig. 2 shows a fluidized bed chemical vapor deposition apparatus for preparing the graphene carbon nanotube composite material, wherein the main body of the apparatus is a single-temperature zone thermal resistance type vertical tube furnace, the maximum experimental temperature can reach 1050 ℃, and the actual temperature floats within +/-1 ℃ of the set temperature in a constant temperature state, as shown in fig. 2. The heating cavity of the tube furnace can accommodate a quartz tube 100 with the maximum outer diameter of 2 inches, and the whole volume of the reaction cavity reaches 600 mL. In addition, each path of gas connected with the tubular furnace is controlled by a mass flow meter (MT51, Horiba Scientific), the maximum measuring range is 0 sccm-1000 sccm, and the maximum stable working pressure is 0.2 Mpa. Meanwhile, a liquid bubbling tank 200 filled with supersaturated ferrocene ethanol solution is arranged in the pipeline. The concrete structure is shown in figure 1.

1) A porous sieve plate 300 made of 100-mesh fused silica particles is additionally arranged in the quartz tube 100, 100mg of the carrier 400 of the preparation example 1 is loaded into the vertically arranged quartz tube, hydrogen and argon are respectively introduced at the flow rate of 300sccm at the same time, and the graphene oxide carrier 400 is stably suspended in the quartz tube 100 under the flow of gas.

2) Heating a fluidized bed reaction cavity to 450 ℃, introducing 100sccm Ar gas as a carrier gas, carrying ferrocene and ethanol into the reaction cavity through a supersaturated ferrocene ethanol solution with a constant temperature of 60 ℃ by a bubbling method, and then carrying out thermal cracking to form pre-carbonized iron (Fe) catalyst nanoparticles attached to the surface of a graphene oxide carrier, wherein the bubbling duration is 20 minutes.

3) Then the temperature of the fluidized bed reaction cavity is raised to 700 ℃, hydrogen gas and argon gas are respectively introduced at the same time at the flow rate of 300sccm, then carbon monoxide is introduced at the flow rate of 100sccm as a carbon source, and after the carbon monoxide gas is closed after the carbon source lasts for 30 minutes. Stopping the reaction, and after the equipment is cooled to room temperature, closing all the gases to obtain the graphene carbon nanotube composite material.

Fig. 3 is a scanning electron microscope image of the graphene carbon nanotube composite material of example 1, which shows that the graphene carbon nanotube composite material is sea urchin-like, and carbon nanotubes with lengths of tens of micrometers are dispersedly grown on the surface of a graphene microsphere, and are lapped with carbon nanotubes on other graphene microspheres to form a continuous conductive network. Fig. 4a and 4b are transmission electron micrographs of the graphene carbon nanotube composite material of example 1, respectively, and it can be seen from fig. 4a and 4b that the carbon nanotubes prepared under the conditions are single-walled carbon nanotubes with a tube diameter of 1nm to 3 nm.

Fig. 5 is a transmission electron microscope image of the catalyst nanoparticles formed in example 1, and fig. 6 is a statistical distribution diagram of the particle diameters of the catalyst nanoparticles formed in example 1. As can be seen from fig. 5 and 6, the catalyst nanoparticles on the surface of the graphene oxide are uniformly distributed, the average particle diameter is 1.78nm, and more than 95% of the particles have a diameter less than 3nm, which is beneficial to preparing the single-walled carbon nanotube with a relatively small tube diameter.

Example 2

The preparation method and the device are the same as the example 1, except that the temperature of the fluidized bed reaction chamber in the step 2) is 400 ℃.

Fig. 7 is a transmission electron microscope image of the catalyst nanoparticles formed in example 2, and fig. 8 is a statistical distribution diagram of the particle diameters of the catalyst nanoparticles formed in example 2. As can be seen from fig. 7 and 8, the catalyst nanoparticles on the surface of the graphene oxide are uniformly distributed, the average particle diameter is 1.22nm, and 98% or more of the particles have a diameter of less than 2 nm. It is demonstrated that the particle size of the catalyst can be reduced by lowering the cracking temperature of the catalyst precursor.

Example 3

The preparation method and the device are the same as the example 1, except that the temperature of the fluidized bed reaction chamber in the step 2) is 500 ℃.

Fig. 9 is a transmission electron microscope image of the catalyst nanoparticles formed in example 3, and fig. 10 is a statistical distribution diagram of the particle diameters of the catalyst nanoparticles formed in example 3. As can be seen from fig. 9 and 10, the catalyst nanoparticles on the surface of the graphene oxide are uniformly distributed, and the average particle size is 4.25nm, which indicates that the particle size of the catalyst can be significantly increased by increasing the cracking temperature of the catalyst precursor, thereby controlling and preparing the carbon nanotube with a larger tube diameter.

Fig. 11 is a transmission electron microscope image of the graphene carbon nanotube composite material of example 3, which shows that the carbon nanotubes prepared under the condition are multiwall carbon nanotubes, and the tube diameter is 10nm to 15 nm.

Example 4

The preparation process and apparatus were the same as in example 1, except that the carbon monoxide was introduced in step 3) for a period of 5 minutes.

Fig. 12 is a transmission electron microscope image of the graphene carbon nanotube composite material of example 4, and as can be seen from fig. 12, single-walled carbon nanotubes with a length of only tens of nanometers grow on the catalyst nanoparticles on the surface of graphene, which illustrates that the growth length of carbon nanotubes can be effectively controlled by controlling the carbon source introduction time during growth.

Example 5

The preparation method and apparatus were the same as in example 1 except that the carrier of preparation 2 was used in step 1).

Example 6

The preparation method and the device are the same as the example 1, except that carbon monoxide is not introduced in the step 3).

Fig. 13 is a high-resolution transmission electron microscope image of the thin layer region on the carbon support microsphere of preparation example 1, wherein the upper right corner is a fourier transform image of a dotted line frame portion, and a clear lattice structure is not shown, which can indicate that the degree of the surface defect of the support is high, and the defect is favorable for the dispersion of the catalyst nanoparticles on the surface of the support.

Fig. 14 is a high-resolution transmission electron microscope image of a thin-layer region on a graphene microsphere after annealing under other atmosphere conditions in the simulated carbon nanotube growth of example 6, where the upper right corner is a transmission electron microscope image locally enlarged by 5 times, and the lower right corner is a fourier transform image of a dashed-line frame part, which shows clear lattice points, and can show that a carrier is converted into a reduced graphene oxide microsphere with a complete structure after being processed under the carbon nanotube growth conditions. Is favorable for ensuring the whole conductivity of the graphene carbon nanotube composite powder.

Fig. 15 is an X-ray photoelectron spectrum of the carbon support microsphere of preparation example 1, and it can be seen that the microsphere has rich oxygen-containing functional groups, which is consistent with the defect conclusion of the TEM characterization shown in fig. 13. Fig. 16 is an X-ray photoelectron spectrum of the material obtained in example 6, and it can be seen that most of the oxygen-containing functional groups of the graphene oxide microsphere treated under the carbon nanotube growth condition are removed, and graphitized carbon occupies a great proportion, which is consistent with the above-mentioned TEM characterization of the reduced graphene oxide microsphere.

It should be noted by those skilled in the art that the described embodiments of the present invention are merely exemplary and that various other substitutions, alterations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the above-described embodiments, but is only limited by the claims.

Claims

1. A preparation method of a graphene carbon nanotube composite material is characterized by comprising the following steps:

granulating the graphene oxide dispersion liquid to remove a solvent to obtain a carrier;

the carrier is arranged in the reaction chamber;

adjusting the temperature of the reaction chamber to a first temperature, introducing a metal precursor, and cracking the metal precursor to form metal nanoparticles on the surface of the carrier to obtain microspheres; and

and adjusting the temperature of the reaction chamber to a second temperature, introducing a carbon source, and performing chemical vapor deposition reaction on the surface of the microsphere to grow the carbon nanotube to obtain the graphene carbon nanotube composite material.

2. The preparation method according to claim 1, wherein the graphene oxide dispersion liquid is a graphene oxide dispersion liquid in which conductive particles are intercalated, the conductive particles account for 1-30% of the total mass of the graphene oxide and the conductive particles, and the conductive particles are selected from one or more of carbon black, ketjen black, onion carbon and fullerene.

3. The method of claim 1, wherein the first temperature is from 100 ℃ to 700 ℃ and the second temperature is from 600 ℃ to 700 ℃.

4. The method according to claim 1, wherein the metal precursor is selected from one or more of a metal carbonyl compound and a metallocene compound, and the metallocene compound is selected from one or more of iron pentacarbonyl, iron nonacarbonyl, iron dodecacarbonyl, nickel tetracarbonyl, chromium hexacarbonyl, cobalt octacarbonyl, and ferrocene.

5. The method according to claim 1, wherein an inert carrier gas is introduced after the carrier is placed in the reaction chamber to suspend the carrier in the reaction chamber; the inert carrier gas is selected from one or more of nitrogen, argon, krypton and xenon, and the flow rate of the inert carrier gas is 300-1000 sccm.

6. The method according to claim 1, wherein the carbon source is selected from one or more of hydrocarbons, alcohols, ethers, ketones, phenols, and carbon monoxide; the time for introducing the carbon source is 1-60 min.

7. The graphene carbon nanotube composite material is characterized by having a sea urchin-like structure and comprising graphene microspheres and a plurality of carbon nanotubes formed on the surfaces of the graphene microspheres, wherein the graphene microspheres are formed by aggregating carbon sheets formed by multi-layer reduced graphene oxide.

8. The graphene-carbon nanotube composite material according to claim 7, wherein the graphene microspheres have nanopores inside, the particle size of the graphene microspheres is 0.1-100 μm, and the carbon sheet comprises 1-10 layers of reduced graphene oxide.

9. The graphene carbon nanotube composite of claim 7, wherein the reduced graphene oxide is a conductive particle intercalated reduced graphene oxide.

10. The graphene-carbon nanotube composite material according to claim 7, wherein the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube, the carbon nanotube has a tube diameter of 0.1nm to 15nm and a tube length of 10nm to 30 μm.