Three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material and preparation method thereof
Technical Field
The invention relates to a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material and a preparation method thereof, belonging to the field of new energy nano materials.
Background
Wearable electronic devices are a current research hotspot due to the characteristics of portability, flexibility, wearability and the like, and flexible electronic materials are important components of wearable electronic devices, and the properties of the flexible electronic materials determine the performance of the wearable electronic devices. Three-dimensional porous graphene frameworks, for example: graphene foam, water/aerogel, graphene sponge and the like are one of the most concerned flexible electronic materials in recent years, a three-dimensional framework of the flexible electronic material is formed by stacking micrometer-scale graphene sheets with different macroscopically oriented directions, a delocalized pi-bond conjugated structure of a graphene sheet layer is still maintained on a microscale, and the structure is favorable for electron transmission and greatly reduces the contact electron and solid-liquid interface resistance usually faced by a two-dimensional material. The three-dimensional porous graphene framework has an adjustable porous structure, high conductivity, high specific surface area, good flexibility and mechanical stability (the three-dimensional structure can inhibit pi-pi aggregation between graphene sheets), so that the three-dimensional porous graphene framework has excellent electrical properties and has great application potential in the application aspect of flexible electronic materials.
For three-dimensional porous graphene, the pore size distribution is one of the key factors determining the material performance, and researchers have tried to prepare three-dimensional porous graphene frameworks with appropriate pore size distribution by various methods. Drieschner et al report a preparation method of graphene foam, which is obtained by a chemical vapor deposition method using copper/nickel powder as a template, wherein the pore diameter (0.5-1 μm) of the graphene foam obtained by the method is far smaller than that of a three-dimensional porous graphene skeleton obtained by chemical vapor deposition using commercial nickel/copper foam as a template, so that the graphene foam has a higher specific surface area, and the specific capacitance is obtained when the graphene foam is used for an electric double-layer supercapacitor electrode. However, the specific capacitance (100F g) actually embodied by the material-1) And theoretical specific capacitance of graphene (-550F g)-1) The reason for this is that the pore size of the material is still large due to the large diameter of the copper particles and the loose template, which results in a limited increase of the specific surface area. In addition, since the pore size is large but the pore walls are thin, the foam is easily broken when pressed or bent, and the flexibility and mechanical strength are insufficient.
The problems of low specific surface area, low flexibility and insufficient mechanical strength of the material can be greatly improved by combining the three-dimensional porous graphene framework with the carbon nano tube, the carbon nano tube has excellent flexibility, and the unique tubular structure, rich mesopores and easy chemical modification can bring more choices for improving the performance of the composite material. However, a simple, efficient and controllable method for preparing a three-dimensional porous graphene skeleton-carbon nanotube composite is still lacking at present, on one hand, the carbon nanotubes are very easy to be wound into bundles, so that the effective area and the charge transmission efficiency are reduced, on the other hand, the carbon nanotubes are difficult to be uniformly distributed in the graphene skeleton, and some preparation methods reported at present are relatively complex and uncontrollable, such as: liquid phase composite processes (hydrothermal/solvothermal processes, etc.), chemical vapor deposition processes using commercial templates (copper foil, copper/nickel foam), and binder-assisted synthesis processes, among others.
Therefore, the preparation method of the three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material which is simple, controllable and efficient to prepare is researched, and the preparation method has great significance for the application of the graphene-carbon nanotube flexible composite material in the field of wearable electronics.
Disclosure of Invention
The invention aims to provide a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material and a preparation method thereof.
The material is characterized in that the carbon nano tube and the graphene are connected, supported and reinforced with each other, the material is a flexible composite material with a hierarchical porous structure and is prepared by a one-step chemical vapor deposition method, and a template for chemical vapor deposition is obtained by uniformly mixing copper powder and a single-walled carbon nano tube by a ball milling method and tabletting. The method is characterized in that single-walled carbon nanotubes are preassembled into a copper powder template by ball milling in advance, so that the solid-solid physical mixing method is simple to operate, the content of the carbon nanotubes in the graphene-single-walled carbon nanotube compound can be controllably adjusted by adjusting the amount of the carbon nanotubes added into copper powder (ball milling process), the graphene-copper powder is tabletted to reduce the gaps inside a copper powder-single-walled carbon nanotube mixture, and the water/aerogel material with the specific surface area, the mechanical strength and the flexibility higher than those of foam graphene is obtained after chemical vapor deposition, and the preparation process comprises the following steps: no binder is needed, the cost is low, the operation is simple, the equipment is simple, the application is wide, and the like.
The technical scheme of the invention is as follows:
the three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material is a flexible composite material with a hierarchical porous structure, a matrix of the flexible composite material is a three-dimensional porous graphene skeleton obtained by chemical vapor deposition with copper powder as a template, and single-walled carbon nanotubes embedded in the skeleton are preassembled into the copper powder template by ball milling in advance. The content of carbon nanotubes in the composite can be controllably adjusted by simply adjusting the amount of carbon nanotubes added to the copper powder (ball milling process).
The invention discloses a method for preparing a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material by adopting a ball milling method and a one-step chemical vapor deposition method. The preparation principle is that firstly, nano copper powder with a certain particle size and the single-walled carbon nanotube are uniformly mixed according to a certain mass ratio by a ball milling method and then are pressed into a copper powder-single-walled carbon nanotube self-supporting square block by a powder tablet press, and the content of the carbon nanotube in the graphene-single-walled carbon nanotube composite can be controllably adjusted by adjusting the amount of the carbon nanotube added into the copper powder (ball milling process). Then the square block is directly used as a template for chemical vapor deposition to deposit graphene, and copper powder is etched to obtain the three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite material (hereinafter referred to as composite material).
The preparation process of the invention comprises the following steps:
(1) preparing a nanometer copper powder-single-walled carbon nanotube composite template: adding 3-6 g of nano copper powder (with the diameter of 200-2000 nm) and 0.5-10 mg of single-walled carbon nanotube powder into a 50ml closed agate tank filled with inert gas (nitrogen or argon), fixing the tank in a ball mill, ball-milling for 4-10 h at the rotating speed of 400-800 rpm, placing the ball-milled single-walled carbon nanotube-nano copper powder composite in a square mold (2 x 2cm), pressing the powder into a self-supporting square block (2 x 2cm) at the pressure of 10-20 MPa by using a powder tablet press, and taking the block as a template for chemical vapor deposition.
(2) Preparing a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible compound: directly placing the self-supporting square block obtained in the step (1) into a quartz tube furnace, keeping the pressure in the tube at 500-8000 Pa, raising the temperature to 850-1050 ℃ at the speed of 10-30 ℃/min under the protection of high-purity argon (50-200 sccm), preserving the temperature for 20-60 min, fully annealing the square template, then performing chemical vapor deposition by taking methane as a carbon source, and then placing the self-supporting square block deposited with the graphene framework into a quartz tube furnace with the concentration of 1-3 mol L-1FeSO of (2)4Placing the solution at 60-100 ℃ for 6-48 hours, taking out the solution until the sample floats on the surface of the solution, and respectively using dilute hydrochloric acid (1-3M) and concentrated hydrochloric acidRepeatedly cleaning with nitric acid and deionized water, and freeze drying; putting the dried three-dimensional single-walled carbon nanotube-graphene skeleton into a quartz tube furnace, and heating for 30-60 minutes at 400-500 ℃ under the protection of high-purity argon (10-100 sccm); and pressing the obtained aerogel into a tablet by using a powder tablet press, and fixing the aerogel onto a flexible conductive film by using conductive silver paste to serve as a flexible electrode.
The invention has the advantages that: the composite material prepared by the invention has a hierarchical porous structure and good flexibility, and the carbon nano tubes are added into the graphene framework to play the roles of connecting, supporting and reinforcing the framework, so that the mechanical strength of the framework is increased, and the flexibility of the framework structure is greatly enhanced due to the excellent flexibility of the carbon nano tubes; the material is prepared by a conventional one-step chemical vapor deposition method; the template of the chemical vapor deposition is obtained by uniformly mixing copper powder and the single-walled carbon nanotube by using a ball milling method and tabletting, and the single-walled carbon nanotube is pre-assembled in the copper powder template by using ball milling in advance, so that the solid-solid physical mixing method is simple to operate, and the content of the carbon nanotube in the graphene-single-walled carbon nanotube composite can be controllably adjusted by adjusting the amount of the carbon nanotube added into the copper powder (ball milling process); the graphene-copper powder is tabletted to reduce the gaps inside the copper powder-single-walled carbon nanotube mixture, so that the water/aerogel material with the specific surface area, the mechanical strength and the flexibility higher than those of the foam graphene is obtained after the chemical vapor deposition.
Drawings
Fig. 1 is a macroscopic digital photograph of the three-dimensional porous graphene framework-single-walled carbon nanotube flexible electrode prepared in example 1;
fig. 2 is a scanning electron microscope photograph of the three-dimensional porous graphene framework-single-walled carbon nanotube composite material prepared in example 1.
Fig. 3 is a transmission electron microscope photograph of the three-dimensional porous graphene framework-single-walled carbon nanotube composite material prepared in example 1.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Example 1
Preparing a nanometer copper powder-single-walled carbon nanotube composite template: adding 5g of nano copper powder (with the diameter of 200-2000 nm) and 2mg of single-walled carbon nanotube powder into a 50ml closed agate tank filled with inert gas (nitrogen or argon), fixing the tank in a ball mill, carrying out ball milling for 6h at the rotating speed of 600rpm, placing the ball-milled single-walled carbon nanotube-nano copper powder composite in a square mold (2 x 2cm), pressing the powder into a self-supporting square block (2 x 2cm) at the pressure of 20MPa by using a powder tablet press, and taking the block as a template for chemical vapor deposition.
Preparing a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible compound: directly placing the self-supporting square block obtained in the step (1) into a quartz tube furnace, keeping the pressure in the tube at 1000Pa, raising the temperature to 1000 ℃ at the speed of 30 ℃/min under the protection of high-purity argon (200sccm), preserving the temperature for 30min, fully annealing the square template, then performing chemical vapor deposition by taking methane as a carbon source, and then placing the self-supporting square block deposited with the graphene framework into a quartz tube furnace with the concentration of 2mol L-1FeSO of (2)4Placing the solution at 80 ℃ for 48 hours, taking out the solution until the sample floats on the surface of the solution, repeatedly washing the solution by using dilute hydrochloric acid (2M), concentrated nitric acid and deionized water respectively, and freeze-drying the solution; placing the dried three-dimensional single-walled carbon nanotube-graphene skeleton into a quartz tube furnace, and heating at 500 ℃ for 30 minutes under the protection of high-purity argon (500sccm), wherein macroscopic digital photographs of the prepared three-dimensional porous graphene skeleton-single-walled carbon nanotube aerogel under the conditions are respectively shown in fig. 1 a; and pressing the obtained aerogel into a tablet by using a powder tablet press, and fixing the aerogel onto a flexible conductive film by using conductive silver paste to serve as a flexible electrode. The macroscopic digital photograph, the scanning electron microscope photograph and the transmission electron microscope photograph of the three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible composite prepared under the condition are respectively shown in fig. 1b, fig. 2 and fig. 3.
Example 2
Preparing a nanometer copper powder-single-walled carbon nanotube composite template: adding 5g of nano copper powder (with the diameter of 200-2000 nm) and 4mg of single-walled carbon nanotube powder into a 50ml closed agate tank filled with inert gas (nitrogen or argon), fixing the tank in a ball mill, carrying out ball milling for 6h at the rotating speed of 600rpm, placing the ball-milled single-walled carbon nanotube-nano copper powder compound in a square mold (2 x 2cm), pressing the powder into a self-supporting square block (2 x 2cm) at the pressure of 20MPa by using a powder tablet press, and taking the block as a template for chemical vapor deposition.
Preparing a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible compound: directly placing the self-supporting square block obtained in the step (1) into a quartz tube furnace, keeping the pressure in the tube at 1000Pa, raising the temperature to 1000 ℃ at the speed of 30 ℃/min under the protection of high-purity argon (200sccm), preserving the temperature for 30min, fully annealing the square template, then performing chemical vapor deposition by taking methane as a carbon source, and then placing the self-supporting square block deposited with the graphene framework into a quartz tube furnace with the concentration of 2mol L-1FeSO of (2)4Placing the solution at 80 ℃ for 48 hours, taking out the solution until the sample floats on the surface of the solution, repeatedly washing the solution by using dilute hydrochloric acid (2M), concentrated nitric acid and deionized water respectively, and freeze-drying the solution; putting the dried three-dimensional single-walled carbon nanotube-graphene skeleton into a quartz tube furnace, and heating for 30 minutes at 500 ℃ under the protection of high-purity argon (500 sccm); and pressing the obtained aerogel into a tablet by using a powder tablet press, and fixing the aerogel onto a flexible conductive film by using conductive silver paste to serve as a flexible electrode.
Example 3
Preparing a nanometer copper powder-single-walled carbon nanotube composite template: adding 5g of nano copper powder (with the diameter of 200-2000 nm) and 6mg of single-walled carbon nanotube powder into a 50ml closed agate tank filled with inert gas (nitrogen or argon), fixing the tank in a ball mill, carrying out ball milling for 6h at the rotating speed of 600rpm, placing the ball-milled single-walled carbon nanotube-nano copper powder compound in a square mold (2 x 2cm), pressing the powder into a self-supporting square block (2 x 2cm) at the pressure of 20MPa by using a powder tablet press, and taking the block as a template for chemical vapor deposition.
Preparing a three-dimensional porous graphene skeleton-single-walled carbon nanotube flexible compound: directly putting the self-supporting square block obtained in the step (1) into a quartz tube furnace, and keeping the pressure in the tube at 1000Pa and at a high levelRaising the temperature to 1000 ℃ at the speed of 30 ℃/min under the protection of pure argon (200sccm), preserving the heat for 30min, fully annealing the square template, then performing chemical vapor deposition by taking methane as a carbon source, and then placing the self-supporting square block body deposited with the graphene framework in a concentration of 2mol L-1FeSO of (2)4Placing the solution at 80 ℃ for 48 hours, taking out the solution until the sample floats on the surface of the solution, repeatedly washing the solution by using dilute hydrochloric acid (2M), concentrated nitric acid and deionized water respectively, and freeze-drying the solution; putting the dried three-dimensional single-walled carbon nanotube-graphene skeleton into a quartz tube furnace, and heating for 30 minutes at 500 ℃ under the protection of high-purity argon (500 sccm); and pressing the obtained aerogel into a tablet by using a powder tablet press, and fixing the aerogel onto a flexible conductive film by using conductive silver paste to serve as a flexible electrode.