CN116199211A - A kind of two-dimensional monolayer dendritic graphene film and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of graphene film preparation and discloses a two-dimensional single-layer dendritic graphene film and a preparation method thereof. The invention adopts a two-step growth method of chemical vapor deposition, that is, after synthesizing a graphene continuous single-layer film, hydrogen gas is continuously introduced to obtain a high-quality large-area continuous single-layer graphene dendrite film by utilizing the hydrogen gas etching effect. The Raman spectrum confirms that graphene is a single layer, the 2D peak intensity of graphene is greater than the G peak, and it has a perfect single Lorentzian peak type. The two-dimensional single-layer dendritic graphene film obtained by the invention has good stability and continuity, excellent sensing performance and catalytic performance, and has important application prospects in the fields of sensing and photocatalysis.

Description

A kind of two-dimensional monolayer dendritic graphene film and preparation method thereof

technical field

The invention relates to the technical field of graphene film preparation, in particular to a two-dimensional single-layer dendritic graphene film and a preparation method thereof.

Background technique

Graphene is a hexagonal honeycomb-shaped two-dimensional material composed of carbon atoms in sp ² hybridization mode, and its single atomic layer thickness is only 0.35nm. As a new member of the carbon family of materials, graphene has a series of novel physical and chemical properties that make it play a huge advantage in the fields of transparent conductive films, composite materials, optoelectronic devices, and catalytic energy storage. Researchers have attempted to combine graphene with photocatalytic materials to catalyze the decomposition of acidic or aqueous solutions to produce hydrogen. This composite method can effectively improve catalytic performance, thereby improving energy conversion efficiency. The research and development of hydrogen energy is of great significance, and it has become one of the research hotspots of new photocatalytic materials and their composite materials.

However, the surface of ordinary graphene is inert. When it is combined with traditional electrodes and used in the field of catalysis, although it can protect the metal from corrosion, graphene will also inhibit its chemical activity. By introducing defects, while maintaining the excellent properties of intrinsic graphene, increasing active reaction sites can improve its catalytic ability. Researchers at the University of Tsukuba in Japan have developed "porous" graphene-based electrodes that allow for more efficient hydrogen evolution reactions in acidic electrolytes. Compared with ordinary graphene, the porous graphene material is more hydrophilic, and at the same time it is easier to adsorb a single H atom, which provides an additional surface area for the hydrogen evolution reaction. However, the preparation of porous graphene is relatively complicated, and template methods, photolithography methods, and catalytic etching methods are generally used. Yi et al. covered the synthesized silica microspheres on the surface of copper foil, grown Gr on the surface of copper foil by chemical vapor deposition (CVD), and then cleaned amorphous SiO _x with hydrofluoric acid to obtain porous shaped graphene. Safron et al. used patterned aluminum oxide to mask copper foil, and used barrier-free guided CVD etching to generate Gr on the surface of copper foil. Fischbein first used SF ₆ to ion-etch amorphous SiNx to form a square hole of 1 μm ² , then transferred the mechanically stripped Gr to _SiNx , and ablated it with TEM electron beam to obtain nanopores. Although the above method can obtain a high-quality graphene pore structure, the operation cost is relatively high, and the etching process is often accompanied by the generation of pollutants.

The boundary of dendritic graphene is a kind of line defect. According to the law of thermodynamics, in order to achieve stability, the formation of the boundary is a spontaneous process. Reasonable design of the unbalanced boundary of graphene and its boundary defects can obtain dendritic graphene. Dendritic graphene has more nano-edges, which increases the edge reaction sites compared to dense graphene, electrons can move quickly, and the catalytic activity is also higher. Chinese patent CN103834993A discloses a method for preparing graphene dendrites. A square wave electrical signal is applied at both ends of the graphene oxide solution. When the current density exceeds the limit current density, there will be a serious lack of graphene oxide particles near the electrode, and only some crystal faces The whisker-like dendrites continue to grow, which are graphene dendrites. In this method, dendrites are easy to pile up to form a three-dimensional structure, and at the same time, impurity elements such as hydrogen and oxygen are unavoidable to pollute the graphite fried branch sample. Chinese patent CN108910868A discloses a method for preparing graphene dendrites on an insulating substrate. Graphene first forms a spherical shape, then grows branches at the top of the spherical shape, and grows dendrites on the branches, which is essentially a three-dimensional graphene dendrite structure. The preparation of two-dimensional monolayer dendritic graphene dendrites is still lacking. Based on this, the development of two-dimensional single-layer dendritic graphene with higher catalytic or sensing performance has become an urgent need in this field.

Contents of the invention

In view of this, the invention provides a kind of two-dimensional single-layer dendrite graphene film and preparation method thereof, to solve the problem that the existing graphene film is a three-dimensional graphene dendrite, and the problem of two-dimensional single-layer dendrite graphene There are gaps in the research.

In order to achieve the above object, the present invention adopts following technical scheme:

The invention provides a method for preparing a two-dimensional single-layer dendrite graphene film, comprising the steps of:

(1) Under the mixed gas of H ₂ and Ar, the substrate is annealed to obtain the processed substrate;

(2) under the mixed gas of _H2 and _CH4 , heat treatment growth is carried out to the processed substrate, obtain initial graphene thin film;

(3) Under the mixed gas of _H2 and Ar, the initial graphene film is etched to obtain a two-dimensional single-layer dendritic graphene film.

Preferably, in the step (1), the flow rate of Ar is 280-340 sccm, the flow ratio of H ₂ and Ar is 1:14-17; the substrate is copper foil or copper film.

Preferably, in the step (1), the heating rate of the annealing treatment is 12-18° C./min, the temperature of the annealing treatment is 1020-1080° C., and the annealing treatment time is 30-40 minutes.

Preferably, in the step (2), the flow rate of CH ₄ is 3-5 sccm, and the flow ratio of H ₂ and CH ₄ is 18-22:1.

Preferably, in the step (2), the temperature for heat treatment growth is 1045-1055° C., and the time for heat treatment growth is 50-80 minutes.

Preferably, in the step (3), the flow rate of H ₂ is 10-30 sccm, and the flow ratio of H ₂ and Ar is 1:14-17.

As a preference, in the step (3), etching is carried out H ₂ etching to the initial graphene film during the process of cooling down to room temperature; the etching time is 25-40min.

As preferably, in described step (3), after etching finishes, stop _H2 and the mixed gas of Ar, pass into Ar afterwards to obtain two-dimensional single-layer dendritic graphene film.

The present invention also provides the two-dimensional single-layer dendrite graphene film prepared by the preparation method of the two-dimensional single-layer dendrite graphene film.

It can be seen through the above-mentioned technical solution that, compared with the prior art, the beneficial effects of the present invention are as follows:

The invention adopts a chemical vapor deposition two-step growth method to obtain a high-quality large-area continuous single-layer graphene dendrite film. The Raman spectrogram confirms that graphene is a single layer, and the 2D peak intensity of graphene is greater than the G peak, and has a perfect single Lorentzian peak type, that is, the two-dimensional single-layer dendritic graphene film of the present invention has higher transmission Sensitive and catalytic performance, has important application prospects in the field of sensing and photocatalysis.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the scanning electron microscope picture under different magnifications of the obtained two-dimensional single-layer dendritic graphene film of the embodiment 1 of the present invention, wherein, the magnification of a is 100 times, and the magnification of b is 500 times;

Fig. 2 is the optical microscope picture of the obtained two-dimensional monolayer dendritic graphene film of the embodiment of the present invention 1;

Fig. 3 is the optical microscope picture of the obtained two-dimensional single-layer dendritic graphene film of the embodiment of the present invention 1 after being oxidized in air;

Fig. 4 is the Raman spectrum of the two-dimensional single-layer dendritic graphene film obtained in Example 1 of the present invention, wherein, _ID = 34.7, I _G = 93.0, I2 _D = 159.5, I _2D /I _G = 1.72, I _D = 28.0;

Fig. 5 is the Raman spectrum of the two-dimensional single-layer dendritic graphene film obtained in Example 2 of the present invention, wherein, _ID = 98.2, I _G = 209.4, I _2D = 371.1, I _2D /I _G = 1.77, I _D ＝89.2;

Fig. 6 is the scanning electron microscope picture under the different magnifications of the obtained continuous graphene monolayer film of comparative example 1 of the present invention, wherein, the magnification of a is 83 times, and the magnification of b is 123 times;

Fig. 7 is the scanning electron microscope picture of the graphene dendrite obtained in Comparative Example 2 and 3 of the present invention, wherein, a is the scanning electron microscope picture of the graphene dendrite obtained in Comparative Example 1, and b is the scanning electron microscope of the graphene dendrite obtained in Comparative Example 3 picture;

8 is a schematic diagram of the preparation process of the two-dimensional single-layer dendritic graphene film of the present invention, wherein, stage I is an annealing stage, stage II is a growth stage, and stage III is an etching stage.

Detailed ways

The invention provides a method for preparing a two-dimensional single-layer dendrite graphene film, comprising the steps of:

(1) Under the mixed gas of H ₂ and Ar, the substrate is annealed to obtain the processed substrate;

(2) under the mixed gas of _H2 and _CH4 , heat treatment growth is carried out to the processed substrate, obtain initial graphene thin film;

(3) Under the mixed gas of _H2 and Ar, the initial graphene film is etched to obtain a two-dimensional single-layer dendritic graphene film.

In the present invention, the substrate is pretreated before the annealing treatment. The steps of the pretreatment are: the substrate is ultrasonically cleaned in ethanol and acetone respectively for 10-20 minutes, and then dried with _N2 to obtain the pretreated substrate. Treated substrate;

The time for ultrasonic cleaning is preferably 12-18 minutes, more preferably 14-16 minutes; ultrasonic cleaning can remove impurities and organic matter on the surface of the substrate.

In the present invention, in the step (1), the mixed gas of H _and Ar is introduced in the following manner: when the vacuum degree in the reactor chamber is reduced to below 0.7 Pa, Ar is introduced and heated until the temperature reaches annealing When processing the temperature, keep the introduction of Ar and feed H ₂ .

In the present invention, in the step (1), the flow rate of Ar is preferably 280-340 sccm, more preferably 290-320 sccm; the ratio of the flow rate of H _and Ar is preferably 1:14-17, more preferably 1: 15-16; the substrate is preferably copper foil or copper film, more preferably copper foil.

In the present invention, in the step (1), the heating rate of the annealing treatment is preferably 12-18°C/min, more preferably 13-16°C/min; the temperature of the annealing treatment is preferably 1020-1080°C, more preferably 1030-1060° C.; the annealing treatment time is preferably 30-40 minutes, more preferably 34-38 minutes.

In the present invention, in the step (2), the flow rate of CH ₄ is preferably 3-5 sccm, more preferably 4 sccm; the ratio of the flow rates of H ₂ and CH ₄ is preferably 18-22:1, more preferably 19-2 sccm 21:1.

In the present invention, in the step (2), the heat treatment growth temperature is preferably 1045-1055°C, more preferably 1048-1050°C; the heat treatment growth time is preferably 50-80min, more preferably 60-70min.

In the present invention, in the step (3), the flow rate of _H2 is preferably 10-30 sccm, more preferably 15-25 sccm; the ratio of the flow rates of _H2 and Ar is preferably 1:14-17, more preferably 1 : 15-16.

In the present invention, in described step (3), etch is carried out _H2 etching to initial graphene film in the process of being lowered to room temperature processing; The furnace is naturally cooled; the etching time is preferably 25-40 minutes, more preferably 30-35 minutes.

In the present invention, in the step (3), after the etching finishes, stop _H2 and the mixed gas of Ar, then feed Ar to obtain the two-dimensional single-layer dendritic graphene film; the feeding amount of the Ar is preferably In order to make the vacuum chamber reach atmospheric pressure, it can be opened.

The present invention also provides the two-dimensional single-layer dendrite graphene film prepared by the preparation method of the two-dimensional single-layer dendrite graphene film.

The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

Example 1

(1) Pretreatment of the copper foil substrate: Put the copper foil in ethanol and acetone in sequence for ultrasonic cleaning for 15 minutes to remove impurities and other contaminated organic matter on the surface of the copper foil. After the ultrasonic cleaning is completed, the copper foil is blown dry with _N2 to complete the pretreatment of the substrate before growth.

(2) Annealing treatment of the substrate: Put the pretreated copper foil into the quartz boat, place the push rod in the constant temperature area of the growth chamber, close the chamber door, turn on the mechanical pump, and wait until the vacuum degree in the chamber is reduced to 0.65Pa When 320sccmAr was introduced, the heating phase was started, and the heating rate was 15°C/min. After the temperature reaches 1050° C., the introduction of Ar is kept, 20 sccmH ₂ is introduced, and the temperature is kept for 30 minutes, and the substrate is annealed before growth.

(3) Growth of graphene: After the annealing is completed, 80 sccmH ₂ and 4 sccm CH ₄ are passed through at 1045° C. to grow graphene for 60 min.

(4) Etching of graphene: after the growth is completed, close the flow of CH ₄ , keep the flow rate of H _20sccm , feed 320sccmAr, stop the power supply and cool naturally with the furnace, etch for 30min, then cool down to room temperature, and cut off For the supply of _H2 and Ar gas mixture, turn off the mechanical pump. Finally, Ar is injected (the amount of Ar input ensures that the pressure in the vacuum chamber is the same as the external atmospheric pressure so that the vacuum chamber can be opened), and the prepared sample is taken out, that is, the two-dimensional single-layer dendritic graphene film.

Example 2

(1) Pretreatment of the copper film substrate: put the copper film in sequence in ethanol and acetone and ultrasonically clean it for 12 minutes to remove impurities and other contaminated organic matter on the surface of the copper foil. After the ultrasonic cleaning is completed, the copper foil is blown dry with _N2 to complete the pretreatment of the substrate before growth.

(2) Annealing treatment of the substrate: Put the pretreated copper foil into the quartz boat, place the push rod in the constant temperature area of the growth chamber, close the chamber door, turn on the mechanical pump, and wait until the vacuum degree in the chamber is reduced to 0.7Pa When 300sccmAr was introduced, the heating phase was started, and the heating rate was 12°C/min. After the temperature reaches 1040° C., the introduction of Ar is kept, 20 sccmH ₂ is passed through, and the temperature is kept for 35 minutes, and the substrate is annealed before growth.

(3) Growth of graphene: After the annealing is completed, 60 sccmH ₂ and 3 sccm CH ₄ are passed through at 1050° C. to grow graphene for 70 min.

(4) Etching of graphene: after the growth is completed, close the flow of CH ₄ , keep the flow rate of H _20sccm , feed 300sccmAr, and stop the power supply to cool naturally with the furnace, perform etching for 30min, then cool down to room temperature, and cut off For the supply of _H2 and Ar gas mixture, turn off the mechanical pump. Finally, Ar is injected (the amount of Ar input ensures that the pressure in the vacuum chamber is the same as the external atmospheric pressure so that the vacuum chamber can be opened), and the prepared sample is taken out, that is, the two-dimensional single-layer dendritic graphene film.

Example 3

(1) Pretreatment of the copper foil substrate: Put the copper foil in ethanol and acetone in sequence for ultrasonic cleaning for 18 minutes to remove impurities and other contaminated organic matter on the surface of the copper foil. After the ultrasonic cleaning is completed, the copper foil is blown dry with _N2 to complete the pretreatment of the substrate before growth.

(2) Annealing treatment of the substrate: Put the pretreated copper foil into the quartz boat, place the push rod in the constant temperature area of the growth chamber, close the chamber door, turn on the mechanical pump, and wait until the vacuum degree in the chamber is reduced to 0.6Pa When 350sccmAr was introduced, the heating phase was started, and the heating rate was 16°C/min. After the temperature reaches 1050° C., the introduction of Ar is kept, 20 sccmH ₂ is passed through, and the temperature is kept for 32 minutes, and the substrate is annealed before growth.

(3) Growth of graphene: After the annealing is completed, 100 sccmH ₂ and 5 sccm CH ₄ are passed through at 1055° C. to grow graphene for 40 min.

(4) Etching of graphene: after the growth is completed, turn off the flow of CH ₄ , keep the flow rate of H ₂₀ sccm, feed 350 sccmAr, stop the power supply and let the furnace cool naturally, perform etching for 30 minutes, then cool down to room temperature, and cut off For the supply of _H2 and Ar gas mixture, turn off the mechanical pump. Finally, Ar is injected (the amount of Ar input ensures that the pressure in the vacuum chamber is the same as the external atmospheric pressure so that the vacuum chamber can be opened), and the prepared sample is taken out, that is, the two-dimensional single-layer dendritic graphene film.

Comparative example 1

The difference from Example 1 is that H ₂ is not introduced in the etching stage of graphene, and the others are the same as in Example 1, and finally a continuous graphene monolayer film is obtained.

Comparative example 2

The difference from Example 1 is: the flow of CH in the growth stage of graphene is ₁ sccm, and the flow of _H is 20 sccm. Others are the same as in Example 1, and graphene dendrites are finally obtained.

Comparative example 3

The difference from Example 1 is: the flow of CH in the growth stage of graphene is ₂ sccm, and the flow of _H is 40 sccm. Others are the same as in Example 1, and graphene dendrites are finally obtained.

From the comparison of the graphene film layers obtained in the examples and comparative examples, it can be seen that the present invention obtains high-quality large-area continuous single-layer graphene dendrite films, and the Raman spectrum confirms that graphene is a single layer, and the 2D peak intensity of graphene is greater than G peak, and has a perfect single Lorentz peak type, the two-dimensional single-layer dendritic graphene film obtained in the present invention has excellent continuity and integrity, and has important application prospects in the fields of sensing and photocatalysis.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (9)

1. The preparation method of the two-dimensional single-layer dendrite graphene film is characterized by comprising the following steps of:

(1) At H ₂ Annealing the substrate under the mixed gas of Ar to obtain a treated substrate;

(2) At H ₂ And CH (CH) ₄ Performing heat treatment growth on the treated substrate under the mixed gas to obtain an initial graphene film;

(3) At H ₂ Under the mixed gas of Ar and the initial graphene filmAnd etching to obtain the two-dimensional single-layer dendrite graphene film.

2. The method for preparing a two-dimensional monolayer dendrite graphene film according to claim 1, wherein in the step (1), the flow rate of Ar is 280-340 sccm and H ₂ And Ar is 1: 14-17; the substrate is copper foil or copper film.

3. The method for preparing a two-dimensional monolayer dendrite graphene film according to claim 2, wherein in the step (1), the temperature rise rate of the annealing treatment is 12-18 ℃/min, the annealing treatment temperature is 1020-1080 ℃, and the annealing treatment time is 30-40 min.

4. The method for preparing a two-dimensional monolayer dendrite graphene film according to claim 3, wherein in the step (2), CH ₄ The flow rate of (3-5 sccm) H ₂ And CH (CH) ₄ The flow ratio of (2) is 18-22: 1.

5. the method for preparing a two-dimensional monolayer dendrite graphene film according to claim 1 or 4, wherein in the step (2), the temperature of the heat treatment growth is 1045 to 1055 ℃ and the time of the heat treatment growth is 50 to 80 minutes.

6. A method for producing a two-dimensional monolayer dendrite graphene film according to any one of claims 1 to 3, wherein in step (3), H ₂ The flow rate of (C) is 10-30 sccm, H ₂ And Ar is 1:14 to 17.

7. The method of preparing a two-dimensional monolayer dendrite graphene film according to claim 6, wherein in the step (3), the etching is performed by H on the initial graphene film during the process of cooling to room temperature ₂ Etching; the etching time is 25-40 min.

8. The two-dimensional monolayer dendrite of claim 7The preparation method of the graphene film is characterized in that in the step (3), H is stopped after etching is finished ₂ And introducing Ar into the mixed gas of Ar to obtain the two-dimensional monolayer dendrite graphene film.

9. The two-dimensional monolayer dendrite graphene film prepared by the method for preparing the two-dimensional monolayer dendrite graphene film according to any one of claims 1 to 8.

Images