Three-layer porous graphene and preparation method thereof

Abstract

The invention discloses three-layer porous graphene and a preparation method thereof, and belongs to the field of nano materials. The preparation method of the three-layer porous graphene comprises the following steps: growing graphene on a copper substrate by adopting a chemical vapor deposition method to obtain the three-layer porous graphene, wherein hydrogen, shielding gas, methane and oxygen-containing gas or pure oxygen are introduced in the chemical vapor deposition process; the growth temperature of the chemical vapor deposition enables the copper substrate to be molten into a liquid state. Compared with the traditional method, the method provided by the invention does not need complex manpower and material resources, does not need special treatment on the substrate, and provides a method capable of realizing more efficient growth of the three-layer porous single crystal graphene.

Description

Technical Field

[0001] The present invention relates to the field of nanomaterials, and in particular to a three-layer porous graphene and a preparation method thereof. Background Art

[0002] Graphene is an allotrope of carbon. Due to its unique and stable two-dimensional atomic structure, it has enormous potential applications in many areas, including mechanics, electricity, optics, and thermodynamics. For example, due to its unique top-conical electronic structure, single-layer graphene has a carrier mobility several orders of magnitude higher than that of silicon materials commonly used in the semiconductor field. Common methods for preparing graphene include mechanical exfoliation, redox methods, chemical vapor deposition, and organic synthesis. Of these methods, mechanical exfoliation and chemical vapor deposition are widely used in the preparation of high-quality graphene single crystals because of the high quality of the graphene single crystals produced. However, while mechanical exfoliation can produce high-quality graphene single crystals in experiments, it requires a lot of manpower and has a very low yield. Chemical vapor deposition has long been considered the most promising method for preparing high-quality graphene due to its advantages such as high-quality graphene produced, strong controllable operability, and large-scale application.

[0003] Although single-layer graphene has excellent electrical properties, its zero band gap limits its further application possibilities. Recent studies have shown that the band gap of double-layer graphene and triple-layer graphene can be opened, and it also has great application prospects in fields such as superconductivity. Therefore, research on double-layer graphene and triple-layer graphene has attracted widespread attention. At present, the main method for preparing triple-layer graphene is still artificial stacking. This method has low yield and weak coupling between layers, which greatly limits the further development of triple-layer single-crystalline graphene. If triple-layer single-crystalline graphene can be simply prepared using the mature industrial chemical vapor deposition method, this will lay a good foundation for the performance research and industrial application of triple-layer single-crystalline graphene. Summary of the Invention

[0004] The purpose of the present invention is to provide a three-layer porous graphene and a preparation method thereof. The method of the present invention prepares three-layer single-crystalline graphene by a thermal chemical vapor deposition method.

[0005] The present invention first provides a method for preparing three-layer porous graphene, comprising the following steps:

[0006] Growing graphene on a copper substrate using a chemical vapor deposition method to obtain the three-layer porous graphene;

[0007] Wherein, hydrogen, protective gas, methane and oxygen-containing gas or pure oxygen are introduced during the chemical vapor deposition process;

[0008] The growth temperature of the chemical vapor deposition makes the copper substrate melt into a liquid state.

[0009] In the above-mentioned preparation method, the copper substrate includes copper foil and tungsten foil; the tungsten foil is used to support liquid copper during the chemical vapor deposition process;

[0010] The thickness of the copper foil is 50-100 microns;

[0011] The thickness of the tungsten foil is 50-100 microns.

[0012] In the above preparation method, the flow rate of hydrogen is 90-120 sccm; specifically, it can be 90-100 sccm;

[0013] The flow rate of the protective gas is 400-600 sccm, and can be specifically 500 sccm;

[0014] The flow rate of methane is 0-0.7 sccm, but not 0; specifically, it can be 0.2 sccm;

[0015] The flow rate of the oxygen-containing gas or pure oxygen is 0-10 sccm, but not 0; specifically, it can be 2 sccm, 5 sccm or 10 sccm.

[0016] When the flow ratio of methane, oxygen-containing gas, hydrogen and protective gas is 0.2:5:90:500, the obtained three-layer single-crystal graphene has a better morphology.

[0017] In one embodiment of the present invention, the flow rate of the hydrogen gas is 90 sccm;

[0018] The flow rate of the protective gas is 500 sccm;

[0019] The flow rate of methane is 0.2 sccm;

[0020] The flow rate of the oxygen-containing gas or pure oxygen is 5 ccm; wherein the volume percentage of oxygen in the oxygen-containing gas is 5%.

[0021] In the chemical vapor deposition process, the temperature is 1100-1250°C, specifically 1150°C, and the pressure is 0-1.01×10 5 Pa, but not 0; specifically 1.01×10 5 Pa.

[0022] In the above preparation method, the oxygen-containing gas is composed of oxygen and inert gas, wherein the volume percentage of oxygen is 0.5%-100%, but not 100%; specifically, the volume percentage of oxygen is 0.5%-10%; more specifically, it can be 5%;

[0023] The inert atmosphere may specifically be argon and / or nitrogen.

[0024] In the above-mentioned preparation method, the heating rate during the chemical vapor deposition process is 2-30°C / min;

[0025] The protective gas is argon and / or nitrogen.

[0026] In the above preparation method, the growth time is 0.5-2 hours, specifically 1 hour.

[0027] In the above preparation method, the copper substrate is annealed before the chemical vapor deposition step.

[0028] Specifically, in the annealing step, the annealing atmosphere is hydrogen;

[0029] The flow rate of the hydrogen gas is 10-100 sccm, specifically 100 sccm;

[0030] The annealing time is 10-60 min, specifically 30 min;

[0031] The annealing temperature is 110-1250°C.

[0032] In addition, the preparation method further comprises the following steps:

[0033] Before the chemical vapor deposition step, the copper substrate is pretreated as follows: the copper substrate is ultrasonically cleaned with hydrochloric acid solution, acetone, and anhydrous ethanol in sequence, and then dried with nitrogen;

[0034] In the ultrasonic cleaning step, the time can specifically be 6 minutes.

[0035] The preparation method may further include the following steps: after the chemical vapor deposition step, cooling the system in a mixed atmosphere of protective gas and hydrogen; in the cooling step, the flow rate of argon is specifically 500 sccm; the flow rate of hydrogen is specifically 90 sccm.

[0036] The present invention also provides three-layer porous graphene prepared by the above preparation method.

[0037] Specifically, the three-layer porous graphene is three-layer porous single-crystal graphene.

[0038] The method for preparing three-layer porous graphene provided by the present invention introduces oxygen during chemical vapor deposition (CVD) to prepare single-crystalline graphene using liquid copper. The three-layer single-crystalline graphene is prepared by regulating the flow rates of protective gas, oxygen, hydrogen, and methane. This method has the following advantages:

[0039] (1) The present invention discloses for the first time the growth of three-layer single-crystal graphene on a liquid copper substrate by a thermal chemical vapor deposition system;

[0040] (2) The present invention discloses for the first time that oxygen has an effective effect on the growth of three-layer single-crystal graphene;

[0041] (3) The present invention discloses for the first time that the ratio of oxygen to hydrogen is a key factor affecting the growth of single-layer graphene;

[0042] (4) The present invention discloses for the first time the growth mechanism of three-layer graphene grown on a liquid copper substrate by a thermal chemical vapor deposition system;

[0043] (5) The three-layer porous graphene prepared by the present invention is a three-layer single-crystalline graphene stacked in ABA form;

[0044] (6) Compared with the traditional method, the method of the present invention does not require complicated manpower and material resources, nor does it require special treatment of the substrate, and provides a method for more efficiently growing three-layer porous single-crystalline graphene. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is an optical microscope photo of the three-layer porous graphene single crystal prepared in Example 1;

[0046] Figure 2 The low-magnification and high-magnification electron scanning microscopy images of the three-layer porous graphene prepared in Example 1 are shown;

[0047] Figure 3 Optical image and corresponding Raman curve of the three-layer porous graphene prepared in Example 1 transferred from a liquid copper substrate to SiO2 / Si;

[0048] Figure 4 The selected area electron diffraction pattern and boundary high-resolution transmission electron microscopy image of the three-layer porous graphene prepared in Example 1;

[0049] Figure 5 Optical image of graphene prepared in Comparative Example 1 transferred from liquid copper substrate to SiO2 / Si and its corresponding Raman spectrum;

[0050] Figure 6 This is a Raman characterization curve of graphene prepared in Comparative Example 2;

[0051] Figure 7 The graphene liquid copper substrate prepared in comparative example 3 was transferred to the SiO2 / Si optical image;

[0052] Figure 8 This is an optical microscope image of the solid copper substrate of Comparative Example 4 after growth is completed;

[0053] Figure 9 This is a Raman characterization curve diagram of the solid copper substrate of Comparative Example 4. DETAILED DESCRIPTION

[0054] The present invention will be further described in detail below in conjunction with specific embodiments. The examples given are only for illustrating the present invention, not for limiting the scope of the present invention.

[0055] The experimental methods in the following examples are conventional methods unless otherwise specified.

[0056] The quantitative tests in the following examples were performed in triplicate unless otherwise specified, and the results were averaged.

[0057] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0058] Example 1: Introducing oxygen into a chemical vapor deposition system to grow three-layer porous graphene

[0059] (1) Cleaning copper foil and tungsten growth substrate

[0060] Copper foil (100 μm, 1 cm × 1 cm) and tungsten foil (100 μm, 1 cm × 1 cm) were ultrasonically cleaned with hydrochloric acid solution, acetone, and anhydrous ethanol for 6 min each, and then dried with nitrogen gas.

[0061] (2) Stack the copper foil on top of the tungsten foil to obtain a copper / tungsten substrate, which is then placed in a quartz tube. Align the copper / tungsten substrate with the center of the electric furnace thermocouple. After passing 100 sccm of hydrogen for 10 minutes, heating begins at a heating rate of 10°C / min. When the temperature in the center of the electric furnace reaches 1150°C, maintain stable annealing for 30 minutes.

[0062] (3) Graphene growth

[0063] The temperature of the quartz tube in the tubular furnace in step (2) was maintained at 1150°C, and 0.2 sccm of methane, 90 sccm of hydrogen, 5 sccm of a mixed gas of oxygen and argon (oxygen volume percentage of 5%), and 500 sccm of argon were introduced at the same time. 5 After growing for 1 hour at a pressure of Pa, the methane, oxygen and argon mixed gas was turned off and the mixture was cooled to room temperature in a tube furnace under a flow rate of 90 sccm of hydrogen and 500 sccm of argon mixed gas to obtain three-layer porous graphene. Figure 1 , scanning electron microscope photos such as Figure 2 As shown, the prepared samples were characterized by Raman, as Figure 3 In addition, transmission electron microscopy can also show that it is a three-layer graphene, as shown in Figure 4 shown.

[0064] Depend on Figure 1-Figure 4It can be seen that the graphene prepared in this embodiment is a three-layer porous single-crystal graphene, and its stacking method is ABA stacking.

[0065] Comparative Example 1: Effect of Hydrogen Flow Rate on Graphene Morphology During Thermal Chemical Vapor Deposition

[0066] The same method as in Example 1 was followed, except that the hydrogen flow rate during the chemical vapor deposition process in step (3) was adjusted to 80 sccm. By reducing the hydrogen flow rate, the etching effect of hydrogen on graphene was reduced, thereby affecting the morphology of the obtained graphene. Figure 5 Optical image of graphene transferred onto SiO2 / Si substrate.

[0067] Depend on Figure 5 It can be seen that the graphene prepared in this embodiment is non-uniform, and only shows two layers, three layers or multiple layers in some positions, so it is necessary to control the appropriate hydrogen flow rate.

[0068] Comparative Example 2: Effect of Oxygen on Experimental Results in Graphene Preparation by Thermal Chemical Vapor Deposition

[0069] The same method as in Example 1 was used, except that the oxygen flow rate during the chemical vapor deposition in step (3) was adjusted to 0 sccm. No graphene sample was obtained, and the Raman test showed that Figure 6 shown.

[0070] Depend on Figure 6 It can be seen that the growth results without the introduction of oxygen show that there is no obvious graphene characteristic signal, which indicates that the introduction of oxygen promotes the growth of graphene.

[0071] Comparative Example 3: Effect of methane on experimental results during the preparation of graphene by thermal chemical vapor deposition

[0072] Following the same method as in Example 1, only the methane flow rate during the chemical vapor deposition process in step (3) was adjusted to 0.8 sccm. After 6 minutes of growth, the graphene sample with a larger growth area had white silicon oxide deposits on its surface. The graphene sample transferred to the SiO2 / Si substrate was as follows: Figure 7 shown.

[0073] Depend on Figure 7 It can be seen that the growth of graphene is very uneven, which shows that the conditions in Example 1 are conditions for the dynamic equilibrium growth of graphene, and it is necessary to control the appropriate methane flow rate.

[0074] Comparative Example 4: The same conditions of thermal chemical vapor deposition method cannot produce three-layer porous graphene on the solid copper surface

[0075] The same method as in Example 1 was used, except that the chemical vapor deposition growth temperature in step (3) was adjusted to 1080°C, the hydrogen flow rate was reduced to 40 sccm, and the methane flow rate was increased to 10 sccm. This was done to increase the proportion of methane gas so that graphene could grow more easily on solid copper. After 3 hours of growth, no graphene sample could be prepared. The optical microscope photo shows Figure 8 As shown, the prepared samples were characterized by Raman, as Figure 9 shown.

[0076] Depend on Figure 8-Figure 9 It can be seen that there is some silicon oxide deposition on the copper surface, but Raman analysis shows no characteristic graphene signal. Therefore, temperature has a significant impact on graphene growth, and it is necessary to prepare three layers of porous graphene on a liquid copper substrate.

[0077] Example 2

[0078] The preparation method is the same as that of Example 1, except that during the growth process of step (3), 0.2 sccm of methane, 90 sccm of hydrogen, 10 sccm of oxygen and argon mixture (oxygen volume percentage 5%) and 500 sccm of argon are introduced at a flow rate of 1.01×10 5 After growing for 2 hours at a pressure of Pa, the methane, oxygen and argon mixed gas was turned off, and the tube furnace was cooled to room temperature under a flow rate of 90 sccm of hydrogen and 500 sccm of argon mixed gas to obtain three-layer porous graphene.

[0079] This embodiment obtained a three-layer graphene similar to that of embodiment 1, which is three layers of porous single-crystalline graphene and stacked in an ABA stacking manner. However, the morphology of the three-layer graphene is not as good as that of embodiment 1.

[0080] Example 3

[0081] The preparation method is the same as that in the embodiment, except that in the growth process of step (3), 0.2 sccm of methane, 90 sccm of hydrogen, 2 sccm of oxygen and argon mixed gas (oxygen volume percentage 5%) and 500 sccm of argon are introduced at a flow rate of 1.01×10 5 After growing for 40 minutes at a pressure of Pa, the methane, oxygen and argon mixed gas was turned off, and the tube furnace was cooled to room temperature under a flow rate of 90 sccm of hydrogen and 500 sccm of argon mixed gas to obtain three-layer porous graphene.

[0082] This embodiment obtained a three-layer graphene similar to that of embodiment 1, which is three layers of porous single-crystalline graphene and stacked in an ABA stacking manner. However, the morphology of the three-layer graphene is not as good as that of embodiment 1.

[0083] Example 4

[0084] The preparation method is the same as that of Example 1, except that during the growth process of step (3), 0.2 sccm of methane, 100 sccm of hydrogen, 5 sccm of oxygen and argon mixture (oxygen volume percentage 5%) and 500 sccm of argon are introduced at a flow rate of 1.01×10 5 After growing for 70 minutes at a pressure of Pa, the methane, oxygen and argon mixed gas was turned off, and the tube furnace was cooled to room temperature under a flow rate of 100 sccm of hydrogen and 500 sccm of argon mixed gas to obtain three-layer porous graphene.

[0085] This embodiment obtained a three-layer graphene similar to that of embodiment 1, which is three layers of porous single-crystalline graphene and stacked in an ABA stacking manner. However, the morphology of the three-layer graphene is not as good as that of embodiment 1.

Claims

1. A method for preparing three-layer porous graphene, comprising the following steps: Growing graphene on a copper substrate using a chemical vapor deposition method to obtain the three-layer porous graphene; in, During the chemical vapor deposition process, hydrogen, protective gas, methane and oxygen-containing gas or pure oxygen are introduced; The growth temperature of the chemical vapor deposition makes the copper substrate melt into a liquid state.

2. The preparation method according to claim 1, wherein: The copper substrate includes copper foil and tungsten foil; The thickness of the copper foil is 50-100 microns; The thickness of the tungsten foil is 50-100 microns.

3. The preparation method according to claim 1 or 2, characterized in that: The flow rate of the hydrogen gas is 90-120 sccm; The flow rate of the protective gas is 400-600 sccm; The flow rate of methane is 0-0.7 sccm, but not 0; The flow rate of the oxygen-containing gas or pure oxygen is 0-10 sccm, but not 0.

4. The preparation method according to claim 3, wherein: The flow rate of the hydrogen gas is 90 sccm; The flow rate of the protective gas is 500 sccm; The flow rate of methane is 0.2 sccm; The flow rate of the oxygen-containing gas or pure oxygen is 5 ccm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: During the chemical vapor deposition process, the temperature is 1100-1250°C and the pressure is 0-1.01×10 5 Pa, but not 0.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The oxygen-containing gas is composed of oxygen and inert gas, wherein the volume percentage of oxygen is 0.5%-100%, but is 100%; The inert atmosphere may specifically be argon and / or nitrogen.

7. The preparation method according to any one of claims 1 to 6, characterized in that: During the chemical vapor deposition process, the heating rate is 2-30°C / min; The protective gas is argon and / or nitrogen.

8. The preparation method according to any one of claims 1 to 6, characterized in that: The growth time is 0.5-2h.

9. The three-layer porous graphene prepared by the preparation method according to any one of claims 1 to 8.

10. The three-layer porous graphene according to claim 9, characterized in that: The three-layer porous graphene is three-layer porous single-crystal graphene.

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