A method for efficiently preparing CVD graphene powder

Abstract

The application relates to a method for efficiently preparing CVD graphene powder. 3+ The method comprises the following steps: taking dendritic copper powder as a substrate, taking C2H2 as a carbon source, taking HNO3 or Fe as an etchant, first depositing an amorphous carbon layer on the surface of the dendritic copper powder in situ at a lower temperature, then increasing the temperature to convert the amorphous carbon into a high-quality graphene film on the surface of the dendritic copper powder in situ, then completely dissolving the copper in the dendritic copper composite powder which has grown graphene on the surface by the etchant, and finally obtaining the high-quality CVD graphene powder through filtration, deionized water washing and drying. The method can effectively prevent the fusion and growth of the dendritic copper powder at high temperature, maintain the initial high specific surface area of the dendritic copper powder, and realize efficient preparation of the CVD graphene powder.

Description

TECHNICAL FIELD

[0001] The application provides a method for efficiently preparing CVD graphene powder, and belongs to the field of graphene powder preparation. BACKGROUND

[0002] Compared with Hummer's method graphene powder, CVD method graphene powder has the characteristics of less layer and less defect. However, the substrate used in the traditional CVD method for growing graphene is copper foil or foamed copper with small specific surface area, which is completely not suitable for efficiently preparing graphene powder. Nano copper powder with high specific surface area is not suitable for preparing graphene powder due to poor gas permeability and fusion and growth at high temperature. Although dendritic copper powder has the characteristics of high specific surface area and high gas permeability, it still has the objective difficulty of fusion and growth at high temperature and sharp reduction of specific surface area.

[0003] Therefore, it is particularly important to develop a method for efficiently preparing CVD method graphene powder. SUMMARY

[0004] The application aims to provide a method for efficiently preparing CVD method graphene powder. The method adopts the strategy of chemical vapor deposition of graphene on the surface of metal copper, which can prepare high-quality few-layer graphene. The metal copper is dendritic copper powder, which has high specific surface area and high gas permeability. The plasma enhanced strategy is adopted to deposit amorphous carbon film on the surface of the dendritic copper powder at low temperature in situ, so as to prevent the fusion and growth of the dendritic copper powder at high temperature and maintain its initial high specific surface area. Then the temperature is increased, and the amorphous carbon is converted into graphene on the surface of the dendritic copper powder in situ with the assistance of plasma, and the excess amorphous carbon is etched away to obtain graphene / dendritic copper composite powder with high specific surface area. Finally, high-quality CVD method graphene powder is prepared through etching, filtering, washing and drying.

[0005] The application is achieved through the following technical solutions.

[0006] A method for efficiently preparing CVD method graphene powder, and the specific steps are as follows:

[0007] The dendritic copper powder is used as the substrate, C2H2 is used as the carbon source, and HNO3 or Fe 3+The solution is an etching agent; first, the dendritic copper powder is heated to 50-400 DEG C under a low vacuum reducing atmosphere; then C2H2 is introduced, the plasma is turned on, and the dendritic copper powder is kept for a period of time to grow an amorphous carbon layer on the surface of the dendritic copper powder in situ; then the C2H2 is turned off, the temperature is raised to 700-950 DEG C, and the temperature is kept for 10-60 min; finally, the plasma is turned off, and the furnace is cooled to obtain the graphene / dendritic copper composite powder; the copper in the composite powder is completely dissolved by using the etching agent, and then the composite powder is filtered, washed with deionized water, and dried to finally obtain the high-quality CVD graphene powder.

[0008] The dendritic diameter of the dendritic copper powder is not more than 1 μm.

[0009] The absolute pressure of the low vacuum is 50-300 Pa.

[0010] The reducing atmosphere is an argon-hydrogen mixed atmosphere, and the argon-hydrogen ratio is 2:1-1:2.

[0011] The ratio of the amount of C2H2 introduced to the total amount of argon and hydrogen is 1:20-1:30.

[0012] The drying includes freeze drying or vacuum drying and air drying.

[0013] The dendritic copper powder can be replaced by dendritic nickel powder or dendritic copper-nickel alloy powder.

[0014] The C2H2 can be replaced by CH4 or C2H4.

[0015] The present application has the beneficial effect that the fusion and growth of the dendritic copper powder at high temperature can be effectively prevented, the initial high specific surface area of the dendritic copper powder can be maintained, and the efficient preparation of CVD graphene powder can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a SEM image of the raw dendritic copper powder, (a) low magnification-10000 times, (b) high magnification-100000 times.

[0017] Figure 2 is a SEM image of the Gr / Cu composite powder prepared in Example 1, (a) low magnification-10000 times, (b) high magnification-100000 times.

[0018] Figure 3 is is a SEM image of the CVD graphene powder prepared in Example 1, (a) low magnification-10000 times, (b) high magnification-100000 times.

[0019] Figure 4 is a SEM image of the Gr / Cu composite powder prepared in Comparative Example 1, (a) low magnification-10000 times, (b) high magnification-100000 times. DETAILED DESCRIPTION

[0020] The application will be further described in conjunction with the specific embodiments.

[0021] Example 1

[0022] The method for efficiently preparing CVD graphene powder has the following steps:

[0023] The dendritic copper powder is used as a substrate, C2H2 is used as a carbon source, and a solution containing Fe 3+ is used as an etchant. First, dendritic copper powder with an average dendritic diameter of 295 nm is heated to 350°C under a reducing atmosphere with an argon-hydrogen ratio of 3:2 at 120 Pa. Then, C2H2 is introduced (the ratio of the introduced amount to the total amount of argon and hydrogen is 1:25), and the plasma is turned on, and the temperature is kept for 10 min to enable in-situ growth of an amorphous carbon layer on the surface of the dendritic copper powder. Then, the C2H2 is turned off, and the temperature is increased to 750°C, and the temperature is kept for 10 min. Finally, the plasma is turned off, and the furnace is cooled down to obtain graphene / dendritic copper composite powder with an average dendritic diameter of about 298 nm. The copper in the composite powder is completely dissolved by using an etchant containing Fe 3+ , and then the composite powder is filtered, washed with deionized water for 5 times, and freeze-dried to finally obtain high-quality CVD graphene powder. Figure 1 Figure 2 Figure 3) .

[0024] Example 2

[0025] The method for efficiently preparing CVD graphene powder has the following steps:

[0026] The dendritic nickel powder is used as a substrate, C2H2 is used as a carbon source, and a solution containing HNO3 is used as an etchant. First, dendritic nickel powder with an average diameter of 130 nm is heated to 50°C under a reducing atmosphere with an argon-hydrogen ratio of 2:1 at 150 Pa. Then, C2H4 is introduced (the ratio of the introduced amount to the total amount of argon and hydrogen is 1:20), and the plasma is turned on, and the temperature is kept for 15 min to enable in-situ growth of an amorphous carbon layer on the surface of the dendritic nickel powder. Then, the C2H4 is turned off, and the temperature is increased to 700°C, and the temperature is kept for 15 min. Finally, the plasma is turned off, and the furnace is cooled down to obtain graphene / dendritic nickel composite powder with an average dendritic diameter of about 136 nm. The nickel in the composite powder is completely dissolved by using an etchant containing HNO3, and then the composite powder is filtered, washed with deionized water for 3 times, and air-dried to finally obtain high-quality CVD graphene powder.

[0027] Example 3

[0028] The method for efficiently preparing CVD graphene powder has the following steps:

[0029] ​​​The dendritic nickel-copper alloy powder with an average diameter of 985 nm is heated to 400°C under a reducing atmosphere with an argon-hydrogen ratio of 1:2 at 70 Pa. CH4 is introduced (the ratio of the amount of CH4 to the total amount of argon and hydrogen is 1:30), and a plasma is started. The temperature is kept for 20 min to grow an amorphous carbon layer on the surface of the dendritic nickel-copper alloy powder in situ. Then, the temperature is increased to 950°C, and the temperature is kept for 60 min. Finally, the plasma is turned off, and the graphene / dendritic nickel-copper alloy composite powder with an average dendritic diameter of about 772 nm is obtained. The nickel-copper alloy in the composite powder is completely dissolved by using an etching agent containing HNO3. After filtration, washing with deionized water for 6 times, and vacuum drying, the high-quality graphene powder is obtained by CVD.

[0030] The procedure of Comparative Example 1 is as follows:

[0031] The dendritic copper powder with an average dendritic diameter of 295 nm (see Figure 1 ) is directly heated to 750°C under a reducing atmosphere with an argon-hydrogen ratio of 3:2 at 120 Pa. C2H2 is introduced (the ratio of the amount of C2H2 to the total amount of argon and hydrogen is 1:25), and a plasma is started. The temperature is kept for 10 min to grow a graphene layer on the surface of the dendritic copper powder in situ. Then, C2H2 is turned off, and the plasma is turned off. The graphene / dendritic copper composite powder with an average dendritic diameter of about 7 μm is obtained (see Figure 4 ).

[0032] It can be seen from Comparative Example 1 and Example 1 that if graphene is directly deposited at high temperature (Comparative Example 1), the dendrites of the dendritic copper powder will fuse and grow at high temperature, the specific surface area of the copper powder will sharply decrease, and the amount of the grown graphene will sharply decrease. However, if a layer of amorphous carbon is first deposited in situ at low temperature, and then the temperature is increased to high temperature to convert the amorphous carbon into graphene in situ (Example 1), the high-temperature fusion and growth of the dendrites can be prevented, the initial high specific surface area of the dendritic copper powder can be perfectly maintained, and the amount of the grown graphene is 23.3 times (7 μm / 298 nm = 23.3 times) of that in Comparative Example 1.

Claims

1. A method for efficiently preparing CVD graphene powder, characterized in that: Using dendritic copper powder with a dendrite diameter of no more than 1 μm as the substrate, C2H2 as the carbon source, and containing HNO3 or Fe... 3+ The solution is used as the etchant; first, the dendritic copper powder is heated to 50-400℃ in a low-vacuum reducing atmosphere; then C2H2 is introduced, the plasma is turned on, and the temperature is maintained for a period of time to allow an amorphous carbon layer to grow in situ on the surface of the dendritic copper powder; then the C2H2 is turned off, the temperature is raised to 700-950℃, and the temperature is maintained for 10-60 minutes; finally, the plasma is turned off and the powder is cooled with the furnace to obtain graphene / dendritic copper composite powder; the copper in the composite powder is completely dissolved by the etchant, and then filtered, washed with deionized water, and dried to finally obtain high-quality CVD graphene powder.

2. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The absolute pressure of the low vacuum is 50–300 Pa.

3. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The reducing atmosphere is a mixture of argon and hydrogen, with an argon-to-hydrogen ratio of 2:1 to 1:

2.

4. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The ratio of C2H2 to the total amount of argon and hydrogen is 1:20 to 1:

30.

5. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The drying process includes freeze drying, vacuum drying, and forced-air drying.

6. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The dendritic copper powder can be replaced by dendritic nickel powder or dendritic copper-nickel alloy powder.

7. The method for efficiently preparing CVD graphene powder according to claim 1, characterized in that: The C2H2 mentioned can be replaced by CH4 or C2H4.

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