Method for producing graphene using air, water plasma and solid precursors

Abstract

The application belongs to the field of nanometer material preparation, and particularly relates to a method for preparing graphene by using air, water plasma and solid-state precursor, which solves the problems of high preparation cost and low safety. The method comprises the following steps: placing solid organic matter in a vacuum chamber of a plasma enhanced chemical vapor deposition device, closing an air inlet valve; vacuumizing the vacuum chamber to a first preset pressure; opening the air inlet valve to make air with water vapor enter; starting a plasma source to excite air and water vapor plasma, and heating the vacuum chamber to a set temperature by a heater to make vertically oriented graphene start to grow; after growing for a period of time, closing the plasma source, the heater and the air inlet valve, vacuumizing the air pressure in the vacuum chamber to below a second preset pressure, and cooling; when the temperature is below a preset temperature, the vacuum chamber is vented, the vacuum chamber is opened, and the graphene is taken out. The method realizes the effects of low preparation cost, green environmental protection and high safety.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation, and specifically relates to a method for preparing graphene using air, water plasma and solid precursors. Background Technology

[0002] Vertically oriented graphene is a nanomaterial formed by vertically aligned few-layer graphene nanosheets. This material possesses excellent physicochemical properties, such as millisecond-level fast electrochemical response and ultra-high optical absorption rate, and has great application potential in fields such as electrochemical energy storage, light energy conversion, and high-performance sensors.

[0003] Currently, the main method for preparing vertically oriented graphene is plasma-enhanced chemical vapor deposition (PECVD). This method uses plasma excited by direct current, radio frequency, or microwave to convert carbon-containing gaseous precursors such as methane into active free radicals, thereby forming vertically oriented graphene structures on the surface of substrate materials such as nickel and silicon. However, this method requires the consumption of gaseous raw materials such as methane and hydrogen, resulting in high costs; moreover, the gases used are mostly flammable and explosive organic gases (such as methane, acetylene, and propane), posing a lower safety risk. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a method for preparing graphene using air, water plasma, and solid precursors that is low in preparation cost and highly safe.

[0005] To achieve the innovative objectives of this invention, the following technical solutions can be used:

[0006] A method for preparing graphene using air, water plasma, and solid precursors includes the following steps:

[0007] S1. Place the solid organic material in the vacuum chamber of the plasma-enhanced chemical vapor deposition equipment and close the inlet valve;

[0008] S2. Evacuate the vacuum chamber until the first preset pressure is reached;

[0009] S3. Open the air intake valve to allow air containing water vapor to enter the vacuum chamber;

[0010] S4. Turn on the plasma source to excite air and water vapor plasma, and then heat the temperature in the vacuum chamber to the set temperature through the heater to start the growth of vertically oriented graphene.

[0011] S5. After a period of growth, turn off the plasma source, heater and inlet valve, and pump the gas pressure in the vacuum chamber to below the second preset pressure for cooling;

[0012] S6: When the temperature of the vertically oriented graphene drops below the preset temperature, the vacuum chamber is vented, and finally the vacuum chamber is opened to remove the vertically oriented graphene.

[0013] This invention utilizes air and water vapor, which are widely available in nature and have virtually zero cost, as gaseous raw materials. Vertically oriented graphene is prepared by exciting plasma containing highly reactive O atoms, H atoms, and OH radicals, significantly reducing preparation costs and making it environmentally friendly. Compared to preparation methods involving flammable substances such as hydrogen and methane, this invention is safer. In the specific method steps, a solid organic material provides the carbon source, and oxygen atoms and oxygen-containing radicals are generated from water vapor and oxygen in the air. In steps S2 and S3, air and air containing water vapor are introduced into a vacuum chamber. The low-pressure vacuum environment inside facilitates plasma excitation and also prevents the combustion of organic matter. In step S4, oxygen and water, after being excited by the plasma source, generate oxygen atoms and oxygen-containing radicals. These oxygen atoms and radicals lower the decomposition energy barrier of hydrocarbons, reducing the required preparation temperature. After heating to a preset temperature in the heater, the solid organic precursor decomposes under the action of these active atoms and radicals, producing... Gaseous small-molecule organic matter is transformed into carbon-containing active free radicals, which are then deposited on the substrate surface to form vertically oriented graphene. No flammable or explosive gases are involved in this process, ensuring high safety. Furthermore, these active particles readily react with amorphous carbon impurities, effectively removing them during preparation. During the growth of vertically oriented graphene, oxygen atoms and oxygen-containing free radicals collide on the graphene surface, producing a micro-etching effect that creates defect structures. These defect sites serve as nucleation sites for newly formed graphene sheets, resulting in highly branched vertically oriented graphene and promoting growth.

[0014] Specifically, plasma-enhanced chemical vapor deposition equipment includes structures such as a vacuum chamber, a plasma source, and a vacuum pump, with an inlet valve and an outlet valve connected to the vacuum chamber.

[0015] In the above-described method for preparing graphene using air, water plasma, and solid precursors, the first preset pressure in step S2 is 2 Pa to 5 Pa.

[0016] The first preset pressure reaches a low-pressure vacuum state, which is conducive to plasma excitation.

[0017] In the above-described method for preparing graphene using air, water plasma, and solid precursors, in step S3, air and water vapor are thoroughly mixed in a mixing device to obtain air containing water vapor, and the outlet of the mixing device is connected to an air inlet valve.

[0018] The air mixed in the mixing device is mixed with water vapor and evenly distributed, which is conducive to the generation of oxygen atoms and oxygen-containing free radicals.

[0019] In the above-described method for preparing graphene using air, water plasma, and solid precursors, in step S3, when air containing water vapor enters the vacuum chamber, the gas pressure inside the vacuum chamber is adjusted by regulating the opening of the air inlet valve. Step S4 is then executed after the gas pressure inside the vacuum chamber stabilizes.

[0020] After the air pressure stabilizes, proceed to step S4 to ensure that the internal environment is stable under the conditions required for excitation.

[0021] In the above-described method for preparing graphene using air, water plasma, and solid precursors, the temperature is set to 300℃-800℃ in step S4.

[0022] In the above-described method for preparing graphene using air, water plasma, and solid precursors, the second preset pressure in step S5 is 2 Pa to 5 Pa.

[0023] In the above method for preparing graphene using air, water plasma and solid precursors, the growth time in step S5 is 30 min to 120 min.

[0024] In the above-described method for preparing graphene using air, water plasma, and solid precursors, the preset temperature in step S6 is 50℃-80℃.

[0025] In the above-described method for preparing graphene using air, water plasma, and solid precursors, in step S1, the solid organic material includes one or more of carbohydrates, fats, proteins, and artificially synthesized organic compounds.

[0026] In the above-described method for preparing graphene using air, water plasma, and solid precursors, in step S4, the plasma source includes any one or more of DC, radio frequency, and microwave.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] This invention utilizes air and water vapor, which are widely available in nature and have virtually zero cost, as gaseous raw materials. Vertically oriented graphene is prepared by exciting plasma containing highly reactive O atoms, H atoms, and OH radicals, significantly reducing preparation costs and making it environmentally friendly. Compared to preparation methods involving flammable substances such as hydrogen and methane, this invention is safer. In the specific method steps, a solid organic material provides the carbon source, and oxygen atoms and oxygen-containing radicals are generated from water vapor and oxygen in the air. In steps S2 and S3, air and air containing water vapor are introduced into a vacuum chamber. The low-pressure vacuum environment inside facilitates plasma excitation and also prevents the combustion of organic matter. In step S4, oxygen and water, after being excited by the plasma source, generate oxygen atoms and oxygen-containing radicals. These oxygen atoms and radicals lower the decomposition energy barrier of hydrocarbons, reducing the required preparation temperature. After heating to a preset temperature in the heater, the solid organic precursor decomposes under the action of these active atoms and radicals, producing... Gaseous small-molecule organic matter is transformed into carbon-containing active free radicals, which are then deposited on the substrate surface to form vertically oriented graphene. No flammable or explosive gases are involved in this process, ensuring high safety. Furthermore, these active particles readily react with amorphous carbon impurities, effectively removing them during preparation. During the growth of vertically oriented graphene, oxygen atoms and oxygen-containing free radicals collide on the graphene surface, producing a micro-etching effect that creates defect structures. These defect sites serve as nucleation sites for newly formed graphene sheets, resulting in highly branched vertically oriented graphene and promoting growth. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method steps provided by the present invention;

[0030] Figure 2 This is a simplified connection diagram of the preparation equipment provided by the present invention.

[0031] In the diagram, there are: 1. Gas mixing device; 2. Inlet valve; 3. Plasma-enhanced chemical vapor deposition equipment; and 4. Vacuum chamber. Detailed Implementation

[0032] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0033] Specific implementation examples Figure 1 , 2 As shown, the method for preparing graphene using air, water plasma, and solid precursors includes the following steps:

[0034] S1. Place the solid organic material in the vacuum chamber 4 of the plasma-enhanced chemical vapor deposition equipment 3 and close the inlet valve 2;

[0035] S2. Evacuate vacuum chamber 4 until the pressure reaches below 3 Pa;

[0036] S3. Open the air inlet valve 2 to allow air containing water vapor to enter the vacuum chamber 4;

[0037] S4. Turn on the plasma source to excite air and water vapor plasma, and then heat the temperature in vacuum chamber 4 to 500°C through the heater to start the growth of vertically oriented graphene.

[0038] S5. After 120 min of growth, turn off the plasma source, heater and inlet valve 2, and pump the gas pressure in the vacuum chamber 4 to below 3 Pa for cooling.

[0039] S6: When the temperature of the vertically oriented graphene drops to below the preset temperature of 60°C, the vacuum chamber 4 is vented, and finally the vacuum chamber 4 is opened to take out the vertically oriented graphene.

[0040] Specifically, the method of this invention uses air and water vapor, which are widely available in nature and have almost zero cost, as gaseous raw materials. Vertically oriented graphene is prepared by exciting plasma containing highly reactive O atoms, H atoms, and OH radicals, significantly reducing preparation costs and making it environmentally friendly. Compared to preparation methods involving flammable substances such as hydrogen and methane, this invention is safer. In the specific method steps, solid organic matter serves as a carbon-containing precursor to provide the carbon source, while oxygen atoms and oxygen-containing radicals are generated from water vapor and oxygen in the air. In steps S2 and S3, air and air containing water vapor are introduced into vacuum chamber 4. The low-pressure vacuum environment inside facilitates plasma excitation and also prevents the combustion of organic matter. In step S4, oxygen and water, after being excited by the plasma source, generate oxygen atoms and oxygen-containing radicals. These oxygen atoms and radicals lower the decomposition energy barrier of hydrocarbons, reducing the required preparation temperature. After being heated to a preset temperature by the heater, the solid organic precursor, under the influence of these active atoms and radicals... The process involves the pyrolysis of gaseous small organic molecules, which then form carbon-containing active free radicals. These free radicals eventually deposit on the substrate surface to form vertically oriented graphene. No flammable or explosive gases are involved, ensuring a high level of safety during the preparation process. Furthermore, these active particles readily react with amorphous carbon impurities, effectively removing them during the preparation process. During the growth of vertically oriented graphene, oxygen atoms and oxygen-containing free radicals collide on the graphene surface, creating a micro-etching effect that generates defect structures. These defect sites serve as nucleation sites for newly formed graphene sheets, resulting in highly branched vertically oriented graphene and promoting its growth.

[0041] In this embodiment, the plasma-enhanced chemical vapor deposition apparatus 3 includes a vacuum chamber 4, a plasma source, and a vacuum pump, etc. The vacuum chamber 4 is connected to an inlet valve 2 and an outlet valve.

[0042] As an optimization, in step S3, air and water vapor are thoroughly mixed in the mixing device 1 to obtain air containing water vapor. The outlet of the mixing device 1 is connected to the inlet valve 2. The air containing water vapor obtained in the mixing device 1 is evenly distributed, which is conducive to the generation of oxygen atoms and oxygen-containing free radicals.

[0043] As an optimization, when air containing water vapor enters vacuum chamber 4, the gas pressure inside vacuum chamber 4 is adjusted by regulating the opening of the air inlet valve 2. Step S4 is executed only after the gas pressure inside vacuum chamber 4 has stabilized. Executing step S4 after the gas pressure has stabilized ensures that the internal environment remains stable under the conditions required for excitation.

[0044] As an optimization of the embodiment, in step S1, the solid organic matter is selected from organic solid waste.

[0045] As an optimization, in step S4, the plasma source includes any one or more of DC, radio frequency, and microwave.

[0046] The process of preparing vertically oriented graphene using air + water vapor plasma and organic solid precursors in this embodiment is described in detail below:

[0047] First, the organic solid waste, serving as a precursor, is placed in the vacuum chamber 4 of the plasma-enhanced chemical vapor deposition (PECVD) apparatus 3, and the vent valve is closed. The vacuum pump integrated into the PECVD apparatus 3 evacuates the gas pressure inside the vacuum chamber 4 to below 3 Pa. Then, the vent valve is opened, allowing air to enter the plasma apparatus after carrying a certain amount of water vapor through the mixing device 1. The gas pressure inside the vacuum chamber 4 is adjusted by regulating the opening of the vent valve.

[0048] After the gas pressure inside vacuum chamber 4 stabilized, the plasma source was turned on to excite air-water vapor plasma. Once the temperature inside vacuum chamber 4 reached 700℃, vertically oriented graphene began to grow. After 60 minutes of growth, the plasma source, heater, and venting valve were turned off, and the gas pressure inside vacuum chamber 4 was evacuated to below 3 Pa for cooling. After the sample temperature dropped below 60℃, the gas was released, vacuum chamber 4 was opened, and the vertically oriented graphene was removed.

[0049] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing graphene using air, water plasma, and solid precursors, characterized in that, Includes the following steps: S1. Place the solid organic material in the vacuum chamber (4) of the plasma-enhanced chemical vapor deposition apparatus (3) and close the inlet valve (2); S2. Evacuate the vacuum chamber (4) until the first preset pressure is reached; S3. Open the air inlet valve (2) to allow air containing water vapor to enter the vacuum chamber (4); S4. Turn on the plasma source to excite air and water vapor plasma, and then heat the temperature inside the vacuum chamber (4) to the set temperature through the heater to allow the vertically oriented graphene to begin growing. S5. After a period of growth, shut off the plasma source, heater and inlet valve (2), and pump the gas pressure in the vacuum chamber (4) to below the second preset pressure for cooling. S6: When the temperature of the vertically oriented graphene drops below the preset temperature, the vacuum chamber (4) is vented, and finally the vacuum chamber (4) is opened to take out the vertically oriented graphene.

2. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S2, the first preset pressure is 2 Pa to 5 Pa.

3. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S3, air and water vapor are thoroughly mixed in the mixing device (1) to obtain air containing water vapor. The outlet of the mixing device (1) is connected to the air inlet valve (2).

4. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S3, when air containing water vapor enters the vacuum chamber (4), the gas pressure inside the vacuum chamber (4) is adjusted by adjusting the opening of the air inlet valve (2). Step S4 is executed after the gas pressure inside the vacuum chamber (4) stabilizes.

5. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S4, the temperature is set to 300℃-800℃.

6. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S5, the second preset pressure is 2 Pa to 5 Pa.

7. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S5, the growth time is 30 min to 120 min.

8. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S6, the preset temperature is 50℃-80℃.

9. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S1, the solid organic matter includes one or more of carbohydrates, fats, proteins, and artificially synthesized organic compounds.

10. The method for preparing graphene using air, water plasma, and solid precursors according to claim 1, characterized in that, In step S4, the plasma source includes any one or more of DC, radio frequency, and microwave.

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