A method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma

Abstract

This invention discloses a one-step synthesis method for sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma, belonging to the field of functionalized graphene preparation. The method includes the following steps: introducing a hydrocarbon compound into the central region of the magnetic rotating arc plasma to form a graphene precursor; introducing a sulfur source and a nitrogen source into the downstream first and second regions of the magnetic rotating arc plasma, respectively, to form a sulfur-containing precursor and a nitrogen-containing precursor; the plasma temperature at the sulfur source introduction location is higher than that at the nitrogen source introduction location; the graphene precursor, the sulfur-containing precursor, and the nitrogen-containing precursor react in the tail flame of the magnetic rotating arc plasma, and after cooling, sulfur / nitrogen co-doped graphene is obtained. This invention has the advantages of simple process, one-step synthesis, continuous reaction, and no need for a catalyst. The synthesized sulfur / nitrogen co-doped graphene has a high doping concentration and the doping level is easy to control, making it easy to achieve large-scale production and use as a high-efficiency microwave absorbing material.

Description

Technical Field

[0001] This invention belongs to the field of functionalized graphene preparation, specifically relating to a method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma. Background Technology

[0002] Graphene, a two-dimensional sheet-like sp2 hybrid carbon, possesses excellent electrical, mechanical, and thermal properties, making it a long-standing research hotspot. However, its highly stable crystal structure limits its applications, necessitating improvements to its properties. Research has revealed that doping graphene with certain elements alters some properties, further enhancing its usability. Currently, lightweight non-metallic elements such as N, B, S, and P are primarily used to dope graphene. When two or more heteroatoms are introduced into the graphene framework simultaneously, the resulting product is called co-doped graphene. Experimental and theoretical studies show that introducing two or more dopants can significantly alter the physicochemical properties of graphene. Sulfur / nitrogen co-doped graphene exhibits a large specific surface area, significant polarization characteristics, and numerous active sites, showing broad application prospects in electrocatalysis, microwave absorbing materials, and bio-power generation.

[0003] Methods for preparing sulfur / nitrogen co-doped graphene are still relatively rare. Chemical vapor deposition (CVD) and chemical post-treatment of graphene oxide are the main approaches for its preparation. For example, Ning et al. (High capacity Li storage in sulfur and nitrogen dual-doped graphene networks, Carbon, 2014, 79: 310-320) successfully prepared sulfur / nitrogen co-doped graphene using a combination of CVD and acid washing. Peng et al. (Sequencing dual dopants for an electromagnetic tunable graphene, Chemical Engineering Journal, 2021, 413: 127421) synthesized sulfur / nitrogen co-doped graphene using graphene oxide as a raw material through a two-step thermal treatment process. However, these methods often only yield low levels of doping, require multiple synthesis steps, and suffer from drawbacks such as significant waste liquid and gas emissions. They cannot achieve large-scale continuous production of high-doping-concentration, high-quality sulfur / nitrogen co-doped graphene, thus limiting the application of this type of graphene product.

[0004] Plasma-based gas-phase synthesis of graphene is a novel process developed in recent years. Graphene can be synthesized in one step through the pyrolysis of hydrocarbons using high-energy plasma, and it features the advantages of requiring no catalyst or substrate material. McGill University in Canada (Carbon blacks produced by thermal plasma: the influence of the reactor geometry on the product morphology. Plasma Chem Plasma P. 2010, 30: 267-279) and the Cheng Yi research group at Tsinghua University (Preparation of few-layer graphene nanosheets by radio-frequency induction thermal plasma. Carbon, 2015, 86: 38-45) reported a method for preparing graphene using radio-frequency plasma to treat methane; the University of Lisbon in Portugal (Microwave plasma-based direct synthesis of free-standing N-graphene. Phys Chem Chem Phys, 22: 4772-4787) reported a method for synthesizing nitrogen-doped graphene using microwave nitrogen plasma in the gas phase. Currently, plasma-gas phase synthesis of graphene mainly focuses on pure graphene or nitrogen-doped graphene, and there are no reports on plasma-gas phase preparation of sulfur-doped graphene.

[0005] Magnetic rotating arc plasma (MOAP) is a common type of non-transfer arc. Driven by an axial magnetic field, the arc rotates at high speed around an inner electrode, increasing the volume of the arc plasma and thus improving the mixing uniformity between the plasma and the feed gas, while reducing electrode ablation. It is widely used in the preparation of graphene and other nanomaterials. Currently, there are existing methods for the continuous and controllable preparation of graphene using MOAP, but there are no precedents for the preparation of sulfur / nitrogen co-doped graphene using MOAP. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma, which solves the shortcomings of existing technologies such as complex processes and difficulty in large-scale production.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma, wherein the method uses magnetic rotating arc plasma as the reaction condition, argon as the plasma working gas, hydrocarbon compounds as the carbon source, nitrogen as the nitrogen source, and carbon disulfide as the sulfur source; the method includes the following steps:

[0009] The described magnetic rotating arc plasma is generated by a magnetic rotating arc plasma device, which includes a hollow cathode and a ring anode coaxially mounted outside the hollow cathode. The top of the ring anode has a plasma working gas inlet, and a magnetic field coil is mounted outside the ring anode. The plasma working gas is introduced through the plasma working gas inlet, which induces an arc between the hollow cathode and the ring anode. Under the induction of the axial magnetic field, the arc rotates around the hollow cathode to form a magnetic rotating arc plasma. The axial magnetic field drives the arc to rotate at high speed around the cathode. The high-speed rotation of the arc increases the plasma volume and the temperature uniformity of the plasma region, which is beneficial to ensuring the uniformity of the products. The lower part of the annular anode has a first raw material inlet and a second raw material inlet from top to bottom. The first raw material inlet faces the first downstream region of the magnetic rotating arc plasma; the second raw material inlet faces the second downstream region of the magnetic rotating arc plasma. Since the magnetic rotating arc plasma has the characteristic of gradually decreasing temperature as it develops downstream, the temperature of the magnetic rotating arc plasma located in the first raw material inlet region is higher than that located in the second raw material inlet region. A cooling chamber is installed below the annular anode, and the lower part of the cooling chamber has a reaction tail gas exhaust port. Preferably, the cooling chamber includes a collection box and a water-cooled wall.

[0010] The magnetic rotating arc plasma is first ignited in an argon atmosphere. The central channel of the hollow cathode serves as the entrance for hydrocarbon compounds, which are introduced into the central region of the plasma through the hollow cathode to form a graphene precursor. As the magnetic rotating arc plasma progresses downstream, its temperature gradually decreases. Accordingly, carbon disulfide and nitrogen are introduced into the first and second downstream regions of the magnetic rotating arc plasma, respectively, to form a sulfur-containing precursor and a nitrogen-containing precursor. The graphene precursor, the sulfur-containing precursor, and the nitrogen-containing precursor react in the plasma tail flame, and after cooling, sulfur / nitrogen co-doped graphene can be obtained.

[0011] The introduction of hydrocarbon compounds, carbon disulfide, and nitrogen into the plasma region is subject to strict requirements. This is because: hydrocarbon compounds are the basic raw materials for graphene formation and need to be introduced into a high-temperature region to ensure complete dissociation of the raw materials; carbon disulfide is stable, containing only carbon and sulfur elements without introducing other impurities, and to ensure complete pyrolysis of carbon disulfide, the plasma temperature at the introduction location must be no lower than 5000K and no higher than 8000K; the temperature at the nitrogen introduction location must be no lower than 3000K and no higher than 5000K, allowing for the reasonable utilization of the residual plasma heat after the introduction of carbon disulfide and ensuring sufficient nitrogen-containing precursors for nitrogen dissociation; after introducing nitrogen, the temperature in the plasma tail flame must be ensured not to exceed 3000K to avoid excessive participation of sulfur and nitrogen atoms in the graphene nucleation process at high temperatures, which could affect the graphene crystal structure.

[0012] The described magnetic rotating arc has a discharge current of 100-1000 amperes, a discharge power of 10-1000 kilowatts, an axial magnetic field of 0.2-2 Tesla, an arc speed of 100-5000 revolutions per second, and a discharge pressure of 0.2-2 bar to ensure that the average temperature of the high-temperature region of the plasma exceeds 5000K.

[0013] The described hydrocarbon compounds are one or more of alkanes, alkenes, alkynes, cyclic hydrocarbons, and aromatic hydrocarbons; the molar flow rate of carbon atoms in the hydrocarbon compounds to the molar flow rate of argon, the plasma working gas, is no higher than 1:5. An excessively high ratio will lead to a high carbon concentration in the plasma atmosphere, resulting in graphene stacking and reduced graphene quality.

[0014] The molar flow rate of carbon atoms in the described hydrocarbon compounds is greater than 10:1 and less than 100:1 compared to the molar flow rate of sulfur atoms in carbon disulfide. Excessive carbon disulfide flow rate will introduce excessive carbon source, leading to graphene stacking and thus affecting graphene quality; excessively low carbon disulfide concentration will result in low sulfur doping, affecting the performance of doped graphene.

[0015] The molar flow rate of carbon atoms in hydrocarbon compounds to the molar flow rate of nitrogen atoms in nitrogen gas should be higher than 6:1 and lower than 60:1. Excessive nitrogen flow rate will introduce an excessive amount of nitrogen source. A large amount of nitrogen source participating in graphene nucleation will reduce the planar size of graphene, thus affecting the quality of graphene. Insufficient nitrogen flow rate will result in a low nitrogen doping amount, affecting the performance of doped graphene.

[0016] The sulfur / nitrogen-doped graphene described has 1-10 layers and a planar size of 100-300 nm; the nitrogen atom doping level in the sulfur / nitrogen-doped graphene is 1-15% (atomic ratio), and the sulfur atom doping level is 1-15% (atomic ratio).

[0017] The sulfur / nitrogen-doped graphene described has excellent dielectric properties and can be used as a microwave absorbing material.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention employs a one-step plasma synthesis method for sulfur / nitrogen co-doped graphene, which features a simple process, continuous reaction, and suitability for large-scale production.

[0020] The carbon source, sulfur source, and nitrogen source used in this invention are all conventional raw materials in the field, which are simple and readily available, and do not require the addition of catalysts or other organic solvents, thus resulting in low cost.

[0021] The synthesized sulfur / nitrogen co-doped graphene has a highly tunable doping level and excellent performance, making it suitable for use as a high-efficiency microwave absorbing material. Attached Figure Description

[0022] Figure 1 The diagram shows a magnetic rotating arc plasma device for preparing sulfur / nitrogen co-doped graphene according to an embodiment of the present invention, wherein: 1-hollow cathode, 2-ring anode, 3-magnetic field coil, 4-magnetic rotating arc plasma, 5-water-cooled wall, 6-collection box, 7-plasma working gas inlet, 8-hydrocarbon compound inlet, 9-first raw material inlet, 10-second raw material inlet, 11-sulfur / nitrogen co-doped graphene product, and 12-reaction tail gas emission port.

[0023] Figure 2 Transmission electron microscopy image of the product prepared in Example 1.

[0024] Figure 3 High-magnification transmission electron microscope image of the product prepared in Example 1.

[0025] Figure 4 X-ray photoelectron spectrum image of the product prepared in Example 1.

[0026] Figure 5 Microwave absorption performance test of the product prepared in Example 1.

[0027] Figure 6 Transmission electron microscopy image of the product prepared in Example 2.

[0028] Figure 7 X-ray photoelectron spectrum image of the product prepared in Example 2.

[0029] Figure 8 Transmission electron microscopy image of the product prepared in Comparative Example 1.

[0030] Figure 9 Transmission electron microscopy image of the product prepared in Comparative Example 2.

[0031] Figure 10 X-ray photoelectron spectrum image of the product prepared in Comparative Example 2. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0034] Figure 1 This diagram illustrates a magnetic rotating arc plasma device for preparing sulfur / nitrogen co-doped graphene according to an embodiment of the present invention. The device includes a hollow cathode 1 and an annular anode 2 coaxially mounted outside the hollow cathode. The top of the annular anode 2 has a plasma working gas inlet 7, and a magnetic field coil 3 is fitted around the outside of the annular anode 2. Plasma working gas is introduced through the plasma working gas inlet, initiating an arc between the hollow cathode and the annular anode. Under the induction of an axial magnetic field, the arc rotates around the hollow cathode to form a magnetic rotating arc plasma 4. The lower part of the annular anode 2 has a first raw material inlet 8 and a second raw material inlet 9 from top to bottom. The first raw material inlet faces a first downstream region of the magnetic rotating arc plasma; the second raw material inlet faces a second downstream region of the magnetic rotating arc plasma. A cooling chamber is installed below the annular anode, and the cooling chamber includes a collection box. The device consists of a water-cooled wall 5 and a reaction exhaust port 12 at the bottom of the cooling chamber. The process for preparing sulfur / nitrogen co-doped graphene is as follows: First, argon gas is introduced through the plasma working gas inlet 7 to purge the air in the device and to ignite an electric arc in the argon atmosphere to form an electric arc plasma. Then, hydrocarbon compounds are introduced through the hydrocarbon compound inlet 8, while carbon disulfide and nitrogen are introduced through the first raw material inlet 9 and the second raw material inlet 10, respectively. The introduced hydrocarbon compounds, carbon disulfide, and nitrogen are pyrolyzed and grown in the plasma environment to form sulfur / nitrogen co-doped graphene flue gas. The sulfur / nitrogen co-doped graphene flue gas is cooled by the water-cooled wall 5 and finally adheres to the inner wall of the collection box 6. The product adhering to the inner wall of the collection box is collected, which is sulfur / nitrogen co-doped graphene 11. The exhaust gas after the reaction is discharged through the reaction exhaust port 12.

[0035] The technical solution of the present invention will be further clearly and completely described below with reference to specific embodiments. It should be noted that the reaction device and reaction conditions in the embodiments are only examples made to make the technical solution of the present invention clearer, and do not mean that the present invention can only be implemented by the device or parameters in the embodiments. In addition, the contents not specifically disclosed in the following embodiments are common knowledge in the field, and therefore, they are not specifically described.

[0036] Example 1

[0037] The magnetic rotating arc plasma device in this embodiment is referenced. Figure 1 The annular anode 2 has an inner diameter of 35 mm, and the rod-shaped hollow cathode 1 has a diameter of 10 mm. Both are made of high-purity graphite with a purity of not less than 99.99%. The magnetic field coil 3 surrounding the annular anode 2 provides an axial magnetic field of 0.08 Tesla. Argon gas is introduced into the magnetic rotating arc device to purge the air, and the arc is ignited in the argon atmosphere to form a magnetic rotating arc plasma 4. The argon flow rate is 5 mol / min, the discharge current is 100 amperes, the power is 15 kW, and the discharge pressure is 1 bar. After 5 minutes of discharge, methane is selected as the hydrocarbon feedstock and introduced through hydrocarbon inlet 8 at a flow rate of 0.4 mol / min. Carbon disulfide is evaporated by oil bath heating and introduced into the plasma region as steam through the first feedstock inlet 9 at a flow rate of 0.015 mol / min, where the temperature is approximately 6000 K. Nitrogen gas is introduced into the rotating arc plasma region (temperature around 4000 K) through the second feedstock inlet 10 at a flow rate of 0.02 mol / min. After the introduction of nitrogen gas, the temperature of the plasma tail flame is approximately 2600 K. The reaction is stopped after 30 minutes, and the solid product adhering to the inner wall of the collection box 6, approximately 12 g, is collected.

[0038] Figure 2 The images shown are transmission electron microscope (TEM) images of the solid products in this embodiment. As can be seen, the solid products are all rolled graphene sheets with a size between 100-300 nm.

[0039] Figure 3 The high-magnification transmission electron microscope image of the solid product in this embodiment shows that graphene is composed of straight or curled graphite layers, and the number of layers is between 1 and 10.

[0040] Figure 4 The X-ray photoelectron spectroscopy (XPS) spectrum of the solid product in this example shows that the elemental composition of the graphene product is carbon, nitrogen, sulfur, and oxygen, proving that the product is sulfur / nitrogen co-doped graphene, with a nitrogen atom doping amount of approximately 12.7% and a sulfur atom doping amount of approximately 11.5%.

[0041] To characterize the complex permittivity and microwave absorption performance of the product, the solid product and paraffin were mixed uniformly at a mass ratio of 1:9 and pressed into a coaxial test sample. Based on this, the reflection loss (RL) of the sample was calculated using transmission line theory to characterize the microwave absorption performance of the product. Figure 5 This example demonstrates the microwave absorption performance testing of the solid product. Typically, an RL value below -10 dB is considered an effective indicator of the absorber. From... Figure 5 It can be seen that within the microwave frequency range of 3.7-9.3 GHz, the RL value is below -10 dB for absorber thicknesses of 1-5 mm. When the absorber thickness is 3 mm, the RL value reaches its optimal value (-36.2 dB) at 5.6 GHz. Microwave absorption performance tests confirm that the sulfur / nitrogen co-doped graphene prepared in this embodiment possesses excellent microwave absorption capabilities.

[0042] Example 2

[0043] The apparatus in this embodiment is the same as that in the previous embodiment, except for the discharge parameters and the flow rates of the hydrocarbon compound, carbon disulfide, and nitrogen. Specifically, the argon flow rate is 10 mol / min, the discharge current is 300 amperes, the power is 27 kW, and the discharge pressure is 1 bar; the hydrocarbon feedstock is acetylene with a flow rate of 0.3 mol / min; the carbon disulfide flow rate is 0.005 mol / min, and the nitrogen flow rate is 0.01 mol / min. The reaction is stopped after 30 minutes, and approximately 22 g of solid product adhering to the inner wall of the collection tank 6 is collected.

[0044] Figure 6 The images shown are transmission electron microscope (TEM) images of the solid products in this embodiment. It can be seen that the products are all rolled graphene sheets, with the size of the graphene sheets ranging from 100 to 300 nm.

[0045] Figure 7 The X-ray photoelectron spectrum of the solid product in this embodiment shows that the elemental composition of the graphene product is carbon, nitrogen, sulfur, and oxygen, proving that the product is sulfur / nitrogen co-doped graphene, with a nitrogen atom doping amount of about 3.2% and a sulfur atom doping amount of about 1.9%.

[0046] Example 3

[0047] The apparatus in this embodiment is the same as in the previous embodiment, except for the flow rates of carbon disulfide and nitrogen. The flow rate of carbon disulfide is 0.01 mol / min, and the flow rate of nitrogen is 0.015 mol / min. The reaction is stopped after 30 minutes, and the solid product adhering to the inner wall of the collection tank 6, approximately 17 g, is collected. X-ray photoelectron spectroscopy measurements show that the nitrogen atom doping content of the solid product in this embodiment is approximately 6.3%, and the sulfur atom doping content is approximately 5.8%.

[0048] Example 4

[0049] The apparatus in this embodiment is the same as that in the previous embodiment, except that the discharge parameters are different. The discharge current is 600 amperes, the power is 55 kilowatts, and the discharge pressure is 0.4 bar. X-ray photoelectron spectroscopy measurements show that the nitrogen atom doping content of the solid product in this embodiment is approximately 14.3%, and the sulfur atom doping content is approximately 10.8%.

[0050] Example 5

[0051] The magnetic rotating arc device in this embodiment is the same as in the previous embodiment, except that the type of hydrocarbon compound is different. The hydrocarbon feedstock is butane, and its flow rate is 0.1 mol / min. X-ray photoelectron spectroscopy measurements show that the nitrogen atom doping content of the solid product in this embodiment is approximately 10.3%, and the sulfur atom doping content is approximately 13.8%.

[0052] Comparative Example 1

[0053] This comparative example uses the same implementation method as Example 1, except that in this comparative example, methane, carbon disulfide and nitrogen all enter the magnetic rotating arc plasma region 4 from the hydrocarbon compound inlet 8. Figure 8 The transmission electron microscope image of the product prepared in this comparative example shows that the solid products in this comparative example are all distorted spherical structures and no longer have the characteristics of graphene. This is because the temperature in the plasma core region is high, and sulfur and nitrogen atoms participate excessively in the formation of graphene cores, affecting the graphene crystal structure and thus preventing the formation of graphene structure.

[0054] Comparative Example 2

[0055] This comparative example uses the same implementation method as Example 1, except that in this comparative example, nitrogen gas is introduced into the rotating arc plasma region from the first raw material inlet 9, and carbon disulfide is introduced into the plasma region from the second raw material inlet 10. Figure 9 The transmission electron microscope image of the product prepared in this comparative example shows that the solid products in this comparative example are all graphene products. Figure 10 The X-ray photoelectron spectroscopy (XPS) image of the product prepared for this comparative example shows that the elemental composition of the solid product is carbon, nitrogen, and oxygen, with no obvious signs of sulfur atom doping. This is because the temperature at which carbon disulfide is introduced is relatively low (approximately 4000 K), and the carbon disulfide cannot be fully pyrolyzed, thus failing to provide sufficient sulfur-containing precursors and consequently affecting sulfur atom doping.

[0056] As can be seen from the above examples and comparative examples, the preparation method of the present invention guides hydrocarbon compounds, carbon disulfide and nitrogen to different positions of the magnetic rotating arc plasma. Specifically, the hydrocarbon compounds are guided to the high-temperature region of the plasma core, the carbon disulfide is guided to the high-temperature region downstream of the plasma, and the nitrogen is guided to the low-temperature region downstream of the plasma. The resulting sulfur / nitrogen co-doped graphene has a high doping level and can be used as a high-performance microwave absorbing material, achieving unexpected technical effects and showing significant progress.

[0057] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0058] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma, characterized in that: Includes the following steps: Hydrocarbon compounds are introduced into the central region of the magnetic rotating arc plasma, where they undergo pyrolysis to form graphene precursors. A sulfur source is introduced into the first region downstream of the magnetic rotating arc plasma to form a sulfur-containing precursor. A nitrogen source is introduced into the second downstream region of the magnetic rotating arc plasma to form a nitrogen-containing precursor. The temperatures of the central region of the magnetic rotating arc plasma, the first downstream region of the magnetic rotating arc plasma, and the second downstream region of the magnetic rotating arc plasma decrease sequentially. Graphene precursors, sulfur-containing precursors, and nitrogen-containing precursors are reacted in the tail flame of a magnetic rotating arc plasma, and sulfur / nitrogen co-doped graphene is obtained after cooling. The temperature of the first downstream region of the magnetic rotating arc plasma is not lower than 5000K and not higher than 8000K; the temperature of the second downstream region of the magnetic rotating arc plasma is not lower than 3000K and not higher than 5000K; and the tail flame temperature of the magnetic rotating arc plasma is not higher than 3000K.

2. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 1, characterized in that: The discharge current of the magnetic rotating arc plasma is 100-1000 amperes, the discharge power is 10-1000 kilowatts, the axial magnetic field is 0.2-2 Tesla, the arc speed is 100-5000 revolutions per second, and the discharge pressure is 0.2-2 bar.

3. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 1 or 2, characterized in that: The magnetic rotating arc plasma is generated by a magnetic rotating arc plasma device, which includes a hollow cathode and an annular anode coaxially mounted outside the hollow cathode. The top of the annular anode has a plasma working gas inlet, and a magnetic field coil is mounted outside the annular anode. Plasma working gas is introduced through the plasma working gas inlet, which induces an electric arc between the hollow cathode and the annular anode. Under the induction of the axial magnetic field, the arc rotates around the hollow cathode to form a magnetic rotating arc plasma. The lower part of the annular anode has a first raw material inlet and a second raw material inlet from top to bottom. The first raw material inlet faces the first region downstream of the magnetic rotating arc plasma; the second raw material inlet faces the second region downstream of the magnetic rotating arc plasma. A cooling chamber is installed below the annular anode, and the lower part of the cooling chamber has a reaction tail gas emission port.

4. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 3, characterized in that: The cooling chamber includes a collection tank and water-cooled walls.

5. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 3, characterized in that: The hydrocarbon compound is one or more of alkanes, alkenes, alkynes, cyclic hydrocarbons, and aromatic hydrocarbons; the plasma working gas is argon; the molar flow rate of carbon atoms in the hydrocarbon compound to the molar flow rate of the plasma working gas is not higher than 1:

5.

6. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 3, characterized in that: The sulfur source is carbon disulfide; the molar flow rate of carbon atoms in the hydrocarbon compound to the molar flow rate of sulfur atoms in carbon disulfide is (10-100):

1.

7. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 3, characterized in that: The nitrogen source is nitrogen gas, and the molar flow rate of carbon atoms in the hydrocarbon compound to the molar flow rate of nitrogen atoms in the nitrogen gas is (6-60):

1.

8. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 1, characterized in that: The sulfur / nitrogen co-doped graphene has 1-10 layers and a planar size of 100-300 nm.

9. The method for one-step synthesis of sulfur / nitrogen co-doped graphene based on magnetic rotating arc plasma according to claim 1, characterized in that: The nitrogen atom doping content in the sulfur / nitrogen co-doped graphene is 1-15%, and the sulfur atom doping content is 1-15%.

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