Heteroatom-doped reduced graphene oxide material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of carbon materials, and particularly relates to a heteroatom-doped reduced graphene oxide material as well as a preparation method and application thereof. According to the method, a cyclic voltammetry method is adopted, and a working electrode is subjected to pre-oxidation treatment in a sulfate solution; performing an oxidation-reduction reaction on the pre-oxidized working electrode in a solution containing heteroatoms to obtain a heteroatom-doped reduced graphene oxide material; the working electrode is made of a carbon material; the heteroatoms comprise one or more of nitrogen atoms, fluorine atoms, sulfur atoms and boron atoms. The method is mild in reaction condition, simple to operate, high in controllability and free of side reaction, and the prepared heteroatom-doped reduced graphene oxide material has high electrochemical performance and catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon materials, and particularly relates to a heteroatom-doped reduced graphene oxide material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to their wide sources, safety, environmental friendliness, and adjustable structures, carbon materials have received extensive attention in energy and environmental fields such as the development of high-efficiency energy storage devices, electrolysis of water, and electrochemical sensing. Although traditional carbon materials have good electrical conductivity and structural stability, the active sites provided during the electrochemical reaction process are limited, which restricts their electricity storage capacity and catalytic efficiency.

[0003] Ion-doped carbon materials, especially heteroatom-doped carbon materials, have received extensive attention in the fields of electrochemical energy storage, electrochemical catalysis, and electrochemical sensing. By introducing foreign atoms to change the electronic structure of carbon materials, the electrochemical performance of such materials can be effectively improved, such as enhancing electrical conductivity, improving surface wettability, and providing more active sites, thus showing better performance in applications such as batteries, supercapacitors, and surface catalysis.

[0004] Currently, a variety of methods for preparing heteroatom-doped carbon materials have been reported, and each method has its own characteristics and scope of application, specifically including: pyrolysis method, chemical vapor deposition (CVD) method, hydrothermal / solvothermal method, template method, direct mixing and calcination method, electrochemical deposition method, wet chemical method, and laser-induced graphitization. Among them, the pyrolysis method is commonly used, but the pyrolysis process usually requires high-temperature conditions, which may lead to side reactions and thus affect their electrochemical performance and catalytic activity. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a heteroatom-doped reduced graphene oxide material, a preparation method thereof, and an application thereof. The method has mild reaction conditions, is simple to operate, has strong controllability, does not occur side reactions, and the prepared heteroatom-doped reduced graphene oxide material has high electrochemical performance and catalytic activity.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of a heteroatom-doped reduced graphene oxide material, comprising the following steps:

[0008] Performing a pre-oxidation treatment on a working electrode in a sulfate solution by cyclic voltammetry;

[0009] Performing an oxidation-reduction reaction on the pre-oxidized working electrode in a solution containing heteroatoms to obtain a heteroatom-doped reduced graphene oxide material;

[0010] The working electrode is a carbon material;

[0011] The heteroatoms include one or more of nitrogen atoms, fluorine atoms, sulfur atoms, and boron atoms.

[0012] Preferably, the carbon material is one or more of graphite paper, graphite rod, carbon paper, and carbon brush.

[0013] Preferably, the heteroatom-containing solution is one or more of a nitrogen-containing solution, a fluorine-containing solution, a sulfur-containing solution, and a boron-containing solution; the concentration of the solute in the nitrogen-containing solution is 1.5 - 2.5 mol / L; the concentration of the solute in the fluorine-containing solution is 1 - 2.5 mol / L; the concentration of the solute in the sulfur-containing solution is 1 - 2.5 mol / L; the concentration of the solute in the boron-containing solution is 1 - 2.5 mol / L.

[0014] Preferably, the nitrogen-containing solution is one or more of ammonium nitrate solution, nitric acid solution, sodium nitrate solution, ammonium sulfate solution, ammonia water solution, and imidazolium-based ionic liquid solution; the fluorine-containing solution is potassium fluoride solution and / or ammonium tetrafluoroborate solution; the sulfur-containing solution is thiosulfate solution and / or sulfite solution; the boron-containing solution is one or more of ammonium tetrafluoroborate solution, tetrafluoroborate-based ionic liquid solution, boric acid solution, and sodium borohydride solution.

[0015] Preferably, the sulfate is one or more of sodium sulfate, potassium sulfate, and magnesium sulfate; the concentration of the sulfate in the sulfate solution is 0.5 - 1.5 mol / L.

[0016] Preferably, the parameters of the pre-oxidation treatment are: temperature is room temperature, initial voltage is 0 - 1 V, maximum voltage is 1.5 - 2.5 V, minimum voltage is 0 - 1 V, scanning speed is 0.02 - 0.1 V / s, number of scanning cycles is 10 - 100 cycles, and current density is 5 - 200 mA / cm 2 。

[0017] Preferably, the parameters of the redox reaction are: temperature is room temperature, initial voltage is 0 - 1 V, maximum voltage is 1.5 - 3 V, minimum voltage is -1.2 - -0.8 V, scanning speed is 0.02 - 0.05 V / s, number of scanning cycles is 50 - 300 cycles, and current density is 5 - 200 mA / cm 2 。

[0018] Preferably, the cyclic voltammetry is carried out using a three-electrode system; in the three-electrode system, the counter electrode is a platinum wire or a platinum sheet, and the reference electrode is an Ag / AgCl electrode or a calomel electrode.

[0019] The present invention also provides a heteroatom-doped reduced graphene oxide material prepared by the preparation method described in the above technical solution, which includes reduced graphene oxide and heteroatoms doped on the surface and between the layers of the reduced graphene oxide;

[0020] The heteroatoms include one or more of nitrogen atoms, fluorine atoms, sulfur atoms, and boron atoms;

[0021] The nitrogen atoms are doped in the form of pyridine nitrogen, pyrrole nitrogen, or graphitic nitrogen. The pyridine nitrogen or pyrrole nitrogen is formed by the nitrogen atoms and the carbon atoms in the reduced graphene oxide. The boron atoms are doped in the form of substituting carbon atoms. The sulfur atoms are doped by forming S-C covalent bonds, and the fluorine atoms are doped by forming C-F covalent bonds.

[0022] The present invention also provides the application of the heteroatom-doped reduced graphene oxide material described in the above technical solution in electrodes, and the electrodes include one or more of electrochemical sensing electrodes, energy storage electrodes, and electrolysis electrodes.

[0023] The present invention provides a preparation method of a heteroatom-doped reduced graphene oxide material. The cyclic voltammetry method is used to pre-oxidize the working electrode in a sulfate solution; an oxidation-reduction reaction is carried out on the pre-oxidized working electrode in a solution containing heteroatoms to obtain a heteroatom-doped reduced graphene oxide material; the working electrode is a carbon material; the heteroatoms include one or more of nitrogen atoms, fluorine atoms, sulfur atoms, and boron atoms.

[0024] The present invention adopts the cyclic voltammetry method, and the carbon material is converted into a heteroatom-doped reduced graphene oxide material through ion intercalation, oxidation, and reduction. In this process, as the positive overpotential increases, the carbon material is oxidized to form oxygen-containing functional groups such as hydroxyl groups, epoxy groups, and carboxyl groups at the edges. At the same time, the interlayer spacing gradually opens under the action of hydrolysis bubbles, and then the heteroatoms are inserted into the interlayer and adsorbed on the oxygen-containing functional groups or planes through electrostatic attraction, cation-π, hydrogen bonds, etc., while dehydrogenating. When the scanning potential is reversed, as the negative overpotential increases, the oxygen-containing functional groups adsorbed with heteroatoms are reduced and hydrogenated, so that the heteroatoms are embedded in the lattice of the carbon material, thereby making the material have high electrochemical performance and catalytic activity. This method has mild reaction conditions, simple operation, environmental friendliness, strong controllability, low cost, does not occur side reactions, and is suitable for large-scale production. Description of the Drawings

[0025] Figure 1 CV curve graph of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1;

[0026] Figure 2 XPS graph of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1;

[0027] Figure 3 CV curve diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2;

[0028] Figure 4 XPS diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2;

[0029] Figure 5 CV curve diagram of the boron atom-doped reduced graphene oxide material prepared in Example 3;

[0030] Figure 6 XPS diagram of the boron atom-doped reduced graphene oxide material prepared in Example 3;

[0031] Figure 7 CV curve diagram of the sulfur atom-doped reduced graphene oxide material prepared in Example 4;

[0032] Figure 8 XPS diagram of the sulfur atom-doped reduced graphene oxide material prepared in Example 4;

[0033] Figure 9 Raman, XRD, and XPS test result diagrams of the nitrogen-doped graphene oxide prepared in Comparative Example 1;

[0034] Figure 10 XPS test result diagram of the sulfur-doped graphene oxide prepared in Comparative Example 2;

[0035] Figure 11 Mott-Schottky curve diagram of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1;

[0036] Figure 12 Mott-Schottky curve diagram of the boron atom-doped reduced graphene oxide material prepared in Example 3;

[0037] Figure 13 Mott-Schottky curve diagram of the sulfur atom-doped reduced graphene oxide material prepared in Example 4;

[0038] Figure 14 Original data diagram of the Tafel curve test of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1;

[0039] Figure 15 Fitted diagram of the Tafel curve test of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1;

[0040] Figure 16 Electrochemical impedance (EIS) test diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2;

[0041] Figure 17 CV test chart of nitrogen-doped graphene oxide prepared for Comparative Example 1;

[0042] Figure 18 CV test chart of sulfur-doped graphene oxide prepared for Comparative Example 2. Detailed implementation mode

[0043] The present invention provides a preparation method of a heteroatom-doped reduced graphene oxide material, which is characterized by including the following steps:

[0044] Using cyclic voltammetry, pre-oxidize the working electrode in a sulfate solution;

[0045] Perform an oxidation-reduction reaction on the pre-oxidized working electrode in a solution containing heteroatoms to obtain a heteroatom-doped reduced graphene oxide material;

[0046] The working electrode is a carbon material;

[0047] The heteroatoms include one or more of nitrogen atoms, fluorine atoms, sulfur atoms, and boron atoms.

[0048] Unless otherwise specified, the present invention has no special requirements for the sources of the raw materials used, and commercially available products well-known to those skilled in the art can be used.

[0049] As an implementation mode, the carbon material is a bulk carbon material; the carbon material is one or more of graphite paper, graphite rod, carbon paper, and carbon brush, and is graphite paper in a specific embodiment. Graphite paper is widely sourced, inexpensive, and easily available.

[0050] As an implementation mode, the cyclic voltammetry is carried out using a three-electrode system; in the three-electrode system, the counter electrode is a platinum wire or a platinum sheet, which is a platinum wire in a specific embodiment, and the reference electrode is an Ag / AgCl electrode or a calomel electrode, which is an Ag / AgCl electrode in a specific embodiment. Platinum has strong inertness and is a conventional counter electrode material. The surface area of the platinum wire is small, which is more suitable for situations with a small current density. The potential of the Ag / AgCl electrode is stable and the applicable pH value range is wide.

[0051] As an implementation mode, the sulfate is one or more of sodium sulfate, potassium sulfate, and magnesium sulfate, which is sodium sulfate in a specific embodiment; the concentration of the sulfate in the sulfate solution is 0.5 - 1.5 mol / L, which is 1 - 2 mol / L in a specific embodiment. Sulfate does not introduce other foreign atoms but can be inserted into the graphite interlayer and can promote hydrolysis oxidation.

[0052] As an implementation manner, the parameters of the pre-oxidation treatment are as follows: the temperature is room temperature, specifically 15 - 25°C in specific embodiments; the initial voltage is set to 0 - 1V, specifically 0V in specific embodiments; the maximum voltage is set to 1.5 - 2.5V, specifically 1.8 - 2.1V in specific embodiments; the minimum voltage is set to 0 - 1V, specifically 0V in specific embodiments; the scanning speed is 0.02 - 0.1V / s, specifically 0.03 - 0.05V / s in specific embodiments; the number of scanning cycles is 10 - 100 cycles, specifically 10 - 75 cycles in specific embodiments; the current density is 5 - 200 mA / cm 2 , specifically 10 - 100 mA / cm 2 .

[0053] In the present invention, the pre-oxidation treatment opens the interlayer spacing of the carbon material, laying a foundation for the next step of heteroatom doping. In the present invention, the pre-oxidation treatment can open the interlayer spacing, which is beneficial to the subsequent embedding of heteroatom-containing ions into the graphite interlayer; the conditions of the pre-oxidation can just open the graphite interlayer spacing and will not damage the apparent structure of the carbon material.

[0054] As an implementation manner, the heteroatom-containing solution is one or more of a nitrogen-containing solution, a fluorine-containing solution, a sulfur-containing solution, and a boron-containing solution. Specifically, in specific embodiments, it is a nitrogen-containing solution, a fluorine-containing solution, a sulfur-containing solution, or a boron-containing solution; the nitrogen-containing solution is one or more of an ammonium nitrate solution, a nitric acid solution, a sodium nitrate solution, an ammonium sulfate solution, an ammonia water solution, and an imidazolium ionic liquid solution. Specifically, in specific embodiments, it is an ammonium nitrate solution; the concentration of the solute in the nitrogen-containing solution is 1.5 - 2.5 mol / L, specifically 1.5 - 2 mol / L in specific embodiments; the fluorine-containing solution is a potassium fluoride solution and / or an ammonium tetrafluoroborate solution. Specifically, in specific embodiments, it is a potassium fluoride solution; the concentration of the solute in the fluorine-containing solution is 1 - 2.5 mol / L, specifically 1 - 2 mol / L in specific embodiments; the sulfur-containing solution is a thiosulfate solution and / or a sulfite solution. Specifically, in specific embodiments, it is a thiosulfate solution; the thiosulfate is sodium thiosulfate; the concentration of the solute in the sulfur-containing solution is 1 - 2.5 mol / L, specifically 1.25 - 2 mol / L in specific embodiments; the boron-containing solution is one or more of an ammonium tetrafluoroborate solution, a tetrafluoroborate ionic liquid solution, a boric acid solution, and a sodium borohydride solution. Specifically, in specific embodiments, it is an ammonium tetrafluoroborate solution; the concentration of the solute in the boron-containing solution is 1 - 2.5 mol / L, specifically 1.5 - 2 mol / L in specific embodiments.

[0055] In the present invention, ammonium nitrate solution is selected to simultaneously provide two nitrogen sources of anions and cations, thereby obtaining a high-concentration nitrogen-doped material; potassium fluoride solution is selected to obtain a relatively high fluorine doping amount without introducing other heteroatoms; ammonium tetrafluoroborate solution has a high B doping amount and forms multiple doping types; thiosulfate and sulfite can form S-C bonds instead of C-SOx.

[0056] As an embodiment, the parameters of the redox reaction are: the temperature is room temperature, specifically 15-25 °C in specific embodiments, the initial voltage is set to 0-1 V, specifically 0 V in specific embodiments, the maximum voltage is set to 1.5-3 V, specifically 1.7-2.5 V in specific embodiments, the minimum voltage is set to -1.2 to -0.8 V, specifically -1.2 to -1.0 V in specific embodiments, the scanning speed is 0.02-0.05 V / s, specifically 0.03-0.04 V / s in specific embodiments, the number of scanning cycles is 50-300 cycles, specifically 100-200 cycles in specific embodiments, and the current density is 5-200 mA / cm 2 , specifically 10-100 mA / cm 2 。

[0057] The carbon material is converted into a heteroatom-doped reduced graphene oxide material through ion intercalation, oxidation, and reduction. During this process, as the positive overpotential increases, first the carbon material is oxidized to form oxygen-containing functional groups such as hydroxyl, epoxy, and carboxyl groups at the edges, and at the same time, the interlayer spacing gradually opens under the action of hydrolysis bubbles. Then, heteroatoms are inserted into the interlayer and adsorbed on the oxygen-containing functional groups or planes through electrostatic attraction, cation-π, hydrogen bonding, etc., while dehydrogenating. When the scanning potential is reversed, as the negative overpotential increases, the oxygen-containing functional groups adsorbed with heteroatoms are reduced and hydrogenated, enabling the heteroatoms to be embedded in the lattice of the carbon material, thereby endowing the material with high electrochemical performance and catalytic activity.

[0058] The parameters of the redox reaction mainly affect the oxidation and reduction degree of the carbon material, the intercalation and hydrolysis degree of heteroatom-containing ions, and the doping type. Generally, the wider the voltage range and the slower the scanning speed, the more beneficial it is to generate more defect sites and improve the electrochemical activity of the carbon material.

[0059] Within a certain range, the smaller the current density and the higher the positive overpotential, the more beneficial it is for the heteroatom-containing ions to slowly intercalate into the graphite interlayer, generate more oxygen-containing functional groups, and produce more defects during reduction and deoxidation for heteroatom doping; the heteroatoms with different ion types in the heteroatom-containing solution are beneficial to increasing the concentration of heteroatom doping. The control of these conditions is beneficial to changing the electronic structure of graphene, adjusting the bandgap width, creating more electron donor and electron acceptor sites, increasing the electrochemical activity and conductivity of the heteroatom-doped reduced graphene oxide material, and thus improving the efficiency of its catalytic reaction.

[0060] Compared with the constant voltage electrochemical exfoliation technology, the cyclic voltammetry method adopted in the present invention can achieve precise regulation of heteroatom doping by flexibly controlling the redox environment. This method can realize the preparation of thin-film graphene-like materials in one step, and is more suitable as an electrode material for electrochemical sensing without secondary treatment.

[0061] In terms of the preparation method, the present invention has the advantages of low cost, mild reaction conditions, high sensitivity, convenience, simplicity, environmental friendliness, strong controllability, no side reactions, and is suitable for large-scale production; in terms of application prospects, it is expected that the present invention can conduct sensing monitoring on an electrochemical workstation through the electron transfer and binding of active sites occurring on its surface by pollutants, so as to precisely monitor new pollutants. At the same time, by adjusting parameters such as current density, voltage, composition of the doping solution (solution containing heteroatoms), and temperature, the microstructures such as the interlayer spacing of carbon materials, heteroatom doping amount, functional group structure, and defects can be precisely controlled.

[0062] The present invention also provides a heteroatom-doped reduced graphene oxide material prepared by the preparation method described in the above technical solution, including reduced graphene oxide and heteroatoms doped on the surface and between the layers of the reduced graphene oxide;

[0063] The heteroatoms include one or more of nitrogen atoms, fluorine atoms, sulfur atoms, and boron atoms;

[0064] The nitrogen atoms are doped in the form of pyridine nitrogen, pyrrole nitrogen, or graphitic nitrogen. The pyridine nitrogen or pyrrole nitrogen is formed by the nitrogen atoms and carbon atoms in the reduced graphene oxide. The boron atoms are doped in the form of substituting carbon atoms. The sulfur atoms are doped by forming S-C covalent bonds, and the fluorine atoms are doped by forming C-F covalent bonds.

[0065] As an implementation mode, the heteroatoms are nitrogen atoms, fluorine atoms, sulfur atoms, or boron atoms; the C-F covalent bonds include ionic C-F bonds and semi-ionic C-F bonds.

[0066] As an implementation mode, the mass percentage content of heteroatoms in the heteroatom-doped reduced graphene oxide material is 1-5%, specifically 2.39%, 1.17%, or 1% in specific embodiments, and the mass percentage content of reduced graphene oxide is 95-99%, specifically 97.61%, 98.83%, or 99% in specific embodiments.

[0067] Heteroatom doping changes the electronic structure of carbon materials, effectively improving their electrochemical performance, enhancing electrical conductivity, improving surface wettability, and can also provide more active sites to improve their catalytic activity. Among them, nitrogen atom doping can increase the free electron density in reduced graphene oxide materials, improve their electrocatalytic activity, electrical conductivity and surface wettability. Nitrogen usually exists in the forms of pyridine nitrogen, pyrrole nitrogen and graphitic nitrogen. Boron doping will cause holes to appear in the carbon lattice, enhancing the p-type semiconductor characteristics of carbon materials and improving their mechanical strength and thermal stability. Boron mainly exists in carbon materials in the form of substituting carbon atoms. Sulfur doping helps to improve the lithium storage capacity, capacitance performance and redox activity of carbon materials, and is suitable for supercapacitor and battery electrode materials. Sulfur is doped by forming covalent bonds with carbon materials. Fluorine doping can change the surface chemical properties of carbon materials, making them more hydrophobic, and may improve the antioxidant and corrosion resistance of the materials. Fluorine is also doped by forming covalent bonds with carbon materials.

[0068] The present invention also provides the application of the heteroatom-doped reduced graphene oxide material described in the above technical solution in an electrode.

[0069] As an implementation manner, the electrode includes one or several of an electrochemical sensing electrode, an energy storage electrode and an electrolysis electrode, and is specifically an electrochemical sensing electrode in a specific embodiment.

[0070] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention, but they cannot be understood as limiting the protection scope of the present invention.

[0071] Example 1

[0072] An electrochemical reaction device was constructed using graphite paper as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. First, cyclic voltammetry was adopted, and 1 mol / L sodium sulfate solution was used for pre-oxidation treatment: the temperature was 25 °C, the initial voltage was set to 0 V, the highest voltage was set to 2 V, the lowest voltage was set to 0 V, and the scanning speed was 0.05 V / s, and the current density was 10 mA / cm 2 , after 10 cycles of pre-oxidation treatment, cyclic voltammetry was continued for redox reaction. 2.5 mol / L ammonium nitrate solution was selected as the doping solution to dope N atoms. The temperature was 25 °C, the initial voltage was set to 0 V, the highest voltage was set to 2.1 V, the lowest voltage was set to -1.2 V, the scanning speed was 0.05 V / s, and the current density was 5 mA / cm 2 . After 100 cycles of cyclic scanning, a nitrogen atom-doped reduced graphene oxide material was obtained.

[0073] Example 2

[0074] The difference from Example 1 is that a 1 mol / L potassium fluoride solution is selected as the doping solution to dope F atoms. In the pre-oxidation treatment, the maximum voltage is set to 2.5 V, the scanning speed is 0.1 V / s, and the number of scanning cycles is 75. During the redox reaction process, the maximum voltage is set to 1.9 V, and the minimum voltage is set to -1.2 V. The remaining assembly steps are the same as those in Example 1, and a fluorine atom-doped reduced graphene oxide material is obtained.

[0075] Example 3

[0076] The difference from Example 1 is that a 1.5 mol / L ammonium tetrafluoroborate solution is selected as the doping solution to dope B atoms. In the pre-oxidation treatment, the maximum voltage is set to 2 V. During the redox reaction process, the maximum voltage is set to 1.7 V, and the minimum voltage is set to -1.2 V. The remaining assembly steps are the same as those in Example 1, and a boron atom-doped reduced graphene oxide material is obtained.

[0077] Example 4

[0078] The difference from Example 1 is that a 1.25 mol / L sodium thiosulfate solution is selected as the doping solution to dope S atoms. In the pre-oxidation treatment, the maximum voltage is set to 2 V. During the redox reaction process, the maximum voltage is set to 1.7 V, and the minimum voltage is set to -1.2 V. The remaining assembly steps are the same as those in Example 1, and a sulfur atom-doped reduced graphene oxide material is obtained.

[0079] Comparative Example 1

[0080] An electrochemical reaction device is constructed using a graphite rod as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. Ethylammonium nitrate containing 10% (v / v) water is selected as the electrolyte. The constant voltage method is adopted, and electrolysis is carried out at 25 °C and a voltage of 2.2 V for 20 min until complete exfoliation. Finally, nitrogen-doped graphene oxide is obtained.

[0081] Comparative Example 2

[0082] An electrochemical reaction device is constructed using a graphite rod as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. A 1.5 mol / L ammonium sulfate solution is selected as the electrolyte. The constant current method is adopted, and electrolysis is carried out at 25 °C and a static current of 1.0 A for 2 h until complete exfoliation. Finally, sulfur-doped graphene oxide is obtained.

[0083] Comparative Example 3

[0084] The electrochemical deposition method constructs an electrochemical reaction device with a conductive material as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. An acid ionic liquid solution treated by deoxidation is used as the electrolyte, and the doping object, graphene oxide, exists in a colloidal state therein. An electrolytic reduction reaction is carried out at a constant potential of -1.0 V, and finally, nitrogen-doped reduced graphene oxide in-situ loaded on the conductive material is obtained. In comparison, the present invention has two advantages. One is that the doping object is a solid carbon material, without the need for a conductive material, directly targeting the structural regulation of the solid electrode material, without subsequent treatment, and has good stability. The other is that the defect regulation is more precise, and the required doping type is regulated through cyclic oxidation and reduction.

[0085] Performance test

[0086] (1) Figure 1 It is the CV curve diagram of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1.

[0087] From Figure 1 it can be seen that in cyclic voltammetry, when the current is positive, the rising curve indicates that the electrode undergoes an oxidation reaction and nitrate ions are embedded between layers. When the current is negative, a reduction reaction and the embedding of ammonium ions occur. Two reduction peaks appear, respectively representing the reduction of nitrate and graphene oxide. After 100 cycles, a nitrogen atom-doped reduced graphene oxide material is formed.

[0088] (2) Figure 2 It is the XPS diagram of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1.

[0089] From Figure 2 it can be seen that XPS testing can illustrate the type of N element doping. Two types of N doping are formed in the nitrogen atom-doped reduced graphene oxide material, among which graphitic nitrogen accounts for 45.88% and pyrrolic nitrogen accounts for 54.12%, indicating that the method successfully incorporates N atoms into the carbon material.

[0090] (3) Figure 3 It is the CV curve diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2.

[0091] From Figure 3 it can be seen that in cyclic voltammetry, when the current is positive, the rising curve indicates that the electrode undergoes an oxidation reaction and fluoride ions are embedded between layers. When the current is negative, a reduction reaction occurs. Two reduction peaks appear, respectively representing fluoride ion doping and the reduction of graphene oxide. After 100 cycles, a fluorine atom-doped reduced graphene oxide material is formed.

[0092] (4) Figure 4 It is the XPS diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2.

[0093] FromFigure 4 It can be seen that two peaks regarding C-F can be obtained from the XPS image, which is consistent with the conclusion of F doping obtained by referring to the literature. The ionic C-F bond accounts for 60.29% and the semi-ionic C-F bond accounts for 39.71%. In summary, it shows that the method has successfully incorporated F atoms into the carbon material.

[0094] (5) Figure 5 It is the CV curve graph of the boron atom-doped reduced graphene oxide material prepared in Example 3.

[0095] From Figure 5 it can be seen that in cyclic voltammetry, when the current is positive, the rising curve indicates that the electrode undergoes an oxidation reaction and the tetrafluoroborate ions are embedded between the layers. When the current is negative, the falling curve indicates that the material undergoes a reduction reaction. After 100 cycles, the boron atom-doped reduced graphene oxide material is formed.

[0096] (6) Figure 6 It is the XPS graph of the boron atom-doped reduced graphene oxide material prepared in Example 3.

[0097] From Figure 6 it can be seen that the XPS test can illustrate the type of B element doping. Two types of B doping are formed in the boron atom-doped reduced graphene oxide material, among which BCO 2 contains 82.06% and BC 2 O contains 17.94%, indicating that the method has successfully incorporated B atoms into the carbon material.

[0098] (7) Figure 7 It is the CV curve graph of the sulfur atom-doped reduced graphene oxide material prepared in Example 4.

[0099] From Figure 7 it can be seen that in cyclic voltammetry, when the current is positive, the rising curve indicates that the electrode undergoes an oxidation reaction and the thiosulfate ions are embedded between the layers. When the current is negative, the falling curve indicates that the material and the thiosulfate undergo a reduction reaction. After 100 cycles, the S-doped graphene material is formed.

[0100] (8) Figure 8 It is the XPS graph of the sulfur atom-doped reduced graphene oxide material prepared in Example 4.

[0101] From Figure 8 it can be seen that the XPS test can illustrate the type of S element doping. Two types of S doping are formed in the sulfur atom-doped reduced graphene oxide material, among which C-S-C accounts for 43.65% and C-SOx accounts for 56.35%, indicating that the method has successfully incorporated S atoms into the carbon material.

[0102] (9) Raman, XRD, and XPS tests were carried out on the nitrogen-doped graphene oxide prepared in Comparative Example 1, and the results are asFigure 9 As shown, where (a) is the Raman test graph, (b) is the XRD test graph, (c) is the XPS total spectrum graph, and (d) is the N-doping spectrum graph of XPS.

[0103] From Figure 9 It can be seen from (a), (b), (c) and (d) in that, it shows that nitrogen-doped graphene oxide was formed in Comparative Example 1. The main difference is that the material prepared in Example 1 is in the form of a thin film, which is more conducive to being used as an electrode material and does not require secondary treatment, while the material prepared in Comparative Example 1 is in the form of powder. Moreover, Comparative Example 1 uses a constant voltage method to continuously oxidize to obtain exfoliated graphene oxide powder, and the degree of doping and oxidation is uncontrollable. In contrast, Example 1 applies cyclic forward and reverse voltages, and graphite is repeatedly oxidized and reduced to form a thin film-like graphene. This process can accurately control the doping type, promote electron transfer by utilizing the abundant defect sites on the surface while maintaining good conductivity, and quickly identify pollutants.

[0104] (10) XPS test was carried out on the sulfur-doped graphene oxide prepared in Comparative Example 2, and the results are as Figure 10 shown, where a is the S-doping spectrum graph of XPS and b is the N-doping spectrum graph of XPS.

[0105] From Figure 10 It can be seen from a and b in that, it shows that S / N co-doped graphene oxide was formed in Comparative Example 2. In Example 4, C-S-C type doping can be formed, which can better change the electronic structure of carbon nanomaterials, adjust the band gap structure, form electron donor and electron acceptor sites, and improve the catalytic ability of the material.

[0106] (11) Figures 11 to 13 They are the Mott-Schottky curve graphs of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1, the boron atom-doped reduced graphene oxide material prepared in Example 3, and the sulfur atom-doped reduced graphene oxide material prepared in Example 4, respectively.

[0107] From Figures 11 to 13 it can be seen that this test technology can show the semiconductor types of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1, the boron atom-doped reduced graphene oxide material prepared in Example 3, and the sulfur atom-doped reduced graphene oxide material prepared in Example 4, which are n-type, p-type, and p-type respectively, and the flat band potentials are -0.287 eV, 0.792 eV, and 0.796 eV respectively: This parameter is closely related to the Fermi level position of the material and is a key index for evaluating the energy band structure of semiconductors in electrolytes.

[0108] (12) Figure 14 It is the original data graph of the Tafel curve test of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1, Figure 15Fitting diagram of the Tafel curve test for the nitrogen atom-doped reduced graphene oxide material prepared in Example 1. This test uses a three-electrode system, the scanning voltage range is 0 - 100 mV, the electrolyte is pure water or tetracycline, the scanning speed is 1 mV / s. DL+NGO refers to using the nitrogen atom-doped reduced graphene oxide material prepared in Example 1 as the working electrode and pure water as the electrolyte for the Tafel test; TC+NGO refers to using the nitrogen atom-doped reduced graphene oxide material prepared in Example 1 as the working electrode and tetracycline as the electrolyte for the Tafel test; TC+NGO (adsorbed saturated PMS) refers to using the nitrogen atom-doped reduced graphene oxide material prepared in Example 1 that has fully adsorbed PMS as the working electrode and tetracycline as the electrolyte for the Tafel test. Then, by fitting the linear part (60 mV - 80 mV) of the Tafel curve, we get Figure 15 。

[0109] From Figure 14 and Figure 15 it can be seen that this test is to verify the ability of the prepared material to activate persulfate and transfer electrons with the new pollutant antibiotic. From the fitted quadratic function, it can be seen that the slope of the blue curve is the largest, indicating that the material has strong electron transfer ability and good catalytic activity.

[0110] (13) Figure 16 Electrochemical impedance (EIS) test diagram of the fluorine atom-doped reduced graphene oxide material prepared in Example 2. The diameter of the semicircle in the middle frequency region corresponds to the charge transfer resistance Rct. From Figure 16 it can be seen that the measured diameter is small, indicating that the material has a small resistance and good conductivity.

[0111] (14) Figure 17 CV test diagram of the nitrogen-doped graphene oxide prepared in Comparative Example 1. Figure 18 CV test diagram of the sulfur-doped graphene oxide prepared in Comparative Example 2.

[0112] From Figure 17 、 Figure 18 it can be seen that by comparing the CV test diagram of the nitrogen-doped graphene oxide prepared in Comparative Example 1 with that of the nitrogen atom-doped reduced graphene oxide material prepared in Example 1 ( Figure 1 ), and comparing the CV test diagram of the sulfur-doped graphene oxide prepared in Comparative Example 2 with the CV curve diagram of the sulfur atom-doped reduced graphene oxide material prepared in Example 4 ( Figure 7 ), the heteroatom-doped reduced graphene oxide material prepared in the present invention can withstand a wider scanning voltage range and more scanning cycles, indicating that the heteroatom-doped reduced graphene oxide material prepared in the present invention has better stability.

[0113] Although the above embodiments have described the present invention in detail, they are only a part rather than all of the embodiments of the present invention. People can also obtain other embodiments based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing heteroatom-doped reduced graphene oxide material, characterized in that: The following steps are involved: Using cyclic voltammetry, the working electrode was pre-oxidized in a sulfate solution; performing a redox reaction on the pre-oxidized working electrode in a solution containing heteroatoms to obtain a heteroatom-doped reduced graphene oxide material; The working electrode is a carbon material; The heteroatom includes one or more of a nitrogen atom, a fluorine atom, a sulfur atom and a boron atom.

2. The preparation method according to claim 1, characterized in that: The carbon material is one or more of graphite paper, graphite rod, carbon paper and carbon brush.

3. The preparation method according to claim 1, characterized in that: The heteroatom-containing solution is one or more of a nitrogen-containing solution, a fluorine-containing solution, a sulfur-containing solution and a boron-containing solution; the concentration of the solute in the nitrogen-containing solution is 1.5 to 2.5 mol / L; the concentration of the solute in the fluorine-containing solution is 1 to 2.5 mol / L; the concentration of the solute in the sulfur-containing solution is 1 to 2.5 mol / L; the concentration of the solute in the boron-containing solution is 1 to 2.5 mol / L.

4. The preparation method according to claim 1 or 3, characterized in that: The nitrogen-containing solution is one or more of ammonium nitrate solution, nitric acid solution, sodium nitrate solution, ammonium sulfate solution, ammonia solution and imidazole-based ionic liquid solution; the fluorine-containing solution is potassium fluoride solution and / or ammonium tetrafluoroborate solution; The sulfur-containing solution is a thiosulfate solution and / or a sulfite solution; The boron-containing solution is one or more of an ammonium tetrafluoroborate solution, a tetrafluoroborate ion liquid solution, a boric acid solution and a sodium borohydride solution.

5. The preparation method according to claim 1, characterized in that: The sulfate is one or more of sodium sulfate, potassium sulfate and magnesium sulfate; the concentration of the sulfate in the sulfate solution is 0.5-1.5 mol / L.

6. The preparation method according to claim 1 or 5, characterized in that: The parameters of the pre-oxidation treatment are: room temperature, initial voltage of 0-1V, maximum voltage of 1.5-2.5V, minimum voltage of 0-1V, scanning speed of 0.02-0.1V / s, number of scanning circles of 10-100 circles, current density of 5-200mA / cm 2 .

7. The preparation method according to claim 1 or 3, characterized in that: The parameters of the redox reaction are: room temperature, initial voltage of 0-1V, maximum voltage of 1.5-3V, minimum voltage of -1.2-0.8V, scanning speed of 0.02-0.05V / s, number of scanning circles of 50-300 circles, current density of 5-200mA / cm 2 .

8. The preparation method according to claim 1, characterized in that: The cyclic voltammetry is performed using a three-electrode system; in the three-electrode system, the counter electrode is a platinum wire or a platinum sheet, and the reference electrode is an Ag / AgCl electrode or a calomel electrode.

9. The heteroatom-doped reduced graphene oxide material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: It includes reduced graphene oxide and heteroatoms doped on the surface and interlayers of the reduced graphene oxide; The heteroatom includes one or more of a nitrogen atom, a fluorine atom, a sulfur atom and a boron atom; The nitrogen atoms are doped in the form of pyridinic nitrogen, pyrrolic nitrogen or graphitic nitrogen, wherein the pyridinic nitrogen or pyrrolic nitrogen is formed by nitrogen atoms and carbon atoms in the reduced graphene oxide, the boron atoms are doped in the form of replacing carbon atoms, the sulfur atoms are doped in the form of forming SC covalent bonds, and the fluorine atoms are doped in the form of forming CF covalent bonds.

10. The use of the heteroatom-doped reduced graphene oxide material according to claim 9 in an electrode, characterized in that: The electrodes include one or more of electrochemical sensing electrodes, energy storage electrodes and electrolysis electrodes.

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