Preparation method of high dispersibility graphene oxide

Abstract

The application relates to the field of graphene materials, in particular to a preparation method of high-dispersity graphene oxide. The preparation method comprises the following steps: mixing graphite, concentrated sulfuric acid and hydrogen peroxide to obtain expanded graphite; and electrochemically exfoliating the expanded graphite to obtain the high-dispersity graphene oxide; wherein an electrolyte used in the electrochemical exfoliation process comprises an amino modifier. The preparation method synchronously carries out electrochemical exfoliation and graft modification of the graphene oxide by adding the amino modifier in the electrolyte, so that the high-dispersity graphene oxide is obtained, and the preparation method is simple in operation, low in cost, high in efficiency and easy to control.

Description

Technical Field

[0001] This invention relates to the field of graphene materials, and more particularly to a method for preparing highly dispersed graphene oxide. Background Technology

[0002] Graphene is a unique two-dimensional material with excellent mechanical, thermal, electrical, and chemical stability properties, making it widely used in novel composite materials, optoelectronic materials, and biosensors. However, the unique π-π conjugation and van der Waals forces in graphene cause its sheets to easily aggregate and stack, making uniform dispersion in solution difficult and limiting its effective applications. Graphene oxide (GO), a derivative of graphene, has a quasi-two-dimensional layered structure containing numerous oxygen-containing functional groups such as hydroxyl, carboxyl, and epoxy groups, exhibiting strong hydrophilicity and allowing for uniform dispersion in water. Electrochemically exfoliated graphene has a lower degree of oxidation, posing a challenge to its uniform dispersion in aqueous solutions.

[0003] Therefore, improving the dispersibility of electrochemically prepared graphene oxide is crucial for expanding its applications. Extensive research has been conducted on improving the dispersibility of graphene oxide through complex physical methods or chemical modification. However, existing preparation and modification processes involve complex steps such as separation, stirring, hydrothermal treatment, and secondary ultrasonication, resulting in low efficiency, high cost, and difficulty in controlling the degree of modification and grafting.

[0004] Therefore, there is an urgent need to provide a simple and efficient electrochemical preparation method for highly dispersible graphene oxide. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, this invention provides a method for preparing highly dispersible graphene oxide. By electrochemically exfoliating expanded graphite and adding an amino modifier to the electrolyte, the preparation and modification of graphene oxide are carried out simultaneously, thereby obtaining a highly dispersible graphene oxide. This preparation method is simple to operate, low in cost, highly efficient, and easy to control.

[0006] Therefore, the present invention provides a method for preparing highly dispersible graphene oxide, comprising:

[0007] (1) Mix graphite, concentrated sulfuric acid and hydrogen peroxide to obtain expanded graphite;

[0008] (2) Electrochemically exfoliate the expanded graphite to obtain the highly dispersed graphene oxide;

[0009] The electrolyte used in the electrochemical stripping process includes an amino modifier.

[0010] During the research, the inventors discovered that increasing the current density of the electrodes during the electrochemical exfoliation process for graphene preparation is beneficial for obtaining graphene with smaller flake diameters, thereby increasing the degree of oxidation at the graphene edges and improving its dispersibility. The degree of close contact between graphite particles is the main factor limiting the current density. This invention obtains a highly cross-linked expanded graphite stack by mixing graphite, concentrated sulfuric acid, and hydrogen peroxide, increasing the close contact between graphite particles. This facilitates obtaining a higher current density during the subsequent electrochemical exfoliation process, promoting the production of small-diameter graphene oxide flakes. Simultaneously, using an electrolyte containing an amino-modifying agent during the electrochemical exfoliation process allows for the grafting of functional groups onto the graphene surface, enhancing the electrostatic repulsion between graphene particles and significantly improving the dispersibility of the electrochemically exfoliated graphene oxide.

[0011] According to embodiments of the present invention, the graphite includes at least one of natural flake graphite, microcrystalline graphite, artificial graphite, and Kish graphite.

[0012] According to an embodiment of the present invention, the electrolyte in step (2) further includes at least one of inorganic acid and inorganic salt.

[0013] According to embodiments of the present invention, the inorganic acid includes at least one selected from sulfuric acid, hydrochloric acid, and phosphoric acid.

[0014] According to an embodiment of the present invention, the inorganic salt includes at least one selected from ammonium sulfate, sodium sulfate, potassium sulfate, and sodium chloride.

[0015] According to an embodiment of the present invention, the concentration of the inorganic acid and / or inorganic salt is 0.1 mol / L to 1 mol / L.

[0016] According to embodiments of the present invention, the amino modifier includes at least one selected from 2-aminobenzamide, 3,5-diaminobenzoic acid, polyaniline, and 3,5-diaminobenzenesulfonic acid.

[0017] According to an embodiment of the present invention, the concentration of the amino modifier in step (2) is 0 to 0.5 mol / L and is not 0 mol / L.

[0018] According to an embodiment of the present invention, step (2) further includes:

[0019] The temperature of the electrolyte is controlled to be between 0 and 90°C.

[0020] According to an embodiment of the present invention, the voltage applied during the electrochemical stripping process is in the range of 5V to 20V.

[0021] According to an embodiment of the present invention, the electrochemical stripping time is 15 min to 120 min.

[0022] The advantages of this invention over the prior art are:

[0023] This invention provides an electrochemical method for preparing highly dispersed graphene oxide. The method increases the cross-linking degree between graphite particles by preparing expanded graphite aggregates, and then combines this with electrochemical exfoliation to obtain highly dispersed graphene oxide with small flake size. This preparation method eliminates the need to remove sulfuric acid before electrochemical exfoliation, and the preparation and modification of graphene oxide are carried out simultaneously, reducing intermediate steps and lowering environmental pollution, production costs, and energy consumption.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 The Zeta potential distribution curve of the graphene oxide dispersion prepared in Example 1 of this invention is shown.

[0027] Figure 2 The Zeta potential distribution curve of the graphene oxide dispersion prepared in Comparative Example 1 of this invention is shown.

[0028] Figure 3 The Zeta potential distribution curve of the graphene oxide dispersion prepared in Comparative Example 2 of this invention is shown.

[0029] Figure 4 The Zeta potential distribution curve of the graphene oxide dispersion prepared in Comparative Example 3 of this invention is shown.

[0030] Figure 5 Optical photographs of the graphene oxide dispersions prepared according to the present invention after standing for 30 days are shown, wherein: Figure a is an optical photograph of the graphene oxide dispersion prepared in Example 1 after standing for 30 days; Figure b is an optical photograph of the graphene oxide dispersion prepared in Comparative Example 1 after standing for 30 days; Figure c is an optical photograph of the graphene oxide dispersion prepared in Comparative Example 2 after standing for 30 days; and Figure d is an optical photograph of the graphene oxide dispersion prepared in Comparative Example 3 after standing for 30 days. Detailed Implementation

[0031] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0036] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0037] According to embodiments of the present invention, a method for preparing highly dispersed graphene oxide is provided, comprising:

[0038] (1) Mix graphite, concentrated sulfuric acid and hydrogen peroxide to obtain expanded graphite.

[0039] In this step, hydrogen peroxide oxidizes the graphite edges, promoting the intercalation of graphite by concentrated sulfuric acid. At the same time, hydrogen peroxide is introduced into the graphite interlayer along with sulfuric acid, and the expansion of graphite is increased under the impetus of oxygen generated by decomposition, thereby obtaining a highly cross-linked expanded graphite stack. This improves the tightness of the contact between graphite particles, thereby obtaining a higher current density during the electrochemical exfoliation process to promote the production of small-diameter graphene oxide flakes.

[0040] According to specific embodiments of the present invention, the type of graphite is not particularly limited. As some specific examples, the graphite includes, but is not limited to, natural flake graphite, microcrystalline graphite, artificial graphite, and Kish graphite.

[0041] According to a specific embodiment of the present invention, expanded graphite can be prepared by mixing graphite, concentrated sulfuric acid and hydrogen peroxide evenly under ice bath conditions, transferring the mixture to a fixed volume container, and allowing it to stand at room temperature to obtain a highly cross-linked expanded graphite stack.

[0042] (2) Electrochemically exfoliate the expanded graphite to obtain the highly dispersed graphene oxide;

[0043] The electrolyte used in the electrochemical stripping process includes an amino modifier.

[0044] In this step, the amino modifier can graft functional groups onto the surface of graphene oxide, and the electrochemical exfoliation of graphene oxide and graft modification can be carried out simultaneously, which improves the electrostatic repulsion between graphene oxides and thus significantly improves the dispersibility of electrochemically exfoliated graphene oxide.

[0045] According to specific embodiments of the present invention, the type of electrolyte in step (2) is not particularly limited. As some specific examples, the electrolyte includes, but is not limited to, at least one of inorganic acids and inorganic salts.

[0046] According to specific embodiments of the present invention, the type of inorganic acid is not particularly limited. As some specific examples, the inorganic acid includes, but is not limited to, at least one of sulfuric acid, hydrochloric acid, and phosphoric acid.

[0047] According to specific embodiments of the present invention, the type of inorganic salt is not particularly limited. As some specific examples, the inorganic salt includes, but is not limited to, at least one of ammonium sulfate, sodium sulfate, potassium sulfate, and sodium chloride.

[0048] According to specific embodiments of the present invention, the concentration of the inorganic acid and / or inorganic salt is 0.1 mol / L to 1 mol / L. As some specific examples, the concentration of the inorganic acid and / or inorganic salt may be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, etc.

[0049] According to specific embodiments of the present invention, the type of amino modifier is not particularly limited. As some specific examples, the amino modifier includes, but is not limited to, at least one of 2-aminobenzamide, 3,5-diaminobenzoic acid, polyaniline, and 3,5-diaminobenzenesulfonic acid.

[0050] According to specific embodiments of the present invention, the concentration of the amino modifier is 0 to 0.5 mol / L and is not 0 mol / L. As some specific examples, the concentration of the amino modifier may be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0051] In this invention, when ammonium sulfate or other electrolytes as described above are selected, the expanded graphite in the fixed-volume container does not need to undergo a desulfurization process; it can be exfoliated immediately after the electrode is inserted through the opening. The air bubbles generated during the exfoliation process act as a disturbance, increasing the contact probability between the graphene and the modifier. Furthermore, the heat generated during the electrochemical exfoliation process can also accelerate the reaction rate of the modifier on the graphene surface, improving the grafting modification of functional groups on the graphene surface, thereby further enhancing the dispersibility of graphene oxide.

[0052] According to a specific embodiment of the present invention, step (2) can be specifically operated by making a small hole in the container and inserting a platinum wire as the electrochemical anode and another platinum wire as the cathode, immersing it in an electrolyte containing an amino modifier, applying an external voltage for electrochemical stripping, and separating the reaction products after electrolysis to obtain highly dispersed graphene oxide. According to a specific embodiment of the present invention, step (2) further includes:

[0053] The temperature of the electrolyte is controlled to be between 0 and 90°C. As some specific examples, the temperature of the electrolyte can be 0°C, 30°C, 60°C, 90°C, etc.

[0054] By controlling the temperature of the electrolyte, the solubility of different amino modifiers in water can be increased, thereby promoting the grafting modification reaction, increasing the electrostatic repulsion between graphenes, and thus significantly improving the dispersibility of electrochemically exfoliated graphene oxide.

[0055] According to specific embodiments of the present invention, the voltage applied during the electrochemical stripping process is in the range of 5V to 20V. As some specific examples, the voltage applied during the electrochemical stripping process may be 5V, 10V, 15V, 20V, etc.

[0056] According to specific embodiments of the present invention, the electrochemical stripping time is 15 min to 120 min. As some specific examples, the electrochemical stripping time can be 15 min, 30 min, 60 min, 90 min, 120 min, etc.

[0057] According to specific embodiments of the present invention, the method for separating graphene oxide after electrochemical exfoliation is not particularly limited. As some specific examples, the separation method includes, but is not limited to, at least one of filtration, centrifugation, and dialysis.

[0058] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0059] Example 1

[0060] (1) Under ice bath conditions, 0.5g of natural flake graphite (100 mesh) was mixed evenly with 7mL of concentrated sulfuric acid and 3.6mL of hydrogen peroxide, transferred to a fixed volume container, and left to stand at room temperature for 4h to obtain cross-linked worm-like expanded graphite.

[0061] (2) Make a 2 mm hole in the container and insert a platinum wire as the electrochemical anode and another platinum wire as the cathode. The electrode spacing is 2 cm. The electrolyte is 0.5 mol / L ammonium sulfate and the amino modifier is 0.1 mol / L 2-aminobenzamide. Control the electrolyte temperature at 30℃, apply an external voltage of 10V, and electrolyze for 60 min. Filter and wash the reaction product until it is neutral (pH = 6-7). Sonicate it at 500W for 30 min and centrifuge it at 3000 r / min for 10 min to remove the thicker graphene particles to obtain highly dispersed graphene oxide.

[0062] The zeta potential of the highly dispersed graphene oxide prepared according to the above process was measured as follows: Figure 1 As shown, the optical photographs taken after it has been left to stand for 30 days are as follows: Figure 5 As shown in Figure a, the Zeta potential values ​​are shown in Table 1. As can be seen from the figure, the graphene oxide prepared in this embodiment does not settle after standing for several days, exhibits a high absolute value of zeta potential, and has excellent dispersibility.

[0063] Example 2

[0064] (1) Under ice bath conditions, 0.5g of natural flake graphite (100 mesh) was mixed evenly with 7mL of concentrated sulfuric acid and 3.6mL of hydrogen peroxide, transferred to a fixed volume container, and left to stand at room temperature for 4h to obtain cross-linked worm-like expanded graphite.

[0065] (2) Make a 2 mm hole in the container and insert a platinum wire as the electrochemical anode and another platinum wire as the cathode. The electrode spacing is 2 cm. The electrolyte is 0.5 mol / L ammonium sulfate and the amino modifier is 0.1 mol / L polyaniline. Control the electrolyte temperature at 30℃, apply an external voltage of 12V, and electrolyze for 30 min. Filter and wash the reaction product until it is neutral (pH = 6-7). Sonicate it at 500W for 30 min. Centrifuge it at 3000 r / min for 10 min to remove the thicker graphene particles to obtain highly dispersed graphene oxide.

[0066] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0067] Example 3

[0068] (1) Under ice bath conditions, 0.5g of natural flake graphite (100 mesh) was mixed evenly with 7mL of concentrated sulfuric acid and 3.6mL of hydrogen peroxide, transferred to a fixed volume container, and left to stand at room temperature for 4h to obtain cross-linked worm-like expanded graphite.

[0069] (2) Make a 2 mm hole in the container and insert a platinum wire as the electrochemical anode and another platinum wire as the cathode. The electrode spacing is 2 cm. The electrolyte is 0.5 mol / L ammonium sulfate and the amino modifier is 0.5 mol / L 2-aminobenzamide. Control the electrolyte temperature at 30 °C, apply an external voltage of 8 V, and electrolyze for 90 min. Use a dialysis bag with a molecular weight of 500 to separate the reaction products and obtain highly dispersed graphene oxide.

[0070] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0071] Example 4

[0072] The preparation method in this embodiment is the same as that in Example 1, except that the graphite raw material used in this embodiment is Kish graphite.

[0073] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0074] Example 5

[0075] The preparation method in this embodiment is the same as that in Example 1, except that the electrolyte temperature is controlled at 0°C in this embodiment.

[0076] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0077] Example 6

[0078] The preparation method in this embodiment is the same as that in Example 1, except that the electrolyte temperature is controlled at 60°C in this embodiment.

[0079] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0080] Example 7

[0081] The preparation method in this embodiment is the same as that in Example 1, except that the electrolyte temperature is controlled at 90°C in this embodiment.

[0082] The Zeta potential values ​​of the highly dispersed graphene oxide prepared according to the above process are shown in Table 1.

[0083] Comparative Example 1

[0084] (1) Under ice bath conditions, 0.5g of natural flake graphite (100 mesh) was mixed evenly with 7mL of concentrated sulfuric acid and 3.6mL of hydrogen peroxide, transferred to a fixed volume container, and left to stand at room temperature for 4h to obtain cross-linked worm-like expanded graphite.

[0085] (2) Make a 2 mm hole in the container, insert a platinum wire as the electrochemical anode, and another platinum wire as the cathode. The electrode spacing is 2 cm. The electrolyte is 0.5 mol / L ammonium sulfate. Control the electrolyte temperature at 30 °C. Apply an external voltage of 10 V and electrolyze for 30 min. Filter and wash the reaction product until it is neutral (pH = 6-7). Sonicate it at 500 W for 30 min. Centrifuge it at 3000 r / min for 10 min to remove the thicker graphene particles to obtain highly dispersed graphene oxide.

[0086] The zeta potential of the graphene oxide prepared according to the above process flow was measured as follows: Figure 2 As shown, the optical photographs taken after it has been left to stand for 30 days are as follows: Figure 5 As shown in b, the Zeta potential values ​​are shown in Table 1. As can be seen from the figure, the graphene oxide prepared in Comparative Example 1 has poor dispersibility; after standing for 30 days, most of it settled to the bottom.

[0087] Comparative Example 2

[0088] The preparation method of this comparative example is the same as that of comparative example 1, except that the graphite raw material used in this comparative example is Kish graphite.

[0089] The zeta potential of the graphene oxide prepared according to the above process was measured as follows: Figure 3 As shown, the optical photographs taken after it has been left to stand for 30 days are as follows: Figure 5 As shown in Figure c, the Zeta potential values ​​are shown in Table 1. As can be seen from the figure, the graphene oxide prepared in Comparative Example 2 has poor dispersibility, and most of it settles to the bottom after standing for 30 days.

[0090] Comparative Example 3

[0091] The preparation method of this comparative example is the same as that of comparative example 1, except that the electrolyte temperature is controlled at 90℃ in this comparative example.

[0092] The zeta potential of the graphene oxide prepared according to the above process flow was measured as follows: Figure 4 As shown, the optical photographs taken after it has been left to stand for 30 days are as follows: Figure 5 As shown in d, the Zeta potential values ​​are shown in Table 1. As can be seen from the figure, the graphene oxide prepared in Comparative Example 3 also exhibits poor dispersibility, with some settling at the bottom after standing.

[0093] The zeta potential test results are shown in Table 1 below:

[0094] Table 1

[0095]

[0096]

[0097] As can be seen from the experimental data in Table 1, the absolute values ​​of the Zeta potential of Comparative Examples 1-3 are relatively small, indicating poor dispersibility and a tendency to agglomerate and settle. In contrast, the graphene oxide prepared by the method of this invention has a higher absolute value of the Zeta potential. The addition of an amino modifier during the electrolysis process allows the grafting modification and electroexfoliation of the graphene surface to proceed simultaneously, increasing the electrostatic repulsion between graphene particles and thus significantly improving the dispersibility of the prepared graphene oxide.

[0098] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0099] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing highly dispersible graphene oxide, characterized in that, include: (1) Mix graphite, concentrated sulfuric acid and hydrogen peroxide to obtain expanded graphite; (2) Electrochemically exfoliate the expanded graphite to obtain the highly dispersed graphene oxide; The electrolyte used in the electrochemical stripping process includes an amino modifier; The amino modifier includes at least one of 2-aminobenzamide, 3,5-diaminobenzoic acid, polyaniline, and 3,5-diaminobenzenesulfonic acid; The concentration of the amino modifier in step (2) is 0.1 ~ 0.5 mol / L.

2. The preparation method according to claim 1, characterized in that, The graphite includes at least one of natural flake graphite, microcrystalline graphite, artificial graphite, and Kish graphite.

3. The preparation method according to claim 1, characterized in that, The electrolyte in step (2) also includes at least one of inorganic acids and inorganic salts.

4. The preparation method according to claim 3, characterized in that, The inorganic acid includes at least one of sulfuric acid, hydrochloric acid, and phosphoric acid; Optionally, the inorganic salt includes at least one of ammonium sulfate, sodium sulfate, potassium sulfate, and sodium chloride.

5. The preparation method according to claim 3, characterized in that, The concentration of the inorganic acid and / or inorganic salt is 0.1 mol / L to 1 mol / L.

6. The preparation method according to claim 1, characterized in that, Step (2) further includes: The temperature of the electrolyte is controlled to be 0 ~ 90 ℃.

7. The preparation method according to claim 1, characterized in that, The voltage applied during the electrochemical stripping process ranges from 5V to 20V.

8. The preparation method according to claim 1, characterized in that, The electrochemical stripping time is 15 min to 120 min.

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