Preparation method of high-dispersity graphene oxide

Abstract

The invention 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 performing electrochemical stripping on the expanded graphite to obtain the high-dispersity graphene oxide, wherein an electrolyte adopted in the electrochemical stripping process comprises an amino modifier. According to the preparation method, the amino modifier is added into the electrolyte, so that electrochemical stripping and grafting modification of the graphene oxide are synchronously carried out, the graphene oxide with high dispersity is obtained, and the preparation method is simple and convenient to operate, low in cost, high in efficiency and easy to regulate and control.

Description

Technical Field

[0001] The invention relates to the field of graphene materials, and in particular to a method for preparing highly dispersible graphene oxide. Background Art

[0002] Graphene is a unique two-dimensional material with excellent physical and chemical properties such as mechanical properties, thermal properties, electrical properties, and good chemical stability. It is widely used in new composite materials, optoelectronic materials, biosensors, and other fields. However, the special π-π conjugation and van der Waals forces of graphene cause the graphene sheets to easily aggregate and accumulate, and cannot be evenly dispersed in the solution, limiting the effective application of graphene. As a derivative of graphene, graphene oxide (GO) is a quasi-two-dimensional layered structure containing a large number of oxygen-containing functional groups such as hydroxyl, carboxyl, and epoxy groups. It has strong hydrophilicity and can be evenly dispersed in water. The oxidation degree of graphene prepared by electrochemical exfoliation is low, and its uniform dispersion in aqueous solution faces challenges.

[0003] Therefore, improving the dispersibility of electrochemically prepared graphene oxide is critical to expanding its application. Extensive research has been conducted to improve the dispersibility of graphene oxide through complex physical methods or chemical modification, but the existing preparation and modification process involves complex steps such as separation, stirring, hydrothermal treatment, and secondary ultrasound, which is inefficient, costly, and difficult to control the degree of modified grafting.

[0004] Therefore, there is an urgent need to provide an electrochemical preparation method for highly dispersed graphene oxide that is simple to operate and highly efficient. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present invention provides a method for preparing highly dispersible graphene oxide, wherein the preparation and modification of graphene oxide are carried out simultaneously by electrochemically exfoliating expanded graphite and adding an amino modifier to an electrolyte, thereby obtaining a highly dispersible graphene oxide, and the preparation method is simple to operate, low in cost, high in efficiency, and easy to control.

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

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

[0008] (2) electrochemically exfoliating the expanded graphite to obtain the highly dispersible graphene oxide;

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

[0010] During the research process, the inventors found that increasing the current density of the electrode during the preparation of graphene by electrochemical stripping is conducive to obtaining graphene with a smaller sheet diameter, thereby increasing the degree of oxidation of the graphene edge to improve its dispersibility, and the close contact degree between the graphite particles is the main factor restricting the current density. The present invention obtains a highly cross-linked expanded graphite deposit by mixing graphite, concentrated sulfuric acid and hydrogen peroxide, improves the close contact degree between the graphite particles, and is conducive to obtaining a higher current density in the subsequent electrochemical stripping process to promote the production of small-diameter graphene oxide. At the same time, an electrolyte containing an amino modifier is used in the electrochemical stripping process, which can realize the electrostatic repulsion between graphenes by grafting functional groups on the graphene surface, and significantly improves the dispersibility of electrochemically stripped graphene oxide.

[0011] According to an embodiment 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 an inorganic acid and an inorganic salt.

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

[0014] According to an embodiment of the present invention, the inorganic salt includes at least one of 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 an embodiment of the present invention, the amino modifier includes at least one of 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, the step (2) further comprises:

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

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

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

[0022] The beneficial effects of the present invention compared to the prior art are as follows:

[0023] The present invention provides an electrochemical preparation method for highly dispersible graphene oxide, which increases the degree of crosslinking between graphite particles by preparing an expanded graphite stack, and combines electrochemical stripping to obtain highly dispersible, small-diameter graphene oxide. The preparation method does not require the removal of sulfuric acid before electrochemical stripping, and the preparation and modification of graphene oxide are carried out simultaneously, which reduces intermediate steps, environmental pollution, production costs and energy consumption.

[0024] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments 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 the present invention is shown;

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

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

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

[0030] Figure 5 Optical photographs of the graphene oxide dispersion prepared by 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; Figure d is an optical photograph of the graphene oxide dispersion prepared in Comparative Example 3 after standing for 30 days. DETAILED DESCRIPTION

[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 understood 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 understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0033] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0034] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0035] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0036] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0037] According to an embodiment of the present invention, the present invention provides a method for preparing highly dispersible graphene oxide, comprising:

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

[0039] In this step, hydrogen peroxide oxidizes the edges of graphite, 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 degree of graphite is increased under the driving effect of decomposition and oxygen generation, thereby obtaining a highly cross-linked expanded graphite accumulation body, and improving the closeness of contact between graphite particles, so as to obtain a higher current density during the electrochemical stripping process to promote the production of small-diameter graphene oxide.

[0040] According to a specific embodiment 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, the expanded graphite can be prepared by uniformly mixing graphite, concentrated sulfuric acid and hydrogen peroxide in an ice bath, transferring the mixture into a fixed volume container, and standing at room temperature to obtain a highly cross-linked expanded graphite stack.

[0042] (2) electrochemically exfoliating the expanded graphite to obtain the highly dispersible graphene oxide;

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

[0044] In this step, the amino modifier can graft functional groups on the surface of graphene oxide, and the electrochemical exfoliation of graphene oxide and the grafting modification are carried out simultaneously, thereby increasing the electrostatic repulsion between graphenes, thereby significantly improving the dispersibility of electrochemically exfoliated graphene oxide.

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

[0046] According to a specific embodiment of the present invention, the type of the 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 a specific embodiment of the present invention, the type of the 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 a specific embodiment 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 a specific embodiment of the present invention, the type of the 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 a specific embodiment of the present invention, the concentration of the amino modifier is 0-0.5 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 the present invention, when ammonium sulfate or other electrolytes are selected, the expanded graphite expanded in a fixed volume container does not need to undergo a desulfurization process, and can be stripped after the opening and insertion of the electrode. The bubbles generated during the stripping process play a disturbing role, promoting the contact probability between graphene and the modifier. In addition, the heat generated during the electrochemical stripping process can also accelerate the reaction rate of the modifier on the graphene surface, improve the grafting modification of the functional group on the graphene surface, and further improve the dispersibility of the graphene oxide.

[0052] According to a specific embodiment of the present invention, the specific operation of step (2) can be to open a small hole in the container, insert a platinum wire as an electrochemical anode, another platinum wire as a cathode, immerse in an electrolyte containing an amino modifier, apply an external voltage for electrochemical stripping, separate the reaction products after electrolysis, and obtain highly dispersed graphene oxide. According to a specific embodiment of the present invention, the step (2) further includes:

[0053] The temperature of the electrolyte is controlled to be 0-90° C. As some specific examples, the temperature of the electrolyte may 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 and increasing the electrostatic repulsion between graphenes, thereby significantly improving the dispersibility of electrochemically exfoliated graphene oxide.

[0055] According to a specific embodiment of the present invention, the voltage applied during the electrochemical stripping process ranges from 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 a specific embodiment of the present invention, the time of the electrochemical stripping is 15 min to 120 min. As some specific examples, the time of the electrochemical stripping may be 15 min, 30 min, 60 min, 90 min, 120 min, etc.

[0057] According to a specific embodiment of the present invention, the separation method of the 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 scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0059] Example 1

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

[0061] (2) A 2 mm hole was opened in the container, a platinum wire was inserted as an electrochemical anode, another platinum wire electrode was used as a cathode, the electrode spacing was 2 cm, the electrolyte was 0.5 mol / L ammonium sulfate, the amino modifier was 0.1 mol / L 2-aminobenzamide, the electrolyte temperature was controlled at 30°C, an external voltage of 10 V was applied, and the electrolysis time was 60 min; the reaction product was filtered and washed to neutrality (pH = 6-7), ultrasonicated at 500 W for 30 min, and centrifuged at 3000 r / min for 10 min to remove graphene particles with thicker flakes, thereby obtaining highly dispersed graphene oxide.

[0062] The Zeta potential of the highly dispersed graphene oxide prepared according to the above process is measured as follows: Figure 1 As shown, the optical photograph after 30 days of standing is as follows Figure 5 a, and its zeta potential value is shown in Table 1. As can be seen from the figure, the graphene oxide prepared in this embodiment does not settle after being left to stand for many days, has a high absolute value of zeta potential, and has excellent dispersibility.

[0063] Example 2

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

[0065] (2) A 2 mm hole was opened in the container, a platinum wire was inserted as an electrochemical anode, another platinum wire electrode was used as a cathode, the electrode spacing was 2 cm, the electrolyte was 0.5 mol / L ammonium sulfate, the amino modifier was 0.1 mol / L polyaniline, the electrolyte temperature was controlled to be 30°C, an external voltage of 12 V was applied, and the electrolysis time was 30 min; the reaction product was filtered and washed to neutrality (pH = 6-7), ultrasonicated at 500 W for 30 min, and centrifuged at 3000 r / min for 10 min to remove graphene particles with thicker flakes, thereby obtaining highly dispersed graphene oxide.

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

[0067] Example 3

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

[0069] (2) A 2 mm hole was opened in the container, and a platinum wire was inserted as an electrochemical anode. Another platinum wire electrode was used as a cathode. The electrode spacing was 2 cm. The electrolyte was 0.5 mol / L ammonium sulfate, and the amino modifier was 0.5 mol / L 2-aminobenzamide. The electrolyte temperature was controlled at 30°C, an external voltage of 8 V was applied, and the electrolysis time was 90 min. The reaction products were separated using a dialysis bag with a molecular weight of 500 to obtain highly dispersed graphene oxide.

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

[0071] Example 4

[0072] The preparation method of this embodiment is the same as that of Embodiment 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 flow are shown in Table 1.

[0074] Example 5

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

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

[0077] Example 6

[0078] The preparation method of this embodiment is the same as that of embodiment 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 flow are shown in Table 1.

[0080] Example 7

[0081] The preparation method of this embodiment is the same as that of embodiment 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 flow are shown in Table 1.

[0083] Comparative Example 1

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

[0085] (2) A 2 mm hole was opened in the container, and a platinum wire was inserted as an electrochemical anode, and another platinum wire electrode was inserted as a cathode. The electrode spacing was 2 cm, the electrolyte was 0.5 mol / L ammonium sulfate, the electrolyte temperature was controlled at 30°C, an external voltage of 10 V was applied, and the electrolysis time was 30 min; the reaction product was filtered and washed to neutrality (pH = 6-7), ultrasonicated at 500 W for 30 min, and centrifuged at 3000 r / min for 10 min to remove graphene particles with thicker flakes, thereby obtaining highly dispersed graphene oxide.

[0086] The Zeta potential of graphene oxide prepared according to the above process is measured as follows Figure 2 As shown, the optical photograph after 30 days of standing is as follows Figure 5 b, and its Zeta potential value is shown in Table 1. As can be seen from the figure, the graphene oxide prepared in Comparative Example 1 has poor dispersibility, and most of it settles to the bottom after standing for 30 days.

[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 graphene oxide prepared according to the above process is measured as follows Figure 3 As shown, the optical photograph after 30 days of standing is as follows Figure 5 c, and its Zeta potential value is 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°C in this comparative example.

[0092] The Zeta potential of graphene oxide prepared according to the above process is measured as follows Figure 4 As shown, the optical photograph after 30 days of standing is as follows Figure 5 d, and its Zeta potential value is shown in Table 1. As can be seen from the figure, the dispersibility of the graphene oxide prepared in Comparative Example 3 is also poor, and part of it settles to the bottom after standing.

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

[0094] Table 1

[0095]

[0096]

[0097] It can be seen from the experimental data in Table 1 that the absolute value of the Zeta potential of Comparative Examples 1-3 is small, the dispersibility is poor, and it is easy to agglomerate and precipitate, while the absolute value of the Zeta potential of the graphene oxide obtained by the preparation method of the present invention is high. The addition of an amino modifier during the electrolysis process allows the graphene surface grafting modification and electrical stripping to proceed simultaneously, increasing the electrostatic repulsion between graphenes, thereby significantly improving the dispersibility of the obtained graphene oxide.

[0098] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0099] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary 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) mixing graphite, concentrated sulfuric acid and hydrogen peroxide to obtain expanded graphite; (2) electrochemically exfoliating the expanded graphite to obtain the highly dispersible graphene oxide; Wherein, the electrolyte used in the electrochemical stripping process includes an amino modifier.

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) further includes at least one of an inorganic acid and an inorganic salt.

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: The amino modifier includes at least one of 2-aminobenzamide, 3,5-diaminobenzoic acid, polyaniline, and 3,5-diaminobenzenesulfonic acid.

7. The preparation method according to claim 1, characterized in that: The concentration of the amino modifier in step (2) is 0 to 0.5 mol / L and is not 0 mol / L.

8. The preparation method according to claim 1, characterized in that: The step (2) further comprises: The temperature of the electrolyte is controlled to be 0-90°C.

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

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

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