Graphene oxide, method for producing the same, and graphene

Abstract

The application provides graphene oxide and a preparation method thereof and graphene, and relates to the technical field of graphene materials. The graphene oxide contains oxygen-containing functional groups, the oxygen-containing functional groups include carboxyl groups and / or ketone groups, and the total number of the carboxyl groups and the ketone groups is not more than 30% of the total number of the oxygen-containing functional groups. The preparation method of the graphene oxide comprises the following steps: providing graphene oxide slurry; adjusting the PH of the graphene oxide slurry to PH1 to obtain an intermediate product; adjusting the PH of the intermediate product to PH2 and drying to obtain the graphene oxide; wherein 3≤PH1≤7, 6≤PH2≤11, and PH1<PH2. By reducing the proportion of unstable oxygen-containing functional groups in the graphene oxide, that is, reducing the proportion of the total number of carboxyl groups and ketone groups, and increasing the proportion of stable epoxy groups and hydroxyl groups, the thermal stability of the graphene oxide is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of graphene materials, and particularly relates to graphene oxide, a preparation method thereof and graphene. BACKGROUND

[0002] Graphene oxide is one of the derivatives of graphene, and its main morphological characteristics are similar to those of graphene. Graphene oxide is mainly a two-dimensional sheet material and has a high specific surface area. The difference between graphene oxide and pure graphene material lies in that the pure graphene material is a complete sp 2 honeycomb structure composed of carbon, while graphene oxide is rich in oxygen-containing functional groups such as epoxy groups and carboxyl groups. These oxygen-containing functional groups are usually highly active and can be deoxidized to rebuild molecular bonds under the condition of high temperature or reducing agent, thereby completing the reduction of graphene oxide to graphene. In the application process of graphene oxide, it is often used as a precursor for the preparation of graphene material and its derivative materials, and has the characteristics of easy industrial production and excellent processing performance. Graphene can be prepared by a series of high-temperature treatment of graphene oxide, so that the oxygen-containing functional groups are decomposed at high temperature, and then graphene material is prepared.

[0003] Graphene oxide contains a large amount of oxygen-containing functional groups. The high activity of these oxygen-containing functional groups reduces the stability of graphene oxide. When the temperature rises to about 200℃, because different functional groups in the oxygen-containing functional groups decompose violently and generate a large amount of heat in a short time, the graphene oxide expands violently. In the industrialization process of graphene prepared from graphene oxide, heating and deoxidation is a key link, but uncontrolled heating will reduce the yield of the processing technology, and even cause safety hazards. For example, in the preparation process of graphene heat film, the thermal runaway of graphene oxide raw film will cause the film to expand, smoke and burn, etc. Moreover, the poor thermal stability also makes the storage conditions of graphene oxide more stringent.

[0004] At present, in the existing industrial technology, the thermal runaway of graphene oxide is usually avoided by slowing down the heating rate in the heat treatment process and storing at low temperature, but such methods will cause problems such as reduced processing efficiency and increased storage cost. SUMMARY

[0005] The purpose of the present application is to provide graphene oxide, a preparation method thereof and graphene, which reduce the proportion of oxygen-containing functional groups such as carboxyl groups and ketone groups to improve the stability of graphene oxide.

[0006] To achieve the above purpose, the technical solutions of the present application are as follows:

[0007] In a first aspect, the present application provides a graphene oxide, wherein the graphene oxide contains oxygen-containing functional groups, the oxygen-containing functional groups include carboxyl groups and / or ketone groups, and the total number of the carboxyl groups and the ketone groups is not more than 30% of the total number of the oxygen-containing functional groups.

[0008] In combination with the first aspect, in a feasible implementation, the oxygen-containing functional groups further include hydroxyl groups and / or epoxy groups, and the total number of the hydroxyl groups and the epoxy groups is 70%-100% of the total number of the oxygen-containing functional groups.

[0009] In combination with the first aspect, in a feasible implementation, the graphene oxide satisfies at least one of the following conditions a-e:

[0010] a. The graphene oxide contains carbon elements, oxygen elements and hydrogen elements;

[0011] b. In the graphene oxide, the mass percentage of the carbon elements is 29%-94%, the mass percentage of the oxygen elements is 5%-70%, and the mass percentage of the hydrogen elements is 1%-10%;

[0012] c. The mass ratio O / C of the oxygen elements to the carbon elements in the graphene oxide is 0.05-1.2;

[0013] d. The graphene oxide further contains at least one of sulfur elements, nitrogen elements and impurity elements;

[0014] e. In the graphene oxide, the mass percentage of the sulfur elements is ≤10%, the mass percentage of the nitrogen elements is ≤10%, and the mass percentage of the impurity elements is ≤5%.

[0015] Further, the impurity elements include at least one of Mn, K, Cl, Fe and P.

[0016] In combination with the first aspect, in a feasible implementation, the graphene oxide with high stability satisfies at least one of the following conditions f-g:

[0017] f. In a mixed solution of the graphene oxide and water, when the solid content of the mixed solution is 1%, the pH of the mixed solution is ≥5;

[0018] g. In a deoxidation reaction of the graphene oxide at 100°C-400°C, the heat released per gram is 300J-1400J.

[0019] In a second aspect, the present application further provides a preparation method of graphene oxide, comprising:

[0020] providing graphene oxide slurry;

[0021] adjusting the PH of the graphene oxide slurry to PH1 to obtain an intermediate product;

[0022] The pH of the intermediate product was adjusted to pH2 and dried to obtain the graphene oxide.

[0023] Among them, 3≤PH1≤7, 6≤PH2≤11, and PH1<PH2.

[0024] In conjunction with the second aspect, in one feasible implementation, the preparation method satisfies at least one of the following conditions:

[0025] h. The graphene oxide slurry comprises graphene oxide raw material and solvent, and the pH of the graphene oxide slurry is <3;

[0026] i. The graphene oxide slurry comprises graphene oxide raw material and solvent, wherein the solvent comprises at least one of water, NMP, and DMF;

[0027] j. The solid content of the graphene oxide slurry is 1%-50%;

[0028] k. The step of adjusting the pH of the graphene oxide slurry to pH1 includes: mixing the graphene oxide slurry with an alkaline solution;

[0029] l. The step of adjusting the pH of the intermediate product to pH2 includes: mixing the intermediate product with an alkaline solution.

[0030] Furthermore, the preparation method satisfies at least one of the following conditions:

[0031] m. The alkaline solution includes at least one of ammonia water, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate and sodium bicarbonate solution;

[0032] n. The OH in the alkaline solution - Concentrations range from 0.5 mol / L to 10 mol / L;

[0033] o. The step of mixing the graphene oxide slurry and the alkaline solution includes: adding the alkaline solution to the graphene oxide slurry in M ​​portions, where M≥2;

[0034] p. The step of mixing the intermediate product and the alkaline solution includes: adding the alkaline solution to the intermediate product in N portions, where N≥1;

[0035] q. The step of mixing the graphene oxide slurry and the alkaline solution further includes stirring, wherein the stirring time is 5 min-30 min and the stirring speed is 1000 rpm-6000 rpm;

[0036] r. The step of mixing the intermediate product and the alkaline solution further includes stirring, wherein the stirring time is 10 min-120 min and the stirring speed is 1000 rpm-6000 rpm.

[0037] More preferably, the preparation method satisfies at least one of the following conditions:

[0038] s. In the step of adding the alkaline solution to the graphene oxide slurry in M ​​portions, each time the alkaline solution is added to each 1g graphene oxide slurry containing graphene oxide, the OH groups in the alkaline solution... - The content shall not exceed 0.002 mol;

[0039] t. In the step of adding the alkaline solution to the intermediate product in N portions, each time the alkaline solution is added to each intermediate product containing 1g of graphene oxide, the OH- in the alkaline solution... - The content does not exceed 0.002 mol.

[0040] Furthermore, the drying process in the preparation method includes any one of vacuum drying, heating drying, vacuum filtration, and filtration.

[0041] Thirdly, this application also provides a graphene, wherein the raw materials for preparing the graphene include the graphene oxide described in the first aspect or the graphene oxide prepared by the preparation method described in the second aspect.

[0042] The beneficial effects of this application are:

[0043] The oxygen-containing functional groups in graphene oxide are the most important characteristic determining its thermal stability. Compared to conventional graphene oxide, the graphene oxide of this application has a smaller proportion of carboxyl and ketone groups in its oxygen-containing functional groups. Since carboxyl and ketone groups are more chemically reactive than other oxygen-containing functional groups, their high reactivity leads to decreased stability. Therefore, the fewer carboxyl and ketone groups in the oxygen-containing functional groups of the graphene oxide of this application, the higher its thermal stability.

[0044] In the method for preparing graphene oxide in this application, the unstable carbon-based oxides in the graphene oxide slurry are effectively removed by stepwise control of the pH, leaving stable groups and thus improving the thermal stability of the material. Specifically, during the process of obtaining the intermediate product, the pH of the graphene oxide slurry is gradually increased, leading to intensified swelling of the graphene oxide and increased interlayer spacing. Raising the pH to pH 1 at this point facilitates the full release of acids within the graphene oxide. Especially when the pH of the intermediate product is adjusted to 5-6, the surface charge of the graphene oxide is highest, and the dispersibility is best, which is conducive to subsequent reactions. Further adjusting the pH of the intermediate product to pH 2 allows the remaining unstable carbon-based oxides in the graphene oxide to fully react and dissolve. These unstable carbon-based oxides are rich in carboxyl and / or ketone groups; therefore, after sufficient reaction, the exothermic heat of deoxidation in the prepared graphene oxide under heating is significantly reduced, thereby reducing the probability of thermal runaway and improving the thermal stability of the graphene oxide. The preparation process of this application is simple, requires a wide range of process conditions, and has relatively low cost, making it suitable for industrial production. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope of the present invention.

[0046] Figure 1 This is a flowchart of the preparation method for graphene oxide;

[0047] Figure 2 The appearance of the samples prepared for Example 1 and Comparative Example 1 after being kept at 400°C for 28 hours in air atmosphere. Detailed Implementation

[0048] As used in this article:

[0049] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0050] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0051] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0052] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0053] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0054] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0055] In a first aspect, this application provides a graphene oxide containing oxygen-containing functional groups, wherein the oxygen-containing functional groups include carboxyl groups and / or ketone groups, and the total number of carboxyl groups and ketone groups does not exceed 30% of the total number of oxygen-containing functional groups, for example, it can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, or any value between 0% and 30%.

[0056] In the graphene oxide of this application, the total proportion of carboxyl and ketone groups in the oxygen-containing functional groups is reduced. Since carboxyl and ketone groups are more chemically reactive than other oxygen-containing functional groups, their high reactivity leads to decreased stability of the graphene oxide. Therefore, the fewer carboxyl and ketone groups in the oxygen-containing functional groups of the graphene oxide of this application, the higher its thermal stability.

[0057] As an optional technical solution of this application, the oxygen-containing functional groups also include hydroxyl and epoxy groups, and the total number of hydroxyl and epoxy groups accounts for 70%-100% of the total number of oxygen-containing functional groups, for example, it can be 70%, 75%, 80%, 85%, 90%, 95%, 100% or any value between 70% and 100%.

[0058] It should be noted that the oxygen-containing functional groups in graphene oxide are the most important characteristic that determines the thermal stability of the material. Under the condition of constant oxidation, the fewer the total number of unstable carboxyl and ketone groups and the more stable hydroxyl and epoxy groups in graphene oxide, the better its thermal stability.

[0059] As an optional technical solution in this application, graphene oxide includes carbon, oxygen and hydrogen elements.

[0060] Specifically, the mass percentage of carbon in graphene oxide is 29%-94%, for example, it can be 29%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 94%, or any value between 29% and 94%. The mass percentage of oxygen is 5%-70%, for example, it can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or any value between 5% and 70%. The mass percentage of hydrogen is 1%-10%, for example, it can be 1%, 3%, 50%, 8%, 10%, or any value between 1% and 10%.

[0061] As an optional technical solution in this application, the mass ratio of oxygen to carbon in graphene oxide, i.e., O / C, is 0.05-1.2, for example, it can be 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2 or any value between 0.05 and 1.2.

[0062] It should be noted that carbon and oxygen are the two main elements in the graphene oxide of this application. By ensuring the proportion of oxygen, the graphene oxide can maintain its tunable, self-assembly, and good water solubility.

[0063] As an optional technical solution in this application, graphene oxide also includes at least one of the elements S, N, and impurity elements.

[0064] Specifically, the mass percentage of sulfur in graphene oxide is ≤10%, for example, it can be 0.01%, 2%, 4%, 6%, 8%, 10%, or any value between 0 and 10%; the mass percentage of nitrogen is ≤10%, for example, it can be 0, 2%, 4%, 6%, 8%, 10%, or any value between 0 and 10%; the mass percentage of impurity elements is ≤5%, for example, it can be 0, 1%, 2%, 3%, 4%, 5%, or any value between 0 and 5%.

[0065] Furthermore, the impurity elements in graphene oxide include at least one of Mn, K, Cl, Fe, and P.

[0066] It is understandable that the mass proportion of nitrogen and sulfur elements in the graphene oxide in this application is not high, which can reduce the production of acidic gases during the processing of graphene oxide, making the production process more environmentally friendly and reliable.

[0067] As an optional technical solution of this application, in a mixed solution of graphene oxide and water, when the solid content of the mixed solution is 1%, the pH of the mixed solution is ≥5, for example, it can be 5, 6, 7, 8, 9, 10, 11 or any value ≥5.

[0068] As an optional technical solution in this application, the heat released per gram of graphene oxide sample during the deoxygenation reaction at 100℃-400℃ is 300J-1400J, for example, it can be any value between 300J, 500J, 800J, 1000J, 1200J, 1400J or 300J-1400J.

[0069] Secondly, this application also provides a method for preparing the above-mentioned graphene oxide, including:

[0070] S1. Provide graphene oxide slurry;

[0071] S2. Adjust the pH of the graphene oxide slurry to pH1 to obtain the intermediate product;

[0072] S3. Adjust the pH of the intermediate product to pH2, dry it, and obtain graphene oxide.

[0073] Among them, 3≤PH1≤7, 6≤PH2≤11, and PH1<PH2.

[0074] As an optional technical solution in this application, the graphene oxide slurry in S1 comprises graphene oxide raw material and solvent. Further, the solvent comprises at least one of water, NMP, and DMF. More preferably, the solvent is water.

[0075] As an optional technical solution of this application, the solid content in the graphene oxide slurry in S1 is 1%-50%, for example, it can be 1%, 5%, 10%, 20%, 30%, 40%, 50%, or any value between 1% and 50%.

[0076] It should be noted that the graphene oxide raw material used in the graphene oxide slurry of this application is the industrially common graphene oxide. These raw materials themselves carry a large number of oxygen-containing functional groups such as carboxyl and hydroxyl groups. These highly active oxygen-containing functional groups will be acidic in the slurry solution, resulting in a low pH value of the formed graphene oxide slurry. Generally, pH < 3. If pH is greater than or equal to 3, the pH should be adjusted to pH 1 first. pH 1 is higher than the original pH of the graphene oxide slurry, but should be maintained between 3 and 7. Then, the pH should be adjusted to pH 2, and pH 2 should be maintained between 6 and 11, and pH 1 < pH 2.

[0077] As an optional technical solution of this application, the step of adjusting the pH of the graphene oxide slurry to pH1 in S2 includes: mixing the graphene oxide slurry with an alkaline solution.

[0078] As an optional technical solution of this application, the step of adjusting the pH of the intermediate product to pH2 in S3 includes: mixing the intermediate product with an alkaline solution.

[0079] It is understandable that graphene oxide slurry is acidic due to the presence of oxygen-containing functional groups, so mixing graphene oxide slurry with alkaline solution can adjust the pH value of the slurry.

[0080] In a preferred embodiment, the alkaline solution includes at least one selected from ammonia, potassium hydroxide solution, sodium hydroxide solution, sodium carbonate solution, potassium carbonate solution, and sodium bicarbonate solution. More preferably, the alkaline solution is selected from ammonia.

[0081] Different alkaline substances are prepared into solutions, that is, added to the graphene oxide slurry in the form of alkaline solutions. This facilitates the mixing and reaction of the alkali in the alkaline solution with the graphene oxide, and can greatly shorten the time required for the two substances to mix evenly and for the reaction to occur.

[0082] In a preferred embodiment, the OH in the alkaline solution... - The concentration is 0.5 mol / L to 10 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, 10 mol / L, or any value between 0.5 mol / L and 10 mol / L.

[0083] In a preferred embodiment, the step of mixing the graphene oxide slurry and the alkaline solution includes adding the alkaline solution to the graphene oxide slurry in M ​​portions, where M ≥ 2.

[0084] More preferably, in the step of adding the alkaline solution to the graphene oxide slurry in M ​​portions, each time the alkaline solution is added to every 1g of graphene oxide slurry containing graphene oxide, the OH groups in the alkaline solution... - The content shall not exceed 0.002 mol, for example, it can be 0.0005 mol, 0.001 mol, 0.0015 mol, etc.

[0085] In a preferred embodiment, the step of mixing graphene oxide slurry and alkaline solution to obtain an intermediate product further includes stirring.

[0086] It should be noted that after each addition of alkali solution to the graphene oxide slurry, stirring is required. The stirring time for each stirring session is 5-30 minutes, for example, it can be any value between 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, or 5 minutes and 30 minutes. The stirring speed is 1000 rpm-6000 rpm, for example, it can be any value between 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, or 1000 rpm and 6000 rpm.

[0087] During the process of gradually increasing the pH value of the graphene oxide slurry to obtain intermediate products, the graphene oxide in the slurry swells more rapidly, and the interlayer spacing also gradually increases. If the alkali solution is added to the slurry in multiple small amounts each time, the interlayer spacing of the graphene oxide will also increase as the pH value slowly rises, allowing the acidic groups inside to be fully released and neutralized. However, if a large amount of alkali solution is added directly at once to adjust the pH of the slurry, the pH change is too rapid, making it difficult for the graphene oxide to fully release the acids inside. As a result, the graphene oxide prepared subsequently will still contain a large number of unstable functional groups, thus affecting the thermal stability of the graphene oxide.

[0088] By adding alkali solution to graphene oxide slurry in small amounts multiple times, an intermediate product is obtained with a pH value of PH1, which can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 or any value between 3 and 7.

[0089] More preferably, the intermediate product has a pH value of 5-6. Specifically, when adding the alkali solution to the graphene oxide slurry in M ​​portions to obtain the intermediate product, stirring and dispersing are required after each addition of the alkali solution. The stirring speed can be specifically set to 3000 rpm. After stirring for 10 minutes, the pH value of the mixed solution is tested. If the pH is lower than 5, alkali solution is added again, and stirring is repeated for another 10 minutes, and the pH value is tested again, until the pH value of the mixed solution reaches 5-6.

[0090] Of particular note is that when the pH of the intermediate product reaches the range of 5-6, in order to ensure sufficient swelling of the graphene oxide and release of the acids present within it, the intermediate product needs to be stirred for a prolonged period, from 40 minutes to 8 hours. At this point, the graphene oxide in the slurry exhibits the highest degree of swelling, the highest surface charge, and the best dispersion, which is conducive to the occurrence of subsequent reactions. Sufficient stirring further facilitates the full release and neutralization of acidic groups within the graphene oxide, helping to reduce the proportion of carboxyl and ketone groups. The stirring time can be 40 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours, with 2 hours to 8 hours being the preferred stirring time.

[0091] In a preferred embodiment, the step of mixing the intermediate product and the alkali solution includes adding the alkali solution to the intermediate product in N portions, where N ≥ 2.

[0092] More preferably, in the step of adding the alkali solution to the intermediate product in N portions, each time the alkali solution is added to the intermediate product containing 1g of graphene oxide, the OH- in the alkali solution... - The content shall not exceed 0.002 mol, for example, it can be 0.0005 mol, 0.001 mol, 0.0015 mol, etc.

[0093] In a preferred embodiment, the step of mixing the intermediate product and the alkali solution further includes stirring. After each addition of alkali solution, the mixture of intermediate products is stirred for a period of 10 min to 120 min, for example, 10 min, 30 min, 50 min, 80 min, 100 min, 120 min, or any value between 10 min and 120 min; the stirring speed is 1000 rpm to 6000 rpm, for example, 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, or any value between 1000 rpm and 6000 rpm.

[0094] Specifically, after adding alkaline solution to the intermediate product at pH 5-6, stirring at 3000 rpm for 10 minutes allows the alkaline substances in the solution to fully contact the graphene oxide, thereby reacting and decomposing the residual carbon-based oxides in the graphene oxide. These carbon-based oxides are generally rich in carboxyl and ketone groups, have poor stability, and are prone to thermal decomposition in the range of 100℃-400℃, affecting the thermal stability of graphene oxide. Therefore, fully reacting and removing them in alkaline solution can greatly improve the thermal stability of graphene oxide.

[0095] In a preferred embodiment, during the preparation of the graphene oxide slurry in S1, stirring is also required using a mixer to ensure the graphene oxide raw material is evenly distributed in the slurry, which is beneficial for subsequent reactions. In this case, stirring can be performed at a low speed first, followed by high speed. Specifically, stirring can be performed at 300 rpm for 10 minutes, then the speed can be increased to 3000 rpm, and stirring can continue for another 30 minutes. It is understood that using low-speed and high-speed stirring can better disperse the graphene oxide raw material evenly, which is beneficial for subsequent reactions.

[0096] As an optional technical solution in this application, the drying in S3 includes any one of vacuum drying, heating drying, suction filtration, and filtration. Drying can filter out excess water from the mixed slurry. Simultaneously, during the drying process, unstable carbon-based oxides can be removed along with the water, which also affects the distribution of oxygen-containing functional groups on the surface of graphene oxide. The proportion of more stable functional groups such as epoxy and hydroxyl groups will increase, while the proportion of unstable carboxyl and ketone groups will decrease, ultimately achieving the goal of improving the thermal stability of graphene oxide.

[0097] This application also provides a graphene, the raw material for which the graphene is prepared includes the above-described graphene oxide or graphene oxide prepared by the above-described method for preparing graphene oxide.

[0098] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0099] Example 1

[0100] This embodiment provides a graphene oxide, the specific preparation method of which includes:

[0101] (1) Add water to the graphene oxide raw material to prepare a slurry with a solid content of 1% in 170mL. Stir it for 10 minutes at 300rpm using a mixer, and then increase the speed to 3000rpm and disperse for 30 minutes.

[0102] (2) Add 1 mL of 1 mol / L ammonia dilution to the slurry from step (1), set the speed of the mixer to 3000 rpm, disperse for 10 minutes, and test the pH. Then add the same volume and concentration of ammonia dilution and stir. After four stirring and dispersion cycles, the pH of the slurry mixture was measured to be 4.2. Then continue stirring and dispersing at 3000 rpm for 4 hours.

[0103] (3) Continue to add 1 mL of 1 mol / L ammonia solution to the slurry mixture solution that has been dispersed for 30 minutes in step (2), stir at 3000 rpm for 10 minutes, and then add the same volume and concentration of ammonia solution and stir again. After four stirring and dispersions, the pH of the slurry mixture solution is measured to be 8.9.

[0104] (4) Highly stable graphene oxide powder is obtained by heating and drying the slurry mixture solution.

[0105] Example 2

[0106] This embodiment provides a graphene oxide, and its specific preparation method is the same as that in embodiment 1. The difference is that the addition of ammonia dilution solution in step (2) is changed from four times to three times. After three stirring and dispersion, the pH of the slurry mixture solution is measured to be 3.6. The addition of ammonia dilution solution in step (3) is changed from four times to two times. The stirring and dispersion time between step (2) and step (3) is 2 hours. Finally, the pH of the slurry mixture solution measured in step (3) is 6.1.

[0107] Example 3

[0108] This embodiment provides a graphene oxide, and its specific preparation method is the same as that in embodiment 1. The difference is that in step (2), the addition of ammonia dilution solution four times is changed to three times. After stirring and dispersing three times, the pH of the slurry mixture solution is measured to be 3.6. In step (3), the addition of ammonia dilution solution four times is changed to six times. The stirring and dispersing time between step (2) and step (3) is 6 hours. Finally, the pH of the slurry mixture solution measured in step (3) is 10.4.

[0109] Example 4

[0110] This embodiment provides a graphene oxide, and its specific preparation method is the same as that in embodiment 1. The difference is that the addition of ammonia dilution solution in step (2) is changed from four times to six times. After stirring and dispersing for six times, the pH of the slurry mixture solution is measured to be 5.8. The addition of ammonia dilution solution in step (3) is changed from four times to three times. The stirring and dispersing time between step (2) and step (3) is 7 hours. Finally, the pH of the slurry mixture solution measured in step (3) is 10.8.

[0111] Example 5

[0112] This embodiment provides a graphene oxide, and its specific preparation method is the same as that in Example 1. The difference is that in step (2), 1 mL of 0.5 mol / L ammonia dilution is added each time in 8 steps, and the mixture is stirred and dispersed. The pH of the slurry mixture is measured to be 4.1. In step (3), 1 mL of 0.5 mol / L ammonia dilution is added each time in 8 steps, and the mixture is stirred and dispersed. The stirring and dispersion time between steps (2) and (3) is 5 h. The pH of the slurry mixture measured in step (3) is 9.1.

[0113] Example 6

[0114] This embodiment provides a graphene oxide, and its specific preparation method is the same as that in embodiment 1. The difference is that in step (2), 2 mL of 1 mol / L ammonia dilution is added in two batches each time, and the mixture is stirred and dispersed. The pH of the slurry mixture is measured to be 4.4 at this time. In step (3), 2 mL of 1 mol / L ammonia dilution is added in two batches each time, and the mixture is stirred and dispersed. The stirring and dispersion time between steps (2) and (3) is 3 hours. The pH of the slurry mixture measured in step (3) is 8.7.

[0115] Example 7

[0116] This embodiment provides a graphene oxide, which is prepared in the same way as in embodiment 1. The difference is that the ammonia diluent in steps (2) and (3) is replaced with a 1 mol / L sodium hydroxide solution, the stirring and dispersion time between steps (2) and (3) is 8 h, the pH of the slurry mixture obtained after adding 1 mL four times in step (2) is 5.8, and the pH of the slurry mixture obtained after adding 1 mL four times in step (3) is 10.8.

[0117] Example 8

[0118] This embodiment provides a graphene oxide, which is prepared in the same way as in embodiment 1. The difference is that the ammonia dilution solution in steps (2) and (3) is replaced with a 1 mol / L sodium carbonate solution, the stirring and dispersion time between steps (2) and (3) is 40 min, the pH of the slurry mixture obtained after adding 1 mL in 4 times in step (2) is 3.5, and the pH of the final slurry mixture is 6.0 after adding 1 mL in 3 times in step (3).

[0119] Comparative Example 1

[0120] This comparative example provides a graphene oxide, the specific preparation method of which includes:

[0121] (1) Add water to the graphene oxide raw material to prepare a slurry with a solid content of 1% in 170 mL. Stir it for 10 minutes at 300 rpm using a stirring disperser, and then increase the speed to 3000 rpm and disperse for 30 minutes. The pH of the graphene oxide slurry was measured to be 2.101 at this time.

[0122] (2) Graphene oxide powder is obtained by heating and drying.

[0123] Comparative Example 2

[0124] This comparative example provides a graphene oxide, the specific preparation method of which is the same as that in Example 1. The difference is that: in step (3), ammonia water dilution is no longer added, but the mixed slurry solution in step (2) is directly heated and dried to obtain graphene oxide powder.

[0125] Comparative Example 3

[0126] This comparative example provides a graphene oxide, the specific preparation method of which is the same as that in Example 1, except that: in step (2), 8 mL of 1 mol / L ammonia water dilution is added directly at one time, and after dispersing at a speed of 3000 rpm for 80 minutes, the pH of the mixed slurry is measured to be 11.2; then it is directly heated and dried to obtain graphene oxide powder.

[0127] The performance parameters of the graphene oxide prepared in Examples 1-8 and Comparative Examples 1-3 were measured in the following manner:

[0128] The specific mass percentages of C, H, O, N, and S were determined using an organic elemental analyzer: Using an Elementarvario EL cube analyzer, before testing, first open the pressure reducing valves for argon and oxygen to adjust the gas pressure; then turn on the instrument power and computer power, confirming the elemental analyzer and computer workstation are connected; once all instrument statuses are "OK", the instrument enters the test-ready state, use a syringe to take an appropriate amount of sample into the instrument, and operate the workstation to start the analysis; after analysis, save the test results, remove the test sample, exit the software, and shut down the computer; turn off the instrument power, and then close the argon and oxygen pressure reducing valves.

[0129] The proportions of hydroxyl, epoxy, carboxyl, and ketone groups were determined by X-ray photoelectron spectroscopy (XPS): Using a Thermo Fisher ESCALab250Xi X-ray photoelectron spectrometer, the powder sample was first pressed into a pellet, fixed on the sample stage, and sent into the sample injection chamber. After the vacuum level reached the standard, the sample was sent to the analysis chamber, and the sample position was manually adjusted to achieve the optimal testing position. The X-ray source was turned on, and the test results were collected and saved. After the data acquisition was completed, the X-ray gun and electron neutralization gun were turned off, and the sample was removed from the analysis chamber. The test results were saved for subsequent analysis.

[0130] The heat released by the deoxidation reaction of the sample at 400℃ was measured using a differential scanning calorimeter (DSC3, model Mettler DSC3). The dried graphene oxide sample was ground and placed in an aluminum crucible, which was then placed in the DSC furnace. The furnace chamber was purged with air at a flow rate of 40 mL / min, and the test began. After data acquisition, the instrument automatically stopped heating, and the next test was performed after the instrument cooled to room temperature.

[0131] The graphene oxide samples prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to the above-mentioned different tests, and the specific test results are shown in Table 1.

[0132] Table 1

[0133]

[0134]

[0135]

[0136] Figure 1 A flowchart illustrating the preparation process of graphene oxide according to this application is shown. Figure 2 The images show the appearance of the samples prepared in Example 1 and Comparative Example 1 after being kept at 400°C in air for 28 hours. From... Figure 2 It is evident that the graphene oxide film in Example 1 has a uniformly distributed surface and intact edges, while the graphene oxide film in Comparative Example 1 shows uneven burning marks and severely broken edges. When handling the two samples, it is also clear that the sample in Example 1 is flexible and bendable, while the sample in Comparative Example 1 is brittle and inflexible.

[0137] Combining the different test results of Examples 1-8 and Comparative Examples 1-3 in Table 1, it is clear that: in the process of improving the stability of graphene oxide, this application can indeed react and decompose the unstable carbon-based oxides in the graphene oxide raw material by treating the graphene oxide slurry with alkaline solution in stages, thereby increasing the proportion of stable oxygen-containing functional groups such as epoxy groups and hydroxyl groups, and reducing the proportion of unstable oxygen-containing functional groups such as carboxyl groups and ketone groups, which greatly improves the thermal stability of graphene oxide (the less heat generated by the deoxygenation reaction at 400℃, the better the thermal stability).

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0139] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing graphene oxide, characterized in that, include: Provide graphene oxide slurry; The pH of the graphene oxide slurry was adjusted to pH1 to obtain an intermediate product; The pH of the intermediate product was adjusted to pH2 and dried to obtain the graphene oxide. Where 3≤PH1≤7, 6≤PH2≤11, and PH1<PH2; The step of adjusting the pH of the graphene oxide slurry to pH1 includes: mixing the graphene oxide slurry with an alkaline solution; The step of adjusting the pH of the intermediate product to pH2 includes: mixing the intermediate product with an alkaline solution; The step of mixing the graphene oxide slurry and the alkaline solution further includes stirring, wherein the stirring time is 5 min-30 min and the stirring speed is 1000 rpm-6000 rpm; The step of mixing the intermediate product and the alkaline solution further includes stirring, wherein the stirring time is 10 min-120 min and the stirring speed is 1000 rpm-6000 rpm; The graphene oxide contains oxygen-containing functional groups, including carboxyl groups and / or ketone groups, wherein the total number of carboxyl groups and ketone groups does not exceed 30% of the total number of oxygen-containing functional groups. The oxygen-containing functional groups further include hydroxyl groups and / or epoxy groups, wherein the total number of hydroxyl groups and epoxy groups accounts for 70%-100% of the total number of oxygen-containing functional groups.

2. The method for preparing graphene oxide as described in claim 1, characterized in that, At least one of the following conditions ae must be satisfied: a. The graphene oxide comprises carbon, oxygen, and hydrogen elements; b. In the graphene oxide, the mass percentage of carbon is 29%-94%, the mass percentage of oxygen is 5%-70%, and the mass percentage of hydrogen is 1%-10%. c. The mass ratio of oxygen to carbon in the graphene oxide is 0.05-1.2; d. The graphene oxide further includes at least one of sulfur and nitrogen elements; e. In the graphene oxide, the mass percentage of sulfur is ≤10% and the mass percentage of nitrogen is ≤10%.

3. The method for preparing graphene oxide as described in claim 1 or 2, characterized in that, At least one of the following conditions fg must be met: f. In the mixed solution of graphene oxide and water, when the solid content of the mixed solution is 1%, the pH of the mixed solution is ≥5; g. The heat released per gram of the graphene oxide during the deoxygenation reaction at 100℃-400℃ is 300J-1400J.

4. The method for preparing graphene oxide as described in claim 1, characterized in that, At least one of the following conditions hj must be met: h. The graphene oxide slurry comprises graphene oxide raw material and solvent, and the pH of the graphene oxide slurry is <3; i. The graphene oxide slurry comprises graphene oxide raw material and solvent, wherein the solvent comprises at least one of water, NMP, and DMF; j. The solid content of the graphene oxide slurry is 1%-50%.

5. The method for preparing graphene oxide as described in claim 4, characterized in that, At least one of the following conditions must be met in mp: m. The alkaline solution includes at least one of ammonia water, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate and sodium bicarbonate solution; n. The OH in the alkaline solution - Concentrations range from 0.5 mol / L to 10 mol / L; o. The step of mixing the graphene oxide slurry and the alkaline solution includes: adding the alkaline solution to the graphene oxide slurry in M ​​portions, where M≥2; p. The step of mixing the intermediate product and the alkaline solution includes: adding the alkaline solution to the intermediate product in N portions, where N ≥ 2.

6. The method for preparing graphene oxide as described in claim 5, characterized in that, At least one of the following conditions must be met: s. In the step of adding the alkaline solution to the graphene oxide slurry in M ​​portions, each time the alkaline solution is added to each 1g graphene oxide slurry containing graphene oxide, the OH groups in the alkaline solution... - The content shall not exceed 0.002 mol; t. In the step of adding the alkaline solution to the intermediate product in N portions, each time the alkaline solution is added to each intermediate product containing 1g of graphene oxide, the OH- in the alkaline solution... - The content does not exceed 0.002 mol.

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