Graphene nanosheet layer oxidation intermediate and preparation method and application thereof

Abstract

The application discloses a preparation method of a graphene nanosheet layer oxidation intermediate, which comprises the following steps: 1 part of graphite powder particles is placed in a pure oxygen sealed container, and the sealed container is heated to 600-1200 DEG C, and then ultrasonic pulses are emitted into the sealed container to prepare oxidized pyrolytic graphite; the oxidized pyrolytic graphite is stirred and mixed with 40-100 parts of concentrated sulfuric acid, and then 1 part of an expanding agent, 1 part of a water absorbing agent and 2-8 parts of an oxidizing agent are added to react, and the reaction product is cooled to room temperature after the reaction is completed; a pH stabilizer is added dropwise into the above reaction product, and stirring is conducted to obtain a precipitate, and the precipitate is washed and dried. The application further discloses the graphene nanosheet layer oxidation intermediate prepared by the above preparation method; the oxidation intermediate has very high reaction activity, is easy to transport and store for a long time, can be used as a reaction precursor of novel high-performance materials such as graphene oxide, sulfur-graphene oxide and nitrogen-graphene oxide, and has unique advantages in large-scale synthesis of graphene-based high-performance nanomaterials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new material synthesis, in particular to a graphene nanosheet layer oxidation intermediate and a preparation method and application thereof. BACKGROUND

[0002] Graphene-based nanomaterials, such as graphene oxide, have a unique sheet structure and water-oil amphiphilic structure, and are widely used in heat insulation, adsorption, electromagnetic shielding, energy storage, catalysis, flexible sensing and other fields.

[0003] The patent document with the publication number CN105347340A discloses a preparation method of graphene oxide. Graphite raw material and an oxidation aid are added to an alkali solution and placed in a sealed container. 1-50g of graphite raw material and 1-30g of oxidation aid are added per 100ml of alkali solution. The container is replaced with oxygen gas and filled with oxygen gas to a pressure of 1-20Mpa. The reaction is carried out at a temperature of 101-650℃. After the reaction is completed, the reaction product is removed and solid-liquid separation is carried out. The obtained solid phase is washed and dried to obtain the graphene oxide solid product.

[0004] The patent document with the publication number CN102225754B discloses a preparation method of graphene oxide. Graphite, concentrated acid and strong oxidizing agent are mixed uniformly and reacted at 80-130℃ in a sealed environment to obtain graphene oxide. Hydrazine hydrate is added to the graphene oxide, and after reduction reaction, graphene is obtained. The graphene oxide prepared by the method has more oxygen-containing functional groups, which is beneficial to surface modification and expansion of the application of graphene oxide.

[0005] However, the unique structure of graphene-based nanomaterials has extremely high surface energy and relatively weak chemical stability. The extremely high surface energy can cause it to easily agglomerate, even when dispersed in solution, prolonged storage can cause mutual adsorption between the layers and sedimentation. The chemical stability is not high, which can cause reduction reaction and deterioration during long-term storage. Therefore, graphene-based nanomaterials cannot be stored for a long time, and often need to be prepared and used immediately, which not only limits its application scenarios, but also hinders its industrialization and large-scale production.

[0006] In order to improve the structural stability of graphene-based nanomaterials and reduce the surface energy, the chemical modification method is generally used at home and abroad at present, the structure is changed by small molecule grafting or other means, or the non-ionic surfactant is added, so as to reduce the surface energy and improve the structural stability. However, the structural change caused by chemical modification will also inhibit the performance, and even change the original performance. For example, chemical grafting often consumes the original functional groups, so that the water-oil amphiphilic properties are inhibited. On the other hand, the addition of non-ionic surfactant will reduce the content of graphene-based nanomaterials, reduce the use efficiency of the material; on the other hand, the addition of non-ionic surfactant will further increase the preparation cost of graphene-based nanomaterials, and greatly reduce the performance price ratio of the material. SUMMARY

[0007] In order to overcome the defects of the prior art, the application provides a preparation method of graphene nanosheet layer oxidation intermediate, which has simple process and stable chemical properties, is convenient to transport and store, widens the use scene of graphene-based nanomaterials, and realizes the large-scale and industrialized application.

[0008] A preparation method of graphene nanosheet layer oxidation intermediate, comprising the following steps:

[0009] Step one: 1 part of graphite powder particles is placed in a pure oxygen sealed container, heated to 600-1200 DEG C, and then ultrasonic pulses are emitted into the sealed container for oxidation reaction to prepare oxidized pyrolytic graphite, and then cooled to room temperature after the reaction is completed;

[0010] Step two: the oxidized pyrolytic graphite obtained in step 1 is stirred and mixed with 40-100 parts of concentrated sulfuric acid, then 1 part of an expanding agent, 1 part of a water absorbing agent and 2-8 parts of an oxidizing agent are added for reaction, and then cooled to room temperature after the reaction is completed;

[0011] Step three: the product obtained in step two is dropped into a pH stabilizer, stirred to obtain a precipitate, and then the precipitate is washed and dried to obtain the graphene nanosheet layer oxidation intermediate.

[0012] The graphite powder particles are contacted with pure oxygen in a closed container at 600-1200℃ under the action of ultrasonic pulses, and an oxidative pyrolysis reaction occurs, the large pi bond in the graphite layer is destroyed to introduce oxygen radicals, and the active carbon atoms at the edges of the graphite layer are removed to obtain the oxidative pyrolysis graphite. The large pi bond is destroyed and oxygen radicals are introduced, so that the oxidative pyrolysis graphite is more easily reacted with the oxidizing agent in the concentrated sulfuric acid in step two, and the oxidative pyrolysis graphite avoids directly generating high-polarity groups such as carboxyl groups in the reaction in step two because the active carbon atoms at the edges of the graphite layer are removed, thereby greatly extending the storage time of the final product. After the mild oxidation in step two, most of the conjugated aromatic domains in the graphite are destroyed, the interlayer spacing is opened, and a large amount of carbon-carbon double bonds are generated. The product in step two is quenched into a sufficient amount of pH stabilizer to avoid the erosion of a large amount of hydrogen ions generated by the dissociation of carbon-carbon double bonds and the like by concentrated sulfuric acid, so that the basic chemical structure of the product is retained, which can be used as a reaction intermediate for preparing graphene oxide and sulfurized graphene materials, and the subsequent preparation conditions are simple, and the product can be stored for a long time.

[0013] Preferably, in step one, the particle size of the graphite powder particles is 5-1000μm.

[0014] Preferably, in step one, the pressure of pure oxygen in the closed container is 2-3 atmospheres.

[0015] Preferably, in step one, the ultrasonic pulse power is 80-300W / L, and the emission time is 20-40min. The ultrasonic pulse power of the present application is related to the volume of the closed container, and the ultrasonic pulse power per liter of the container is 80-300W.

[0016] Preferably, in step two, the expanding agent includes persulfate or a foaming agent.

[0017] Preferably, the persulfate is ammonium persulfate.

[0018] Preferably, in step two, the water-absorbing agent includes anhydrous copper sulfate or diphosphorus pentoxide.

[0019] Preferably, in step two, the oxidizing agent includes dichromate, potassium permanganate, perchloric acid, perchlorate, chlorate, nitric acid or nitrate.

[0020] Preferably, in step two, the reaction temperature is 30-50℃, and the reaction time is 2-5h.

[0021] Preferably, in step three, the pH stabilizer includes a saturated sodium bicarbonate solution, a monosodium phosphate solution or a disodium phosphate solution.

[0022] The application further provides the graphene nanosheet layer oxidation intermediate prepared by the preparation method.

[0023] The application further provides application of the graphene nanosheet layer oxidation intermediate in preparation of graphene-based nanomaterials.

[0024] Preferably, the graphene-based nanomaterials include graphene oxide, sulfur-graphene oxide or nitrogen-graphene oxide.

[0025] Compared with the prior art, the application has at least the following beneficial effects:

[0026] The preparation method is simple, the graphene nanosheet layer oxidation intermediate prepared has stable quality, high reaction activity, stable structure and can be stored for a long time, and can be directly converted into graphene oxide, sulfur-graphene oxide, nitrogen-graphene oxide and other high-performance graphene-based nanomaterials through a simple process, which is conducive to promoting the realization of large-scale and industrialized application of graphene-based high-performance materials. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical advantages and values of the application, the following will illustrate the structure of the graphene oxide prepared before and after long-term storage of the comparative examples and the examples.

[0028] Figure 1 The Fourier infrared spectrum of the graphene nanosheet layer oxidation intermediate prepared for the example 1 and the example 2.

[0029] Figure 2 The Fourier infrared spectrum of the graphene oxide prepared for the comparative example 1 before and after storage for 30 days.

[0030] Figure 3 The infrared spectrum comparison of the graphene oxide prepared from the graphene nanosheet layer oxidation intermediate of the example 1 before and after storage for 30 days.

[0031] Figure 4 The infrared spectrum comparison of the graphene oxide prepared from the graphene nanosheet layer oxidation intermediate of the example 2 before and after storage for 30 days. DETAILED DESCRIPTION

[0032] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of the present application.

[0033] Example 1: Graphene nanosheet layer oxidation intermediate

[0034] 1 part of graphite powder with a particle size of 30 μm and pure oxygen were fully contacted for oxidation reaction in a high-pressure reaction kettle at 600 ℃ under the action of ultrasonic pulses, wherein the volume of the high-pressure reaction kettle was 5 L, the power of the ultrasonic pulses was 500 W, the reaction time was 30 min, and after the reaction was completed, oxidized pyrolytic graphite was obtained. The obtained oxidized pyrolytic graphite was uniformly mixed with 50 parts of concentrated sulfuric acid by stirring, then 1 part of ammonium persulfate was added as a graphite sheet layer expanding agent, 1 part of anhydrous copper sulfate was added as a water absorbing agent, and 4 parts of potassium dichromate was added as an oxidizing agent, and after uniform mixing, the mixture was fully reacted at 40 ℃ for 2 hours, and after the reaction was completed, the mixture was cooled to room temperature.

[0035] The obtained mixture was added dropwise into 1000 parts of saturated sodium bicarbonate solution, fully stirred, and then the precipitate was taken; the precipitate was fully washed with saturated sodium bicarbonate solution, then centrifugally washed with distilled water, dried, and then a graphene nanosheet layer oxidation intermediate was obtained.

[0036] Example 2: Graphene nanosheet layer oxidation intermediate

[0037] The difference between the present embodiment and Example 1 is only in the type and proportion of the raw materials, that is, 1 part of graphite powder with a particle size of 180 μm and pure oxygen were fully contacted for oxidation reaction in a high-pressure reaction kettle at 600 ℃ under the action of ultrasonic pulses, wherein the volume of the high-pressure reaction kettle was 8 L, the power of the ultrasonic pulses was 700 W, the reaction time was 40 min, and after the reaction was completed, oxidized pyrolytic graphite was obtained. The obtained oxidized pyrolytic graphite was uniformly mixed with 80 parts of concentrated sulfuric acid by stirring, then 1 part of ammonium persulfate was added as a graphite sheet layer expanding agent, 1 part of anhydrous copper sulfate was added as a water absorbing agent, and 8 parts of potassium dichromate was added as an oxidizing agent, and after uniform mixing, the mixture was fully reacted at 40 ℃ for 5 hours, and after the reaction was completed, the mixture was cooled to room temperature.

[0038] The obtained mixture was added dropwise into 1000 parts of saturated sodium bicarbonate solution, fully stirred, and then the precipitate was taken; the precipitate was fully washed with saturated sodium bicarbonate solution, then centrifugally washed with distilled water, dried, and then a graphene nanosheet layer oxidation intermediate was obtained.

[0039] Comparative Example 1: Graphene oxide

[0040] The fully oxidized graphene oxide was directly provided by a manufacturer (manufacturer: Nanjing Jicang Nanometer Technology Co., Ltd., product name: high-purity graphene oxide, grade: JCGO-100-1-3).

[0041] According to Figure 1 As shown in FIG. 2, the Fourier infrared spectra of the graphene nanosheet layer oxidation intermediates prepared in Example 1 and Example 2 show that the peak positions of the main characteristic peaks of the two are highly coincident, meaning that the molecular structures of the products of the two examples are similar. This shows that the graphene nanosheet layer oxidation intermediate product prepared by the present application is stable in quality and good in product control.

[0042] The graphene nanosheet layer oxidation intermediates obtained in Example 1 and Example 2 were dissolved in acidic hydrogen peroxide solution to obtain graphene oxide. To test the structural differences of the prepared graphene oxide before and after long-term storage (30 days), the following used the transmittance of the solution at the same concentration and the Fourier infrared spectrum to characterize.

[0043] Table 1 shows the transmittance of the graphene oxide of different concentrations before and after 30 days of storage of Comparative Example 1, and the transmittance of the graphene oxide prepared in the examples at the corresponding concentrations before and after 30 days of storage, and the storage condition is at room temperature, in a cool and dry place.

[0044] As shown in Table 1, the commercially available graphene oxide of the comparative example has a significant decrease in transmittance after 30 days of storage. The decrease in transmittance indicates that the layers have agglomerated due to the high surface energy, and the graphene oxide is no longer dispersed in the form of single layers in the solution, resulting in a decrease in specific surface area, thereby inhibiting its properties as a nanomaterial. The graphene oxide prepared in the examples of the present application has no significant change in transmittance before and after 30 days of storage, indicating that the layer dispersion is maintained, and the graphene oxide is still extended in the form of single layers in the solution.

[0045] Table 1 Comparison of the transmittance of the graphene oxide solution obtained before and after 30 days of storage of the examples and the comparative example

[0046]

[0047] Figure 2 The Fourier infrared spectra of the graphene oxide of the comparative example before and after 30 days of storage are shown in FIG. 3. As can be seen from the figure, after 30 days of storage, the structure of the graphene oxide changes significantly, especially the peak at a wave number of 880 (characteristic peak of epoxy group) is significantly weakened and almost disappears after 30 days. The remaining characteristic peaks also appear to weaken to varying degrees, indicating that after 30 days of storage, the structure of the graphene oxide changes significantly, and the functional groups are partially reduced and deteriorated.

[0048] Figure 3 Compared with Figure 4The Fourier infrared spectra of graphene oxide of example 1 and example 2 before and after storage for 30 days are shown respectively, and it can be seen from the figure that the graphene oxide of the example of the application has little difference before and after storage for 30 days, the infrared characteristic peak correspondence is obvious, and the peak intensity is not weakened, so that it is proved that long-term storage will not change the quality of graphene oxide. As can be seen, the graphene nanosheet layer oxidation intermediate of the application can be stored for a long time, and then the functional graphene-based nanomaterial can be obtained by simple means.

[0049] The graphene nanosheet layer oxidation intermediate prepared by the application has stable product control and is easy to synthesize subsequent functional graphene-based nanomaterials, and can be used as raw materials of high-performance graphene-based nanomaterials such as graphene oxide, sulfur-graphene oxide and nitrogen-graphene oxide. In addition, it can be stored for a long time and is easy to transport, which solves the weakness that high-performance graphene-based nanomaterials need to be prepared and used immediately, and paves the way for the realization of large-scale and industrialized application of graphene-based high-performance materials.

Claims

1. A method of preparing a graphene nanoplatelet layer oxidation intermediate, characterized by, The method comprises the following steps: Step 1: 1 part of graphite powder particles is placed in a pure oxygen sealed container, heated to 600-1200℃, and then ultrasonic pulses are emitted into the sealed container for oxidation reaction to prepare oxidized pyrolytic graphite, and the reaction is cooled to room temperature after the reaction is completed; Step 2: the oxidized pyrolytic graphite obtained in step 1 is mixed with 40-100 parts of concentrated sulfuric acid, 1 part of an expanding agent, 1 part of a water absorbing agent, and 2-8 parts of an oxidizing agent for reaction, and the reaction is cooled to room temperature after the reaction is completed; Step 3: the product obtained in step 2 is dropped into a pH stabilizer, stirred, and a precipitate is obtained, which is washed and dried to obtain the graphene nanosheet layer oxidation intermediate.

2. The production method according to claim 1, characterized by, The particle size of the graphite powder particles is 5-1000 μm.

3. The production method according to claim 1, characterized by, The pressure of pure oxygen in the sealed container is 2-3 atmospheres.

4. The method of claim 1, wherein, In step 1, the ultrasonic pulse power is 80-300 W / L, and the emission time is 20-40 min.

5. The preparation method according to claim 1, characterized in that, The expanding agent includes persulfate or a foaming agent.

6. The method of claim 1, wherein, The oxidizing agent includes dichromate, potassium permanganate, perchloric acid, perchlorate, chlorate, nitric acid or nitrate.

7. The preparation method according to claim 1, characterized in that, In step 2, the reaction temperature is 30-50℃, and the reaction time is 2-5h.

8. The method of claim 1, wherein, The pH stabilizer includes a saturated sodium bicarbonate solution, a sodium monohydrogen phosphate solution or a sodium dihydrogen phosphate solution.

9. The graphene nanosheet layer oxidation intermediate prepared by the preparation method according to any one of claims 1-8.

10. The use of the graphene nanosheet layer oxidation intermediate according to claim 9 in the preparation of graphene-based nanomaterials.

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