CN101591014B - Method for realizing large-scale preparation of monolayer oxidized graphene - Google Patents

Abstract

The invention relates to a method used for realizing large-scale preparation of monolayer oxidized graphene. The method comprises the following steps: oxidizing natural crystalline flake graphite by an oxidant to obtain oxidized graphite; after ultrasonic stripping, carrying out filtration to remove unreacted graphite and obtain the aqueous solution of oxidized graphene; and adding a flocculatingagent to obtain oxidized graphene solid after settlement, filtration and drying. The method can easily separate the oxidized graphene solid from aqueous dispersion solution through flocculating settlement, thereby realizing large-scale preparation of graphene; moreover, the method has cheap and accessible raw materials, easy operation, simple process and good reproducibility, and is suitable for large-scale industrial production. The monatomic oxidized graphene prepared by the method can be used as flake reinforced phase of composite materials to prepare materials with high mechanical property and barrier property; moreover, the oxidized graphene can also be used for preparing fingerprint collecting materials, and the like. Graphene, namely the reduction product of the oxidized graphene can be used for constructing two-dimensional photoelectron components such as nano computer chips, solar battery electrodes and field effect transistors and the like.

Description

A method for large-scale preparation of single-layer graphene oxide

technical field

The invention relates to a method for large-scale preparation of single-layer graphene oxide. the

Background technique

In 2004, Geim, a professor of physics at the University of Manchester in the United Kingdom, peeled off and observed a single-layer graphene crystal (Geim, A.K.et al.Science, 306, 666 (2004)) with a very simple method, which has aroused new interest in the scientific community. A round of "carbon" craze. The theoretical specific surface area of graphene is as high as 2600m2/g (Chae, H.K.etal.Nature, 427,523 (2004)), has outstanding thermal conductivity (3000W/(m K)) and mechanical properties (1060GPa) (Schadler, L.S. et al.Appl Phys Lett, 73, 3842(1998)), and high-speed electron mobility (15000cm2/(V s)) at room temperature (Zhang, Y.et al.Nature, 438, 201(2005)). The special structure of graphene makes it have a series of properties such as perfect quantum tunneling effect, half-integer quantum Hall effect and never-disappearing electrical conductivity (Novoselov, K.S. et al. Nature, 38, 197 (2005)). These unique properties make it have broad application prospects in the fields of materials science and electronics. the

At present, the preparation methods of graphene include: mechanical exfoliation method, chemical vapor deposition method, intercalation method and oxidation-reduction method. Among them, the yield of graphene obtained by the first two methods is low, and the product of the intercalation method contains a large number of multilayer graphene, which to a certain extent limits its application in various fields, especially in composite materials. The oxidation-reduction method uses natural flake graphite as a raw material to prepare graphene starting from the preparation of graphene oxide. The world is rich in graphite minerals, and my country is also a country with high graphite production. Therefore, this method has laid the foundation for the large-scale preparation of graphene from the aspect of raw materials. Therefore, the preparation of graphene oxide from graphite is a strategic starting point for large-scale graphene synthesis. Moreover, compared with expensive fullerenes and carbon nanotubes, graphene oxide is cheap and easy to obtain raw materials; graphene oxide also contains a large number of -OH and -COOH groups, which can be easily modified chemically , is expected to be a high-quality filler for polymer nanocomposites. the

The oxidation-reduction method mainly uses a strong oxidant to oxidize natural flake graphite to obtain graphene oxide, and then reduces to obtain graphene. However, the graphene oxide obtained by this method is a two-dimensional sheet-like structure with good film-forming properties and good dispersibility in water. separate from. Especially for large-scale industrial preparation and treatment, these methods have high cost and low efficiency, and are not suitable for popularization and application. Therefore, exploring a simple, applicable, cost-effective method for preparing a large amount of graphene oxide, so as to solve the large-scale preparation of graphene, is of great value to realize the wide application of graphene. the

Contents of the invention

The object of the present invention is to aim at the above-mentioned present situation, and aims to provide a method for preparing single-layer graphene oxide with low raw material cost, easy operation, simple process, good reproducibility, and large-scale industrialization. the

The realization mode of the object of the present invention is, a kind of method for preparing monolayer graphene oxide on a large scale, concrete steps are as follows:

① Graphite Oxidation: Use 2g-500g of natural flake graphite as raw material, oxidize with an oxidizing agent, after oxidizing for 72-100 hours, wash and filter the oxide with 1 liter of deionized water, wash until neutral, and dry to obtain graphite oxide ,

Described oxidizing agent is the composition of the mixed acid of 35 milliliters of concentrated sulfuric acid and 18 milliliters of concentrated nitric acid and other reagents, and other reagents are potassium chlorate, potassium permanganate, phosphorus pentoxide, potassium persulfate, one or more in hydrogen peroxide The combination, the addition amount of other reagents is 10 grams -22 grams,

② Dispersion and stripping: Add the graphite oxide solid after deacidification and washing to deionized water immediately to dilute to a concentration of 0.5 g/L, use ultrasonic waves to disperse and strip for 0.5 hours to 10 hours, then filter unreacted graphite, collect the filtrate, and obtain Aqueous solution of graphene oxide, unreacted graphite repeat steps ① and ② operation,

③Flocculation and sedimentation: add flocculant in the graphene oxide aqueous solution according to the amount of 5 g to 50 g/L graphene oxide aqueous solution to make the graphene oxide settle down, then filter, freeze-dry the filter cake to obtain graphene oxide solid ,

The flocculant is one or a combination of potassium hydroxide, sodium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, potassium chloride, sodium chloride, sodium sulfate, potassium iodide or polyacrylamide. the

The present invention can easily separate the graphene oxide solid from its aqueous dispersion through flocculation and sedimentation, thereby realizing the large-scale preparation of graphene; the raw material cost is cheap and easy to obtain, the operation is easy, the process is simple, and the reproducibility is good. Large-scale industrial production is possible. the

The monoatomic graphene oxide prepared by the present invention can be used as a flaky reinforcing phase of composite materials to prepare materials with high mechanical properties and barrier properties; it can be used to make fingerprint collection materials and the like. Its reduction product - graphene, can be used to construct two-dimensional optoelectronic components such as nanoscale computer chips, solar cell electrodes and field effect transistors, and has extremely important practical application value. the

Description of drawings

Figure 1 is a schematic diagram of the process flow for large-scale preparation of graphene oxide,

Fig. 2 is the photo of flocculation step in the preparation graphene oxide process, wherein a is the aqueous solution of graphene oxide; B is the photo of graphene oxide sedimentation after adding flocculant; C is the graphene oxide solid after suction filtration washing, in c The inserted picture is the obtained graphene oxide solid dispersed in water,

Figure 3a and b are low-resolution and high-resolution scanning electron microscope images of field emission of single atomic layer graphene oxide,

Figure 4a, b are high-resolution transmission low-resolution, high-resolution electron microscope images of monoatomic layer graphene oxide,

Figure 5a, b, c, d are atomic force microscope pictures and cross-sectional analysis of single atomic layer graphene oxide with a thickness of 0.730nm and 0.826nm,

Fig. 6 is the X-ray diffraction spectrogram of monoatomic layer graphene oxide,

Fig. 7 is a Fourier transform infrared spectrum of monoatomic layer graphene oxide. the

Detailed ways

With reference to Fig. 1, the specific steps of the present invention are, oxidize natural flake graphite with oxidizing agent, obtain graphite oxide, after ultrasonic stripping, filter and remove unreacted graphite, obtain the aqueous solution of graphene oxide, add flocculant, through sedimentation, filter , and obtain graphene oxide solid after drying. the

The oxidizing agent is preferably a combination of concentrated sulfuric acid, concentrated nitric acid mixed acid and other reagents, and the other reagents are preferably one or a combination of potassium chlorate, potassium permanganate, and phosphorus pentoxide. The optimum oxidation time of the oxidizing agent is 72 hours to 96 hours. The optimal time for ultrasonic dispersion and stripping is 1 hour to 2 hours. The flocculant is preferably one or a combination of potassium hydroxide, sodium hydroxide, hydrochloric acid, potassium chloride, and sodium chloride. the

The graphene oxide prepared by the present invention is composed of carbon atoms, has a small-sized single-layer flake-like structure with an area of square micrometers, and is dark brown powder by naked eyes. Field emission scanning electron microscope photos (as shown in Figure 3a, b), high-resolution transmission electron microscope photos in Figure 4a, b, combined with atomic force microscope photos in Figure 5a, b show graphene oxide with a thin sheet structure, and its thickness is zero A few nanometers, the thickness of a single atomic layer. The X-ray diffraction spectrum is shown in Figure 6, showing the diffraction peaks of graphene oxide: 2θ=10.12° and the diffraction peaks of single-layer graphene oxide structure: 2θ=29°, 30.8°. The Fourier transform infrared spectrum is shown in Figure 7. It can be seen that the characteristic peaks of some groups are produced by the oxidation process. The peaks are C-O: 1053cm-1, C-O-C: 1280cm-1, C-OH: 1385cm-1, and C=O: 1723cm-1. The peak around 1631cm-1 is the skeleton vibration of graphene. the

Below, the present invention will be described in more detail in conjunction with the accompanying drawings and embodiments. the

Embodiment 1, the first step, preparation of graphite oxide: 2 grams of natural graphite flakes were dispersed under stirring into the mixed acid of 35 milliliters of concentrated sulfuric acid and 18 milliliters of concentrated nitric acid which were stirred and cooled in an ice bath for 15 minutes. Slowly add potassium chlorate 22g then, whole reaction system keeps open, and is equipped with tail gas absorption device. The reaction lasted 96 hours. After the reaction was finished, the mixture was washed with 1 liter of deionized water and filtered until neutral. the

The second step, dispersing and peeling: add the washed graphite oxide to deionized water immediately, dilute to a concentration of 0.5 g/L, and use ultrasonic waves to disperse and peel for 1 hour after dilution. Then filter and remove unreacted graphite, collect filtrate, obtain the aqueous solution of graphene oxide as shown in Figure 2a, the solution in the small beaker is: the solution after adding 50 milliliters of deionized water dilutions in the 10 milliliters of large beakers, from Fig. It can be seen that graphene oxide is well dispersed in water. the

The third step, flocculation and sedimentation, filtration, and drying: add 5 grams of sodium hydroxide solution to the aqueous solution of graphene oxide as a flocculant, and the graphene oxide will immediately precipitate and settle as flocs. After standing still, the graphene oxide will completely settle down . Finally, 2.3 grams of graphene oxide solids were obtained after filtration and drying (as shown in Figure 2b, c). the

Embodiment 2, by the preparation method of embodiment 1, just described oxidizing agent is 10 grams of potassium permanganate, obtain the result shown in Figure 3,4,5,6,7 equally. the

Embodiment 3, by the preparation method of embodiment 1, just described oxygenant is 15 grams of potassium persulfate, obtain the result shown in Figure 3,4,5,6,7 equally. the

Embodiment 4, by the preparation method of embodiment 1, just described oxidizing agent is 10 gram potassium permanganate and 13 milliliters of hydrogen peroxide, obtain the result shown in Figure 3,4,5,6,7 equally. the

Embodiment 5, by the preparation method of embodiment 1, just described oxidizing agent is 10 gram potassium permanganate and 1.7 gram phosphorus pentoxide, obtain the result shown in Figure 3,4,5,6,7 equally. the

Embodiment 6 is by the preparation method of embodiment 1, just described oxidizing agent is 10 gram potassium permanganate and 1.7 gram potassium persulfate, obtain the result shown in Figure 3,4,5,6,7 equally. the

Example 7, according to the preparation method of Example 1, the oxidation time was 72 hours, and the results shown in Figures 3, 4, 5, 6, and 7 were also obtained. the

Example 8, according to the preparation method of Example 1, the ultrasonic stripping time is 0.5 hours, and the results shown in Figures 3, 4, 5, 6, and 7 are also obtained. the

Example 9, according to the preparation method of Example 1, the flocculant is hydrochloric acid solution, and the results shown in Figure 2b and c are also obtained. the

Example 10, according to the preparation method of Example 1, the flocculant is a sulfuric acid solution, and the results shown in Figure 2b and c are also obtained. the

Example 11. According to the preparation method of Example 1, the flocculant is nitric acid solution, and the results shown in Fig. 2B and C are also obtained. the

Example 12. According to the preparation method of Example 1, the flocculant is potassium hydroxide solution, and the results shown in Figure 2b and c are also obtained. the

Example 13. According to the preparation method of Example 1, the flocculant is potassium chloride solution, and the results shown in Figure 2b and c are also obtained. the

Example 14. According to the preparation method of Example 1, the flocculant is sodium chloride solution, and the results shown in Figure 2b and c are also obtained. the

Example 15. According to the preparation method of Example 1, the flocculant is sodium sulfate solution, and the results shown in Figure 2b and c are also obtained. the

Example 16. According to the preparation method of Example 1, the flocculant is potassium iodide solution, and the results shown in Figure 2b and c are also obtained. the

Example 17. According to the preparation method of Example 1, the flocculant is polyacrylamide, and the results shown in Figure 2b and c are also obtained. the

Example 18. According to the preparation method of Example 1, except that the flocculant was replaced by a combination of potassium hydroxide and sodium chloride, the results shown in Figure 2b and c were also obtained. the

Example 19. According to the preparation method of Example 1, the flocculant is a composition of hydrochloric acid and sodium chloride, and the ratio of hydrochloric acid and sodium chloride is 1:1. The results shown in Figure 2b and c are also obtained. the

Example 20, according to the preparation method of Example 1, 10 grams of natural flake graphite was dispersed into the mixed acid of 35 milliliters of concentrated sulfuric acid and 18 milliliters of concentrated nitric acid under stirring, and the same obtained as shown in Figures 3, 4, 5, 6, and 7. the result of. the

Example 21, according to the preparation method of Example 1, 50 grams of natural flake graphite was dispersed into the mixed acid of 35 milliliters of concentrated sulfuric acid and 18 milliliters of concentrated nitric acid under stirring, and the same obtained as shown in Figures 3, 4, 5, 6, and 7. the result of. the

Example 22, according to the preparation method of Examples 1 to 15, 500 grams of natural graphite flakes were dispersed into the mixed acid of 35 milliliters of concentrated sulfuric acid and 18 milliliters of concentrated nitric acid under stirring, the oxidation time was 100 hours, and the ultrasonic stripping time was 10 hours. The amount of flocculant used was 50 g/L graphene oxide aqueous solution, and the results shown in Fig. 2b, c and Fig. 3, 4, 5, 6, 7 were also obtained. the

Claims (5)

1. the method for a realizing large-scale preparation of monolayer oxidized graphene is characterized in that concrete steps are as follows:

1. graphite oxidation: with 2 grams-500 gram natural flake graphites is raw material, uses the oxygenant oxidation, and oxidation is after 72 hours-100 hours, and oxide compound is washed till neutrality with 1 liter of deionized water wash suction filtration, obtains graphite oxide after the drying,

Described oxygenant is nitration mixture and other combination of agents thing of 35 milliliters of vitriol oils and 18 milliliters of concentrated nitric acids, other reagent is one or more the combination in Potcrate, potassium permanganate, Vanadium Pentoxide in FLAKES, Potassium Persulphate, the hydrogen peroxide, the dosage of other reagent is 10 grams-22 grams

2. disperse to peel off: the oxidation graphite solid after depickling is washed joins immediately and is diluted to concentration in the deionized water is 0.5 grams per liter, disperseed to peel off 0.5 hour to 10 hours with ultrasonic wave, filter unreacted graphite then, collect filtrate, obtain the aqueous solution of graphene oxide, unreacted graphite repeating step is 2. operation 1.

3. flocculating settling: in the aqueous solution of graphene oxide, add flocculation agents, graphene oxide is settled down, filter then, obtain the graphene oxide solid after the filter cake lyophilize by 5 grams to the amount of 50 grams per liter graphite oxide aqueous solutions,

Described flocculation agent is one or more the combination in potassium hydroxide, sodium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, Repone K, sodium-chlor, sodium sulfate, potassiumiodide or the polyacrylamide.

2. press the method for the described a kind of realizing large-scale preparation of monolayer oxidized graphene of claim 1, it is characterized in that oxygenant is the vitriol oil, concentrated nitric acid nitration mixture and combination of agents thing, reagent is one or more the combination in Potcrate, potassium permanganate, the Vanadium Pentoxide in FLAKES.

3. by the method for the described a kind of realizing large-scale preparation of monolayer oxidized graphene of claim 1, the oxidization time that it is characterized in that described oxygenant is 72 hours to 96 hours.

4. by the method for the described a kind of realizing large-scale preparation of monolayer oxidized graphene of claim 1, it is characterized in that described dispersion splitting time is 1 hour to 2 hours.

5. by the method for the described a kind of realizing large-scale preparation of monolayer oxidized graphene of claim 1, it is characterized in that flocculation agent is one or more the combination in potassium hydroxide, sodium hydroxide, hydrochloric acid, Repone K, the sodium-chlor.

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