High-speed turbulence preparation method of porous graphene

Abstract

The invention provides a preparation method of porous graphene, and belongs to the technical field of graphene preparation. The preparation method comprises the following steps: dispersing graphite powder in a solution, carrying out high-speed turbulence treatment on a graphite dispersion liquid, and carrying out centrifugal treatment on the treated dispersion liquid to obtain the porous graphene. According to the invention, turbulent flow and cavitation effects are formed in the high-speed turbulent flow treatment process, and the stripping of the graphite sheet layer is realized by using inertia force, viscous shearing force and Reynolds shearing force generated by the turbulent flow; and high-pressure micro-jet is generated at the collapse moment of the cavitation bubbles and continuously impacts the graphene to form holes. In the preparation process, related flow fields are all full turbulent flow fields, turbulent flow and cavitation effects can be generated by means of high-speed turbulent flow, the preparation process is simple and mild, and the defects that other preparation methods adopted at present are harsh in preparation condition and tedious in preparation process are overcome.

Description

Technical Field

[0001] The invention relates to the technical field of graphene preparation, and in particular to a method for preparing porous graphene. Background Art

[0002] Porous graphene (PG) is a new type of graphene derivative. The porous morphology of PG is the vacancies left by the removal of some graphene carbon atoms from the lattice or transfer to the surface. It is essentially a defect. High-energy particle radiation, chemical treatment and other operations on graphene will lead to the generation of such defects. Making holes in graphene can not only retain the excellent properties of graphene, but also produce many unique properties different from traditional graphene, such as the ability to screen ions and molecules of different sizes, open energy band gaps, tough mechanical properties and ultra-large specific surface area. Therefore, compared with graphene, PG has a wider range of application prospects in the fields of material transportation, electrochemical energy storage, catalysis, etc.

[0003] At present, the main known preparation methods for PG include particle etching, chemical etching, 3D template method and heat treatment method. Among them, although the particle etching method can obtain high-quality PG structure, its operation cost is high and it has limitations in batch preparation; the chemical etching method can achieve batch preparation by using the redox principle, but the use of chemical reagents and the occurrence of redox reactions in the preparation process will introduce other defects in the PG structure, affecting the conductivity and mechanical properties, and the strong acid and strong alkali reagents required for the redox reaction will have adverse effects on the equipment and the environment; the PG structure prepared by the 3D template method has fewer defects and the 3D structure can avoid the agglomeration of PG sheets, but this method requires strict control of harsh environmental conditions such as high temperature and vacuum, and needs further development in batch preparation; the PG structure prepared by the heat treatment method has good adsorption and regeneration, but it is often doped with other elements or compounds.

[0004] Based on the above discussion, it can be seen that the common PG material preparation methods cannot achieve all the advantages in terms of preparation cost, ease of operation, production scale, yield, etc. Therefore, it is particularly important to develop a high-quality PG preparation method with a relatively mild operating environment, one-step mass production, and environmental friendliness. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for preparing porous graphene. The method for preparing porous graphene provided by the present invention has a relatively mild operating environment, can achieve one-step batch production, and is environmentally friendly.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing porous graphene, comprising the following steps:

[0008] dispersing graphite powder in a solution to obtain a graphite dispersion;

[0009] The graphite dispersion is subjected to high-speed turbulence treatment to obtain a treated graphite dispersion, wherein the rotation speed of the high-speed turbulence treatment is greater than 8000 rpm and the time is greater than 30 minutes;

[0010] The treated graphite dispersion is centrifuged to obtain the porous graphene.

[0011] Preferably, the rotation speed of the high-speed turbulent flow treatment is 8000r~50000rpm.

[0012] Preferably, the rotation speed of the high-speed turbulent flow treatment is 18000 rpm.

[0013] Preferably, the high-speed turbulent flow treatment time is 30 minutes to 10 hours.

[0014] Preferably, the high-speed turbulent flow treatment time is 1 hour.

[0015] Preferably, the high-speed turbulence treatment is performed in a high-speed rotating cavitation device, and the high-speed rotating cavitation device comprises an upper blade, a middle blade and a lower blade.

[0016] Preferably, the solution is a water-ethanol mixture, and the volume fraction of ethanol in the water-ethanol mixture is 30% to 70%.

[0017] Preferably, the graphite powder includes one or more of microcrystalline graphite, flake graphite, expandable graphite and highly oriented pyrolytic graphite.

[0018] Preferably, the centrifugal treatment is carried out at a centrifugal speed of 25 to 1600 g and a centrifugal time of 30 to 90 min.

[0019] Preferably, the centrifugal treatment has a centrifugal speed of 64 g and a centrifugal time of 45 min.

[0020] The invention provides a method for preparing porous graphene, comprising the following steps: dispersing graphite powder in a solution to obtain a graphite dispersion; subjecting the graphite dispersion to a high-speed turbulence treatment, wherein the rotation speed of the high-speed turbulence treatment is above 8000 rpm and the time is above 30 minutes; and centrifuging the treated graphite dispersion to obtain the porous graphene.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the preparation process of the present invention, the flow fields involved are all full turbulent fields, and the turbulence and cavitation effects can be generated by means of a simple high-speed rotating cavitation device. The preparation process is simple and gentle, overcoming the shortcomings of other preparation methods currently used, such as harsh preparation conditions and cumbersome preparation processes, and it is easy to achieve batch preparation of few-layer porous graphene with obvious porous morphology.

[0023] 2. Porous graphene is prepared by high-speed turbulence method, and low-boiling point solvents such as water and ethanol are selected. The cavitation effect is strong and the density is high during the preparation process, which has high energy utilization rate. Water and ethanol are non-toxic, and the gas discharged during the reaction is CO2, which is green and pollution-free.

[0024] 3. The porous graphene is prepared by high-speed turbulence method. The required raw material is graphite. This method can directly realize the transformation from graphite to porous graphene, which has the advantage of "one-step method".

[0025] 4. The porous graphene prepared by high-speed turbulence method has obvious porous morphology and a thickness of less than 5 carbon atomic layers.

[0026] The data of the examples show that the porous graphene prepared by the present invention has obvious porous morphology, and porous graphene with 2 to 3 layers can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of preparing porous graphene according to an embodiment of the present invention;

[0028] Figure 2 is a three-dimensional schematic diagram of the high-speed rotating cavitation device used;

[0029] Figure 3 is a two-dimensional schematic diagram of the high-speed rotating cavitation device used;

[0030] Figure 4 This is an atomic force microscope photo of the porous graphene prepared in Example 1;

[0031] Figure 5 This is an atomic force microscope photo of the porous graphene prepared in Example 2;

[0032] Figure 6 This is an atomic force microscope photo of the porous graphene prepared in Example 3;

[0033] Figure 7 This is an atomic force microscope photograph of graphene prepared in comparative example. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing porous graphene, comprising the following steps:

[0035] dispersing graphite powder in a solution to obtain a graphite dispersion;

[0036] The graphite dispersion is subjected to a high-speed turbulent flow treatment, wherein the rotation speed of the high-speed turbulent flow treatment is above 8000 rpm and the time is above 30 minutes;

[0037] The treated graphite dispersion is centrifuged to obtain the porous graphene.

[0038] In the present invention, unless otherwise specified, the raw materials used are all commercially available products in the art.

[0039] The present invention disperses graphite powder in a solution to obtain a graphite dispersion.

[0040] In the present invention, the solution is preferably a water-ethanol mixture, and the volume fraction of ethanol in the water-ethanol mixture is preferably 30% to 70%, more preferably 30%, 50% or 70%.

[0041] In the present invention, the graphite powder preferably includes one or more of microcrystalline graphite, flake graphite, expandable graphite and highly oriented pyrolytic graphite.

[0042] In the present invention, the concentration of graphite in the graphite dispersion is preferably 1 to 5 mg / mL, more preferably 3 mg / mL.

[0043] After obtaining the graphite dispersion, the present invention performs high-speed turbulence treatment on the graphite dispersion, wherein the rotation speed of the high-speed turbulence treatment is above 8000 rpm and the time is above 30 minutes.

[0044] In the present invention, the rotation speed of the high-speed turbulent treatment is preferably 8000-50000 rpm, specifically 12000, 18000 or 27000 rpm; the high-speed turbulent treatment is preferably carried out in a high-speed rotating cavitation device, the function of the high-speed rotating cavitation device is to create high-speed turbulence and high-intensity cavitation conditions for the graphite dispersion; the Reynolds number generated by the high-speed turbulent treatment is greater than 10 4 , the entire flow field is a full turbulent field. The present invention utilizes the turbulence and cavitation effect generated by a high-speed rotating cavitation device to realize the exfoliation of graphite sheets and the construction of porous morphology thereon, and obtains high-quality porous graphene under relatively mild preparation conditions.

[0045] In the present invention, the time of the high-speed turbulent flow treatment is preferably 30 minutes to 10 hours, specifically 0.5, 1 or 2 hours.

[0046] In the present invention, the high-speed rotating cavitation device preferably includes an upper blade, a middle blade and a lower blade. The upper blade is preferably tilted upward, and the lower blade is preferably tilted downward. The angle between the upper blade and the horizontal reference line is preferably 45°, the angle between the middle blade and the horizontal reference line is preferably 0°, and the angle between the lower blade and the horizontal reference line is preferably 60°.

[0047] In the present invention, the number of the upper blades, the middle blades and the lower blades in the high-speed rotating cavitation device is preferably 2.

[0048] Figure 2 It is a three-dimensional schematic diagram of the high-speed rotating cavitation device used in the present invention, Figure 3 It is a two-dimensional schematic diagram of the high-speed rotating cavitation device used in the present invention.

[0049] After obtaining the treated graphite dispersion, the present invention centrifuges the treated graphite dispersion to obtain the porous graphene.

[0050] In the present invention, the centrifugal speed of the centrifugal treatment is preferably 25-1600 g, specifically 64 g, and the centrifugal time is preferably 30-90 min, specifically 45 min.

[0051] After the centrifugation is completed, the present invention preferably collects the obtained supernatant liquid, that is, obtains a stable high-quality porous graphene dispersion liquid, and filters or distills the supernatant liquid to obtain porous graphene powder.

[0052] The present invention has no particular limitation on the specific parameters of the filtration and distillation, and methods well known to those skilled in the art may be used.

[0053] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Figure 1 This is a flowchart of the process of preparing porous graphene according to an embodiment of the present invention.

[0055] The high-speed rotating cavitation device used in the embodiment of the present invention is as follows: Figures 2-3 shown.

[0056] Example 1

[0057] Step 1: Prepare 1000 mL of a mixed solution of deionized water and anhydrous ethanol, with the volume fraction of anhydrous ethanol being 50%. Disperse 3000 mg of flake graphite powder in the prepared mixed solution to obtain a 3 mg / mL graphite dispersion. Pour the graphite dispersion into a high-speed rotating cavitation device.

[0058] Step 2: High-speed turbulence treatment was performed at 18000 rpm for 1 h. The Reynolds number corresponding to the high-speed turbulence was 2.04×10 7 , greater than 10 4 , the flow field is a fully turbulent field;

[0059] Step 3: placing the treated graphite dispersion in a centrifugal device for high-speed centrifugation, with a centrifugal acceleration of 64g and a centrifugal time of 45min;

[0060] Step 4: Collect the supernatant after high-speed centrifugation to obtain a high-quality porous graphene stable dispersion in a mixed solution of deionized water and anhydrous ethanol. According to the atomic force microscope photo, the thickness of the porous graphene is 1.086 nm, that is, 2 to 3 carbon atomic layers;

[0061] Step 5: Filter the porous graphene dispersion to obtain porous graphene powder.

[0062] The atomic force microscope photo of the porous graphene prepared in Example 1 is as follows: Figure 4 shown.

[0063] Example 2

[0064] Step 1: Prepare 1000 mL of a mixed solution of deionized water and anhydrous ethanol, with the volume fraction of anhydrous ethanol being 50%. Disperse 3000 mg of flake graphite powder in the prepared mixed solution to obtain a 3 mg / mL graphite dispersion. Pour the graphite dispersion into a high-speed rotating cavitation device.

[0065] Step 2: High-speed turbulence treatment was performed at 12000 rpm for 0.5 h. The Reynolds number corresponding to the turbulence was 1.36×10 7 , greater than 10 4 , the flow field is a fully turbulent field;

[0066] Step 3: placing the treated graphite dispersion in a centrifugal device for high-speed centrifugation, with a centrifugal acceleration of 64g and a centrifugal time of 45min;

[0067] Step 4: Collect the supernatant after high-speed centrifugation to obtain a high-quality porous graphene stable dispersion in a mixed solution of deionized water and anhydrous ethanol. According to the atomic force microscope photo, the thickness of the porous graphene is 1.535 nm, that is, 3 to 4 carbon atomic layers;

[0068] Step 5: Filter the porous graphene dispersion to obtain porous graphene powder.

[0069] The atomic force microscope photo of the porous graphene prepared in Example 2 is as follows: Figure 5 shown.

[0070] Example 3

[0071] Step 1: Prepare 1000 mL of a mixed solution of deionized water and anhydrous ethanol, with the volume fraction of anhydrous ethanol being 50%. Disperse 3000 mg of flake graphite powder in the prepared mixed solution to obtain a 3 mg / mL graphite dispersion. Pour the graphite dispersion into a high-speed rotating cavitation device.

[0072] Step 2: High-speed turbulence treatment was performed at 27000 rpm for 0.5 h. The Reynolds number corresponding to the turbulence was 3.06×10 7 , greater than 10 4 , the flow field is a fully turbulent field;

[0073] Step 3: placing the treated graphite dispersion in a centrifugal device for high-speed centrifugation, with a centrifugal acceleration of 64g and a centrifugal time of 45min;

[0074] Step 4: Collect the supernatant after high-speed centrifugation to obtain a high-quality porous graphene stable dispersion in a mixed solution of deionized water and anhydrous ethanol. According to the atomic force microscope photo, the thickness of the porous graphene is 1.218 nm, that is, 2 to 3 carbon atomic layers;

[0075] Step 5: Filter the porous graphene dispersion to obtain porous graphene powder.

[0076] The atomic force microscope photo of the porous graphene prepared in Example 3 is as follows: Figure 6 shown.

[0077] Comparative Example

[0078] The same as Example 1, the only difference is that the speed of the high-speed rotating cavitation device is 5000 rpm and the time is 0.5 h.

[0079] The atomic force microscope photo of the graphene prepared in the comparative example is as follows: Figure 7 As shown, compared with the porous graphene of the present invention, it does not have a porous structure.

[0080] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing porous graphene, characterized in that: The following steps are involved: dispersing graphite powder in a solution to obtain a graphite dispersion; The graphite dispersion is subjected to high-speed turbulence treatment to obtain a treated graphite dispersion, wherein the rotation speed of the high-speed turbulence treatment is greater than 8000 rpm and the time is greater than 30 minutes; The treated graphite dispersion is centrifuged to obtain the porous graphene.

2. The preparation method according to claim 1, characterized in that: The rotation speed of the high-speed turbulent flow treatment is 8000-50000 rpm.

3. The preparation method according to claim 2, characterized in that: The rotation speed of the high-speed turbulent flow treatment is 18000 rpm.

4. The preparation method according to claim 1 or 2, characterized in that: The high-speed turbulent flow treatment time is 30 minutes to 10 hours.

5. The preparation method according to claim 4, characterized in that: The high-speed turbulence treatment time is 1 hour.

6. The preparation method according to claim 1, characterized in that: The high-speed turbulence treatment is carried out in a high-speed rotating cavitation device, which includes an upper blade, a middle blade and a lower blade.

7. The preparation method according to claim 1, characterized in that: The solution is a water-ethanol mixture, and the volume fraction of ethanol in the water-ethanol mixture is 30% to 70%.

8. The preparation method according to claim 1, characterized in that: The graphite powder includes one or more of microcrystalline graphite, flake graphite, expandable graphite and highly oriented pyrolytic graphite.

9. The preparation method according to claim 1, characterized in that: The centrifugal treatment has a centrifugal speed of 25 to 1600 g and a centrifugal time of 30 to 90 min.

10. The preparation method according to claim 9, characterized in that: The centrifugal treatment was performed at a centrifugal speed of 64 g and a centrifugal time of 45 min.

Images