A high-speed turbulent flow method for the production of porous graphene

Abstract

The application provides a preparation method of porous graphene, and belongs to the technical field of graphene preparation.The graphite powder is dispersed in a solution, high-speed turbulent flow treatment is conducted on the graphite dispersion liquid, and centrifugal treatment is conducted on the treated dispersion liquid to obtain the porous graphene.In the high-speed turbulent flow treatment process, turbulent flow and cavitation effect are formed, inertial force, viscous shear force and Reynolds shear force generated by the turbulent flow are utilized, and the graphite sheet layer is peeled off;high-pressure microjet is generated in the instant of collapse of cavitation bubbles, and the graphene is continuously impacted to form holes.In the preparation process, all the flow fields involved are full turbulent flow fields, the turbulent flow and cavitation effect can be generated by means of high-speed turbulent flow, the preparation process is simple and mild, and the defects of other preparation methods, such as harsh preparation conditions and complicated preparation process, are overcome.

Description

Technical Field

[0001] This invention relates to the field of graphene preparation technology, and in particular to a method for preparing porous graphene. Background Technology

[0002] Porous graphene (PG) is a novel derivative of graphene. The porous morphology of PG consists of vacancies left by the removal or transfer of some carbon atoms from the graphene lattice to the surface; essentially, these are defects. High-energy particle irradiation and chemical treatments of graphene can induce these defects. Creating pores in graphene not only preserves its excellent properties but also produces many unique properties different from traditional graphene, such as the ability to sieve ions and molecules of different sizes, open band gaps, robust mechanical properties, and an extremely large specific surface area. Therefore, compared to graphene, PG has broader application prospects in areas such as mass transport, electrochemical energy storage, and catalysis.

[0003] Currently, known methods for preparing photopolymer (PG) mainly include particle etching, chemical etching, 3D template method, and thermal treatment. While particle etching can yield high-quality PG structures, its high operating cost limits its mass production capabilities. Chemical etching, utilizing the redox principle, can achieve mass production, but the use of chemical reagents and the occurrence of redox reactions can introduce defects into the PG structure, affecting conductivity and mechanical properties. Furthermore, the strong acids and bases required for redox reactions can adversely affect equipment and the environment. 3D template method produces PG structures with fewer defects, and the 3D structure prevents PG sheet aggregation; however, this method requires strict control of harsh environmental conditions such as high temperature and vacuum, and its mass production needs further development. Thermal treatment produces PG structures with good adsorption and regenerability, but often results in the doping of other elements or compounds.

[0004] In summary, common PG material preparation methods cannot simultaneously achieve optimal results in terms of preparation cost, ease of operation, production scale, and yield. Therefore, it is particularly important to develop a high-quality PG preparation method that has a relatively mild operating environment, enables one-step mass production, and is environmentally friendly. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing porous graphene. The method for preparing porous graphene provided by this invention operates in a relatively mild environment, enables one-step mass production, and is also environmentally friendly.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

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

[0008] Graphite powder is dispersed in a solution to obtain a graphite dispersion.

[0009] The graphite dispersion was subjected to high-speed turbulence treatment to obtain the treated graphite dispersion. The high-speed turbulence treatment was carried out at a speed of 8000 rpm or more and for a time of 30 min or more.

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

[0011] Preferably, the rotational speed of the high-speed turbulence treatment is 8000r to 50000rpm.

[0012] Preferably, the rotational speed of the high-speed turbulence treatment is 18,000 rpm.

[0013] Preferably, the high-speed turbulence treatment time is 30 min to 10 h.

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

[0015] Preferably, 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.

[0016] Preferably, the solution is a water-ethanol mixture, wherein 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 centrifugation speed is 25–1600 g and the centrifugation time is 30–90 min.

[0019] Preferably, the centrifugation speed is 64g and the centrifugation time is 45min.

[0020] This 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 high-speed turbulence treatment, wherein the high-speed turbulence treatment speed is above 8000 rpm and the time is above 30 min; and centrifuging the treated graphite dispersion to obtain the porous graphene.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. In the preparation process of this invention, the flow field involved is a fully turbulent flow field. Turbulence and cavitation effects can be generated by a simple high-speed rotating cavitation device. The preparation process is simple and mild, overcoming the shortcomings of other preparation methods currently used, such as harsh preparation conditions and complicated preparation processes. It is easy to achieve the batch preparation of few-layer porous graphene with obvious porous morphology.

[0023] 2. Porous graphene was prepared using a high-speed turbulent flow method, with low-boiling-point solvents water and ethanol. The preparation process has a large cavitation effect and high density, resulting in high energy utilization. Moreover, water and ethanol are non-toxic, and the gas emitted during the reaction is CO2, which is green and pollution-free.

[0024] 3. Porous graphene can be prepared using a high-speed turbulent flow method. The required raw material is graphite. This method can directly realize the transformation from graphite to porous graphene and has the advantage of being a "one-step" method.

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

[0026] Data from the examples show that the porous graphene prepared by the present invention has a distinct porous morphology and can obtain porous graphene with 2 to 3 layers. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the process of preparing porous graphene according to an embodiment of the present invention.

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

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

[0030] Figure 4 An atomic force microscope image of the porous graphene prepared in Example 1;

[0031] Figure 5 An atomic force microscope image of the porous graphene prepared in Example 2;

[0032] Figure 6 An atomic force microscope image of the porous graphene prepared in Example 3;

[0033] Figure 7 An atomic force microscope image of graphene prepared for comparison. Detailed Implementation

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

[0035] Graphite powder is dispersed in a solution to obtain a graphite dispersion.

[0036] The graphite dispersion was subjected to high-speed turbulence treatment, wherein the high-speed turbulence treatment speed was above 8000 rpm and the time was above 30 min;

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

[0038] Unless otherwise specified, all raw materials used in this invention are commercially available products in the field.

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

[0040] In this 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 this invention, the graphite powder preferably includes one or more of microcrystalline graphite, flake graphite, expandable graphite, and highly oriented pyrolytic graphite.

[0042] In this 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 subjectes the graphite dispersion to high-speed turbulence treatment, wherein the high-speed turbulence treatment speed is above 8000 rpm and the time is above 30 min.

[0044] In this invention, the rotational speed of the high-speed turbulence treatment is preferably 8000–50000 rpm, specifically 12000, 18000, or 27000 rpm; the high-speed turbulence treatment is preferably carried out in a high-speed rotating cavitation device, the function of which is to create high-speed turbulence and high-intensity cavitation conditions for the graphite dispersion; the Reynolds number generated by the high-speed turbulence treatment is greater than 10. 4 The entire flow field is a fully turbulent flow field. This invention utilizes the turbulence and cavitation effects generated by a high-speed rotating cavitation device to achieve the exfoliation of graphite sheets and the construction of porous morphologies on them, obtaining high-quality porous graphene under relatively mild preparation conditions.

[0045] In this invention, the high-speed turbulence treatment time is preferably 30 min to 10 h, specifically 0.5, 1 or 2 h.

[0046] In this invention, the high-speed rotating cavitation device preferably includes an upper blade, a middle blade, and a lower blade. The upper blade is preferably inclined upwards, the lower blade is preferably inclined downwards, 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 this invention, the number of upper blades, middle blades and lower blades in the high-speed rotating cavitation device is preferably 2.

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

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

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

[0051] After the centrifugation process is completed, the present invention preferably collects the supernatant to obtain a stable, high-quality porous graphene dispersion. The supernatant is then filtered or distilled to obtain porous graphene powder.

[0052] The present invention does not impose any special limitations on the specific parameters of the filtration and distillation, and any method known to those skilled in the art can be used.

[0053] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

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

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

[0056] Example 1

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

[0058] Step 2: Perform high-speed turbulence treatment at 18000 rpm for 1 hour. The Reynolds number corresponding to this high-speed turbulence is 2.04 × 10⁻⁶. 7 greater than 10 4 The flow field is a fully turbulent flow field;

[0059] Step 3: Place the treated graphite dispersion in a centrifuge and centrifuge at high speed for 45 minutes with a centrifugation acceleration of 64 g.

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

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

[0062] An atomic force microscope image of the porous graphene prepared in Example 1 is shown below. Figure 4 As shown.

[0063] Example 2

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

[0065] Step 2: Perform high-speed turbulence treatment at 12000 rpm for 0.5 hours. The Reynolds number corresponding to this turbulence is 1.36 × 10⁻⁶. 7 greater than 10 4 The flow field is a fully turbulent flow field;

[0066] Step 3: Place the treated graphite dispersion in a centrifuge and centrifuge at high speed for 45 minutes with a centrifugation acceleration of 64 g.

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

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

[0069] An atomic force microscope image of the porous graphene prepared in Example 2 is shown below. Figure 5 As shown.

[0070] Example 3

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

[0072] Step 2: Perform high-speed turbulence treatment at 27,000 rpm for 0.5 hours. The Reynolds number corresponding to this turbulence is 3.06 × 10⁻⁶. 7 greater than 10 4 The flow field is a fully turbulent flow field;

[0073] Step 3: Place the treated graphite dispersion in a centrifuge and centrifuge at high speed for 45 minutes with a centrifugation acceleration of 64 g.

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

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

[0076] An atomic force microscope image of the porous graphene prepared in Example 3 is shown below. Figure 6 As shown.

[0077] Comparative Example

[0078] Same as in Example 1, except that the rotational speed of the high-speed rotating cavitation device is 5000 rpm and the time is 0.5 h.

[0079] Atomic force microscope images of graphene prepared in a comparative manner are shown below. Figure 7 As shown, it does not have a porous structure compared to the porous graphene of the present invention.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing porous graphene, characterized in that, Includes the following steps: Graphite powder is dispersed in a solution to obtain a graphite dispersion; the solution is a water-ethanol mixture. The graphite dispersion was subjected to high-speed turbulence treatment to obtain the treated graphite dispersion. The high-speed turbulence treatment was carried out at a speed of 18,000 rpm for 1 hour. The treated graphite dispersion was centrifuged to obtain the porous graphene. 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. The upper blade is inclined upward, the lower blade is inclined downward, the angle between the upper blade and the horizontal reference line is 45°, the angle between the middle blade and the horizontal reference line is 0°, and the angle between the lower blade and the horizontal reference line is 60°.

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

3. 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.

4. The preparation method according to claim 1, characterized in that, The centrifugal acceleration for the centrifugation process is 25~1600g, and the centrifugation time is 30~90min.

5. The preparation method according to claim 4, characterized in that, The centrifugal acceleration for the centrifugation process was 64g, and the centrifugation time was 45min.

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