CN108373151B - Preparation method of multi-fold hollow graphene oxide microspheres - Google Patents
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Abstract
The invention provides a preparation method of a multi-fold hollow graphene oxide microsphere. The preparation method comprises the following steps: 1) preparing graphene oxide by using graphite as a raw material through a Hummers improvement method, and preparing a graphene oxide aqueous solution; 2) ultrasonically dispersing a graphene oxide aqueous solution uniformly; 3) dropwise adding the uniformly dispersed graphene oxide aqueous solution into the low-temperature liquid to obtain a graphene oxide ice ball; 4) and (3) carrying out freeze drying and centrifugal purification on the graphene oxide ice ball to obtain the multi-fold hollow graphene oxide microsphere. The preparation method of the multi-fold hollow graphene oxide microspheres has the advantages of simple operation process, high efficiency, no need of special or complex reaction equipment, low cost, no additional additive, no need of high-temperature reaction, hollow structure of the prepared graphene oxide microspheres, particle size of 0.5-10 mu m, and large amount of folds distributed on the surface, and is suitable for large-scale industrial production of the multi-fold hollow graphene oxide microspheres.
Description
Technical Field
The invention belongs to the technical field of preparation of graphene oxide microspheres, relates to a preparation method of a multi-fold graphene oxide microsphere, and particularly relates to a preparation method of a multi-fold hollow graphene oxide microsphere.
Background
Since the first report of graphene in 2004, due to its excellent physicochemical properties, researchers from various fields such as physics, chemistry, material science, and biomedicine have attracted attention. Graphene is a crystal with a two-dimensional structure, consisting of a single layer of carbon atoms passing through sp2The material is formed by hybridization to form a two-dimensional structure with a hexagonal honeycomb-shaped lattice, and the unique structure enables the material to have high strength and hardness, huge specific surface area, excellent heat conduction, strong electric conductivity, high carrier mobility and good optical characteristics, so that the material can be widely applied to various fields. Graphene oxide is an important precursor for preparing graphene by a chemical method. The surface of graphene oxide has a certain amount of carboxyl, carbonyl, epoxy and hydroxyl functional groups, which causes the graphene oxide lamellar structure to be changed and defect occurs, thereby showing physicochemical properties different from those of graphene with a uniform structure. The graphene oxide with functional groups can be uniformly dispersed in a plurality of solvents, and can be well applied to the fields of catalysis, dispersing auxiliaries and the like.
However, most of the graphene oxide related in the prior art is a flat sheet structure, which is a characteristic of a typical two-dimensional material. However, the planar sheet structure of the two-dimensional material has a slightly smaller specific surface area than that of the zero-dimensional material and that of the one-dimensional material, which limits further applications in the fields of catalysis, energy storage, microelectronics, etc. Compared with a planar lamellar structure, the specific surface area of graphene oxide with a surface corrugation structure is greatly increased, and therefore, surface corrugation also becomes one of the current research hotspots.
CN105540573A discloses a high-solubility multi-fold dry graphene oxide microsphere, which is formed by folding a single-layer graphene oxide sheet with the size of 1-200 mu m, the diameter of the microsphere is 500 nm-30 mu m, and the density is 0.08-0.2 g/cm3The specific surface area is 10 to 2300m2The carbon-oxygen ratio is 1.8-3, the invention also discloses a preparation method of the high-solubility multi-fold dry graphene oxide microsphere, and the preparation method comprises the following steps: (1) diluting the graphene oxide dispersion liquid prepared by a Hummers method with an organic solvent; the mass ratio of the organic solvent to the graphene oxide dispersion liquid is 1-50: 1; (2) and (3) carrying out atomization drying on the dispersion liquid diluted in the step (1) to obtain the graphene oxide microspheres. According to the invention, the high-solubility multi-fold dry graphene oxide microspheres are obtained by adding an organic solvent into the graphene oxide dispersion to form a mixed dispersion and then carrying out atomization drying, but the method needs a certain temperature to volatilize the solvent, so that the preparation cost is relatively high.
In the prior art, a method for preparing graphene oxide microspheres with wrinkled surfaces is to stack graphene oxide into a complex polyhedral structure by self-assembly so as to form wrinkles, but the reaction components involved in the preparation method are complex, and impurities are easily introduced into the graphene oxide microspheres with excellent adsorbability.
In summary, it is necessary to provide a method for preparing hollow graphene oxide microspheres with surface wrinkles, which has a simple process and does not require an etchant or a high-temperature reaction.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of a multi-fold hollow graphene oxide microsphere, no additional additive is needed, no special or complex reaction equipment is needed, the cost is low, no high-temperature reaction is needed, the prepared graphene oxide microsphere has a hollow structure, the particle size is 0.5-10 mu m, and a large number of folds are distributed on the surface.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a multi-fold hollow graphene oxide microsphere comprises the following steps:
1) preparing graphene oxide by using graphite as a raw material through a Hummers improvement method, and preparing a graphene oxide aqueous solution from the prepared graphene oxide;
2) ultrasonically dispersing the graphene oxide aqueous solution prepared in the step 1) to obtain a uniformly dispersed graphene oxide aqueous solution;
3) dropwise adding the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) into low-temperature liquid to obtain graphene oxide ice balls;
4) and 3) carrying out freeze drying and centrifugal purification on the graphene oxide ice ball obtained in the step 3) to obtain the multi-fold hollow graphene oxide microsphere.
The preparation method comprises the steps of preparing graphene oxide by a Hummers improvement method, preparing a graphene oxide aqueous solution, carrying out ultrasonic dispersion on the prepared graphene oxide aqueous solution to obtain a uniformly dispersed graphene oxide aqueous solution, dropwise adding the uniformly dispersed graphene oxide aqueous solution into a low-temperature liquid to obtain a graphene oxide ice ball, and carrying out freeze drying and centrifugal purification on the graphene oxide ice ball to obtain the multi-fold hollow graphene oxide microsphere. According to the method, other additives are not introduced, impurities are not introduced due to the fact that an etching agent is not added, volatilization of the solvent due to high-temperature reaction is avoided due to the fact that the solvent is not added, and the multi-fold hollow graphene oxide microspheres with a large number of folds on the surfaces and hollow structures are obtained through low-temperature liquid and freeze drying.
In the step 3), the low-temperature liquid is liquid nitrogen or dry ice.
In step 3), the volume of each drop of the uniformly dispersed graphene oxide aqueous solution is 0.01 to 0.1mL, and for example, the volume of each drop of the uniformly dispersed graphene oxide aqueous solution is 0.01mL, 0.02mL, 0.03mL, 0.04mL, 0.05mL, 0.06mL, 0.07mL, 0.08mL, 0.09mL, or 0.1 mL. If the aqueous solution of the graphene oxide is not dripped into the low-temperature liquid drop by drop, spherical graphene oxide ice balls cannot be obtained, the graphene oxide can be cracked due to stress cracking after freeze drying, and complete graphene oxide microspheres cannot be formed.
In the step 4), the freeze drying is vacuum freeze drying; preferably, the temperature of the freeze-drying is-40 to-60 ℃, for example, the temperature of the freeze-drying is-40 ℃, -45 ℃, -50 ℃, -55 ℃, -60 ℃; the freeze drying time is 12-48 h, for example, the freeze drying time is 12h, 15h, 16h, 18h, 20h, 24h, 25h, 30h, 35h, 36h, 40h and 48 h.
In the step 4), the centrifugal purification process comprises the following steps: dispersing the frozen and dried ice balls in a solvent, performing vortex oscillation and centrifugal separation, and drying supernate to obtain the multi-fold hollow graphene oxide microspheres;
preferably, the solvent is one of ethanol and acetone;
preferably, the rotation speed of the centrifugal separation is 800-1500 r/min, for example, the rotation speed of the centrifugal separation is 800r/min, 900r/min, 1000r/min, 1100r/min, 1200r/min, 1300r/min, 1400r/min, 1500 r/min; the time of centrifugal separation is 3-8 min, for example, the time of centrifugal separation is 3min, 4min, 5min, 6min, 7min and 8 min.
Graphene oxide (abbreviated as GO) is generally obtained by oxidizing graphite with strong acid. There are three main methods for preparing graphite oxide: the Brodie method, Staudenmier method and Hummers method. Among them, the Hummers method has relatively good timeliness and safety in the preparation process, and is the most commonly used one at present. The Hummers method adopts potassium permanganate in concentrated sulfuric acid and graphite powder to carry out oxidation reaction to obtain brown graphite flakes with derived carboxylic acid groups at the edges and mainly phenolic hydroxyl groups and epoxy groups on the planes, the graphite flake layer can be stirred and peeled off violently by ultrasonic or high shear to form graphene oxide, and stable and light brown single-layer graphene oxide suspension is formed in water.
Compared with the conventional Hummers method, the Hummers improved method has fewer impurities and reduces NO generated in the reaction2、N2O4And the like.
In the step 1), the Hummers improvement method comprises the following steps: preparing a mixed acid solution by using concentrated sulfuric acid and concentrated phosphoric acid as raw materials, and preparing graphene oxide by using graphite, the mixed acid solution and potassium permanganate as raw materials.
Preferably, the volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid in the mixed acid solution is (8-10): 1, for example, the volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid is 8:1, 9:1, 10:1, preferably 9: 1; the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8), and preferably 1:182.5: 6.
The preparation process of the graphene oxide in the step 1) comprises the following steps:
a) h is to be2SO4And H3PO4Preparing a mixed acid solution according to a volume ratio of (8-10) to 1;
b) taking the flaky graphite and the mixed acid solution to mix in a single-neck flask, and stirring the mixture by magnetic force at room temperature to mix the mixture evenly; placing the single-neck flask with the mixed solution in an ice-water bath, slowly adding potassium permanganate into the single-neck flask, and reacting for 1-2 hours by magnetic stirring, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8);
c) after the reaction is finished, placing the single-neck flask into a medium-temperature constant-temperature water bath kettle, stirring, cooling to room temperature, pouring the reaction liquid into ice water containing 100mL, and dropwise adding hydrogen peroxide after uniform stirring until the solution becomes bright yellow; and after the reaction is finished, respectively using dilute hydrochloric acid, ethanol and water to centrifugally wash the reaction product until the pH value is neutral, and freeze-drying the precipitate to obtain the graphene oxide.
As a preferred scheme, the preparation process of the graphene oxide in the step 1) is as follows:
a) h is to be2SO4And H3PO4According to the volume ratio of (8-1)0) 1, preparing a mixed acid solution;
b) taking the flaky graphite and the mixed acid solution to mix in a single-neck flask, and stirring the mixture by magnetic force at room temperature to mix the mixture evenly; placing the single-neck flask with the mixed solution in an ice-water bath, slowly adding potassium permanganate into the single-neck flask, and reacting for 1-2 hours by magnetic stirring, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8);
c) after the reaction is finished, placing the single-neck flask into a medium-temperature constant-temperature water bath kettle, stirring, cooling to room temperature, pouring the reaction liquid into ice water containing 100mL, and dropwise adding hydrogen peroxide after uniform stirring until the solution becomes bright yellow; and after the reaction is finished, respectively using dilute hydrochloric acid, ethanol and water to centrifugally wash the reaction product until the pH value is neutral, and freeze-drying the precipitate to obtain the graphene oxide.
In the step 1), the molar concentration of the graphene oxide aqueous solution is 0.001-20 mg/mL; the molar concentration of the graphene oxide aqueous solution determines the size of pores, if the molar concentration of the graphene oxide aqueous solution is less than 0.001mg/mL, the pore diameter is too large or the pores are not broken to form incomplete pores, and if the molar concentration of the graphene oxide aqueous solution is more than 20mg/mL, the graphene oxide is agglomerated or cannot form pores; therefore, the molar concentration of the aqueous solution of graphene oxide should be reasonably controlled, for example, the aqueous solution of graphene oxide should have a molar concentration of 0.001mg/mL, 0.005mg/mL, 0.01mg/mL, 0.02mg/mL, 0.05mg/mL, 0.08mg/mL, 0.1mg/mL, 0.2mg/mL, 0.3mg/mL, 0.4mg/mL, 0.5mg/mL, 0.6mg/mL, 0.7mg/mL, 0.8mg/mL, 0.9mg/mL, 1mg/mL, 2mg/mL, 3mg/mL, 4mg/mL, 5mg/mL, 6mg/mL, 7mg/mL, 8mg/mL, 9mg/mL, 10mg/mL, 11mg/mL, 12mg/mL, 13mg/mL, 14mg/mL, 15mg/mL, 16mg/mL, 17mg/mL, 18mg/mL, 19mg/mL, 20 mg/mL.
Preferably, the molar concentration of the graphene oxide aqueous solution is 1-10 mg/mL.
In the step 2), ultrasonic dispersion is performed to avoid agglomeration of graphene oxide, so that pore formation in the step 3) and the step 4) is facilitated, and the frequency of ultrasonic dispersion is 15-25 KHz, for example, the frequency of ultrasonic dispersion is 15KHz, 16KHz, 17KHz, 18KHz, 19KHz, 20KHz, 21KHz, 22KHz, 23KHz, 24KHz and 25 KHz; the ultrasonic dispersion time is 150-200 min, for example, the ultrasonic dispersion time is 150min, 160min, 170min, 180min, 190min, 200 min.
The particle size of the multi-fold hollow graphene oxide microspheres is 0.5-10 μm, for example, the particle size of the multi-fold hollow graphene oxide microspheres is 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm.
As a preferred embodiment of the present invention, a preparation method of a multi-fold hollow graphene oxide microsphere comprises the following steps:
1) preparing a mixed acid solution by using concentrated sulfuric acid and concentrated phosphoric acid as raw materials, and preparing graphene oxide by using graphite, the mixed acid solution and potassium permanganate as raw materials, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1:182.5:6, and preparing the prepared graphene oxide into a graphene oxide aqueous solution with the molar concentration of 0.001-20 mg/mL;
2) ultrasonically dispersing the graphene oxide aqueous solution prepared in the step 1) for 150-200 min at the frequency of 15-25 KHz to obtain a uniformly dispersed graphene oxide aqueous solution;
3) dropwise adding the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) into a low-temperature liquid to obtain graphene oxide ice balls, wherein the volume of each drop of the uniformly dispersed graphene oxide aqueous solution is 0.01-0.1 mL;
4) carrying out freeze drying on the graphene oxide ice balls obtained in the step 3) at the temperature of-40 to-60 ℃ for 12-48 h, dispersing the freeze-dried ice balls in a solvent, carrying out centrifugal separation at the rotating speed of 800-1500 r/min for 3-8 min after vortex oscillation, and drying the supernatant to obtain the multi-fold hollow graphene oxide microspheres.
Compared with the prior art, the invention has the beneficial effects that:
(1) the preparation method of the multi-fold hollow graphene oxide microsphere provided by the invention has the advantages that no additional additive is needed, and no etching agent is needed to avoid introducing impurities; the method has the advantages that high-temperature reaction is not needed, the solvent volatilization caused by the high-temperature reaction is avoided without adding the solvent, the uniformly dispersed graphene oxide aqueous solution is dripped into low-temperature liquid drop by drop, the prepared graphene oxide microspheres have hollow structures through freeze drying, a large number of folds are distributed on the surfaces of the graphene oxide microspheres, and the particle size of the prepared multi-fold hollow graphene oxide microspheres is 0.5-10 mu m.
(2) The preparation method of the multi-fold hollow graphene oxide microspheres, disclosed by the invention, is simple in operation process, high in preparation efficiency, low in cost and suitable for large-scale industrial production of the multi-fold hollow graphene oxide microspheres, and special or complex reaction equipment is not required.
Drawings
Fig. 1 is a scanning electron microscope image of graphene oxide selected in embodiment 1 of the present invention;
fig. 2 is a scanning electron microscope image of a multi-folded hollow graphene oxide microsphere prepared in example 1 of the present invention;
FIG. 3 is a scanning electron micrograph of a sample prepared according to example 2 of the present invention after freeze-drying;
FIG. 4 is a scanning electron micrograph of a sample prepared according to example 3 of the present invention after freeze-drying;
fig. 5 is a scanning electron microscope image of a multi-fold hollow graphene oxide microsphere prepared by centrifugal separation in example 4 of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Unless otherwise specified, various starting materials of the present invention are commercially available or prepared according to conventional methods in the art.
Example 1
Graphene oxide (shown in figure 1) prepared by a Hummers improved method is selected to prepare a graphene oxide aqueous solution. 10mg of graphene oxide and 10mL of deionized water are added into a conical flask, and the mixture is magnetically stirred for 1h at room temperature to prepare a 1mg/mL graphene oxide aqueous solution. And then placing the preliminarily mixed graphene oxide aqueous solution in an ice water bath, and performing ultrasonic dispersion for 3 hours by using a cell crushing instrument. Then, dropwise adding the uniformly mixed graphene oxide aqueous solution into a small test tube filled with liquid nitrogen by using a dropper, wherein the volume of each drop of graphene oxide aqueous solution is 0.02mL, the graphene oxide aqueous solution can be rapidly cooled and solidified to form brown small spheres, performing freeze drying at-40 ℃ for 48 hours, dispersing the freeze-dried ice spheres in a solvent, performing centrifugal separation at the rotating speed of 800r/min for 8min after vortex oscillation, and drying the supernatant to obtain multi-folded hollow graphene oxide microspheres, wherein a scanning electron microscope image of the graphene oxide microspheres prepared in the embodiment is shown in fig. 2. As can be seen from fig. 2, the graphene oxide microspheres prepared in this embodiment have many folds on the surface.
Example 2
30mg of graphene oxide and 10mL of deionized water are added into a conical flask, and the mixture is magnetically stirred for 1h at room temperature to prepare a 3mg/mL graphene oxide aqueous solution. And then placing the preliminarily mixed graphene oxide aqueous solution in an ice water bath, and performing ultrasonic dispersion for 3 hours by using a cell crushing instrument. Then, the uniformly mixed graphene oxide aqueous solution is dropwise added into a small test tube filled with liquid nitrogen by a dropper, the volume of each graphene oxide aqueous solution is 0.05mL, the graphene oxide aqueous solution is rapidly cooled and solidified to form brown spheres, and the brown spheres are subjected to freeze drying at the temperature of-50 ℃ for 24 hours, wherein a scanning electron microscope image of a sample prepared by freeze drying in the embodiment is shown in fig. 3. As can be seen from fig. 3, after freeze-drying, the formed graphene oxide hollow microspheres are adsorbed on the surface of the porous graphene oxide with pores, that is, at this time, the prepared sample contains both porous graphene oxide sheets and wrinkled graphene oxide microspheres. Dispersing the frozen and dried ice ball into a solvent, carrying out centrifugal separation for 5min at a rotating speed of 1000r/min after vortex oscillation, and drying the supernatant to obtain the multi-folded hollow graphene oxide microspheres.
Example 3
50mg of graphene oxide and 10mL of deionized water were added to a conical flask, and the mixture was magnetically stirred at room temperature for 1 hour to prepare a 5mg/mL graphene oxide aqueous solution. And then placing the preliminarily mixed graphene oxide aqueous solution in an ice water bath, and performing ultrasonic dispersion for 3 hours by using a cell crushing instrument. And then dropwise adding the uniformly mixed graphene oxide aqueous solution into a small test tube filled with liquid nitrogen by using a dropper, wherein the volume of each drop of graphene oxide aqueous solution is 0.03mL, the graphene oxide aqueous solution can be rapidly cooled and solidified to form a brown small ball, carrying out freeze drying on the brown small ball at the temperature of-60 ℃ for 12h, and showing a scanning electron microscope image of the freeze-dried ice ball sample as shown in figure 4, wherein the surface of the graphene oxide microspheres in the sample has a plurality of folds.
Example 4
Dispersing the freeze-dried sample of the example 3 in absolute ethyl alcohol according to the proportion of 1: 10; carrying out centrifugal separation on the dispersion liquid at the speed of 1000rpm/min, and purifying the graphene oxide microspheres in the freeze-dried product; and (3) dropping the centrifuged supernatant on a silicon wafer, placing the silicon wafer in an oven at 45 ℃ for drying, and observing that the surface of the graphene oxide microsphere shown in fig. 5 has wrinkles and has a hollow structure under a scanning electron microscope.
Comparative example
50mg of graphene oxide and 10mL of deionized water were added to a conical flask, and the mixture was magnetically stirred at room temperature for 1 hour to prepare a 5mg/mL graphene oxide aqueous solution. And then placing the preliminarily mixed graphene oxide aqueous solution in an ice water bath, and performing ultrasonic dispersion for 3 hours by using a cell crushing instrument. And then dripping 0.5mL of uniformly mixed graphene oxide aqueous solution into a small test tube filled with liquid nitrogen by a dropper, cooling the graphene oxide aqueous solution, carrying out freeze drying on the graphene oxide aqueous solution at the temperature of-60 ℃ for 12 hours, and scanning the freeze-dried sample to obtain complete graphene oxide microspheres.
The preparation method of the multi-fold hollow graphene oxide microsphere disclosed by the invention has the advantages that no additional additive is needed, no high-temperature reaction is needed, the prepared graphene oxide microsphere can reach a hollow structure, a large number of folds are distributed on the surface of the graphene oxide microsphere, and the particle size of the prepared multi-fold hollow graphene oxide microsphere is 0.5-10 mu m. The preparation method of the multi-fold hollow graphene oxide microspheres, disclosed by the invention, is simple in operation process, high in preparation efficiency, low in cost and suitable for large-scale industrial production of the multi-fold hollow graphene oxide microspheres, and special or complex reaction equipment is not required.
The above examples are only intended to illustrate the detailed process of the present invention, and the present invention is not limited to the above detailed process, i.e., it is not intended that the present invention necessarily depends on the above detailed process for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (16)
1. The preparation method of the multi-fold hollow graphene oxide microspheres is characterized by comprising the following steps:
1) preparing graphene oxide by using graphite as a raw material through a Hummers improvement method, and preparing a graphene oxide aqueous solution with a molar concentration of 0.001-20 mg/mL from the prepared graphene oxide;
2) ultrasonically dispersing the graphene oxide aqueous solution prepared in the step 1) to obtain a uniformly dispersed graphene oxide aqueous solution;
3) dropwise adding the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) into a low-temperature liquid to obtain graphene oxide ice balls, wherein the volume of each drop of the uniformly dispersed graphene oxide aqueous solution is 0.01-0.1 mL;
4) freeze-drying and centrifugally purifying the graphene oxide ice ball obtained in the step 3) to obtain the multi-fold hollow graphene oxide microsphere with the particle size of 0.5-10 microns.
2. The method according to claim 1, wherein in step 3), the cryogenic liquid is liquid nitrogen.
3. The method according to claim 1 or 2, wherein in the step 4), the freeze-drying is vacuum freeze-drying.
4. The preparation method according to claim 1 or 2, wherein the temperature of the freeze-drying in the step 4) is-40 ℃ to-60 ℃, and the time of the freeze-drying is 12-48 h.
5. The method of claim 1 or 2, wherein in step 1), the Hummers improvement method comprises the steps of: preparing a mixed acid solution by using concentrated sulfuric acid and concentrated phosphoric acid as raw materials, and preparing graphene oxide by using graphite, the mixed acid solution and potassium permanganate as raw materials.
6. The preparation method according to claim 5, wherein the volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid in the mixed acid solution is (8-10): 1.
7. The production method according to claim 5, wherein the volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid in the mixed acid solution is 9: 1.
8. The preparation method of claim 5, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8).
9. The preparation method according to claim 5, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1:182.5: 6.
10. The preparation method according to claim 1, wherein the graphene oxide in step 1) is prepared by:
a) h is to be2SO4And H3PO4Preparing a mixed acid solution according to a volume ratio of (8-10) to 1;
b) taking the flaky graphite and the mixed acid solution to mix in a single-neck flask, and stirring the mixture by magnetic force at room temperature to mix the mixture evenly; placing the single-neck flask with the mixed solution in an ice-water bath, slowly adding potassium permanganate into the single-neck flask, and reacting for 1-2 hours by magnetic stirring, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8);
c) after the reaction is finished, placing the single-neck flask into a medium-temperature constant-temperature water bath kettle, stirring, cooling to room temperature, pouring the reaction liquid into ice water containing 100mL, and dropwise adding hydrogen peroxide after uniform stirring until the solution becomes bright yellow; and after the reaction is finished, respectively using dilute hydrochloric acid, ethanol and water to centrifugally wash the reaction product until the pH value is neutral, and freeze-drying the precipitate to obtain the graphene oxide.
11. The preparation method according to claim 1, wherein in the step 1), the graphene oxide aqueous solution has a molar concentration of 1-10 mg/mL.
12. The preparation method according to claim 1, wherein in the step 2), the frequency of the ultrasonic dispersion is 15 to 25KHz, and the time of the ultrasonic dispersion is 150 to 200 min.
13. The preparation method according to claim 1, wherein in the step 4), the centrifugal purification process comprises: and dispersing the frozen and dried ice ball in a solvent, carrying out vortex oscillation and centrifugal separation, taking supernatant and drying to obtain the multi-fold hollow graphene oxide microsphere.
14. The method according to claim 13, wherein the solvent is one of ethanol and acetone.
15. The method according to claim 13, wherein the rotation speed of the centrifugal separation is 800 to 1500r/min, and the time of the centrifugal separation is 1 to 8 min.
16. The method of claim 1, comprising the steps of:
1) preparing a mixed acid solution by using concentrated sulfuric acid and concentrated phosphoric acid as raw materials, and preparing graphene oxide by using graphite, the mixed acid solution and potassium permanganate as raw materials, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8), and preparing the prepared graphene oxide into a graphene oxide aqueous solution with the molar concentration of 0.001-20 mg/mL;
2) ultrasonically dispersing the graphene oxide aqueous solution prepared in the step 1) for 150-200 min at the frequency of 15-25 KHz to obtain a uniformly dispersed graphene oxide aqueous solution;
3) dropwise adding the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) into a low-temperature liquid to obtain graphene oxide ice balls, wherein the volume of each drop of the uniformly dispersed graphene oxide aqueous solution is 0.01-0.1 mL;
4) carrying out freeze drying on the graphene oxide ice balls obtained in the step 3) at the temperature of-40 to-60 ℃ for 12-48 h, dispersing the freeze-dried ice balls in a solvent, carrying out centrifugal separation at the rotating speed of 800-1500 r/min for 1-8 min after vortex oscillation, and drying the supernatant to obtain the multi-fold hollow graphene oxide microspheres.
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| CN110681549B (en) * | 2019-09-24 | 2021-07-13 | 西安交通大学 | High-heat-conductivity super-hydrophobic flue gas condensation heat exchange surface and preparation method and device thereof |
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| CN107344855A (en) * | 2017-07-25 | 2017-11-14 | 东莞市联洲知识产权运营管理有限公司 | A kind of multistage hole foamed ceramics of the microballoon containing porous graphene and preparation method thereof |
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| CN103420352A (en) * | 2013-08-08 | 2013-12-04 | 四川大学 | High-fluoride-content graphite fluoride and preparation method thereof |
| CN106810629A (en) * | 2015-12-02 | 2017-06-09 | 中国石油天然气股份有限公司 | A kind of spherical graphite alkene/magnesium-supported polyethylene catalysts of halogenation |
| CN107344855A (en) * | 2017-07-25 | 2017-11-14 | 东莞市联洲知识产权运营管理有限公司 | A kind of multistage hole foamed ceramics of the microballoon containing porous graphene and preparation method thereof |
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