CN108394897B - Macroscopic preparation method of porous graphene oxide - Google Patents
Macroscopic preparation method of porous graphene oxide Download PDFInfo
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- CN108394897B CN108394897B CN201810516090.8A CN201810516090A CN108394897B CN 108394897 B CN108394897 B CN 108394897B CN 201810516090 A CN201810516090 A CN 201810516090A CN 108394897 B CN108394897 B CN 108394897B
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Abstract
The invention provides a macroscopic preparation method of porous graphene oxide. The macro preparation method of the porous graphene oxide 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 to obtain a uniformly dispersed graphene oxide aqueous solution; 3) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution to obtain graphene oxide ice blocks; 4) and (3) carrying out freeze drying on the graphene oxide ice blocks to obtain the porous graphene oxide. The macroscopic preparation method of the porous graphene oxide has the advantages of simple operation process and low cost, does not need to add extra additives such as an etching agent and the like, is uniform in prepared porous graphene oxide component, can control the pore diameter within the range of 1-20 mu m, is large in pore diameter distribution range, and is suitable for macroscopic industrial production of the porous graphene oxide.
Description
Technical Field
The invention belongs to the technical field of preparation of porous graphene oxide, and relates to a macro preparation method of porous graphene oxide.
Background
Graphene is a crystal with a two-dimensional structure, consisting of a single layer of carbon atoms passing through sp2Hybridized to form a two-dimensional hexagonal honeycomb lattice structure. Therefore, the single-layer graphene material has a theoretical thickness (0.335nm) of only one carbon atom and is the thinnest substance in the two-dimensional materials known at present. Due to the unique crystal structure of graphene, the exceptional physical properties of graphene, such as high strength and hardness, huge specific surface area, excellent heat conduction, strong conductivity, high carrier mobility and good optical properties, are determined. Due to the excellent characteristics of graphene, graphene can be widely applied to the fields of flexible electronic devices, high-precision gas sensors, biosensors, catalytic conversion, composite materials, batteries, super capacitors and the like.
Due to the fact that high Van der Waals force and strong pi-pi acting force exist between the single graphene layers, the graphene layers and the graphene layers are stacked and easily agglomerated in water, and cannot be dispersed, and the characteristic of large specific surface area cannot be fully exerted. In order to effectively solve the problems of graphene agglomeration and processing in water, graphene is chemically oxidized and stripped, and the obtained graphene oxide has amphipathy, so that the graphene solution has processability and is more suitable for industrial manufacturing. In addition, the porous modification of the graphene oxide can obviously improve the utilization rate of the surface area of the graphene oxide, so that the advantages of the two-dimensional layered material are fully exerted.
Graphene Oxide (GO) 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 the functional group can be uniformly dispersed in a plurality of solvents, and can be well applied to the fields of catalysis, dispersing auxiliaries and the like.
The existing preparation method of porous graphene oxide comprises electron beam etching and MnO2Chemical etching, ultraviolet radiation photoreaction and the like. However, the electron beam etching method and the ultraviolet radiation photoreaction method involve complicated and tedious processes, and MnO2Impurities can be introduced by the chemical etching method, so that the subsequent application of the porous graphene oxide of the novel graphene derivative material is severely limited.
CN107720743A discloses a controllable preparation method of graphene oxide with a two-dimensional porous structure: adding ammonium persulfate into the graphene oxide dispersion liquid, wherein the mass ratio of the ammonium persulfate to the graphene oxide is 5-11: 1, heating and refluxing, and naturally cooling to room temperature to obtain the graphene oxide nano material with the two-dimensional porous structure. The specific surface area and the pore volume of the two-dimensional porous graphene oxide obtained by the method are obviously increased compared with those of the graphene oxide, but impurities such as ammonium sulfate and the like are introduced in the preparation process, and the pore diameter of the prepared porous graphene oxide is not easy to control.
CN105692598A discloses a preparation method of lamellar porous graphene oxide, which comprises the following steps: 1) dissolving graphene oxide and a binder in water to prepare a precursor solution; 2) placing the precursor solution in a container to carry out bidirectional freezing reaction to obtain an intermediate product; the bottom of the container is provided with a wedge-shaped device; 3) freeze-drying the intermediate product obtained in the step 2) to remove the solvent, so as to obtain the lamellar porous graphene oxide. The preparation method can prepare graphene oxide with different interlayer spacing and pore size and with a lamellar porous structure, and the size, porosity and pore appearance of the lamellar porous structure can be adjusted in a large range.
CN102963886A discloses a preparation method of porous graphene oxide, which comprises the following specific steps: (1) preparing graphite oxide by using natural crystalline flake graphite as a raw material by using a hunmers method; (2) dispersing the obtained graphite oxide at 10-50 ℃ for 10-30 min by using a magnetic stirrer to prepare a uniformly mixed suspension; (3) weighing prepared graphite oxide suspension liquid 0.1-1 mg/ml, adding the graphite oxide suspension liquid into a clean cuboid electrolytic tank, and then placing graphite electrodes on two inner sides of the electrolytic tank; (4) and stripping the graphite oxide into single-layer graphene oxide by using an alternating electric field, wherein the stripping voltage is 10-30V, the stripping frequency is 50-5000 Hz, and the action time is 30-120 min. According to the method for preparing the porous graphene oxide in a stripping manner, the graphite oxide is stripped by using the alternating electric field, compared with the traditional ultrasonic stripping method, the method has the advantages of no noise, high yield and the like, but the preparation of the porous graphene oxide needs to be provided with special reaction equipment, and is not beneficial to the mass production of the porous graphene oxide.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a macroscopic preparation method of porous graphene oxide, which is simple in operation process, low in cost, free of adding extra additives such as etching agents and the like, uniform in prepared porous graphene oxide component, large in pore size distribution range and suitable for macroscopic industrial production of porous graphene oxide, and the pore size can be controlled within the range of 1-20 microns.
In order to achieve the purpose, the invention adopts the following technical scheme:
a macro preparation method of porous graphene oxide 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) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) to obtain graphene oxide ice blocks;
4) and 3) carrying out freeze drying on the graphene oxide ice blocks obtained in the step 3) to obtain the porous graphene oxide.
According to the method, graphene oxide is prepared by a Hummers improvement method, a graphene oxide aqueous solution is prepared and subjected to ultrasonic dispersion to obtain a uniformly dispersed graphene oxide aqueous solution, a low-temperature liquid is slowly poured into the uniformly dispersed graphene oxide aqueous solution to obtain graphene oxide ice blocks, and the graphene oxide ice blocks are subjected to freeze drying to obtain porous graphene oxide. According to the method, other additives are not introduced, impurities are not introduced due to the addition of an etching agent, the solvent is prevented from being volatilized due to high-temperature reaction due to the addition of the solvent, the porous graphene oxide is obtained through low-temperature liquid and freeze drying, the process is simpler, the production efficiency is higher, special or complex reaction equipment is not needed, the cost is lower, the prepared porous graphene oxide is uniform in component, the pore diameter can be controlled within the range of 1-20 mu m, the pore diameter distribution range is large, and the method is suitable for the macro industrial production of the porous graphene oxide; the prepared porous graphene oxide has the characteristic of multiple functional groups, is convenient for subsequent functional modification, and can be used in the fields of electrocatalysis, supercapacitors, lithium ion batteries, organic catalysis and the like.
In the step 3), the low-temperature liquid is gaseous at normal temperature; preferably, the cryogenic liquid is liquid nitrogen or dry ice.
In the step 3), the rate of slowly pouring the uniformly dispersed graphene oxide aqueous solution into the low-temperature liquid is 3-100 mL/min, for example, the pouring rate is 3, 10mL/min, 20mL/min, 30mL/min, 40mL/min, 50mL/min, 60mL/min, 70mL/min, 80mL/min, 90mL/min, 100mL/min, preferably 40-60 mL/min. If the pouring rate of the low-temperature liquid is too high and the pouring rate of the low-temperature liquid is higher than 100mL/min, the pore structure of the prepared porous graphene oxide is incomplete, and the layered graphene is crushed under the gasification impact force of liquid nitrogen to form a fibrous material; if the introduction rate of the low-temperature liquid is too slow, the low-temperature liquid is quickly vaporized, the purpose of quickly cooling cannot be achieved, and the graphene oxide cannot form holes, so that the pouring rate of the low-temperature liquid needs to be reasonably controlled.
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.
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 H3PO4By volumePreparing a mixed acid solution in a 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 specific preparation process of the graphene oxide in the step 1) is as follows:
a) h is to be2SO4And H3PO4Preparing a mixed acid solution according to the volume ratio of 9: 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 1h by magnetic stirring, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1:182.5: 6;
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 pore diameter of the porous graphene oxide is 1-20 μm, for example, the pore diameter of the porous graphene oxide is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm.
As a preferred scheme of the present invention, a macro preparation method of porous graphene oxide 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) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) at the speed of 3-1000 mL/min to obtain graphene oxide ice blocks;
4) carrying out freeze drying on the graphene oxide ice blocks obtained in the step 3) at the temperature of-40 to-60 ℃ for 12 to 48 hours to obtain the porous graphene oxide.
Compared with the prior art, the invention has the beneficial effects that:
(1) the macroscopic preparation method of the porous graphene oxide has few implementation steps, does not need any etching agent to avoid introducing impurities, avoids volatilizing the solvent by high-temperature reaction without adding the solvent, can prepare the porous graphene oxide by slowly pouring low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution and freeze-drying, and has the advantages of simpler process, higher production efficiency, no need of special or complex reaction equipment and lower cost.
(2) According to the macroscopic preparation method of the porous graphene oxide, the prepared porous graphene oxide is uniform in components, the pore diameter can be controlled within the range of 1-20 mu m, the pore diameter distribution range is large, and the method is suitable for macroscopic industrial production of the porous graphene oxide.
(3) According to the macroscopic preparation method of the porous graphene oxide, extra additives such as an etching agent and the like are not required to be added, the prepared porous graphene oxide contains polyfunctional groups such as-OH, -COOH, C-O-C and-C ═ O, the subsequent functional modification is facilitated, and the method can be used in the fields of electrocatalysis, supercapacitors, lithium ion batteries, organic catalysis and the like.
Drawings
Fig. 1 is a transmission electron microscope image of graphene oxide prepared in example 1 of the present invention;
FIG. 2 is a Fourier transform infrared (FT-IR) spectrum of graphene oxide prepared in example 1 of the present invention;
fig. 3 is a scanning electron microscope image of porous graphene oxide prepared in example 2 of the present invention;
fig. 4 is a scanning electron microscope image of porous graphene oxide prepared in example 3 of the present invention;
fig. 5 is a scanning electron microscope image of porous graphene oxide prepared in example 4 of the present invention.
Fig. 6 is a scanning electron microscope image of porous graphene oxide prepared in comparative example 1 of the present invention.
Fig. 7 is a scanning electron microscope image of porous graphene oxide prepared in comparative example 2 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.
The macroscopic preparation method of the porous graphene oxide 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) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) to obtain graphene oxide ice blocks;
4) and 3) carrying out freeze drying on the graphene oxide ice blocks obtained in the step 3) to obtain the porous graphene oxide.
Example 1
Preparing graphene oxide by first preparing H2SO4And H3PO4Mixing acid solution according to the volume ratio of 9: 1. 1g of flaky graphite and 100mL of mixed acid solution are mixed in a single-neck flask, and the mixture is stirred magnetically at room temperature to be mixed uniformly. And (3) placing the single-neck flask with the mixed solution under an ice-water bath, slowly adding proper amount of potassium permanganate into the single-neck flask, and reacting for 1 hour by magnetic stirring. After the reaction is finished, the single-neck flask is placed in a medium-temperature constant-temperature water bath kettle and stirred for a certain time. Cooling to room temperature, pouring into ice water containing 100mL, stirring, and dropwise adding hydrogen peroxideUntil the solution turned bright yellow. After the reaction is finished, the reaction product is respectively washed by diluted hydrochloric acid, ethanol and water in a centrifugal mode until the pH value is neutral, and the precipitate is frozen and dried to obtain the graphene oxide.
The transmission electron microscope image of the graphene oxide prepared in this embodiment is shown in fig. 1, and it can be seen that the prepared graphene oxide is a micron-sized large-sheet layered graphene oxide.
The infrared spectroscopic analysis of the prepared graphene oxide was performed, and the result is shown in a fourier transform infrared spectroscopy (FT-IR) chart of graphene oxide in fig. 2. As can be seen from FIG. 2, 3354cm-1A wider and stronger absorption peak is nearby, which belongs to the stretching vibration peak of O-H; at 1730cm-1Where represents the stretching vibration peak of C ═ O on the carboxyl group; at 1624cm-1The absorption peak is the bending vibration absorption peak belonging to C-OH; at 1048cm-1The peak of (a) is a vibration absorption peak of C-O-C; thus, it is explained that the prepared graphene oxide has groups such as-OH, -COOH, C-O-C, and-C ═ O.
Example 2
Taking 0.002g of graphene oxide, preparing 2mL of graphene oxide aqueous solution with the concentration of 1mg/mL, and carrying out ultrasonic treatment for 150min at the frequency of 20kHz to obtain the uniformly dispersed graphene oxide solution. And then slowly pouring normal-temperature gaseous liquid nitrogen into the graphene oxide solution at the speed of 30mL/min until the solution is completely frozen into ice blocks, and freeze-drying the ice blocks at the temperature of-40 ℃ for 24 hours to obtain the graphene oxide with micron pores. A scanning electron microscope image of the porous graphene oxide prepared in this embodiment is shown in fig. 3, and as can be seen from fig. 3, the pore size of the porous graphene oxide prepared in this embodiment is about 10 μm.
Example 3
Taking 0.006g of graphene oxide, preparing 2mL of graphene oxide aqueous solution with the concentration of 3mg/mL, and carrying out ultrasonic treatment for 180min at the frequency of 18kHz to obtain the uniformly dispersed graphene oxide solution. And then slowly pouring normal-temperature gaseous liquid nitrogen into the graphene oxide solution at the speed of 50mL/min until the solution is completely frozen into ice blocks, and freeze-drying the ice blocks at the temperature of-50 ℃ for 48 hours to obtain the graphene oxide with micron pores. The scanning electron microscope image of the porous graphene oxide prepared in this embodiment is shown in fig. 4, and as can be seen from fig. 4, the pore size of the porous graphene oxide prepared in this embodiment is 4 to 10 μm.
Example 4
Taking 0.01g of graphene oxide, preparing 2mL of graphene oxide aqueous solution with the concentration of 5mg/mL, and carrying out ultrasonic treatment for 200min at the frequency of 15kHz to obtain the uniformly dispersed graphene oxide solution. And then slowly pouring liquid nitrogen into the graphene oxide solution at the speed of 50mL/min until the solution is completely frozen into ice blocks, and freeze-drying the ice blocks at the temperature of-60 ℃ to obtain the graphene oxide with micron pores. The scanning electron microscope image of the porous graphene oxide prepared in the present embodiment is shown in fig. 5, and as can be seen from fig. 5, the pore size of the porous graphene oxide prepared in the present embodiment is about 2 to 5 μm.
Example 5
Taking 0.02g of graphene oxide, preparing 2mL of graphene oxide aqueous solution with the concentration of 10mg/mL, and carrying out ultrasonic treatment for 150min at the frequency of 25kHz to obtain the uniformly dispersed graphene oxide solution. And then, slowly pouring liquid nitrogen into the graphene oxide solution at a speed of about 80mL/min until the solution is completely frozen into ice blocks, and freeze-drying the ice blocks at a temperature of-50 ℃ to obtain the graphene oxide with micron pores, wherein the pore size of the porous graphene oxide prepared by the embodiment is about 1-5 microns.
Example 6
0.02g of graphite oxide is taken to prepare 2mL of solution with the concentration of 20mg/mL, and the solution is subjected to ultrasonic treatment for 150min at the frequency of 25kHz to obtain the uniformly dispersed graphene oxide solution. And then slowly pouring liquid nitrogen into the graphene oxide solution at a speed of about 100mL/min until the solution is completely frozen into ice blocks, and freeze-drying the ice blocks at a temperature of-50 ℃ to obtain the graphene oxide with micron pores, wherein the pore size of the porous graphene oxide prepared by the embodiment is about 1-5 microns.
Comparative example 1
0.02g of graphite oxide is taken to prepare 2mL of solution with the concentration of 5mg/mL, and the solution is subjected to ultrasonic treatment for 150min at the frequency of 25kHz to obtain the uniformly dispersed graphene oxide solution. Then, liquid nitrogen is rapidly poured into the graphene oxide solution at a speed of about 10mL/s until the solution is completely frozen into ice blocks, and freeze drying is carried out at a temperature of-50 ℃ to obtain the graphene oxide with micron pores, wherein the porous graphene oxide prepared in the comparative example has an incomplete pore structure, the layered graphene is crushed under the gasification impact force of the liquid nitrogen to form a fibrous material, and a scanning electron microscope image is shown in FIG. 6.
Comparative example 2
0.02g of graphite oxide is taken to prepare 2mL of solution with the concentration of 5mg/mL, and the solution is subjected to ultrasonic treatment for 150min at the frequency of 25kHz to obtain the uniformly dispersed graphene oxide solution. Then, liquid nitrogen is very slowly poured into the graphene oxide solution at the speed of about 3mL/min until the solution is completely frozen into ice blocks, and freeze drying is carried out at the temperature of-50 ℃ to obtain the graphene oxide with micron pores, wherein the graphene oxide prepared by the comparative example has an obvious pore structure and still maintains the layered structure of the graphene oxide, and a scanning electron microscope image is shown as fig. 7.
The macro preparation method of the porous graphene oxide has few implementation steps, can prepare the porous graphene oxide without any etching agent to avoid introducing impurities, is simpler in process, higher in production efficiency, free from special or complex reaction equipment and lower in cost; the prepared porous graphene oxide has the characteristics of large specific surface area and higher polyfunctional group, is convenient for subsequent functional modification, and can be used in the fields of electrocatalysis, supercapacitors, lithium ion batteries, organic catalysis and the like.
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. A macro preparation method of porous graphene oxide 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 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) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) to obtain graphene oxide ice blocks; the low-temperature liquid is gaseous at normal temperature;
4) freezing and drying the graphene oxide ice blocks obtained in the step 3) to obtain the porous graphene oxide;
in the step 3), the rate of slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution is 3-100 mL/min.
2. The macro-preparation method according to claim 1, wherein in step 3), the cryogenic liquid is liquid nitrogen.
3. The macro-preparation method according to claim 1, wherein in the step 3), the slow pouring rate of the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution is 40-60 mL/min.
4. The macro-preparation method according to claim 1, wherein in step 4), the freeze-drying is vacuum freeze-drying.
5. The macro-preparation method according to claim 1, wherein the temperature of the freeze-drying in step 4) is-40 to-60 ℃, and the time of the freeze-drying is 12 to 48 hours.
6. The macro-preparation method according to claim 1, 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.
7. The macro-preparation method according to claim 6, wherein the volume ratio of concentrated sulfuric acid to concentrated phosphoric acid in the mixed acid solution is (8-10): 1.
8. The macro-production method according to claim 7, wherein the volume ratio of concentrated sulfuric acid to concentrated phosphoric acid in the mixed acid solution is 9: 1.
9. The macro-preparation method of claim 6, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1 (180-185) to (5-8).
10. The macro-preparation method according to claim 9, wherein the mass ratio of the graphite to the mixed acid solution to the potassium permanganate is 1:182.5: 6.
11. The macro preparation method according to claim 6, wherein the graphene oxide in step 1) is prepared by 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.
12. The macro preparation method according to claim 1, wherein in step 1), the graphene oxide aqueous solution has a molar concentration of 0.001-20 mg/mL.
13. The macro-preparation method according to claim 12, wherein in step 1), the graphene oxide aqueous solution has a molar concentration of 1 to 10 mg/mL.
14. The macro-preparation method according to claim 1, wherein in step 2), the frequency of ultrasonic dispersion is 15 to 25KHz, and the time of ultrasonic dispersion is 150 to 200 min.
15. The macro-preparation method according to claim 1, wherein the pore size of the porous graphene oxide is 1 to 20 μm.
16. The macro-preparation method according to any one of claims 1 to 15, wherein the macro-preparation method comprises 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) slowly pouring the low-temperature liquid into the uniformly dispersed graphene oxide aqueous solution prepared in the step 2) at a rate of 3-100 mL/min to obtain graphene oxide ice blocks; the low-temperature liquid is gaseous at normal temperature;
4) carrying out freeze drying on the graphene oxide ice blocks obtained in the step 3) at the temperature of-40 to-60 ℃ for 12 to 48 hours to obtain the porous graphene oxide.
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| CN109824033B (en) * | 2019-03-06 | 2021-01-29 | 华南理工大学 | Method for preparing high-thermal-conductivity graphene film at low cost |
| CN111450810B (en) * | 2020-04-07 | 2022-05-27 | 武夷学院 | Method for improving pore structure of material |
| CN111591978A (en) * | 2020-05-29 | 2020-08-28 | 成都理工大学 | Preparation method for preparing graphene air filter element on large scale |
| CN113648850B (en) * | 2021-09-01 | 2022-10-21 | 北京理工大学 | Preparation method of MXene/reduced porous graphene oxide (r-HGO) composite membrane with high flux and high removal rate |
| CN114014306B (en) * | 2021-12-15 | 2022-08-09 | 陇东学院 | Preparation method and application of oxygen-enriched layered porous graphene |
| CN114408911B (en) * | 2022-01-17 | 2022-11-04 | 哈尔滨工业大学 | Preparation method of graphene-based aerogel with ultra-fast light-thermal response |
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