CN110577210B - Preparation method of graphene and graphene derivative powder - Google Patents
Preparation method of graphene and graphene derivative powder Download PDFInfo
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- CN110577210B CN110577210B CN201810581205.1A CN201810581205A CN110577210B CN 110577210 B CN110577210 B CN 110577210B CN 201810581205 A CN201810581205 A CN 201810581205A CN 110577210 B CN110577210 B CN 110577210B
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Abstract
The invention provides a preparation method of graphene and graphene derivative powder, which comprises the following steps: s1) adding a graphene aqueous solution or a graphene derivative aqueous solution into liquid nitrogen to obtain solidified graphene or solidified graphene derivative; s2) carrying out vacuum freeze drying on the solidified graphene or the solidified graphene derivative to obtain graphene powder or graphene derivative powder. Compared with the prior art, the method has the advantages that the graphene aqueous solution or the graphene derivative is treated by liquid nitrogen and then is dried in vacuum, so that the irreversible superposition and agglomeration of graphene and the graphene derivative lamellar are effectively avoided, and the obtained graphene and graphene derivative powder is easy to disperse.
Description
Technical Field
The invention belongs to the technical field of graphene, and particularly relates to a preparation method of graphene and graphene derivative powder.
Background
Gein was first prepared and observed in 2004 as a monolayer of graphene, thereby raising the research hot-melt of graphene materials. Graphene is the thinnest and toughest material found at present, and has high electric conductivity and heat conductivity, so that the graphene plays a great role in a plurality of fields such as electrochemistry, biomedicine and the like.
Since graphene was found, various methods of preparing graphene have been developed. The preparation methods commonly used at present comprise a micromechanical stripping method, an epitaxial growth method, a chemical vapor deposition CVD method, a graphite oxide reduction method and the like.
The micro-mechanical stripping method is to press the high-orientation pyrolytic graphite sheet onto other surfaces by using a transparent adhesive tape to strip for multiple times, and finally obtain single-layer or multi-layer graphene. The method is simple to operate, high in sample quality, and is a main method for preparing single-layer high-quality graphene at present. But the controllability is poor, the prepared graphene has small size and large uncertainty, and meanwhile, the efficiency is low, the cost is high, and the graphene is not suitable for large-scale production.
CVD is considered to be the most promising method for preparing high-quality large-area graphene, and is the most potential method for industrially producing graphene films. The specific process is as follows: hydrocarbon methane, ethanol and the like are introduced to the surfaces of the metal substrates Cu and Ni heated at high temperature, the metal substrates Cu and Ni are cooled after the reaction lasts for a certain time, a plurality of layers or single-layer graphene can be formed on the surfaces of the substrates in the cooling process, and carbon atoms are contained in the process to dissolve and diffuse on the substrates to grow. The method is similar to a metal catalytic epitaxial growth method, and has the advantages that the method can be carried out at a lower temperature, so that the energy consumption in the preparation process can be reduced, and the graphene and the substrate can be easily separated by a chemical corrosion metal method, thereby being beneficial to the subsequent processing treatment of the graphene.
The reduction of graphite oxide is also considered to be one of the best methods for preparing graphene at present. The method is simple to operate and low in preparation cost, and graphene can be prepared on a large scale, so that the method becomes an effective way for preparing the graphene. In addition, the method has the advantage that the functionalized graphene-graphene oxide with wide application prospect can be produced first. The specific operation process is that firstly, strong oxidant concentrated sulfuric acid, concentrated nitric acid, potassium permanganate and the like are used for oxidizing graphite into graphite oxide, in the oxidation process, oxygen-containing functional groups are inserted between graphite layers, so that the interlayer distance of the graphite is increased, then, after ultrasonic treatment for a period of time, single-layer or multi-layer graphene oxide can be formed, and then, strong reducing agents hydrazine hydrate, sodium borohydride and the like are used for reducing the graphene oxide, so that graphene dispersion liquid is obtained.
At present, graphene dispersion liquid is commonly used for preparing graphene powder, and conventional preparation methods comprise filtration, rotary evaporation and the like, but the methods are easy to cause irreversible superposition and agglomeration of graphene sheets and difficult to disperse.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing graphene and its derivative powder, wherein the graphene and its derivative powder prepared by the method are easy to disperse.
The invention provides a preparation method of graphene and graphene derivative powder, which comprises the following steps:
s1) adding a graphene aqueous solution or a graphene derivative aqueous solution into liquid nitrogen to obtain solidified graphene or solidified graphene derivative;
s2) carrying out vacuum freeze drying on the solidified graphene or the solidified graphene derivative to obtain graphene powder or graphene derivative powder.
Preferably, the graphene aqueous solution or the graphene derivative aqueous solution is subjected to ultrasound and then added to liquid nitrogen.
Preferably, the frequency of the ultrasonic wave is 10-100 KHZ; the ultrasonic time is 1-5 h.
Preferably, the mass fraction of graphene in the graphene aqueous solution is 0.1% -0.5%; the mass fraction of the graphene derivative in the graphene derivative aqueous solution is 0.1% -0.3%.
Preferably, the volume ratio of the graphene aqueous solution or the graphene derivative aqueous solution to the liquid nitrogen is 1: (2-10).
Preferably, the step S1) specifically includes:
and adding the graphene aqueous solution or the graphene derivative aqueous solution into liquid nitrogen in a stirring state to obtain the solidified graphene or the solidified graphene derivative.
Preferably, the stirring speed is 600-1000 rpm.
Preferably, the pre-cooling temperature of the vacuum freeze drying is less than-40 ℃.
Preferably, the temperature in the vacuum freeze-drying process is-40-2 ℃.
Preferably, the vacuum degree of the vacuum drying is 0.1 to 0.5Pa.
The invention provides a preparation method of graphene and graphene derivative powder, which comprises the following steps: s1) adding a graphene aqueous solution or a graphene derivative aqueous solution into liquid nitrogen to obtain solidified graphene or solidified graphene derivative; s2) carrying out vacuum freeze drying on the solidified graphene or the solidified graphene derivative to obtain graphene powder or graphene derivative powder. Compared with the prior art, the method has the advantages that the graphene aqueous solution or the graphene derivative is treated by liquid nitrogen and then is dried in vacuum, so that the irreversible superposition and agglomeration of graphene and the graphene derivative lamellar are effectively avoided, and the obtained graphene and graphene derivative powder is easy to disperse.
Drawings
Fig. 1 is a photograph showing the appearance of graphene powder obtained in example 1 of the present invention;
FIG. 2 is a scanning electron micrograph of the graphene powder obtained in example 1 of the present invention;
FIG. 3 is an X-ray diffraction chart of graphene powder obtained in example 1 of the present invention;
fig. 4 is an atomic force micrograph of graphene powder obtained in example 1 of the present invention;
FIG. 5 is a photograph showing the appearance of an aqueous graphene oxide solution obtained in example 3 of the present invention;
FIG. 6 is a photograph showing the appearance of graphene oxide powder obtained in example 3 of the present invention;
FIG. 7 is a scanning electron micrograph of the graphene oxide powder obtained in example 3 of the present invention;
FIG. 8 is a scanning electron micrograph of the graphene oxide powder obtained in example 3 of the present invention;
FIG. 9 is an X-ray diffraction chart of graphene oxide powder obtained in example 3 of the present invention;
FIG. 10 is an atomic force micrograph of graphene oxide powder obtained in example 3 of the present invention;
FIG. 11 is a photograph showing the appearance of graphene oxide powder obtained in comparative example 1 of the present invention;
FIG. 12 is a scanning electron micrograph of the graphene oxide powder obtained in comparative example 1 of the present invention;
FIG. 13 is a photograph showing the dissolution of graphene oxide powder obtained in comparative example 1 of the present invention in water and ethanol;
FIG. 14 is a photograph showing the dissolution of graphene oxide powder obtained in example 3 of the present invention in water and ethanol;
FIG. 15 is a photograph showing the appearance of graphene oxide powder obtained in comparative example 2 of the present invention;
FIG. 16 is a photograph showing the appearance of graphene powder obtained in comparative example 3 of the present invention;
FIG. 17 is a scanning electron micrograph of the graphene powder obtained in comparative example 3 of the present invention;
fig. 18 is a photograph showing the appearance of graphene powder obtained in comparative example 4 of the present invention.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of graphene powder, which comprises the following steps: s1) adding a graphene aqueous solution into liquid nitrogen to obtain solidified graphene; s2) carrying out vacuum drying on the cured graphene to obtain graphene powder.
The sources of all raw materials are not particularly limited, and the raw materials are commercially available or self-made, and in the invention, the graphene aqueous solution is preferably prepared according to the following method: mixing concentrated sulfuric acid, graphite and fuming nitric acid for reaction, cooling, adding potassium permanganate, adding water for quenching reaction after the mixed reaction, and adding hydrogen peroxide to obtain graphene oxide aqueous solution; and carrying out ultrasonic treatment on the graphene oxide aqueous solution, then adjusting the pH value of the graphene oxide aqueous solution to be alkaline, adding a reducing agent and an alcohol polymer, and heating for reaction to obtain the graphene aqueous solution.
Wherein the graphite is preferably natural crystalline flake graphite; the particle size of the natural crystalline flake graphite is preferably 5 to 20. Mu.m, more preferably 5 to 15. Mu.m, still more preferably 8 to 12. Mu.m, most preferably 10. Mu.m; the mass ratio of the graphite to the concentrated sulfuric acid is preferably 1: (60 to 80), more preferably 1: (65-75); in some embodiments provided herein, the mass ratio of graphite to concentrated sulfuric acid is preferably 1:73.44; in other embodiments provided by the present invention, the mass ratio of graphite to concentrated sulfuric acid is preferably 1:68.85; the mass ratio of the graphite to fuming nitric acid is preferably 1: (0.9 to 1.8), more preferably 1: (0.9 to 1.6), and more preferably 1: (0.9 to 1.4), most preferably 1: (0.9 to 1.3); in some embodiments provided herein, the mass ratio of graphite to fuming nitric acid is preferably 1:0.9475; the mass ratio of fuming nitric acid to concentrated sulfuric acid is preferably 1: (70 to 120), more preferably 1: (70 to 110), and more preferably 1: (70 to 90), and more preferably 1: (70-80); in some embodiments provided herein, the mass ratio of fuming nitric acid to concentrated sulfuric acid is preferably 1:77.5; in other embodiments provided by the present invention, the mass ratio of fuming nitric acid to concentrated sulfuric acid is preferably 1:72.6.
in the invention, preferably, concentrated sulfuric acid and graphite are mixed and stirred first, and fuming nitric acid is added; the mixing and stirring time is preferably 0.5 to 1.5 hours, more preferably 0.8 to 1.4 hours, still more preferably 0.9 to 1.3 hours, and most preferably 1 to 1.2 hours; in some embodiments provided herein, fuming nitric acid is preferably added after mixing and stirring for 1 hour. Fuming nitric acid is used as an acid mixing agent and an intercalation agent to improve the reaction effect.
Adding fuming nitric acid for mixing reaction; the mixing reaction time is preferably 10 to 20 hours, more preferably 12 to 17 hours, still more preferably 12 to 16 hours, and most preferably 13 to 15 hours; in some embodiments provided herein, mixing reaction for 14h is preferred.
After the mixing reaction, the temperature is reduced, preferably to a temperature below 10 ℃, and then potassium permanganate is added. The mass ratio of the graphite to the potassium permanganate is preferably 1: (2.8 to 4), more preferably 1: (3-4), and more preferably 1: (3.5-4); in some embodiments provided herein, the mass ratio of graphite to potassium permanganate is preferably 1:4.
after the addition of potassium permanganate, the reaction is preferably carried out at room temperature, more preferably at 30 ℃; the mixing reaction time is preferably 120 to 160 hours, more preferably 130 to 150 hours, still more preferably 140 to 150 hours, and most preferably 142 to 146 hours; in some embodiments provided herein, the time of the mixing reaction is preferably 144 hours.
After the mixing reaction, adding water to quench the reaction, more preferably, the temperature of the reaction solution is less than 60 ℃, then adding water to quench the reaction, and further preferably, controlling the temperature of the reaction solution to be less than 60 ℃ through a constant pressure dropping funnel, and then adding water to quench the reaction. The mass ratio of the graphite to the water is preferably 1: (30 to 60), more preferably 1: (33 to 60), and more preferably 1: (37-60); in some embodiments provided herein, the graphite to water mass ratio is preferably 1:60; in other embodiments provided by the present invention, the graphite to water mass ratio is preferably 1:37.5.
after the water quenching reaction, preferably heating and then cooling, and then adding hydrogen peroxide; the temperature of the heating is preferably 80-95 ℃, more preferably 85-95 ℃, still more preferably 87-92 ℃ and most preferably 90 ℃; preferably, the temperature is maintained for 2 to 5 hours, more preferably 2 to 4 hours, still more preferably 2.5 to 3 hours, and most preferably 2.5 hours after the temperature is raised; the temperature of the cooling is preferably 50 to 70 ℃ or lower, more preferably 55 to 65 ℃ or lower, and still more preferably 60 ℃ or lower; the mass ratio of the added hydrogen peroxide to the graphite is preferably (3-6): 1, more preferably (4 to 5): 1, a step of; the concentration of the hydrogen peroxide is preferably 25% -35%, more preferably 30% -35%, still more preferably 32% -35%, and most preferably 32%. The hydrogen peroxide is added to reduce the excessive oxidant.
After hydrogen peroxide is added, the temperature is preferably reduced to room temperature, and finally the reaction solution is filtered and cleaned, and after the sulfate radical content is detected to be qualified, ultrasonic is more preferably carried out, so that the graphene oxide aqueous solution is obtained. The filtering and cleaning is preferably performed by a ceramic membrane filtering device; the method of ultrasonic treatment is well known to those skilled in the art, and is not particularly limited, and the ultrasonic treatment is preferably performed by using energy-accumulating ultrasonic equipment; the frequency of the ultrasound is preferably 10 to 100KHz, more preferably 10 to 80KHz, still more preferably 10 to 60KHz, still more preferably 10 to 40KHz, still more preferably 20 to 30KHz, and most preferably 20KHz.
Carrying out ultrasonic treatment on the graphene oxide aqueous solution; the mass concentration of graphene oxide in the graphene oxide aqueous solution is preferably 0.2% -0.35%, more preferably 0.25% -0.35%, and most preferably 0.3%. Too low mass fraction of graphene oxide in the graphene oxide aqueous solution can cause low efficiency, too high mass fraction of graphene oxide in the graphene oxide aqueous solution can influence subsequent reduction effects, so that reduction is incomplete, and caking phenomenon occurs.
The ultrasonic treatment can further delaminate the graphene oxide, and the dispersion plays a role in crushing. The method of ultrasonic treatment is well known to those skilled in the art, and is not particularly limited, and the ultrasonic treatment is preferably performed by using energy-accumulating ultrasonic equipment; the frequency of the ultrasound is preferably 10 to 100KHz, more preferably 10 to 80KHz, still more preferably 10 to 60KHz, still more preferably 10 to 40KHz, still more preferably 20 to 30KHz, and most preferably 20KHz; the ultrasonic time is preferably 1 to 5 hours, more preferably 2 to 4 hours, and still more preferably 2 to 3 hours; in some embodiments provided by the present invention, the time of the ultrasound is preferably 2 hours.
After the ultrasonic treatment, the pH value of the solution is adjusted to be alkaline, preferably the pH value of the solution is adjusted to be 10.3-10.8, more preferably the pH value of the solution is adjusted to be 10.5-10.8, and still more preferably the pH value of the solution is adjusted to be 10.5-10.6; in some embodiments provided herein, it is preferred to adjust the pH of the solution to 10.5; in other embodiments provided by the present invention, the pH of the solution is preferably adjusted to 10.6.
Then adding a reducing agent and an alcohol polymer; wherein the reducing agent is a reducing agent well known to those skilled in the art, and is not particularly limited, and hydrazine hydrate or sodium borohydride is preferably added, and hydrazine hydrate is more preferably added as the reducing agent in the present invention; the mass ratio of the graphene oxide to the reducing agent is preferably 1: (0.5 to 1.2), more preferably 1: (0.5 to 1), and more preferably 1: (0.6 to 0.8), most preferably 1: (0.6 to 0.7); in some embodiments provided by the present invention, the mass ratio of graphene oxide to reducing agent is preferably 1:0.6; the alcohol polymer is used as a polymerization inhibitor to be added into the solution to prevent the generated graphene from aggregation; the alcohol polymer is preferably polyethylene glycol; the mass ratio of the alcohol polymer to the reducing agent is preferably 1: (1 to 10), more preferably 1: (1 to 8), and more preferably 1: (1 to 6), and more preferably 1: (1.5 to 4), most preferably 1: (1.5-2); in some embodiments provided herein, the mass ratio of the alcohol polymer to the reducing agent is preferably 1:1.8.
adding a reducing agent and an alcohol polymer, and then heating for reaction; the temperature of the heating reaction is preferably 70-95 ℃, more preferably 75-95 ℃, still more preferably 80-95 ℃, and most preferably 85-95 ℃; in some embodiments provided herein, the temperature of the heating reaction is preferably 90 ℃; the heating reaction time is preferably 10 to 20 hours, more preferably 12 to 18 hours, still more preferably 12 to 16 hours, and most preferably 13 to 15 hours; in some embodiments provided herein, the heating reaction time is preferably 14 hours.
After the heating reaction, the temperature is preferably naturally reduced, and then water washing is carried out, more preferably, the pH value is 8, so that the graphene aqueous solution is obtained.
According to the invention, the graphene oxide aqueous solution is subjected to ultrasonic treatment, so that the graphene oxide is further layered and dispersed, and the alcohol polymer is added as a polymerization inhibitor, so that the obtained graphene has high single-layer rate and uniform sheet diameter, and the preparation method is simple and has low cost.
Adding the graphene aqueous solution into liquid nitrogen; wherein the mass concentration of graphene in the graphene aqueous solution is preferably 0.1% -0.5%, more preferably 0.1% -0.4%, still more preferably 0.1% -0.3%, and most preferably 0.1% -0.2%; in some embodiments provided herein, the mass concentration of graphene in the aqueous graphene solution is preferably 0.1%.
In the present invention, in order to disperse the graphene in an aqueous solution better, it is preferable to perform ultrasonic treatment first and then add it to liquid nitrogen. The method of ultrasonic treatment is well known to those skilled in the art, and is not particularly limited, and the ultrasonic treatment is preferably performed by using energy-accumulating ultrasonic equipment; the frequency of the ultrasound is preferably 10 to 100KHz, more preferably 10 to 80KHz, still more preferably 10 to 60KHz, still more preferably 10 to 40KHz, still more preferably 20 to 30KHz, and most preferably 20KHz; the time of the ultrasonic wave is preferably 1 to 5 hours, more preferably 2 to 4 hours, still more preferably 2 to 3 hours, and most preferably 2 hours. The volume ratio of the graphene aqueous solution to the liquid nitrogen is preferably 1: (2 to 10), more preferably 1: (3 to 8), and more preferably 1: (3-6), most preferably 1: (3-5); in some embodiments provided by the present invention, the volume ratio of the graphene aqueous solution to liquid nitrogen is preferably 1:5, a step of; in other embodiments provided by the present invention, the volume ratio of the graphene aqueous solution to liquid nitrogen is preferably 3:10.
in order to better mix graphene with liquid nitrogen, preferably adding the graphene aqueous solution to the liquid nitrogen in a stirring state to obtain solidified graphene; the stirring speed is preferably 600 to 1000rpm, more preferably 700 to 900rpm, still more preferably 750 to 850rpm, and most preferably 800rpm.
Vacuum drying the cured graphene; the vacuum degree of the vacuum drying is preferably 0.1 to 0.5Pa, more preferably 0.1 to 0.3Pa, still more preferably 0.1 to 0.2Pa, and most preferably 0.1Pa; more preferably, the solidified graphene is subjected to vacuum freeze drying; the pre-cooling temperature of the vacuum freeze drying is preferably less than-40 ℃, more preferably between-45 ℃ and-55 ℃, and still more preferably between-50 ℃; then the temperature of a vacuum freeze-dried separator is controlled in sections, and the temperature of the separator is required to be not higher than-2 ℃ to-5 ℃; when the material temperature is higher than 2 ℃, the graphene is completely dried, and inert gas is introduced to replace the vacuum degree, so that graphene powder is obtained; the inert gas may be any inert gas known to those skilled in the art, and is not particularly limited, but argon is preferred in the present invention.
According to the invention, the graphene aqueous solution is treated by liquid nitrogen and then vacuum-dried, so that the irreversible superposition and agglomeration of graphene sheets are effectively solved, and the obtained graphene powder is easy to disperse.
The invention also provides a preparation method of the graphene derivative powder, which comprises the following steps: s1) adding a graphene derivative aqueous solution into liquid nitrogen to obtain a solidified graphene derivative; s2) carrying out vacuum drying on the cured graphene derivative to obtain graphene derivative powder.
The graphene derivative may be a graphene derivative known to those skilled in the art, and is not particularly limited, and graphene oxide is preferred in the present invention; the graphene oxide may be self-made or commercially available, and is not particularly limited, but is preferably prepared according to the preparation method of graphene oxide described above in the present invention.
The graphene aqueous solution is added to liquid nitrogen, wherein the mass fraction of the graphene derivative in the graphene derivative aqueous solution is preferably 0.1% to 0.3%, more preferably 0.1% to 0.2%, still more preferably 0.1%.
In the present invention, in order to disperse the graphene derivative in an aqueous solution better, it is preferable to perform ultrasonic treatment first and then add it to liquid nitrogen. The method of ultrasonic treatment is well known to those skilled in the art, and is not particularly limited, and the ultrasonic treatment is preferably performed by using energy-accumulating ultrasonic equipment; the frequency of the ultrasound is preferably 10 to 100KHz, more preferably 10 to 80KHz, still more preferably 10 to 60KHz, still more preferably 10 to 40KHz, still more preferably 20 to 30KHz, and most preferably 20KHz; the time of the ultrasonic wave is preferably 1 to 5 hours, more preferably 2 to 4 hours, still more preferably 2 to 3 hours, and most preferably 2 hours. The volume ratio of the graphene derivative aqueous solution to liquid nitrogen is preferably 1: (2 to 10), more preferably 1: (3 to 8), and more preferably 1: (3-6), most preferably 1: (3-5); in some embodiments provided by the present invention, the volume ratio of the graphene derivative aqueous solution to liquid nitrogen is preferably 1:5.
in order to better mix the graphene derivative with liquid nitrogen, it is preferable to add an aqueous solution of the graphene derivative to the liquid nitrogen in a stirred state to obtain a solidified graphene derivative; the stirring speed is preferably 600 to 1000rpm, more preferably 700 to 900rpm, still more preferably 750 to 850rpm, and most preferably 800rpm.
Vacuum drying the cured graphene derivative; the vacuum degree of the vacuum drying is preferably 0.1 to 0.5Pa, more preferably 0.1 to 0.3Pa, still more preferably 0.1 to 0.2Pa, and most preferably 0.1Pa; more preferably, the cured graphene derivative is subjected to vacuum freeze drying; the pre-cooling temperature of the vacuum freeze drying is preferably less than-40 ℃, more preferably between-45 ℃ and-55 ℃, and still more preferably between-50 ℃; then the temperature of a vacuum freeze-dried separator is controlled in sections, and the temperature of the separator is required to be not higher than-2 ℃ to-5 ℃; the temperature in the vacuum freeze drying process is preferably-40-2 ℃, more preferably-40-5 ℃; when the material temperature is higher than 2 ℃, the graphene derivative is completely dried, and inert gas is introduced to replace the vacuum degree, so that graphene derivative powder is obtained; the inert gas may be any inert gas known to those skilled in the art, and is not particularly limited, but argon is preferred in the present invention.
The graphene derivative aqueous solution is quickly frozen by liquid nitrogen, so that the graphene derivative is in solid state in a short time, and then solvent water is continuously sublimated by freezing under a vacuum condition to obtain a powder product. The method has the advantage of dispersing macroscopic solution into fine particles, thereby greatly reducing the possibility of agglomeration. And the whole drying process is kept at the temperature of minus 2 ℃ to ensure that the active targets of the graphene derivative, especially the graphene oxide, are not damaged by heat.
In order to further illustrate the present invention, the following describes in detail a preparation method of graphene and a powder of a derivative thereof according to the present invention with reference to examples.
The reagents used in the examples below are all commercially available.
Example 1
1.1 dispersing 20g (1.667 mol) of natural crystalline flake graphite with the granularity of 10 mu m in 800ml of 98% concentrated sulfuric acid at room temperature, stirring for 1 hour, adding 10ml of fuming nitric acid, reacting for 14 hours, controlling the reaction temperature below 10 ℃, adding 80g of potassium permanganate, and reacting for 144 hours at the constant temperature of 30 ℃. And (3) dropwise adding 1.2L of high-purity water at a temperature lower than 60 ℃ by using a constant-pressure dropping funnel, heating to 90 ℃ for reaction for 2.5h, cooling to a temperature lower than 60 ℃, adding 40ml of hydrogen peroxide, naturally cooling, cleaning by using ceramic membrane cleaning equipment, and performing ultrasonic treatment to obtain a single-layer graphene oxide solution.
1.2 ultrasonic treatment of 2L graphene oxide aqueous solution with concentration of 0.3% at 20KHz and 2KW power for 2h, regulating pH to 10.5 with ammonia water, adding 3.6g hydrazine hydrate and 2g polyethylene glycol, stirring, controlling reaction temperature to 90 deg.C, and reacting for 14 hr. And naturally cooling, and washing until the pH value is 8 to obtain the graphene aqueous solution. Adding pure water to prepare 0.1% graphene solution for later use.
1.3, starting a vacuum freeze dryer, setting the precooling temperature to-50 ℃, and precooling for four hours. Taking 5L of liquid nitrogen, adding mechanical stirring, and slowly adding 1L of 0.1% graphene solution into the liquid nitrogen at the rotating speed of 800rpm to obtain solidified graphene; and (3) placing the solidified graphene into a vacuum freeze dryer, starting a vacuum pump, and keeping the vacuum degree at 0.1Pa. When the material temperature is higher than 2 ℃, closing the vacuum stop valve, opening the inflation valve, slowly enabling the internal pressure to reach the atmospheric pressure, and taking out the graphene powder.
Fig. 1 is a photograph showing the appearance of graphene powder obtained in example 1. As can be seen from fig. 1, the product density is much less than that of graphite.
The graphene powder obtained in example 1 was analyzed by a scanning electron microscope to obtain a scanning electron micrograph thereof, as shown in fig. 2. As can be seen from fig. 2, it is a single layer structure, and no agglomeration occurs.
The graphene powder obtained in example 1 was analyzed by X-ray diffraction to obtain an X-ray diffraction pattern thereof, as shown in fig. 3.
The graphene powder obtained in example 1 was analyzed by an atomic force microscope to obtain an atomic force micrograph thereof, as shown in fig. 4. As can be seen from fig. 4, the thickness of the graphene obtained in example 1 was 2 to 4nm.
Example 2
2.1 dispersing 60g (5 mol) of natural crystalline flake graphite with the granularity of 10 mu m in 2.25L98% concentrated sulfuric acid at room temperature, stirring for 1 hour, adding 30ml of fuming nitric acid, reacting for 14 hours, controlling the reaction temperature below 10 ℃, adding 240g of potassium permanganate, and reacting for 144 hours at the constant temperature of 30 ℃. 2.25L of high-purity water was added dropwise at a temperature lower than 60℃using a constant pressure dropping funnel. Heating to 90 ℃ for reaction for 2.5h, cooling to below 60 ℃, and adding 125ml hydrogen peroxide. And (3) cleaning by using ceramic membrane cleaning equipment after natural cooling, and obtaining a single-layer graphene oxide solution after ultrasonic treatment.
2.2 ultrasonic treatment of 4L graphene oxide aqueous solution with concentration of 0.3% under 20KHz and 2KW power for 2h, adjusting pH to 10.5 with ammonia water, adding 7.2g hydrazine hydrate, controlling reaction temperature at 90 deg.C, and reacting for 14 hours. And naturally cooling, and washing until the pH value is 8 to obtain the graphene aqueous solution. Adding pure water to prepare 0.1% graphene solution for later use.
2.3, starting the vacuum freeze dryer, setting the precooling temperature to-50 ℃, and precooling for four hours. Taking 10L of liquid nitrogen, adding mechanical stirring, and slowly adding 3L of 0.1% graphene solution into the liquid nitrogen at the rotating speed of 800rpm to obtain solidified graphene; and (3) placing the solidified graphene into a vacuum freeze dryer, starting a vacuum pump, and keeping the vacuum degree at 0.1Pa. When the material temperature is higher than 2 ℃, closing the vacuum stop valve, opening the inflation valve, slowly enabling the internal pressure to reach the atmospheric pressure, and taking out the graphene powder.
Example 3
3.1 preparation of graphene oxide solution. 60g (5 mol) of natural crystalline flake graphite with the granularity of 10 mu m is dispersed in 2.25L of 98% concentrated sulfuric acid at room temperature, 30ml of fuming nitric acid is added after stirring for 1 hour, 180g of potassium permanganate is added after the reaction is carried out for 14 hours at the reaction temperature of less than 10 ℃, and the reaction is carried out for 72 hours at the constant temperature of 30 ℃. 2.25L of high-purity water was added dropwise at a temperature lower than 60℃using a constant pressure dropping funnel. Heating to 90 ℃ for reaction for 2.5h, cooling to below 60 ℃, and adding 125ml of 32% hydrogen peroxide. And (3) cleaning by using ceramic membrane cleaning equipment after naturally cooling until the sulfate radical content in the permeate is less than 20ppm. Detecting the solid content of the graphene oxide aqueous solution, and preparing the graphene oxide aqueous solution with the solid content of 0.1 percent.
3.2 starting a vacuum freeze dryer, wherein the precooling temperature is-50 ℃. Setting the freezing process temperature at-40 ℃ to-5 ℃; 5L of liquid nitrogen is taken, mechanical stirring is added, and 1L0.1% graphene oxide solution is slowly added into the liquid nitrogen under the condition of 800rpm. Along with continuous gasification of liquid nitrogen, a proper amount of liquid nitrogen needs to be added into the stirring container in time, so that the liquid is ensured not to splash in a bumping way. And (5) putting the graphene oxide solution into a vacuum dryer after all the graphene oxide solution is changed into solid particles. Starting a vacuum pump, maintaining vacuum, and performing vacuum drying at a drying temperature of 40 ℃ to minus 5 ℃.
When the material temperature probe shows that the temperature is higher than 2 ℃, argon is used for replacing vacuum, a dry environment is kept, and graphene oxide powder is taken out.
FIG. 5 is a photograph showing the appearance of the aqueous graphene oxide solution obtained in example 3; fig. 6 is a photograph showing the appearance of the graphene oxide powder obtained in example 3.
The graphene oxide powder obtained in example 3 was analyzed by a scanning electron microscope to obtain a scanning electron micrograph thereof, as shown in fig. 7 and 8.
The graphene oxide powder obtained in example 3 was analyzed by X-ray diffraction to obtain an X-ray diffraction pattern thereof, as shown in fig. 9.
The graphene oxide powder obtained in example 3 was analyzed by an atomic force microscope to obtain an atomic force micrograph thereof, as shown in fig. 10.
Comparative example 1
And directly placing the graphene oxide aqueous solution in the embodiment 3 into a vacuum freeze dryer for freeze drying to obtain graphene oxide powder.
Fig. 11 is a photograph showing the appearance of the graphene oxide powder obtained in comparative example 1.
The graphene oxide powder obtained in comparative example 1 was analyzed by a scanning electron microscope to obtain a scanning electron micrograph thereof, as shown in fig. 12. As can be seen from FIG. 12, the agglomeration is more serious.
The graphene oxide powder obtained in comparative example 1 was dissolved in water and ethanol, as shown in fig. 13, wherein a is an ethanol solution and B is an aqueous solution, and it is apparent from fig. 13 that dissolution was incomplete and suspended matter was present.
The graphene oxide powder obtained in example 3 was dissolved in water and ethanol, as shown in fig. 14, where a is an ethanol solution and B is an aqueous solution. It can be seen from fig. 14 that it is completely dissolved.
Comparative example 2
And (3) placing the graphene oxide aqueous solution in the embodiment 3 into an oven for drying to obtain graphene oxide powder.
Fig. 15 is a photograph showing the appearance of the graphene oxide powder obtained in comparative example 2. As can be seen from fig. 15, the particles are distributed in a flake form on glass, and the morphology is greatly different from that of the powder.
Comparative example 3
And directly placing the graphene aqueous solution obtained in the embodiment 1 into a freeze dryer for drying, wherein the freeze drying conditions are the same as those of the embodiment 1, so as to obtain graphene powder.
Fig. 16 is a photograph showing the appearance of the graphene powder obtained in comparative example 3. As can be seen from fig. 16, the appearance of the graphene powder obtained in example 1 was relatively similar.
The graphene powder obtained in comparative example 3 was analyzed by a scanning electron microscope to obtain a scanning electron micrograph thereof, as shown in fig. 17. As can be seen from fig. 17, the agglomeration thereof is serious.
Comparative example 4
And directly placing the graphene aqueous solution obtained in the embodiment 1 in an oven for drying to obtain graphene powder.
Fig. 18 is a photograph showing the appearance of the graphene powder obtained in comparative example 4. It can be seen from fig. 18 that it is agglomerated into a block shape.
Claims (1)
1. The preparation method of the graphene and the graphene derivative powder is characterized by comprising the following steps of:
s1) adding a graphene aqueous solution or a graphene derivative aqueous solution into liquid nitrogen to obtain solidified graphene or solidified graphene derivative;
s2) carrying out vacuum freeze drying on the solidified graphene or the solidified graphene derivative to obtain graphene powder or graphene derivative powder;
the graphene aqueous solution is prepared according to the following method: mixing concentrated sulfuric acid, graphite and fuming nitric acid for reaction, cooling, adding potassium permanganate, adding water for quenching reaction after the mixed reaction, and adding hydrogen peroxide to obtain graphene oxide aqueous solution; carrying out ultrasonic treatment on the graphene oxide aqueous solution, then adjusting the pH value of the graphene oxide aqueous solution to be alkaline, adding a reducing agent and an alcohol polymer, and heating to react to obtain the graphene oxide aqueous solution;
the graphite is natural crystalline flake graphite; the grain diameter of the natural crystalline flake graphite is 5-20 mu m; the mass ratio of the graphite to the concentrated sulfuric acid is 1: (60-80); the mass ratio of the graphite to fuming nitric acid is 1: (0.9 to 1.8); the mass ratio of fuming nitric acid to concentrated sulfuric acid is 1: (70-120);
cooling to the temperature below 10 ℃ of the reaction solution, and then adding potassium permanganate; the mass ratio of the graphite to the potassium permanganate is 1: (2.8-4);
adding potassium permanganate, mixing and reacting for 120-160 h at room temperature to make the temperature of the reaction solution less than 60 ℃, and then adding water to quench the reaction; the mass ratio of the graphite to the water is 1: (30-60);
after the water quenching reaction is carried out, heating and cooling are carried out, and then hydrogen peroxide is added; the temperature of the heating is 80-95 ℃; maintaining for 2-5 h after heating; the temperature of the cooling is below 50-70 ℃; the mass ratio of the added hydrogen peroxide to the graphite is (3-6): 1, a step of; the concentration of the hydrogen peroxide is 25% -35%;
after hydrogen peroxide is added, cooling to room temperature, finally filtering and cleaning the reaction solution, and carrying out ultrasonic treatment after the sulfate radical content is detected to be qualified to obtain graphene oxide aqueous solution;
the reducing agent is hydrazine hydrate or sodium borohydride; the mass ratio of the graphene oxide to the reducing agent is 1: (0.5-1.2); the alcohol polymer is polyethylene glycol; the mass ratio of the alcohol polymer to the reducing agent is 1: (1-10);
adding a reducing agent and an alcohol polymer, and then heating for reaction; the temperature of the heating reaction is 70-95 ℃; the heating reaction time is 10-20 h;
naturally cooling after the heating reaction, and then washing with water until the pH value is 8 to obtain a graphene aqueous solution;
the graphene derivative is graphene oxide;
the graphene aqueous solution or the graphene derivative aqueous solution is subjected to ultrasonic treatment firstly and then added into liquid nitrogen;
the ultrasonic frequency is 10-100 KHZ; the ultrasonic time is 1-5 h;
the mass fraction of graphene in the graphene aqueous solution is 0.1% -0.5%; the mass fraction of the graphene derivative in the graphene derivative aqueous solution is 0.1% -0.3%;
the volume ratio of the graphene aqueous solution or the graphene derivative aqueous solution to the liquid nitrogen is 1: (2-10);
the step S1) specifically comprises the following steps:
adding the graphene aqueous solution or the graphene derivative aqueous solution into liquid nitrogen in a stirring state to obtain solidified graphene or solidified graphene derivative;
the stirring speed is 600-1000 rpm;
the pre-cooling temperature of the vacuum freeze drying is less than-40 ℃;
the vacuum degree of the vacuum freeze drying is 0.1Pa to 0.5Pa;
the temperature in the vacuum freeze drying process is-40-2 ℃.
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