CN109292760B - Method for preparing graphene - Google Patents
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- CN109292760B CN109292760B CN201811456420.5A CN201811456420A CN109292760B CN 109292760 B CN109292760 B CN 109292760B CN 201811456420 A CN201811456420 A CN 201811456420A CN 109292760 B CN109292760 B CN 109292760B
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Abstract
The invention discloses a method for preparing graphene, which can prepare the graphene by using renewable biomass materials as raw materials through freeze drying and high-temperature carbonization treatment, and develops a new freeze drying method. The graphene prepared by the method is flaky, the morphology structure of the graphene can be regulated and controlled by regulating the concentration of a biomass solution, and the chemical components of the graphene can be regulated by high-temperature carbonization temperature. All raw materials and reagents are wide in source, easy to obtain, low in cost, degradable and harmless to human bodies and the environment; the preparation process does not need a catalyst, the process is simple and convenient, large-scale industrial production is easy to realize, new theoretical guidance and technical support are provided for simply and conveniently preparing the graphene, high added value application of the biomass material is improved, and good economic benefits are achieved.
Description
Technical Field
The invention relates to the technical field of carbon material preparation, in particular to a method for preparing graphene.
Background
Graphene is a two-dimensional monoatomic layer carbon material stacked by hexagonal peak nest lattices, and the almost completely transparent, light and flexible material is not only the thinnest and hardest nano material known at present, but also has a plurality of excellent properties, such as the thermal conductivity coefficient of the graphene is about 5300W/m.K, which is higher than that of materials such as natural graphite, carbon nano tubes and diamond; the electron mobility of the graphene at normal temperature is larger than 15000cm2V.s, higher than carbon nanotubes and silicon crystals; the conductivity of the graphene is as high as 10 < -6 > S/m, is lower than that of copper or silver, and is the highest material at present. Based on the unique physical and chemical properties of graphene, the graphene has a wide application prospect in the fields of lithium ion batteries, super capacitors, solar cells, light emitting diodes, sensors, hydrogen storage, catalyst carriers, composite materials, coatings, biological scaffold materials, drug controlled release and the like, and is more and more emphasized by people.
At present, various methods can be used for preparing graphene, such as a micro mechanical lift-off method, a solvent lift-off method, an oxidation-reduction method, a crystal epitaxial growth method, a chemical vapor deposition method, a microwave method, an electrochemical method, and the like. Among the methods, the preparation efficiency of the micro-mechanical stripping method and the crystal epitaxial growth method is low, and the requirement of large-scale production is difficult to meet at present; although the chemical vapor deposition method can obtain a large-size continuous graphene film, the chemical vapor deposition method is suitable for electronic devices and transparent conductive films, and cannot meet the large-scale requirements in the fields of energy storage materials and functional composite materials; the graphene powder prepared by the oxidation-reduction method is low in cost and easy to realize, but the prepared graphene generally has more defects, and a large amount of waste water or waste gas is generated in the preparation process, so that the environment is seriously polluted; the microwave method and the electrochemical method have the advantages of short reaction period, high efficiency, greenness, no pollution, complete appearance of the prepared graphene, few defects and the like, but the prepared graphene has low yield and cannot realize large-scale industrial production.
Biomass carbon source materials such as lignin, alkali lignin, cellulose, sodium alginate, tannic acid and the like are important resources which are rich in reserves and can be regenerated, renewable biomass materials are the most abundant resources of carbon storage in the world, and the biomass carbon source materials can be used as an excellent porous carbon material precursor due to the characteristics of wide and easily available sources, low cost, rich carbon content and the like; at present, the renewable biomass material is used as a precursor to prepare a carbon material, so that the production of the degradable and cheap biomass carbon aerogel which is harmless to human bodies and environment is a direction of much attention. However, few documents report the application of biomass materials to the preparation of biomass-based graphene.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a novel method for efficiently preparing graphene, solves the problems that the existing graphene is high in preparation cost, complex in process and harsh and difficult to control, has large environmental pollution and high energy consumption, cannot realize large-scale industrial production, is difficult to store, and the like, expands a freeze drying method, realizes freeze drying under normal pressure, and promotes high value-added application of renewable biomass materials.
In order to solve the technical problems, the invention adopts the following technical scheme: a method of preparing graphene, comprising the steps of:
1) dissolving a biomass carbon source material in a solvent, fully mixing to obtain a mixed solution with the concentration of 5-50 mg/mL, and freeze-drying the mixed solution to obtain the nano-thickness sheet-structure porous aerogel;
2) and (2) carrying out high-temperature carbonization treatment on the sheet-structure porous aerogel obtained in the step 1) in vacuum or inert atmosphere to obtain graphene.
Thus, the single-layer or multi-layer sheet distribution of biomass molecules such as lignin and the like can be realized by directly using a freeze drying technology, the structure and the distribution of the precursor can be regulated and controlled by controlling the concentration, the prepared graphene precursor has a nano-functional biomass aerogel, the specific surface area and the pore structure can be greatly increased, and the physical morphology structure of the graphene precursor is extremely similar to that of graphene or graphene oxide; further, carbonization and graphitization of the organic carbon source material are realized in a high-temperature heat treatment mode, the conversion of a chemical structure is completed, the organic carbon is converted into a carbon component of graphite, the preparation of graphene is finally realized, and the graphitization degree can be controlled by adjusting the carbonization temperature.
Preferably, the biomass carbon source material is one or more of lignin, alkali lignin, hydroxyethyl cellulose, tannic acid and sodium alginate.
Preferably, the solvent is deionized water, an organic solvent, an alkaline aqueous solution or a mixed solution of an organic solvent and deionized water.
Thus, different carbon source materials with different properties can be dissolved by using different solvents; and the alkali can also improve the graphitization efficiency of the carbon material to a certain extent.
Preferably, the concentration of the alkaline solution is 1-20%, and the alkali in the alkaline solution is sodium hydroxide or potassium hydroxide; the organic solvent is tert-butanol.
Preferably, the freeze-drying comprises the steps of: freezing the mixed solution at-196 to-0 ℃ for fructification, and then transferring the frozen fructification into a freezing freeze dryer for complete drying; the treatment time is 24-72 h; the method further comprises the steps of freezing the mixed solution in a cold environment at-196 to-0 ℃ for compaction, placing the mixed solution on a water-absorbing material at-10 to 10 ℃, and drying for 48 to 120 hours.
Therefore, the porous morphology of the material can be kept by freeze drying under the normal pressure condition, and the method does not need to be realized under the vacuum condition, and is simple and convenient to operate.
Preferably, the thickness of the aerogel is 10-500 nm.
Preferably, the inert atmosphere is argon or nitrogen, helium or neon.
Preferably, the carbonization treatment temperature is extremely high and is 1000-2500 ℃, and the time is 0.5-6 h.
Under high temperature conditions, graphitization of the carbon material is achieved, and the degree of graphitization is directly related to temperature. Within a certain temperature range, the graphitization degree of the material can be improved by properly increasing the heat treatment temperature.
Graphene obtained according to the preparation method.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the graphene prepared by the invention, a mode of firstly carrying out structural layering on the precursor is adopted, the process is extremely simple, the preparation efficiency of a single-layer or multi-layer precursor material is greatly improved, and the morphological structure and distribution characteristics of the graphene can be regulated and controlled by adjusting the concentration of a biomass solution.
2. The method for preparing the graphene adopts a mode of firstly layering or separating and then graphitizing, solves the problem that the step of directly or indirectly stripping graphite is extremely complex and difficult in the preparation process of the traditional method, obviously simplifies the preparation process, obviously improves the preparation efficiency, and the prepared target graphene is easy to disperse and store for a long time.
3. According to the invention, the renewable biomass material is used as a raw material, the graphene can be prepared by freeze drying and high-temperature carbonization treatment, the preparation process does not need a catalyst, the process is simple and convenient, the raw material and the solvent are widely and easily available, low in cost and degradable, and harmless to human bodies and environment, large-scale industrial production is easily realized, new theoretical guidance and technical support are provided for simply and conveniently preparing the graphene, meanwhile, the high-added-value application of the biomass material is improved, and the method has good economic benefits.
4. The method of the invention also expands the freeze drying method, directly uses the water absorbing material for drying, can keep the porous appearance of the material, does not need to be realized under the vacuum condition, has simple and convenient operation, simple and easily obtained material, low energy consumption and low cost, and can be used in large area.
Drawings
Fig. 1 is a scanning electron micrograph of graphene prepared in example 1;
fig. 2 is a scanning electron micrograph of the graphene prepared in example 3.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1
1) Dissolving water-soluble alkali lignin in deionized water to prepare a lignin aqueous solution with the concentration of 50mg/mL, quickly freezing the lignin aqueous solution in liquid nitrogen, and drying in a freeze dryer for 24 hours to obtain a flaky lignin aerogel with the thickness of about 300 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 0.5 hour under the conditions of argon atmosphere and 2500 ℃, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component is 90% by Raman spectrum analysis, and the yield is 8.8%.
Example 2
1) Dissolving water-soluble alkali lignin in ionized water to prepare a lignin aqueous solution with the concentration of 20 mg/mL, quickly freezing the lignin aqueous solution in liquid nitrogen, and then drying in a freeze dryer for 48 hours to obtain lignin aerogel with the thickness of about 100 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 1 hour under the conditions of argon atmosphere and 2000 ℃, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component is 95% by Raman spectrum analysis, and the yield is 13%.
Example 3
1) Dissolving water-soluble alkali lignin in deionized water to prepare a lignin aqueous solution with the concentration of 10mg/mL, quickly freezing the lignin aqueous solution at the temperature of between 20 ℃ below zero in a refrigerator, and then treating the lignin aqueous solution in a freeze dryer for 72 hours to obtain lignin aerogel with the thickness of about 60 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 2 hours at 1500 ℃ in a nitrogen atmosphere, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component is 88% by Raman spectrum analysis, and the yield is 19%.
Example 4
1) Dissolving alkali lignin in tert-butyl alcohol to prepare a lignin solution with the concentration of 5mg/mL, freezing the lignin solution in a refrigerator at the temperature of 20 ℃ below zero, and then placing the mixed solution on sanitary absorbent paper at the temperature of 0 ℃ for drying treatment for 120h to obtain lignin aerogel with the thickness of about 20 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 6 hours at 1000 ℃ in a nitrogen atmosphere, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component is 71% by Raman spectrum analysis, and the yield is 18%.
Example 5
1) Alkali lignin was dissolved in deionized water and tert-butanol (volume ratio 1: 1) preparing a lignin solution with the concentration of 10mg/mL in the mixed solvent, quickly freezing the lignin solution in liquid nitrogen, and then placing the mixed solution on sanitary absorbent paper at the temperature of 10 ℃ for drying treatment for 96 hours to obtain lignin aerogel with the thickness of about 50 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tube furnace, carbonizing for 2 hours under the conditions of vacuum and 1500 ℃, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component is 90% by Raman spectrum analysis, and the yield is 16%.
Example 6
1) Dissolving lignin in 5% KOH aqueous solution to prepare lignin solution with the concentration of 10mg/mL, freezing the lignin solution in a refrigerator at the temperature of 20 ℃ below zero, and then processing the lignin solution in a freeze dryer for 72 hours to obtain lignin aerogel with the thickness of about 50 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 1 hour at 1500 ℃ in a nitrogen atmosphere, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component of the graphene is 93% by Raman spectrum analysis, and the yield is 17%.
Example 7
1) Dissolving water-soluble cellulose in deionized water to prepare a cellulose solution with the concentration of 10mg/mL, freezing the cellulose solution in a refrigerator at the temperature of 20 ℃ below zero, and then drying the cellulose solution in a freeze dryer for 72 hours to obtain cellulose aerogel with the thickness of about 100 nm;
2) placing the aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 1 hour at 1500 ℃ in a nitrogen atmosphere, cooling, and preparing microcosmic flaky graphene, wherein the chemical component graphene component of the graphene is 79% by Raman spectrum analysis, and the yield is 15%.
Example 8
1) Dissolving tannic acid in deionized water to prepare a tannic acid aqueous solution with the concentration of 50mg/mL, freezing the tannic acid aqueous solution in a refrigerator at the temperature of 20 ℃ below zero, and drying in a freeze dryer for 48 hours to obtain tannic acid aerogel with the thickness of about 250 nm;
2) putting the lignin aerogel obtained in the step 1) as a graphene precursor in a tube furnace, carbonizing for 1 hour under the conditions of argon atmosphere and 1500 ℃, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component of the graphene is 74% by Raman spectroscopy, and the yield is 20%.
Example 9
1) Dissolving sodium alginate in deionized water, preparing a 10mg/mL sodium alginate aqueous solution, and drying the sodium alginate aqueous solution in a freeze dryer at-50 ℃ for 72 hours to obtain a sodium alginate aerogel with the thickness of about 100 nm;
2) placing the aerogel obtained in the step 1) as a graphene precursor in a tubular furnace, carbonizing for 1 hour under the conditions of argon atmosphere and 1500 ℃, cooling, and preparing microscopically flaky graphene, wherein the chemical component graphene component of the graphene is 65% by Raman spectrum analysis, and the yield is 16%.
Example 10
1) Dissolving water-soluble alkali lignin and sodium alginate in deionized water, preparing a lignin and sodium alginate aqueous solution with the concentration of 50mg/mL, quickly freezing the lignin and sodium alginate aqueous solution in liquid nitrogen, placing the solution on flat sanitary absorbent paper at the temperature of 0 ℃, and drying for 72 hours to obtain aerogel with the thickness of about 400 nm;
2) placing the aerogel obtained in the step 1) as a graphene precursor in a tube furnace, carbonizing for 1 hour under the conditions of vacuum and 1500 ℃, cooling to obtain microcosmic flaky graphene, analyzing the chemical component of the graphene by using Raman spectroscopy to obtain 89% of graphene, and obtaining the yield of 26%.
Fig. 1 and 2 are scanning electron micrographs of the graphenes prepared in examples 1 and 3, respectively, and it can be seen from fig. 1 that, at a higher concentration (50 mg/mL), the graphenes having a more continuous lamellar structure can be maintained after carbonization. With the reduction of the concentration of the biomass solution, the thickness of the prepared sheet precursor and graphene becomes thinner and thinner, and pores are easy to appear in the middle of a graphene layer, for example, when the concentration of the solution is 10mg/mL (figure 2), the pore structure is much more than that of 50 mg/mL; particularly, at concentrations of 5mg/mL or even lower, the pores become more pronounced, resulting in graphene sheets much smaller than at higher concentrations.
In conclusion, the morphology structure and distribution characteristics of the graphene can be regulated and controlled by regulating the concentration of the biomass solution; the chemical composition of the graphene can be regulated and controlled by regulating the carbonization temperature.
The above description is only exemplary of the present invention and should not be taken as limiting, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A method for preparing graphene, comprising the following steps:
1) dissolving a biomass carbon source material in a solvent, fully mixing to obtain a mixed solution with the concentration of 5-50 mg/mL, and freeze-drying the mixed solution to obtain the nano-thickness sheet-structure porous aerogel; the freeze-drying comprises the following steps: freezing the mixed solution in a cold state at-196 to-0 ℃ for compaction, and then placing the mixed solution on a water-absorbing material at-10 to 10 ℃ for drying treatment for 48 to 120 hours;
2) carbonizing the porous aerogel with the sheet structure obtained in the step 1) at high temperature in vacuum or inert atmosphere to obtain graphene; the temperature of the carbonization treatment is 1000-2500 ℃, and the time is 0.5-6 h.
2. The method for preparing graphene according to claim 1, wherein the biomass carbon source material is one or more of lignin, alkali lignin, hydroxyethyl cellulose, tannic acid and sodium alginate.
3. The method for preparing graphene according to claim 1, wherein the solvent is deionized water, an organic solvent, an alkaline aqueous solution or a mixed solution of an organic solvent and deionized water.
4. The method for preparing graphene according to claim 3, wherein the concentration of the alkaline aqueous solution is 1-20%, and the alkali in the alkaline aqueous solution is sodium hydroxide or potassium hydroxide; the organic solvent is tert-butanol.
5. The method for preparing graphene according to claim 1, wherein the thickness of the aerogel is 10-500 nm.
6. The method for preparing graphene according to claim 1, wherein the inert protective atmosphere is argon, nitrogen, helium or neon.
7. Graphene obtained by the preparation method according to any one of claims 1 to 6.
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| CN110803695A (en) * | 2019-10-29 | 2020-02-18 | 浙江工业大学 | Method for preparing graphene by using large-sized seaweed as raw material |
| CN111470495B (en) * | 2020-04-24 | 2023-05-12 | 山东龙力生物科技股份有限公司 | Raw material for preparing graphene and method for preparing graphene by using raw material |
| CN113247887B (en) * | 2021-04-13 | 2022-08-23 | 齐鲁工业大学 | Preparation method of hierarchical porous graphene and application of hierarchical porous graphene |
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