CN110550621B - Graphene and preparation method thereof - Google Patents
Graphene and preparation method thereof Download PDFInfo
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- CN110550621B CN110550621B CN201810539047.3A CN201810539047A CN110550621B CN 110550621 B CN110550621 B CN 110550621B CN 201810539047 A CN201810539047 A CN 201810539047A CN 110550621 B CN110550621 B CN 110550621B
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- C01—INORGANIC CHEMISTRY
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- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
- C01B32/19—Preparation by exfoliation
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- C01B32/21—After-treatment
- C01B32/22—Intercalation
- C01B32/225—Expansion; Exfoliation
Abstract
The invention relates to the field of functional materials, and discloses graphene and a preparation method thereof, wherein the graphene is prepared into 0.01-1 per thousand by weight of graphene aqueous dispersion, the graphene aqueous dispersion is stood for 1 hour, the absorbances of upper graphene aqueous dispersion, middle graphene aqueous dispersion and bottom graphene aqueous dispersion with the same volume are respectively measured at the same temperature, the relative deviation of the absorbances of the upper graphene aqueous dispersion, the middle graphene aqueous dispersion and the bottom graphene aqueous dispersion is not higher than 10%, preferably less than or equal to 5%, and the relative deviation of the absorbances of the upper graphene aqueous dispersion, the middle graphene aqueous dispersion and the bottom graphene aqueous dispersion is not higher than 20%, preferably less than or equal to 10% after the graphene is stood for 12 hours. The graphene provided by the invention can be stably dispersed in water, has good dispersibility in water, solves the problem of poor compatibility with other materials due to inherent hydrophobicity of a carbon material to a certain extent, and expands the application range of the graphene in other materials.
Description
Technical Field
The invention relates to graphene and a preparation method thereof, in particular to graphene with good water dispersibility and a preparation method thereof.
Background
The unique two-dimensional structure of graphene makes it have a structure that can be as high as 2600cm2Specific surface area per gram, high Young modulus and carrier mobility, excellent conductivity, thermal conductivity, mechanical property, light transmittance and the like. Among the known materials, graphene is the substance of highest known strength by humans, and is more than 100 times that of steel. The graphene is also nanocompositeAn additive to the material. With the continuous and deep research on graphene, the application range of graphene is continuously expanded, so that the preparation of graphene becomes an important research topic.
However, due to the inherent hydrophobicity of the carbon material, graphene produced by the prior art is difficult to be fully dispersed in water, the dispersion stability in water is poor, and "water-soluble" graphene capable of being well dispersed in water is difficult to obtain, so how to solve the problem of the dispersibility of graphene in water is a difficult point and a key for obtaining the "water-soluble" graphene. The solution is that graphene is modified usually, but the graphene has stable chemical properties, and a large amount of strong acid and strong oxidant such as concentrated sulfuric acid, potassium permanganate and the like are required to be used for oxidizing the graphene (such as oxidized graphene) in order to perform modification, and then the oxidized graphene is subjected to graft modification through chemical reaction. However, oxidation of graphene by strong acids and strong oxidants not only destroys the structure of graphene, but also degrades its performance. In addition, due to poor water dispersibility of graphene, graphene cannot be uniformly dispersed in other materials, such as paint, plastic, resin, rubber, etc., which greatly limits the application of graphene.
Therefore, in view of the problems of poor graphene dispersibility and poor compatibility between the obtained graphene and other materials in the methods for preparing graphene in the prior art, the development of new methods for preparing graphene is still pending for further research, and the present invention is proposed.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide graphene with good water dispersibility and a preparation method thereof.
In order to achieve the above object, in one aspect of the present invention, graphene is prepared into a graphene aqueous dispersion with a content of 0.01 to 1 wt%, and is left standing for 1h, and then absorbances of upper, middle and bottom graphene aqueous dispersions of the same volume are respectively measured at the same temperature, wherein a relative deviation of the absorbances of the upper, middle and bottom graphene aqueous dispersions is not higher than 10%, and preferably not higher than 5%, and a relative deviation of the absorbances of the upper, middle and bottom graphene aqueous dispersions is not higher than 20%, and preferably not higher than 10%, after the graphene aqueous dispersion is left standing for 12 h.
Preferably, the assay method comprises: respectively measuring the absorbances of upper, middle and bottom graphene aqueous dispersions with the same volume, respectively recording the absorbances as S1, S2, S3, S1, S2 or S3 and the average values of S1, S2 and S3 in the measurement, respectively recording the absolute values of the differences as RS1, RS2 and RS3, and recording the percentages of the ratios of RS1, RS2 and RS3 to the average values of S1, S2 and S3 in the measurement as DS1, DS2 and DS 3; standing for 1h, wherein the ranges of DS1, DS2 and DS3 are 0.1-8, 0.1-8 and 0.1-10 respectively, preferably 0.1-5, 0.1-5 and 0.1-8; after standing for 12h, the ranges of DS1, DS2 and DS3 are 0.1-10, 0.1-10 and 0.1-20 respectively, preferably 0.1-5, 0.1-5 and 0.1-10 respectively.
The second aspect of the present invention provides a preparation method of graphene, wherein the preparation method comprises the following steps:
(1) in the presence of ammonia or ammonium salt, graphite and an intercalating agent are subjected to contact reaction to obtain a graphite intercalation compound;
(2) the graphite intercalation compound obtained in the step (1) is in contact reaction with an oxidant so as to oxidize the intercalation agent in the graphite intercalation compound and realize the interlayer stripping of the graphite intercalation compound;
(3) and (3) recovering the product obtained in the step (2) to obtain graphene powder.
Preferably, in step (1), the intercalation agent is selected from at least one of hydrazine hydrate, carbon disulfide, elemental phosphorus, elemental sulfur, ferric chloride and potassium iodide, and the intercalation agent is more preferably selected from one or more of elemental sulfur, elemental phosphorus and hydrazine hydrate; in the step (2), the oxidizing agent is selected from at least one of air, oxygen, ozone, chlorine dioxide, chlorine gas, hypochlorous acid, nitric acid, hydrogen peroxide, benzoyl peroxide and dicumyl peroxide, and more preferably, the oxidizing agent is selected from one or more of hydrogen peroxide, ozone and benzoyl peroxide.
In a third aspect, the present invention provides a graphene prepared by the method of the present invention.
Compared with the prior art, the invention has the beneficial effects that:
1) the graphene provided by the invention is different from the traditional common graphene, can be fully and stably dispersed in water, and has good dispersibility in water, so that the problem of the hydrophobicity of the traditional graphene is changed, the problem of poor compatibility with other materials due to the inherent hydrophobicity of a carbon material is solved to a certain extent, and the application range of the graphene in other materials is expanded.
2) The preparation method of the graphene provided by the invention has no special reaction equipment and condition requirements, can be carried out on the existing industrial equipment, and has the advantages of low consumption of used oxidant, low process emission, simple, quick, environment-friendly, easy operation and the like in the preparation process, and is easy to industrialize.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The graphene provided by the invention has good and stable dispersion performance in water. In the invention, the stability of the graphene aqueous dispersion is defined by preparing the graphene aqueous dispersion and standing, and measuring the absolute deviation and the relative deviation of the absorbance of the graphene aqueous dispersion sampled at different positions after standing for different times under the same conditions.
Specifically, according to the present invention, an aqueous graphene dispersion having a content of 0.01 to 1% by weight is prepared, and absorbances of upper, middle and bottom aqueous graphene dispersions of the same volume are measured at the same temperature, respectively, and the absolute values of the differences between S1, S2, S3, S1, S2 or S3 and the average values of S1, S2 and S3 in the measurement are recorded as RS1, RS2 and RS3, that is, the absolute deviation values (absolute deviation value ═ the arithmetic average value of individual measurement values — multiple measurements |), and the ratios between RS1, RS2 and RS3 and the average values of S1, S2 and S3 in the measurement are recorded as percentages DS1, DS2 and DS 3; that is, the relative deviation values (the relative deviation value is the percentage of the absolute deviation of a certain measurement to the average value and is used for measuring the deviation degree of a single measurement result from the average value) are recorded, and after standing for 1h, the ranges of DS1, DS2 and DS3 are 0.1-8, 0.1-10, preferably 0.1-5, 0.1-5 and 0.1-8 respectively; after standing for 12h, the ranges of DS1, DS2 and DS3 are 0.1-10, 0.1-10 and 0.1-20 respectively, preferably 0.1-5, 0.1-5 and 0.1-10 respectively. The smaller the numerical values of DS1, DS2 and DS3 after standing for 1 hour, the better the water dispersibility of graphene. The smaller the difference between the numerical values of DS1, DS2 and DS3 after standing for 1h and the numerical values of DS1, DS2 and DS3 after standing for 12h respectively, the better the water dispersibility stability of the graphene is.
According to the invention, 0.01-1 wt% of graphene aqueous dispersion is prepared, preferably 0.02-0.5 wt% of graphene aqueous dispersion is prepared, after standing for 1h, samples are taken from different positions of the upper part, the middle part and the lower part of the graphene aqueous dispersion, the absorbance of the upper part, the middle part and the bottom graphene aqueous dispersion is measured, the relative deviation is not higher than 10%, preferably less than or equal to 5%, after standing for 12h, samples are taken from different positions of the upper part, the middle part and the lower part of the graphene aqueous dispersion again, and the absorbance of the upper part, the middle part and the bottom graphene aqueous dispersion is measured, the relative deviation is not higher than 20%, preferably less than or equal to 10%. Therefore, the graphene provided by the invention has good and stable dispersibility in water. The number of measurements per sampling site is usually 2 to 10, preferably 3 to 8, and the average value is used as the measurement result by default.
According to the invention, the measurement temperature of the graphene dispersibility can be normal temperature to 100 ℃, and preferably, the measurement temperature of the graphene dispersibility is 20-60 ℃.
According to the present invention, the preparation method of graphene comprises the following steps:
(1) in the presence of ammonia or ammonium salt, graphite and an intercalating agent are subjected to contact reaction to obtain a graphite intercalation compound;
(2) the graphite intercalation compound obtained in the step (1) is in contact reaction with an oxidant so as to oxidize the intercalation agent in the graphite intercalation compound and realize the interlayer stripping of the graphite intercalation compound;
(3) and (3) recovering the product obtained in the step (2) to obtain graphene powder.
The layered structure of graphite allows some voids to exist between layers, so that under certain conditions, atoms (or molecules) of certain reactants (such as acid, alkali, halogen, etc.) can enter the interlayer gaps and form an intercalation compound or intercalation compound with the carbon network. In the preparation method of the graphene, in the step (1), in the presence of ammonia or ammonium salt, the graphite is in contact reaction with the intercalation agent, so that the intercalation reaction is more sufficient, the consumption of the intercalation agent is reduced, the treatment temperature of the intercalation reaction can be properly reduced, and the total emission in the preparation process of the graphene is reduced. Wherein, the total discharge means reducing the influence of total waste water and/or waste gas and/or waste residue and the like on the environment in the graphene preparation process. The inventors surprisingly found that the dispersion stability of the graphene prepared by the method in water can be greatly improved.
According to the present invention, in step (1), the intercalating agent may be a respective intercalating agent conventionally used in the art, for example, the intercalating agent may be selected from at least one of hydrazine hydrate, carbon disulfide, elemental phosphorus, elemental sulfur, ferric chloride, and potassium iodide. In the step (2), the oxidation may be a respective oxidizing agent conventionally used in the art, for example, the oxidizing agent may be selected from at least one of inorganic oxidizing agents and organic oxidizing agents. Specifically, the oxidizing agent may be selected from at least one of air, oxygen, ozone, chlorine dioxide, chlorine gas, hypochlorous acid, nitric acid, hydrogen peroxide, benzoyl peroxide, and dicumyl peroxide.
According to the invention, a specific intercalator and an oxidant are combined for use, firstly, in the presence of ammonia or ammonium salt, the specific intercalator is utilized to prepare an intercalation compound, and then the oxidant is utilized to remove the intercalator to prepare the graphene. The inventors surprisingly found that the dispersion stability of the prepared graphene in water can be further improved by adopting the preferable combination of the intercalation agent and the oxidizing agent. That is, in step (1), the intercalation agent is preferably selected from at least one of hydrazine hydrate, carbon disulfide, elemental phosphorus and elemental sulfur, and more preferably, the intercalation agent is selected from one or more of elemental sulfur, elemental phosphorus and hydrazine hydrate; preferably, in the step (2), the oxidizing agent is one or more selected from hydrogen peroxide, ozone and benzoyl peroxide. Most preferably, in step (1), the intercalation agent is elemental sulfur or a combination of elemental sulfur and elemental phosphorus and/or hydrazine hydrate, and when the intercalation agent selects elemental sulfur to be used in combination with other intercalation agents, the mass ratio of elemental sulfur to the total amount of elemental phosphorus and hydrazine hydrate is preferably 1: 0.1-1. In the step (2), the most preferable combination of the oxidant and the oxidant is hydrogen peroxide and/or ozone, so that the dispersion stability of the prepared graphene in water can be further improved, and the quality of the graphene can be improved.
According to the invention, in the step (1), the mass ratio of the intercalation agent to graphite can be 1-120:1, and in order to further prepare graphene with excellent quality, the mass ratio of the intercalation agent to graphite is preferably 2-100:1, and more preferably 5-50: 1.
According to the invention, in the step (1), in the process of carrying out contact reaction between graphite and the intercalator to prepare the graphite intercalation compound, the contact mode of the intercalator and the graphite is not particularly limited, and when the intercalator is used in combination of a plurality of types, the intercalator can be respectively mixed with the graphite (specifically, the intercalator can be added into the graphite and uniformly mixed), and the sequence of the contact of each intercalator and the graphite does not particularly influence the quality of the obtained graphite intercalation compound.
According to the present invention, in step (1), although it is sufficient if the graphite is brought into contact with an intercalating agent in the presence of ammonia or an ammonium salt to obtain a graphite intercalation compound, it is preferably carried out in the form of NH3The weight ratio of graphite to ammonia can be 1:0.01-2, preferably 1: 0.02-1; by NH3The weight ratio of graphite to ammonium salt may be 1:0.02 to 5, preferably 1:0.05 to 2. Wherein the ammonia may be present in the form of at least one of ammonia gas, liquid ammonia, and a solution of ammonia, and more preferably, the ammonia is ammonia gas and/or liquid ammonia, and most preferably liquid ammonia from the viewpoint of convenience. Wherein the ammonia solution can be ammonia water solution or ammoniaThe concentration of the alcohol solution of (3) and the solution of ammonia is also not particularly limited and may be, for example, 5 to 40% by weight. The ammonium salt may be selected from one or more of ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium acetate, ammonium sulfates, ammonium phosphates, and the like.
According to the invention, in the step (1), since the graphite is contacted with the intercalating agent in the presence of ammonia or ammonium salt to react, the intercalation reaction can be more sufficient, the amount of the intercalating agent can be reduced, and the processing temperature of the intercalation reaction can be properly reduced, in the step (1), the conditions of the contact reaction comprise: the reaction temperature may be 80 to 200 ℃, preferably 100 ℃ to 180 ℃, and the reaction time may be 1 to 24 hours, preferably 2 to 12 hours.
In the present invention, in step (1), the contact reaction of graphite and the intercalant may be carried out under stirring for the purpose of more complete reaction. The stirring rate may be suitably selected in accordance with the actual conditions, and for example, the stirring rate may be 20 to 2000 rpm, preferably 50 to 1000 rpm. Furthermore, preferably, in step (1), after the graphite intercalation compound is obtained, a step of washing and drying the graphite intercalation compound may be further included, and the specific operation of washing and drying is well known to those skilled in the art, for example, the obtained mixture may be washed to neutrality with diluted hydrochloric acid and deionized water, and then subjected to suction filtration and drying. The method of filtration after washing is well known to those skilled in the art, and for example, suction filtration may be employed, and the suction filtration equipment and the suction filtration conditions are not particularly limited and may be selected conventionally by those skilled in the art. In the present invention, the drying method may be vacuum drying, freeze drying, spray drying, etc., and the drying equipment and drying conditions are not particularly limited and may be selected conventionally by those skilled in the art.
According to the present invention, the graphite may be selected from one or more of natural flake graphite, microcrystalline graphite, and synthetic graphite. The flake graphite is natural crystalline graphite which is shaped like fish scales and has a layered structure. The microcrystalline graphite is also called earthy graphite powder, amorphous graphite powder and black lead powder, and belongs to aphanitic graphite. The synthetic graphite is also called artificial graphite or artificial graphite, and in a broad sense, all graphite materials obtained by organic carbonization and graphitization high-temperature treatment can be called artificial graphite, such as carbon fiber, pyrolytic carbon, foam graphite and the like, while the artificial graphite in a narrow sense generally refers to a massive solid material prepared by taking a carbon raw material with low impurity content as an aggregate, coal pitch and the like as a binder and performing the procedures of batching, kneading, molding, carbonization, graphitization and the like, such as static pressure graphite and the like. The carbon content at the time of the lower content of the graphite impurity may be 99% by weight or more (i.e.,. gtoreq.99% by weight), preferably 99.99% by weight or more (i.e.,. gtoreq.99.99% by weight), and the average particle size of the graphite may be 30 to 500 mesh, preferably 50 to 350 mesh.
According to the invention, in the step (2), the conditions for the contact reaction of the graphite intercalation compound obtained in the step (1) and the oxidant are related to the selection of the oxidant, but only the conditions are required to ensure that the reaction of the oxidant is promoted to oxidize and decompose the intercalation agent in the graphite intercalation compound under the corresponding reaction conditions.
Specifically, the oxidant may be air and/or oxygen, and the contact reaction conditions include: the reaction temperature may be 200-600 deg.C, preferably 300-500 deg.C, and the reaction time may be 0.1-8 hours, preferably 0.2-5 hours. Wherein, the dosage of the oxidant can be 2 to 10 times of the theoretical value of oxygen demand for decomposing the intercalating agent by the mass of the oxygen.
The oxidant may be selected from one or more of ozone, chlorine and chlorine dioxide, and the contact reaction conditions include: the reaction temperature may be 20 to 100 deg.C, preferably 30 to 80 deg.C, and the reaction time may be 0.1 to 8 hours, preferably 0.2 to 4 hours. The amount of oxidizing agent used may be from 1 to 5 times the theoretical amount of oxidizing agent used to decompose the intercalant.
The oxidant can be hypochlorous acid and/or nitric acid, and the contact reaction conditions comprise: the reaction temperature may be 30 to 80 ℃ and preferably 40 to 70 ℃ and the reaction time may be 1 to 8 hours and preferably 2 to 4 hours. The mass ratio of oxidant to graphite may be 0.5-10:1, preferably 1-8: 1.
The oxidant may be hydrogen peroxide, and the contact reaction conditions include: the reaction temperature may be 30 to 80 deg.C, preferably 40 to 60 deg.C, and the reaction time may be 0.5 to 8 hours, preferably 1 to 6 hours. The hydrogen peroxide is generally used in the form of an aqueous solution thereof, and the mass ratio of hydrogen peroxide to graphite may be 0.5 to 5:1, preferably 0.75 to 2: 1; wherein the concentration of the aqueous hydrogen peroxide solution is generally 10 to 70% by weight.
The oxidant can be benzoyl peroxide and/or dicumyl peroxide, and the contact reaction conditions comprise: the reaction temperature may be 100-150 deg.C, preferably 110-140 deg.C, and the reaction time may be 4-12 hours, preferably 5-10 hours. The mass ratio of oxidant to graphite may be 0.5-10:1, preferably 1-8: 1.
Preferably, when the oxidizing agents are used in a plurality of combinations, the amount of each oxidizing agent can be reduced to 1/3-1/2 in the amount of the oxidizing agent used alone.
In the present invention, in the step (2), in order to allow the reaction to be more sufficient, when the oxidizing agent is in a liquid phase, the graphite intercalation compound obtained in the step (1) may be contacted with the oxidizing agent while stirring. The stirring rate may be suitably selected in accordance with the actual operation, and for example, the stirring rate may be 50 to 1000 rpm.
According to the invention, the method further comprises a step (3): and (3) recovering the product obtained in the step (2). The recovery process and steps can be carried out with reference to the prior art. For example, the recovery process may include optional filtration and washing and drying steps, the particular methods and conditions of which are routinely selected by those skilled in the art. In addition, in the present invention, the drying manner may be vacuum drying, freeze drying, spray drying, etc., and the drying equipment and drying conditions are not particularly limited, and may be selected conventionally by those skilled in the art, and are not described herein again.
The invention also provides graphene prepared by the method.
The present invention will be described in detail below by way of examples.
Unless otherwise specified, various materials used below are commercially available.
The graphene nanopowder prepared in the following manner is graphene with an atomic layer of 1-10.
In the following examples, two decimal places were retained for the relative deviation in absorbance.
Example 1
This example is intended to illustrate the process for preparing graphene provided by the present invention.
(1) Under the stirring speed of 300 revolutions per minute, uniformly mixing natural crystalline flake graphite with the average particle size of 325 meshes and the carbon content of more than or equal to 99.99 percent, liquid ammonia and elemental sulfur in a reaction kettle, wherein the weight ratio of the graphite to the liquid ammonia is 1:0.1, the weight ratio of the graphite to the elemental sulfur is 1:10, and contacting for 12 hours at the reaction temperature of 120 ℃.
(2) And (3) introducing ozone (the volume concentration of the ozone is 50%, and the balance is oxygen) into the reaction kettle, and contacting for 5 hours at the reaction temperature of 60 ℃ to obtain the graphene nanosheet, wherein the introduction amount of the ozone is 5 times of the theoretical dosage used for decomposing the intercalating agent.
(3) Washing the obtained graphene nanosheets to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference between S1 or S2 or S3 and the average value of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement are 0.96%, 1.65% and 2.48% respectively. After standing for 12 hours, the samples were measured 5 times, and the amounts of DS1, DS2 and DS3 were 1.26%, 2.52% and 4.21%, respectively.
Example 2
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1, except that in step (1), liquid ammonia was replaced by an equal amount of ammonium nitrate.
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentage of the ratio of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement was 1.11% for DS1, 1.75% for DS2, and 2.58% for DS 3. After standing for 12 hours again, the DS1, DS2 and DS3 were measured 5 times and ranged 1.48%, 2.69% and 4.98%, respectively.
Example 3
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1, except that in step (1), liquid ammonia was replaced by an equal amount of ammonium sulfate.
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentage of the ratio of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement was 1.21% for DS1, 1.89% for DS2, and 2.69% for DS 3. After standing for 12 hours again, the samples were measured 5 times, and the ranges of DS1, DS2 and DS3 were 1.56%, 2.82% and 5.05%, respectively.
Example 4
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1 except that in step (1) an equal amount of carbon disulphide was used instead of elemental sulphur.
Washing the graphene nanosheets prepared in the embodiment to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference between S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement were 3.19%, 3.86% and 4.17% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 4.03%, 4.85% and 6.28%, respectively.
Example 5
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1, except that in step (1), elemental sulfur was replaced with equal amounts of phosphorus powder.
Washing the graphene nanosheets prepared in the embodiment to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference between S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2 and RS3 to the average of S1, S2 and S3 in this measurement are 1.01%, 1.77% and 2.55% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 1.25%, 2.78% and 4.34%, respectively.
Example 6
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1, except that in step (2), ozone was replaced with an equimolar amount of oxygen, and the reaction temperature of step (2) was 300 ℃.
Washing the graphene nanosheets prepared in the embodiment to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference between S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement were 4.11%, 4.36% and 6.04% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 4.55%, 4.85% and 6.28%, respectively.
Example 7
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 1, except that, in the step (2), an equimolar amount of hydrogen peroxide (aqueous solution having a concentration of 30% by mass) was used instead of ozone.
Washing the graphene nanosheets prepared in the embodiment to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference between S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement are 1.33%, 2.14% and 3.01% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 1.73%, 3.36% and 5.37%, respectively.
Example 8
This example is intended to illustrate the process for preparing graphene provided by the present invention.
(1) Under the stirring speed of 300 revolutions per minute, uniformly mixing natural crystalline flake graphite with 325 meshes and carbon content of more than or equal to 99.99 percent, ammonium chloride, elemental sulfur and hydrazine hydrate in a reaction kettle, wherein the weight ratio of the graphite to the ammonium chloride is 1:1, and the weight ratio of the graphite to the total amount of the elemental sulfur and the hydrazine hydrate is 1:10 (the mass ratio of the elemental sulfur to the hydrazine hydrate is 1:0.5), contacting for 8 hours at the reaction temperature of 130 ℃, transferring a reaction product into suction filtration equipment after the reaction is finished and cooled to room temperature, washing by using dilute hydrochloric acid with the concentration of 2 weight percent, repeatedly washing by using deionized water to be neutral, and drying for 2 hours at the temperature of 80 ℃.
(2) And (2) placing the graphite intercalation compound obtained in the step (1) into a reaction kettle, introducing an oxidant ozone (the volume concentration of the ozone is 50%, and the balance of oxygen), and contacting for 3 hours at the reaction temperature of 35 ℃, wherein the introduction amount of the ozone is 3 times of the theoretical dosage used for decomposing the intercalation agent.
(3) Washing the obtained graphene nanosheets to prepare a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute value of the difference between S1 or S2 or S3 and the average value of S1, S2 and S3 in the measurement is RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement are 0.46%, 0.65% and 0.97% respectively. After standing for 12 hours again, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 0.65%, 0.85% and 1.16%, respectively.
Example 9
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 8, except that crystalline graphite was substituted for the crystalline flake graphite of example 8.
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2 and RS3 to the average of S1, S2 and S3 in this measurement are 0.53%, 0.75% and 1.01% respectively. After standing for 12 hours again, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 0.72%, 0.98% and 1.21%, respectively.
Example 10
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 8, except that crystalline graphite was used instead of crystalline flake graphite in example 8, and in step (2), the oxidant was used instead of ozone, and the oxidation contact reaction conditions included: the reaction temperature was 100 ℃ and the reaction time was 6 hours.
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement are 0.86%, 1.08% and 1.23% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 0.98%, 1.22% and 1.39%, respectively.
Example 11
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 8, except that, in the step (2), the oxidizing agent was nitric acid (the mass percentage concentration was 40%, and the mass ratio of nitric acid to graphite was 5: 1).
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentage of the ratio of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement was 3.82% for DS1, 4.08% for DS2, and 4.21% for DS 3. After standing for 12 hours again, the samples were measured 5 times, and the ranges of DS1, DS2 and DS3 were 4.03%, 4.22% and 4.39%, respectively.
Example 12
This example is intended to illustrate the process for preparing graphene provided by the present invention.
Graphene was prepared according to the method of example 8 except that in step (1) the intercalant replaced the total amount of elemental sulphur and hydrazine hydrate with the same weight of ferric chloride.
Preparing the graphene nano powder prepared in the embodiment into a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbance of the upper part, the middle part and the bottom part of the prepared graphene aqueous dispersion at 25 ℃, respectively recording the absorbance as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1 or S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentage of the ratio of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement was 3.96% for DS1, 4.22% for DS2, and 4.75% for DS 3. After standing for 12 hours again, the samples were measured 5 times, and the ranges of DS1, DS2 and DS3 were 4.18%, 4.89% and 6.35%, respectively.
Comparative example 1
Graphene was prepared according to the method of example 12 except that, in step (1), ammonia chloride was not added.
Preparing a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbances of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1, S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement were 6.64%, 8.58% and 12.16% respectively. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 11.37%, 15.52% and 23.49%, respectively.
Comparative example 2
Graphene was prepared according to the method of example 12 except that, in step (1), ammonia chloride was not added. The reaction temperature in the step (1) is increased to 350 ℃, and the reaction time is 12 h.
Preparing a graphene aqueous dispersion with the content of 0.1 weight per thousand, standing for 1h, respectively measuring the absorbances of the upper part, the middle part and the bottom part of the graphene aqueous dispersion at 25 ℃, respectively recording as S1, S2 and S3, and measuring for 5 times, wherein the absolute values of the difference values of S1, S2 or S3 and the average values of S1, S2 and S3 in the measurement are RS1, RS2 and RS 3. The percentages DS1, DS2 and DS3 of the ratios of RS1, RS2, RS3 to the average of S1, S2, S3 in this measurement were 4.57%, 6.82% and 10.85% respectively for DS2 and S3. After standing for 12 hours, the samples were measured 5 times, and the values of DS1, DS2 and DS3 were 9.31%, 13.63% and 20.16%, respectively.
As can be seen from comparison of the data of comparative examples 1 and 2 with example 12, when ferric chloride is used as an intercalating agent and ozone is used as an oxidizing agent, the dispersibility of the obtained graphene is poor even if the reaction temperature of step (1) is increased in the absence of ammonia or ammonium salt.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (22)
1. The graphene is characterized in that after the graphene is prepared into graphene aqueous dispersion with the content of 0.01-1 per thousand by weight and is stood for 1 hour, the absorbance of upper graphene aqueous dispersion, middle graphene aqueous dispersion and bottom graphene aqueous dispersion with the same volume are respectively measured at the same temperature, the relative deviation of the absorbance of the upper graphene aqueous dispersion, the middle graphene aqueous dispersion and the bottom graphene aqueous dispersion is not higher than 10%, and the relative deviation of the absorbance of the upper graphene aqueous dispersion, the middle graphene aqueous dispersion and the bottom graphene aqueous dispersion is not higher than 20% after the graphene is stood for 12 hours;
the preparation method of the graphene comprises the following steps:
(1) in the presence of ammonia or ammonium salt, graphite and an intercalating agent are subjected to contact reaction to obtain a graphite intercalation compound; in the step (1), the intercalation agent is elemental sulfur or a combination of elemental sulfur and elemental phosphorus and/or hydrazine hydrate, and when the intercalation agent selects elemental sulfur to be used in combination with other intercalation agents, the mass ratio of the elemental sulfur to the total amount of the elemental phosphorus and the hydrazine hydrate is 1: 0.1-1; the ammonia salt is selected from one or more of ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium sulfate and ammonium phosphate; the conditions of the contact reaction include: the reaction temperature is 80-200 ℃, and the reaction time is 1-24 hours;
(2) the graphite intercalation compound obtained in the step (1) is in contact reaction with an oxidant so as to oxidize the intercalation agent in the graphite intercalation compound and realize the interlayer stripping of the graphite intercalation compound;
(3) and (3) recovering the product obtained in the step (2) to obtain graphene powder.
2. The graphene according to claim 1, wherein after the graphene is prepared into an aqueous graphene dispersion solution with a content of 0.01 to 1 wt% and is left standing for 1 hour, the absorbance of the upper, middle and bottom aqueous graphene dispersion solutions with the same volume is respectively measured at the same temperature, the relative deviation of the absorbance of the upper, middle and bottom aqueous graphene dispersion solutions is less than or equal to 5%, and the relative deviation of the absorbance of the upper, middle and bottom aqueous graphene dispersion solutions is less than or equal to 10% after the graphene is left standing for 12 hours.
3. The graphene according to claim 1, wherein the assay method comprises: respectively measuring the absorbances of upper, middle and bottom graphene aqueous dispersions with the same volume, respectively recording the absorbances as S1, S2, S3, S1, S2 or S3 and the average values of S1, S2 and S3 in the measurement, respectively recording the absolute values of the differences as RS1, RS2 and RS3, and recording the percentages of the ratios of RS1, RS2 and RS3 to the average values of S1, S2 and S3 in the measurement as DS1, DS2 and DS 3; standing for 1h, wherein the ranges of DS1, DS2 and DS3 are 0.1-8, 0.1-8 and 0.1-10 respectively; standing for 12h, the ranges of DS1, DS2 and DS3 are 0.1-10, 0.1-10 and 0.1-20 respectively.
4. The graphene according to claim 3, wherein after standing for 1h, the ranges of DS1, DS2 and DS3 are 0.1-5, 0.1-5 and 0.1-8 respectively; after standing for 12h, the ranges of DS1, DS2 and DS3 are 0.1-5, 0.1-5 and 0.1-10 respectively.
5. The graphene according to any one of claims 1 to 4, wherein the measurement temperature is from room temperature to 100 ℃ and the number of measurements is from 2 to 10.
6. The graphene according to claim 5, wherein the measurement temperature is 20-60 ℃; the number of measurements was 3-8.
7. A preparation method of graphene is characterized by comprising the following steps:
(1) in the presence of ammonia or ammonium salt, graphite and an intercalating agent are subjected to contact reaction to obtain a graphite intercalation compound; in the step (1), the intercalation agent is elemental sulfur or a combination of elemental sulfur and elemental phosphorus and/or hydrazine hydrate, and when the intercalation agent selects elemental sulfur to be used in combination with other intercalation agents, the mass ratio of the elemental sulfur to the total amount of the elemental phosphorus and the hydrazine hydrate is 1: 0.1-1; the ammonia salt is selected from one or more of ammonium nitrate, ammonium carbonate, ammonium bicarbonate, ammonium chloride, ammonium bromide, ammonium fluoride, ammonium sulfate and ammonium phosphate; the conditions of the contact reaction include: the reaction temperature is 80-200 ℃, and the reaction time is 1-24 hours;
(2) the graphite intercalation compound obtained in the step (1) is in contact reaction with an oxidant so as to oxidize the intercalation agent in the graphite intercalation compound and realize the interlayer stripping of the graphite intercalation compound;
(3) and (3) recovering the product obtained in the step (2) to obtain graphene powder.
8. The production method according to claim 7, wherein in the step (2), the oxidizing agent is at least one selected from the group consisting of air, oxygen, ozone, chlorine dioxide, chlorine gas, hypochlorous acid, nitric acid, hydrogen peroxide, benzoyl peroxide and dicumyl peroxide.
9. The method according to claim 8, wherein in the step (2), the oxidizing agent is one or more selected from the group consisting of hydrogen peroxide, ozone, and benzoyl peroxide.
10. The production method according to any one of claims 7 to 9, wherein in step (1), the mass ratio of the intercalant to graphite is 1 to 120: 1.
11. The preparation method according to claim 10, wherein in the step (1), the mass ratio of the intercalation agent to graphite is 2-100: 1.
12. The preparation method according to claim 11, wherein in the step (1), the mass ratio of the intercalation agent to graphite is 5-50: 1.
13. The production method according to any one of claims 7 to 9, wherein in the step (1), NH is used as the catalyst3The weight ratio of the graphite to the ammonia is 1:0.01-2, the ammonia is at least one of ammonia gas, liquid ammonia and ammonia solution, wherein the ammonia solution is ammonia water solution or ammonia alcohol solution, and the concentration of the ammonia solution is 5-40 wt%; by NH3The weight ratio of the graphite to the ammonium salt is 1: 0.02-5.
14. The method according to claim 13, wherein in the step (1), NH is used as the catalyst3The weight ratio of the graphite to ammonia is 1:0.02-1, wherein the ammonia is ammonia gas and/or liquid ammonia; by NH3The weight ratio of the graphite to the ammonium salt is 1: 0.05-2.
15. The production method according to any one of claims 7 to 9, wherein in the step (1), the conditions of the contact reaction include: the reaction temperature is 100-180 ℃, and the reaction time is 2-12 hours.
16. The method of claim 15, wherein the contacting is performed under agitation.
17. The production method according to any one of claims 7 to 9, wherein in step (1), the graphite is selected from one or more of flake graphite, microcrystalline graphite and synthetic graphite, and the graphite has a carbon content of 99% by weight or more and an average particle size of 30 to 500 mesh.
18. The production method according to claim 17, wherein the graphite has a carbon content of 99.99% by weight or more and an average particle size of 50 to 350 mesh.
19. The production method according to any one of claims 7 to 9, wherein in step (2):
when the oxidant is air and/or oxygen, the contact reaction conditions comprise: the reaction temperature is 300-500 ℃, the reaction time is 0.2-5 hours, and the dosage of air and/or oxygen is 2-10 times of the theoretical value of oxygen demand for decomposing the intercalating agent by mass of the oxygen;
when the oxidant is one or more selected from ozone, chlorine and chlorine dioxide, the contact reaction conditions include: the reaction temperature is 20-100 ℃, the reaction time is 0.1-8 hours, and the dosage of one or more of ozone, chlorine and chlorine dioxide is 1-5 times of the theoretical dosage of the oxidant used for decomposing the intercalating agent;
when the oxidant is hypochlorous acid and/or nitric acid, the contact reaction conditions comprise: the reaction temperature is 30-80 ℃, the reaction time is 1-8 hours, and the mass ratio of the oxidant to the graphite is 0.5-10: 1;
when the oxidant is hydrogen peroxide, the contact reaction conditions comprise: the reaction temperature is 30-80 ℃, the reaction time is 0.5-8 hours, the hydrogen peroxide is used in the form of aqueous solution, and the mass ratio of the hydrogen peroxide to the graphite is 0.5-5: 1; the concentration of the aqueous hydrogen peroxide solution is 10 to 70 wt%;
when the oxidant is benzoyl peroxide and/or dicumyl peroxide, the contact reaction conditions comprise: the reaction temperature is 100-150 ℃, the reaction time is 4-12 hours, and the mass ratio of the oxidant to the graphite is 0.5-10: 1.
20. The production method according to claim 19, wherein in step (2):
when the oxidant is one or more selected from ozone, chlorine and chlorine dioxide, the contact reaction conditions include: the reaction temperature is 30-80 ℃, and the reaction time is 0.2-4 hours;
when the oxidant is hypochlorous acid and/or nitric acid, the contact reaction conditions comprise: the reaction temperature is 40-70 ℃, the reaction time is 2-4 hours, and the mass ratio of the oxidant to the graphite is 1-8: 1;
when the oxidant is hydrogen peroxide, the contact reaction conditions comprise: the reaction temperature is 40-60 ℃, the reaction time is 1-6 hours, the hydrogen peroxide is used in the form of aqueous solution, and the mass ratio of the hydrogen peroxide to the graphite is 0.75-2: 1;
when the oxidant is benzoyl peroxide and/or dicumyl peroxide, the contact reaction conditions comprise: the reaction temperature is 110-140 ℃, the reaction time is 5-10 hours, and the mass ratio of the oxidant to the graphite is 1-8: 1.
21. The method of claim 19 or 20, wherein the contacting is performed under agitation.
22. Graphene prepared by the method of any one of claims 7-21.
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