CN108946707B - Graphene aerogel and preparation method and application thereof - Google Patents
Graphene aerogel and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the field of material engineering, and discloses a preparation method of graphene aerogel. The method is simple, rapid and efficient, and the prepared graphene aerogel is complete in spatial reticular structure, high in porosity and large in specific surface area.
Description
Technical Field
The invention relates to the field of material engineering, relates to a preparation method of graphene aerogel, and particularly relates to a method for preparing graphene aerogel by burning a solvent.
Background
The graphene aerogel is a three-dimensional porous structure material formed by connecting graphene sheet layers, has the advantages of light weight, good conductivity, super-strong elasticity, large specific surface area, oleophylic property, fire resistance, ultrahigh porosity and the like, has wide application and excellent performance in many fields of water treatment, electrochemistry, energy sources, catalysts, sensors, super capacitors, adsorption, thermal control and the like, but the real industrial application is limited by factors such as too high preparation cost and the like.
The graphene aerogel is generally obtained by replacing a solvent medium in graphene liquid-phase gel with a gas medium, and a one-step solvothermal or hydrothermal method is one of the most common methods for preparing the graphene liquid-phase gel, and has the characteristics of simplicity, high efficiency and high sample purity. The prepared graphene liquid-phase gel has surface tension in a solvent in a gel framework, and the framework can collapse under common drying conditions, so that a drying process capable of maintaining a gel porous network structure is a difficult point in the preparation of the graphene aerogel and is one of the key points of research of related scientific researchers.
In the process of preparing graphene aerogel, most researchers adopt freeze drying or supercritical drying so as to keep the microporous structure of the aerogel as complete as possible. Freeze-drying is a drying process in which an aqueous material is frozen below freezing to convert water to ice, which is then removed by converting the ice to a vapor under a relatively high vacuum. Supercritical drying is a new technology developed in recent years, the solvent in the gel is replaced mildly and quickly by using a supercritical solvent, then the supercritical solvent becomes a uniform fluid between gas and liquid when reaching the critical point of the supercritical solvent, the gas-liquid interface disappears, the capillary action disappears, and the gel cannot shrink or be structurally damaged when the fluid is discharged from the gel, so that the gel material with a complete nano-network structure is obtained. However, both drying methods require expensive equipment and harsh experimental conditions such as low temperature, high vacuum or high pressure, for example, CN104163423 discloses a method for preparing sponge graphene by freeze-drying, wherein the freeze-drying is performed for 12-24h under the conditions of-60 ℃ and less than 12Pa, the experimental period is relatively long, the yield is low, the cost is high, and the industrial production of graphene aerogel is severely limited.
Therefore, finding a graphene liquid-phase gel drying method which is simple in process and capable of completely reserving a gel microporous structure is a difficult problem to be overcome, and is directly related to whether the graphene aerogel can be produced and applied on a large scale.
Disclosure of Invention
The invention aims to solve the problems of complex operation, long time consumption and high cost in the prior art, and provides a simple, quick and efficient preparation method of graphene aerogel.
The inventor of the invention finds that the graphene aerogel can be simply, conveniently and quickly prepared by burning the combustible solvent in the graphene liquid-phase gel containing the combustible solvent, and the obtained graphene aerogel has a complete space network structure, high porosity and large specific surface area. More surprisingly, the graphene aerogel obtained by the method has a larger specific surface area than that of the aerogel obtained by a freeze-drying method, and has a great application prospect in the aspects of adsorption, catalysis and the like; compared with freeze drying, the method does not need expensive instruments and equipment, shortens the preparation period and is very beneficial to large-scale industrial production.
In order to achieve the above object, in one aspect, the present invention provides a method for preparing a graphene aerogel, the method including combusting a flammable solvent in a graphene liquid-phase gel containing the flammable solvent to obtain the graphene aerogel.
Preferably, the content of the flammable solvent in the graphene liquid-phase gel containing the flammable solvent is more than 60 wt% of all solvents.
Preferably, the graphene liquid-phase gel containing the flammable solvent contains a surfactant. More preferably, the surfactant is selected from one or more of lignosulfonate, dodecylbenzene sulfonate and dodecyl sulfate.
Preferably, the graphene liquid-phase gel containing the combustible solvent is a graphene liquid-phase gel prepared by a solvothermal method.
Preferably, the graphene liquid-phase gel containing the flammable solvent is obtained by replacing water in the graphene hydrogel prepared by a hydrothermal method with the flammable solvent.
The second aspect of the present invention provides a graphene aerogel obtained by the above method.
The third aspect of the present invention provides applications of the graphene aerogel described above in electrode materials, hydrogen storage materials, catalyst materials, heat insulating materials, and adsorbent materials.
Through the technical scheme, the preparation method disclosed by the invention is simple to operate, good in repeatability, free of special equipment, simple in process, short in preparation period and extremely low in cost, greatly improves the production efficiency, and is very beneficial to industrial mass production of the graphene aerogel. In addition, the method avoids the use of expensive drying instruments and long-time drying process, and can be quickly finished under the condition of a common laboratory.
Drawings
Fig. 1 is a graph comparing a graphene aerogel obtained in example 1 of the present invention with a graphene aerogel obtained in comparative example 1;
fig. 2 is a graph of adsorption and desorption isotherms of the graphene aerogel obtained in example 1 of the present invention;
fig. 3 is a pore size distribution diagram of the graphene aerogel obtained in example 1 of the present invention;
fig. 4 is a pore size distribution diagram of the graphene aerogel obtained in comparative example 2 of the present invention;
fig. 5 is a scanning electron microscope photograph of the graphene aerogel obtained in example 1 of the present invention;
fig. 6 is a transmission electron microscope photograph of the graphene aerogel obtained in example 1 of the present invention;
FIG. 7 is a scanning electron micrograph of graphene aerogels obtained in examples 1 to 4 of the present invention;
fig. 8 is XRD patterns of the graphene aerogels obtained in examples 1 to 3 of the present invention and comparative example 1.
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 preparation method of the graphene aerogel comprises the step of combusting the combustible solvent in the graphene liquid-phase gel containing the combustible solvent to obtain the graphene aerogel.
According to the invention, the combustible solvent is combusted, so that the solvent in the graphene liquid-phase gel is removed, the graphene liquid-phase gel is dried to obtain the graphene aerogel, and the combustible solvent is combusted, so that the gel volume is basically unchanged or slightly changed before and after combustion, and the chemical property of the obtained aerogel is not influenced.
In the present invention, the manner of burning the flammable solvent is not particularly limited, and may be selected from one or more of open flame ignition, heat radiation ignition, and arc ignition. The conditions for the combustion of the flammable solvent are not particularly limited, and the complete combustion of the flammable solvent is only required. For example, the ambient temperature of combustion may be normal or elevated (e.g., above 5℃.) and the oxygen concentration is greater than or equal to the minimum oxygen concentration required for combustion of the flammable solvent.
In the present invention, the flammable solvent may be any organic solvent that can be removed by combustion, and may be an organic solvent that can be used in the conventional solvothermal method for preparing a graphene liquid gel, or an organic solvent that can be used to replace water in a graphene hydrogel prepared by a hydrothermal method. The flammable solvent may be one or more selected from alcohols, ketones, ethers, aldehydes and acids. Preferably, the alcohol is a lower aliphatic alcohol, more preferably an aliphatic alcohol having less than 6 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, and the like; the ketone is a lower aliphatic ketone, more preferably an aliphatic ketone having less than 6 carbon atoms, such as acetone, butanone, 2-pentanone, 3-pentanone, hexanone, and the like; the ether is lower aliphatic ether, more preferably aliphatic ether with carbon number less than 6, such as methyl ether, ethyl ether, methyl ethyl ether, etc.; the aldehyde is a lower aliphatic aldehyde, more preferably an aliphatic aldehyde having less than 6 carbon atoms, such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, and the like; the acid is a lower fatty acid, and more preferably a fatty acid having less than 6 carbon atoms, for example, acetic acid, propionic acid, or the like. The flammable solvent may be one or more selected from methanol, ethanol, propanol, isopropanol, acetone, diethyl ether, formaldehyde and acetic acid, from the viewpoint of easy availability.
According to a preferred embodiment of the present invention, in order to ensure that the solvent in the graphene liquid-phase gel can be sufficiently removed by combustion, the content of the flammable solvent in the graphene liquid-phase gel containing the flammable solvent in all solvents is 60 wt% or more, more preferably 70 wt% or more, further preferably 80 wt% or more, further preferably 90 wt% or more, further preferably 95 wt% or more, further preferably 98 wt% or more, further preferably 99 wt% or more, and further preferably 99.5 wt% or more. By controlling the content of the flammable solvent in the graphene liquid-phase gel containing the flammable solvent to all the solvents within the above range, the solvent in the graphene liquid-phase gel can be sufficiently removed by combustion.
The inventor of the present invention also finds that by making the graphene liquid-phase gel containing the flammable solvent contain a surfactant, physical properties, such as specific surface area and pore size, of the graphene aerogel obtained by combustion can be further improved, and the application of the graphene aerogel is more facilitated. The theory thereof is presumed as: the surfactant can play a role in supporting a framework in the process of removing the combustible solvent by combustion, so that the collapse of a pore structure caused by the reduction of the solvent is reduced, and the graphene aerogel with high specific surface area can be obtained. In addition, through the combustion process, the surfactant can be simultaneously removed through combustion, and finally the graphene aerogel without the surfactant is obtained.
The kind of the surfactant is not particularly limited as long as it does not affect combustion of the flammable solvent, and may be a cationic surfactant, an anionic surfactant, and a nonionic surfactant. The surfactant is preferably an anionic surfactant from the viewpoint of reducing introduction of impurity ions. More preferably, the anionic surfactant is one or more selected from the group consisting of lignosulfonate, dodecylbenzene sulfonate and dodecyl sulfate, and particularly preferably lignosulfonate. The anionic surfactant may be a sodium salt, a potassium salt, a lithium salt, or the like.
In the present invention, it is preferable to provide the graphene liquid phase gel before combustion with good mechanical strength in order to further improve the mechanical strength of the obtained graphene aerogel.
According to a preferred embodiment of the present invention, the graphene liquid-phase gel containing the flammable solvent is a graphene liquid-phase gel prepared by a solvothermal method. In order to facilitate the combustion of the solvent, preferably, the combustible solvent in the graphene liquid-phase gel containing the combustible solvent is the solvent used in the solvothermal method. By using a combustible solvent as a solvent in the solvothermal method, the graphene liquid-phase gel obtained after the solvothermal method heat treatment can be directly subjected to combustion treatment by the method in the invention to obtain the graphene aerogel. When the solvent used in the solvothermal method is not easily burned, the solvent in the prepared graphene liquid-phase gel may be replaced with a flammable solvent in the same manner as the water used to replace the following graphene hydrogel.
According to another preferred embodiment of the present invention, the graphene liquid gel containing the flammable solvent is obtained by replacing water in a graphene hydrogel obtained by a hydrothermal method with the flammable solvent. Through the replacement process of replacing water with an organic solvent, the graphene hydrogel prepared through the hydrothermal reaction can also be used for preparing the graphene aerogel through the method disclosed by the invention.
The substitution method is not particularly limited, and the water in the graphene hydrogel may be substituted with a flammable solvent to obtain a graphene liquid-phase gel containing the flammable solvent. From the viewpoint of sufficiently proceeding combustion, it is preferable that the substitution is performed to a higher degree as well. The replacement may include a soaking treatment and/or a rinsing treatment.
The graphene hydrogel may be soaked in a flammable solvent as the soaking treatment, and the soaking treatment may be performed 1 time or more, preferably 1 to 3 times. In order to increase the rate of substitution, the temperature of the soaking treatment is 0 to 250 deg.C, preferably 80 to 180 deg.C. In order to carry out the metathesis reaction at a higher temperature, it may be carried out by heating in a reaction vessel. In order to ensure the replacement effect, the time of the soaking treatment is 10min or more, preferably 0.5 to 3 h. The volume of the flammable solvent used in the soaking treatment is preferably 4 to 20 volumes, and more preferably 8 to 10 volumes, based on 1 volume of the graphene hydrogel.
As the washing treatment, the graphene hydrogel may be washed with a flammable solvent. The number of rinsing treatments may be 2 or more, preferably 3 to 4. The volume of the flammable solvent used for the rinsing treatment is preferably 4 to 30 volumes, and more preferably 10 to 12 volumes, based on 1 volume of the graphene hydrogel.
In the present invention, the solvothermal method may be an existing solvothermal method that can be used to prepare a graphene liquid-phase gel. The solvothermal process comprises: and carrying out heat treatment on the organic solvent solution of the graphene oxide.
The temperature of the heat treatment in the solvothermal method may be 50 to 250 ℃, preferably 120 to 180 ℃, and the time may be 6 to 48 hours, preferably 12 to 24 hours.
The concentration of graphene oxide in the organic solvent solution of graphene oxide may be 0.2 to 10 mg/mL. In order to improve the mechanical strength of the graphene hydrogel, the concentration of the graphene oxide is preferably 1 to 5mg/mL, and more preferably 2 to 3.5 mg/mL.
In the present invention, the hydrothermal method may be an existing hydrothermal method that can be used for preparing the graphene liquid-phase gel. The hydrothermal process comprises: and carrying out heat treatment on the aqueous solution of the graphene oxide.
The temperature for the heat treatment in the hydrothermal method may be 50 to 250 ℃, preferably 120-180 ℃, and the time may be 0.5 to 48 hours, preferably 12 to 24 hours.
The concentration of graphene oxide in the aqueous solution of graphene oxide may be 0.2 to 10 mg/mL. In order to improve the mechanical strength of the graphene hydrogel, the concentration of the graphene oxide is preferably 1 to 5mg/mL, and more preferably 2 to 3.5 mg/mL.
The pH of the aqueous solution of graphene oxide is not particularly limited, and a graphene hydrogel may be prepared, and is preferably 2 to 6 or 8 to 11, more preferably 4 to 5 or 8 to 10, and particularly preferably 9 to 10.
The inventors of the present invention have also found that, by adding a surfactant to an organic solvent solution or an aqueous solution of graphene oxide (hereinafter referred to as a graphene oxide solution) before performing the heat treatment, not only the effect of the combustion treatment can be improved, but also the mechanical strength of the prepared graphene aerogel can be improved. Therefore, in the graphene liquid-phase gel containing the surfactant, the surfactant is preferably added before the heat treatment is performed. The surfactant can promote dispersion of the graphene oxide solution, so that the graphene liquid-phase gel obtained by heat treatment has a larger volume, a larger specific surface area and a larger void structure are obtained, and meanwhile, the graphene liquid-phase gel can play a role of framework support when a combustible solvent is removed by combustion, and the specific surface area of the graphene liquid-phase gel is further improved. The surfactant is not particularly limited, and may be a surfactant commonly used for preparing graphene liquid-phase gel, as long as combustion of the flammable solvent is not affected. The surfactant is preferably an anionic surfactant from the viewpoint of reducing introduction of impurity ions. More preferably, the anionic surfactant is one or more selected from the group consisting of lignosulfonate, dodecylbenzene sulfonate and dodecyl sulfate, and particularly preferably lignosulfonate. The anionic surfactant may be a sodium salt, a potassium salt, a lithium salt, or the like.
By adding the surfactant, the graphene liquid-phase gel can be prepared more easily, and the mechanical strength of the graphene liquid-phase gel is improved. The surfactant may be appropriately added as needed, and is preferably added in an amount of 0.5 to 3 parts by weight, preferably 0.5 to 2 parts by weight, and more preferably 1 to 1.5 parts by weight, relative to 1 part by weight of the graphene oxide.
In order to ensure smooth progress of the heat treatment, one or more of a reducing agent, a catalyst, and a raw material of a supporting substance are added to the graphene oxide solution before the heat treatment, as necessary. By adding the reducing agent and/or the catalyst, the graphene liquid-phase gel can be prepared when the heat treatment is carried out at a lower temperature. By adding the loading substance raw material, the modified graphene liquid-phase gel or graphene composite liquid-phase gel can be prepared.
In order to ensure that the heat treatment is sufficiently performed, before the heat treatment, an organic solvent solution or an aqueous solution of graphene oxide may be uniformly mixed, for example, by stirring and/or ultrasonic treatment, and the time may be 10min or more, preferably 0.5 to 2 hours.
The method can be widely applied to preparation of various graphene aerogels. That is to say, the graphene aerogel is not particularly limited, and the graphene aerogel may also be a reduced graphene oxide aerogel, and the graphene aerogel may also be a graphene composite aerogel formed by compounding graphene and other materials. The graphene composite aerogel can be one or more of reduced graphene oxide/oxide composite aerogel, reduced graphene oxide/hydroxide composite aerogel, reduced graphene oxide/nitride composite aerogel, reduced graphene oxide/sulfide composite aerogel, reduced graphene oxide/selenide composite aerogel, reduced graphene oxide/cyanide composite aerogel, reduced graphene oxide/fluoride composite aerogel, reduced graphene oxide/chloride composite aerogel and reduced graphene oxide/metal composite aerogel.
In the present invention, the graphene may be unmodified graphene or modified graphene, for example, graphene doped with N, B, P or the like.
The second aspect of the present invention also provides a graphene aerogel obtained according to the above method.
The third aspect of the invention also provides the application of the graphene aerogel in electrode materials, hydrogen storage materials, catalyst materials, heat insulation materials and adsorbent materials. The graphene aerogel prepared by the method provided by the invention has good electrical properties, large specific capacity, good rate capability and good cycling stability, and is particularly suitable for being used as an electrode material of a supercapacitor.
The present invention will be described in detail below by way of examples. In the following examples, scanning electron microscopes were obtained from Nippon electronics, Inc., model JSM-6390; transmission electron microscopes were purchased from japan electronics, model JEOL-2100; the instrument for testing the adsorption and desorption isotherm and the pore size distribution is purchased from Beijing Betserd instruments science and technology Limited, model 3H-2000 PSI; x-ray diffractometers were purchased from Japan science, Inc., model D/MAX-Ultima; all reagents used were commercially available analytical grade reagents.
Preparation example 1
This preparation example is used to illustrate a method for preparing graphene hydrogel by a one-step hydrothermal method.
1) Dissolving graphene oxide with a certain amount of deionized water, uniformly stirring, and performing ultrasonic treatment for 2 hours, and uniformly stirring to obtain a graphene oxide solution. And calibrating the concentration of the graphene oxide to be 2mg/mL by adopting a drying and weighing mode.
2) Preparing a graphene oxide solution with a certain concentration and a certain pH value by using the graphene oxide solution prepared in the step 1), adding a surfactant according to needs, stirring for 0.5h, transferring to a hydrothermal kettle, and carrying out hydrothermal reaction at 180 ℃ for 12 h.
3) And (4) taking out the hydrogel after the hydrothermal reaction is finished, and washing the hydrogel for 2-3 times by using deionized water.
Example 1
This example is used to illustrate the preparation method of the graphene aerogel according to the present invention.
1) Graphene hydrogel was prepared according to the method of preparation example 1 using graphene oxide solution (pH 10, containing sodium lignosulfonate 2mg/mL) at a concentration of 2 mg/mL.
2) And (3) soaking the graphene hydrogel for 24 hours by using isopropanol with the volume 5 times that of the graphene hydrogel to finish solvent replacement.
3) And directly igniting the graphene hydrogel after the replacement is finished in a fume hood, and completely combusting isopropanol to obtain graphene aerogel G1.
Example 2
This example is used to illustrate the preparation method of the graphene aerogel according to the present invention.
Graphene aerogel G2 was prepared according to the method of example 1, except that sodium lignosulfonate was replaced with the same weight of sodium dodecylbenzenesulfonate.
Example 3
This example is used to illustrate the preparation method of the graphene aerogel according to the present invention.
The process of example 1 was followed, except that sodium lignosulfonate was replaced with the same weight of sodium lauryl sulfate, to produce graphene aerogel G3.
Example 4
This example is used to illustrate the preparation method of the graphene aerogel according to the present invention.
The process was carried out according to example 1, except that sodium lignosulfonate was not used, and graphene aerogel G4 was prepared.
Comparative example 1
This comparative example is used to illustrate the preparation of graphene aerogel by a drying method at atmospheric pressure.
Steps 1) and 2) were carried out according to the method of example 1, with the difference that no surfactant was added.
And 3) directly drying the graphene hydrogel after the replacement in an oven at 50 ℃ for 5 hours to constant weight to obtain the graphene aerogel D1.
Comparative example 2
This comparative example is used to illustrate the preparation of graphene aerogel by freeze-drying.
The graphene hydrogel was prepared according to the method of step 1) in example 1, except that no surfactant was added. Pre-freezing the graphene hydrogel, placing the graphene hydrogel in a freeze dryer, simultaneously cooling the sample and a drying oven, stabilizing, and performing vacuum freeze drying for 24h to constant weight under the conditions of-50 ℃ and 8Pa to obtain the graphene aerogel D2.
Test example 1
The test example is used to illustrate a method of testing the specific surface area of the graphene aerogel.
The graphene aerogels prepared in the above examples 1 to 4 and comparative examples 1 to 2 were subjected to degassing treatment at 200 ℃ for 90min, and BET adsorption isotherms thereof were tested to calculate the maximum specific surface area of the graphene aerogels.
A comparative graph of the graphene aerogel obtained in example 1 of the present invention and the graphene aerogel obtained in comparative example 1 is shown in fig. 1; fig. 2 shows a graph of adsorption and desorption isotherms of the graphene aerogel obtained in example 1; relevant parameters of the graphene aerogels prepared in examples 1 to 4 and comparative examples 1 to 2 are shown in table 1.
TABLE 1
| Surface active agent | Specific surface area (m)2/g) | Pore size (nm) | |
| Comparative example 1 | - | 6.78 | 4.42 |
| Comparative example 2 | - | 261.59 | 3.34 |
| Example 1 | Lignosulfonic acid sodium salt | 731.77 | 6.88 |
| Example 2 | Sodium dodecyl benzene sulfonate | 610.4 | 8.33 |
| Example 3 | Sodium dodecyl sulfate | 553.52 | 8.47 |
| Example 4 | - | 405.18 | 6.16 |
Test example 2
The test example is used to illustrate a method for testing the pore size distribution of the graphene aerogel.
The pore size distributions of the graphene aerogels G1 and D2 prepared in example 1 and comparative example 2 were tested by BJH, and the results are shown in fig. 3 and 4, respectively;
as shown in fig. 3, the graphene aerogel prepared by the method of the present invention has a sharp peak in the pore size distribution curve, which indicates that the pore size distribution is uniform, and the measured pore size is about 6.88 nm. As shown in fig. 4, the pore size of the graphene aerogel prepared by freeze drying is about 3.34nm, which is much smaller than the pore size of the graphene aerogel prepared by the method of the present invention.
Test example 3
The test example is used to illustrate the microporous structure of the graphene aerogel according to the present invention.
The microstructure of the graphene aerogel G1 was observed by a scanning electron microscope, and the result is shown in fig. 5.
As can be seen from fig. 5, the graphene aerogel G1 has a good microporous structure and a uniform pore size distribution, which indicates that the microstructure of the graphene aerogel is not damaged by the solvent combustion of the present invention, the graphene micro layered structure is still maintained, and the graphene aerogel has a large specific surface area.
Test example 4
The test example is used to illustrate the microporous structure of the graphene aerogel according to the present invention.
The microstructure of graphene aerogel G1 was observed using a projection electron microscope, and the result is shown in fig. 6.
As can be seen from fig. 6, fig. 6A shows that there is only a small amount of aggregation and overlapping between sheets of the graphene aerogel G1, and fig. 6B shows that there are about 3-4 layers from the magnified photograph, which reflects the spatial network structure of the graphene hydrogel prepared by the hydrothermal method, and is well maintained after the graphene aerogel is dried by solvent combustion.
Test example 5
The results of observing graphene aerogel G1-4 obtained in examples 1-4 by a scanning electron microscope are shown in fig. 7.
As can be seen from fig. 7, the graphene aerogels of examples 1 to 4 all have a relatively uniform pore distribution, and have a relatively large pore structure between sheets, and the sheets are stacked to a relatively small extent, which results in a relatively large specific surface area and a relatively large specific capacity of the graphene aerogel.
Test example 6
The test example is used to illustrate the lattice structure of the graphene aerogel of the present invention.
XRD patterns of the graphene aerogels obtained in examples 1 to 3 and comparative example 1 were measured using an X-ray diffractometer, as shown in fig. 8.
Fig. 8 shows that the graphene aerogels G1-G3 obtained in examples 1-3 have an obvious characteristic peak of graphene at 25.26 °, and the characteristic peak is sharper than the characteristic peak of graphene of the graphene aerogel D1 obtained in comparative example 1, which indicates that the combustion drying process of the present invention does not destroy the lattice structure of the graphene aerogel, and further improves the crystallinity of the graphene aerogel, so that the lattice is more complete.
As can be seen from the comparison between example 1 and comparative examples 1-2, the atmospheric drying in comparative example 1 requires the continuous treatment of the sample in the oven for more than 3 hours, and the pore diameter of the graphene aerogel obtained by the method is collapsed, the surface area is very small, and the surface area is only 6.78m2(ii)/g; the freeze-drying in the comparative example 2 requires the vacuum freeze-drying of the sample in a freeze dryer for 12-24 hours at the temperature of below-50 ℃ and below 12Pa, and the method requires large-scale equipment and has a long period; the method in embodiment 1 only needs to directly ignite the organic solvent in the graphene gel, so that the obtained aerogel has a large specific surface area, does not need special equipment, is simple in process, short in preparation period and extremely low in cost, greatly improves the production efficiency, and is very beneficial to industrial batch production of the graphene aerogel.
According to the test results, the graphene aerogel prepared by the method has a large specific surface area. In particular, the amount of the solvent to be used,as can be seen from comparison between example 1 and comparative example 1, as shown in fig. 1, the graphene aerogel obtained by the combustion method in example 1 has a large macroscopic volume, while the graphene aerogel obtained by the room-temperature drying method in comparative example 1 has a small macroscopic volume. As can be seen from the results in Table 1, the specific surface area of the graphene aerogel obtained by the method of the invention can reach 731.7m2The specific surface area of the graphene aerogel obtained by the freeze drying method is only 261.59m2/g。
As can be further seen from fig. 3, the graphene aerogel obtained by the embodiment 1 of the present invention has uniform pore size distribution, and the size is about 6.88 nm; as can be seen from fig. 4, the pore size of the graphene aerogel obtained by the freeze-drying method in comparative example 2 is only 3.34 nm.
The results show that the graphene aerogel prepared by the invention has higher specific surface area and higher utilization value than the graphene obtained by traditional freeze drying and oven drying under normal pressure.
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 (20)
1. The preparation method of the graphene aerogel is characterized by comprising the steps of combusting a combustible solvent in graphene liquid-phase gel containing the combustible solvent to obtain the graphene aerogel;
the graphene liquid-phase gel containing the flammable solvent is prepared by a solvothermal method, or is prepared by replacing water in graphene hydrogel prepared by a hydrothermal method with the flammable solvent;
the graphene liquid-phase gel containing the combustible solvent contains a surfactant, wherein the surfactant is selected from one or more of lignosulfonate, dodecylbenzene sulfonate and dodecyl sulfate;
the content of the combustible solvent in the graphene liquid-phase gel containing the combustible solvent accounts for more than 60 wt% of all solvents.
2. The method according to claim 1, wherein the graphene liquid-phase gel containing the combustible solvent is a solvothermal graphene liquid-phase gel.
3. The method according to claim 2, wherein the flammable solvent is one or more selected from alcohols, ketones, ethers, aldehydes, or acids.
4. The method according to claim 3, wherein the alcohol is a lower aliphatic alcohol, the ketone is a lower aliphatic ketone, the ether is a lower aliphatic ether, the aldehyde is a lower aliphatic aldehyde, and the acid is a lower fatty acid.
5. The method according to claim 3, wherein the alcohols are methanol, ethanol, propanol, isopropanol, the ketones are acetone, butanone, the ethers are diethyl ether, the aldehydes are formaldehyde, acetaldehyde, propionaldehyde, and the acids are acetic acid.
6. The method of claim 1, wherein the manner of replacement comprises a soaking treatment and/or a rinsing treatment.
7. The method according to claim 6, wherein the temperature of the soaking treatment is 0 to 250 ℃ and the time is 10min or more.
8. The method according to claim 7, wherein the temperature of the soaking treatment is 80-180 ℃ and the time is 0.5-3 h.
9. The process of claim 1, wherein the hydrothermal process comprises: and carrying out heat treatment on the aqueous solution of the graphene oxide.
10. The method according to claim 9, wherein the concentration of graphene oxide in the aqueous solution of graphene oxide is 0.2-10 mg/mL.
11. The method according to claim 10, wherein the concentration of graphene oxide in the aqueous solution of graphene oxide is 1-5 mg/mL.
12. The method of claim 9, wherein the aqueous solution of graphene oxide has a pH of 2-11.
13. The method of claim 12, wherein the aqueous solution of graphene oxide has a pH of 2-6 or 8-11.
14. The method according to claim 9, wherein a surfactant is added to the aqueous solution of graphene oxide before the heat treatment.
15. The method of claim 14, wherein the surfactant is added in an amount of 0.5-3 parts by weight with respect to 1 part by weight of the graphene oxide.
16. The method of any one of claims 1-15, wherein the flammable solvent is caused to combust by means selected from one or more of open flame ignition, thermal radiation ignition, or electric arc ignition.
17. The method of any one of claims 1-15, wherein the graphene aerogel further comprises a graphene composite aerogel.
18. The method of claim 17, wherein the graphene composite aerogel is one or more of a reduced graphene oxide/oxide composite aerogel, a reduced graphene oxide/hydroxide composite aerogel, a reduced graphene oxide/nitride composite aerogel, a reduced graphene oxide/sulfide composite aerogel, a reduced graphene oxide/selenide composite aerogel, a reduced graphene oxide/cyanide composite aerogel, a reduced graphene oxide/fluoride composite aerogel, a reduced graphene oxide/chloride composite aerogel, a reduced graphene oxide/metal composite aerogel.
19. Graphene aerogel obtainable by the process according to any one of claims 1 to 18.
20. Use of the graphene aerogel according to claim 19 in electrode materials, hydrogen storage materials, catalyst materials, thermal insulation materials and adsorbent materials.
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