CN115010122B - Method for preparing high-oxidation graphene - Google Patents
Method for preparing high-oxidation graphene Download PDFInfo
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- CN115010122B CN115010122B CN202210693114.3A CN202210693114A CN115010122B CN 115010122 B CN115010122 B CN 115010122B CN 202210693114 A CN202210693114 A CN 202210693114A CN 115010122 B CN115010122 B CN 115010122B
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Abstract
The invention discloses a method for preparing high-oxidation graphene, and belongs to the field of graphene preparation. The device for preparing the high-oxidation graphene comprises an electrolytic anode, an electrolytic cathode, a reaction container, a direct current power supply and a cooling device; the electrolytic anode is composed of a metal net structure with multiple layers of gradually decreasing pore diameters, and the metal net structures are mutually fixed and electrically contacted. Through this institutional advancement, electrolysis positive pole top-down divide into multilayer mesh screen structure for the graphene oxide that peels off drops to the lower floor from the hole on upper strata, then carries out the oxidation on lower floor's positive pole, has solved prior art and has directly regard graphite as the positive pole, causes the graphene after peeling off to leave the positive pole, material oxidation is insufficient, the inhomogeneous problem of lamellar structure.
Description
Technical Field
The invention belongs to the field of graphene preparation, and particularly relates to a method for preparing high-oxidation graphene.
Background
Graphene has a perfect two-dimensional crystal structure, and its lattice is hexagonal surrounded by six carbon atoms, and has a thickness of one atomic layer. The carbon atoms are connected by sigma bonds, the combination mode is sp2 hybridization, and the sigma bonds endow the graphene with extremely excellent mechanical properties and structural rigidity. Graphene is 100 times harder than the best steel, even more so than diamond. In graphene, each carbon atom has an unbonded p electron, the p electrons can freely move in the crystal, and the movement speed is as high as 1/300 of the speed of light, so that good conductivity is provided for the graphene. Graphene is a new generation transparent conductive material, and in the visible light region, the transmittance of four layers of graphene is equivalent to that of a traditional ITO film, and in other wave bands, the transmittance of four layers of graphene is far higher than that of the ITO film.
The graphene oxide flake is a product of graphite powder subjected to chemical oxidation and stripping, and is used as an important derivative of a graphene-based material, and the graphene oxide flake still maintains special surface performance and lamellar structure although the oxidation process breaks the highly conjugated structure of graphene. The introduction of the oxygen-containing group not only ensures that the graphene oxide has chemical stability, but also provides a surface modification active position and a larger specific surface area for synthesizing the graphene base/graphene oxide base material. Graphene oxide is used as a precursor and a support carrier for synthesizing the graphene-based composite material, and is easy to functionalize and high in controllability. In the process of compounding with materials such as metal, metal oxide, high molecular polymer and the like, the adhesive material can be effectively dispersed with large specific surface area, and agglomeration is prevented.
Graphene oxide also shows excellent physical, chemical, optical and electrical properties, and as the basal plane and the edge of the graphene sheet framework have a structure in which various oxygen-containing functional groups coexist, the graphene oxide can modulate conductivity and band gap by regulating and controlling the types and the quantity of the oxygen-containing functional groups. Graphene oxide is a novel carbon material with excellent performance, and has higher specific surface area and rich surface functional groups. The graphene oxide composite material comprises a polymer composite material and an inorganic composite material, and has wide application fields, so that the surface modification of the graphene oxide becomes another research focus.
Currently, the technical routes for preparing graphene on a large scale mainly include a chemical oxidation-reduction method, a CVD method and a liquid phase stripping method. The chemical oxidation-reduction method can obtain high-yield few-layer graphene oxide, but in the preparation process, strong acid and strong oxidant are needed to be used for intercalation and stripping of graphite, so that serious environmental pollution is caused, and irreversible damage to a graphene structure is caused. The CVD method for preparing the graphene utilizes the pyrolysis of methane molecules at high temperature to catalyze and deposit on the surface of metal copper, so that the high-quality graphene is obtained. The number of layers of the graphene prepared by the liquid phase stripping method is relatively thick, and a large amount of organic solvents can be used.
The current electrochemical method for preparing graphene is a method for peeling graphene from a block or powder raw material by utilizing electrochemical reaction and performing ultrasonic dispersion to obtain graphene. The method generally adopts a constant voltage and constant current power supply, flexible graphite paper and a graphite rod are used as working electrodes, hydroxyl ions generated by electrolysis of water are used as strong nucleophiles under the action of an electric field, sp2 hybridized carbon atoms at the edge and the grain boundary of graphite are attacked, and two adjacent carbon atoms are hydroxylated. This causes interlaminar expansion and depolarization of the edge graphite, promotes intercalation of electrolyte ions and water molecules, and simultaneously electrolyzes water-generated gas, further promotes exfoliation of the graphite, forming graphene oxide. Such methods, without the use of strong oxidants, can regulate the oxidation and exfoliation levels of graphite by varying the applied voltage, current, electrolyte concentration. The method is environment-friendly and high in safety, and is expected to be a method for preparing graphene on a large scale. However, the graphene prepared by the conventional electrochemical method has the problems of low graphene oxidation degree, non-uniform lamellar thickness and the like.
It should be noted that the information disclosed in this background section is only for the purpose of increasing the understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.
Disclosure of Invention
The invention aims to solve the technical problems of low oxidation degree and non-uniform thickness of a slice layer of graphene oxide prepared by the existing electrochemical method. Meanwhile, the high-oxidation graphene is prepared by adopting the device disclosed by the invention, so that the product performance and quality can be improved, and the collection and the taking of the graphene are facilitated.
The invention also provides a manufacturing method of high-oxidation graphene, which increases the oxidation time of a graphite material on the surface of an electrode through the design of a multi-layer net structure of the electrode device, and simultaneously increases a gas discharge channel, so that the steps of embedding and stripping graphite are more efficient and uniform, and the electrolyte does not generate uneven temperature gradient, thereby being more beneficial to the manufacturing of graphene by an electrochemical stripping method and having stable performance.
In order to achieve the above object, the present invention provides a manufacturing device of high graphene oxide, comprising an electrolytic anode, an electrolytic cathode, a reaction vessel, a direct current power supply and a cooling device; wherein the electrolytic anode is composed of N layers of metal net structures with gradually decreasing pore diameters, the metal net structures are mutually fixed and realize electric contact, and N is more than or equal to 2.
In one embodiment of the present invention, the electrolytic anode includes: the aperture of the top layer of the electrolytic anode is smaller than that of the reaction layer, and the aperture of the retention layer is smaller than that of the reaction layer.
In one embodiment of the present invention, the pore size of the top layer is 600 to 800 mesh, the pore size of the reaction layer is 400 to 600 mesh, and the pore size of the retention layer is less than 200 mesh.
In an embodiment of the present invention, the material of the electrolytic anode is titanium metal, platinum metal or an alloy material with inert metal on the surface; the retention layer is a metal plate with a micro-nano structure or a solid; the distance between the cathode and the anode electrode in the reaction container is 1-20cm.
The invention also provides a method for preparing high-oxidation graphene by adopting the equipment, which comprises the following steps:
(1) Placing an electrolytic anode and an electrolytic cathode in a reaction container filled with electrolyte, placing a graphite material in the center of the electrolytic anode, switching on a power supply, and switching on a cooling device to realize electrochemical stripping under a specific voltage;
(2) And after the reaction is finished, filtering the electrolyte, collecting primary graphene powder, and washing and drying the primary graphene powder to obtain a graphene powder product.
In an embodiment of the present invention, the graphite material is one or more of flake graphite, graphite paper, graphite plate, graphite powder, graphite foil, and expanded graphite.
In one embodiment of the present invention, the electrolyte is a sulfate solution selected from one or more of a perchlorate solution, a hydrogen peroxide solution, a persulfate, a phosphate solution, a nitrate, and a sulfate solution, and the concentration of the electrolyte is 0.1M to 5M.
In an embodiment of the invention, the electrolytic anode electrode material is a corrosion-resistant metal electrode, such as a titanium electrode, a platinum electrode, a gold electrode, an iridium tantalum electrode, an alloy electrode, and the like.
In one embodiment of the present invention, the specific electrochemical stripping voltage is 3 to 30V; the drying mode is one or more of freeze drying, vacuum drying and spray drying.
The invention also provides the high-oxidation graphene obtained by the method.
The invention also provides application of the high-oxidation graphene prepared by the method in transistors, solar cells, flexible sensors, biomedical engineering, nano medicine, tumor treatment, tissue engineering, drug release, biological imaging and biological molecule sensing.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the electrolytic anode of the electrochemical process device is designed into a multi-layer mesh structure, through the structural improvement, the electrolytic anode is divided into a multi-layer mesh structure from top to bottom, so that peeled graphene oxide falls into a lower layer from holes in an upper layer, and then oxidation is continuously carried out on the lower layer anode, thereby solving the problems of insufficient material oxidation and uneven layered structure caused by that the peeled graphene is separated from the anode directly taking graphite as the anode in the prior art;
2. the electrolytic anode designed by the invention has the advantages that the pore structure of the electrode structure is increased, the gas discharge channel is increased, the problems of low oxidation state and uneven lamellar caused by falling of graphite powder due to gas escape are reduced, meanwhile, the abundant pore diameter is requested to realize rapid heat dissipation in the electrode, the electrolyte is prevented from generating uneven temperature gradient, and the stable performance of graphene produced by the electrochemical stripping method is facilitated;
3. the method has the advantages of simple device, environment-friendly process, stable quality, uniform surface, good dispersibility and high yield of the obtained graphene, and is convenient for industrial production.
Drawings
FIG. 1 is a schematic diagram of an electrochemical preparation apparatus according to the present invention;
FIG. 2 is a schematic view of the structure of an electrolytic anode of the present invention;
FIG. 3 is a photograph showing the preparation of an aqueous dispersion of high graphene oxide according to example 2 of the present invention;
fig. 4 is a TEM image of the high graphene oxide prepared in example 2 of the present invention;
FIG. 5 is an AFM image of the high graphene oxide obtained in example 2 of the present invention;
fig. 6 is an SEM image of the high graphene oxide obtained in example 3 of the present invention;
fig. 7 is an SEM image of the high graphene oxide obtained in example 4 of the present invention;
FIG. 8 is an SEM image of the high graphene oxide obtained in example 5 of the present invention;
fig. 9 is an SEM image of the high graphene oxide obtained in example 6 of the present invention;
fig. 10 is an SEM image of high graphene oxide prepared according to the comparative example of the present invention.
The main reference numerals illustrate:
1 electrolytic anode, 2 electrolytic cathode, 3 reaction vessel, 4 DC power supply, 5 cooling device, 11 top layer, 12 reaction layer, 13 retention layer, 14 metal network structure.
Detailed Description
The invention will be described in further detail with reference to the drawings and the specific examples, but it should be understood that the scope of the invention is not limited by the specific embodiments. These embodiments are all preferred embodiments of the present invention, and the drawings are schematic for convenience of description, which merely illustrate the basic structure of the present invention, and the shown structure is not drawn to limit the same shape and size ratio as in actual implementation, which is an alternative design.
Throughout the specification and claims, unless explicitly stated otherwise, the term "comprise" or variations thereof such as "comprises" or "comprising", etc. will be understood to include the stated element or component without excluding other elements or components.
The invention aims to provide a device for preparing high-oxidation graphene. The method can prolong the oxidation time of graphene through the unique design of the positive electrode, and solves the problems of low oxidation degree, non-uniform thickness of the slice layer and the like of the graphene prepared by the existing electrochemical method. The preparation flow of the graphene is simplified, the product performance and quality are improved, and the graphene is conveniently collected and taken. The invention also provides a manufacturing method of the high-oxidation graphene, which increases the oxidation time of the graphite material on the surface of the electrode through the multi-layer net structure design of the electrode device, and simultaneously increases the gas discharge channel, so that the embedding and stripping steps of the graphite are more efficient and uniform, the electrolyte cannot generate uneven temperature gradient, and the manufacturing of the graphene by an electrochemical stripping method is more facilitated, and the performance of the graphene is stable.
In order to achieve the above object, the present invention provides a manufacturing device of high graphene oxide, as shown in fig. 1, the manufacturing device includes an electrolysis anode 1, an electrolysis cathode 2, a reaction vessel 3, a direct current power supply 4, and a cooling device 5; the electrolytic anode is composed of N layers of metal net structures with decreasing pore diameters, wherein the metal net structures are mutually fixed and realize electric contact, and N is more than or equal to 2. Preferably, 2.ltoreq.N.ltoreq.5; more preferably, n=3. Through such institutional advancement, electrolysis positive pole top-down divide into multilayer mesh screen structure for the graphene oxide that peels off drops to the lower floor from the hole on upper strata, then continues to peel off and oxidize on lower floor's positive pole, until the detention layer, has solved prior art and has directly regard graphite as the positive pole, causes the graphene after peeling off to leave the positive pole, material oxidation insufficient, the inhomogeneous problem of lamellar structure.
Fig. 2 shows a structure of an electrolytic anode according to an embodiment of the present invention, the electrolytic anode 1 comprises a top layer 11, a reaction layer 12, and a retention layer 13, wherein the pore size of the top layer 11 of the electrolytic anode is smaller than that of the reaction layer 12, and the pore size of the retention layer is smaller than that of the reaction layer 13.
In one embodiment of the invention, the electrolytic anode electrotop layer has a pore size of 600 to 800 mesh, the reaction layer has a pore size of 400-600 mesh, and the retention layer has a pore size of less than 200 mesh. Preferably, the pore diameter of the electrolytic anode electrotop layer is 700-800 meshes, the pore diameter of the reaction layer is 500-600 meshes, and the pore diameter of the retention layer is less than 200 meshes. More preferably, the electrolytic anode electrotop layer has a pore size of 800 mesh, the reaction layer has a pore size of 600 mesh, and the retention layer has a pore size of less than 200 mesh.
The pore structure arranged in this way has better layering effect on graphene stripping. Too small pore diameter and too large pore density can affect the stripping effect of the graphene material, and the integrity of electrochemical reaction cannot be ensured; too large pore diameter or too small pore density can lead to the peeled graphene to be difficult to drop to the lower layer, the layering effect is poor, and then the yield of the graphene is affected, so that the yield is too low.
Wherein the graphite material is one or more of flake graphite, graphite paper, graphite plate, graphite powder, graphite foil and expanded graphite; and/or the thickness of the graphite flake is 2-5 mm. The graphite material has a size greater than the size of the top layer pore size.
The graphene oxide fragments are generated after the delamination and stripping steps of the graphite material in the electrolyte, and fall to the reaction layer through the reaction layer screen mesh, then further stripped in the reaction layer and then fall to the retention layer. Because the top layer, the reaction layer and the retention layer are electrically connected, the graphene material can be separated from the graphite material and then oxidized.
In one embodiment of the present invention, the electrolyte is one or more selected from perchlorate solution, hydrogen peroxide solution, persulfate, phosphate solution, nitrate, sulfate solution, and the concentration of sulfate is 0.1M to 5M. Preferably, the electrolyte is a sulfate solution and/or a sodium persulfate solution, and the concentration of the solution is 0.1M-3M. More preferably, the electrolyte is a sulfate solution and/or a sodium persulfate solution, and the concentration of the solution is 0.1M-1M.
In one embodiment of the invention, the electrode materials of the electrolytic anode and the cathode are corrosion-resistant metal electrodes, such as titanium electrodes, platinum electrodes, gold electrodes, iridium tantalum electrodes, iridium plated titanium electrodes, alloy-based electrodes, and the like.
In one embodiment of the invention, the distance between the electrolytic anode and the cathode is 1-20cm. Preferably, the distance between the electrolytic anode and the cathode is 1-10cm. More preferably, the distance between the electrolytic anode and the cathode is 1-5cm.
In one embodiment of the invention, the specific electrochemical voltage is 3-30V. Preferably, the specific electrochemical voltage is 3-20V. More preferably, the specific electrochemical voltage is 3-10V.
Alternatively, the specific electrochemical voltage of the present invention may be changed in a gradient, for example, the whole reaction process is divided into more than two stages, wherein a voltage of 3-10V is applied in the first stage, a voltage greater than that in the first stage, for example, a voltage of 6-15V is applied in the second stage, and then a third voltage or a positive voltage of a pulse waveform may be applied to perform the peeling step, so that a better peeling effect is obtained.
The cooling step in the invention can be carried out by adopting a circulating water cooling mode, and the cooling temperature is between-10 ℃ and 10 ℃. Preferably, the cooling temperature is from-5 ℃ to 5 ℃. More preferably, the cooling temperature is from-5 ℃ to 0 ℃. Cooling the electrolyte can prevent side reactions, such as ammonia, sulfur dioxide, nitrogen dioxide, etc., that occur when the electrolyte temperature is too high when the electrolysis current is large. On the other hand, a local heat release phenomenon can occur in the anodic electrolysis, and if the system does not timely dissipate heat, the prepared graphene can be partially reduced.
And after the reaction is finished, filtering the electrolyte, collecting primary graphene powder, and washing and drying the primary graphene powder to obtain a graphene powder product.
In a specific embodiment of the present invention, the drying mode is one or more of freeze drying, vacuum drying and spray drying.
Embodiment one:
the preparation device for preparing high-oxidation graphene, shown in fig. 1 and 2, comprises an electrolysis anode 1, an electrolysis cathode 2, a reaction vessel 3, a direct current power supply 4 and a cooling device 5; wherein, the electrolytic anode 1 comprises a top layer 11, a reaction layer 12 and a retention layer 13, the aperture of the top layer 11 of the electrolytic anode is smaller than that of the reaction layer 12, and the aperture of the retention layer is smaller than that of the reaction layer 12.
Embodiment two:
the apparatus of example one was used to prepare high graphene oxide. Wherein the top layer of the electrolytic anode is a titanium mesh with the mesh number of 800 and the area of 5cm x 5 cm; titanium mesh with the mesh number of the reaction layer being 400 and the area being 5cm x 5 cm; the retention layer is a titanium sheet with an area of 5cm by 5cm. The cathode adopts a flaky electrode with the same area.
The method comprises the following steps:
(1) Graphite paper with the thickness of 0.5mm and 3cm is placed in the center of the reaction layer 12, and three layers of the top layer 11, the reaction layer 12 and the retention layer 13 are sequentially clamped through threads to realize electric contact. The vertical distance between the electrodes of the electrolytic cathode 2 and the electrolytic anode 1 is set to be 2cm, the electrodes are placed in a reaction container 3, 1M ammonium sulfate electrolyte is slowly injected into the reaction container, two electrodes are not used, a direct current power supply 4 is connected, a cooling device 5 is opened to cool the electrolyte to-5 ℃, and electrochemical stripping of graphene is realized under 10V voltage.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
Description of product properties obtained in this example:
an aqueous dispersion of high graphene oxide prepared according to this example is shown in fig. 3, and the dispersion is brown-yellow. The morphology of the obtained high graphene oxide product observed under a Transmission Electron Microscope (TEM) is shown in FIG. 4; the morphology of the product observed under an Atomic Force Microscope (AFM) is shown in fig. 5. It can be seen from the figure that the graphene oxide film is mainly composed of single-layer graphene oxide, wherein 1-2 layers account for 40% and 1-3 layers account for 70% through statistics. And determining the carbon-oxygen ratio of the graphene powder to be 3.1 by using an X-ray photon energy spectrum.
Embodiment III:
the apparatus of example one was used to prepare high graphene oxide. Wherein the top layer of the electrolytic anode is a titanium mesh with the mesh number of 800 and the area of 4cm x 5 cm; titanium mesh with the mesh number of 600 and the area of 4cm x 5cm is arranged on the reaction layer; the retention layer is a nano titanium sheet with the area of 4cm x 5cm. The cathode adopts titanium sheet electrodes with the same area.
The method comprises the following steps:
(1) And a proper amount of flake graphite powder is paved in the center of the reaction layer 12, and three layers of the top layer 11, the reaction layer 12 and the retention layer 13 are sequentially clamped through threads, so that electric contact is realized. The upper and lower spacing between the electrodes of the electrolytic cathode 2 and the electrolytic anode 1 is set to be 3cm, the electrolytic cathode and the electrode of the electrolytic anode 1 are placed in a reaction container 3, 0.1M ammonium sulfate electrolyte is slowly injected into the reaction container to permeate the two electrodes, a direct current power supply 4 is connected, a cooling device 5 is opened to cool the electrolyte to-3 ℃, and electrochemical stripping of graphene is realized under 20V voltage.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
Description of product properties obtained in this example:
the morphology observed under the high graphene oxide aqueous dispersion and the low-power transmission electron microscope obtained according to this example was similar to that of example 2. The morphology of the product observed under a Scanning Electron Microscope (SEM) for the obtained high graphene oxide product is shown in fig. 6. The statistics show that the 1-2 layers account for 20% and the 1-3 layers account for 50%. And determining the carbon-oxygen ratio of the graphene powder to be 4.5 by using an X-ray photon energy spectrum.
Embodiment four:
the apparatus of example one was used to prepare high graphene oxide. Wherein the top layer of the electrolytic anode is a titanium mesh with the mesh number of 600 and the area of 4cm x 4 cm; the reaction layer is a titanium net with the mesh number of 200 and the area of 4cm x 4 cm; the retention layer is a titanium sheet with an area of 4cm x 4 cm. The cathode adopts titanium sheet electrodes with the same area.
The method comprises the following steps:
(1) A graphite plate with the thickness of 0.3cm and 2cm x 2cm is placed in the center of the reaction layer 12, and three layers of the top layer 11, the reaction layer 12 and the retention layer 13 are sequentially clamped through threads to realize electric contact. The upper and lower spacing between the electrodes of the electrolytic cathode 2 and the electrolytic anode 1 is set to be 6cm, the electrolytic cathode and the electrode of the electrolytic anode 1 are placed in a reaction container 3, 5M sodium sulfate and 20% hydrogen peroxide electrolyte are slowly injected into the reaction container, the two electrodes are not used, a direct-current power supply 4 is connected, a cooling device 5 is turned on to cool the electrolyte to-5 ℃, and electrochemical stripping of graphene is realized under the voltage of 6V.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
Description of product properties obtained in this example:
the morphology observed under the low-power transmission electron microscope of the graphene oxide-graphene oxide aqueous dispersion liquid obtained according to the present example was similar to that of example 2. The morphology of the product observed under a Scanning Electron Microscope (SEM) of the obtained high graphene oxide product is shown in fig. 7. The statistics show that the 1-2 layers account for 30% and the 1-3 layers account for 45%. And determining the carbon-oxygen ratio of the graphene powder to be 4.6 by using an X-ray photon energy spectrum.
Fifth embodiment:
the apparatus of example one was used to prepare high graphene oxide. Wherein the top layer of the electrolytic anode is an iridium-titanium plated net with the mesh number of 800 and the area of 5cm x 4 cm; the reaction layer is a platinum net with the mesh number of 600 and the area of 5cm x 4 cm; the retention layer was a platinum sheet with an area of 5cm x 4 cm. The cathode adopts a platinum sheet electrode with the same area.
The method comprises the following steps:
(1) And a proper amount of expanded graphite powder is paved in the center of the reaction layer 12, and three layers of the top layer 11, the reaction layer 12 and the retention layer 13 are sequentially clamped through threads to realize electric contact. The upper and lower spacing between the electrodes of the electrolytic cathode 2 and the electrolytic anode 1 is set to be 2cm, the electrolytic cathode and the electrode of the electrolytic anode 1 are placed in a reaction container 3, a mixed solution of 1M sodium sulfate and 1M phosphoric acid is slowly injected into the reaction container to pass through the two electrodes, a direct-current power supply 4 is connected, a cooling device 5 is turned on to cool the electrolyte to-4 ℃, and electrochemical stripping of graphene is realized under 16V voltage.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
Description of product properties obtained in this example:
the morphology observed under the low-power transmission electron microscope of the graphene oxide-graphene oxide aqueous dispersion liquid obtained according to the present example was similar to that of example 2. The morphology of the product observed under a Scanning Electron Microscope (SEM) of the obtained high graphene oxide product is shown in fig. 9. The statistics show that the 1-2 layers account for 25% and the 1-3 layers account for 33%. And determining the carbon-oxygen ratio of the graphene powder to be 5.2 by using an X-ray photon energy spectrum.
Example six:
the apparatus of example one was used to prepare high graphene oxide. Wherein the top layer of the electrolytic anode is an iridium-titanium plated net with the mesh number of 600 and the area of 3cm x 4 cm; the reaction layer is a platinum net with the mesh number of 400 and the area of 3cm x 4 cm; the retention layer is a nano titanium sheet with the area of 3cm x 4 cm. The cathode adopts a platinum sheet electrode with the same area.
The method comprises the following steps:
(1) A graphite plate with the thickness of 0.2cm and 1cm x 2cm is placed in the center of the reaction layer 12, and three layers of the top layer 11, the reaction layer 12 and the retention layer 13 are sequentially clamped through threads to realize electric contact. The upper and lower spaces between the electrodes of the electrolysis cathode and the electrolysis anode are set to be 10cm, the electrodes are placed in a reaction container 3, 1M sodium perchlorate solution is slowly injected into the reaction container, the two electrodes are not used, a direct current power supply 4 is connected, a cooling device 5 is opened to cool electrolyte to 0 ℃, and electrochemical stripping of graphene is realized under 10V voltage.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
Description of product properties obtained in this example:
the morphology observed under the low-power transmission electron microscope of the graphene oxide-graphene oxide aqueous dispersion liquid obtained according to the present example was similar to that of example 2. The morphology of the product observed under a Scanning Electron Microscope (SEM) of the obtained high graphene oxide product is shown in fig. 9. The statistics show that the 1-2 layers account for 26% and the 1-3 layers account for 50%. And determining the carbon-oxygen ratio of the graphene powder to be 4.9 by using an X-ray photon energy spectrum.
Comparative example
The apparatus of example one was used to prepare high graphene oxide using a direct electrolysis process. Wherein, the electrolytic anode directly carries out electrolysis by graphite paper, and the cathode adopts a platinum sheet electrode with the same area as that of the sixth embodiment.
The method comprises the following steps:
(1) The upper and lower spacing between the electrodes of the electrolytic cathode and the electrolytic anode is set to be 2cm, the electrodes are placed in a reaction container 3, 1M sodium perchlorate solution is slowly injected into the reaction container to pass through the two electrodes, a direct current power supply 4 is connected, a circulating device 5 is opened to cool electrolyte to 0 ℃, and electrochemical stripping of graphene is realized under 10V voltage.
(2) And after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, and washing and freeze-drying for multiple times to obtain a graphene powder product.
The morphology of the product observed under a Scanning Electron Microscope (SEM) of the obtained graphene product is shown in fig. 10.
Table 1 list of graphene performance parameters prepared for each example and comparative example
Compared with the comparative example, the high-oxidation graphene obtained by the method has good water dispersibility and can be directly used for preparing the composite material. Meanwhile, the comparison of AFM and SEM pictures can show that the graphene sheet prepared by the method has good extensibility; the sheet is thin. And after repeated ultrasonic treatment, graphene prepared by the traditional electrochemical method has small sheet diameter, thick sheet layer and poor dispersion effect.
The high-purity graphene prepared by the method can reach more than 100 microns in size, the number of layers can be controlled below 2, and the high-purity graphene has the advantages of large specific surface area and good conductivity when being used as a composite material additive.
The foregoing descriptions of specific exemplary embodiments of the present invention are presented for purposes of illustration and description. It is not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application to thereby enable one skilled in the art to make and utilize the invention in various exemplary embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.
Claims (4)
1. A method for preparing high-oxidation graphene, which is characterized by comprising the following steps: the device comprises an electrolytic anode (1), an electrolytic cathode (2), a reaction container (3), a direct current power supply (4) and a cooling device (5); the electrolytic anode (1) comprises: a top layer (11), a reaction layer (12) and a retention layer (13), wherein the aperture of the top layer (11) of the electrolytic anode is smaller than that of the reaction layer (12), and the aperture of the retention layer is smaller than that of the reaction layer (12); the material of the electrolytic anode (1) is titanium metal, platinum metal or alloy material with inert metal on the surface; the retention layer (13) is a metal plate with a micro-nano structure or a solid; the distance between the cathode and the anode electrode in the reaction container (3) is 1cm to 20cm; the method comprises the following steps:
placing an electrolytic anode (1) and an electrolytic cathode (2) in a reaction container (3) filled with electrolyte, placing a graphite material in the center of the electrolytic anode (1), switching on a power supply (4), and switching on a cooling device (5) to realize electrochemical stripping under the voltage of 3-30V;
(2) And after the reaction is finished, filtering the electrolyte, collecting graphene primary powder, and washing and drying the graphene primary powder to obtain a graphene powder product.
2. The method of preparing high graphene oxide according to claim 1, wherein the graphite material is one or more of graphite paper, graphite sheet, graphite powder, graphite foil.
3. The method for preparing high-oxidation graphene according to claim 1, wherein the electrolyte is one or more selected from perchlorate solution, hydrogen peroxide solution, persulfate, phosphate solution, nitrate solution and sulfate, and the concentration of the electrolyte is 0.1M to 5M.
4. The method for preparing high-oxidation graphene according to claim 1, wherein the drying mode is one or more of freeze drying, vacuum drying and spray drying.
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