CN115010122A

CN115010122A - Preparation device, preparation method and application of high-oxidation graphene

Info

Publication number: CN115010122A
Application number: CN202210693114.3A
Authority: CN
Inventors: 陈文苗; 陈杰; 李梦雨; 裴晓东
Original assignee: Sinosteel Nanjing New Material Research Institute Co Ltd
Current assignee: Sinosteel Nanjing New Material Research Institute Co Ltd
Priority date: 2022-06-17
Filing date: 2022-06-17
Publication date: 2022-09-06
Anticipated expiration: 2042-06-17
Also published as: CN115010122B

Abstract

The invention discloses a device and a method for preparing high-oxidation graphene, and belongs to the field of graphene preparation. The device comprises an electrolytic anode, an electrolytic cathode, a reaction container, a direct current power supply and a cooling device; wherein the electrolytic anode is composed of a plurality of layers of metal net structures with decreasing pore diameters, and the metal net structures are mutually fixed and realize electric contact. Through the structural improvement, the electrolytic anode is divided into a multi-layer mesh screen structure from top to bottom, so that the stripped graphene oxide drops to the lower layer from the holes in the upper layer, then the graphene oxide is continuously oxidized on the anode in the lower layer, and the problems that in the prior art, graphite is directly used as the anode, the stripped graphene leaves the anode, the material is not sufficiently oxidized, and the layered structure is not uniform are solved.

Description

Preparation device, preparation method and application of high-oxidation graphene

Technical Field

The invention belongs to the field of graphene preparation, and particularly relates to a preparation device, a preparation method and application of high-oxidation graphene.

Background

Graphene has a perfect two-dimensional crystal structure, the crystal lattice of which is a hexagon surrounded by six carbon atoms, and the thickness of the crystal lattice is one atomic layer. The carbon atoms are connected by sigma bonds in an sp2 hybridization mode, and the sigma bonds endow the graphene with extremely excellent mechanical properties and structural rigidity. Graphene is 100 times harder than the best steels, and even more so than diamond. In graphene, each carbon atom has an unbound p electron, and the p electrons can move freely in the crystal and move at 1/300 with the speed as high as the speed of light, so that the graphene is endowed with good conductivity. Graphene is a new-generation transparent conductive material, the transmittance of four-layer graphene is equivalent to that of the traditional ITO thin film in a visible light region, and the transmittance of four-layer graphene is far higher than that of the ITO thin film in other wave bands.

The graphene oxide sheet is a product obtained by chemically oxidizing and stripping graphite powder, is an important derivative of a graphene-based material, and maintains special surface performance and a layered structure although a highly conjugated structure of graphene is damaged in an oxidation process. The introduction of the oxygen-containing group not only enables the graphene oxide to have chemical stability, but also provides a surface modification active site and a larger specific surface area for synthesizing the graphene-based/graphene oxide-based material. The 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 metal, metal oxide, high molecular polymer and other materials, the material can be dispersed and attached effectively in large specific surface area to prevent agglomeration.

The graphene oxide also shows excellent physical, chemical, optical and electrical properties, and due to the coexistence structure of various oxygen-containing functional groups on the basal plane and the edge of the graphene sheet layer framework, the conductivity and the band gap of the graphene oxide can be adjusted by regulating the type and the number of the contained oxygen-containing functional groups. Graphene oxide is a novel carbon material with excellent performance, and has a high specific surface area and rich functional groups on the surface. The graphene oxide composite materials including polymer composite materials and inorganic composite materials have a wide application field, so that the surface modification of graphene oxide becomes another important research point.

At present, 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 adopted to carry out intercalation and stripping on graphite, so that not only is serious environmental pollution caused, but also irreversible damage to the graphene structure is caused. The CVD method for preparing the graphene is to utilize the cracking of methane molecules at high temperature to perform catalytic deposition on the surface of metal copper so as to obtain the high-quality graphene. The graphene prepared by the liquid phase stripping method has a relatively large number of layers, and a large amount of organic solvent is used.

The existing electrochemical method for preparing graphene is a method for stripping graphene from a block or powder raw material by using an electrochemical reaction and performing ultrasonic dispersion to obtain the graphene. In the method, a constant-voltage and constant-current power supply is adopted, flexible graphite paper and a graphite rod are used as working electrodes, and under the action of an electric field, hydroxide ions generated by electrolyzed water are used as a strong nucleophilic agent to attack sp2 hybridized carbon atoms at the edge of graphite and a crystal boundary so as to hydroxylate two adjacent carbon atoms. This causes interlayer expansion and depolarization of the edge graphite, promotes intercalation of electrolyte ions and water molecules, and further promotes exfoliation of graphite by electrolysis of gas generated by water, thereby forming graphene oxide. The method can regulate the oxidation and stripping degree of graphite by changing applied voltage, current and electrolyte concentration without using a strong oxidant. The method has the characteristics of environmental protection and high safety, and is expected to become 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, uneven lamella thickness and the like.

It is noted that the information disclosed in this background section is only for enhancement of 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 skilled in the art.

Disclosure of Invention

The invention aims to solve the technical problems of low oxidation degree and nonuniform lamella thickness of graphene oxide prepared by the conventional electrochemical method. Meanwhile, the device disclosed by the invention is adopted to prepare the high-oxidation graphene, so that the product performance and quality can be improved, and the graphene can be conveniently collected and used.

Another objective of the present invention is to provide a method for manufacturing highly oxidized graphene, which increases the oxidation time of the graphite material on the electrode surface through the multi-layer mesh structure design of the electrode device, and increases the gas discharge channel, so as to promote the embedding and stripping steps of graphite to have higher efficiency and uniformity, and to prevent the electrolyte from generating uneven temperature gradient, thereby facilitating the stable performance of the electrochemical stripping method for manufacturing and producing graphene.

In order to achieve the purpose, the invention provides a manufacturing device of high-oxidation graphene, which comprises an electrolytic anode, an electrolytic cathode, a reaction container, a direct-current power supply and a cooling device, wherein the electrolytic anode is connected with the electrolytic cathode; wherein, the electrolytic anode is composed of N layers of metal net structures with decreasing pore diameters, the metal net structures are mutually fixed and realize electric contact, wherein 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 an embodiment of the invention, the pore size of the top layer is 600-800 mesh, the pore size of the reaction layer is 400-600 mesh, and the pore size of the retention layer is less than 200 mesh.

In one embodiment of the present invention, the material of the electrolytic anode is titanium metal, platinum metal or an alloy material with an inert metal surface; the detention layer is a metal plate with a micro-nano structure or a solid structure; the distance between the cathode and the anode 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, turning on a cooling device, and realizing electrochemical stripping under specific voltage;

(2) and after the reaction is finished, filtering the electrolyte, collecting the graphene primary powder, and washing and drying the graphene primary 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 sheet, graphite powder, graphite foil, and expanded graphite.

In an embodiment of the present invention, the electrolyte is one or more sulfate solutions selected from 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 present invention, the material of the electrolytic anode electrode 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 peeling voltage is 3 to 30V; the drying mode is one or more of freeze drying, vacuum drying and spray drying.

The invention also provides high-oxidation graphene obtained by the method.

The invention also provides application of the high graphene oxide prepared by the method in transistors, solar cells, flexible sensors, biomedical engineering, nanomedicine, tumor treatment, tissue engineering, drug release, biological imaging and biomolecule 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 multilayer mesh structure, and is divided into a multilayer mesh structure from top to bottom through the structural improvement, so that the stripped graphene oxide falls to the lower layer from the holes of the upper layer, and then the oxidation is continuously carried out on the anode of the lower layer, thereby solving the problems that the stripped graphene leaves the anode due to the fact that the graphite is directly used as the anode in the prior art, the material oxidation is insufficient, and the layered structure is not uniform;

2. the electrolytic anode designed by the invention is additionally provided with the hole structure of the electrode structure, the gas discharge channel is increased, the problems of low oxidation state and uneven lamella caused by the falling of graphite powder due to gas escape are solved, meanwhile, the rich aperture is requested to realize rapid heat dissipation in the electrode, the electrolyte is prevented from generating uneven temperature gradient, and the performance stability of graphene production by an electrochemical stripping method is facilitated;

3. the device is simple, the process is green and environment-friendly, the obtained graphene is stable in quality, uniform in surface, good in dispersity and high in graphene yield, and industrial production is facilitated.

Drawings

FIG. 1 is a schematic view of the structure 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 picture of a high graphene oxide aqueous dispersion prepared in example 2 of the present invention;

FIG. 4 is a TEM image of highly oxidized graphene obtained in example 2 of the present invention;

FIG. 5 is an AFM picture of highly oxidized graphene obtained in example 2 of the present invention;

FIG. 6 is an SEM picture of highly oxidized graphene obtained in example 3 of the present invention;

FIG. 7 is an SEM picture of highly oxidized graphene obtained in example 4 of the present invention;

FIG. 8 is an SEM picture of highly oxidized graphene obtained in example 5 of the present invention;

FIG. 9 is an SEM picture of highly oxidized graphene obtained in example 6 of the present invention;

fig. 10 is an SEM picture of high graphene oxide prepared by the comparative example of the present invention.

Description of the main reference numerals:

1 electrolytic anode, 2 electrolytic cathode, 3 reaction vessel, 4 DC power supply, 5 cooling device, 11 top layer, 12 reaction layer, 13 detention layer, 14 metal net structure.

Detailed Description

The present invention is described in further detail below with reference to the attached drawings and specific examples, but it should be understood that the scope of the present invention is not limited by the specific embodiments. These embodiments are preferred embodiments of the present invention, and the drawings are schematic diagrams for convenience of description, which illustrate the basic structure of the present invention only in a schematic manner, and are not drawn to be limited to the same shapes and size ratios as those of actual implementation, which are an alternative design.

Throughout the specification and claims, unless explicitly stated otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element or component but not the exclusion of any other element or component.

The invention aims to provide a device for preparing high-oxidation graphene. The graphene oxidation time can be prolonged through the unique design of the positive electrode, and the problems of low oxidation degree, uneven lamella thickness and the like of the graphene prepared by the existing electrochemical method are solved. Simplify graphite alkene preparation flow, promote product property ability and quality, facilitate the collection and the taking of graphite alkene. 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 and increases the gas discharge channel through the design of the multi-layer net structure of the electrode device, so that the embedding and stripping steps of the graphite have higher efficiency and uniformity, the electrolyte does not generate uneven temperature gradient, and the performance of the graphene manufactured by the electrochemical stripping method is more stable.

In order to achieve the above object, the present invention provides a manufacturing apparatus of high graphene oxide, as shown in fig. 1, the manufacturing apparatus includes an electrolysis anode 1, an electrolysis cathode 2, a reaction vessel 3, a dc power supply 4, and a cooling device 5; the electrolytic anode is composed of N layers of metal net structures with decreasing pore diameters, 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 the structural improvement, the electrolytic anode is divided into a multi-layer mesh screen structure from top to bottom, so that the stripped graphene oxide falls to the lower layer from the holes in the upper layer, then the stripping and oxidation are continuously carried out on the anode in the lower layer until a retention layer, and the problems that in the prior art, the graphite is directly used as the anode, the stripped graphene leaves the anode, the material oxidation is insufficient, and the layered structure is not uniform are solved.

Fig. 2 shows a structure diagram of an electrolytic anode according to an embodiment of the invention, wherein the electrolytic anode 1 comprises a top layer 11, a reaction layer 12 and a retention layer 13, the pore diameter of the top layer 11 of the electrolytic anode is smaller than that of the reaction layer 12, and the pore diameter of the retention layer is smaller than that of the reaction layer 13.

In an embodiment of the invention, the aperture of the electrolytic anode electro-top layer is 600-800 meshes, the aperture of the reaction layer is 400-600 meshes, and the aperture of the retention layer is less than 200 meshes. Preferably, the aperture of the electrolytic anode electric top layer is 700-800 meshes, the aperture of the reaction layer is 500-600 meshes, and the aperture of the retention layer is less than 200 meshes. More preferably, the aperture of the electrolytic anode electro-top layer is 800 meshes, the aperture of the reaction layer is 600 meshes, and the aperture of the retention layer is less than 200 meshes.

The pore structure arranged in this way has a better layering effect for graphene stripping. The too small pore diameter and the too large opening density can affect the stripping effect of the graphene material and cannot ensure the integrity of the electrochemical reaction; too big or the trompil density undersize in aperture can lead to the graphite alkene of peeling off to be difficult to drop to the lower floor, and the layering effect is not good, and then influences the productivity of graphite alkene, leads to the productivity to hang down excessively.

Wherein the graphite material is one or more of crystalline flake graphite, graphite paper, graphite plate, graphite powder, graphite foil and expanded graphite; and/or the thickness of the graphite sheet is 2-5 mm. The graphite material has a size greater than the pore size of the top layer.

The graphite material generates graphene oxide fragments after a layer stripping step in electrolyte, the graphene fragments fall to a reaction layer through a reaction layer screen, and then are further stripped in the reaction layer, and then fall to a retention layer. Since 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 continuously oxidized.

In one embodiment of the present invention, the electrolyte is one or more selected from a perchlorate solution, a hydrogen peroxide solution, a persulfate, a phosphate solution, a nitrate, and a sulfate solution, and the sulfate has a concentration of 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 present invention, the electrode material of the electrolytic anode and the electrolytic cathode is a corrosion-resistant metal electrode, such as a titanium electrode, a platinum electrode, a gold electrode, an iridium-tantalum electrode, an iridium-plated titanium electrode, an alloy-based electrode, or the like.

In one embodiment of the invention, the distance between the electrolytic anode and cathode is from 1 to 20 cm.. Preferably, the distance between the electrolytic anode and the cathode is 1-10 cm.. More preferably, the distance between the electrolytic anode and the cathode is 1-5cm.

In one embodiment of the present invention, the specific electrochemical voltage is 3 to 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 varied in a gradient manner, for example, the whole reaction process is divided into two or more stages, a voltage of 3-10V is applied in the first stage, a voltage larger than that of 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 with a pulse waveform is applied to perform the stripping step, so as to obtain a better stripping effect.

The cooling step in the invention can be carried out by adopting a circulating water cooling mode, and the cooling temperature is-10 ℃ to 10 ℃. Preferably, the cooling temperature is from-5 ℃ to 5 ℃. More preferably, the cooling temperature is from-5 ℃ to 0 ℃. The cooling of the electrolyte can prevent side reactions, such as the generation of ammonia, sulfur dioxide, nitrogen dioxide, etc., which occur when the temperature of the electrolyte is too high when the electrolytic current is large. On the other hand, a local heat release phenomenon occurs in the anodic electrolysis, and if the system does not dissipate heat in time, the prepared graphene may be partially reduced.

And after the reaction is finished, filtering the electrolyte, collecting the graphene primary powder, washing and drying the graphene primary powder, and obtaining a graphene powder product.

In one embodiment of the present invention, the drying manner is one or more of freeze drying, vacuum drying and spray drying.

The first embodiment is as follows:

as shown in fig. 1 and 2, the apparatus for preparing high-oxidized graphene includes an electrolysis anode 1, an electrolysis cathode 2, a reaction vessel 3, a dc power supply 4, and a cooling apparatus 5; the electrolytic anode 1 comprises a top layer 11, a reaction layer 12 and a retention layer 13, wherein the pore diameter of the top layer 11 of the electrolytic anode is smaller than that of the reaction layer 12, and the pore diameter of the retention layer is smaller than that of the reaction layer 13.

Example two:

the preparation of high graphene oxide was performed using the apparatus of example one. 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; the mesh number of the reaction layer is 400, and the area of the reaction layer is 5cm by 5 cm; the retention layer is a titanium sheet with an area of 5cm x 5cm. The cathode adopts a sheet electrode with the same area.

The method comprises the following steps:

(1) graphite paper with the thickness of 0.5mm and 3cm by 3cm is placed in the center of the reaction layer 12, and the top layer 11, the reaction layer 12 and the retention layer 13 are clamped in sequence through threads to realize electric contact. Setting the distance between the electrodes of the electrolysis cathode 2 and the electrolysis anode 1 to be 2cm, placing the electrodes in a reaction container 3, slowly injecting 1M ammonium sulfate electrolyte into the electrodes to submerge the electrodes, switching on a direct current power supply 4, turning on a cooling device 5 to cool the electrolyte to-5 ℃, and realizing electrochemical stripping of graphene under the voltage of 10V.

(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.

Product characterization obtained in this example:

the aqueous dispersion of graphene oxide prepared according to this example is brown-yellow as shown in fig. 3. The product morphology observed under a Transmission Electron Microscope (TEM) on the obtained high graphene oxide product is shown in fig. 4; the morphology of the product observed under Atomic Force Microscopy (AFM) is shown in FIG. 5. As can be seen from the figure, the graphene oxide film is mainly composed of a single layer of graphene oxide, and statistics shows that 1-2 layers account for 40% and 1-3 layers account for 70%. And the carbon-oxygen ratio of the graphene powder is 3.1 by X-ray photon energy spectrum determination.

Example three:

the preparation of high graphene oxide was performed using the apparatus of example one. 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; the number of the reaction layers is 600, and the area of the reaction layers is 4cm by 5 cm; the retention layer is a nano titanium sheet with the area of 4cm by 5cm. The cathode adopts titanium plate electrodes with the same area.

The method comprises the following steps:

(1) proper amount of scale graphite powder is spread in the center of the reaction layer 12, and the top layer 11, the reaction layer 12 and the detention layer 13 are clamped tightly in sequence through threads to realize electric contact. And arranging electrodes of an electrolysis cathode 2 and an electrolysis anode 1 at an interval of 3cm from top to bottom, placing the electrodes in a reaction container 3, slowly injecting 0.1M ammonium sulfate electrolyte into the electrodes to submerge the electrodes, switching on a direct current power supply 4, turning on a cooling device 5 to cool the electrolyte to-3 ℃, and realizing electrochemical stripping of graphene under the voltage of 20V.

Product characterization obtained in this example:

the high graphene oxide aqueous dispersion obtained according to the embodiment and the morphology observed under a low-power transmission electron microscope are similar to those of the embodiment 2. The morphology of the obtained high graphene oxide product observed under a Scanning Electron Microscope (SEM) is shown in fig. 6. According to statistics, the proportion of 1-2 layers is 20%, and the proportion of 1-3 layers is 50%. And the carbon-oxygen ratio of the graphene powder is 4.5 by X-ray photon energy spectrum determination.

Example four:

the preparation of high graphene oxide was performed using the apparatus of example one. 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 by 4 cm; the retention layer is a titanium sheet with an area of 4cm x 4 cm. The cathode adopts a titanium sheet electrode with the same area.

The method comprises the following steps:

(1) a graphite plate with the thickness of 0.3cm and 2cm by 2cm is placed in the center of the reaction layer 12, and the top layer 11, the reaction layer 12 and the retention layer 13 are clamped in sequence through threads to realize electric contact. The electrodes of the electrolysis cathode 2 and the electrolysis anode 1 are arranged at an interval of 6cm from top to bottom and placed in a reaction container 3, 5M sodium sulfate and 20% hydrogen peroxide solution are slowly injected into the electrodes to immerse the electrodes, a direct current power supply 4 is switched on, a cooling device 5 is switched on to cool the solution to-5 ℃, and electrochemical stripping of graphene is achieved under the voltage of 6V.

Product characterization obtained in this example:

the graphene oxide and graphene oxide aqueous dispersion obtained according to the embodiment and the morphology observed under a low-power transmission electron microscope are similar to those of the embodiment 2. The morphology of the obtained high graphene oxide product observed under a Scanning Electron Microscope (SEM) is shown in fig. 7. According to statistics, the proportion of 1-2 layers accounts for 30%, and the proportion of 1-3 layers accounts for 45%. And the carbon-oxygen ratio of the graphene powder is 4.6 by X-ray photon energy spectrum determination.

Example five:

the preparation of high graphene oxide was performed using the apparatus of example one. 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 is 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 paving a proper amount of expanded graphite powder in the center of the reaction layer 12, and sequentially clamping the top layer 11, the reaction layer 12 and the detention layer 13 through threads to realize electric contact. The method comprises the steps of placing an electrode of an electrolytic cathode 2 and an electrode of an electrolytic anode 1 in a reaction container 3 at an upper-lower interval of 2cm, slowly injecting a mixed solution of 1M sodium sulfate and 1M phosphoric acid into the reaction container to submerge the two electrodes, switching on a direct current power supply 4, turning on a cooling device 5 to cool an electrolyte to-4 ℃, and realizing electrochemical stripping of graphene under the voltage of 16V.

Product characterization obtained in this example:

the graphene oxide and graphene oxide aqueous dispersion obtained according to the embodiment and the morphology observed under a low-power transmission electron microscope are similar to those of the embodiment 2. The morphology of the obtained high graphene oxide product observed under a Scanning Electron Microscope (SEM) is shown in fig. 9. The statistics show that 1-2 layers account for 25 percent and 1-3 layers account for 33 percent. And the carbon-oxygen ratio of the graphene powder is 5.2 by X-ray photon energy spectrum determination.

Example six:

the preparation of high graphene oxide was performed using the apparatus of example one. Wherein the top layer of the electrolytic anode is 600 meshes, and the area of the electrolytic anode is 3cm x 4cm and is plated with an iridium titanium net; the reaction layer is a platinum net with the mesh number of 400 and the area of 3cm by 4 cm; the detention layer is a nano titanium sheet with the area of 3cm by 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 the top layer 11, the reaction layer 12 and the retention layer 13 are clamped tightly in sequence through threads to realize electric contact. The method comprises the steps of arranging an electrolytic cathode and an electrolytic anode at an upper-lower interval of 10cm in a reaction container 3, slowly injecting 1M sodium perchlorate solution into the reaction container to submerge the two electrodes, switching on a direct current power supply 4, starting a cooling device 5 to cool electrolyte to 0 ℃, and realizing electrochemical stripping of graphene under the voltage of 10V.

Product characterization obtained in this example:

the morphology of the graphene oxide/graphene oxide aqueous dispersion obtained according to the embodiment and observed under a low-power transmission electron microscope is similar to that of the embodiment 2. The morphology of the obtained high graphene oxide product observed under a Scanning Electron Microscope (SEM) is shown in fig. 9. The statistics show that 1-2 layers account for 26% and 1-3 layers account for 50%. And the carbon-oxygen ratio of the graphene powder is 4.9 by X-ray photon energy spectrum determination.

Comparative example

The preparation of highly oxidized graphene was performed by direct electrolysis using the apparatus of example one. The anode of the electrolysis is graphite paper for direct electrolysis, and the cathode is a platinum sheet electrode with the same area as the sixth embodiment.

The method comprises the following steps:

(1) the method comprises the steps of arranging an electrolytic cathode and an electrolytic anode at an upper-lower interval of 2cm in a reaction container 3, slowly injecting 1M sodium perchlorate solution into the reaction container to submerge the two electrodes, switching on a direct current power supply 4, starting a circulating device 5 to cool electrolyte to 0 ℃, and realizing electrochemical stripping of graphene under the voltage of 10V.

The morphology of the obtained graphene product observed under a Scanning Electron Microscope (SEM) is shown in fig. 10.

Table 1 list of graphene performance parameters prepared in each example and comparative example

	1-2 layer ratio (%)	1-3 layer ratio (%)	Carbon to oxygen ratio
				Example one	--	--	--
Example two	40	70	3.1
				EXAMPLE III	20	50	4.5
Example four	30	45	4.6
				EXAMPLE five	25	33	5.2
EXAMPLE six	26	50	4.9
				Comparative example	10	20	7.8

Compared with a comparative example, the high-oxidation graphene obtained by the invention has good water dispersibility, and can be directly used for preparing a composite material. Meanwhile, the comparison of AFM and SEM pictures shows that the graphene sheet layer prepared by the method has good extensibility; the sheet is thin. 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 has the advantages that the size can reach more than 100 micrometers, the number of layers can be controlled to be less than 2, and when the graphene is used as a composite material additive, the graphene has the advantages of large specific surface area and good conductivity.

The foregoing descriptions of specific exemplary embodiments of the present invention have been 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 certain principles of the invention and its practical application to enable one skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and 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

1. The preparation device of the high-oxidation graphene is characterized by comprising 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 (2) is composed of N layers of metal net structures (14) with decreasing pore diameters, the metal net structures are mutually fixed and realize electric contact, wherein N is more than or equal to 2.

2. The apparatus for preparing high graphene oxide according to claim 1, wherein the electrolytic anode (1) comprises: the electrolytic anode comprises a top layer (11), a reaction layer (12) and a retention layer (13), wherein the pore diameter of the electrolytic anode top layer (11) is smaller than that of the reaction layer (12), and the pore diameter of the retention layer is smaller than that of the reaction layer (13).

3. The preparation device of high graphene oxide according to claim 2, wherein the pore size of the top layer (11) is 600-800 meshes, the pore size of the reaction layer (12) is 400-600 meshes, and the pore size of the retention layer (13) is less than 200 meshes.

4. The device for preparing high-oxidation graphene according to claim 2, wherein the material of the electrolysis anode (1) is titanium metal, platinum metal or an alloy material with an inert metal surface; the retention layer (13) is a metal plate with a micro-nano structure or a solid structure; the distance between the cathode and the anode in the reaction container (3) is 1-20cm.

5. A method for preparing high-oxidation graphene is characterized by comprising the following steps: which employs the device of any one of claims 1-5, comprising the steps of:

(1) 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), turning on a cooling device (5), and realizing electrochemical stripping under specific voltage;

(2) and after the reaction is finished, filtering the electrolyte, collecting the primary graphene powder, washing and drying the primary graphene powder, and obtaining a graphene powder product.

6. The method for preparing high graphene oxide according to claim 5, wherein the graphite material is one or more of flake graphite, graphite paper, graphite plate, graphite powder, graphite foil and expanded graphite.

7. The method for preparing graphene oxide according to claim 5, wherein the electrolyte is one or more selected from a perchlorate solution, a hydrogen peroxide solution, a persulfate, a phosphate solution, a nitrate solution and a sulfate, and the concentration of the electrolyte is 0.1-5M.

8. The method for preparing high graphene oxide according to claim 5, wherein the specific voltage is 3-30V; the drying mode is one or more of freeze drying, vacuum drying and spray drying.

9. A highly oxidized graphene prepared according to the method of claim 5.

10. Use of the highly oxidized graphene prepared according to the method of claim 5 in transistors, solar cells, flexible sensors, biomedical engineering, nanomedicine, tumor therapy, tissue engineering, drug delivery, bio-imaging, and bio-molecular sensing.