CN111422859A - Low-defect nitrogen-doped graphene and preparation method thereof - Google Patents
Low-defect nitrogen-doped graphene and preparation method thereof Download PDFInfo
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Abstract
The invention discloses low-defect nitrogen-doped graphene and a preparation method thereof, wherein nitrogen atoms in a graphene material are connected in a graphite layer by graphite type nitrogen and pyridine type nitrogen, and the doping amount atomic percentage is 1-10%. The preparation method comprises the following steps: (1) pre-nitriding a graphite raw material; (2) stripping by chemical oxidation; (3) and (4) pyrolysis reduction. The method directly mixes nitrogen atoms into the graphite layer by the pre-nitridation technology and then carries out stripping, which is completely different from the traditional stripping-first nitrogen-mixing technology. The method has the advantages that the graphene lamellar structure cannot be damaged by doping nitrogen atoms in the pre-nitridation way, the nitrogen-doped graphene prepared by the method has few defects and high quality, the type and the number of the nitrogen atoms are controllable, and the method is simple in synthesis process and easy to realize large-scale production and application.
Description
Technical Field
The invention relates to the technical field of carbon nano materials and preparation thereof, in particular to low-defect nitrogen-doped graphene and a pre-nitridation preparation method thereof.
Background
The graphene is represented by sp2The single-layer graphite flake formed by the hybridized carbon atom six-membered ring is a novel two-dimensional nanocrystal material and has the characteristics of ultrahigh specific surface area, excellent mechanical property, excellent electrical property, excellent optical property, excellent thermal property and excellent multifunctional property. Since its discovery in 2004, it has received extensive attention from academia and industry, and has shown important application value and development potential in the fields of electronics, communications, energy, environment, biology, medical treatment, etc. The relation between energy and momentum of the graphene crystal with the complete structure near the Fermi surface can be approximately linear, so that the current carrier of the graphene crystal can be continuously converted between electrons and holes, and the graphene has the property of a zero-band-gap semiconductor. Also because of this, the conductivity of graphene cannot be fully controlled and utilized like conventional semiconductors. In addition, the surface of the graphene crystal with the complete structure is in an inert state, the chemical property is very stable, the graphene crystal is difficult to interact with other materials or media, and the graphene crystal is difficult to disperse in common polar solvents such as water and the like due to strong van der waals force and non-polar property between graphite sheets, so that the application of the graphene is greatly limited.
People regulate and control and improve the structure and the performance of graphene by methods such as chemical modification, and chemical element doping is considered to be one of the methods which are very effective in improving the structure and the performance of graphene. The nitrogen atom is similar to the carbon atom in radius size and is easy to be combined into a carbon layer framework in a substituted structure, lone-pair electrons of the nitrogen can form a conjugated structure with a pi-bond system of graphene, and the charge concentration around the carbon atom and the carrier concentration of a graphene sheet layer are effectively improved, so that the performances of the carbon atom such as electrical conductivity, electrochemical activity, catalytic activity and the like are improved. In addition, the access of nitrogen atoms destroys carbon-carbon bonds with uniform structure, and the formed carbon-nitrogen bonds introduce stress into the carbon layers around the carbon-nitrogen bonds to deform and fold the carbon layers, so that a richer and ideal micro-nano structure is provided for realizing the functional application of graphene. Compared with graphene, the nitrogen-doped graphene has greatly improved structure and performance, and therefore has more important and wider application in the functional fields of energy, communication and the like.
There are three main ways of nitrogen atoms to be grafted into the graphene carbon layer, namely pyridine type nitrogen, pyrrole type nitrogen and graphite type nitrogen. The different types of nitrogen atom doping have different effects on changing the electrical properties and the structure of the graphene. Researches show that pyridine nitrogen, pyrrole nitrogen and graphite nitrogen have positive effects on the pseudocapacitance and catalytic activity of graphene, and the graphite nitrogen can obviously improve the conductivity of the graphene. However, pyridine nitrogen and pyrrole nitrogen can only be connected in six-membered rings and five-membered rings at the edge of a carbon layer or at the edge defect of a hole, so that a large number of hole defects are formed in a graphene layer due to the introduction of the two kinds of nitrogen, the structure of graphene is damaged, and the electrical property and the mechanical property of the material are seriously influenced. Therefore, the graphene material with low structural defects and a specific nitrogen-doped type is synthesized and is prepared in a large scale, and the method has important scientific value and application value.
At present, the most common and easy-to-operate method is to synthesize graphene oxide first, and then carry out nitrogen doping by subsequent methods such as high-temperature heating, solvothermal, nitrogen plasma discharge, microwave irradiation and the like. However, the nitrogen-doped graphene prepared by these subsequent methods is mainly based on pyridine-type nitrogen and pyrrole-type nitrogen. It has also been reported that carbon-and nitrogen-containing precursors are used as carbon and nitrogen sources to directly synthesize nitrogen-doped graphene by a chemical vapor deposition method or an arc discharge method. However, the methods involve the steps of graphene film separation, transfer and the like, and are low in nitrogen doping amount, harsh in reaction conditions, high in requirements on equipment and preparation cost, and difficult to realize large-scale production.
Therefore, the problem to be solved by those skilled in the art is how to provide a nitrogen-doped graphene material with low defect, high quality and simple preparation process, and a synthesis method thereof.
Disclosure of Invention
The invention aims to provide an effective preparation method of nitrogen-doped graphene aiming at the defects of the prior art, and simultaneously provide a low-defect and high-quality nitrogen-doped graphene material.
The preparation method of the nitrogen-doped graphene provided by the invention is completely different from the prior subsequent nitrogen doping method and the direct nitrogen doping method, and the nitrogen-doped graphene is prepared by directly doping nitrogen elements into a graphite carbon layer by adopting a pre-nitridation technology and carrying out processes such as stripping.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of low-defect nitrogen-doped graphene comprises the following steps:
(1) carrying out heat treatment on a graphite raw material in a nitrogen-containing active atmosphere to carry out pre-nitridation;
(2) stripping the pre-nitrided graphite through chemical oxidation to obtain nitrogen-doped graphene oxide;
(3) and (3) carrying out pyrolysis reduction on the nitrogen-doped graphene oxide obtained in the step (2) to obtain the low-defect nitrogen-doped graphene.
Preferably, in the above preparation method of low-defect nitrogen-doped graphene, the graphite raw material in step (1) is natural flaky graphite, cracked expanded graphite or other artificial graphite without any chemical modification.
The beneficial effects of the above technical scheme are: the graphite raw material which is not chemically modified can be used for avoiding side reactions possibly occurring in the high-temperature pre-nitridation process, so that the defects of introducing extra holes in the graphite layer and the like are avoided.
Preferably, in the preparation method of low-defect nitrogen-doped graphene, the nitrogen-containing active atmosphere in step (1) is any one of ammonia gas, a mixed gas of ammonia gas and argon gas, a mixed gas of ammonia gas and helium gas, a mixed gas of ammonia gas and nitrogen gas, and a mixed gas of ammonia gas and hydrogen gas, and further preferably is ammonia gas or a mixed gas of ammonia gas and argon gas.
Preferably, in the preparation method of the low-defect nitrogen-doped graphene, the temperature of the heat treatment in the step (1) is 500-.
The beneficial effects of the above technical scheme are: the nitrogen atom doping can be realized at the normal heating temperature and the lower speed gas flow, and the nitrogen atom doping amount can be adjusted by changing the heat treatment temperature and the heat treatment time, and the higher the heat treatment temperature is, the longer the heat treatment time is, the higher the content of the doped nitrogen atom is. The experimental result shows that the nitrogen atom content of the nitrogen-doped graphene prepared by performing heat treatment and pre-nitridation at 500 ℃ for 0.5h is about 1.0%; the nitrogen-doped graphene prepared by heat treatment at 1200 ℃ and pre-nitridation for 6 hours has the nitrogen atom content of about 10.0%.
Preferably, in the above method for preparing low-defect nitrogen-doped graphene, after the heat treatment in step (1), the graphene is naturally cooled to room temperature, and then one of argon, helium and hydrogen, or a mixed gas of two or more of the above gases is introduced to remove the adsorbed nitrogen atoms, wherein the gas introduction time is 0.5 to 1 hour.
The beneficial effects of the above technical scheme are: and introducing nitrogen-free inert or reducing gas after the temperature reduction of the pre-nitridation heat treatment to remove nitrogen atoms physically adsorbed on the surface of the graphite layer.
Preferably, in the above preparation method of low-defect nitrogen-doped graphene, the oxidizing agent used in the chemical oxidation stripping in step (2) is concentrated sulfuric acid and potassium permanganate.
Preferably, in the preparation method of low-defect nitrogen-doped graphene, the specific steps of chemically oxidizing and stripping to obtain nitrogen-doped graphene oxide in step (2) are as follows:
placing 20 parts by mass of concentrated sulfuric acid in a beaker, adding 1 part by mass of pre-nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, magnetically stirring for 30-60min, carrying out pre-oxidation intercalation, and increasing the graphite interlayer spacing;
slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the temperature of reactants between 10 and 20 ℃ in the process, continuously stirring until the potassium permanganate is dissolved after the addition is finished, removing an ice bath when the temperature of the reactants does not rise, replacing the ice bath and keeping stirring, heating the reactants to 35 ℃, preserving the temperature for 30 to 60 minutes, carrying out oxidation intercalation reaction, and further increasing the graphite interlayer spacing;
adding 40-60 parts by mass of deionized water, carrying out heat preservation for 15-30min at the temperature of 90-95 ℃ under magnetic stirring, and carrying out hydrolysis reaction to enable oxygen-containing groups to replace manganese groups on the surface of the graphite layer;
and continuously adding 3-10 parts by mass of hydrogen peroxide and 20-30 parts by mass of deionized water under magnetic stirring, stopping stirring after 3-10min, centrifuging the reaction solution at 10000rpm for 5-10min, then respectively cleaning the centrifuged product by using 3% by mass of HCl aqueous solution and deionized water for 3-5 times, and drying the product in an oven at 60-80 ℃ for 12-48h to obtain the nitrogen-doped graphene oxide.
Preferably, in the preparation method of the low-defect nitrogen-doped graphene, the pyrolysis reduction temperature in the step (3) is 500-.
Preferably, in the above preparation method of low-defect nitrogen-doped graphene, in the step (3), the pyrolysis reduction atmosphere is any one of argon, helium and hydrogen, or a mixed gas of two or more of the above gases, and the gas flow rate is 0.06-0.6L/min.
The beneficial effects of the above technical scheme are: the heat treatment in the temperature range and the reducing and inert atmosphere can ensure that the nitrogen-doped graphene oxide is effectively reduced, and the graphene structure cannot be damaged by short-time pyrolysis reduction.
The invention also discloses the low-defect nitrogen-doped graphene synthesized by the method, wherein nitrogen atoms in the nitrogen-doped graphene are respectively connected with the inner part and the edge of the graphite layer by graphite type nitrogen and pyridine type nitrogen.
Preferably, in the low-defect nitrogen-doped graphene, the content of nitrogen atoms in the nitrogen-doped graphene is 1-10%, the number of layers of the nitrogen-doped graphene is 1-10, and the size of a single layer is 50nm-50 μm.
According to the technical scheme, compared with the prior art, the low-defect nitrogen-doped graphene and the preparation method thereof disclosed by the invention have the following obvious technical advantages and effects:
(1) the method is adopted to dope the graphene with nitrogen, nitrogen atoms replace carbon atoms and enter a grid inside the graphite layer in advance, the nitrogen atoms are mainly connected into the grid of the carbon layer by graphite type nitrogen and connected into the edge of the carbon layer by pyridine type nitrogen, and the defects of holes and the like cannot be introduced into the graphite layer, so that the problems that the electrical property and the mechanical property of the material are seriously influenced due to a plurality of hole defects of the graphene caused by the conventional subsequent nitrogen doping method are solved, and the technical defects of membrane separation, transfer, harsh reaction conditions, high cost and the like in the conventional direct synthesis method are also avoided;
(2) the synthetic method for preparing the nitrogen-doped graphene through pre-nitridation provided by the invention has the advantages of simple and reliable process and large-scale production;
(3) the nitrogen-doped graphene material prepared by the invention has the advantages of few defects of holes in the sheet layer, complete sheet layer structure, high quality and high nitrogen content, the conductivity of graphene can be effectively improved by graphite type nitrogen, the reactivity of graphene can be improved by pyridine type nitrogen at the edge, and the nitrogen-doped graphene material has important application value in super capacitors, lithium ion batteries and sensors, especially micro-nano circuits, electronic devices and electrocatalysis.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Figure 1 is a diagram showing XRD spectra of graphite starting material, nitrogen-doped graphite and nitrogen-doped graphene of example 1;
fig. 2 is an SEM photograph of nitrogen-doped graphene prepared in example 1;
FIG. 3 is a TEM photograph of nitrogen-doped graphene prepared in example 1;
fig. 4 is an XPS total spectrum of the nitrogen-doped graphene prepared in example 1;
fig. 5 is an XPS spectrum of nitrogen-doped graphene N1s prepared in example 1;
fig. 6 is an EDS spectrum of nitrogen-doped graphene prepared in example 2.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The method has the advantages that the structure of the graphene sheet layer cannot be damaged by doping nitrogen atoms in the pre-nitridation process, the doping type and the number of the nitrogen atoms are controllable, the synthesis process is simple, the product purity is high, the quality is high, and the large-scale production is easy to realize.
Example 1
Placing natural flaky graphite (325 meshes) in a crucible, introducing argon into a vacuum tube furnace at the flow rate of 0.15L/min to remove air in the furnace tube, introducing ammonia gas at the flow rate of 0.1L/min, heating to 900 ℃ at the speed of 5 ℃/min to perform heat preservation and heat treatment for 5h to perform pre-nitridation, introducing argon for 0.5h after the reaction furnace naturally cools to room temperature to obtain nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) in a beaker, adding 1 part by mass of nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, performing magnetic stirring for 30min to perform pre-oxidation intercalation, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring to keep the temperature of reactants within 10-20 ℃ in the process, continuously stirring to dissolve the reactants after the addition is completed, removing the ice bath when the temperature of the reactants does not rise any more, changing the water bath and keeping stirring, heating the reactants to 35 ℃ to perform intercalation reaction, adding 45 parts by mass of deionized water, performing hydrolysis reaction at the temperature of 90 ℃ for 30min, performing hydrolysis reaction for 30min, placing the hydrolysis reaction for 30min, adding argon gas into a water bath, heating to obtain a product, adding hydrogen peroxide solution, drying at the hydrogen peroxide solution, adding the hydrogen chloride, performing centrifugal reaction for 5.5 min, heating to the hydrogen chloride, drying at the hydrogen chloride for 5min, and drying at the temperature of 1000 parts by mass of 50 min, and the temperature of the hydrogen chloride, and drying to obtain a product, and drying, and the product, and adding the.
As shown in fig. 1, the XRD spectrum showed that the interlayer spacing of the nitrogen-doped graphene prepared using example 1 was significantly increased; as shown in fig. 2, SEM structural characterization shows that the prepared nitrogen-doped graphene sheets are in a dispersed state, and the sheet size is 500nm-20 μm; as shown in fig. 3, TEM characterization shows that the nitrogen-doped graphene sheet has a complete structure, no obvious hole defects, and 1-10 carbon layers; as shown in fig. 4, the relative content of nitrogen atoms was 5.4% by XPS spectroscopy; as shown in fig. 5, the nitrogen atom has a pyridine type nitrogen structure and a graphite type nitrogen structure.
Example 2
Placing natural flaky graphite (8000 meshes) in a crucible, introducing argon into a vacuum tube furnace at the flow rate of 0.15L/min to remove air in the furnace tube, introducing the mixed gas of ammonia and argon (the volume fraction of the ammonia is 10%) at the flow rate of 0.1L/min, heating to 900 ℃ at the speed of 5 ℃/min, carrying out heat preservation and heat treatment for 5h to carry out pre-nitridation, naturally cooling the reaction furnace to room temperature, introducing argon for 0.5h to obtain nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) into a beaker, adding 1 part by mass of nitrided graphite in an ice water bath at the temperature of 1-5 ℃, carrying out magnetic stirring for 60min to carry out pre-oxidation intercalation, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the temperature of reactants within 10-20 ℃ in the process, adding magnetic stirring to dissolve the potassium permanganate, removing the ice bath when the temperature of the reactants does not rise, changing the water bath to keep stirring, heating the reactants to 35 ℃ for 60min, carrying out oxidation reaction, adding 60 parts by mass of 60min, stirring, placing the mixture of the hydrogen-doped graphene in a tube furnace at the temperature of 10% and 10min, carrying out centrifugal stirring, adding hydrogen-doped deionized water, carrying out the centrifugal stirring, carrying out the reaction for 30min, heating, adding 10min, adding 10% of 10min, carrying out the mixture of 10% of hydrogen-doped graphene, carrying out the centrifugal reaction, carrying out the centrifugal stirring, carrying out the reaction, adding 10min, carrying out the reaction, wherein the reaction of 10% of the reaction, the reaction of 10% of the reaction.
As shown in fig. 6, the EDS spectrum analysis shows that the relative content of nitrogen atoms in the nitrogen-doped graphene prepared in example 2 is 8.13%, the SEM characterization result shows that the size of the nitrogen-doped graphene sheet is 50nm to 2.0 μm, the TEM characterization shows that the structure of the nitrogen-doped graphene sheet is complete, the number of carbon layers is 1 to 10, and the XPS spectrum shows that the nitrogen atoms are pyridine nitrogen and graphite nitrogen structures.
Example 3
Placing natural flaky graphite (325 meshes) in a crucible, introducing argon into a vacuum tube furnace at the flow rate of 0.15L/min to remove air in the furnace tube, introducing ammonia gas at the flow rate of 0.1L/min, heating to 500 ℃ at the speed of 5 ℃/min, performing heat preservation and heat treatment for 0.5h to perform pre-nitridation, introducing argon for 0.5h after the reaction furnace naturally cools to room temperature, obtaining nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) in a beaker, adding 1 part by mass of nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, performing pre-oxidation intercalation by magnetic stirring for 30min, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the reactant temperature within 10-20 ℃ in the process, dissolving potassium permanganate by continuous stirring after the addition is finished, removing an ice bath when the reactant temperature is not higher than the upper temperature, replacing the water bath and keeping stirring, heating the reactant to 35 ℃ for 30min for oxidation reaction, adding 45 parts by mass of potassium permanganate, performing hydrolysis reaction at the temperature of 90 ℃ for 30min, adding deionized water, performing hydrolysis reaction for 30min, adding deionized water, adding hydrogen peroxide and drying at the mixture of 10.5 min, adding hydrogen chloride, adding the mixture of the mixture, performing centrifugal reaction for 24.5 min, adding hydrogen chloride, heating to obtain a mixture, and drying at the mixture of graphene, and the mixture of the mixture, and the mixture of 5% of the mixture, and the mixture of graphene, and the mixture, and the.
EDS (electron-dispersive spectroscopy) energy spectrum analysis shows that the relative content of nitrogen atoms in the nitrogen-doped graphene prepared in example 3 is about 1.0%, SEM (scanning electron microscope) characterization results show that the size of a nitrogen-doped graphene sheet layer is 500nm-20 mu m, and TEM (transmission electron microscope) characterization shows that the structure of the nitrogen-doped graphene sheet layer is complete and the number of carbon layers is 1-10.
Example 4
Placing natural flaky graphite (325 meshes) in a crucible, introducing argon at the flow rate of 0.15L/min in a vacuum tube furnace to remove air in the furnace tube, introducing ammonia at the flow rate of 0.1L/min, heating to 1200 ℃ at the speed of 5 ℃/min for heat preservation and heat treatment for 6 hours for pre-nitridation, introducing argon at the flow rate of 0.5 hour after the reaction furnace naturally cools to room temperature, obtaining nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) in a beaker, adding 1 part by mass of nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, magnetically stirring for 30 minutes to perform pre-oxidation intercalation, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the reactant temperature within 10-20 ℃ in the process, continuously stirring to dissolve the high concentration after the addition is finished, removing the ice bath when the reactant temperature does not rise any more, changing the water bath and keeping stirring, heating the reactant to 35 ℃ for heat preservation and heat preservation for 30 minutes to perform intercalation reaction, adding 45 parts by mass of deionized water, magnetically stirring at the temperature of 90 ℃ for 30 minutes, performing hydrolysis reaction for 30 minutes, adding hydrogen at the mixture of 30 minutes, adding hydrogen, stirring, adding hydrogen at the mixture of 60.5 parts by mass of 60 minutes, drying, adding hydrogen at the mixture of 5 ℃/min, and drying to obtain a product, and drying at the concentration of 5 minutes, and adding hydrogen at the temperature of the mixture of 5%, and drying to obtain a product, and adding a mixture, and adding hydrogen, and drying to obtain a product, and drying, and adding a product, and adding hydrogen-doped graphene, and adding a product, and.
EDS (electron-dispersive spectroscopy) energy spectrum analysis shows that the relative content of nitrogen atoms in the nitrogen-doped graphene prepared in the example 4 is about 10.0%, SEM (scanning electron microscope) characterization results show that the size of a nitrogen-doped graphene sheet layer is 500nm-20 mu m, and TEM (transmission electron microscope) characterization shows that the structure of the nitrogen-doped graphene sheet layer is complete and the number of carbon layers is 1-10.
Example 5
Placing commercial high-temperature cracked graphite in a crucible, introducing argon into a vacuum tube furnace at the flow rate of 0.15L/min to remove air in the furnace tube, introducing ammonia gas at the flow rate of 0.06L/min, heating to 700 ℃ at the speed of 5 ℃/min, performing heat preservation and heat treatment for 1h to perform pre-nitridation, introducing argon for 0.5h after the reaction furnace naturally cools to room temperature to obtain nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) in a beaker, adding 1 part by mass of nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, performing pre-oxidation intercalation by magnetic stirring for 30min, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the temperature of reactants within 10-20 ℃ in the process, dissolving potassium permanganate by continuous stirring after the addition is finished, removing the ice bath when the temperature of the reactants does not rise any more, changing the water bath and keeping stirring, heating the reactants to 35 ℃ for heat preservation for 30min to perform oxidation intercalation, adding 45 parts by mass of deionized water, performing hydrolysis reaction at the temperature of 90 ℃ for 30min, adding argon for 30min under magnetic stirring, adding argon for stirring, performing centrifugal stirring, adding deionized water, drying at the temperature of 3.5 ℃/min, adding argon gas, adding deionized water, drying at the mixture of argon for 24.5 min, and drying at the temperature of the mixture, and drying to obtain graphene, and drying the product of graphene, and drying at the temperature of the mixture of graphene, and the mixture of graphene, and the mixture of.
EDS (electron-dispersive spectroscopy) energy spectrum analysis shows that the relative content of nitrogen atoms in the nitrogen-doped graphene prepared in example 5 is about 4.0%, SEM (scanning electron microscope) characterization results show that the size of a nitrogen-doped graphene sheet layer is 1-20 mu m, and TEM (transmission electron microscope) characterization shows that the nitrogen-doped graphene sheet layer has a complete structure and the number of carbon layers is 1-10.
Example 6
Placing commercial high-temperature cracked graphite in a crucible, introducing argon into a vacuum tube furnace at the flow rate of 0.15L/min to remove air in the furnace tube, introducing mixed gas of ammonia and nitrogen (the volume fraction of the ammonia is 50%) at the flow rate of 0.6L/min, heating to 900 ℃ at the speed of 5 ℃/min, carrying out heat preservation and heat treatment for 5h to carry out pre-nitridation, naturally cooling the reaction furnace to room temperature, introducing argon for 0.5h to obtain nitrided graphite, placing 20 parts by mass of concentrated sulfuric acid (98%) in a beaker, adding 1 part by mass of nitrided graphite in an ice water bath at the temperature of 1-5 ℃, carrying out magnetic stirring for 30min to carry out pre-oxidation intercalation, slowly adding 3 parts by mass of potassium permanganate under magnetic stirring while keeping the temperature of the reactant within 10-20 ℃, continuing stirring to dissolve the potassium permanganate after the addition is finished, removing the ice bath when the temperature of the reactant is not raised again, replacing the water bath and keeping stirring, heating the reactant to 35 ℃ for 30min to carry out oxidation reaction, adding 45 parts by mass of deionized water, stirring at the temperature of 90 ℃ for 90 min, carrying out heat preservation and heat reaction for 30min, respectively, adding hydrogen peroxide in a deionized water, adding hydrogen peroxide solution, heating to carry out heat preservation and drying at the reaction for 30min, adding the temperature of the mixture of graphite, and the mixture of the mixture, and the mixture, heating to obtain a product, and drying the product, and drying at the product of graphene, wherein the product of graphene under the mixture of.
EDS (electron-dispersive spectroscopy) energy spectrum analysis shows that the relative content of nitrogen atoms in the nitrogen-doped graphene prepared in the embodiment 6 is about 5.0%, SEM (scanning electron microscope) characterization results show that the size of a nitrogen-doped graphene sheet layer is 1-20 mu m, and TEM (transmission electron microscope) characterization shows that the nitrogen-doped graphene sheet layer has a complete structure and the number of carbon layers is 1-10.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. As for the method and the material disclosed by the embodiment, the description is simple because the method and the material correspond to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A preparation method of low-defect nitrogen-doped graphene is characterized by comprising the following steps:
(1) carrying out heat treatment on a graphite raw material in a nitrogen-containing active atmosphere to carry out pre-nitridation;
(2) stripping the pre-nitrided graphite through chemical oxidation to obtain nitrogen-doped graphene oxide;
(3) and (3) carrying out pyrolysis reduction on the nitrogen-doped graphene oxide obtained in the step (2) to obtain the low-defect nitrogen-doped graphene.
2. The method for preparing low-defect nitrogen-doped graphene according to claim 1, wherein the graphite raw material in the step (1) is natural flaky graphite, cracked expanded graphite or other artificial graphite without any chemical modification.
3. The method according to claim 1, wherein the nitrogen-containing active atmosphere in step (1) is any one of ammonia gas, a mixed gas of ammonia gas and argon gas, a mixed gas of ammonia gas and helium gas, a mixed gas of ammonia gas and nitrogen gas, and a mixed gas of ammonia gas and hydrogen gas.
4. The method as claimed in claim 1, wherein the temperature of the heat treatment in step (1) is 500-1200 ℃, the time of the heat treatment is 0.5-6h, and the gas flow rate is 0.06-0.6L/min.
5. The method according to claim 1, wherein the graphene is naturally cooled to room temperature after the heat treatment in the step (1), and any one of argon, helium and hydrogen or a mixed gas of two or more of the above gases is introduced for 0.5 to 1 hour.
6. The method for preparing low-defect nitrogen-doped graphene according to claim 1, wherein the step (2) of chemically oxidizing and stripping to obtain nitrogen-doped graphene oxide comprises the following specific steps:
placing 20 parts by mass of concentrated sulfuric acid in a beaker, adding 1 part by mass of pre-nitrided graphite in an ice-water bath at the temperature of 1-5 ℃, and carrying out magnetic stirring for 30-60min to carry out pre-oxidation intercalation;
slowly adding 3 parts by mass of potassium permanganate under magnetic stirring, keeping the temperature of reactants between 10 and 20 ℃ in the process, continuously stirring until the potassium permanganate is dissolved after the addition is finished, removing an ice bath when the temperature of the reactants does not rise, replacing the ice bath and keeping stirring, heating the reactants to 35 ℃, keeping the temperature for 30 to 60 minutes, and carrying out oxidation intercalation reaction;
adding 40-60 parts by mass of deionized water, and carrying out hydrolysis reaction at the temperature of 90-95 ℃ for 15-30min under magnetic stirring;
continuously adding 3-10 parts by mass of hydrogen peroxide and 20-30 parts by mass of deionized water under magnetic stirring, stopping stirring after 3-10min, centrifuging the reaction solution at 10000rpm for 5-10min, then respectively cleaning the centrifuged product by using 3% by mass of HCl aqueous solution and deionized water for 3-5 times, and drying the product in an oven at 60-80 ℃ for 12-48h to obtain the nitrogen-doped graphene oxide.
7. The method as claimed in claim 1, wherein the pyrolysis reduction temperature in step (3) is 500-1200 ℃, and the pyrolysis reduction time is 30s-1 h.
8. The method according to claim 1, wherein the pyrolysis atmosphere in step (3) is any one of argon, helium and hydrogen, or a mixture of two or more of the above gases, and the gas flow rate is 0.06-0.6L/min.
9. The low-defect nitrogen-doped graphene synthesized by the method according to any one of claims 1 to 8, wherein nitrogen atoms contained in the nitrogen-doped graphene are respectively connected in a graphite layer by graphite type nitrogen and pyridine type nitrogen.
10. The low-defect nitrogen-doped graphene according to claim 9, wherein the nitrogen atom content of the nitrogen-doped graphene is 1-10%, the number of nitrogen-doped graphene layers is 1-10, and the size of a single layer is 50nm-50 μm.
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| CN103359711A (en) * | 2012-03-27 | 2013-10-23 | 海洋王照明科技股份有限公司 | Preparation method of nitrogen-doped graphene |
| CN103803539A (en) * | 2014-02-17 | 2014-05-21 | 上海交通大学 | Nitrogen-doped graphene oxide material and preparation method thereof |
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