CN104528703B - Preparation method of nitrogen/phosphorus-codoped graphene - Google Patents

Abstract

The invention discloses a preparation method of nitrogen-phosphorus co-doped graphene, comprising the following steps: S100: uniformly mixing phosphorus-containing compounds, nitrogen-containing organic substances and six-carbon compounds according to a certain ratio, and pulverizing after drying or directly pulverizing to obtain Precursor particles; wherein, the molar ratio of N atoms in the nitrogen-containing organic compound to C atoms in the six-carbon compound is 10:1 to 100:1, and the ratio of the N atom in the nitrogen-containing organic compound to the C atom in the phosphorus-containing compound The molar ratio of P atoms is 10:1 to 1000:1; S200: Put the precursor particles in a heating furnace, pass in protective gas, keep warm at 800°C to 1300°C for 0.5h to 5h, and then cool Nitrogen-phosphorus co-doped graphene was obtained. The preparation process is simple, the raw materials are easy to obtain, the cost is low, the output is high, and it is easy to scale production; and the distribution of N atoms and P atoms in the obtained graphene is uniform, the doping concentration is adjustable, the product quality is good, and it has high practical application value.

Description

Preparation method of nitrogen and phosphorus co-doped graphene

technical field

The invention relates to the technical field of material preparation, in particular to a preparation method of nitrogen-phosphorus co-doped graphene.

Background technique

Graphene is a new two-dimensional carbon material composed of planar extensions of six-membered rings of C atoms. Good carrier mobility and super large specific surface area make graphene a material star. However, pure graphene is prone to interlayer reattachment due to van der Waals force and Coulomb electrostatic force during use and loses the ability to store charges. Studies have shown that the uniform distribution of free charges on both sides of the graphene sheet can be changed by doping, and the free electrons in a certain range around the dopant atoms can be localized, resulting in bending and wrinkles in the graphene sheet. Wrinkled graphene sheets can provide strong support, thereby avoiding stacking and recombination between graphene sheets, and at the same time can increase the overall porosity and mesopore fraction, thereby affecting the application of graphene in the fields of energy storage, catalysis, and environmental protection. application.

At present, graphene containing dopant atoms is mainly prepared by chemical vapor deposition and ion implantation. However, the above two methods have strict requirements on equipment and technology and high preparation costs, which are not conducive to large-scale production.

Contents of the invention

Based on the above problems, the present invention provides a method for preparing simple and low-cost nitrogen-phosphorus co-doped graphene.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method for nitrogen-phosphorus co-doped graphene, comprising the following steps:

S100: Mix the phosphorus-containing compound, the nitrogen-containing organic matter and the six-carbon compound uniformly according to a certain ratio, and pulverize after drying or directly pulverize to obtain precursor particles;

Wherein, the molar ratio of the N atom in the nitrogen-containing organic compound to the C atom in the six-carbon compound is 10:1 to 100:1, and the molar ratio of the N atom in the nitrogen-containing organic compound to the P atom in the phosphorus-containing compound The ratio is 10:1～1000:1;

S200: placing the precursor particles in a heating furnace, introducing a protective gas, keeping the temperature at 800°C-1300°C for 0.5h-5h, and obtaining nitrogen-phosphorus co-doped graphene after cooling.

In one of the embodiments, the nitrogen-containing organic matter is one or more of urea, melamine and dicyandiamide;

The six-carbon compound is one or more of pentahydroxymethylfurfural, glucose, mannose and alginic acid;

The phosphorus-containing compound is one or both of phosphoric acid and triphenylphosphine.

In one embodiment, in S100, the phosphorus-containing compound, the nitrogen-containing organic compound and the six-carbon compound are uniformly mixed by means of impregnation, co-dissolution or solid co-grinding.

In one of the embodiments, when the phosphorus-containing compound is phosphoric acid, the phosphorus-containing compound, nitrogen-containing organic matter and six-carbon compound are uniformly mixed in the following manner:

The nitrogen-containing organic matter and the phosphoric acid aqueous solution with a mass concentration of 1wt%-20wt% are impregnated in equal volumes, and then the hexacarbon compound is added and stirred evenly.

In one embodiment, in S100, the drying condition is: drying at 60° C. to 100° C. for 12 hours to 24 hours.

In one embodiment, in S100, the particle size of the precursor particles is less than or equal to 20 mesh.

In one embodiment, in S200, the linear flow rate of the introduced protective gas is 1 cm/min˜10 cm/min.

In one of the embodiments, in S200, the temperature control process of the heating furnace is as follows: the temperature is raised from room temperature to 600°C to 700°C at a speed of 1°C/min to 5°C/min, and then the temperature is set at 2°C after holding for 1h to 5h. /min～10℃/min, continue to heat up to 800℃～1300℃, keep warm for 0.5h～3h, then cool to room temperature.

In one embodiment, in S200, the temperature control process of the heating furnace is as follows: heating from room temperature to 800°C to 1300°C at a rate of 1°C/min to 5°C/min, keeping the temperature for 1h to 5h, and then cooling to room temperature.

In one embodiment, the protective gas is one or more of nitrogen, argon and helium.

The present invention has the following beneficial effects:

The present invention can obtain nitrogen and phosphorus co-doped graphene through one-time solid-phase thermal cracking. Compared with traditional methods, the method of the present invention has lower requirements on equipment and technology, simple preparation process, easy to obtain raw materials, and low cost. The yield is high, it is easy to produce on a large scale, and the preparation process does not need the support of the substrate, which avoids the problem that the graphene is difficult to separate from the substrate; at the same time, the distribution of N atoms and P atoms in the graphene obtained by the method of the present invention is uniform, and the doped The impurity concentration is adjustable, the product quality is good, and it has high practical application value.

Description of drawings

Fig. 1 is the Raman spectrogram of the nitrogen-phosphorus co-doped graphene obtained in the embodiment of the present invention 1;

Fig. 2 is the scanning electron micrograph of the nitrogen-phosphorus co-doped graphene obtained in the embodiment of the present invention 1;

Fig. 3 is the transmission electron microscope figure of the nitrogen-phosphorus co-doped graphene obtained in the embodiment of the present invention 1;

Fig. 4 is the atomic force microscope characterization result of the nitrogen-phosphorus co-doped graphene obtained in Example 1 of the present invention, wherein, the background is an atomic force electron microscope photo, and the curve is a height measurement curve of graphene;

Fig. 5 is the nitrogen physical adsorption result of the nitrogen-phosphorus co-doped graphene obtained in Example 1 of the present invention;

Fig. 6 is an X-ray photoelectron spectrum diagram of the nitrogen-phosphorus co-doped graphene obtained in Example 1 of the present invention.

detailed description

Specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The invention provides a method for preparing nitrogen-phosphorus co-doped graphene. The graphene prepared by the method is evenly doped, has high yield, and the obtained product has stable physical and chemical properties, and is not easy to occur due to flakes during use. A situation in which graphene properties are lost due to layer stacking recombination.

The preparation method of the present invention comprises the following steps:

S100, preparation of precursor particles: uniformly mix phosphorus-containing compounds, nitrogen-containing organic substances, and six-carbon compounds in a certain proportion, and then pulverize or directly pulverize after drying to obtain precursor particles; The molar ratio of C atoms in the compound is 10:1-100:1, and the molar ratio of N atoms in the nitrogen-containing organic compound to P atoms in the phosphorus-containing compound is 10:1-1000:1.

Preferably, as an implementable manner, the nitrogen-containing organic compound is one or more (including two) of urea, melamine, and dicyandiamide; the hexacarbon compound is a compound containing 6 C atoms, preferably five One or more (including two) of hydroxymethylfurfural, glucose, and mannose alginic acid; the phosphorus-containing compound is phosphoric acid, triphenylphosphine, or a mixture of the two. Since phosphoric acid has a pore-forming effect and can increase the specific surface area of the finally obtained graphene, the phosphorus-containing compound is preferably phosphoric acid or a mixture of phosphoric acid and triphenylphosphine.

In the present invention, the phosphorus-containing compound, the nitrogen-containing organic compound and the six-carbon compound can be homogeneously mixed by means of impregnation, co-dissolution or solid co-grinding. For example, the nitrogen-containing organic matter can be immersed in the aqueous solution of the phosphorus-containing compound first, and then the six-carbon compound is added, and stirred evenly; the phosphorus-containing compound, nitrogen-containing organic matter and six-carbon compound can also be dissolved in a certain amount of water, And stir evenly; it can also directly mix phosphorus-containing compounds, nitrogen-containing organic compounds and six-carbon compounds, and then grind them evenly.

Further, when the phosphorus-containing compound is phosphoric acid, the phosphorus-containing compound, nitrogen-containing organic matter and six-carbon compound can be uniformly mixed in the following manner: the nitrogen-containing organic matter and a phosphoric acid aqueous solution with a mass concentration of 1wt% to 20wt% are impregnated in equal volumes, and then Add the hexa compound and mix well. Equal-volume impregnation speed is fast, mixing is uniform, and it is suitable for industrial production; and within the concentration range of phosphoric acid, it is beneficial to obtain graphene with better performance.

After the phosphorus-containing compound, nitrogen-containing organic matter and six-carbon compound are uniformly mixed in a certain proportion, if there is free water in the mixture, drying operation is required to remove the free water in the mixture, and then the step of crushing is carried out, if If there is no free water in the mixture, the mixture can be crushed directly. Preferably, the drying condition is: drying at 60° C. to 100° C. for 12 hours to 24 hours. Among them, the crushing method is preferably mechanical crushing, such as mechanical grinding. It should be noted that the mixing process and pulverization process of nitrogen-containing organic matter, phosphorus-containing compound and six-carbon compound can be carried out simultaneously.

In the present invention, there is no special limitation on the particle size of the precursor particles obtained after pulverization. In order to prepare nitrogen-phosphorus co-doped graphene with excellent performance and enhance its physical and chemical stability, preferably, the particle size of the precursor particles is less than or equal to 20 mesh.

S200, solid-phase thermal cracking reaction: place the precursor particles obtained in step S100 in a heating furnace, pass through a protective gas, and keep warm at 800°C-1300°C for 0.5h-5h, and after cooling, nitrogen and phosphorus co-doping can be obtained miscellaneous graphene.

Preferably, the nitrogen-phosphorus co-doped graphene obtained in the present invention has 2-3 layers of graphene sheets.

This step obtains the required nitrogen-phosphorus co-doped graphene by solid-phase thermal cracking, wherein the heating furnace is preferably a tube furnace with a built-in quartz tube or corundum tube to facilitate the introduction of a protective gas. The protective gas is preferably nitrogen, One or more of argon and helium. The flow rate of the shielding gas should not be too large, and the linear flow rate is preferably 1 cm/min to 10 cm/min. At this speed, the yield and purity of the product can be guaranteed, and the oxidation of the product can be prevented, thereby improving the physical and chemical properties of the product.

In step S200, the heating method may adopt a one-step heating method or a staged heating method. In order to improve the quality of the product, the heating speed should not be too fast. Preferably, when the one-step heating method is adopted, the temperature control process of the heating furnace is: the temperature is raised from room temperature to 800°C to 1300°C at a speed of 1°C/min to 5°C/min. ℃, keep warm for 1h~5h, then cool down to room temperature; when adopting staged heating method, the temperature control process of the heating furnace is: from room temperature to 600℃~700℃ at a speed of 1℃/min~5℃/min, After 1h-5h of heat preservation, continue to heat up to 800°C-1300°C at a rate of 2°C/min-10°C/min, keep heat for 0.5h-3h, and cool to room temperature.

In the present invention, the main function of the nitrogen-containing organic matter is to provide a template to allow the six-carbon compound to polymerize and form an interlayer compound. After the temperature rises, most of the nitrogen-containing organic matter will volatilize or sublimate and escape, leaving a layered carbon skeleton. Thereby providing a basis for the generation of graphene; the role of phosphorus-containing compounds is to provide P sources, when phosphoric acid exists in phosphorus-containing compounds, because phosphoric acid and the intermediate products produced in the pyrolysis process have a pore-forming effect, it can improve Graphene specific surface area.

It should be noted that in the finally obtained nitrogen-phosphorus co-doped graphene, the doping concentration of N atoms and P atoms can be regulated by the ratio of each raw material at the beginning.

The preparation method of nitrogen-phosphorus co-doped graphene of the present invention adopts a completely different preparation approach from the traditional preparation method, and the raw materials used in the method of the present invention are commonly used chemical raw materials, and the cost is relatively low; meanwhile, the method of the present invention is beneficial to The requirements for equipment and technology are low, nitrogen and phosphorus co-doped graphene can be obtained at one time through solid-phase thermal cracking, the operation is simple, and it is easy to produce on a large scale; the distribution of N atoms and P atoms in the graphene obtained by the method of the present invention is uniform , the doping concentration is adjustable, so as to meet the application of graphene in different fields; and the graphene obtained in the present invention has a hierarchical porous structure, has better self-supporting performance, and has the advantages of ultra-light and ultra-high specific surface area at the same time, It can resist stacking and recombination during use, has stable physical and chemical properties and excellent service life; in addition, the preparation process of this method does not require the support of the substrate, which avoids the problem that graphene is difficult to separate from the substrate.

In order to better understand the present invention, the preparation method of the nitrogen-phosphorus co-doped graphene of the present invention will be further described below through specific examples. The reaction raw materials in the following examples are all commercially available raw materials.

Example 1

(1) Add 80g of dicyandiamide in a beaker, then impregnate it with the equal volume of phosphoric acid with a mass concentration of 10wt%, then add 2g of pentamethylenefurfural, stir evenly at 80°C, put it into an oven at 100°C Dry for 12 hours, take it out and grind to obtain precursor particles with a particle size of 20 mesh or less. Wherein, the molar ratio of N atoms in dicyandiamide to C atoms in pentamethylenefurfural is 40:1, and the molar ratio of N atoms in dicyandiamide to P atoms in phosphoric acid is 60:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal it and feed high-purity nitrogen as a full-process protective gas, wherein the linear flow rate of nitrogen is 2cm/min; Raise the temperature to 600°C at a rate of 2°C/min, hold for 2 hours, then raise the temperature to 1000°C at a rate of 5°C/min, hold for 1 hour, and cool to room temperature naturally. The obtained product is nitrogen-phosphorus co-doped graphene.

Referring to Fig. 1, it is the Raman spectrogram of the nitrogen-phosphorus co-doped graphene obtained in this embodiment, as can be seen from the figure, there are three characteristic peaks at 1340cm ^-1 , 1580cm ^-1 and 2680cm ^-1 , respectively D, G and 2D peaks indicate that the product obtained is graphene; Fig. 2 is a scanning electron microscope image of the nitrogen-phosphorus co-doped graphene obtained in this embodiment, and the obvious wrinkled graphene sheet structure can be seen from the figure; Fig. 3 is this The transmission electron microscope figure of the nitrogen-phosphorus co-doped graphene obtained in the embodiment, as seen from the figure, the graphene has porous characteristics; Fig. 4 is the atomic force microscope characterization result of the nitrogen-phosphorus co-doped graphene obtained in the present embodiment, and the height measurement shows It is 2 to 3 layers of graphene sheets; Figure 5 shows the nitrogen physical adsorption results of nitrogen and phosphorus co-doped graphene obtained in this example, its specific surface area is as high as 1960m ² /g, rich in micropores and mesopores, and mesopores Aperture has concentrated distribution at about 4nm; Fig. 6 is the X-ray photoelectron energy spectrogram of the nitrogen-phosphorus co-doped graphene that the present embodiment obtains, and the result shows, nitrogen, phosphorus element composition are respectively 5.07% (atomic ratio, The same below), 0.99%, and the lower oxygen content is 5.89%.

Example 2

(1) Add 80g of dicyandiamide in a beaker, then impregnate it with the equal volume of phosphoric acid with a mass concentration of 20wt%, then add 2g of pentamethylenefurfural, stir evenly at 80°C, put it into an oven at 100°C Dry for 12 hours, take it out and grind to obtain precursor particles with a particle size of 20 mesh or less. Wherein, the molar ratio of N atoms in dicyandiamide to C atoms in pentamethylenefurfural is 40:1, and the molar ratio of N atoms in dicyandiamide to P atoms in phosphoric acid is 30:1.

(2) With embodiment 1.

Compared with Example 1, the concentration of phosphoric acid in the raw materials used in this example has changed, and all the other preparation conditions have not changed. With the increase of phosphoric acid concentration, the total amount of nitrogen and phosphorus co-doped graphene obtained finally The pore volume and specific surface area both increase.

Example 3

(1) Add 80g of dicyandiamide in a beaker, then impregnate it with the equal volume of phosphoric acid with a mass concentration of 1wt%, then add 2g of pentamethylenefurfural, stir evenly at 80°C, put it into an oven at 100°C Dry for 12 hours, take it out and grind to obtain precursor particles with a particle size of 20 mesh or less. Wherein, the molar ratio of N atoms in dicyandiamide to C atoms in pentamethylene furfural is 40:1, and the molar ratio of N atoms in dicyandiamide to P atoms in phosphoric acid is 600:1.

(2) With embodiment 1.

Compared with Example 1, the concentration of phosphoric acid in the raw materials used in this example has changed, and all the other preparation conditions have not changed. With the reduction of phosphoric acid concentration, the micropores of the nitrogen-phosphorus co-doped graphene finally obtained The number, total pore volume and specific surface area all decrease.

Example 4

(1) Add 120g of dicyandiamide, 1.5g of pentamethylenefurfural, 3.78ml of analytically pure concentrated phosphoric acid and 600ml of deionized water into a beaker, stir evenly at 80°C, and then dry in an oven at 80°C for 16h , remove free water, take it out and grind it to obtain precursor particles with a particle size of less than or equal to 20 mesh. Wherein, the molar ratio of the N atom in the dicyandiamide to the C atom in the pentamethylene furfural is 80:1, and the molar ratio of the N atom in the dicyandiamide to the P atom in the concentrated phosphoric acid is 100:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity argon as a full-process protective gas, wherein the linear flow rate of argon is 5cm/min; After 1h, the temperature was raised to 1000°C at a rate of 2°C/min, kept for 2h, and cooled to room temperature naturally, and the obtained product was nitrogen-phosphorus co-doped graphene.

Example 5

(1) Add 20g of dicyandiamide, 2g of pentamethylenefurfural, 6.3ml of analytically pure concentrated phosphoric acid and 500ml of deionized water into a beaker, stir evenly at 60°C, then place in a 60°C oven and dry for 24h, Remove free water, take it out and grind to obtain precursor particles with a particle size of 20 mesh or less. Wherein, the molar ratio of the N atom in the dicyandiamide to the C atom in the pentamethylenefurfural is 10:1, and the molar ratio of the N atom in the dicyandiamide to the P atom in the concentrated phosphoric acid is 10:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity argon as a full-process protective gas, wherein the linear flow rate of argon is 2cm/min; After 0.5h, the temperature was raised to 800°C at a rate of 1°C/min, kept for 5h, and cooled to room temperature naturally. The obtained product was nitrogen-phosphorus co-doped graphene.

Example 6

(1) Add 160g of melamine and 2.3g of mannose into a beaker, then add 0.55ml of phosphoric acid with a mass concentration of 20wt% into the beaker, stir evenly, and then place in a ball mill and mill for 60min to obtain precursor particles. Wherein, the molar ratio of N atoms in melamine to C atoms in mannose is 100:1, and the molar ratio of N atoms in melamine to P atoms in phosphoric acid is 1000:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity nitrogen as a full-process protective gas, wherein the linear flow rate of nitrogen is 5cm/min; ventilate for a period of time Then raise the temperature to 700°C at a speed of 1°C/min, keep it warm for 5 hours, then raise the temperature to 1300°C at a speed of 10°C/min, keep it warm for 0.5h, and cool down to room temperature naturally. The obtained product is nitrogen-phosphorus co-doped graphene .

Example 7

(1) Add 160 g of melamine and 2.3 g of glucose into a beaker, then add 2 g of triphenylphosphine into the beaker, stir evenly, and then place it in a ball mill for 30 min to obtain precursor particles. Wherein, the molar ratio of N atoms in melamine to C atoms in glucose is 100:1, and the molar ratio of N atoms in melamine to P atoms in triphenylphosphine is 1000:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity helium as a full-range protective gas, wherein the linear flow rate of helium is 4cm/min; After a period of time, the temperature was raised to 650°C at a rate of 5°C/min, kept for 1 hour, then raised to 800°C at a rate of 10°C/min, kept for 3 hours, and naturally cooled to room temperature. The obtained product is nitrogen-phosphorus co-doped graphite alkene.

Example 8

(1) Add 160g of dicyandiamide, 2.3g of glucose, 0.5ml of analytically pure concentrated phosphoric acid, and 2g of triphenylphosphine into a beaker, stir evenly, and then place it in a ball mill for 60 minutes to obtain precursor particles. Wherein, the molar ratio of the N atom in dicyandiamide to the C atom in pentamethylenefurfural is 100:1, and the molar ratio of the N atom in dicyandiamide to the sum of the P atoms in concentrated phosphoric acid and triphenylphosphine It is 500:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity argon as a full-range protective gas, wherein the linear flow rate of argon is 6cm/min; After 1h, the temperature was raised to 1300°C at a rate of 4°C/min, kept for 1h, and cooled to room temperature naturally, and the obtained product was nitrogen-phosphorus co-doped graphene.

Example 9

(1) Add 120g of urea, 1.2g of glucose, 0.26ml of analytically pure concentrated phosphoric acid and 700ml of deionized water into a beaker, stir evenly at 65°C, then dry in an oven at 100°C for 16h to remove free water, take out Post-grinding to obtain precursor particles with a particle size of less than or equal to 20 mesh. Wherein, the molar ratio of N atoms in urea to C atoms in glucose is 100:1, and the molar ratio of N atoms in urea to P atoms in concentrated phosphoric acid is 1000:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity argon as a full-process protective gas, wherein the linear flow rate of argon is 7cm/min; After 1h, the temperature was raised to 700°C at a rate of 5°C/min, kept for 3 hours, then raised to 1200°C at a rate of 4°C/min, kept at a temperature of 1.5h, and cooled to room temperature naturally. The obtained product is nitrogen-phosphorus co-doped graphite alkene.

Example 10

(1) Add 60g of urea, 6g of alginic acid, 1.3ml of analytically pure phosphoric acid and 300ml of deionized water into a beaker, stir evenly at 65°C, and then dry in an oven at 80°C for 16 hours to remove free water. Grinding to obtain precursor particles with a particle size less than or equal to 20 mesh. Wherein, the molar ratio of N atoms in urea to C atoms in alginic acid is 10:1, and the molar ratio of N atoms in urea to P atoms in phosphoric acid is 100:1.

(2) Place the precursor particles obtained in step (1) in a quartz boat in a tube furnace, seal and feed high-purity argon as a full-process protective gas, wherein the linear flow rate of argon is 4cm/min; After 0.5h, heat up to 680°C at a rate of 5°C/min, hold for 2.5h, then heat up to 1100°C at a rate of 5°C/min, hold for 2h, and cool down to room temperature naturally. The obtained product is nitrogen and phosphorus co-doping Graphene.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (9)

1. a preparation method of nitrogen-phosphorus co-doped graphene, is characterized in that, comprises the following steps: S100: Mix the phosphorus-containing compound, the nitrogen-containing organic matter and the six-carbon compound uniformly according to a certain ratio, and pulverize after drying or directly pulverize to obtain precursor particles; Wherein, the molar ratio of the N atom in the nitrogen-containing organic compound to the C atom in the six-carbon compound is 10:1 to 100:1, and the molar ratio of the N atom in the nitrogen-containing organic compound to the P atom in the phosphorus-containing compound The ratio is 10:1～1000:1; S200: Put the precursor particles in a heating furnace, pass in a protective gas, keep warm at 800°C-1300°C for 0.5h-5h, and obtain nitrogen-phosphorus co-doped graphene after cooling, The nitrogen-containing organic matter is one or more of urea, melamine and dicyandiamide; The six-carbon compound is one or more of pentahydroxymethylfurfural, glucose, mannose and alginic acid; The phosphorus-containing compound is one or both of phosphoric acid and triphenylphosphine. 2. the preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, is characterized in that, in S100, described phosphorus-containing compound, nitrogen-containing organic matter and hexacarbon compound are obtained by impregnation, co-dissolution or solid co-grinding Way to mix well. 3. the preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, is characterized in that, when described phosphorus-containing compound is phosphoric acid, described phosphorus-containing compound, nitrogen-containing organic matter and six-carbon compound are mixed by following way Uniform: The nitrogen-containing organic matter and the phosphoric acid aqueous solution with a mass concentration of 1wt%-20wt% are impregnated in equal volumes, and then the hexacarbon compound is added and stirred evenly. 4. The method for preparing nitrogen-phosphorus co-doped graphene according to claim 1, characterized in that, in S100, the drying condition is: drying at 60°C-100°C for 12h-24h. 5. The preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, characterized in that, in S100, the particle size of the precursor particles is less than or equal to 20 mesh. 6 . The method for preparing nitrogen-phosphorus co-doped graphene according to claim 1 , characterized in that, in S200 , the linear flow velocity of the introduced protective gas is 1 cm/min˜10 cm/min. 7. The preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, characterized in that, in S200, the temperature control process of the heating furnace is: at a speed of 1°C/min～5°C/min by The room temperature is raised to 600°C-700°C, after 1h-5h of heat preservation, the temperature is continuously raised to 800°C-1300°C at a speed of 2°C/min-10°C/min, after 0.5h-3h of heat preservation, it is cooled to room temperature. 8. The preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, characterized in that, in S200, the temperature control process of the heating furnace is: at a speed of 1°C/min～5°C/min by Raise the temperature from room temperature to 800°C to 1300°C, keep it warm for 1h to 5h, and then cool to room temperature. 9. The preparation method of nitrogen-phosphorus co-doped graphene according to claim 1, wherein the protective gas is one or more of nitrogen, argon and helium.