Nitrogen-doped graphitized carbon microspheres, preparation method and application thereof

Abstract

The application relates to the technical field of functional materials, in particular to nitrogen-doped graphitized carbon microspheres and a preparation method and application thereof. The preparation method provided by the application comprises the following steps: performing carbonization treatment on polymer-based microspheres to prepare polymer-based carbon microspheres; performing activation treatment on the polymer-based carbon microspheres by using an activator to prepare porous carbon microspheres; mixing the porous carbon microspheres, a catalyst, a nitrogen source and a solvent, and performing heat treatment under vacuum conditions to prepare nitrogen-doped carbon microspheres; the catalyst comprises one or more of metal salt catalysts and non-metal oxide catalysts; the temperature of the heat treatment is 90 DEG C-200 DEG C; under a protective atmosphere, the nitrogen-doped carbon microspheres are subjected to graphitization treatment at 900 DEG C-1700 DEG C to prepare nitrogen-doped graphitized carbon microspheres. The preparation method provided by the application has the advantages of low graphitization temperature, low energy consumption and easy large-scale production, and the nitrogen-doped graphitized carbon microspheres prepared by the method have a high nitrogen doping amount.

Description

Technical Field

[0001] This application relates to the field of functional materials technology, specifically to nitrogen-doped graphitized carbon microspheres, their preparation methods, and applications. Background Technology

[0002] Carbon materials have excellent advantages such as high thermal conductivity, high heat resistance, and stable physical and chemical properties, and are widely used in energy, chemical industry, environmental protection, electronics and aerospace fields.

[0003] Among various carbon materials, graphitized carbon has been extensively studied due to its higher electrical conductivity and excellent machinability. Graphitized carbon is formed by stacking multiple layers of graphene. Currently, the main method for preparing graphitized carbon involves heating amorphous carbon to 2500 ℃~3000 ℃ in a graphitization furnace to graphitize the amorphous carbon. However, this method requires expensive graphitization furnaces and consumes a large amount of energy.

[0004] Besides graphitized carbon, nitrogen-doped carbon substitutes nitrogen atoms for carbon. The lone pair electrons of nitrogen atoms can enhance the electron donor properties of the material, affect the π-π conjugated system, and increase the delocalized electron density. Therefore, nitrogen-doped carbon exhibits excellent electrical conductivity, high capacity efficiency, and high thermal stability, providing new ideas for the development of energy storage devices. Currently, there are two main methods for preparing nitrogen-doped carbon. One method involves directly synthesizing nitrogen-doped carbon by using gases or small organic molecules as precursors and employing an assembly process. Representative methods include chemical vapor deposition and chemical synthesis. The other method uses graphite, graphene, or graphene oxide as the base material and performs doping substitution using dopants. Representative methods include ball milling and hydrothermal methods. However, the former method is difficult to achieve large-scale preparation of nitrogen-doped carbon, while the latter method results in a low nitrogen doping rate (nitrogen content ≤ 5%). Summary of the Invention

[0005] Based on this, this application provides a nitrogen-doped graphitized carbon microsphere, its preparation method, and its application. The preparation method provided in this application has the advantages of low graphitization temperature, low energy consumption, and ease of large-scale production. At the same time, the nitrogen-doped graphitized carbon microspheres prepared by this method have a high nitrogen doping content.

[0006] A first aspect of this application provides a method for preparing nitrogen-doped graphitized carbon microspheres, comprising the following steps:

[0007] Polymer-based carbon microspheres are prepared by carbonizing carbon-containing polymer-based microspheres.

[0008] Porous carbon microspheres were prepared by activating the polymer-based carbon microspheres with an activating agent.

[0009] The porous carbon microspheres, catalyst, nitrogen source, and solvent are mixed and heat-treated under vacuum conditions to prepare the nitrogen-doped carbon microspheres; the catalyst includes one or more of metal salt catalysts and non-metal oxide catalysts, and the heat treatment temperature is 90 ℃~200 ℃;

[0010] The nitrogen-doped carbon microspheres were graphitized at 900 °C to 1700 °C under a protective atmosphere to prepare the nitrogen-doped graphitized carbon microspheres.

[0011] In one embodiment, the specific process parameters of the graphitization treatment include: heating to 900 ℃ to 1700 ℃ at a heating rate of 2 ℃ / min to 15 ℃ / min, and holding at that temperature for 4 h to 16 h.

[0012] In one embodiment, the preparation method has one or more of the following features:

[0013] (1) The mass ratio of the porous carbon microspheres to the catalyst is (0.2~0.4):(0.2~2.4);

[0014] (2) The catalyst comprises one or more of the following: metal nitrate, metal halide salt, metal sulfate, metal acetate, metal dicthecinate, metal ethylenediaminetetraacetate, molybdate, and boron trioxide;

[0015] (3) The process parameters of the carbonization treatment include: carbonization temperature of 500 ℃~900 ℃.

[0016] In one embodiment, the activator includes one or more of liquid and gaseous activators.

[0017] The liquid activator includes one or more of the following: deionized water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and ammonia.

[0018] The gaseous activator includes one or more of carbon monoxide, carbon dioxide, and oxygen.

[0019] In one embodiment, the specific steps of activating the polymer-based carbon microspheres with an activator include:

[0020] After the carrier gas is bubbled through the liquid surfactant, the carrier gas is flowed through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and the activation treatment is carried out at a temperature of 800 °C to 1100 °C.

[0021] Alternatively, the gaseous activator can be flowed through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and activated at a temperature of 800 °C to 1100 °C.

[0022] In one embodiment, the carbon-containing polymer-based microspheres are phenolic resin-based microspheres, and the preparation steps of the phenolic resin-based microspheres include:

[0023] The phenolic source and aldehyde source are mixed in a solvent to prepare a mixture; after the mixture undergoes a polycondensation reaction, phenolic resin-based microspheres are prepared.

[0024] In one embodiment, the preparation method has one or more of the following features:

[0025] (1) The phenol source includes one or more of resorcinol, hydroquinone, catechol, phloroglucinol, m-aminophenol and p-aminophenol;

[0026] (2) The aldehyde source includes one or more of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, salicylaldehyde and aldehyde precursors; the aldehyde precursor includes hexamethylenetetramine.

[0027] A second aspect of this application provides nitrogen-doped graphitized carbon microspheres, prepared by any of the preparation methods described in the first aspect of this application.

[0028] In one embodiment, the nitrogen-doped graphitized carbon microspheres have one or more of the following characteristics:

[0029] (1) The area ratio of the Raman spectrum D peak intensity to the Raman spectrum G peak intensity of the nitrogen-doped graphitized carbon microspheres is 1.0~2.0;

[0030] (2) The BET specific surface area of ​​the nitrogen-doped graphitized carbon microspheres is 150 m². 2 / g~600 m 2 / g;

[0031] (3) The particle size of the nitrogen-doped graphitized carbon microspheres is 0.1 μm to 10.0 μm;

[0032] (4) The nitrogen content of the nitrogen-doped graphitized carbon microspheres is 5.5% to 16.5%.

[0033] A third aspect of this application provides the application of nitrogen-doped graphitized carbon microspheres as described in any of the second aspects of this application in electrode materials, conductive materials, catalyst supports, and thermally conductive materials.

[0034] This application has the following beneficial effects:

[0035] The preparation method provided in this application includes carbonization, activation, nitrogen doping, and graphitization. The activation treatment prepares porous carbon microspheres that help improve the specific surface area and adsorption performance of the material. Further nitrogen doping heat treatment is performed under catalytic conditions. The catalyst lowers the energy barrier for nitrogen atom insertion into the carbon framework, making it easier for nitrogen atoms to substitute or insert into the carbon network. This allows the heat treatment temperature to be between 90 °C and 200 °C, while also forming a stable nitrogen-doped carbon structure. Furthermore, the catalyst is retained in the nitrogen-doped carbon structure to further catalyze graphitization, lowering the graphitization temperature to between 900 °C and 1700 °C.

[0036] In summary, the preparation method provided in this application has the advantages of low graphitization temperature, low energy consumption, and ease of large-scale production. Furthermore, the nitrogen-doped graphitized carbon microspheres prepared by this method have a high nitrogen doping content. Moreover, the nitrogen-doped graphitized carbon microspheres prepared by this method possess unique microstructure characteristics, high structural integrity, high nitrogen doping content, and large surface area. The nitrogen-doped graphitized carbon microspheres prepared in this application have broad application prospects in electrode materials, conductive materials, catalyst supports, and thermally conductive materials. Attached Figure Description

[0037] Figure 1 This is a SEM image of the nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application;

[0038] Figure 2 XEDS image of nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application;

[0039] Figure 3 TEM image of nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application;

[0040] Figure 4 XRD patterns of nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application, graphitized carbon microspheres in Comparative Example 1, and porous carbon microspheres in Comparative Example 2.

[0041] Figure 5 Raman images of nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application, graphitized carbon microspheres in Comparative Example 1, and porous carbon microspheres in Comparative Example 2.

[0042] Figure 6 The nitrogen adsorption-desorption curve is shown for the nitrogen-doped graphitized carbon microspheres prepared in Example 1 of this application. Detailed Implementation

[0043] The nitrogen-doped graphitized carbon microspheres of this application, their preparation method, and their applications are described in further complete and clear manner below with reference to specific embodiments. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0044] Graphitized carbon is typically produced by heating amorphous carbon to 2500℃~3000℃ in an electric furnace. Researchers believe the mechanism of this process mainly includes: as the temperature gradually increases, carbonization intermediates and layered liquid crystals begin to appear in the amorphous carbon; with continued temperature increases, carbon atoms gradually stack in an ordered manner, eventually forming a perfectly ordered graphite-like structure; graphitized carbon contains some graphene structures with fewer stacked layers. Graphene possesses a very high specific surface area, extremely high mechanical strength, extremely strong electronic conductivity, good flexibility, and ease of chemical processing.

[0045] Based on this, the first aspect of this application provides a method for preparing nitrogen-doped graphitized carbon microspheres, comprising the following steps:

[0046] S20. Carbon-containing polymer-based microspheres are carbonized to prepare polymer-based carbon microspheres;

[0047] S30. The polymer-based carbon microspheres are activated using an activator to prepare porous carbon microspheres;

[0048] S40. The porous carbon microspheres, catalyst, nitrogen source and solvent are mixed and heat-treated under vacuum to prepare the nitrogen-doped carbon microspheres; the catalyst includes one or more of metal salt catalysts and non-metal oxide catalysts, and the heat treatment temperature is 90 ℃~200 ℃;

[0049] S50. Under a protective atmosphere, the nitrogen-doped carbon microspheres are graphitized at 900 ℃ to 1700 ℃ to prepare the nitrogen-doped graphitized carbon microspheres.

[0050] Understandably, the heat treatment temperature of this application can be selected from any value between 90 ℃ and 200 ℃. Specifically, the heat treatment temperature includes, but is not limited to, 90 ℃, 100 ℃, 103 ℃, 105 ℃, 108 ℃, 110 ℃, 113 ℃, 115 ℃, 118 ℃, 120 ℃, 113 ℃, 115 ℃, 118 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃, or 200 ℃.

[0051] The temperature for graphitization can be selected from 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃, 1150 ℃, 1200 ℃, 1300 ℃, 1400 ℃, 1450 ℃, 1500 ℃, 1550 ℃, 1600 ℃, 1650 ℃ or 1700 ℃.

[0052] The preparation method provided in this application includes carbonization, activation, nitrogen doping, and graphitization. The activation treatment prepares porous carbon microspheres that help improve the specific surface area and adsorption performance of the material. Further nitrogen doping heat treatment is performed under catalytic conditions. The catalyst lowers the energy barrier for nitrogen atom insertion into the carbon framework, making it easier for nitrogen atoms to substitute or insert into the carbon network. This allows the heat treatment temperature to be between 90 °C and 200 °C, while also forming a stable nitrogen-doped carbon structure. Furthermore, metal elements are retained in the nitrogen-doped carbon structure to further catalyze graphitization, lowering the graphitization temperature to between 900 °C and 1700 °C.

[0053] In summary, the preparation method provided in this application has the advantages of low graphitization temperature, low energy consumption, and ease of large-scale production. Furthermore, the nitrogen-doped graphitized carbon microspheres prepared by this method have a high nitrogen doping content. Moreover, the nitrogen-doped graphitized carbon microspheres prepared by this method possess unique microstructure characteristics, high structural integrity, high nitrogen doping content, and large surface area. The nitrogen-doped graphitized carbon microspheres prepared in this application have broad application prospects in electrode materials, conductive materials, catalyst supports, and thermally conductive materials.

[0054] Understandably, in step S20 of this application, the carbon-containing polymer-based microspheres can be any carbonizable polymer-based microspheres. For example, the carbon-containing polymer-based microspheres include, but are not limited to, phenolic resin-based microspheres, polyvinylidene fluoride microspheres, polyfurfuryl alcohol-based microspheres, polystyrene-based microspheres, polyethylene-based microspheres, polyvinyl chloride microspheres, polymethacrylonitrile-based microspheres, polyacrylic anhydride-based microspheres, polyphenylene ether-based microspheres, polyetherketone-based microspheres, polyacrylonitrile-based microspheres, polysulfone-based microspheres, polyethersulfone-based microspheres, polyaryl ethersulfone-based microspheres, chloromethylated polysulfone-based microspheres, polyethylene terephthalate-based microspheres, polycarbonate-based microspheres, polyvinyl alcohol formal-based microspheres, polyvinyl alcohol butyral-based microspheres, and polymethyl methacrylate polymer-based microspheres.

[0055] However, considering the advantages of carbon-containing polymer-based microspheres, such as simple preparation process, low raw material cost, high chemical stability, high electrical conductivity, and high specific surface area, the carbon-containing polymer-based microspheres are preferably phenolic resin-based microspheres. The preparation steps of the phenolic resin-based microspheres include:

[0056] S10. The phenol source and aldehyde source are mixed in a solvent to prepare a mixture; after the mixture undergoes a polycondensation reaction, phenolic resin-based microspheres are prepared.

[0057] In one example, in step S10, the phenol source includes one or more of resorcinol, hydroquinone, catechol, phloroglucinol, phenol, m-aminophenol, and p-aminophenol.

[0058] In one example, in step S10, the aldehyde source includes one or more of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, salicylaldehyde, and aldehyde precursors. The aldehyde precursor includes hexamethylenetetramine. Hexamethylenetetramine decomposes under heating conditions or in an acidic environment to produce aldehyde compounds.

[0059] In one example, in step S10, when the aldehyde source is liquid, the mass-to-volume ratio of the phenol source to the aldehyde source is (1.5~2.7) g: (2.1~2.5) mL. Specifically, the mass-to-volume ratio of the phenolic source and the aldehyde source includes, but is not limited to, 1.5g:2.1 mL, 1.5g:2.2 mL, 1.5g:2.3 mL, 1.5g:2.32 mL, 1.5g:2.35 mL, 1.5g:2.4 mL, 1.5g:2.5 mL, 2.4g:2.2 mL, 2.48g:2 mL, 2.48g:2.1 mL, 2.48g:2.2 mL, 2.48g:2.3 mL, 2.5g:2.2 mL, 2.5g:2.21 mL, 2.5g:2.25 mL, 2.5g:2.3 mL, 2.5g:2.4 mL, 2.5g:2.5 mL, 2.7g:2.3 mL, 2.7g:2.2 mL, 2.7g:2.32 mL, or 2.7g:2.5 mL.

[0060] In another example, in step S10, when the aldehyde source is solid, the mass ratio of the phenol source to the aldehyde source is (3~3.3):(2~2.5). Specifically, the mass ratio of the phenol source to the aldehyde source includes, but is not limited to, 3.03:2, 3.05:2, 3.08:2, 3.1:2, 3.12:2, 3.12:2.5, 3.2:2.5, or 3.3:2.5.

[0061] In one example, in step S10, the solvent is deionized water.

[0062] To ensure thorough mixing of the phenolic and aldehyde sources and reduce the surface tension of the reaction system, the morphology and particle size distribution of the polymer-based microspheres are controlled. In one example, step S10 further includes a short-chain fatty alcohol in the mixture. The short-chain fatty alcohol contains 1 to 4 carbon atoms. Specifically, the short-chain fatty alcohol includes one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol.

[0063] More specifically, in step S10, the volume ratio of the short-chain fatty alcohol to deionized water is (10~70):(50~130). Specifically, the volume ratio of the short-chain fatty alcohol to deionized water includes, but is not limited to, 10:50, 10:80, 10:130, 20:120, 20:124, 20:130, 20:135, 67:82, 67.5:82, 68:82, 70:82, 70:82.5, 70:83, 70:85, 70:90, or 70:130.

[0064] To ensure sufficient crosslinking of the phenolic and aldehyde sources, and further increase the complexity and functionality of the polymer network, in one example, step S10 further includes an amine crosslinking agent in the mixture. For example, the amine crosslinking agent includes, but is not limited to, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, ethylenediamine, and hexamethylenediamine.

[0065] To accelerate the polycondensation reaction of phenolic and aldehyde sources and increase the polycondensation rate, in one example, step S10 further includes an alkaline catalyst in the mixture. For example, the alkaline catalyst includes, but is not limited to, ammonia, potassium carbonate, sodium carbonate, sodium hydroxide, and potassium hydroxide.

[0066] In one example, in step S10, the process parameters for the polycondensation reaction include a heating temperature of 40℃ to 95℃. Specifically, the temperatures for the polycondensation reaction include, but are not limited to, 40℃, 50℃, 55℃, 58℃, 60℃, 65℃, 68℃, 70℃, 75℃, 78℃, 80℃, 85℃, 88℃, 90℃, or 95℃. Further, the heating method is water bath heating. The polycondensation reaction time is 6 hours to 24 hours.

[0067] In one example, step S10, after the polycondensation reaction, also includes centrifugation, washing, and drying.

[0068] In one example, in step S20, the process parameters for the carbonization treatment include: a carbonization temperature of 500℃ to 900℃. Specifically, the carbonization temperature includes, but is not limited to, 500℃, 600℃, 610℃, 620℃, 650℃, 680℃, 700℃, 750℃, 800℃, 850℃, or 900℃. Specifically, the carbonization treatment time is 1 hour to 5 hours.

[0069] In one example, in step S30, the activation temperature is 800℃~1100℃. Specifically, the activation temperature includes, but is not limited to, 800℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 1000℃, 1050℃, 1080℃, or 1100℃.

[0070] In one example, in step S30, the activator includes one or more of liquid activators and gaseous activators.

[0071] In one example, the liquid activator includes one or more of deionized water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, and ammonia.

[0072] In one example, the gaseous activator includes one or more of carbon monoxide, carbon dioxide, and oxygen.

[0073] In one example, step S30, which involves activating the polymer-based carbon microspheres with an activator, includes the following specific steps:

[0074] After the carrier gas is bubbled through the liquid surfactant, it is then flowed through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and activation is performed at a temperature of 800 °C to 1100 °C. The flow rate of the carrier gas includes, but is not limited to, 100 mL / min, 150 mL / min, 200 mL / min, 210 mL / min, 220 mL / min, 240 mL / min, 260 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 350 mL / min, 380 mL / min, 400 mL / min, 500 mL / min, 600 mL / min, 700 mL / min, 800 mL / min, 900 mL / min, or 1000 mL / min. For example, the carrier gas includes, but is not limited to, nitrogen.

[0075] In another example, step S30, which involves activating the polymer-based carbon microspheres with an activator, includes the following specific steps:

[0076] The gaseous activator is flowed through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and activation is performed at a temperature of 800 °C to 1100 °C. The flow rate of the carrier gas includes, but is not limited to, 200 mL / min, 210 mL / min, 220 mL / min, 240 mL / min, 260 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 350 mL / min, 380 mL / min, 400 mL / min, 500 mL / min, 600 mL / min, 700 mL / min, 800 mL / min, 900 mL / min, or 1000 mL / min.

[0077] In one example, in step S40, the catalyst comprises one or more of the following: metal nitrates, metal halide salts, metal sulfates, metal acetates, metal ferrocene salts, metal ethylenediaminetetraacetate, molybdates, and boron trioxide. Specifically, the metal comprises one or more of the following: calcium, iron, cobalt, nickel, copper, zinc, manganese, molybdenum, platinum, chromium, tungsten, and lanthanum. More specifically, the catalyst comprises one or more of the following: calcium nitrate, ferric nitrate, cobalt chloride, ferric acetate, calcium chloride, ferrocene, ammonium molybdate, ferrous sulfate, boron trioxide, and manganese ethylenediaminetetraacetate.

[0078] In one example, in step S40, the nitrogen source is an organic amine compound. Examples of such organic amine compounds include, but are not limited to, urea, dicyandiamide, melamine, triazine, methyl ethyl ketone oxime, hydrazine hydrate, methylamine, ethylamine, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethanolamine, trimethylamine, triethylamine, aniline, p-phenylenediamine, m-phenylenediamine, p-aminobenzoic acid, imidazole, azobisisopropionitrile, azobisisobutyronitrile, azobenzene, p-methylaminoazobenzene, acetonitrile, butyronitrile, N-methylpyrrolidone, N-vinylpyrrolidone, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, N-methyl(meth)acrylamide, N-(3-dimethylaminopropyl)acrylamide, N-( 3-Dimethylaminopropyl)methacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, acrylamide, allylamine, diallylamine, triallylamine, isopropylacrylamide, acrylonitrile, benzonitrile, glutamic acid, arginine, histidine, tryptophan, aspartic acid, tryptophan, alanine, threonine, arginine, leucine, isoleucine, colic acid, histidine, glycine, lysine, serine, cystine, and polyethyleneimine.

[0079] In one example, in step S40, the solvent includes one or more of water, methanol, ethanol, isopropanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0080] In one example, in step S40, the mass ratio of the porous carbon microspheres to the catalyst is (0.2~0.4):(0.2~2.4). Specifically, the mass ratio of the porous carbon microspheres to the catalyst includes, but is not limited to, 0.2:0.4, 0.2:0.6, 0.2:0.8, 0.2:1.1, 0.2:2, 0.2:2.2, 0.2:1.5, 0.2:2, 0.2:2.4, 0.3:0.4, 0.3:0.6, 0.3:0.8, 0.3:1.1, 0.3:2, 0.3:2.2, 0.3:1.5, 0.3:2, 0.3:2.4, 0.4:0.4, 0.4:0.6, 0.4:0.8, 0.4:1.1, 0.4:2, 0.4:2.2, 0.4:1.5, 0.4:2, or 0.4:2.4.

[0081] When the nitrogen source is solid, in step S40, the mass ratio of the porous carbon microspheres to the nitrogen source is 0.3:(0.9~1.2). Specifically, the mass ratio of the porous carbon microspheres to the nitrogen source includes, but is not limited to, 0.3:0.9, 0.3:1, 0.3:1.1, or 0.3:1.2.

[0082] When the selected nitrogen source is liquid, in step S40, the mass-to-volume ratio of the porous carbon microspheres to the nitrogen source is 0.3 g: (1~1.5) mL. The mass-to-volume ratio of the porous carbon microspheres to the nitrogen source includes, but is not limited to, 0.3 g: 1 mL, 0.3 g: 1.2 mL, 0.3 g: 1.4 mL, or 0.3 g: 1.5 mL.

[0083] Understandably, various nitrogen sources can be used, meaning the nitrogen source can be in a solid or liquid state. For example, in step S40, the mass-to-volume ratio of the porous carbon microspheres, solid nitrogen source, and liquid nitrogen source is 0.3g:(0.25~0.35)g:(1~1.5)mL. Specifically, the mass-to-volume ratio of the porous carbon microspheres, solid nitrogen source, and liquid nitrogen source includes, but is not limited to, 0.3g:0.25g:1mL, 0.3g:0.3g:1mL, 0.3g:0.33g:1mL, or 0.3g:0.35g:1.5mL.

[0084] In one example, in step S40, the temperature of the heat treatment can be selected from any value between 90°C and 200°C. Specifically, the heat treatment temperature includes, but is not limited to, 90°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C.

[0085] In one example, step S50, after graphitization, further includes an acid washing step. Specifically, the acid includes one or more of hydrochloric acid, hydrobromic acid, hydroiodic acid, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, formic acid, acetic acid, citric acid, and oxalic acid. This acid washing step further removes the catalyst components carried in the nitrogen-doped graphitized carbon microspheres.

[0086] By defining specific process parameters for graphitization, the transformation of amorphous carbon into a graphite structure can be promoted, and the risk of material instability can be effectively prevented. In one example, in step S50, the specific process parameters for graphitization include: heating to 900℃~1700℃ at a heating rate of 2℃ / min~15℃ / min, and holding at that temperature for 4 h~16 h. The heating rate for graphitization includes, but is not limited to, 2℃ / min, 3℃ / min, 5℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, or 15℃ / min. The graphitization treatment temperature includes, but is not limited to, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1300℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, 1650℃, or 1700℃. The graphitization treatment holding temperature includes, but is not limited to, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, or 16h.

[0087] The porous carbon microspheres, catalyst, nitrogen source, and solvent are mixed and heat-treated under vacuum conditions to prepare the nitrogen-doped carbon microspheres; the catalyst includes one or more of metal salt catalysts and non-metal oxide catalysts, and the heat treatment temperature is 90 ℃~200 ℃;

[0088] The nitrogen-doped carbon microspheres were graphitized at 900 °C to 1700 °C under a protective atmosphere to prepare the nitrogen-doped graphitized carbon microspheres.

[0089] In one example, to improve the product quality of nitrogen-doped graphitized carbon microspheres, the process further includes repeating steps S40 and S50 with the nitrogen-doped graphitized carbon microspheres. Understandably, the prepared nitrogen-doped graphitized carbon microspheres are also porous carbon microspheres, and when participating in step S40, they can react as porous carbon microspheres.

[0090] A second aspect of this application provides nitrogen-doped graphitized carbon microspheres, prepared by any of the preparation methods described in the first aspect of this application.

[0091] In one example, the area ratio of the D peak to the G peak in the Raman spectrum of the nitrogen-doped graphitized carbon microspheres is 1.0 to 2.0. Specifically, the area ratio of the D peak to the G peak in the Raman spectrum of the nitrogen-doped graphitized carbon microspheres is 1.50 to 1.60. The nitrogen-doped graphitized carbon microspheres of this application exhibit graphene lattice changes caused by a high degree of defect or a large content of nitrogen atoms. That is, compared with undoped microspheres, the nitrogen-doped graphitized carbon microsphere material has lower crystallinity and increased disorder; this indicates that it has higher active sites, which is beneficial for catalytic applications.

[0092] In one example, the nitrogen-doped graphitized carbon microspheres have a BET specific surface area of ​​150 m². 2 / g~600 m 2 / g. The nitrogen-doped graphitized carbon microspheres prepared in this application have a high specific surface area, which has a positive impact on the performance of the material in catalysis, energy storage, adsorption and separation.

[0093] In one example, the nitrogen-doped graphitized carbon microspheres have a particle size of 0.1 μm to 10.0 μm. More specifically, the nitrogen-doped graphitized carbon microspheres have a particle size of 1 μm to 4 μm. More specifically, the nitrogen-doped graphitized carbon microspheres have a particle size of 1.5 μm to 2.0 μm.

[0094] In one example, the nitrogen content of the nitrogen-doped graphitized carbon microspheres is 5.5% to 16.5%. Specifically, the nitrogen content includes, but is not limited to, 6.5%, 7%, 7.5%, 7.6%, 7.8%, 7.9%, 8%, 8.2%, 8.5%, 9%, 9.5%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, or 16.5%. The nitrogen-doped graphitized carbon microspheres provided in this application have a high nitrogen content, resulting in more active sites. When applied to catalytic reactions, they can promote chemical reactions and improve catalytic efficiency. Simultaneously, they can also enhance adsorption performance, increase material stability, and improve electrochemical performance.

[0095] In one example, the nitrogen-doped graphitized carbon microspheres are nitrogen-doped graphitized carbon microspheres.

[0096] A third aspect of this application provides the application of nitrogen-doped graphitized carbon microspheres as described in any of the second aspects of this application in electrode materials, conductive materials, catalyst supports, and thermally conductive materials.

[0097] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0098] Example 1

[0099] (1) Weigh 2.48 g resorcinol (phenol source), 67.5 mL ethanol (short-chain fatty alcohol), 82 mL deionized water (solvent), and 2.2 mL formaldehyde (aldehyde source) and mix and stir for 30 min; add 0.51 mL ammonia water and stir at 50℃ for 6 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60℃ for 24 h to prepare carbon-containing polymer-based microspheres.

[0100] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5°C / min under nitrogen protection, carbonized at 700°C for 2 h, cooled and removed to obtain polymer-based carbon microspheres.

[0101] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through deionized water (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5℃ / min. After activation at 900℃ for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0102] (4) Dissolve 0.80 g cobalt chloride (catalyst) and 1.20 g ferric acetate (catalyst) in 80 mL of water (solvent), then add 0.30 g porous carbon microspheres under stirring, ultrasonically disperse for 10 min, add 1 mL ethylenediamine (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to a Teflon autoclave, treat at 120 ℃ for 12 h, after cooling to room temperature, filter, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer the nitrogen-doped carbon microspheres to a tube furnace, purge with nitrogen, heat at a rate of 10 ℃ / min, hold at 1400 ℃ for 16 h, cool and remove, then treat with 1.50 mol / L sulfuric acid, filter, wash with water, and dry at 60 ℃ for 12 h.

[0103] (5) Repeat step (4) twice to obtain nitrogen-doped graphitized carbon microspheres.

[0104] Example 2

[0105] (1) Weigh 3.03 g resorcinol (phenol source) and 70 mL deionized water (solvent) to dissolve it. Mix 2.00 g hexamethylenetetramine (aldehyde source) and stir for 30 min. Heat to 40 ℃ and stir for 48 h. After centrifugation, washing with water and anhydrous ethanol, dry at 60 ℃ for 24 h to prepare carbon-containing polymer-based microspheres.

[0106] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5 °C / min under nitrogen protection, carbonized at 600 °C for 3 h, and then cooled and removed to obtain polymer-based carbon microspheres.

[0107] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through a 10 wt% ethanol aqueous solution (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5℃ / min. After activation at 900℃ for 3 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0108] (4) Dissolve 0.50 g calcium chloride (catalyst) and 1.80 g ferrocene (catalyst) in 40 mL water (solvent) and 40 mL N,N-dimethylformamide (solvent). Then add 0.30 g porous carbon microspheres under stirring, disperse ultrasonically for 10 min, add 1.0 g p-phenylenediamine (nitrogen source) and 0.10 g acrylamide (nitrogen source), stir for 10 min, then vacuum three times (10 min each time, 1 h apart), transfer to Teflon autoclave, treat at 120 ℃ for 12 h, cool to room temperature, filter, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer nitrogen-doped carbon microspheres to tube furnace, purge with nitrogen, heat at a rate of 10 ℃ / min, hold at 900 ℃ for 24 h, cool and remove, treat with 3 mol / L hydrochloric acid, filter, wash with water, dry at 60 ℃ for 12 h.

[0109] (5) Repeat step (4) three times to obtain nitrogen-doped graphitized carbon microspheres.

[0110] Example 3

[0111] (1) Weigh 1.82 g hydroquinone (phenol source), 1.30 g resorcinol (phenol source), 10 mL ethanol (short chain fatty alcohol), and 50 mL deionized water (solvent) and stir for 30 min; add 2.50 g hexamethylenetetramine (aldehyde source) and 30 mL deionized water (solvent) solution and stir, keep warm at 95℃ for 3 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 ℃ for 24 h to prepare carbon-containing polymer-based microspheres.

[0112] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5 °C / min under nitrogen protection, carbonized at 600 °C for 3 h, and then cooled and removed to obtain polymer-based carbon microspheres.

[0113] (3) The polymer-based carbon microspheres were placed in a tube furnace and a mixture of nitrogen and carbon dioxide gas (a gaseous activator with a volume ratio of 1:1) was passed through the gas. The mixture was bubbled through deionized water (a liquid activator) at a flow rate of 200 mL / min and heated at a rate of 5 °C / min. After activation at 900 °C for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0114] (4) Dissolve 1.00 g ammonium molybdate (catalyst) and 0.10 g ferrous sulfate (catalyst) in 75 mL water (solvent) and 5 mL methanol (solvent). Then add 0.30 g porous carbon microspheres under stirring, disperse ultrasonically for 10 min, add 1.5 mL diallylamine (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to Teflon autoclave, treat at 120 ℃ for 12 h, filter after cooling to room temperature, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer nitrogen-doped carbon microspheres to tube furnace, pass argon gas, heat at a rate of 10 ℃ / min, hold at 1500 ℃ for 12 h, cool and take out, treat with 4 mol / L acetic acid, filter, wash with water, and dry at 80 ℃ for 12 h.

[0115] (5) Repeat step (4) once to obtain nitrogen-doped graphitized carbon microspheres.

[0116] Example 4

[0117] (1) Weigh 2.50 g resorcinol (phenol source), 70 mL ethanol (short chain fatty alcohol), 82.5 mL deionized water (solvent), and 2.21 mL formaldehyde (aldehyde source) and stir for 30 min; add ammonia water (alkaline catalyst) solution and stir, keep warm at 50 ℃ for 8 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 ℃ for 24 h to prepare carbon-containing polymer-based microspheres.

[0118] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5 °C / min under nitrogen protection, carbonized at 600 °C for 3 h, and then cooled and removed to obtain polymer-based carbon microspheres.

[0119] (3) The polymer-based carbon microspheres were placed in a tube furnace and a mixture of nitrogen and carbon monoxide (a gaseous activator with a volume ratio of 3:1) was passed through. The gas flow rate was 200 mL / min, and the temperature was increased at a rate of 5 °C / min. After activation at 900 °C for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0120] (4) Dissolve 1.00 g ammonium molybdate (catalyst) and 0.10 g ferrous sulfate (catalyst) in 75 mL water (solvent) and 5 mL methanol (solvent). Then add 0.30 g porous carbon microspheres under stirring, disperse ultrasonically for 10 min, add 1 mL hydrazine hydrate (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to Teflon autoclave, treat at 120 ℃ for 12 h, filter after cooling to room temperature, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer nitrogen-doped carbon microspheres to tube furnace, pass argon gas, heat at a rate of 10 ℃ / min, hold at 1100 ℃ for 15 h, cool and take out, treat with 1.5 mol / L nitric acid, filter, wash with water, and dry at 80 ℃ for 12 h.

[0121] (5) Repeat step (4) twice to obtain nitrogen-doped graphitized carbon microspheres.

[0122] Example 5

[0123] (1) Weigh 1.50 g resorcinol (phenol source), 1.20 g m-phenylenediamine (amine crosslinking agent), 20 mL isopropanol (short-chain fatty alcohol), 124 mL deionized water (solvent), and 2.32 mL formaldehyde (aldehyde source) and stir for 30 min; add ammonia water (alkaline catalyst) solution and stir, keep warm at 70 ℃ for 9 h; after centrifugation, washing with water and anhydrous ethanol, dry in a forced-air dryer at 60 ℃ for 24 h to prepare carbon-containing polymer-based microspheres.

[0124] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5 °C / min under nitrogen protection, carbonized at 600 °C for 3 h, and then cooled and removed to obtain polymer-based carbon microspheres.

[0125] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The gas was bubbled through an ammonia aqueous solution (5 wt%, liquid activator) at a flow rate of 200 mL / min. The temperature was increased at a rate of 5 °C / min. After activation at 900 °C for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0126] (4) Dissolve 1.00 g boron trioxide (catalyst) and 0.50 g manganese ethylenediaminetetraacetate (catalyst) in 75 mL water (solvent) and 5 mL methanol (solvent). Then add 0.30 g porous carbon microspheres under stirring, disperse ultrasonically for 10 min, add 1 mL polyethyleneimine (nitrogen source) and 0.3 g glutamic acid (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to Teflon autoclave, treat at 120 ℃ for 12 h, filter after cooling to room temperature, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer nitrogen-doped carbon microspheres to tube furnace, pass argon gas, heat at a rate of 10 ℃ / min, hold at 1700 ℃ for 4 h, cool and take out, treat with 1.5 mol / L hydrofluoric acid, filter, wash with water, and dry at 80 ℃ for 12 h.

[0127] (5) Repeat step (4) twice to obtain nitrogen-doped graphitized carbon microspheres.

[0128] Comparative Example 1

[0129] (1) Weigh 2.48 g resorcinol (phenol source), 67.5 mL ethanol (short chain fatty alcohol), 82 mL deionized water (solvent), and 2.2 mL formaldehyde (aldehyde source) and mix and stir for 30 min; add 0.51 mL ammonia water and stir at 50 °C for 6 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 °C for 24 h to prepare carbon-containing polymer-based microspheres.

[0130] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5 °C / min under nitrogen protection, and carbonized at 700 °C for 2 h before being cooled and removed to obtain polymer-based carbon microspheres.

[0131] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through deionized water (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5 °C / min. After activation at 900 °C for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0132] (4) Dissolve 0.80 g cobalt chloride (catalyst) and 1.20 g ferric acetate (catalyst) in 80 mL of water (solvent), then add 0.30 g porous carbon microspheres under stirring, ultrasonically disperse for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to a Teflon autoclave, treat at 120 ℃ for 12 h, filter after cooling to room temperature, dry at 60 ℃ for 12 h, transfer to a tube furnace, purge with nitrogen, heat at a rate of 10 ℃ / min, hold at 1400 ℃ for 16 h, cool and remove, then treat with 1.50 mol / L sulfuric acid, filter, wash with water, and dry at 60 ℃ for 12 h.

[0133] (5) Repeat step (4) twice to obtain graphitized carbon microspheres.

[0134] Comparative Example 2

[0135] (1) Weigh 2.48 g resorcinol (phenol source), 67.5 mL ethanol (short-chain fatty alcohol), 82 mL deionized water (solvent), and 2.2 mL formaldehyde (aldehyde source) and mix and stir for 30 min; add 0.51 mL ammonia water and stir at 50 °C for 6 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 °C for 24 h to prepare polymer-based microspheres.

[0136] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5°C / min under nitrogen protection, carbonized at 700°C for 2 h, cooled and removed to obtain polymer-based carbon microspheres.

[0137] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through deionized water (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5 °C / min. After activation at 900 °C for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0138] Comparative Example 3

[0139] (1) Weigh 2.48 g resorcinol (phenol source), 67.5 mL ethanol (short-chain fatty alcohol), 82 mL deionized water (solvent), and 2.2 mL formaldehyde (aldehyde source) and mix and stir for 30 min; add 0.51 mL ammonia water and stir at 50 °C for 6 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 °C for 24 h to prepare polymer-based microspheres.

[0140] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5°C / min under nitrogen protection, carbonized at 700°C for 2 h, cooled and removed to obtain polymer-based carbon microspheres.

[0141] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through deionized water (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5℃ / min. After activation at 900℃ for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0142] (4) Dissolve 0.80 g cobalt chloride (catalyst) and 1.20 g ferric acetate (catalyst) in 80 mL of water (solvent), then add 0.30 g porous carbon microspheres under stirring, ultrasonically disperse for 10 min, add 1 mL ethylenediamine (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to a Teflon autoclave, treat at 120 ℃ for 12 h, after cooling to room temperature, filter, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer the nitrogen-doped carbon microspheres to a tube furnace, purge with nitrogen, heat at a rate of 10 ℃ / min, hold at 700 ℃ for 16 h, cool and remove, then treat with 1.50 mol / L sulfuric acid, filter, wash with water, and dry at 60 ℃ for 12 h.

[0143] (5) Repeat step (4) twice to obtain nitrogen-doped carbon microspheres. Due to the low graphitization temperature in Comparative Example 3, graphitized carbon microspheres were not obtained in the product.

[0144] Comparative Example 4

[0145] (1) Weigh 2.48 g resorcinol (phenol source), 67.5 mL ethanol (short-chain fatty alcohol), 82 mL deionized water (solvent), and 2.2 mL formaldehyde (aldehyde source) and mix and stir for 30 min; add 0.51 mL ammonia water and stir at 50 °C for 6 h; after centrifugation, washing with water and anhydrous ethanol, dry at 60 °C for 24 h to prepare polymer-based microspheres.

[0146] (2) The polymer-based microspheres were placed in a tube furnace, purged with nitrogen three times, heated at a rate of 5°C / min under nitrogen protection, carbonized at 700°C for 2 h, cooled and removed to obtain polymer-based carbon microspheres.

[0147] (3) The polymer-based carbon microspheres were placed in a tube furnace and nitrogen gas was introduced. The nitrogen gas was bubbled through deionized water (liquid activator) at a flow rate of 400 mL / min. The temperature was increased at a rate of 5℃ / min. After activation at 900℃ for 2 h, the microspheres were cooled and removed to obtain porous carbon microspheres.

[0148] (4) Dissolve 0.30 g of porous carbon microspheres in 80 mL of water (solvent), disperse ultrasonically for 10 min, add 1 mL of ethylenediamine (nitrogen source), stir for 10 min, then vacuum twice (10 min each time, 1 h apart), transfer to a Teflon autoclave, treat at 120 ℃ for 12 h, filter after cooling to room temperature, dry at 60 ℃ for 12 h to prepare nitrogen-doped carbon microspheres; transfer nitrogen-doped carbon microspheres to a tube furnace, purge with nitrogen, heat at a rate of 10 ℃ / min, hold at 1400 ℃ for 16 h, cool and remove, then treat with 1.50 mol / L sulfuric acid, filter, wash with water, and dry at 60 ℃ for 12 h.

[0149] (5) Repeat step (4) twice to obtain nitrogen-doped carbon microspheres. Since no catalyst was used in Comparative Example 4, graphitized carbon microspheres were not obtained from the product of Comparative Example 4 at the same graphitization temperature as in Example 1.

[0150] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were subjected to the following tests:

[0151] (1) Characterization by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (XEDS)

[0152] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were characterized by scanning electron microscopy (SEM). The method was as follows: a small amount of nitrogen-doped graphitized carbon microsphere powder was ultrasonically dispersed in anhydrous ethanol, then dropped onto a silicon wafer, dried, and sputtered with gold. The morphology and structure of the prepared microspheres were then observed using a scanning electron microscope. The corresponding results are as follows: Figure 1 As shown. Simultaneously, its XEDS data was tested, and the corresponding test results are as follows. Figure 2 As shown.

[0153] from Figure 1 SEM images of nitrogen-doped graphitized carbon microspheres clearly show the three-dimensional structure of graphene, with good microsphere dispersion and a particle size of approximately 1.5 μm to 2.0 μm. Figure 2 The energy dispersive spectroscopy (EDS) data shows that the nitrogen-doped graphitized carbon microspheres are mainly composed of C and N elements, with a carbon atom content of 92.2% and a N atom content of 7.8%. The particle size distribution and elemental content of other embodiments and comparative examples are shown in Table 1 below.

[0154] (2) Transmission electron microscopy (TEM) characterization

[0155] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were characterized by transmission electron microscopy (TEM). The method involved taking a small amount of nitrogen-doped graphitized carbon microsphere powder, ultrasonically dispersing it in anhydrous ethanol, then dropping it onto a copper grid and drying it. The morphology and structure of the prepared microspheres were then observed using a transmission electron microscope. Figure 3 As shown. From Figure 3 TEM images of nitrogen-doped graphitized carbon microspheres clearly show the unique rolled structure of graphene.

[0156] (3) X-ray diffraction (XRD) characterization

[0157] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were characterized by X-ray diffraction (XRD), and the XRD pattern is shown below. Figure 4 As shown in the XRD pattern, the porous carbon microspheres (Comparative Example 2) exhibit a distinct amorphous carbon structure with 2θ between 15 and 30°; the graphitized carbon microspheres (Comparative Example 1) show obvious graphene characteristic peaks; after nitrogen doping, the graphene characteristic peaks of the nitrogen-doped graphitized carbon microspheres (Example 1) are weakened, indicating that nitrogen doping reduces the crystallinity of the graphitized structure of the microspheres.

[0158] (4) Raman characterization

[0159] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were characterized by Raman spectroscopy. Figure 5 Raman spectra of porous carbon microspheres (Comparative Example 2), graphitized carbon microspheres (Comparative Example 1), and nitrogen-doped graphitized carbon microspheres (Example 1) are shown. The study indicates that the ratio between the D peak and the G peak (Ig) can be used to determine the Raman spectra of these microspheres. D / I G ( ) is used to characterize the degree of defects in graphene. Figure 5 The Raman spectrum of the mesoporous carbon microspheres (Comparative Example 2) shows broad and weak peaks, typical of amorphous carbon; the graphitized carbon microspheres (Comparative Example 1) have peaks at ~1340 cm⁻¹. -1 The D peak and 1570 cm -1 The G peak is significantly enhanced, and the intensity of its 2D peak is also very significant (~2680 cm⁻¹). -1 ), I D / I G The peak area ratio is approximately 0.772, indicating relatively few defect structures in graphene. In contrast, nitrogen-doped graphitized carbon microspheres (Example 1) are located at ~1342 cm⁻¹. -1 The D peak and 1572 cm -1 The G peak becomes significantly wider and the peak intensity decreases, while the I peak becomes significantly lower. D / I G The peak area ratio is approximately 1.540, indicating a high degree of defect in the graphene or lattice changes caused by a large amount of nitrogen atom doping. In other words, compared to undoped graphene, the nitrogen-doped material has lower crystallinity and increased disorder. Other embodiments and comparative examples I... D / I G The peak area ratios are shown in Table 1 below.

[0160] (5) Characterization of nitrogen adsorption-desorption

[0161] The nitrogen-doped graphitized carbon microspheres prepared in Example 1 were characterized by nitrogen adsorption-desorption, and the nitrogen adsorption-desorption curves are shown below. Figure 6 As shown, the calculated BET specific surface area of ​​nitrogen-doped graphitized carbon microspheres is 316 m². 2 The surface area / g indicates that the nitrogen-doped graphitized carbon microspheres prepared in this application have a high specific surface area. The specific surface areas of other embodiments and comparative examples are shown in Table 1 below.

[0162] Table 1

[0163]

[0164] As shown in Table 1, the nitrogen-doped graphitized carbon microspheres prepared in Examples 1-5 of this application have a particle size distribution between 0.1 μm and 10 μm, and a nitrogen content between 5.6% and 16.2%. The higher nitrogen content indicates that they possess more active sites. The nitrogen-doped graphitized carbon microspheres prepared in Examples 1-5 have I... D / I G The peak area ratio is between 1.04 and 1.92, indicating that the nitrogen-doped graphitized carbon microspheres prepared in Examples 1-5 of this application have low crystallinity and increased disorder, resulting in higher active sites, which is beneficial for catalytic applications. Furthermore, the specific surface area of ​​the nitrogen-doped graphitized carbon microspheres prepared in Examples 1-5 is 268 m². 2 / g~590m 2 Between / g, its high specific surface area has a positive impact on the performance of the material in catalysis, energy storage, adsorption and separation.

[0165] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0166] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing nitrogen-doped graphitized carbon microspheres, characterized in that, Includes the following steps: Polymer-based carbon microspheres are prepared by carbonizing carbon-containing polymer-based microspheres. Porous carbon microspheres are prepared by activating the polymer-based carbon microspheres with an activating agent; the activating agent includes one or more of liquid activators and gaseous activators, the liquid activator includes one or more of deionized water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol and ammonia; the gaseous activator includes one or more of carbon monoxide, carbon dioxide and oxygen. The porous carbon microspheres, catalyst, nitrogen source, and solvent are mixed and heat-treated under vacuum to prepare nitrogen-doped carbon microspheres; the heat treatment temperature is 90 ℃~200 ℃; the catalyst includes one or more of metal nitrates, metal halide salts, metal sulfates, metal acetates, metal dicerocene salts, metal ethylenediaminetetraacetic acid salts, molybdates, and boron trioxide; the nitrogen source is an organic amine compound; when the nitrogen source is solid, the mass ratio of the porous carbon microspheres to the nitrogen source is 0.3:(0.9~1.2); when the nitrogen source is liquid, the mass-volume ratio of the porous carbon microspheres to the nitrogen source is 0.3g:(1~1.5)mL; The nitrogen-doped carbon microspheres were graphitized at 900 °C to 1700 °C under a protective atmosphere to prepare the nitrogen-doped graphitized carbon microspheres. The step of activating the polymer-based carbon microspheres with an activator includes: bubbling a carrier gas through the liquid activator, then flowing the carrier gas through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and performing activation treatment at a temperature of 800 ℃ to 1100 ℃; or, flowing the gaseous activator through the polymer-based carbon microspheres at a flow rate of 100 mL / min to 1000 mL / min, and performing activation treatment at a temperature of 800 ℃ to 1100 ℃.

2. The method for preparing nitrogen-doped graphitized carbon microspheres according to claim 1, characterized in that, The specific process parameters for the graphitization treatment include: heating to 900 ℃ to 1700 ℃ at a heating rate of 2 ℃ / min to 15 ℃ / min, and holding at that temperature for 4 h to 16 h.

3. The method for preparing nitrogen-doped graphitized carbon microspheres according to claim 1, characterized in that, The mass ratio of the porous carbon microspheres to the catalyst is (0.2~0.4):(0.2~2.4).

4. The method for preparing nitrogen-doped graphitized carbon microspheres according to claim 1, characterized in that, The process parameters for the carbonization treatment include: carbonization temperature of 500 ℃ to 900 ℃.

5. The method for preparing nitrogen-doped graphitized carbon microspheres according to any one of claims 1 to 4, characterized in that, The carbon-containing polymer-based microspheres are phenolic resin-based microspheres, and the preparation steps of the phenolic resin-based microspheres include: The phenolic source and aldehyde source are mixed in a solvent to prepare a mixture; after the mixture undergoes a polycondensation reaction, phenolic resin-based microspheres are prepared.

6. The method for preparing nitrogen-doped graphitized carbon microspheres according to claim 5, characterized in that, The phenol source includes one or more of resorcinol, hydroquinone, catechol, phloroglucinol, phenol, m-aminophenol, and p-aminophenol.

7. The method for preparing nitrogen-doped graphitized carbon microspheres according to claim 5, characterized in that, The aldehyde source includes one or more of formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, salicylaldehyde, and aldehyde precursors, wherein the aldehyde precursor includes hexamethylenetetramine.

8. A nitrogen-doped graphitized carbon microsphere, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The nitrogen-doped graphitized carbon microspheres according to claim 8, characterized in that, The nitrogen-doped graphitized carbon microspheres have one or more of the following characteristics: (1) The area ratio of the Raman spectrum D peak intensity to the Raman spectrum G peak intensity of the nitrogen-doped graphitized carbon microspheres is 1.0~2.0; (2) The BET specific surface area of ​​the nitrogen-doped graphitized carbon microspheres is 150 m². 2 / g~600 m 2 / g; (3) The particle size of the nitrogen-doped graphitized carbon microspheres is 0.1 μm to 10.0 μm; (4) The nitrogen content of the nitrogen-doped graphitized carbon microspheres is 5.5% to 16.5%.

10. The use of nitrogen-doped graphitized carbon microspheres according to any one of claims 8 or 9 in electrode materials, conductive materials, catalyst supports, and thermally conductive materials.

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