Nitrogen-doped highly-graphitized mesoporous carbon material as well as preparation method and application thereof

Abstract

The invention discloses a nitrogen-doped highly-graphitized mesoporous carbon material and a preparation method and application thereof, and relates to the technical field of hydrogen fuel cell catalysis, the nitrogen-doped highly-graphitized mesoporous carbon material comprises a material prepared from ZnxZn1-x (OH) 2-MOF and metal lithium, and X is more than or equal to 0.1 and less than or equal to 0.5. The high reaction enthalpy of formation of a lithium fluoride material is utilized, a large amount of heat can be released when metal lithium reacts with fluoride, a reaction system is rapidly heated, the contact reaction interface of molten lithium and fluorine-containing organic matter is increased, the reaction is extremely rapid, the generated high temperature is sufficient to directly pyrolyze and carbonize the carbon-containing organic matter, and a highly graphitized carbon material matrix is formed; a large amount of gas is generated in the carbon-containing organic matter pyrolysis process, a carbon material matrix is promoted to form a large number of pores, and the purpose of improving the comprehensive performance of the carbon material is achieved.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen fuel cell catalysis technology, and in particular to a nitrogen-doped highly graphitized mesoporous carbon material and a preparation method and application thereof. Background Art

[0002] In the field of hydrogen fuel cells, high-performance electrocatalysts have long been a research focus. As a key material in electrocatalysts, carbon supports significantly influence their performance. Commonly used carbon supports for hydrogen fuel cell catalysts include acetylene black, Vulcan XC-72R, Ketjen Black EC300J, Ketjen Black EC600JD, Ensaco 350G, Black Pearls 2000, and PRINTEX XE2-B. The aforementioned conventional carbon supports are limited by their low specific surface area (e.g., acetylene black, Vulcan XC-72R). Platinum nanoparticles can mostly only be loaded on the surface of the carbon supports, where they are easily covered and poisoned by ionomers, and the platinum nanoparticles are more likely to agglomerate. Porous carbon supports with higher specific surface areas (e.g., ketjen black EC300J, ketjen black EC600JD, Ensaco 350G, black pearls 2000, PRINTEX XE2-B) have tortuous, disconnected pore structures and poor pore size distribution, which hinders the mass transfer process and makes it difficult for some platinum particles to function. Mesoporous carbon materials have the advantages of high specific surface area, excellent electrical conductivity, gas-liquid permeability, and adjustable pore structure, and have great application prospects in the field of hydrogen fuel cell catalyst supports. Replacing conventional carbon supports with mesoporous carbon will effectively improve the performance of the catalyst. According to Toyota's public information, the cathode catalyst for the second-generation Mirai fuel cell utilizes a mesoporous carbon support. Approximately 80% of the platinum particles are located within the carbon support's pores, significantly reducing poisoning caused by direct contact between the platinum particles and the ionomer. Furthermore, the interconnected mesopores facilitate material transport, ensuring more uniform dispersion of the platinum particles. The confined nature of the pores also reduces particle agglomeration, thereby improving lifespan. However, the mesoporous carbon preparation process used by Toyota is demanding, and its precursor, silver acetylene, is prone to uncontrolled explosive reactions, resulting in high technical barriers to mass production. Toyo Tanso's MgO-templated mesoporous carbon (MH-18) demonstrates excellent resistance to poisoning and high activity as a hydrogen fuel cell cathode catalyst support. Pajarito Powder's ECS series of mesoporous carbons, produced using a silicon-based template method, also exhibit interconnected mesoporous structures, resulting in higher catalyst activity and superior oxygen transport performance. The possible shortcoming of the mesoporous carbon that has been mass-produced by the template method is that it takes a long time to use acid / alkali solution to etch away the template wrapped in the carbon material matrix, while generating a large amount of acid / alkali waste liquid and washing wastewater. If the template is not etched cleanly and remains in the mesoporous carbon matrix, it may also affect the performance of the catalyst. Due to the limitation of the single template size, the mesopore diameter of the carbon material is difficult to control.The corrosion resistance of mesoporous carbon prepared by the template method is further enhanced after high-temperature graphitization treatment, but this sacrifices some specific surface area. Furthermore, long-term high-temperature heat treatment means high energy consumption.

[0003] The performance of hydrogen fuel cells is highly dependent on the microstructure of the catalyst layer. The catalyst layer consists of a network of platinum particles supported by carbon particles mixed with an ionomer. Optimal ionomer coverage on the catalyst is crucial for providing proton conduction pathways while minimizing oxygen transport resistance. For example, Sebastian Ott reported in "Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells" that a nitrogen-modified commercial carbon support was developed. The electrostatic interaction between the nitrogen-containing groups and the ionomer improves the distribution of the ionomer on the carbon support surface, ultimately achieving high fuel cell power density. Furthermore, the strong interaction between the nitrogen-containing groups and the platinum nanoparticles firmly anchors the Pt nanoparticles to the carbon support, slowing their dissolution, migration, agglomeration, and shedding during electrochemical cycling and enhancing the stability of the catalyst system. The presence of nitrogen-containing groups can modify the electronic structure of nearby active components, enhancing the catalytic activity of the catalyst system. They can also serve as nucleation sites during catalyst preparation, promoting the dispersion of Pt nanoparticles. Therefore, the introduction of nitrogen into carbon materials can improve the overall level of fuel cell catalysts in many aspects.

[0004] However, there is no mesoporous carbon material that has a large specific surface area, adjustable mesopore size, high degree of graphitization, and nitrogen modification, or it requires a complex synthesis route to be produced. Summary of the Invention

[0005] The purpose of the present invention is to provide a nitrogen-doped highly graphitized mesoporous carbon material and its preparation method and application, so as to solve the problems of complex preparation process and low catalytic performance of carbon carrier materials in the prior art.

[0006] First, the embodiment of the present invention provides a nitrogen-doped highly graphitized mesoporous carbon material, comprising Zn x Zn 1-x A material prepared from (OH)2-MOF and metallic lithium, wherein 0.1≤X≤0.5.

[0007] As an optional embodiment of the present invention, the Zn x Zn 1-x(OH)2-MOF includes materials prepared from metal organic framework material Zn-MOF and alkali metal hydroxide; The metal organic framework material Zn-MOF includes a material prepared from zinc salt, N,N-dimethylformamide, an organic ligand and polyvinyl pyrrolidone.

[0008] As an optional embodiment of the present invention, the organic ligand includes at least one of 2-fluoroterephthalic acid, 3-fluorophthalic acid, 4-fluoroisophthalic acid, and 4-fluorophthalic acid; The zinc salt includes at least one of zinc nitrate, zinc sulfate, zinc chloride and zinc acetate.

[0009] As an optional embodiment of the present invention, the molar ratio of the zinc salt to the organic ligand is 1:0.2~2; The molar ratio of the zinc salt to N,N-dimethylformamide is 1: 120-240; The molar ratio of the zinc salt to polyvinyl pyrrolidone is 1: 30-70; The molecular weight of the polyvinyl pyrrolidone is ≤100,000.

[0010] Secondly, an embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: S1: zinc salt, N,N-dimethylformamide, organic ligand, and polyvinyl pyrrolidone are placed in a high-pressure reactor to prepare a metal-organic framework material Zn-MOF, and the metal-organic framework material Zn-MOF is rinsed and dried for later use; S2: Disperse the dried metal organic framework material Zn-MOF into anhydrous ethanol, then dropwise add an ethanol solution containing alkali metal hydroxide and stir, filter and dry in turn to obtain the standby powder Zn x Zn 1-x (OH)2-MOF; S3: Powder Zn x Zn 1-x (OH)2-MOF and metallic lithium powder are heat-treated under an inert atmosphere to obtain a coarse carbon material powder; S4: Grinding and crushing the coarse carbon material powder into fine powder; S5: putting the fine powder into an acid washing solution for pickling, and rinsing with deionized water until the conductivity of the filtrate is less than 200 μs / cm to obtain a fine carbon material; S6: vacuum drying the carbon material fine material to obtain a mesoporous carbon material.

[0011] As an optional embodiment of the present invention, the reaction temperature for preparing the metal organic framework material Zn-MOF in S1 is 150-180° C., and the reaction time is 5-10 hours.

[0012] As an optional embodiment of the present invention, the step of adding the ethanol solution containing an alkali metal hydroxide dropwise with stirring in S2 includes: using five equally spaced pump tubes to simultaneously add the ethanol solution containing an alkali metal hydroxide dropwise through a peristaltic pump, and assisting stirring during the dropwise addition process; and continuing stirring for 25 to 35 minutes after the solution is added dropwise; The dripping rate of a single pump tube is 5~20mL / min, and the dripping time is 30~60 minutes.

[0013] As an optional embodiment of the present invention, the alkali metal hydroxide includes at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide, and the concentration of the ethanol solution containing the alkali metal hydroxide is 0.2-1 mol / L.

[0014] As an optional embodiment of the present invention, the heat treatment temperature in S3 is 200-300°C, the heat treatment time is 30-60 minutes, the heating rate is 1-5°C / min, and the inert atmosphere includes argon and / or nitrogen.

[0015] Finally, an embodiment of the present invention further provides an application of a nitrogen-doped highly graphitized mesoporous carbon material, including applying the mesoporous carbon material to a hydrogen fuel cell.

[0016] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects: 1. This embodiment utilizes the high reaction enthalpy of lithium fluoride (617 kJ / mol). The reaction between metallic lithium and fluoride releases a large amount of heat, causing the reaction system to heat up rapidly. The molten lithium (melting point 180.5°C) interacts with the fluorinated organic matter at a greater number of contact interfaces, resulting in an extremely rapid reaction. The resulting high temperature is sufficient to directly pyrolyze and carbonize the carbon-containing organic matter, forming a highly graphitized carbon matrix.

[0017] During the pyrolysis of carbon-containing organic matter, a large amount of gases (such as CO, CO2, H2O, NO, NO2, CH4, H2, etc.) are generated. The release of these gases causes a large number of pores to form in the carbon material matrix. x Zn 1-x The zinc in the (OH)2-MOF is oxidized and reduced during the carbonization process, evaporating in large quantities, leaving behind natural pores. This mesoporous carbon material combines the advantages of high specific surface area and high degree of graphitization.

[0018] 2. The preparation method of the mesoporous carbon material provided by the embodiment of the present invention is simple in process and the preparation time is shortened by half compared with the traditional preparation method. The high-temperature pyrolysis treatment can realize the melting characteristics of the alkali metal salt, protect the graphitized structure during the pyrolysis process, promote the increase of graphitization degree and the formation of micropore / mesoporous structure, and the metal nanoparticles will leave natural pores after evaporation, avoiding the need to spend a long time to etch the zinc inside the carbon material matrix. Since it is a direct mixing of solid powders, the lithium oxide and lithium fluoride generated by the lithium powder reaction are mostly present on the surface of the carbon material and can be easily washed away by acid. Due to the short reaction time, a large amount of pore structure and nitrogen elements will be retained; by controlling the alkaline solution addition process to control the size of the Zn(OH)2 particles, the mesopore size distribution of the carbon material can be adjusted. The prepared carbon material can simultaneously take into account the advantages of high specific surface area, adjustable mesopore size, high degree of graphitization, nitrogen modification, etc., and its application in fuel cells can greatly improve the activity and durability of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is the SEM test image of NMC-1 in Example 1 of the present invention, wherein Figure 1 The magnification of a is less than Figure 1 b magnification; Figure 2 This is the TEM test image of NMC-1 in Example 1 of the present invention, where Figure 2 The magnification of a is less than Figure 2 The magnification of b, Figure 2 The magnification of c is less than Figure 2 The magnification of b, Figure 2 The magnification of d is less than Figure 2 c magnification; Figure 3 This is the TG test graph of NMC-1 in Example 1 of the present invention; Figure 4 The XRD test patterns of NMC-1 and commercial mesoporous carbon (MH-18, ECS-003604) in Example 1 of the present invention are shown below: Figure 5 This is the desorption test result of NMC-1 in Example 1 of the present invention, where Figure 5 a is the specific surface area distribution diagram, Figure 5 b is the pore size distribution test spectrum; Figure 6 TEM image of the Pt / NMC-1 catalyst in Example 1 of the present invention, wherein Figure 6 b is Figure 6 A partial enlarged view of a; Figure 7 Comparison of membrane electrode tests of catalysts prepared from three types of mesoporous carbon; Figure 8 This is a TEM image of the Pt / NMC-1 catalyst after 30,000 cycles in Example 1 of the present invention, wherein Figure 8 b is Figure 8 A partial enlarged view of a.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0023] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0024] In the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0025] Example An embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: S1: zinc salt, N,N-dimethylformamide, organic ligand, and polyvinyl pyrrolidone are placed in a high-pressure reactor and reacted at 150-180°C for 5-10 hours to obtain a metal organic framework material Zn-MOF. The Zn-MOF is rinsed with anhydrous ethanol 3-5 times and dried at 70-90°C to obtain a standby powder. The organic ligand is at least one of 2-fluoroterephthalic acid, 3-fluorophthalic acid, 4-fluoroisophthalic acid, and 4-fluorophthalic acid. The zinc salt is zinc nitrate, zinc sulfate, zinc chloride, or zinc acetate, and zinc nitrate and zinc acetate are more preferably used. The molar ratio of zinc salt to organic ligand is 1:0.2-2, the molar ratio of zinc salt to N,N-dimethylformamide is 1:120-240; the molar ratio of zinc salt to polyvinyl pyrrolidone is 1:30-70, and the molecular weight of polyvinyl pyrrolidone is not higher than 100,000, and more preferably 50,000; S2: The dried Zn-MOF powder was ultrasonically dispersed in anhydrous ethanol, and then the ethanol solution containing alkali metal hydroxide was added dropwise by 5 pump tubes distributed at equal distances through a peristaltic pump; the dropping process was assisted by strong stirring to ensure that the materials were fully mixed; after the solution was added, it was stirred for 20 to 40 minutes, and the excess solution was filtered out; the filtrate was then placed in an oven at 70 to 90 ° C and dried to obtain the standby powder Zn x Zn 1-x (OH)2-MOF. The single pump tube addition rate is 5-20 mL / min, and the addition time is 30-60 minutes. The concentration of the ethanol solution containing the alkali metal hydroxide is 0.2-1 mol / L, and the alkali metal hydroxide is one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide. Where, 0.1≤X≤0.5.

[0026] S3: Zn x Zn 1-x (OH)2-MOF powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; S4: transferring the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment, the heat treatment atmosphere is high-purity argon or high-purity nitrogen, the heat treatment temperature is 200-300° C., the heat treatment time is 30-60 minutes, and the heating rate is 1-5° C. / min; after the heat treatment is completed, a coarse carbon material powder can be obtained; S5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled to be between 0.8 μm < D90 < 1.5 μm. S6: adding the ground carbon material powder into an acid wash solution for pickling, wherein the pickling solution is a nitric acid or sulfuric acid solution with a concentration of no more than 2M, a pickling temperature of 60-80°C, and a pickling time of 1-3 hours; the mass ratio of the carbon material fine material to the acid solution is 1:2-10; after the pickling is completed, rinsing with deionized water until the filtrate conductivity is less than 200 μs / cm; S7: The acid-washed and rinsed carbon material is vacuum-dried at a temperature of 100-120°C for 8-12 hours. Upon drying, a nitrogen-modified mesoporous carbon material having a high specific surface area and a high degree of graphitization is obtained. This carbon material is labeled NMC.

[0027] Example 1 An embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: 1. Place 1 mol zinc nitrate, 1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (50,000 molecular weight) in an autoclave and react at 170°C for 8 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. Ultrasonic dispersion of dry Zn-MOF powder in anhydrous ethanol, and then dropwise addition of 0.5 mol / L sodium hydroxide ethanol solution through 5 equally spaced pump tubes through a peristaltic pump; the drop rate of a single pump tube is 10 mL / min, and the dropwise addition time is 40 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added, continue stirring for 30 minutes, filter out the excess solution; then place the filtrate in an 80°C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.5).

[0028] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.5) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 300°C, the heat treatment time is 40 minutes, and the heating rate is 3°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 500 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5 M, a pickling temperature of 80 ° C, and a pickling time of 3 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon powder is vacuum dried at 100°C for 12 hours. After drying, a nitrogen-modified mesoporous carbon material with a high specific surface area and a high degree of graphitization is obtained, which is labeled NMC-1.

[0029] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-1, and the platinum loading was 50 wt%.

[0030] Example 2 An embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: 1. Place 1 mol zinc nitrate, 0.8 mol 4-fluorophthalic acid, 180 mol N,N-dimethylformamide, and 50 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 150°C for 10 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. Ultrasonic dispersion of dry Zn-MOF powder in anhydrous ethanol, and then dropwise addition of 1 mol / L lithium hydroxide ethanol solution through 5 equally spaced pump tubes through a peristaltic pump; the drop rate of a single pump tube is 12 mL / min, and the dropwise addition time is 30 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added, continue stirring for 30 minutes, filter out the excess solution; then place the filtrate in an 80°C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.1).

[0031] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.1) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 250°C, the heat treatment time is 50 minutes, and the heating rate is 2°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 600 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 1 M, a pickling temperature of 80°C, and a pickling time of 1 hour. After pickling, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon material powder is vacuum dried at 120°C for 10 hours. After drying, a nitrogen-modified mesoporous carbon material with a high specific surface area and a high degree of graphitization is obtained, which is labeled NMC-2.

[0032] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-2, and the platinum loading was 50 wt%.

[0033] Example 3 An embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: 1. Place 1 mol of zinc acetate, 1.5 mol of 4-fluorophthalic acid, 200 mol of N,N-dimethylformamide, and 30 mol of polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 180°C for 6 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. The dried Zn-MOF powder was ultrasonically dispersed in anhydrous ethanol, and then 5 pump tubes with equal distances were used to add 0.5 mol / L potassium hydroxide ethanol solution dropwise through a peristaltic pump; the drop rate of a single pump tube was 20 mL / min, and the drop addition time was 30 minutes; the drop addition process was assisted by strong stirring to ensure that the material was fully mixed; after the solution was added, it was stirred for 30 minutes and the excess solution was filtered out; the filtrate was then placed in an 80 ° C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.25).

[0034] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.25) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 210°C, the heat treatment time is 60 minutes, and the heating rate is 1°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 1000 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5 M, a pickling temperature of 80 ° C, and a pickling time of 2 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon powder is vacuum dried at 100°C for 12 hours. After drying, a nitrogen-modified mesoporous carbon material with a high specific surface area and a high degree of graphitization is obtained, which is labeled NMC-3.

[0035] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-3, and the platinum loading was 50 wt%.

[0036] Example 4 An embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material, comprising the following steps: 1. Place 1 mol zinc nitrate, 2 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 60 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 180°C for 10 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. The dried Zn-MOF powder was ultrasonically dispersed in anhydrous ethanol, and then 5 pump tubes distributed at equal distances were simultaneously added dropwise to an ethanol solution with a sodium hydroxide concentration of 0.2 mol / L through a peristaltic pump; the drop rate of a single pump tube was 20 mL / min, and the dropwise addition time was 60 minutes; the dropwise addition process was assisted by strong stirring to ensure that the material was fully mixed; after the solution was added, it was stirred for 30 minutes and the excess solution was filtered out; the filtrate was then placed in an 80 ° C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.4).

[0037] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.4) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity nitrogen, the heat treatment temperature is 300°C, the heat treatment time is 60 minutes, and the heating rate is 5°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 800 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 2 M, a pickling temperature of 80°C, and a pickling time of 2 hours. After pickling, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon material powder is vacuum dried at 100°C for 12 hours. After drying, a nitrogen-modified mesoporous carbon material with a high specific surface area and a high degree of graphitization is obtained, which is labeled NMC-4.

[0038] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-4, and the platinum loading was 50 wt%.

[0039] Example 5 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by: 1 mol zinc nitrate, 0.1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (50,000 molecular weight) are placed in an autoclave and then reacted at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a standby powder. The remaining steps remain unchanged. This carbon material is labeled NMC-5.

[0040] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-5, and the platinum loading was 50 wt%.

[0041] Example 6 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by: 1 mol zinc nitrate, 2.5 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (50,000 molecular weight) are placed in an autoclave and then reacted at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a standby powder. The remaining steps remain unchanged. This carbon material is labeled NMC-6.

[0042] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-6, and the platinum loading was 50 wt%.

[0043] Example 7 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by placing 1 mol of zinc nitrate, 1 mol of 4-fluorophthalic acid, 100 mol of N,N-dimethylformamide, and 40 mol of polyvinylpyrrolidone (50,000 molecular weight) in an autoclave, followed by reaction at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a powder for later use. The remaining steps remain unchanged. This carbon material is labeled NMC-7.

[0044] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-7, and the platinum loading was 50 wt%.

[0045] Example 8 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by placing 1 mol of zinc nitrate, 1 mol of 4-fluorophthalic acid, 250 mol of N,N-dimethylformamide, and 40 mol of polyvinylpyrrolidone (50,000 molecular weight) in an autoclave, followed by reaction at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a standby powder. The remaining steps remain unchanged. This carbon material is labeled NMC-8.

[0046] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-8, and the platinum loading was 50 wt%.

[0047] Example 9 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by placing 1 mol of zinc nitrate, 1 mol of 4-fluorophthalic acid, 200 mol of N,N-dimethylformamide, and 25 mol of polyvinylpyrrolidone (50,000 molecular weight) in an autoclave, followed by reaction at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a standby powder. The remaining steps remain unchanged. This carbon material is labeled NMC-9.

[0048] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-9, and the platinum loading was 50 wt%.

[0049] Example 10 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by placing 1 mol of zinc nitrate, 1 mol of 4-fluorophthalic acid, 200 mol of N,N-dimethylformamide, and 80 mol of polyvinylpyrrolidone (50,000 molecular weight) in an autoclave, followed by reaction at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a powder for later use. The remaining steps remain unchanged. This carbon material is labeled NMC-10.

[0050] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-10, and the platinum loading was 50 wt%.

[0051] Example 11 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 1 is replaced by: 1 mol zinc nitrate, 1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (molecular weight 1,300,000) are placed in an autoclave and then reacted at 170°C for 8 hours. The reaction product is rinsed three times with anhydrous ethanol and dried at 80°C to obtain a standby powder. The remaining steps remain unchanged. This carbon material is labeled NMC-11.

[0052] The carbon material was used to prepare a catalyst. The prepared catalyst was labeled Pt / NMC-11, and the platinum loading was 50 wt%.

[0053] Example 12 The embodiment of the present invention provides a preparation method of nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 2 is replaced by: ultrasonically dispersing dry Zn-MOF powder into anhydrous ethanol, and then adding a 0.5 mol / L ethanol solution of sodium hydroxide dropwise through a single pump tube through a peristaltic pump; the dropwise acceleration rate of the single pump tube is 50 mL / min, and the dropwise addition time is 40 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added dropwise, stirring is continued for 30 minutes, and the excess solution is filtered out; and the filtrate is then placed in an 80°C oven to dry to obtain a standby powder Zn x Zn 1-x (OH)2-MOF (X = 0.5). The remaining steps remain unchanged. This carbon material is labeled NMC-12.

[0054] Example 13 The embodiment of the present invention provides a preparation method of nitrogen-doped highly graphitized mesoporous carbon material. The difference from Example 1 is that step 2 is replaced by: ultrasonically dispersing dry Zn-MOF powder into anhydrous ethanol, and then adding 0.5 mol / L sodium hydroxide concentration ethanol solution dropwise through 5 pump tubes distributed at equal distances through a peristaltic pump; the drop rate of a single pump tube is 40 mL / min, and the dropwise addition time is 10 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added dropwise, it is stirred for 30 minutes, and the excess solution is filtered out; and the filtrate is then placed in an 80°C oven to dry to obtain a standby powder Zn x Zn 1-x (OH)2-MOF (X = 0.5). The remaining steps remain unchanged. This carbon material is labeled NMC-13.

[0055] Example 14 This embodiment of the present invention provides a method for preparing a nitrogen-doped highly graphitized mesoporous carbon material. This method differs from Example 1 in that step 6 is replaced with the following: 100 g of the ground carbon material fine powder is added to 500 g of an acid wash solution containing 0.5 M nitric acid at 100°C for 3 hours; after the acid wash, the material is rinsed with deionized water until the filtrate has a conductivity of less than 200 μs / cm. This carbon material is labeled NMC-14.

[0056] Comparative Example 1 A method for preparing a carbon material is provided, comprising the following steps: 1. Place 1 mol zinc nitrate, 1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 170°C for 8 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. Zn-MOF powder and metallic lithium powder were fully mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 3. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 300°C, the heat treatment time is 40 minutes, and the heating rate is 3°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 4. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 5. Add 100g of the ground carbon material fine powder into 500g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5M, a pickling temperature of 80°C, and a pickling time of 3 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200μs / cm. 6. The acid-washed and rinsed carbon material powder was vacuum dried at 100°C for 12 hours. After drying, the carbon material was obtained and labeled as RC-1.

[0057] Comparative Example 2 A method for preparing a carbon material is provided, comprising the following steps: 1. Place 1 mol zinc nitrate, 1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 170°C for 8 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. Ultrasonic dispersion of dry Zn-MOF powder in anhydrous ethanol, and then dropwise addition of 0.5 mol / L sodium hydroxide ethanol solution through 5 equally spaced pump tubes through a peristaltic pump; the drop rate of a single pump tube is 10 mL / min, and the dropwise addition time is 40 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added, continue stirring for 30 minutes, filter out the excess solution; then place the filtrate in an 80°C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.5).

[0058] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.5) powder was placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 300°C, the heat treatment time is 40 minutes, and the heating rate is 3°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 500 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5 M, a pickling temperature of 80 ° C, and a pickling time of 3 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon material powder was vacuum dried at 100°C for 12 hours. After drying, the carbon material was obtained and labeled as RC-2.

[0059] Comparative Example 3 A method for preparing a carbon material is provided, comprising the following steps: 1. Place 1 mol zinc nitrate, 1 mol phthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 170°C for 8 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder. 2. Ultrasonic dispersion of dry Zn-MOF powder in anhydrous ethanol, and then dropwise addition of 0.5 mol / L sodium hydroxide ethanol solution through 5 equally spaced pump tubes through a peristaltic pump; the drop rate of a single pump tube is 10 mL / min, and the dropwise addition time is 40 minutes; the dropwise addition process is assisted by strong stirring to ensure that the material is fully mixed; after the solution is added, continue stirring for 30 minutes, filter out the excess solution; then place the filtrate in an 80°C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.5).

[0060] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.5) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 300°C, the heat treatment time is 40 minutes, and the heating rate is 3°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 500 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5 M, a pickling temperature of 80 ° C, and a pickling time of 3 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon material powder was vacuum dried at 100°C for 12 hours. After drying, the carbon material was obtained and labeled as RC-3.

[0061] Comparative Example 4 A method for preparing a carbon material is provided, comprising the following steps: 1. Place 1 mol zinc nitrate, 1 mol 4-fluorophthalic acid, 200 mol N,N-dimethylformamide, and 40 mol polyvinylpyrrolidone (molecular weight 40,000) in an autoclave and react at 170°C for 8 hours. Rinse the reaction product three times with anhydrous ethanol and dry it at 80°C to obtain a powder for later use. 2. The dried Zn-MOF powder was ultrasonically dispersed in anhydrous ethanol, and then 5 pump tubes with equal distances were used to add ethanol solution with ammonia concentration of 0.5 mol / L dropwise through a peristaltic pump; the drop rate of a single pump tube was 10 mL / min, and the dropwise addition time was 40 minutes; the dropwise addition process was assisted by strong stirring to ensure that the material was fully mixed; after the solution was added, it was stirred for 30 minutes and the excess solution was filtered out; the filtrate was then placed in an 80 ° C oven to dry to obtain the standby powder Zn x Zn 1-x (OH)2-MOF (X=0.5).

[0062] 3. Zn x Zn 1-x (OH)2-MOF (X = 0.5) powder and metallic lithium powder were thoroughly mixed in an inert atmosphere glove box, then placed in a graphite crucible and covered; 4. Transfer the graphite crucible containing the mixture powder to an atmosphere roasting furnace for heat treatment. The heat treatment atmosphere is high-purity argon, the heat treatment temperature is 300°C, the heat treatment time is 40 minutes, and the heating rate is 3°C / min. After the heat treatment is completed, a coarse carbon material powder can be obtained; 5. Grind and crush the coarse carbon material powder into fine powder to reduce its particle size. The particle size range of the ground material is controlled between 0.8μm<D90<1.5μm; 6. Add 100 g of the ground carbon material fine powder into 500 g of pickling solution for pickling. The pickling solution is a nitric acid solution with a concentration of 0.5 M, a pickling temperature of 80 ° C, and a pickling time of 3 hours. After the pickling is completed, rinse with deionized water until the filtrate conductivity is less than 200 μs / cm. 7. The acid-washed and rinsed carbon material powder was vacuum-dried at 100°C for 12 hours. After drying, the carbon material was obtained and labeled as RC-4.

[0063] Comparative Example 5: A method for preparing a carbon material is provided. The difference from Example 1 is that X is 0.05, and the other steps remain unchanged. The carbon material is marked as RC-5.

[0064] Comparative Example 6: A method for preparing a carbon material is provided. The difference from Example 1 is that X is 0.9, and the other steps remain unchanged. The carbon material is marked as RC-6.

[0065] 1. Preparation of Catalyst 1. Dissolve 3.26 g of tetraammineplatinum acetate in 6 mL of deionized water to form a homogeneous solution; 2. Add tetraammine platinum acetate solution dropwise to the carbon support in a vacuum chamber while stirring the mixture; 3. The mixed material is quenched with liquid nitrogen and placed in a freeze dryer for freeze drying for 24 hours; 4. The freeze-dried material was placed in a rotary tube furnace for thermal reduction at a temperature of 600°C for 2 hours at a heating rate of 5°C / min. The gas was a 5 Vol% H2 / Ar mixture. After the thermal reduction was completed, the desired catalyst was obtained. The catalysts with carbon supports of MH-18, ECS-003604, and NMC-X (X represents the example number) were marked as Pt / MH, Pt / ECS, and Pt / NMC-X, respectively, and the platinum loading was 50 wt%.

[0066] 2. Test Method TEM test: The NMC-1, Pt / NMC-1 catalysts prepared in Example 1 and the Pt / NMC-1 catalyst after 30,000 cycles were added to a centrifuge tube with ethanol and water (volume ratio 1:1) and ultrasonically vibrated uniformly; the mixture was dropped onto a copper mesh, dried, and then placed in a transmission electron microscope for testing. The test results are shown as follows: Figure 2 、 Figure 6 and Figure 8 shown.

[0067] SEM test: The NMC-1 prepared in Example 1 was smeared on the conductive adhesive, and loose powder was blown off with nitrogen. The NMC-1 was then placed in a scanning electron microscope for testing.

[0068] TG test: About 15 mg of NMC-1 prepared in Example 1 was weighed using an electronic analytical balance and placed in an alumina crucible, and then placed in a synchronous thermal analysis test equipment for testing; the heating rate was 10°C / min; the test temperature range was room temperature 0~1000°C; the calcination atmosphere was zero-grade air, and the test results were as follows: Figure 3 As shown, the specific surface area and pore size distribution test spectrum is as follows Figure 5 shown.

[0069] Specific surface area and pore size distribution testing: Weigh 100 mg of sample into a sample tube. Connect the sample tube to a degassing station and degas at 200°C for 6 hours. Connect the degassed sample to a nitrogen adsorption / desorption tester for testing. The test gas is nitrogen.

[0070] XRD test: The NMC-1 prepared in Example 1 and the commercial mesoporous carbon MH-18 and ECS-003604 were filled into the sample tank and flattened, and then the sample tank was placed in the XRD tester for testing to obtain the XRD test spectrum; the test scan rate was 5° / min, and the scanning angle range was 20~80°; finally, the average particle size of the platinum nanoparticles was calculated according to the Scherrer formula. The test results are as follows: Figure 4 shown.

[0071] Membrane electrode test: Weigh the prepared platinum-carbon catalyst powder, add a certain proportion of pure water, isopropanol and Nafion solution in turn, mix, and ultrasonically homogenize the mixture to obtain a catalyst slurry for use. The mass ratio of each component is as follows: Nafion to carbon mass ratio 0.7, isopropanol: pure water = 1:1, platinum-carbon catalyst: (mixed solution of isopropanol and pure water) = 1:20. The slurry is loaded into an ultrasonic spray device and sprayed on both sides of the proton exchange membrane, with a platinum loading of 0.05 mg / cm on the anode surface. 2 , cathode platinum loading 0.3 mg / cm 2 , and dried at 80℃, combined with carbon paper and frame, hot pressed on a hot press to form a membrane electrode. The prepared membrane electrode is installed in the test fixture, and then the fixture is connected to the fuel cell test bench for testing. The battery temperature is 80℃, the anode relative humidity is 50%, the cathode relative humidity is 50%, the cathode back pressure is 150Kps, and the anode gas stoichiometric ratio is 1.8. The test results are as follows Figure 7 shown.

[0072] The nitrogen adsorption and desorption test results of NMC-1 are as follows: Figure 5 As shown, the nitrogen adsorption and desorption test results of the carbon materials prepared in Examples 1-4 and Comparative Examples 1-4 are compared in Table 1 below, the elemental analysis test results of the example samples are shown in Table 2 below, and the membrane electrode test comparison data of the catalysts prepared from three mesoporous carbons are shown in Table 3 below: Table 1: Nitrogen adsorption and desorption test results

[0073] Table 2: Elemental analysis test results of samples

[0074] Table 3: Comparative data of membrane electrode tests on three mesoporous carbon catalysts

[0075] Conclusion: Reference Figure 1 The SEM image of the carbon material NMC-1 prepared in Example 1 shows that its morphology is irregular and its size varies; Figure 2From the TEM results, NMC-1 has many holes. The formation of holes mainly comes from the evaporation and removal of metal particles and the pyrolysis of organic matter. In addition, there are obvious carbon lattice fringes in the TEM image, indicating that the degree of graphitization of the carbon material is high. Figure 3 The TG test results show that the residual ash content of the carbon material NMC-1 after calcination is very low, indicating that most of the metal particles and metal salts have been removed and very little remains.

[0076] Reference Figure 4 The XRD patterns of the carbon material NMC-1 prepared in Example 1 were compared with those of two typical commercial mesoporous carbons (MH-18 and ECS-003604). The diffraction peak intensity of NMC-1 near 26.5° was significantly higher than that of the other two commercial mesoporous carbons, indicating that the carbon material NMC-1 has the highest degree of graphitization. This is because the large amount of heat and extremely high temperature generated during the reaction between metallic lithium and fluoride promote the pyrolysis, carbonization and graphitization of organic matter, resulting in the high degree of graphitization of the carbon material NMC-1.

[0077] Reference Figure 5 Nitrogen adsorption-desorption tests on the carbon material NMC-1 prepared in Example 1 revealed a distinct hysteresis loop in its mesoporous structure, indicating that it is a mesoporous material. Curve fitting data (Table 1) indicate that the carbon material NMC-1 possesses high specific surface area and mesopore diameter characteristics. The test results of Examples 2-9 and 14 also demonstrate high specific surface area and mesoporous structure. Therefore, the specific surface area and pore size distribution of carbon materials can be adjusted by adjusting the relevant parameters.

[0078] Continuing with Table 1, a comparison of Example 5 with Example 1 shows that when the amount of organic carrier is too small, ligand deficiency defects may occur, causing reduced framework stability, thereby affecting the specific surface area and pore structure of the final carbon material. A comparison of Example 6 with Example 1 shows that an excessive amount of organic carrier may interfere with the Zn-MOF crystallization equilibrium, resulting in incomplete coordination and the formation of uncontrolled defects, which may reduce framework stability and thus affect the specific surface area and pore structure of the final carbon material. Therefore, the molar ratio of zinc salt to organic ligand is preferably 1:0.2~2; Comparing Example 7 with Example 1, it can be seen that when the amount of N,N-dimethylformamide is too small, it may lead to problems such as insufficient dissolution of the precursor reactants, hindered crystal growth, and aggravated side reactions, thereby affecting the specific surface area and pore structure of the final carbon material. Comparing Example 8 with Example 1, it can be seen that when the amount of N,N-dimethylformamide is too large, it may lead to problems such as reduced product crystallinity, too small crystal size, and the risk of residual impurities, thereby affecting the specific surface area and pore structure of the final carbon material. Therefore, the preferred molar ratio of zinc salt to N,N-dimethylformamide is 1:120-240; Comparing Example 9 with Example 1, it can be seen that when the amount of polyvinyl pyrrolidone is too small, the reaction kinetics may be slowed down, the MOF bonding strength may be weakened, and problems such as incomplete crystal growth or the formation of amorphous byproducts may occur, thereby affecting the specific surface area and pore structure of the final carbon material. Comparing Example 10 with Example 1, it can be seen that when the amount of polyvinyl pyrrolidone is too large, problems such as product morphology and pore size distribution may be affected, thereby affecting the specific surface area and pore structure of the final carbon material. The preferred molar ratio of zinc salt to polyvinyl pyrrolidone is 1:30-70; From the comparison between Example 11 and Example 1, it can be seen that when the molecular weight of polyvinyl pyrrolidone is too large, it may affect the crystal morphology and pore size distribution of Zn-MOF, thereby affecting the specific surface area and pore structure of the final carbon material. Therefore, it is better when the molecular weight of polyvinyl pyrrolidone is ≤100,000; Comparing Example 12 with Example 1 shows that replacing five pump tubes with one results in locally high alkali concentrations, leading to the formation of overly large hydroxide particles (Zn(OH)2). Therefore, the advantage of using five pump tubes is that the alkali solution added per unit time can be evenly dispersed and dripped into the reaction system, avoiding localized high alkali concentrations. This is more conducive to controlling the formation of smaller hydroxide particles (Zn(OH)2), thereby regulating the pore structure of the carbon material.

[0079] Comparing Example 13 with Example 1, it can be seen that when the dripping rate of a single pump tube is greater than 20 mL / min and the dripping time is less than 30 minutes, the local alkali concentration will be too high, resulting in the formation of excessively large hydroxide particles (Zn(OH)2). Therefore, the dripping rate of a single pump tube is preferably 5-20 mL / min, and the dripping time is preferably 30-60 minutes; Comparison of Example 14 with Example 1 shows that when the pickling temperature is greater than 80°C, the oxidation process of the carbon material is easily aggravated, and even excessive oxidation causes the carbon material structure to collapse, reducing the specific surface area and pore volume of the carbon material. Therefore, the pickling temperature is preferably 60-80°C.

[0080] As can be seen from Table 2, the carbon materials prepared in the examples of the present invention are rich in nitrogen. The presence of nitrogen is beneficial to the dispersion of platinum nanoparticles during the catalyst preparation process (e.g. Figure 6 As shown), high activity of the catalyst and high power density of the membrane electrode (as Figure 7 At the same time, the strong anchoring effect of nitrogen on platinum nanoparticles makes the platinum nanoparticles have strong stability during the electrochemical cycle, and can effectively slow down the dissolution, migration, agglomeration, and shedding of platinum nanoparticles during the electrochemical cycle, thereby enhancing the stability of the catalyst (refer to Figure 7 、 Figure 8and Table 3); Even after 30,000 cycles, the performance of Pt / NMC-1 is better than that of the catalyst prepared from commercial mesoporous carbon materials (ref. Figure 7 and Table 3 ).

[0081] Compared to Example 1, Comparative Example 1 reduces the addition of alkali solution. As a result, the metal ions lack hydroxides to react and aggregate to form small hydroxide particles (Zn(OH)2). Instead, they are anchored in specific locations by the organic framework. When high temperatures cause the organic matter to pyrolyze and carbonize in situ, the metal ions are restricted in diffusion and unable to aggregate to form larger particles. Consequently, only smaller pores remain in the carbon framework, resulting in a relatively small average pore size (see Table 1). Such a small average pore size is detrimental to oxygen mass transfer. Comparative Examples 5 and 6 are similarly affected by the proportion of small hydroxide particles (Zn(OH)2) formed, resulting in significant differences in the specific surface area and pore structure of the resulting carbon materials.

[0082] Compared with Example 1, Comparative Examples 2 and 3 respectively reduce the addition of lithium powder and the use of fluorine-containing organic ligands, so that there is no high temperature process generated by the reaction of metallic lithium and fluoride, resulting in the absence of pyrolysis carbonization and pore formation of the material at high temperature, and thus the specific surface area is lower (see Table 1).

[0083] Compared with Example 1, Comparative Example 4 uses a non-alkali metal alkaline solution, and the specific surface area of ​​the carbon material prepared in Comparative Example 4 is lower than that in Example 1; high-temperature pyrolysis treatment can realize the melting characteristics of the alkali metal salt, protect the graphitized structure during the pyrolysis process, promote the increase in the degree of graphitization and the formation of microporous / mesoporous structure, and thus can promote a higher degree of graphitization and a higher specific surface area in Example 1.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, improvements, and the like made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention. It should be noted that the structures or components illustrated in the accompanying drawings are not necessarily drawn to scale, and that descriptions of known components, processing techniques, and processes are omitted to avoid unnecessarily limiting the present invention.

Claims

1. A nitrogen-doped highly graphitized mesoporous carbon material, characterized in that: Including Zn x Zn 1-x A material prepared from (OH)2-MOF and metallic lithium, wherein 0.1≤X≤0.

5.

2. The nitrogen-doped highly graphitized mesoporous carbon material according to claim 1, characterized in that: The Zn x Zn 1-x (OH)2-MOF includes materials prepared from metal organic framework material Zn-MOF and alkali metal hydroxide; The metal organic framework material Zn-MOF includes a material prepared from zinc salt, N,N-dimethylformamide, an organic ligand and polyvinyl pyrrolidone.

3. The nitrogen-doped highly graphitized mesoporous carbon material according to claim 2, characterized in that: The organic ligand includes at least one of 2-fluoroterephthalic acid, 3-fluorophthalic acid, 4-fluoroisophthalic acid, and 4-fluorophthalic acid; The zinc salt includes at least one of zinc nitrate, zinc sulfate, zinc chloride and zinc acetate.

4. The nitrogen-doped highly graphitized mesoporous carbon material according to claim 1, characterized in that: The molar ratio of the zinc salt to the organic ligand is 1:0.2~2; The molar ratio of the zinc salt to N,N-dimethylformamide is 1: 120-240; The molar ratio of the zinc salt to the polyvinyl pyrrolidone is 1: 30-70; The molecular weight of the polyvinyl pyrrolidone is ≤100,000.

5. A method for preparing the nitrogen-doped highly graphitized mesoporous carbon material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: zinc salt, N,N-dimethylformamide, organic ligand, and polyvinyl pyrrolidone are placed in a high-pressure reactor to prepare a metal-organic framework material Zn-MOF, and the metal-organic framework material Zn-MOF is rinsed and dried for later use; S2: Disperse the dried metal organic framework material Zn-MOF into anhydrous ethanol, then dropwise add an ethanol solution containing alkali metal hydroxide and stir, filter and dry in turn to obtain the standby powder Zn x Zn 1-x (OH)2-MOF; S3: Powder Zn x Zn 1-x (OH)2-MOF and metallic lithium powder were heat-treated under an inert atmosphere to obtain a coarse carbon material powder; S4: Grinding and crushing the coarse carbon material powder into fine powder; S5: putting the fine powder into an acid washing solution for pickling, and rinsing with deionized water until the conductivity of the filtrate is less than 200 μs / cm to obtain a fine carbon material; S6: vacuum drying the carbon material fine material to obtain a mesoporous carbon material.

6. The method for preparing a nitrogen-doped highly graphitized mesoporous carbon material according to claim 5, characterized in that: The reaction temperature for preparing the metal organic framework material Zn-MOF described in S1 is 150-180° C., and the reaction time is 5-10 hours.

7. The method for preparing a nitrogen-doped highly graphitized mesoporous carbon material according to claim 5, characterized in that: The step of adding the ethanol solution containing alkali metal hydroxide dropwise with stirring in S2 comprises: using five equally spaced pump tubes to simultaneously add the ethanol solution containing alkali metal hydroxide dropwise through a peristaltic pump, and assisting stirring during the dropping process; and continuing stirring for 25 to 35 minutes after the solution is added dropwise; The dripping rate of a single pump tube is 5~20mL / min, and the dripping time is 30~60 minutes.

8. The method for preparing a nitrogen-doped highly graphitized mesoporous carbon material according to claim 5, wherein: The alkali metal hydroxide includes at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide, and the concentration of the ethanol solution containing the alkali metal hydroxide is 0.2-1 mol / L.

9. The method for preparing a nitrogen-doped highly graphitized mesoporous carbon material according to claim 5, wherein: The heat treatment temperature in S3 is 200-300° C., the heat treatment time is 30-60 minutes, the heating rate is 1-5° C. / min, and the inert atmosphere includes argon and / or nitrogen.

10. Use of a mesoporous carbon material prepared by the method for preparing a nitrogen-doped highly graphitized mesoporous carbon material according to any one of claims 5 to 9, characterized in that: The method comprises applying the porous carbon material to a hydrogen fuel cell.

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