Preparation method of boron-doped carbon microspheres with high specific surface area and boron-doped carbon microspheres
By using boron-containing monomers with specific structures to prepare carbon microspheres, inhibit the substitution reaction on the benzene ring, the problem of difficult to prepare carbon microspheres with high specific surface area and high boron content in the prior art is solved, and the effect of efficient space conversion to specific surface area is achieved, and it is suitable for supercapacitor electrode materials.
Patent Information
- Application Number
- CN202311080457.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-25
- Publication Date
- 2025-02-25
AI Technical Summary
The prior art is difficult to prepare carbon microspheres with high specific surface area and high boron content by simple, controllable and mass-manufactureable methods.
Boron-containing monomers with specific structures are used as the boron source, and the cross-linking density of polymer microspheres is controlled by introducing groups to pre-occupy the active site on the benzene ring or introducing groups with inducing electron withdrawal effects. Boron-doped carbon microspheres with high specific surface area were then prepared by carbonization.
It has achieved a high specific surface area, rich pore structure and high boron content carbon microspheres, which are suitable for supercapacitor electrode materials, improve the performance of supercapacitors, and has the advantages of rich raw materials, low preparation cost, simple process, and green and environmentally friendly synthesis process. It is suitable for large-scale industrial production.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of carbon material preparation, and in particular to a method for preparing boron-doped carbon microspheres with a high specific surface area and the boron-doped carbon microspheres. Background Art
[0002] With the continuous consumption of energy and the resulting numerous environmental and resource problems, new energy has become an ideal alternative. The storage, use, and conversion of new energy are inseparable from the development of new energy devices, of which carbon materials are an important component. Among the various carbon materials, carbon microspheres are an ideal functional material. They have a high specific surface area, controllable size and distribution, excellent chemical stability, and a rich pore structure. Therefore, they are widely used in energy storage and conversion, catalysis and other fields. Traditional heat-generating carbon materials have limited applications due to their single composition. Doping, such as doping with boron, nitrogen, phosphorus, sulfur, etc., is an effective method to improve the performance of carbon materials. Among them, boron doping is a widely used dopant. Boron doping can introduce defects, increase conductivity, and increase active sites. There are two main methods for preparing boron-doped carbon microspheres: one is chemical vapor deposition (CVD), and the other is a method that combines adsorption, heat treatment, and carbonization. For example, Coville et al. (J. Catal. 305 (2013) 36-45; J. Mol. Catal. A: Chem. 422 (2016) 165-174; Diam. Relat. Mater. 74 (2017) 70-80) used trimethyl borate, boron chloride, boron fluoride, etc. as boron sources and acetylene, heptane, toluene, etc. as carbon sources to prepare boron-containing carbon microspheres by CVD. However, CVD is not suitable for large-scale preparation due to its high energy consumption and high pollution.
[0003] Therefore, more methods are to use a method of combining adsorption and heat treatment with carbonization. In this method, boric acid and boron fluoride are commonly used boron sources. Boron-containing carbon microspheres are obtained by mixing pre-carbonized microspheres with boric acid, boron fluoride, etc. for adsorption and then carbonizing at high temperature again. However, this method has the disadvantages of uneven dispersion of inorganic boron and easy precipitation, so the boron content in the carbon microspheres is relatively low. Using organic boron as a boron source is an improved method. For example, 3-hydroxyphenylboric acid is used as a boron source and a carbon source, and boron-doped carbon microspheres are prepared by a one-step hydrothermal method and carbonization. This method significantly improves the shortcomings of the original method. However, because 3-hydroxyphenylboric acid has multiple reactive sites on the benzene ring, the cross-linking density of the prepared polymer microspheres is high, resulting in too high a residual carbon in the polymer microspheres. In addition, because the boron content in the polymer microspheres prepared by 3-hydroxyphenylboric acid is relatively high, the volatilization of oxides such as carbon, hydrogen, and boron is further suppressed during the carbonization process, and the prepared carbon microspheres have a very low specific surface area (about 44 m 2 g -1Therefore, how to prepare carbon microspheres with high specific surface area and high boron content through a simple, controllable and mass-producible method remains a huge challenge. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a simple, controllable, and mass-producible method for preparing boron-doped carbon microspheres with high specific surface area and the boron-doped carbon microspheres.
[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing boron-doped carbon microspheres with a high specific surface area, comprising the following steps: reacting a boron-containing monomer with an aldehyde and a catalyst in a solvent to obtain boron-doped microspheres; then carbonizing the boron-doped microspheres to obtain boron-doped carbon microspheres;
[0006] The boron-containing monomer is a combination of one or more monomers of the following structures:
[0007]
[0008] Wherein, R1 is hydroxyl or amino;
[0009] R2, R3 are halogen, hydroxy, amino or alkyl;
[0010] R4, R5, R6, and R7 are all H, or one of R4, R5, R6, and R7 is halogen or alkyl, and the others are all H, or R4 and R5 are both halogen or alkyl, and R6 and R7 are both H;
[0011] R8, R9, R 10 is halogen or alkyl and at least one of them is H, R 11 It is one of H, halogen and alkyl.
[0012] Another technical solution of the present invention is to provide boron-doped carbon microspheres prepared by the above-mentioned method for preparing boron-doped carbon microspheres with high specific surface area.
[0013] The beneficial effects of the present invention are as follows: the boron-doped carbon microspheres with high specific surface area prepared by the method of preparing boron-doped carbon microspheres with high specific surface area of the present invention use a boron-containing monomer with a specific structure as a boron source, and suppress the substitution reaction on the benzene ring by introducing a group to pre-occupy some active substitution sites on the benzene ring, or introduce a group with an induced electron-withdrawing effect, or increase the spatial position of the benzene ring, thereby achieving the purpose of controlling the cross-linking density of the polymer microspheres. During the carbonization process of preparing the carbon microspheres, the cross-linking density of the polymer microspheres is reduced. Therefore, during the high-temperature carbonization cracking process, the molecular segments and benzene rings can be more effectively cracked, thereby achieving more effective space sacrifice and generating a large number of holes, thereby achieving the effect of converting the sacrificed space into specific surface area.
[0014] The high-specific-surface-area boron-doped carbon microspheres produced by the present invention have the advantages of large specific surface area, rich pore structure, and high boron content. They can be used as supercapacitor electrode materials to improve supercapacitor performance. The method for producing high-specific-surface-area boron-doped carbon microspheres of the present invention has the advantages of abundant raw materials, low preparation cost, simple process, and environmentally friendly synthesis process, making it suitable for large-scale industrial production. DETAILED DESCRIPTION
[0015] To explain the technical content, achieved objectives and effects of the present invention in detail, the following describes them in conjunction with the implementation methods.
[0016] The key concept of the present invention is to use a boron-containing monomer with a specific structure as a boron source. The boron-containing monomer pre-occupies some active substitution sites on the benzene ring by introducing one or more groups, or introduces an electron-withdrawing group with an inductive effect to passivate the benzene ring, or introduces an alkyl group to increase the steric hindrance of the benzene ring to inhibit the substitution reaction on the benzene ring and adjust the cross-linking density of the polymer microspheres. Then, carbon microspheres are prepared by further carbonization. Because the substitution sites on the benzene ring are suppressed, the reaction activity is reduced and the cross-linking density is reduced. Therefore, during the high-temperature carbonization and cracking process, the molecular segments and benzene rings can achieve more effective cracking. A large amount of carbon, hydrogen, boron, etc. can pass through the carbon layer in the form of oxides, achieving effective space sacrifice and generating a large number of pores, achieving the effect of converting the sacrificed space into specific surface area. Test results show that the boron-containing carbon microspheres prepared based on the space sacrifice strategy have a large specific surface area, rich pore structure and high boron content, and have outstanding supercapacitor performance as supercapacitor electrode materials.
[0017] The present invention provides a method for preparing boron-doped carbon microspheres with a high specific surface area, comprising the following steps: reacting a boron-containing monomer with an aldehyde and a catalyst in a solvent to obtain boron-doped microspheres; then carbonizing the boron-doped microspheres to obtain boron-doped carbon microspheres;
[0018] The boron-containing monomer is a combination of one or more monomers of the following structures:
[0019]
[0020] Wherein, R1 is hydroxyl or amino;
[0021] R2, R3 are halogen, hydroxy, amino or alkyl;
[0022] R4, R5, R6, and R7 are all H, or one of R4, R5, R6, and R7 is halogen or alkyl, and the others are all H, or R4 and R5 are both halogen or alkyl, and R6 and R7 are both H;
[0023] R8, R9, R 10 is halogen or alkyl and at least one of them is H, R11 It is one of H, halogen and alkyl.
[0024] In the existing technology, the cross-linking density of polymer microspheres is high, and the benzene rings are stacked excessively, which will lead to excessively high residual carbon in the polymer microspheres. For example, the literature reports that the carbon microspheres obtained using 3-hydroxyphenylboronic acid as the raw material have a very low specific surface area. This is mainly because the boron-containing group occupies the meta position of the benzene ring and has no obvious effect on the substitution reaction and activity of the ortho / para position. In addition, the two hydroxyl groups on the boron atom can also participate in the reaction. Therefore, the reaction cross-linking degree is high, the thermal stability is very good, the cracking effect is poor, and it is difficult to form pores, resulting in a low specific surface area.
[0025] When the boron-containing group occupies the ortho or para position, the number of active sites on the benzene ring is reduced, and the cross-linking density is significantly reduced. Or when the boron-containing group occupies the meta position, if a halogen or alkyl group is introduced to occupy the active site of the benzene ring, the reactivity of the boron-containing monomer will be reduced due to the inductive effect or increased steric hindrance, which can also reduce the cross-linking density. However, the reactivity of the benzene ring cannot be affected too much, such as when R6 and R7 are both halogen or alkyl, or when R8, R9, R 10 When all the substituents are halogens or alkyls, the active sites on the benzene ring disappear. Even if the substituents on the boron can react, they cannot form macromolecules. The residual carbon content during carbonization is extremely low, the pores collapse, and the specific surface area is low. Similarly, when there are strong electron-withdrawing groups or inert groups (such as nitro and cyano groups) on the benzene ring, macromolecules may not form, affecting the specific surface area.
[0026] As can be seen from the above description, the beneficial effect of the above-mentioned method for preparing high-specific-surface-area boron-doped carbon microspheres is that the substitution reaction on the benzene ring is suppressed by introducing groups to pre-occupy some active substitution sites on the benzene ring, or by introducing groups with an induced electron-withdrawing effect, or by increasing the spatial position of the benzene ring, thereby achieving the purpose of controlling the crosslink density of the polymer microspheres. During the carbonization process to prepare the carbon microspheres, the crosslink density of the polymer microspheres is reduced. Therefore, during the high-temperature carbonization cracking process, the molecular segments and benzene rings can be more effectively cracked, thereby achieving more effective spatial sacrifice and generating a large number of pores, achieving the effect of converting the sacrificed space into specific surface area.
[0027] The high-specific-surface-area boron-doped carbon microspheres produced by the present invention have the advantages of large specific surface area, rich pore structure, and high boron content. They can be used as supercapacitor electrode materials to improve supercapacitor performance. The method for producing high-specific-surface-area boron-doped carbon microspheres of the present invention has the advantages of abundant raw materials, low preparation cost, simple process, and environmentally friendly synthesis process, making it suitable for large-scale industrial production.
[0028] Furthermore, in the above method for preparing boron-doped carbon microspheres with high specific surface area, R2 and R3 are preferably hydroxyl groups.
[0029] Furthermore, in the above-mentioned method for preparing boron-doped carbon microspheres with high specific surface area, when an active site on the benzene ring is already occupied by a boron-containing group, such as structure I and structure II, if a strong inert group is continued to be introduced and occupy the active site, it may cause the degree of polymerization to decrease too much, and the pores are easy to collapse during cracking, which will cause the specific surface area to decrease. Preferably, R4, R5 are one of H, halogen, and alkyl, and R6 and R7 are both H; further preferably, R4, R5 are one of H, halogen, and alkyl and at least one of them is H, and R6 and R7 are both H; further preferably, R4, R5, R6, and R7 are all H.
[0030] Based on the same mechanism, preferably, R8, R9, R 10 One of them is halogen or alkyl, and the others are H, R 11 is one of H, halogen, and alkyl; further preferably, R8, R9, R 10 One of them is halogen or alkyl, and the others are H, R 11 For H.
[0031] Furthermore, in the above method for preparing boron-doped carbon microspheres with high specific surface area, the aldehyde is one or a combination of two or more of formaldehyde, paraformaldehyde, benzaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde.
[0032] Furthermore, in the above method for preparing boron-doped carbon microspheres with high specific surface area, the catalyst is one or more of ammonia water, sodium hydroxide, potassium hydroxide, barium hydroxide, and magnesium hydroxide.
[0033] Furthermore, in the above-mentioned method for preparing high-specific-surface-area boron-doped carbon microspheres, the solvent is one or more of water, ethanol, methanol, acetone, tetrahydrofuran, methane, and chloroform. By varying the type and amount of solvent, the size of the carbon microspheres can be controlled. The preferred solvent of the present invention is water, which reduces the use of organic solvents, is low-cost, pollution-free, and has better environmental benefits.
[0034] Furthermore, in the above-mentioned method for preparing boron-doped carbon microspheres with high specific surface area, the boron monomer is one or a combination of two or more of 2-hydroxyphenylboric acid, 4-hydroxyphenylboric acid, 2-aminophenylboric acid, 4-aminophenylboric acid, 3-fluoro-4-hydroxyphenylboric acid, 2-fluoro-6-hydroxyphenylboric acid, 2-fluoro-4-hydroxyphenylboric acid, 4-hydroxy-2-methylphenylboric acid, 2-fluoro-3-hydroxyphenylboric acid, 3-fluoro-5-hydroxyphenylboric acid, 3-fluoro-4-hydroxyphenylboric acid, and 2,6-difluoro-4-hydroxyphenylboric acid.
[0035] The present invention also provides boron-doped carbon microspheres prepared by the above-mentioned method for preparing boron-doped carbon microspheres with high specific surface area.
[0036] From the above description, it can be seen that the boron-doped carbon microspheres obtained above have a high specific surface area, which provides sufficient active sites for ion adsorption. The rich pore structure inside the carbon microsphere material can act as an ion transfer channel, which is beneficial to improving electrolyte diffusion and ion transfer efficiency. The introduction of boron can improve conductivity, produce more defects, and increase pseudocapacitance. Therefore, using the carbon microspheres of the present invention as electrode materials can effectively achieve the improvement of the capacitance performance and rate performance of supercapacitors.
[0037] Example 1
[0038] A method for preparing boron-doped carbon microspheres with a high specific surface area comprises the following steps:
[0039] 0.1 g of 2-hydroxyphenylboric acid, 0.12 g of 37% formaldehyde aqueous solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B1. The prepared boron-doped carbon microspheres B1 have a specific surface area of 751 m 2 / g, and the boron content is 6.6%.
[0040] Example 2
[0041] A method for preparing boron-doped carbon microspheres with a high specific surface area comprises the following steps:
[0042] 0.1 g of 4-aminophenylboronic acid, 0.12 g of 37% formaldehyde aqueous solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B2. The prepared boron-doped carbon microspheres B2 have a specific surface area of 808 m 2 / g, and the boron content is 7.5%.
[0043] Example 3
[0044] A method for preparing boron-doped carbon microspheres with a high specific surface area comprises the following steps:
[0045] 0.1 g of 4-hydroxy-2-methylphenylboronic acid, 0.1 g of 37% formaldehyde aqueous solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B3. The prepared boron-doped carbon microspheres B3 have a specific surface area of 784 m 2 / g, and the boron content is 5.8%.
[0046] Example 4
[0047] A method for preparing boron-doped carbon microspheres with a high specific surface area comprises the following steps:
[0048] 0.1 g of 2-fluoro-3-hydroxyphenylboronic acid, 0.1 g of 37% formaldehyde aqueous solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B4. The prepared boron-doped carbon microspheres B4 have a specific surface area of 712 m 2 / g, and the boron content is 6.3%.
[0049] Example 5
[0050] A method for preparing boron-doped carbon microspheres with a high specific surface area comprises the following steps:
[0051] 0.1 g of 2-fluoro-4-hydroxyphenylboronic acid, 0.1 g of 37% formaldehyde aqueous solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B5. The prepared boron-doped carbon microspheres B5 have a specific surface area of 667 m 2 / g, and the boron content is 6.4%.
[0052] Comparative Example 1
[0053] A method for preparing boron-doped carbon microspheres comprises the following steps:
[0054] 0.1 g of 3-hydroxyphenylboric acid, 0.1 g of 37% formaldehyde solution, and 0.1 g of 25% ammonia water were added to 18 mL of water and mixed; the mixture was added to a high-pressure reactor and heated to 180°C for 24 hours to obtain boron-doped microspheres; the boron-doped microspheres were carbonized at 800°C for 4 hours under a nitrogen atmosphere to obtain boron-doped carbon microspheres B6. The prepared boron-doped carbon microspheres B6 have a specific surface area of 45 m 2 / g, and the boron content is 6.0%.
[0055] In summary, the boron-doped carbon microspheres with high specific surface area prepared by the present invention use a boron-containing monomer with a specific structure as a boron source, and pre-occupy some active substitution sites on the benzene ring by introducing a group, or introduce an electron-withdrawing group with an inductive effect to passivate the benzene ring, or introduce an alkyl group to increase the steric hindrance of the benzene ring, thereby inhibiting the substitution reaction on the benzene ring, so as to achieve the purpose of controlling the cross-linking density of the polymer microspheres. During the carbonization process of preparing carbon microspheres, the cross-linking density of the polymer microspheres is reduced. Therefore, during the high-temperature carbonization and cracking process, the molecular segments and benzene rings can be more effectively cracked, thereby achieving effective spatial sacrifice and generating a large number of pores, achieving the effect of converting the sacrificed space into specific surface area. The boron-doped carbon microspheres prepared by the present invention have the advantages of large specific surface area, rich pore structure and high boron content, and can be used as supercapacitor electrode materials to improve supercapacitor performance. As a method for preparing the boron-doped carbon microspheres with high specific surface area, the method has abundant raw materials, low preparation cost, simple process, green and environmentally friendly synthesis process, and is suitable for large-scale industrial production.
[0056] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.
Claims
1. A method for preparing boron-doped carbon microspheres with high specific surface area, characterized in that: The method comprises the following steps: reacting a boron-containing monomer with an aldehyde and a catalyst in a solvent to obtain boron-doped microspheres; then carbonizing the boron-doped microspheres to obtain boron-doped carbon microspheres; The boron-containing monomer is a combination of one or more monomers of the following structures: Wherein, R1 is hydroxyl or amino; R2, R3 are halogen, hydroxy, amino or alkyl; R4, R5, R6, R7 are all H, or one of R4, R5, R6, R7 is halogen or alkyl, and the others are all H, or R4 and R5 are both halogen or alkyl, and R6 and R7 are both H; R8, R9, R 10 is halogen or alkyl and at least one of them is H, R 11 It is one of H, halogen and alkyl.
2. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The R2 and R3 are hydroxyl groups.
3. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The R4 and R5 are one of H, halogen, and alkyl, and at least one of them is H, and R6 and R7 are both H.
4. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 3, characterized in that: R4, R5, R6, and R7 are all H.
5. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: R8, R9, R 10 One of them is halogen or alkyl, and the others are H, R 11 It is one of H, halogen and alkyl.
6. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The aldehyde is one or a combination of two or more of formaldehyde, paraformaldehyde, benzaldehyde, acetaldehyde, propionaldehyde and butyraldehyde.
7. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The catalyst is one or more of ammonia water, sodium hydroxide, potassium hydroxide, barium hydroxide and magnesium hydroxide.
8. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The solvent is one or more of water, ethanol, methanol, acetone, tetrahydrofuran, methane and chloroform.
9. The method for preparing boron-doped carbon microspheres with high specific surface area according to claim 1, characterized in that: The boron monomer is one or a combination of two or more of 2-hydroxyphenylboric acid, 4-hydroxyphenylboric acid, 2-aminophenylboric acid, 4-aminophenylboric acid, 3-fluoro-4-hydroxyphenylboric acid, 2-fluoro-6-hydroxyphenylboric acid, 2-fluoro-4-hydroxyphenylboric acid, 4-hydroxy-2-methylphenylboric acid, 2-fluoro-3-hydroxyphenylboric acid, 3-fluoro-5-hydroxyphenylboric acid, 3-fluoro-4-hydroxyphenylboric acid, and 2,6-difluoro-4-hydroxyphenylboric acid.
10. Boron-doped carbon microspheres prepared according to the method for preparing boron-doped carbon microspheres with high specific surface area according to any one of claims 1 to 9.