Method for regulating and controlling pore structure of porous carbon through gas phase activation and etching

Abstract

The invention discloses a method for regulating and controlling a porous structure of porous carbon through gas phase activation and etching. The method comprises the following steps: S1, selecting a carbon precursor material; s2, performing carbonization treatment on the selected carbon precursor material to obtain a carbonized material; s3, after carbonization is completed, introducing activation gas and etching gas to perform gas-phase activation and etching treatment on the carbonized material so as to regulate and control the porosity, aperture and specific surface area of porous carbon; the activation gas is one or more of water vapor and carbon dioxide, the etching gas is oxygen, the volume of the introduced etching gas is 0.1%-10% of the volume of the activation gas, and the oxygen is introduced as the etching gas on the basis of the activation gas. The activated gas is mainly responsible for forming a basic pore structure, the oxygen is used as the etching gas, the reaction activity is higher, the surface of the carbonized material and the preliminarily formed pore wall can be selectively etched, and therefore the pore diameter is further regulated and controlled.

Description

Technical Field

[0001] This invention relates to the field of porous carbon material preparation technology, and in particular to a method for controlling the pore structure of porous carbon through gas-phase activation and etching. Background Technology

[0002] Porous carbon materials, due to their high specific surface area, well-developed pore structure, good chemical stability, and excellent electrical conductivity, have wide applications in supercapacitors, adsorption separation, catalysis, and energy storage. The pore structure parameters of porous carbon, such as porosity, pore size distribution, and specific surface area, directly determine its performance and application effects. Therefore, developing methods to precisely control the pore structure of porous carbon has significant scientific and practical value.

[0003] Currently, the main methods for preparing porous carbon include physical activation and chemical activation. Physical activation typically involves activating the carbonized material at high temperatures with activating gases such as CO2 or steam, removing some carbon through a gasification reaction to form pores. Chemical activation involves adding chemical activators (such as KOH, ZnCl2, H3PO4, etc.) before or during carbonization, followed by high-temperature activation treatment to form a porous structure.

[0004] However, traditional physical activation methods are difficult to control during the activation process and lack precision in pore structure regulation, often resulting in a wide pore size distribution, making it difficult to obtain porous carbon with a specific pore size distribution. While chemical activation methods can yield porous carbon with high specific surface area, chemical activators are highly corrosive, difficult to remove through subsequent washing, and environmentally unfriendly. Furthermore, activator residues may affect the performance of the porous carbon.

[0005] In recent years, some studies have attempted to optimize pore structures by combining different activation gases or processes. However, precisely controlling porosity, pore size, and specific surface area, especially achieving fine control of pore size, remains a challenge in the preparation of porous carbon materials. For example, using water vapor or CO2 alone for activation has limited reactivity and selectivity, making it difficult to meet the requirements for precise pore structure design. Introducing a small amount of oxygen as an etching gas results in a more vigorous reaction with carbon materials. Balancing the effects of activation and etching, avoiding excessive etching that could lead to pore structure collapse or a decrease in specific surface area, and achieving precise control of the pore structure are technical problems that need to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the porous carbon structure through vapor phase activation and etching, so as to solve the problems mentioned in the background art, such as the difficulty of accurately controlling porosity, pore size and specific surface area in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for controlling porous carbon pore structure through vapor phase activation and etching, the method comprising the following steps: S1. Select carbon precursor materials; S2. The selected carbon precursor material is carbonized to obtain carbonized material; S3. After carbonization is completed, activation gas and etching gas are introduced to perform gas phase activation and etching treatment on the carbonized material to control the porosity, pore size and specific surface area of ​​the porous carbon. The activating gas is one or more of water vapor and carbon dioxide, the etching gas is oxygen, and the volume of the etching gas introduced is 0.1% to 10% of the volume of the activating gas.

[0008] Preferably, in step S1, the selected carbon precursor material is one or more of biomass materials, polymers, or asphalt.

[0009] Preferably, the biomass material is one or more of coconut shell, walnut shell, wood chips, straw or bamboo, and the polymer is one or more of phenolic resin and polyacrylonitrile.

[0010] Preferably, in step S2, the carbonization temperature is 400~800℃ and the carbonization time is 30~120min.

[0011] Preferably, in step S3, the activation gas and etching gas are mixed and then introduced, or introduced sequentially.

[0012] Preferably, the temperature of the vapor phase activation and etching process is 700~1000℃.

[0013] Preferably, the time for the vapor phase activation and etching process is 30~180 min.

[0014] Preferably, the volumetric flow rate of the activating gas to the mass ratio of the carbonized material is 50~500 mL / min·g.

[0015] Preferably, the volume of the etching gas introduced is 0.5% to 5% of the volume of the activation gas.

[0016] The beneficial effects of this invention are: 1. This invention introduces oxygen within a specific range as an etching gas, based on an activating gas (water vapor, CO2). The activating gas is mainly responsible for forming the basic pore structure, while oxygen, as an etching gas, has higher reactivity and can selectively etch the surface of the carbide and the initially formed pore walls, thereby achieving further control over the pore size, such as enlarging the pore size, adjusting the pore size distribution, and increasing porosity and specific surface area.

[0017] 2. By combining activating gases such as water vapor and CO2 with a specific ratio of oxygen etching gas, the porous structure of carbon can be controlled after carbonization. In particular, by controlling the oxygen content within the range of 0.1% to 10%, the etching effect can be utilized to control the pore size, while avoiding excessive etching that could damage the material structure.

[0018] 3. By precisely controlling the pore structure, porous carbon materials with specific pore size distribution and high specific surface area can be obtained, thereby significantly improving their application performance in fields such as supercapacitors (e.g., high power density, high energy density), adsorption separation (e.g., specific molecular sieving), and catalysis (e.g., active site exposure). Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the steps of preparing porous carbon structures through vapor phase activation and etching according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 A method for controlling porous carbon pore structure through vapor phase activation and etching, the method comprising the following steps: S1. Select carbon precursor materials; S2. The selected carbon precursor material is carbonized to obtain carbonized material; S3. After carbonization is completed, activation gas and etching gas are introduced to perform gas phase activation and etching treatment on the carbonized material to control the porosity, pore size and specific surface area of ​​the porous carbon. The activating gas is one or more of water vapor and carbon dioxide, the etching gas is oxygen, and the volume of the etching gas introduced is 0.1% to 10% of the volume of the activating gas.

[0022] Specifically, by introducing 0.1% to 10% oxygen as an etching gas on the basis of an activating gas (water vapor, CO2), the activating gas is mainly responsible for forming the basic pore structure, while oxygen, as an etching gas, has higher reactivity and can selectively etch the surface of the carbide and the initially formed pore walls, thereby achieving further control over the pore size, such as enlarging the pore size, adjusting the pore size distribution, and increasing the porosity and specific surface area.

[0023] Specifically, in step S1, the selected carbon precursor material is one or more of biomass materials, polymers, or asphalt.

[0024] Specifically, the biomass material is one or more of coconut shells, walnut shells, wood chips, straw, or bamboo, and the polymer is one or more of phenolic resin and polyacrylonitrile.

[0025] Specifically, in step S2, the carbonization temperature is 400~800℃ and the carbonization time is 30~120min.

[0026] Specifically, in step S3, the activation gas and the etching gas are mixed and then introduced, or introduced sequentially.

[0027] Specifically, the temperature for the vapor phase activation and etching process is 700~1000℃.

[0028] Specifically, the time for the vapor phase activation and etching process is 30~180 min.

[0029] Specifically, the volumetric flow rate of the activating gas to the mass ratio of the carbonized material is 50~500 mL / min·g.

[0030] Specifically, the volume of the etching gas introduced is 0.5% to 5% of the volume of the activation gas.

[0031] Specifically, after preparing porous carbon structures through vapor phase activation and etching, the process also includes cooling, washing, and drying.

[0032] Example 1: S1. Select biomass material (coconut shell) as carbon precursor material. After crushing, washing and drying the coconut shell, carbon precursor is prepared.

[0033] S2. The prepared carbon precursor material is placed in a tube furnace and heated to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere. The temperature is held for 60 min and then naturally cooled to room temperature to obtain the carbonized material.

[0034] S3. After carbonization, under a nitrogen atmosphere, the temperature is increased to 850℃ at a heating rate of 5℃ / min. Then, the gas is switched to a mixture of activation gas (water vapor) and etching gas (oxygen), with a water vapor volume flow rate of 200 mL / min and an oxygen volume flow rate of 2 mL / min (i.e., oxygen is 1% of the water vapor volume content), for a total gas flow rate of 202 mL / min. This condition is maintained for 90 min of activation. After activation, the activation gas is stopped, and the mixture is allowed to cool naturally to room temperature under a nitrogen atmosphere. The obtained product is repeatedly washed with deionized water until neutral, and then dried at 105℃ for 12 hours to obtain the final porous carbon sample.

[0035] The porous carbon sample of Example 1 was tested using the gas adsorption method to obtain pore structure parameters. The specific surface area of ​​the porous carbon was 1850 m² / g, the total pore volume was 0.95 cm³ / g, and the average pore size was 2.1 nm. The pore size distribution was mainly concentrated in the micropore and mesopore range, as shown in Table 1.

[0036] Table 1 parameter numerical values Specific surface area (SSA) 1850m² / g Total Pore Volume 0.95cm³ / g Average pore size 2.1nm Main aperture range Micropores + Mesopores Example 2: This example is basically the same as Example 1, except that in step S3, carbon dioxide is used as the activation gas, the volumetric flow rate of carbon dioxide is 150 mL / min, the volumetric flow rate of oxygen is 4.5 mL / min (that is, the volumetric content of oxygen relative to carbon dioxide is 3%), the activation temperature is 900℃, and the activation time is 120 min.

[0037] The porous carbon sample of Example 2 was tested using the gas adsorption method. The specific surface area of ​​the porous carbon was 2100 m² / g, the total pore volume was 1.10 cm³ / g, the average pore size was 2.5 nm, and the proportion of mesopores was increased.

[0038] Example 3: This example is basically the same as Example 1, except that in step S3, the activating gas is a mixture of water vapor and carbon dioxide (volume ratio of 1:1), the total mixed gas flow rate is 180 mL / min, the oxygen volume flow rate is 0.9 mL / min (i.e. the oxygen content relative to the total volume of the activating gas is 0.5%), the activation temperature is 750℃, and the activation time is 60 min.

[0039] The porous carbon sample of Example 3 was tested using the gas adsorption method. The porous carbon had a specific surface area of ​​1500 m² / g, a total pore volume of 0.80 cm³ / g, an average pore size of 1.8 nm, and micropores were the dominant component.

[0040] Example 4: This example is basically the same as Example 1, except that in step S3, the volumetric flow rate of oxygen is 20 mL / min (i.e., the volumetric content of oxygen relative to water vapor is 10%), the activation temperature is 850℃, and the activation time is 90 min.

[0041] The porous carbon sample of Example 4 was tested using the gas adsorption method. The specific surface area of ​​the porous carbon was 1200 m² / g, the total pore volume was 1.20 cm³ / g, the average pore size was 4.0 nm, the pore size distribution was widened, and some pore structures may have collapsed due to excessive etching.

[0042] Example 5: This example is basically the same as Example 1, except that in step S3, the volumetric flow rate of oxygen is 0.2 mL / min (i.e., the volumetric content of oxygen relative to water vapor is 0.1%), the activation temperature is 850℃, and the activation time is 90 min.

[0043] The porous carbon sample of Example 5 was tested using the gas adsorption method. The specific surface area of ​​the porous carbon was 1700 m² / g, the total pore volume was 0.85 cm³ / g, and the average pore diameter was 2.0 nm. The pore structure regulation effect was not significant compared with Example 1, and was close to the result of single water vapor activation.

[0044] Comparative Example 1: This comparative example is basically the same as Example 1, except that in step S3, oxygen is not introduced, only water vapor is introduced, the volume flow rate is 200 mL / min, the activation temperature is 850℃, and the activation time is 90 min.

[0045] The porous carbon sample of Comparative Example 1 was tested using the gas adsorption method. The specific surface area of ​​the porous carbon was 1600 m² / g, the total pore volume was 0.75 cm³ / g, the average pore size was 1.8 nm, the pore size distribution was narrow, the proportion of mesopores was low, and the specific surface area and pore volume were both lower than those of Example 1.

[0046] As can be seen from the above embodiments and comparative examples, the present invention, by introducing oxygen within a specific content range as an etching gas, works synergistically with the activation gas to effectively control the porosity, pore size, and specific surface area of ​​porous carbon. When the oxygen content is too low (as in Example 5), the etching effect is not obvious, and the control effect is limited; when the oxygen content is too high (as in Example 4), it may lead to over-etching, destroying the pore structure and reducing the specific surface area; while within the oxygen content range specified by the present invention (0.1%~10%, preferably 0.5%~5%), porous carbon materials with optimized pore structure and excellent performance can be obtained.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling pore structure of porous carbon by gas phase activation and etching, characterized in that, The method includes the following steps: S1. Select carbon precursor materials; S2. The selected carbon precursor material is carbonized to obtain carbonized material; S3. After carbonization is completed, activation gas and etching gas are introduced to perform gas phase activation and etching treatment on the carbonized material to control the porosity, pore size and specific surface area of ​​the porous carbon. The activating gas is one or more of water vapor and carbon dioxide, the etching gas is oxygen, and the volume of the etching gas introduced is 0.1% to 10% of the volume of the activating gas.

2. The method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1, characterized in that, In step S1, the selected carbon precursor material is one or more of biomass materials, polymers, or asphalt.

3. The method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 2, characterized in that, The biomass material is one or more of coconut shells, walnut shells, wood chips, straw, or bamboo, and the polymer is one or more of phenolic resin and polyacrylonitrile.

4. The method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1, characterized in that, In step S2, the carbonization temperature is 400~800℃ and the carbonization time is 30~120min.

5. The method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1, characterized in that, In step S3, the activation gas and the etching gas are mixed and then introduced, or introduced sequentially.

6. A method for controlling porous carbon pore structure through vapor-phase activation and etching according to claim 1 or 5, characterized in that, The temperature for the vapor phase activation and etching process is 700~1000℃.

7. A method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1 or 5, characterized in that, The time for the vapor phase activation and etching process is 30~180 min.

8. A method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1 or 5, characterized in that, The volumetric flow rate of the activating gas to the mass ratio of the carbonized material is 50~500 mL / min·g.

9. The method for controlling porous carbon pore structure through vapor phase activation and etching according to claim 1, characterized in that, The volume of the etching gas introduced is 0.5% to 5% of the volume of the activation gas.

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