A method for preparing a phenolic resin-based mesoporous carbon based on a foaming technique

Abstract

The application belongs to the technical field of carbon material preparation, and particularly relates to a preparation method of phenolic resin-based mesoporous carbon based on foaming technology, which comprises the following steps: (1) mixing phenolic resin powder with an organic solvent, stirring until dissolution to obtain a phenolic resin precursor solution; (2) adding an acid aqueous solution into the phenolic resin precursor solution, stirring, adding an alkaline substance after the system becomes viscous, stirring at 50-87 DEG C for 2-5 h to obtain a foaming phenolic resin precursor solution; (3) solidifying to obtain a porous carbon precursor material; (4) crushing, carbonizing in an inert atmosphere to obtain carbonized material, cooling to room temperature, then performing alkali activation and water vapor activation, then soaking in an acid solution for 12-24 h, washing, drying to obtain phenolic resin-based mesoporous carbon. The prepared mesoporous carbon has a high specific surface area and a developed mesoporous pore volume.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation technology, specifically relating to a method for preparing phenolic resin-based mesoporous carbon based on foaming technology. Background Technology

[0002] Porous carbon materials possess high specific surface area, tunable pore structure, and excellent physicochemical stability, making them promising candidates for applications in cutting-edge fields such as energy storage, adsorption separation, and catalysis. Among these, carbon materials with hierarchical pore structures that combine micropores, mesopores, and macropores exhibit particularly significant advantages: the hierarchical pore structure enables synergistic function of pores at different scales, especially the mesopores of 2–50 nm, which can serve as rapid channels for mass transport, effectively reducing mass transfer resistance and improving diffusion and transport efficiency, thus being a key factor determining the material's service performance.

[0003] Currently, the construction of mesoporous structures still primarily relies on template methods, mainly including hard template methods represented by silica nanospheres and soft template methods represented by block copolymers. However, this process has inherent technical drawbacks: template raw materials are expensive, the preparation process is cumbersome and lengthy, and the template removal process relies on highly corrosive or energy-intensive methods such as hydrofluoric acid etching or high-temperature calcination. This not only significantly increases the preparation cost and process complexity but also easily causes environmental pollution, presenting significant barriers to industrial application and hindering large-scale production.

[0004] To overcome the technical bottlenecks of template-based methods, template-free preparation strategies have become a research hotspot in the field of porous carbon materials. Among them, the foaming method shows great potential for application due to its simple process, low cost, and ease of large-scale scaling. Its core principle is to utilize the bubbles generated in situ during the curing process of the polymer precursor. Through the nucleation, growth, and shaping of the bubbles, a porous structure is constructed in one step, thus avoiding many drawbacks of the traditional template method. Currently, some studies have used physical foaming agents such as supercritical fluids or thermally decomposable chemical foaming agents such as azodicarbonamide to achieve foaming and pore formation in polymer matrices. However, both of these foaming systems have obvious limitations: physical foaming has stringent requirements for equipment precision and process conditions, and the generated bubbles have poor stability and are prone to collapse; the thermal decomposition temperature of traditional chemical foaming agents is not well matched with the curing temperature of the resin precursor, which can easily lead to premature bubble escape or excessive fusion, ultimately forming open-cell or closed-cell foams with wide pore size distribution and uneven structure, making it difficult to accurately construct a multi-level regular pore structure dominated by mesopores and interconnected channels.

[0005] Phenolic resins possess advantages such as high carbon yield, good thermal stability, and strong structural tunability, making them ideal precursors for preparing high-performance porous carbon materials. However, direct carbonization of pure phenolic resins only forms a dense carbon matrix dominated by micropores, lacking mesoporous structures and exhibiting poor pore connectivity, which makes it difficult to meet the application requirements of efficient mass transfer. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing phenolic resin-based mesoporous carbon based on foaming technology. This method utilizes a specific aqueous solution containing an acidic substance to neutralize an alkali within the phenolic resin system, continuously generating CO2 as a green foaming agent. This eliminates the need for expensive template agents, allowing for the in-situ formation of abundant macropores and mesoporous frameworks during the resin curing stage. Subsequent activation steps create micropores, ultimately resulting in a hierarchical pore structure with micropores, mesopores, and macropores.

[0007] A method for preparing phenolic resin-based mesoporous carbon based on foaming technology includes the following steps: (1) Preparation of phenolic resin precursor solution: Phenolic resin powder is mixed with organic solvent and stirred until dissolved to obtain phenolic resin precursor solution; (2) Preparation of foaming phenolic resin precursor solution: A substance with an acidic aqueous solution is added to the phenolic resin precursor solution and stirred. After the system becomes viscous, an alkaline substance is added and stirred. The reaction is carried out at 50-87℃ for 2-5 h to obtain foaming phenolic resin precursor solution; wherein, the acidic substance in the aqueous solution is at least one of oxalic acid, citric acid, tartaric acid, benzoic acid, and ammonium chloride; and the alkaline substance is at least one of carbonate and bicarbonate. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is cured to obtain porous carbon precursor material; (4) Preparation of phenolic resin-based mesoporous carbon: The porous carbon precursor material is crushed and carbonized under an inert atmosphere to obtain carbonized material. After cooling to room temperature, it is activated by alkali and steam. Then, it is soaked in an acidic solution for 12-24 h, washed, and dried to obtain phenolic resin-based mesoporous carbon.

[0008] More preferably, in step (2), the alkaline substance is one or more of sodium carbonate, sodium bicarbonate, and ammonium bicarbonate.

[0009] Preferably, the mass ratio of the acidic substance in the aqueous solution to the alkaline substance is 1:(0.5-2.5); the mass ratio of the acidic substance in the aqueous solution to the phenolic resin powder is (0.8-2.2):1.

[0010] Preferably, in step (1), the organic solvent is any one of anhydrous ethanol, methanol, and N,N-dimethylformamide; the mass ratio of the organic solvent to the phenolic resin powder is (3-6):1.

[0011] Preferably, in step (3), the curing is carried out by step curing, first curing at 80-90℃ for 2-4 h, and then curing at 90-130℃ for 3-8 h.

[0012] Preferably, the carbonization is performed at 600-800℃ for 2-4 hours.

[0013] Preferably, the alkali activation involves mixing the carbonized material with an alkali and activating it at an inert atmosphere and 700-950°C for 1-2 hours, wherein the mass ratio of the alkali to the carbonized material is (0.5-2):1. More preferably, the alkali is KOH.

[0014] More preferably, the steam activation is to maintain the temperature of alkali activation by introducing steam for 0.5-1.5 h, and the mass ratio of steam to carbonized material is (1-4):1.

[0015] Preferably, the acidic solution is a 0.5-3 mol / L dilute hydrochloric acid solution.

[0016] Preferably, the inert gas is N2 or Ar.

[0017] Preferably, the heating rate during carbonization is 1-5°C / min.

[0018] This invention does not simply follow the traditional physical or thermal decomposition foaming approach, but creatively designs a new foaming strategy of "simultaneous and coordinated in-situ chemical reaction and polymerization crosslinking". This strategy utilizes a specific aqueous acidic substance to neutralize an alkaline carbonate (bicarbonate) in a phenolic resin system, continuously generating CO2 as a green foaming agent. Through sequential control of "first thickening, then foaming", the acidic aqueous substance is first used as a catalyst to induce prepolymerization and crosslinking of the phenolic resin, significantly increasing the system viscosity and forming a polymer network with initial strength. This step provides crucial "skeleton" support for subsequent bubble nucleation, growth, and stabilization, effectively preventing bubble coalescence and collapse. The acid-base neutralization reaction rate can be flexibly controlled by the type, concentration, and temperature of the reactants to achieve a good match with the resin curing rate, ensuring that bubbles are effectively captured and fixed within the "time window" of resin gelation.

[0019] Advantages of this invention: 1. Simple process and low cost: This invention utilizes an acidic substance in the aqueous solution to increase the viscosity of the system, and then uses the CO2 gas generated by the acid-base neutralization reaction as a green foaming agent. It eliminates the need for expensive template agents, simplifies the process, and reduces production costs. 2. Precise and controllable pore structure: By adjusting the type and ratio of acidic or alkaline substances in the aqueous solution and the reaction conditions, the foaming process can be precisely controlled, thereby forming a rich macroporous and mesoporous framework in situ during the resin curing stage. Combined with subsequent activation energy, micropores are created, ultimately forming a perfect microporous-mesoporous-macroporous hierarchical structure. 3. Excellent material properties: The obtained porous carbon materials have high specific surface area, well-developed mesopore volume and suitable surface chemical properties, exhibiting excellent performance in fields such as supercapacitors and adsorption. Attached Figure Description

[0020] Figure 1 This is a transmission electron microscope image of Example 2. Detailed Implementation

[0021] Example 1: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 30 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foamed phenolic resin precursor solution: 8 g of oxalic acid was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 4 g of sodium bicarbonate powder was added to it immediately. At this time, a large number of fine bubbles were immediately observed to be generated. The temperature was raised to 50°C and the reaction was stirred for 2 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foamed phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 80°C for 2 h, then cured at 90°C for 3 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 600℃ at a heating rate of 1℃ / min and carbonize it at a constant temperature for 2 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 0.5:1, under nitrogen atmosphere protection, heat it to 700℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 1 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced at the mass ratio of water vapor to carbonized material of 1:1, and the alkali activation temperature is maintained for 0.5 h. Then, it is soaked in 0.5 mol / L dilute hydrochloric acid solution for 12 hours, with intermittent stirring during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0022] Example 2: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 60 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foamed phenolic resin precursor solution: 22 g of citric acid was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 55 g of sodium bicarbonate powder was added to it immediately. At this time, a large number of fine bubbles were immediately observed to be generated. The temperature was raised to 87°C and the reaction was stirred for 5 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foamed phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 90°C for 4 h, then cured at 130°C for 8 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 800℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 4 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 2:1, under nitrogen atmosphere protection, heat it to 950℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 2 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced according to the mass ratio of water vapor to carbonized material of 4:1, and the alkali activation temperature is maintained for 1.5 h. Then, it is soaked in 3 mol / L dilute hydrochloric acid solution for 24 hours, with intermittent stirring during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0023] Transmission electron microscopy analysis was performed on the phenolic resin-based mesoporous carbon, and the results are shown in the figure. Figure 1In the microstructure image with a scale bar of 10 nm, the dark areas represent thin-walled carbon frameworks, while the numerous alternating light and dark cavities are mesoporous channels left over from the foaming bubble template and subsequently formed through activation and pore expansion. These pores are densely packed and interconnected. During the foaming stage, acid-base neutralization generates CO2 bubbles in situ, which act as templates. This stretches the resin to form thin-walled carbon walls, causing the carbon wall molecular chains to oriented. After carbonization / activation, abundant mesopores are generated inside, significantly shortening the diffusion path of the activator and improving pore-forming efficiency. This process does not require an external hard template, is low-cost, and easy to operate. The well-developed and interconnected mesoporous network can accelerate ion transport, making it suitable for applications such as energy storage electrodes and composite supports.

[0024] Example 3: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 45 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foamed phenolic resin precursor solution: 10 g of ammonium chloride was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 15 g of sodium bicarbonate powder was added to it immediately. At this time, a large number of fine bubbles were observed to be generated. The temperature was raised to 60°C and the reaction was stirred for 3 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foamed phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 85°C for 2 h, then cured at 110°C for 5 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 700℃ at a heating rate of 2℃ / min and carbonize it at a constant temperature for 2 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 1:1, under nitrogen atmosphere protection, heat it to 800℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 2 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced according to the mass ratio of water vapor to carbonized material of 2:1, and the alkali activation temperature is maintained for 1 h. Then, it is soaked in 1 mol / L dilute hydrochloric acid solution for 12 hours, with intermittent stirring during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0025] Example 4: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 40 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foamed phenolic resin precursor solution: 15 g of benzoic acid was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 20 g of ammonium bicarbonate powder was added to it immediately. At this time, a large number of fine bubbles were observed to be generated. The temperature was raised to 65°C and the reaction was stirred for 2.5 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foamed phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 80°C for 4 h, then cured at 100°C for 8 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 750℃ at a heating rate of 2℃ / min and carbonize it at a constant temperature for 2 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 0.8:1, under nitrogen atmosphere protection, heat it to 850℃ at a heating rate of 5℃ / min and hold it at a constant temperature for 1.5 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced at the mass ratio of water vapor to carbonized material of 3.1:1, and the alkali activation temperature is maintained for 0.9 h. Then, it is soaked in 2 mol / L dilute hydrochloric acid solution for 12 hours, with intermittent stirring during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0026] Example 5: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 50 g of methanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foaming phenolic resin precursor solution: 13 g of tartaric acid was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 23 g of sodium carbonate powder was added to it immediately. At this time, a large number of fine bubbles were immediately observed to be generated. The temperature was raised to 72°C and stirred for 4 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foaming phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 87°C for 3 h, then cured at 95°C for 6 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 780℃ at a heating rate of 2℃ / min and carbonize it at a constant temperature for 2.5 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 1.2:1, under nitrogen atmosphere protection, heat it to 800℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 1 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced at the mass ratio of water vapor to carbonized material of 1.3:1 and the alkali activation temperature is maintained for 1.2 h. Then, it is soaked in 1.5 mol / L dilute hydrochloric acid solution for 20 hours, with intermittent stirring during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0027] Example 6: A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, comprising the following steps: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 55 g of N,N-dimethylformamide and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of foamed phenolic resin precursor solution: 17 g of citric acid was slowly added to the phenolic resin precursor solution. The solution color was observed to gradually darken. The system was stirred until it became viscous and the surface of the liquid showed lines that were not easy to disappear, indicating that the prepolymer crosslinking had reached a suitable viscosity. Then, 34 g of sodium bicarbonate powder was added to it immediately. At this time, a large number of fine bubbles were immediately observed to be generated. The temperature was raised to 83°C and the reaction was stirred for 2.3 h to allow the foaming and polycondensation reactions to proceed fully. After the reaction was completed, a brown, viscous foamed phenolic resin precursor solution filled with fine bubbles was obtained. (3) Preparation of porous carbon precursor material: The foamed phenolic resin precursor liquid is poured into a polytetrafluoroethylene mold, transferred to a forced-air drying oven, cured at 80°C for 2.5 h, then cured at 103°C for 8 h, and after natural cooling, a porous carbon precursor material is obtained, which is a hard and brittle brown foam solid. (4) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 800℃ at a heating rate of 2℃ / min and carbonize it at a constant temperature for 1.5 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 0.9:1, under nitrogen atmosphere protection, heat it to 850℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 1 h to complete the alkali activation. Subsequently, under nitrogen protection, water vapor is introduced at the mass ratio of water vapor to carbonized material of 2.5:1 and the alkali activation temperature is maintained for 1 h. Then, it is soaked in 1.8 mol / L dilute hydrochloric acid solution for 16 hours, with intermittent stirring during the period to ensure that metal ions and residual alkali are fully removed. Then, it is repeatedly washed with deionized water until the filtrate is neutral. Finally, it is vacuum dried at 110℃ for 12 h to obtain phenolic resin-based mesoporous carbon.

[0028] Comparative Example 1: Carbon materials were prepared by adding only acidic substances to the aqueous solution, without adding alkaline substances, as follows: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 60 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution; 22 g of citric acid was slowly added to the phenolic resin precursor solution, and the temperature was raised to 87℃ and stirred for 5 h. It was observed that the solution color gradually deepened to a dark yellow viscous state. (2) Preparation of porous carbon precursor material: Pour the phenolic resin precursor liquid into a polytetrafluoroethylene mold, transfer it to a forced-air drying oven, first cure at 90℃ for 4 h, then cure at 130℃ for 8 h, and after natural cooling, obtain porous carbon precursor material, which is a hard brown solid. (3) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 800℃ at a heating rate of 2℃ / min and carbonize it at a constant temperature for 4 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 2:1, under nitrogen atmosphere protection, heat it to 950℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 2 h to complete the alkali activation. Then, under nitrogen protection, activate it for 1.5 h according to the mass ratio of water vapor to carbonized material of 4:1. Then, soak it in 3 mol / L dilute hydrochloric acid solution for 24 hours, stirring intermittently during the soaking period to ensure that metal ions and residual alkali are fully removed. Then, wash it repeatedly with deionized water until the filtrate is neutral. Finally, dry it under vacuum at 110℃ for 12 h to obtain phenolic resin-based porous carbon.

[0029] Comparative Example 2: Carbon materials were prepared by adding only alkaline substances, without adding any acidic substances to the aqueous solution, as follows: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 60 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution; then 55 g of sodium bicarbonate powder was added to it, and the temperature was raised to 87℃ and stirred for 5 h to obtain a brown phenolic resin precursor solution. (2) Preparation of porous carbon precursor material: Pour the phenolic resin precursor liquid into a polytetrafluoroethylene mold, transfer it to a forced-air drying oven, first cure at 90℃ for 4 h, then cure at 130℃ for 8 h, and after natural cooling, obtain porous carbon precursor material, which is a hard brown solid. (3) Preparation of phenolic resin-based mesoporous carbon: Weigh 2.0 g of pulverized porous carbon precursor material, place it in a porcelain boat, put it in a tube furnace, and under nitrogen atmosphere, heat it to 800℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 4 h. After natural cooling to room temperature, a preliminary black carbonized material is obtained. Then, according to the mass ratio of KOH to carbonized material of 2:1, under nitrogen atmosphere protection, heat it to 950℃ at a heating rate of 5℃ / min and carbonize it at a constant temperature for 2 h to complete the alkali activation. Then, under nitrogen protection, activate it for 1.5 h according to the mass ratio of water vapor to carbonized material of 4:1. Then soak it in 3 mol / L dilute hydrochloric acid solution for 24 hours, stirring intermittently during the soaking period to ensure that metal ions and residual alkali are fully removed. Then wash it repeatedly with deionized water until the filtrate is neutral. Finally, vacuum dry it at 110℃ for 12 h to obtain phenolic resin-based porous carbon.

[0030] Comparative Example 3: Carbon materials were prepared without adding any acidic or alkaline substances to the aqueous solution, as detailed below: (1) Preparation of phenolic resin precursor solution: 10.0 g of thermoplastic phenolic resin powder (softening point 85℃) was mixed with 60 g of anhydrous ethanol and stirred at room temperature to obtain a yellow, clear and transparent phenolic resin precursor solution. (2) Preparation of porous carbon precursor material: Pour the phenolic resin precursor liquid into a polytetrafluoroethylene mold, transfer it to a forced-air drying oven, first cure at 90℃ for 4 h, then cure at 130℃ for 8 h, and after natural cooling, obtain porous carbon precursor material, which is a hard brown solid. (3) Preparation of phenolic resin-based mesoporous carbon: 2.0 g of pulverized porous carbon precursor material was weighed, placed in a porcelain boat, and placed in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 800℃ at a heating rate of 5℃ / min and held at that temperature for 4 h. After natural cooling to room temperature, a preliminary black carbonized material was obtained. Then, under a nitrogen atmosphere, the temperature was increased to 950℃ at a mass ratio of KOH to carbonized material of 2:1 and held at that temperature for 2 h to complete alkali activation. Subsequently, under a nitrogen atmosphere, the material was activated for 1.5 h with a mass ratio of water vapor to carbonized material of 4:1. Then, the material was soaked in a 3 mol / L dilute hydrochloric acid solution for 24 hours with intermittent stirring to ensure thorough removal of metal ions and residual alkali. The material was then repeatedly washed with deionized water until the filtrate was neutral. Finally, the material was vacuum dried at 110℃ for 12 h to obtain phenolic resin-based porous carbon.

[0031] Performance testing The carbon materials described above were characterized, and the results are shown in Table 1. Table 1 Characterization Results .

[0032] It can be seen that the mesopore volume and mesopore ratio of the carbon material prepared by this invention are better than those of the three comparative examples, which irrefutably proves that the foaming technology is the core and key to constructing the mesoporous structure. All embodiments use acidic substances (oxalic acid, citric acid, ammonium chloride, benzoic acid, tartaric acid, etc.) and alkaline inorganic salts (sodium bicarbonate, sodium carbonate or ammonium bicarbonate) to undergo a neutralization reaction in the resin precursor, releasing CO2 gas in situ. Since the reaction is carried out when the system reaches a suitable viscosity, the bubbles are stably encapsulated and gradually expand to form an interconnected foam structure. This process has three major advantages: (1) Bubble template effect: The space occupied by the bubbles in the resin becomes a cavity of macropore / mesopore scale after solidification, and the bubble wall becomes the reaction interface for subsequent carbonization and activation. (2) Pore wall thinning: The foaming process transforms the resin skeleton from a dense block into a thin-walled foam, which significantly shortens the diffusion distance of the activator (KOH, water vapor) in the solid and improves the activation efficiency. (3) Mesoporous orientation: The bubble wall itself is subjected to bidirectional stretching during the foaming process, and the molecular chains are oriented and aligned. After carbonization, it is easy to form mesoporous channels of 2-50 nm in the wall. Therefore, the mesoporous pore volume of all embodiments exceeds the microporous pore volume, and the mesoporous ratio is generally greater than 60%. Although the comparative examples also underwent joint activation, due to the lack of foaming (only acid or only alkali or no foaming agent was added), the precursor was dense or contained only isolated pores, and the activator was difficult to penetrate evenly. The pore structure was mainly micropores, and the mesoporous pore volume was extremely low. The total pore volume and specific surface area were much lower than those of the examples.

[0033] Compared to template methods (such as mesoporous silicon templates), this method eliminates the need for dangerous and costly template etching, making it economical and environmentally friendly. The resulting mesoporous carbon can be directly used as an electrode material or as a highly efficient carrier for sulfur, metal oxides, etc., making it suitable for next-generation high-energy / high-power energy storage systems.

[0034] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing phenolic resin-based mesoporous carbon based on foaming technology, characterized in that: Includes the following steps: (1) Mix phenolic resin powder with an organic solvent and stir until dissolved to obtain a phenolic resin precursor solution; (2) Add an acidic aqueous solution to the phenolic resin precursor solution, stir, and after the system becomes viscous, add an alkaline substance and stir. Stir and react at 50-87℃ for 2-5 h to obtain a foaming phenolic resin precursor solution; wherein, the acidic aqueous solution is at least one of oxalic acid, citric acid, tartaric acid, benzoic acid, and ammonium chloride; and the alkaline substance is at least one of carbonate and bicarbonate. (3) The foamed phenolic resin precursor liquid is cured to obtain a porous carbon precursor material; (4) The porous carbon precursor material is crushed and carbonized under an inert atmosphere to obtain carbonized material. After cooling to room temperature, it is activated by alkali and steam. Then it is soaked in an acidic solution for 12-24 h, washed, and dried to obtain phenolic resin-based mesoporous carbon.

2. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The alkaline substance is sodium carbonate, sodium bicarbonate, or ammonium bicarbonate.

3. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The mass ratio of the acidic substance to the alkaline substance in the aqueous solution is 1:(0.5-2.5); the mass ratio of the acidic substance to the phenolic resin powder in the aqueous solution is (0.8-2.2):

1.

4. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: In step (1), the organic solvent is any one of anhydrous ethanol, methanol, and N,N-dimethylformamide; the mass ratio of the organic solvent to the phenolic resin powder is (3-6):

1.

5. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: In step (3), the curing is carried out in a stepped curing manner, first curing at 80-90℃ for 2-4 h, and then curing at 90-130℃ for 3-8 h.

6. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The carbonization is carried out at 600-800℃ for 2-4 hours.

7. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The alkali activation involves mixing the carbonized material with an alkali and activating it at an inert atmosphere and 700-950℃ for 1-2 hours. The mass ratio of the alkali to the carbonized material is (0.5-2):

1.

8. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The steam activation involves maintaining the temperature used for alkali activation by introducing steam for 0.5-1.5 hours, with the mass ratio of steam to carbonized material being (1-4):

1.

9. The method for preparing phenolic resin-based mesoporous carbon based on foaming technology according to claim 1, characterized in that: The acidic solution is a 0.5-3 mol / L dilute hydrochloric acid solution.

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