A high-porosity high-uniform stable carbon material pore volume standard substance and a preparation method thereof

Abstract

This invention belongs to the field of standard material technology, and relates to a high-porosity, highly uniform, and stable carbon material pore volume standard material and its preparation method. Using resorcinol and formaldehyde as raw materials, polydiallyldimethylammonium chloride as a soft template agent, and sodium carbonate and ammonia as catalysts, a uniform RF resin gel with a templated mesoscopic structure is prepared through segmented temperature-controlled sol-gel polymerization. The complete pore structure is preserved by supercritical CO2 drying. Then, the pore structure is directionally controlled through a precisely proportioned potassium hydroxide activator and a segmented programmed temperature-increasing carbonization process. Finally, pure carbon-based pore volume standard material is obtained through acid washing, water washing, and vacuum drying purification. This invention solves the technical problems of matrix effect in existing inorganic standard materials, low pore volume, and poor uniformity and stability in carbon-based standard materials. It fills the gap in high-porosity carbon-based metrological standard materials, exhibits good matrix matching and stable performance, and can be widely used for calibration of instruments for detecting high-porosity porous carbon materials, verification of detection methods, and traceability of data values.

Description

Technical Field

[0001] This invention belongs to the field of standard material technology, and specifically provides a high-pore-volume, highly uniform and stable carbon material pore-volume standard material and its preparation method. Background Technology

[0002] Porous carbon materials, with their excellent specific surface area, tunable pore structure, and good chemical stability, are widely used in supercapacitors, gas adsorption and separation, industrial catalysis, water treatment and other fields. Pore volume parameter is the core indicator for characterizing the adsorption performance and energy storage performance of porous carbon materials, and its accurate detection is crucial for material performance evaluation and industrial production quality control.

[0003] Standard reference materials serve as core metrological benchmarks for instrument calibration, method validation, and data traceability. Their homogeneity, long-term stability, and matrix compatibility are crucial indicators for ensuring accurate, reliable, and traceable test data. Currently, most commercially available pore volume standard reference materials are based on inorganic oxide matrices such as alumina and silica. These inorganic standard reference materials differ significantly from porous carbon materials in surface chemistry, pore adsorption forces, and interfacial wettability. This leads to severe matrix effects during testing, easily causing systematic deviations in carbon material pore volume detection and failing to meet the demands of high-precision testing.

[0004] Compared to inorganic reference materials, carbon-based reference materials can perfectly match the matrix characteristics of porous carbon materials, completely eliminating matrix effects. However, there are currently very few types of carbon-based pore volume reference materials on the market, and they generally suffer from low pore volumes (typically <0.5 cm³ / g), making them unsuitable for the current testing and calibration needs of high-pore volume porous carbon materials. In addition, high-pore volume carbon materials prepared by conventional processes generally suffer from poor batch uniformity, easy collapse of pore structure during long-term storage, and large performance fluctuations due to the strong disorder of activation etching and unstable framework structure, failing to meet the uniformity and stability requirements of metrological grade reference materials.

[0005] Therefore, how to overcome the inherent defects of high-porosity carbon materials in terms of uniformity and stability while retaining the matching advantages of pure carbon matrix, and prepare carbon material pore volume standard materials with high pore volume, high batch uniformity and high long-term storage stability, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention addresses the numerous shortcomings of the aforementioned technologies by providing a high-pore-volume, highly uniform, and stable carbon material pore-volume standard and its preparation method. Using resorcinol and formaldehyde as raw materials, polydiallyldimethylammonium chloride as a soft template agent, and a composite system of sodium carbonate and ammonia as a catalyst, a uniform RF resin gel with a templated mesoscopic structure is prepared through segmented temperature-controlled sol-gel polymerization. The intact pore structure is preserved by supercritical CO2 drying. Then, the pore structure is directionally controlled through a precisely proportioned potassium hydroxide activator and a segmented programmed temperature carbonization process. Finally, the pure carbon-based pore-volume standard is obtained through acid washing, water washing, and vacuum drying purification. This standard uses amorphous cross-linked carbon as the matrix, has a carbon content >99%, and a pore volume range of 0.62–1.78 cm⁻¹. 3 / g, pore size concentrated in the range of 2–20 nm, batch internal pore volume test RSD < 2%, pore volume fluctuation < ± 0.03 cm³ after 6 months of sealed storage at room temperature. 3 / g. The above solution solves the technical problems of matrix effect in existing inorganic standard materials, low pore volume, and poor uniformity and stability of carbon-based standard materials. It fills the gap in high-pore-volume carbon-based metrological standard materials, has good matrix matching and stable performance, and can be widely used for calibration of testing instruments, verification of testing methods and traceability of data values ​​for high-pore-volume porous carbon materials.

[0007] The main features of this invention are: the polydiallyldimethylammonium chloride (PDADMAC) soft template undergoes thermal decomposition during carbonization to form regular mesoscopic channels, which synergistically construct a hierarchical porous structure with potassium hydroxide activation and pore formation; the sodium carbonate-ammonia composite catalyst enables precise staged control of the polymerization reaction, ensuring a highly regular and uniform precursor structure; more specifically: 1. Synergistic Pore-Building Mechanism of Soft Template and Activator: PDADMAC, as a strong cationic polyelectrolyte, can self-assemble with RF prepolymer through electrostatic interactions during the sol-gel process, forming a templated mesoscopic structure in the gel network. During carbonization, the thermal decomposition of PDADMAC leaves behind regular mesoscopic channels (pore sizes concentrated in the 2–20 nm range); simultaneously, potassium hydroxide activation chemically etches the carbon framework, forming micro / mesoporous structures. The two mechanisms complement each other in pore size range and synergistically enhance pore volume: the template creates mesopores to ensure a high upper limit of pore volume, while activation creates micro / mesopores to further enrich the pore structure, jointly constructing a hierarchical porous structure and achieving a significant increase in pore volume (0.62–1.78 cm⁻¹). 3 / g). This dual pore-forming strategy of "soft template + chemical activation" for the preparation of standard substances is a first in the field.

[0008] 2. Staged Polymerization Control with Composite Catalysts: Traditional RF aerogel preparation often uses sodium carbonate as a single catalyst, whose fixed catalytic activity makes it difficult to precisely control the entire polymerization process. This invention employs a sodium carbonate + ammonia dual-component composite catalytic system: ammonia plays a catalytic role in the low-temperature stage, promoting gel nucleation and initial cross-linking; sodium carbonate dominates the condensation reaction in the medium- and high-temperature stages, driving deep cross-linking and structural stabilization of the gel network. The staged synergistic effect of the two catalysts achieves precise control of the polymerization rate and gel network structure, ensuring the regularity and uniformity of the precursor structure from the source, laying the foundation for high batch uniformity of subsequent carbon materials.

[0009] 3. Contribution of Templated Mesostructure to Uniformity and Stability: The regular mesostructure formed by PDADMAC in the gel network transforms into uniformly distributed mesoporous channels during carbonization, avoiding the problems of inconsistent channel size and uneven distribution caused by disordered etching in traditional activation processes. Simultaneously, the cationic polyelectrolyte properties of PDADMAC have a stabilizing effect on the sol-gel nanostructure, effectively inhibiting structural shrinkage and channel collapse during gel drying and carbonization, thus ensuring the long-term storage stability of the material from a mechanistic perspective.

[0010] 4. Synergistic effect of supercritical drying for pore preservation and segmented carbonization for shaping: Supercritical CO2 drying has no surface tension effect, thus completely preserving the original pore structure of the gel; segmented programmed temperature carbonization stabilizes the carbon skeleton at low temperature, achieves gentle and directional activation with potassium hydroxide at medium temperature, and precisely shapes the pore structure at high temperature. These three factors together solve the pain point of "inability to balance pore expansion and structural stability" in traditional high-porosity activation processes, ultimately achieving synergistic optimization of high pore volume, high uniformity, and high stability.

[0011] The specific technical solution of the present invention is as follows: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard material includes the following steps: (1) Preparation of RF resin gel precursor: Resorcinol and formaldehyde solution were used as raw materials, polydiallyl dimethyl ammonium chloride (PDADMAC) was added as a soft template agent, and a composite system of sodium carbonate and ammonia water was used as a catalyst. Sol-gel polymerization reaction was carried out in deionized water to prepare a uniform RF resin gel with a templated mesoscopic structure. The mass ratio of PDADMAC to resorcinol is 1:50 to 1:10; the formaldehyde solution is a 37% analytical grade formaldehyde aqueous solution; the molar ratio of resorcinol to formaldehyde is 1:2 to 1:2.5; the molar ratio of resorcinol to sodium carbonate is 90:1 to 180:1; the amount of ammonia added is 0.5% to 1.5% of the mass of resorcinol; the mass fraction of resorcinol in deionized water is 12% to 22%; and the mass fraction of ammonia used is 25%.

[0012] Furthermore, the polymerization reaction adopts a segmented temperature control process: stirring at 25°C for 30-60 minutes, holding at 65-75°C for 8-10 hours, gelling at 85-95°C for 15-20 hours, and finally aging at 85-95°C for 20-30 hours.

[0013] (2) Post-gel treatment: The obtained RF resin gel was washed, solvent replaced and dried with supercritical CO2 to obtain RF aerogel; The deionized water washing conditions are as follows: soaking and washing at 30-50℃, changing the deionized water every 10-15 hours, repeating 3-4 times, until the washing water conductivity is <10 μS / cm and the pH is neutral. Solvent replacement involves soaking in acetone or ethanol for 6–12 hours. The supercritical CO2 drying conditions are: temperature 35-45℃, pressure 8-12MPa, treatment time 3-6h, and pressure reduction rate 0.5-1.2MPa / h.

[0014] (3) Activation and programmed carbonization: RF aerogel is uniformly mixed with potassium hydroxide activator and carbonized by segmented programmed heating under a high-purity nitrogen protective atmosphere to complete the activation and regulation of pore structure. The mass ratio of RF aerogel to potassium hydroxide is 2:1 to 5:1; the purity of high-purity nitrogen is ≥99.999%; nitrogen is purged for 20 to 40 minutes to replace the air in the furnace before carbonization; and the nitrogen flow rate during carbonization is 80 to 180 mL / min.

[0015] Furthermore, the activation and programmed carbonization employ a segmented programmed heating process, including a low-temperature stage for stabilizing the carbon framework, a medium-temperature stage for directional activation, and a high-temperature stage for precise shaping of the pore structure. The segmented programmed heating process in this step is as follows: room temperature to 200℃, heating rate 1 to 3℃ / min; 200 to 500℃, heating rate 2 to 5℃ / min, with 1 to 2 holding points set in the 300 to 450℃ range, each holding point for 0.5 to 2 hours; 500 to 800℃, heating rate 3 to 6℃ / min; from 800℃ to the final carbonization temperature range, heating rate 2 to 4℃ / min, with the final carbonization temperature being 850 to 1000℃. After reaching the final carbonization temperature, the temperature is held for 3 to 5 hours to complete the activation and carbonization.

[0016] (4) Purification and post-treatment: The carbonized product is washed and dried to remove residual activators and impurities, and then cooled to obtain carbon material pore volume standard material; The carbonized products were washed sequentially with dilute hydrochloric acid and deionized water at a concentration of 0.05–0.2 mol / L until neutral. After washing, they were vacuum dried at 80–120°C for 6–10 hours to remove residual impurities and moisture.

[0017] In addition, this application also claims protection for a high-porosity, highly uniform, and stable carbon material pore volume standard material prepared by the above method, wherein the standard material is based on pure amorphous cross-linked carbon material with a carbon content >99%, a pore size concentrated in the range of 2–20 nm, and no large pore defects; the pore volume range of the standard material is 0.62–1.78 cm³ / g, the relative standard deviation (RSD) of the pore volume measurement value within a batch is <2%, and the pore volume change after 6 months of sealed storage at room temperature is <±0.03 cm³ / g.

[0018] Compared with the prior art, the present invention has the following significant advantages and beneficial effects: 1. Existing carbon-based pore volume standard materials generally have low pore volumes (<0.5 cm). 3 The present invention addresses the limitation that the standard carbon standard ( / g) cannot cover the detection scenarios of high-porosity porous carbon materials, by expanding the pore volume range of carbon-based standard materials to 0.62–1.78 cm³. 3 / g, precisely adaptable to the needs of instrument calibration, method verification and data traceability for supercapacitors and high-porosity carbon materials for adsorption and separation, filling a technological gap in the industry.

[0019] 2. Achieving a synergistic breakthrough in high pore volume, high uniformity, and high stability: In traditional processes, potassium hydroxide activation to increase material pore volume inevitably leads to problems such as disordered pore etching, porous framework, and a significant decrease in batch uniformity and stability. This invention overcomes this technical bottleneck through a synergistic process of "PDADMAC soft template for mesopore creation + staged regulation of composite catalyst + supercritical drying for pore preservation + segmented precise activation and carbonization." The prepared standard material showed an RSD of <2% in batch pore volume testing and a pore volume change of <±0.03 cm during 6 months of long-term storage. 3 / g, pore volume deviation after 5 degassing cycles < ±0.015cm 3 / g, with overall performance far exceeding that of conventional commercial high-porosity carbon materials.

[0020] 3. Pure carbon matrix completely eliminates matrix effect: The final product of this invention has a carbon content of >99%, and the matrix composition, surface properties, and pore adsorption behavior are completely consistent with various commercial porous carbon materials. Compared with inorganic standard materials such as alumina and silica, it completely avoids the detection system error caused by poor matrix matching, and the accuracy and traceability of detection data are greatly improved.

[0021] 4. High process controllability and repeatability: The process parameters are precisely controllable throughout the entire process. The raw material ratio, temperature control, drying and carbonization processes are all set with precise ranges. It has good industrial replicability and can stably produce metering-grade carbon-based pore volume standard materials in batches. Attached Figure Description

[0022] Figure 1 This is a flowchart of the preparation process described in this invention; Figure 2The graph shows a comparison of uniformity RSD and storage pore volume changes over 6 months for both the example and comparative examples. Detailed Implementation

[0023] The following detailed embodiments further illustrate the above-mentioned content of the present invention, but should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention. Unless otherwise specified, the following embodiments are all completed using conventional existing technologies. The performance of all process embodiments of the present invention is far superior to the critical indicators defined in the claims. If the process parameters are adjusted to bring the performance close to the defined threshold, the material still meets the metrological requirements for the use of carbon material pore volume standard materials, without affecting the realization of the core effect of the present invention. The preparation process flow chart used in the following embodiments is shown below. Figure 1 As shown, all raw materials used are of analytical grade, and the nitrogen purity is ≥99.999%.

[0024] The specific test methods for the uniformity and stability parameters described in the following embodiments are as follows: 1. Batch uniformity test: 15 parallel samples were randomly selected from the same batch of finished products, with a sample weight of 0.2g for each sample. The pore volume was tested using the nitrogen adsorption method, and the relative standard deviation (RSD) of the test results was calculated. 2. Long-term storage stability test: The finished product was sealed and stored in a constant temperature and humidity environment of 20-25℃ and 40-50%. The pore volume was sampled and tested at 0 and 6 months, and the change in pore volume was recorded. 3. Cyclic stability test: The sample was subjected to 5 cycles of vacuum degassing-adsorption test, and the pore volume value was measured after each cycle to calculate the maximum deviation; 4. Carbon content test: The carbon content of the material is tested using an organic elemental analyzer.

[0025] Example 1: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard, comprising the following steps: (1) Preparation of RF resin gel precursor: Weigh 12g resorcinol, add 70mL deionized water, stir to dissolve, the mass fraction of resorcinol in deionized water is 14.6%; add 16.5mL of 37% formaldehyde aqueous solution (molar ratio of resorcinol to formaldehyde 1:2), stir to mix; weigh 0.064g sodium carbonate as catalyst (molar ratio of resorcinol to sodium carbonate 180:1), add 0.12g ammonia water (the amount of ammonia water added is 1.0% of the mass of resorcinol), and then add 0.24g PDADMAC (mass ratio of PDADMAC to resorcinol 1:50), after complete dissolution, add to the mixture, stir at 25℃ for 50min, keep warm at 70℃ for 9h, gel at 90℃ for 18h, age at 90℃ for 25h, to obtain a regular RF gel with a templated mesoscopic structure.

[0026] (2) Post-gel treatment: Soak and wash in deionized water at 30℃, change the water every 10h, repeat 3 times until the conductivity of the washing water is 8.2μS / cm and the pH is neutral; soak in acetone for 6h to replace the solvent; dry with supercritical CO2 (40℃, 10MPa, 4h) at a depressurization rate of 0.8MPa / h to obtain structurally complete RF aerogel.

[0027] (3) Activation and carbonization: Mix aerogel and potassium hydroxide in a mass ratio of 5:1 and place in a tube furnace; purge the furnace air with high-purity nitrogen for 20 min at a flow rate of 80 mL / min; segmented heating process: room temperature - 200℃ (1℃ / min), 200-500℃ (2℃ / min, 350℃ for 1 h), 500-800℃ (3℃ / min), 800-900℃ (4℃ / min), 900℃ for 3 h.

[0028] (4) Post-treatment: The carbonized product was soaked in 0.05 mol / L dilute hydrochloric acid for 4 h, washed with deionized water until neutral, vacuum dried at 80 °C for 6 h, and cooled to obtain the pore volume standard material of the finished carbon material.

[0029] Performance testing: Carbon content 99.21%; Pore volume 0.62 cm³ / g; RSD of 15 parallel tests = 1.82%; Pore volume change over 6 months of storage 0.02 cm³ / g. 3 / g; Maximum deviation of 0.012cm in 5 degassing cycles. 3 / g; pore size is concentrated in the range of 2-15nm, with no large pore defects.

[0030] Example 2: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard, comprising the following steps: (1) Preparation of RF resin gel precursor: Weigh 13.5g resorcinol, add 48mL deionized water, the mass fraction of resorcinol in deionized water is 22.0%; add 23.0mL 37% formaldehyde aqueous solution (molar ratio of resorcinol to formaldehyde 1:2.5); weigh 0.087g sodium carbonate (molar ratio 150:1), add 0.202g ammonia water (1.5% of the mass of resorcinol), add 0.675g PDADMAC (mass ratio 1:20), stir at 25℃ for 40min, keep warm at 70℃ for 9h, gel at 90℃ for 18h, and age at 90℃ for 25h.

[0031] (2) Post-gel treatment: Soak and wash in 50℃ deionized water, change the water every 12h, repeat 3 times, until the conductivity of the washing water is 7.5μS / cm and the pH is neutral; soak in acetone for 8h to replace the solvent; dry with supercritical CO2 (45℃, 8MPa, 5h) at a depressurization rate of 1.2MPa / h to obtain structurally complete RF aerogel.

[0032] (3) Activation and carbonization: Mix aerogel and potassium hydroxide in a mass ratio of 3:1 and place in a tube furnace; purge the furnace air with high-purity nitrogen for 30 min at a flow rate of 120 mL / min; segmented heating process: room temperature - 200℃ (2℃ / min), 200-500℃ (3.5℃ / min, 350℃ for 1 h, 450℃ for 1 h), 500-800℃ (5℃ / min), 800-950℃ (3℃ / min), 950℃ for 4 h.

[0033] (4) Post-treatment: The carbonized product was soaked in 0.1 mol / L dilute hydrochloric acid for 4 h, washed with deionized water until neutral, vacuum dried at 100℃ for 8 h, and cooled to obtain the finished product.

[0034] Performance testing: Carbon content 99.35%; Pore volume 1.25 cm³ 3 / g; RSD = 1.15% in 15 parallel tests; Change in pore volume over 6 months: 0.008 cm³ 3 / g; Maximum deviation of 0.010cm in 5 degassing cycles. 3 / g; pore size is concentrated in the range of 3-18nm, and the pore structure is uniform.

[0035] Example 3: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard, comprising the following steps: (1) Preparation of RF resin gel precursor: Weigh 10g resorcinol, add 68mL deionized water, the mass fraction of resorcinol in deionized water is 12.8%; add 15.6mL 37% formaldehyde aqueous solution (molar ratio of resorcinol to formaldehyde 1:2.3); weigh 0.107g sodium carbonate (molar ratio 90:1), add 0.05g ammonia water (0.5% of the mass of resorcinol), add 1.0g PDADMAC (mass ratio 1:10), stir at 25℃ for 60min, keep warm at 65℃ for 10h, gel at 85℃ for 20h, and age at 85℃ for 30h.

[0036] (2) Post-gel treatment: Soak and wash in deionized water at 40℃, change the water every 15h, repeat 4 times until the conductivity of the washing water is 6.3 μS / cm and the pH is neutral; soak in ethanol for 12h to replace; dry with supercritical CO2 (35℃, 12MPa, 6h) at a depressurization rate of 0.5MPa / h to obtain structurally complete RF aerogel.

[0037] (3) Activation and carbonization: Mix aerogel and potassium hydroxide in a mass ratio of 2:1 and place in a tube furnace; purge the furnace air with high-purity nitrogen for 40 min at a flow rate of 180 mL / min; segmented heating process: room temperature - 200℃ (3℃ / min), 200-500℃ (5℃ / min, 400℃ for 2 h), 500-800℃ (6℃ / min), 800-1000℃ (2℃ / min), 1000℃ for 5 h.

[0038] (4) Post-treatment: The carbonized product was soaked in 0.2 mol / L dilute hydrochloric acid for 4 h, washed with deionized water until neutral, vacuum dried at 120℃ for 10 h, and cooled to obtain the finished product.

[0039] Performance testing: Carbon content 99.18%; Pore volume 1.78 cm³ 3 / g; RSD = 1.91% in 15 parallel tests; Change in pore volume over 6 months: 0.025 cm³ 3 / g; Maximum deviation of 0.014cm in 5 degassing cycles. 3 / g; pore size is concentrated in the range of 5-20nm, with no structural defects.

[0040] Example 4: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard, comprising the following steps: (1) Preparation of RF resin gel precursor: Weigh 12g of resorcinol, add 88mL of deionized water, stir to dissolve, the mass fraction of resorcinol in deionized water is 12%; add 18.0mL of formaldehyde aqueous solution with a mass fraction of 37% (molar ratio of resorcinol to formaldehyde 1:2.2), stir to mix; weigh 0.096g of sodium carbonate as catalyst (molar ratio of resorcinol to sodium carbonate 120:1), add 0.144g of ammonia water (the amount of ammonia water added is 1.2% of the mass of resorcinol), and then add 0.4g of PDADMAC (mass ratio 1:30). After complete dissolution, add to the mixture, stir at 25℃ for 30min, then keep warm at 75℃ for 8h, then raise the temperature to 95℃ to gel for 15h, and finally age at 95℃ for 20h to obtain RF gel.

[0041] (2) Post-gel treatment: Soak and wash in deionized water at 40℃, change the water every 12h, repeat 3 times until the conductivity of the washing water is 9.1 μS / cm and the pH is neutral; use ethanol to soak for 10h for solvent replacement; supercritical CO2 drying conditions are temperature 40℃, pressure 10MPa, treatment for 3h, pressure reduction rate 1.0MPa / h, to obtain RF aerogel.

[0042] (3) Activation carbonization: Mix aerogel and potassium hydroxide in a mass ratio of 4:1 and place in a tube furnace; purge the furnace air with high-purity nitrogen for 30 min at a flow rate of 150 mL / min; segmented heating process: room temperature - 200℃ (2℃ / min), 200-500℃ (4℃ / min, and set a heat preservation point at 380℃ for 0.5 h), 500-800℃ (4℃ / min), and in the range of 800℃ to the final carbonization temperature of 850℃ (3℃ / min), and keep at 850℃ for 4 h.

[0043] (4) Post-treatment: The carbonized product was soaked in 0.15mol / L dilute hydrochloric acid for 4h, washed with deionized water until neutral, dried under vacuum at 100℃ for 8h, and cooled to obtain the finished product.

[0044] Performance testing: Carbon content 99.28%; Pore volume 1.45 cm³ 3 / g; RSD = 1.42% in 15 parallel tests; Change in pore volume over 6 months: 0.015 cm³ 3 / g; Maximum deviation of 0.011cm in 5 degassing cycles. 3 / g; pore size is concentrated in the range of 4–16 nm.

[0045] Example 5: A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard, comprising the following steps: (1) Preparation of RF resin gel precursor: Weigh 15g resorcinol, add 68mL deionized water, stir to dissolve, the mass fraction of resorcinol in deionized water is 18.0%; add 24.0mL of formaldehyde aqueous solution with a mass fraction of 37% (molar ratio of resorcinol to formaldehyde 1:2.4); weigh 0.11g sodium carbonate (molar ratio 135:1), add 0.12g ammonia water (0.8% of the mass of resorcinol), add 0.6g PDADMAC (mass ratio 1:25), stir at room temperature of 25℃ for 45min, then keep warm at 68℃ for 9.5h, then raise the temperature to 88℃ for gel formation for 17h, and finally age at 88℃ for 22h to obtain RF gel.

[0046] (2) Post-gel treatment: Soak and wash in deionized water at 45℃, change the water every 11h, repeat 4 times until the conductivity of the washing water is 6.8 μS / cm and the pH is neutral; use acetone to soak for 9h for solvent replacement; supercritical CO2 drying conditions are temperature 38℃, pressure 11MPa, treatment for 5.5h, pressure reduction rate 0.9MPa / h, to obtain RF aerogel.

[0047] (3) Activation carbonization: Mix aerogel and potassium hydroxide at a mass ratio of 2.5:1 and place in a tube furnace; purge the furnace air with high-purity nitrogen for 25 min at a flow rate of 100 mL / min; segmented heating process: room temperature - 200℃ (1.5℃ / min), 200-500℃ (4.5℃ / min, with two heat preservation points at 320℃ and 420℃, each heat preservation for 1.5 h), 500-800℃ (5.5℃ / min), and in the range from 800℃ to the final carbonization temperature of 880℃ (2.5℃ / min), heat preservation at 880℃ for 3.5 h.

[0048] (4) Post-treatment: The carbonized product was soaked in 0.12 mol / L dilute hydrochloric acid for 4 h, washed with deionized water until neutral, dried under vacuum at 90 °C for 9 h, and cooled to obtain the finished product.

[0049] Performance testing: Carbon content 99.30%; Pore volume 1.12 cm³ 3 / g; RSD = 1.28% in 15 parallel tests; Change in pore volume over 6 months: 0.012 cm³ 3 / g; Maximum deviation of 0.009cm in 5 degassing cycles. 3 / g; pore size is concentrated in the range of 3 to 15 nm.

[0050] Comparative Example 1 (without PDADMAC soft template): Except for step (1) where PDADMAC is not added, the rest of the process is the same as in Example 2.

[0051] Test results: Pore volume 1.20cm 3 / g, batch RSD=6.8%, pore volume change over 6 months: 0.038cm³ 3 / g. The results showed that, without the addition of the PDADMAC soft template, although potassium hydroxide activation could still produce a certain pore volume, the pore distribution was disordered, batch uniformity and long-term stability decreased significantly, failing to meet the requirements of the standard material. This proves that the introduction of the PDADMAC soft template is a necessary condition for achieving high uniformity and high stability.

[0052] Comparative Example 2 (Sodium carbonate catalysis alone, without ammonia): Except for step (1), which uses only sodium carbonate as a single catalyst and does not add ammonia, the rest of the process is the same as in Example 2.

[0053] Test results: Pore volume 1.23cm 3 / g, batch RSD=5.2%, pore volume change over 6 months: 0.035cm³ 3 / g. The results show that sodium carbonate catalysis alone cannot achieve precise control over the entire polymerization process, and the insufficient structural regularity of the precursor ultimately affects the uniformity and stability of the carbon material. This demonstrates that the composite catalytic system is a key technical feature for achieving high uniformity.

[0054] Comparative Example 3 (without PDADMAC and catalyzed by sodium carbonate alone): Except for step (1), where PDADMAC is not added and only sodium carbonate is used as a single catalyst, the rest of the process is the same as in Example 2.

[0055] Test results: Pore volume 1.18cm 3 / g, batch RSD=8.3%, pore volume change over 6 months: 0.045cm³ 3 / g. The worst overall performance proves that both the soft template and the composite catalyst are indispensable and have a synergistic effect.

[0056] Comparative Example 4 (without supercritical drying): Conventional oven drying (105℃, atmospheric pressure, 12h) was used instead of supercritical CO2 drying, and the rest of the process was the same as in Example 2.

[0057] Test results: Pore volume 1.22cm 3 / g, batch RSD=7.9%, pore volume change over 6 months: 0.040 cm³ 3 / g, the pores collapsed severely, and the uniformity and stability decreased significantly.

[0058] Comparative Example 5 (Carbonization without segmented insulation): The 200-500℃ heat preservation process is omitted, and carbonization is carried out directly at a uniform rate. The rest of the process is the same as in Example 2.

[0059] Test results: Pore volume 1.26cm 3 / g, batch RSD=6.5%, pore volume change over 6 months: 0.036cm³ 3 / g, the activated etching is disordered, the pore structure is disordered, and it does not meet the requirements of the standard material.

[0060] Based on the test results of the above embodiments and experimental examples, such as Figure 2 As shown, the RSD values ​​(1.15%–1.91%), long-term storage stability, and cycle stability of the embodiments of the present invention are significantly better than those of the comparative samples. This proves that the synergistic process system of "PDADMAC soft template + composite catalytic system + supercritical drying + segmented programmed carbonization" defined in this invention is a necessary condition for achieving a unified high pore volume, high uniformity, and high stability, and is not a simple superposition of conventional processes. The comprehensive performance of the obtained standard material far exceeds that of conventional commercial high-porosity carbon materials.

[0061] For those skilled in the art, the specific embodiments are merely illustrative descriptions of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for preparing a high-porosity, highly uniform, and stable carbon material pore volume standard reference, characterized in that, Includes the following steps: (1) Preparation of RF resin gel precursor: Resorcinol and formaldehyde solution were used as raw materials, polydiallyldimethylammonium chloride was added as a soft template agent, and a composite system of sodium carbonate and ammonia water was used as a catalyst. Sol-gel polymerization reaction was carried out in deionized water to prepare a uniform RF resin gel with a templated mesoscopic structure. (2) Post-gel treatment: The obtained RF resin gel was washed, solvent replaced and dried with supercritical CO2 to obtain RF aerogel; (3) Activation and programmed carbonization: RF aerogel is uniformly mixed with potassium hydroxide activator and carbonized by segmented programmed heating under a high-purity nitrogen protective atmosphere to complete the activation and regulation of pore structure. The segmented programmed heating includes a low-temperature segment for stabilizing the carbon skeleton, a medium-temperature segment for directional activation, and a high-temperature segment for precisely shaping the pore structure. (4) Purification and post-treatment: The carbonized product is washed and dried to remove residual activators and impurities, and then cooled to obtain carbon material pore volume standard material.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of polydiallyldimethylammonium chloride to resorcinol is 1:50 to 1:10; the formaldehyde solution is an analytical grade formaldehyde aqueous solution with a mass fraction of 37%; the molar ratio of resorcinol to formaldehyde is 1:2 to 1:2.5; the molar ratio of resorcinol to sodium carbonate is 90:1 to 180:1; the amount of ammonia added is 0.5 to 1.5% of the mass of resorcinol; the mass fraction of ammonia is 25%; and the mass fraction of resorcinol in deionized water is 12 to 22%.

3. The preparation method according to claim 1 or 2, characterized in that, The polymerization reaction described in step (1) adopts a segmented programmed heating process: stirring at 25℃ for 30-60 min, holding at 65-75℃ for 8-10 h, gelling at 85-95℃ for 15-20 h, and finally aging at 85-95℃ for 20-30 h.

4. The preparation method according to claim 1, characterized in that, In step (2), the washing conditions using deionized water are: soaking and washing at 30-50℃, changing the deionized water every 10-15 hours, repeating 3-4 times until the conductivity of the washing water is <10 μS / cm and the pH is neutral.

5. The preparation method according to claim 1, characterized in that, In step (2), solvent replacement is performed by soaking in acetone or ethanol for 6–12 hours.

6. The preparation method according to claim 1, characterized in that, The supercritical CO2 drying conditions in step (2) are: temperature 35-45℃, pressure 8-12MPa, treatment time 3-6h, and pressure reduction rate 0.5-1.2MPa / h.

7. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of RF aerogel to potassium hydroxide is 2:1 to 5:1; the purity of high-purity nitrogen is ≥99.999%; nitrogen is passed through the furnace for 20 to 40 minutes to replace the air before carbonization; and the nitrogen flow rate during carbonization is 80 to 180 mL / min.

8. The preparation method according to claim 1 or 7, characterized in that, The segmented programmed heating process in step (3) is as follows: room temperature to 200℃, heating rate 1 to 3℃ / min; 200 to 500℃, heating rate 2 to 5℃ / min, and 1 to 2 heat preservation points are set in the 300 to 450℃ range, each heat preservation point is kept for 0.5 to 2 hours; 500 to 800℃, heating rate 3 to 6℃ / min; 800℃ to the final carbonization temperature range, heating rate is 2 to 4℃ / min, the final carbonization temperature is 850 to 1000℃, and after reaching the final carbonization temperature, it is kept for 3 to 5 hours to complete the activation carbonization.

9. The preparation method according to claim 1 or 7, characterized in that, In step (4), the carbonized product is washed sequentially with dilute hydrochloric acid and deionized water at a concentration of 0.05–0.2 mol / L until neutral, and then vacuum dried at 80–120 °C for 6–10 h.

10. A high-porosity, highly uniform, and stable carbon material pore volume standard material prepared by the method according to any one of claims 1-9, characterized in that, The standard material uses pure amorphous cross-linked carbon material as the matrix, with a carbon content >99%, and the pore size is concentrated in the range of 2-20 nm, without large pore defects; the pore volume range is 0.62-1.78 cm³ / g, the relative standard deviation (RSD) of the pore volume measurement value within the batch is <2%, and the pore volume change after 6 months of sealed storage at room temperature is <±0.03 cm³ / g.

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