A method for preparing a carbon-based high specific surface area material

Abstract

This invention relates to the field of carbon-based new materials technology, specifically to a method for preparing carbon-based high specific surface area materials, comprising four steps: raw material carbonization, atmosphere activation, acid washing, and high-temperature reduction. Wood chips are anaerobically carbonized, crushed, and sieved, then placed in an externally heated, closed-atmosphere rotary activation furnace at 800-1000℃ under a ternary activation gas mixture of ammonia, water vapor, and carbon dioxide for 4-8 hours. During activation, a potassium carbonate and sodium hydroxide dual-base catalyst is injected, and the oxygen content is adjusted in real time. The activated material is then subjected to three-stage acid washing with hydrochloric acid, nitric acid, and hydrofluoric acid until the pH reaches 6-7, followed by drying and grinding. Finally, it is placed in an atmosphere reduction furnace, first passivated with nitrogen, then reduced with hydrogen at 800-1100℃. The resulting material has a specific surface area ≥1600 m². 2 With a surface oxygen content ≤0.5 mmol / g and a bulk density ≥0.44 g / mL, it can be used as a supercapacitor electrode, CO2 adsorption and desulfurization catalysis.

Description

Technical Field

[0001] This invention relates to the field of carbon-based new materials technology, specifically to a method for preparing carbon-based high specific surface area materials. Background Technology

[0002] Activated carbon, as a typical porous carbon-based functional material, is widely used in many industrial fields such as water treatment, air pollution control, gas purification, electrochemical energy storage, and catalytic reaction carriers due to its well-developed pore structure, huge specific surface area, and controllable surface chemical properties. With the rapid development of emerging industries such as new energy vehicles and supercapacitors, and the higher requirements for carbon dioxide capture and desulfurization and denitrification technologies, more stringent requirements are being placed on the performance indicators, production costs, and environmental friendliness of carbon-based high specific surface area materials.

[0003] In existing technologies, methods for preparing high specific surface area carbon-based materials are mainly divided into two categories: physical activation and chemical activation. Based on these, improved processes such as combined physical-chemical methods, microwave activation, and template methods have been derived. Physical activation typically uses oxidizing gases such as water vapor, carbon dioxide, or air as activators at high temperatures of 800 to 1000°C. Pores are etched through selective vaporization reactions between gas molecules and carbon atoms on the carbon skeleton surface. This process is simple, clean, has low environmental pollution, and relatively low production costs, making it the mainstream process used by approximately 70% of activated carbon producers worldwide. However, physical activation requires a long reaction time, and the resulting product has a predominantly microporous pore structure with a specific surface area typically not exceeding 1500 m². 2 The yield is low, and the reaction between a single oxidizing atmosphere and the carbon framework can only achieve pore-forming function, but cannot simultaneously embed heteroatoms into the carbon framework to regulate surface chemical properties during the pore-forming process. The chemical activation method involves pre-mixing the raw materials with chemicals such as KOH, ZnCl2, and H3PO4 in a specific ratio in a solid phase or impregnating them in a liquid phase, followed by high-temperature activation under an inert atmosphere. This method can prepare surfaces with a specific surface area of ​​up to 3000 m² in a relatively short time. 2 Products with a yield of / g or more; however, the chemical activation method faces prominent problems such as high consumption of chemical reagents, high production costs, severe equipment corrosion, and heavy post-treatment load after pickling and washing, which limit its application in large-scale industrial production.

[0004] Specifically, regarding a representative prior art disclosure, WO 03 / 095368 (Production of catalytically active activated carbon from wood char with ammonia and steam) discloses a method for preparing catalytically active activated carbon by adding ammonia to steam and using wood char as a carbon source. The activation gas in this method is a binary mixture of ammonia and steam. However, the process does not introduce carbon dioxide as a third activation gas to form a ternary atmosphere system, and the real-time control of oxygen content in the activation furnace is not standardized. This results in ammonia being easily partially oxidized into nitrogen-containing oxides by trace amounts of oxygen during high-temperature activation, reducing the nitrogen source utilization rate of ammonia, and limiting the selective enrichment of pyridine nitrogen in the obtained activated carbon. Sci. Rep. 2016, 6, 30295 (Y. Hu et al., One-Step Synthesis of Microporous Carbon Monoliths Derived from Biomass with High Nitrogen Doping Content for Highly Selective CO2Capture) reported a one-step process for preparing nitrogen-doped porous carbon using corn cob as a precursor and ammonia as a single activation gas and nitrogen source. However, the pore-forming intensity of a single ammonia atmosphere is limited, and the specific surface area of ​​the obtained material is usually lower than that of steam-activated products. Furthermore, the synergistic introduction of a catalyst system is not involved, and the reaction rate between ammonia and the carbon skeleton during activation is difficult to decouple and control from the pore-forming depth.

[0005] Materials 2019, 12, 1207 (R. Wei et al., Enhanced CO2 Adsorption on Nitrogen-Doped Carbon Materials by Salt and Base Co-Activation Method) discloses a salt and base co-activation method for carbonizing and activating resorcinol-formaldehyde resin precursors using a combination of potassium chloride and potassium hydroxide under an ammonia gas flow. The resulting nitrogen-doped carbon materials exhibit good adsorption performance for carbon dioxide. However, this method belongs to the chemical activation route, requiring the catalyst and precursor to be pre-mixed in a solid phase. This results in a large amount of catalyst used, severe corrosion of the reactor, and a heavy subsequent acid and water washing load, making it difficult to meet the requirements of large-scale industrial clean production. Patent document US 11,767,222 B2 (Activatedcarbon method and material) discloses an activation method for activated carbon using a fluidized bed reactor and a three-stage sequential gas flow of oxygen, ammonia, and hydrogen. The process path is as follows: first, oxygen is used to create oxidative active sites on the surface of activated carbon; then, ammonia is used to nitrid the active sites; and finally, hydrogen is used to stabilize the nitrided intermediate. The design logic of this process sequence is based on a reaction path of creating active sites first and then intercalating nitrogen. Sufficient active sites need to be generated by the pre-oxygen oxidation step before subsequent nitriding can be carried out. The process path of directly creating pores and intercalating nitrogen in one step and then stabilizing the surface is not disclosed, and the scheme does not involve the injection of a dual-base catalyst. Non-patent literature ACS Appl. Mater. Interfaces 2024 (Hydrogen-Assisted Thermal Treatment of Electrode Materials for Electrochemical Double-Layer Capacitors) reported the effectiveness of hydrogen thermal treatment in removing oxygen-containing functional groups from the surface of commercial activated carbon and stabilizing the working voltage of supercapacitor electrodes; however, this method only performs single-stage hydrogen treatment on the finished activated carbon and does not form a systematic integration with the previous activation process, making it difficult to simultaneously address the pore structure and surface chemical properties of the resulting material.

[0006] As can be seen from the above, existing technologies have shortcomings in physical activation methods, such as low specific surface area and difficulty in simultaneously achieving pore formation and nitrogen intercalation; in chemical activation methods, such as high reagent consumption and heavy post-processing load; and in the lack of systematic integration between the stabilization process of activated carbon surface chemistry and the front-end activation process. These shortcomings make it difficult to achieve the three technical goals of high specific surface area, pyridine nitrogen-rich surface chemical properties, and stable electrochemical application interface on a single process line. There is an urgent need to provide a carbon-based high specific surface area material preparation method that can integrate the above three technical requirements and has a simple process that can be industrially promoted. Summary of the Invention

[0007] To address three main technical problems in existing technologies—the difficulty in simultaneously achieving pore formation and nitrogen doping, the heavy post-processing load of chemical activation routes, and the decline in the cycle stability of electrochemical applications due to residual oxygen-containing functional groups on the activated carbon surface—this invention aims to provide a method for preparing carbon-based high specific surface area materials. This method integrates a ternary mixed gas activation process coupled with the injection of a dual-base catalyst in an externally heated, closed-atmosphere rotary activation furnace, combined with a two-stage nitrogen passivation-hydrogen reduction post-processing, to achieve a synergistic effect of high specific surface area, low surface oxygen concentration, and suitable packing density.

[0008] To achieve the above-mentioned objectives, the technical solution provided by this invention includes the following steps: First, woody biomass raw materials containing sawdust are carbonized at high temperature under anaerobic conditions to obtain carbonized material; the carbonized material is crushed and sieved, then placed in an externally heated, sealed atmosphere rotary activation furnace, and a ternary mixed activation gas composed of ammonia, water vapor, and carbon dioxide is introduced at an activation temperature of 800 to 1000°C for 4 to 8 hours. During the activation process, a dual-base catalyst containing potassium carbonate and sodium hydroxide is simultaneously injected into the activation furnace, and the component content of the ternary activation gas and the oxygen content in the activation furnace are controlled in real time; the activated material is washed with inorganic acid and then washed with water until the pH value is 6 to 7, dried, and ground to obtain carbon-based powder; the carbon-based powder is placed in an atmosphere reduction furnace, and nitrogen is first introduced for passivation treatment until the furnace is oxygen-free. After stopping the introduction of nitrogen, hydrogen is introduced for reduction treatment at 800 to 1100°C to finally obtain the carbon-based high specific surface area material.

[0009] The method for preparing carbon-based high specific surface area materials provided by this invention has the following advantages compared with existing technologies. First, the simultaneous introduction of ternary mixed activation gases enables the simultaneous occurrence of pore-forming and nitrogen-doping functions: water vapor and carbon dioxide are responsible for the dominant pore etching process, while nitrogen free radicals generated by the decomposition of ammonia at 800 to 1000°C undergo substitution reactions with unsaturated carbon skeleton carbon atoms, embedding pyridine nitrogen and pyrrole nitrogen sites. The simultaneous action of the three gases can more accurately control the coupling relationship between nitrogen embedding density and pore size distribution compared with binary or single atmospheres. Second, the potassium carbonate and sodium hydroxide dual-base catalyst is introduced into the activation furnace atmosphere by injection rather than premixing with the precursor, reducing the catalyst dosage to 0.4% to 0.6% of the carbonized material mass, which is significantly reduced compared to the traditional 20% to 50% catalyst dosage of chemical activation methods. At the same time, it significantly reduces the corrosion of the reactor inner wall and the post-treatment load of acid washing and water washing. Third, real-time control of oxygen content in the activation furnace prevents ammonia from being oxidized into nitrogen-containing oxide byproducts by trace amounts of oxygen at high temperatures, maximizing the utilization rate of ammonia as a nitrogen source. Fourth, the two-stage post-treatment process—first passing through nitrogen to passivate and purge the air from the furnace, then passing through hydrogen for high-temperature reduction—can specifically remove oxygen-containing functional groups remaining on the carbon surface after acid washing without damaging the carefully constructed pore structure in the previous stage. This results in carbon-based high specific surface area materials with a specific surface area ≥1600 m². 2 With comprehensive performance indicators such as g / g, surface oxygen concentration ≤0.5 mmol / g, and bulk density ≥0.44 g / mL, it has significant industrial value in high-end application fields such as supercapacitor electrode active materials, carbon dioxide selective adsorbents, and desulfurization and denitrification catalyst supports. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the process flow for preparing carbon-based high specific surface area materials according to the present invention. Detailed Implementation

[0011] The technical solution of the present invention will be described in detail below with reference to embodiments, but the scope of protection of the present invention is not limited thereto. Equivalent substitutions, parameter adjustments, and non-substantial improvements made by those skilled in the art based on the technical solution disclosed in the present invention all fall within the scope of protection of the present invention. The process flow diagram of the present invention is shown below. Figure 1 As shown, the overall process consists of six steps in sequence: oxygen-free high-temperature carbonization of wood chips, catalytic activation and pore opening, acid washing, grinding, high-temperature reduction and passivation, and mixed finished product packaging. In the catalytic activation and pore opening step, a ternary mixed activation gas of water vapor, ammonia and carbon dioxide is introduced, and a dual-base catalyst of potassium carbonate and sodium hydroxide is sprayed in. In the high-temperature reduction and passivation step, nitrogen gas is introduced first and then hydrogen gas for two-stage treatment. Example 1

[0012] This embodiment 1 is as follows: Figure 1The process flow shown provides a carbon-based high specific surface area material and its preparation method. This embodiment represents the optimal implementation of the present invention, and the prepared carbon-based high specific surface area material possesses optimal comprehensive performance indicators in terms of specific surface area, pore volume, surface oxygen concentration, and bulk density. The specific preparation steps are as follows.

[0013] Step 1: Raw material pretreatment and anaerobic carbonization. Take sawdust raw materials that have undergone screening and drying, with a particle size of 10-20 mesh and a moisture content of 5%-8%. Place the sawdust raw materials in an anaerobic nitrogen protective atmosphere furnace for two-stage carbonization. The first stage carbonization temperature is 480℃, and the constant temperature carbonization time is 2 hours, during which volatile matter is initially removed. The temperature is then increased to 700℃ for the second stage carbonization, and the constant temperature time is 1.5 hours. The final volatile matter content of the carbonized material is controlled within the range of 10%-15%. The resulting carbonized material is crushed and screened to 16-40 mesh for later use.

[0014] Step 2: Simultaneous activation in a ternary atmosphere and injection of a dual-base catalyst. The 16-40 mesh carbonized material obtained in Step 1 is continuously fed into an externally heated, closed-atmosphere rotary activation furnace for catalytic activation and pore opening treatment. The activation temperature is set at 900℃, and the activation time is 4-5 hours. A ternary mixed activation gas consisting of water vapor, ammonia, and carbon dioxide is introduced into the activation furnace, with a water vapor flow rate of 2.0 g / min, an ammonia flow rate of 0.3 g / min, and carbon dioxide as an auxiliary gas introduced simultaneously at a flow rate of 0.2 L / min. The carbonized material is fed into the activation furnace at a rate of 3 g / min, and the discharge rate of the activation furnace is 1.1 g / min. During activation, a dual-base catalyst containing potassium carbonate and sodium hydroxide is simultaneously injected into the atmosphere of the activation furnace. Potassium carbonate accounts for 0.3% of the mass of the carbonized material, and sodium hydroxide accounts for 0.1% of the mass of the carbonized material. The catalyst is uniformly dispersed into the atmosphere of the activation furnace by atomization. Throughout the activation process, the composition of the ternary activation gas is monitored in real time using an online gas analyzer, and the oxygen content inside the activation furnace is monitored in real time using an oxygen content sensor to ensure that the oxygen content is below 0.1% to prevent ammonia from being oxidized into nitrogen oxide byproducts by trace amounts of oxygen at high temperatures.

[0015] Step 3: Cooling and Three-Stage Acid Washing of Activated Material. After activation, the activated material is cooled to room temperature under a sealed nitrogen atmosphere. The cooled activated material is first acid-washed with 10% hydrochloric acid (5 times the mass of the activated material), with stirring for 1 hour. This primarily removes residual potassium carbonate, sodium hydroxide, and potassium-sodium carbonates and chlorides. After filtration, a second acid wash is performed with 5% nitric acid (3 times the mass of the activated material), with stirring for 1 hour. This primarily removes nitrogen-containing impurities generated during the partial oxidation of ammonia in the activation process. Finally, after filtration, a third acid wash is performed with 3% hydrofluoric acid (2 times the mass of the activated material), with stirring for 30 minutes. This primarily removes inherent silica-based ash from the wood chips. After the three-stage pickling process, the mixture is repeatedly washed with deionized water until the pH of the washing solution is 6 to 7. After drying, it is ground into carbon-based powder with a median particle size D50 of 5 to 7 μm.

[0016] Step four: Two-stage high-temperature treatment of nitrogen passivation and hydrogen reduction. The carbon-based powder obtained in step three is continuously fed into an atmosphere reduction furnace for surface chemical stabilization treatment. First, at a speed of 0.05 m... 3 Nitrogen gas is introduced into the reduction furnace at a flow rate of 0.01 m³ / min for passivation treatment, replacing and purging the air inside the furnace until the oxygen content is below the detection threshold. After stopping the nitrogen supply, hydrogen gas is slowly introduced into the reduction furnace at a flow rate of 0.01~0.02 m³ / min. 3 The reduction furnace was operated at a rate of 900°C for 1 hour, and the reduction process was carried out at a rate of 900°C for 1 hour. After the reduction process, the material was cooled to room temperature under nitrogen protection to obtain the carbon-based high specific surface area material of Example 1.

[0017] The carbon-based high specific surface area material prepared in Example 1, after characterization testing, showed a specific surface area of ​​1756 m². 2 The carbon material has a pore volume of 0.8 mL / g, a surface oxygen concentration of 0.50 mmol / g, and a bulk density of 0.45 g / mL. Its comprehensive performance indicators reach the optimal level of the carbon material for electrodes described in this invention.

[0018] Further characterization results of the carbon-based high specific surface area material obtained in Example 1 are as follows. Nitrogen adsorption-desorption isotherm tests show that the prepared material exhibits typical Type I adsorption isotherm characteristics in the relative pressure range of P / P0 = 0.05~0.30, and obvious hysteresis loops appear in the range of P / P0 = 0.45~0.95, indicating that the obtained carbon-based material has a hierarchical pore structure dominated by micropores and supplemented by mesopores. The pore size distribution results calculated based on density functional theory (DFT) show that the pore size distribution of the obtained material is mainly concentrated in the micropore range of 0.6~1.2 nm and the mesopore range of 2.5~4.0 nm, forming a bimodal distribution. The micropore volume accounts for about 72% of the total pore volume, the mesopore volume accounts for about 24%, and the macropore volume accounts for about 4%. X-ray photoelectron spectroscopy (XPS) analysis showed that the total nitrogen atom content on the surface of the obtained material was 3.8 at%, of which pyridine nitrogen (binding energy 398.5 eV) accounted for about 45% of the total nitrogen atoms, pyrrole nitrogen (binding energy 400.2 eV) accounted for about 28%, graphitic nitrogen (binding energy 401.3 eV) accounted for about 21%, and quaternary nitrogen oxides (binding energy 403.5 eV) accounted for about 6%. The high proportion of pyridine nitrogen is a characteristic characterization result of the ternary atmosphere activation process described in this invention. Pyridine nitrogen sites make outstanding contributions to the chemisorption of carbon dioxide molecules and the selective adsorption of acidic gases such as hydrogen sulfide and sulfur dioxide. Scanning electron microscopy (SEM) observation showed that the obtained carbon-based powder had a uniform, irregular particle morphology, with a large number of open channels of 1-3 μm distributed on the particle surface, corresponding to the corrosion channels formed by potassium vapor and sodium salt melt during the activation process; transmission electron microscopy (TEM) observation further showed that there were a large number of worm-like microporous structures inside the particles, with the diameter of a single micropore being less than 1 nm, which was consistent with the DFT pore size distribution results. Example 2

[0019] The difference between Example 2 and Example 1 is that, during the activation stage, no potassium carbonate and sodium hydroxide dual-base catalyst was injected, and all other parameters remained unchanged. The focus was on verifying the basic pore-forming and nitrogen-intercalating performance under ternary atmosphere activation without the introduction of a dual-base catalyst. The specific preparation steps are as follows.

[0020] Step 1 is the same as in Example 1. Take wood chips with a mesh size of 10 to 20 and a moisture content of 5% to 8%, carbonize them at 480°C for 2 hours under anaerobic conditions, and then raise the temperature to 700°C for 1.5 hours to obtain carbonized material. Crush and sieve the material to a mesh size of 16 to 40.

[0021] Step two: Activation in a ternary atmosphere without injecting a catalyst. The carbonized material is placed in an externally heated, closed-atmosphere rotary activation furnace at 900℃ for 4-5 hours. A ternary mixed activation gas is introduced at a flow rate of 2.0 g / min for steam, 0.3 g / min for ammonia, and 0.2 L / min for carbon dioxide. The feed rate of the carbonized material is 3 g / min, and the discharge rate is 1.0 g / min. The composition and oxygen content of the ternary gas are monitored in real time using an online gas analyzer and an oxygen content sensor. No potassium carbonate or sodium hydroxide catalyst is injected throughout the activation process.

[0022] Step 3 is basically the same as in Example 1. However, since no dual-base catalyst was sprayed in the activation stage of Example 2, there are no carbonate and hydroxide residues in the activated material. Therefore, the amount of acid used in the first stage of hydrochloric acid washing is halved, while the washing steps of nitric acid and hydrofluoric acid remain unchanged. Finally, the material is washed with water until the pH is 6 to 7, dried and ground until the D50 is 5 to 7 μm carbon-based powder.

[0023] Step four is the same as in Example 1. First, introduce nitrogen gas at a rate of 0.05 m³. 3 After passivating and purging the air from the furnace by / min, stop the nitrogen supply and then introduce hydrogen at a rate of 0.01~0.02 m. 3 The carbon-based high specific surface area material of Example 2 was obtained by reducing the material at 900℃ for 1 h at a constant temperature and cooling it under nitrogen protection.

[0024] The carbon-based high specific surface area material prepared in Example 2 was characterized and tested, and its specific surface area was 1652 m². 2 / g, pore volume is 0.7 mL / g, surface oxygen concentration is 0.45 mmol / g, and bulk density is 0.44 g / mL. Comparing Example 2 with Example 1, it can be seen that the injection of the dibasic catalyst has a significant gain effect on specific surface area and pore volume, increasing the specific surface area from 1652 m² / g. 2 / g increased to 1756 m 2 The micropore volume increased from 0.7 mL / g to 0.8 mL / g, and the bulk density increased slightly from 0.44 g / mL to 0.45 g / mL, demonstrating that the injection process of the dual-base catalyst can further enhance the pore-forming effect without destroying the uniformity of the pore structure.

[0025] Further characterization results of the carbon-based high specific surface area material obtained in Example 2 are as follows. Nitrogen adsorption-desorption isotherms show that the material also exhibits Type I-dominated adsorption characteristics, but its hysteresis loop area is significantly smaller than that of Example 1, reflecting a decrease in mesopore formation compared to Example 1 under the absence of a dual-base catalyst. DFT pore size distribution shows that the material has a micropore volume ratio of approximately 81%, a mesopore volume ratio of approximately 15%, and a macropore ratio of approximately 4%. The pore size distribution is mainly concentrated in the 0.5–1.0 nm micropore range, while the peak intensity in the 2.5–4.0 nm mesopore range is only about 60% of that in Example 1. XPS analysis shows that the total surface nitrogen atom content of the material obtained in Example 2 is 3.5 at%, with a pyridine nitrogen content of approximately 42%, close to the 45% level of Example 1. This indicates that the ternary atmosphere activation process itself can ensure the selective enrichment of pyridine nitrogen, and the introduction of the dual-base catalyst has a relatively small impact on the pyridine nitrogen content, mainly contributing to the bimodalization of the pore structure and further improvement of the specific surface area. Example 3

[0026] The difference between Example 3 and Example 1 is that the ammonia flow rate and the injection ratio of potassium carbonate and sodium hydroxide are both increased, focusing on verifying the enhanced synergistic effect of the ternary atmosphere and the dual-base catalyst on the further enhancement of pore-forming and nitrogen-intercalation. The specific preparation steps are as follows.

[0027] Step 1 is the same as in Example 1. Take wood chips with a mesh size of 10 to 20 and a moisture content of 5% to 8%, carbonize them at 480°C for 2 hours under anaerobic conditions, and then raise the temperature to 700°C for 1.5 hours to obtain carbonized material. The volatile matter content is controlled at 10% to 15%, and the material is crushed and sieved to 16 to 40 mesh.

[0028] Step two involves enhanced synergistic ternary atmosphere activation and the injection of a dual-base catalyst. The activation temperature is 900℃, and the activation time is 4-5 h. A ternary mixed activation gas is introduced at a flow rate of 2.0 g / min for steam, 0.6 g / min for ammonia (double that of Example 1), and 0.2 L / min for carbon dioxide. The feed rate of the carbonized material is 3 g / min, and the discharge rate is 1.0 g / min. During activation, a dual-base catalyst containing 0.35% potassium carbonate (slightly higher than 0.3% in Example 1) and 0.25% sodium hydroxide (significantly higher than 0.1% in Example 1) is simultaneously injected into the activation furnace atmosphere. The composition and oxygen content of the ternary gas are monitored in real time using an online gas analyzer and an oxygen content sensor to ensure that the oxygen content is below 0.1%.

[0029] Step 3 is the same as in Example 1. The activated material is sequentially acid-washed in three stages with 10% hydrochloric acid, 5% nitric acid and 3% hydrofluoric acid, washed with water until pH 6 to 7, and dried and ground until D50 is 5~7 μm carbon-based powder.

[0030] Step four is the same as in Example 1. First, purge with nitrogen gas at a rate of 0.05 m³. 3 After passivating and purging the air from the furnace by / min, stop the nitrogen supply and then introduce hydrogen at a rate of 0.01~0.02 m. 3 The carbon-based high specific surface area material of Example 3 was obtained by reducing the material at 900℃ for 1 h and cooling it under nitrogen protection.

[0031] The carbon-based high specific surface area material prepared in Example 3 was characterized and tested to have a specific surface area of ​​1791 m². 2 / g, pore volume is 0.8 mL / g, surface oxygen concentration is 0.72 mmol / g, and bulk density is 0.40 g / mL. Comparing Example 3 with Example 1, it can be seen that simultaneously increasing the ammonia flow rate and the amount of dual-base catalyst injected can increase the specific surface area from 1756 m² / g. 2 / g further increased to 1791 m 2 While the yield was 1 g / g, the specific surface area gain was relatively limited. Simultaneously, the excessive increase in the amount of the dual-base catalyst led to an increased activation depth, causing partial pore wall collapse. This was reflected in a decrease in bulk density from 0.45 g / mL to 0.40 g / mL. Furthermore, some nitrogen free radicals generated by the decomposition of excess ammonia during activation failed to effectively embed into the carbon framework but instead formed weakly bonded nitrogen-containing oxides with surface residual carbon, resulting in an increase in surface oxygen concentration from 0.50 mmol / g to 0.72 mmol / g. A comparison of this example with Example 1 shows that there is an optimal critical point for the synergy between the ternary atmosphere and the dual-base catalyst; excessively increasing the amount of catalyst and ammonia does not bring a linear performance gain.

[0032] Further characterization results of the carbon-based high specific surface area material obtained in Example 3 are as follows. Nitrogen adsorption-desorption isotherms show that the hysteresis loop area of ​​this material is slightly larger than that of Example 1. DFT pore size distribution shows a significant rightward shift in the pore size distribution within the 2.5–4.0 nm mesoporous range, with the peak center shifting from 3.2 nm in Example 1 to 3.6 nm, and a secondary distribution peak appearing in the larger mesoporous range of 4–10 nm. The micropore volume ratio decreases to approximately 65%, the mesopore volume ratio increases to approximately 30%, and the macropore ratio is approximately 5%. XPS analysis shows that the total surface nitrogen atom content of the material obtained in Example 3 is 4.2 at%, slightly higher than the 3.8 at% in Example 1, but the pyridine nitrogen ratio decreases from 45% in Example 1 to approximately 38%, while the ratios of pyrrole nitrogen and quaternary nitrogen oxides increase accordingly, reflecting that under excess ammonia supply conditions, nitrogen free radicals tend to randomly insert rather than selectively occupy pyridine nitrogen sites. This result quantitatively confirms the synergistic optimal critical point mechanism theory revealed by the comparison between Example 3 and Example 1 at the characterization level.

[0033] Comparative Example 1 The purpose of Comparative Example 1 is to verify the synergistic gain of the ternary mixed activation gas compared to a single water vapor activation atmosphere. The difference between this comparative example and Example 1 is that only single water vapor is introduced as the activation gas during the activation stage, and the potassium carbonate and sodium hydroxide dual-base catalyst is not injected.

[0034] The specific preparation steps are as follows. Step 1 is the same as in Example 1, obtaining 16-40 mesh carbonized material with 10%-15% volatile matter. Step 2: The carbonized material is placed in an externally heated, closed-atmosphere rotary activation furnace at an activation temperature of 850℃ for 5-6 hours; the activation gas is only water vapor at a flow rate of 2.0 g / min; the feed rate of the carbonized material is 3 g / min, and the discharge rate is 1.0 g / min; no ammonia or carbon dioxide is introduced during the entire activation process, and no catalyst is injected. Step 3 is the same as in Example 1, involving acid washing, drying, and grinding. Step 4: High-temperature nitrogen passivation-hydrogen reduction treatment is not performed; the activated material, after acid washing, drying, and grinding, directly yields the product of Comparative Example 1.

[0035] The activated carbon material prepared in Comparative Example 1, after characterization testing, showed a specific surface area of ​​only 1152 m². 2 / g, with a pore volume of 0.6 mL / g, a surface oxygen concentration of 2.12 mmol / g, and a bulk density of 0.46 g / mL. A comparison between Comparative Example 1 and Example 1 shows that the ternary mixed activation gas can increase the specific surface area from 1152 m² / g compared to a single water vapor activation atmosphere. 2 / g increased to 1756 m 2 / g, the pore volume increased from 0.6 mL / g to 0.8 mL / g, and the high-temperature nitrogen passivation-hydrogen reduction post-treatment process could significantly reduce the surface oxygen concentration from 2.12 mmol / g to 0.50 mmol / g, proving that the integration of the ternary atmosphere activation and the two-stage post-treatment process described in this invention has a significant and unpredictable synergistic effect.

[0036] Comparative Example 2 The purpose of Comparative Example 2 is to verify the independent contribution of the potassium carbonate and sodium hydroxide dual-base catalyst in the ternary atmosphere activation. The difference between this comparative example and Example 1 is that the ternary mixed atmosphere of water vapor, ammonia, and carbon dioxide is maintained constant during the activation stage, but the potassium carbonate and sodium hydroxide dual-base catalyst is not injected; at the same time, the subsequent high-temperature hydrogen reduction treatment step is omitted.

[0037] The specific preparation steps are as follows. Step 1 is the same as in Example 1. Step 2: The carbonized material is placed in an externally heated, sealed rotary activation furnace at an activation temperature of 900℃ for 4-5 hours. A ternary mixed activation gas is introduced, consisting of steam at a flow rate of 2.0 g / min, ammonia at a flow rate of 0.3 g / min, and carbon dioxide at a flow rate of 0.2 L / min. The feed rate of the carbonized material is 3 g / min, and the discharge rate is 1.0 g / min. No catalyst is injected during the entire activation process. Step 3: The process is the same as in Example 1, involving acid washing, drying, and grinding. Step 4: High-temperature nitrogen passivation-hydrogen reduction treatment is not performed.

[0038] The activated carbon material prepared in Comparative Example 2 was characterized and tested to have a specific surface area of ​​1483 m². 2 / g, with a pore volume of 0.65 mL / g, a surface oxygen concentration of 1.63 mmol / g, and a bulk density of 0.42 g / mL. A comparison between Comparative Example 2 and Example 1 shows that, based on ternary atmosphere activation, the injection of the dibasic catalyst and the subsequent hydrogen reduction treatment jointly contribute approximately 270 m² of specific surface area gain. 2 / g (from 1483 m) 2 / g increased to 1756 m 2 The surface oxygen concentration decreased by approximately 1.1 mmol / g (from 1.63 mmol / g to 0.50 mmol / g), demonstrating that the dual-base catalyst injection process and the hydrogen reduction process make independent and substantial contributions to the performance improvement of the prepared carbon-based materials.

[0039] Comparative Example 3 The purpose of this Comparative Example 3 is to verify the independent contribution of the two-stage nitrogen passivation-hydrogen reduction post-treatment process to the surface chemical stability of the prepared carbon-based material. The difference between this Comparative Example and Example 1 is that the initial ternary atmosphere activation and dual-base catalyst injection processes remain unchanged, and only the high-temperature nitrogen passivation-hydrogen reduction treatment in step four is omitted.

[0040] The specific preparation steps are as follows. Steps one, two, and three are exactly the same as in Example 1. During the activation stage, a ternary gas mixture of 2.0 g / min steam, 0.3 g / min ammonia, and 0.2 L / min carbon dioxide is introduced, and a dual-base catalyst of 0.3% potassium carbonate and 0.1% sodium hydroxide is sprayed in. The activation temperature is 900℃, and the activation time is 4-5 h. After activation, the material is subjected to a three-stage acid washing, water washing, drying, and grinding. Step four is not performed; the material dried and ground in step three is directly used as the product of Comparative Example 3.

[0041] The activated carbon material prepared in Comparative Example 3 was characterized and tested to have a specific surface area of ​​1720 m². 2The specific surface area was 0.78 mL / g, the pore volume was 0.78 mL / g, the surface oxygen concentration was 1.80 mmol / g, and the bulk density was 0.44 g / mL. A comparison between Comparative Example 3 and Example 1 shows that the pre-treatment ternary atmosphere activation and dual-base catalyst injection process contributed the vast majority of the gains to the specific surface area, pore volume, and bulk density of the prepared carbon-based material (the specific surface area reached 1720 m² / g). 2 While the bulk density has reached 0.44 g / mL, the independent contribution of the two-stage post-treatment process is mainly reflected in the further reduction of the surface oxygen concentration (from 1.80 mmol / g to 0.50 mmol / g, a reduction of approximately 72%). This indicator has a decisive impact on the cyclic charge-discharge stability of carbon-based materials in supercapacitor electrode applications. This comparative example verifies the necessity of integrating the front-end ternary gas activation pore-forming nitrogen embedding and the back-end hydrogen reduction surface stabilization process.

[0042] Comparative Example 4 The purpose of this Comparative Example 4 is to verify the effect of the discharge rate of the rotary activation furnace on the properties of the prepared carbon-based material, so as to determine the reasonable boundaries of the process parameters described in this invention. The difference between this Comparative Example and Example 1 is that the discharge rate of the rotary activation furnace is increased from 1.1 g / min to 1.5 g / min, which shortens the residence time of the carbonized material in the activation furnace by about 36%, while other parameters remain unchanged.

[0043] The specific preparation steps are as follows. Steps one, three, and four are exactly the same as in Example 1. In step two, the carbonized material is placed in an externally heated, sealed rotary activation furnace at an activation temperature of 900℃ for 2-3 hours; a ternary mixed activation gas of 2.0 g / min steam, 0.3 g / min ammonia, and 0.2 L / min carbon dioxide is introduced; a dual-base catalyst of 0.3% potassium carbonate and 0.1% sodium hydroxide is injected; the feed rate of the carbonized material is kept constant at 3 g / min, but the discharge rate is increased from 1.1 g / min to 1.5 g / min by increasing the rotary furnace speed.

[0044] The activated carbon material prepared in Comparative Example 4, after characterization testing, showed a specific surface area of ​​only 902 m². 2 The micropore volume was 0.4 mL / g, the surface oxygen concentration was 0.5 mmol / g, and the bulk density was 0.55 g / mL. A comparison between Comparative Example 4 and Example 1 showed that the increased discharge rate of the rotary activation furnace resulted in insufficient residence time of the carbonized material in the activation atmosphere, incomplete reaction between the ternary atmosphere and the carbon skeleton, and severely insufficient pore depth. Consequently, the specific surface area and micropore volume of the resulting material decreased significantly, failing to reach the ≥1600 μm² required by this invention. 2The specific surface area index requirement is / g. This comparative example verifies that the process parameter boundary within the discharge rate range of 0.8~1.5 g / min, preferably within the range of 1.0~1.1 g / min, as described in this invention, has substantial technical significance.

[0045] The specific testing methods for the various performance indicators described in this invention are as follows.

[0046] Specific surface area was measured using a Micromeritics ASAP 2020M fully automated specific surface area and microporous physical adsorption analyzer, with high-purity nitrogen as the adsorbate, and N2 isothermal adsorption-desorption was performed at liquid nitrogen temperature of 77 K. Before the test, the sample was degassed under vacuum at 300℃ for 4 h. The specific surface area was calculated using the BET (Brunauer-Emmett-Teller) multi-point method with fitting within the relative pressure P / P0 range of 0.05 to 0.30.

[0047] The micropore volume test was conducted concurrently with the BET test. The t-plot method was used to calculate the micropore volume, and the BJH (Barrett-Joyner-Halenda) method was used to calculate the mesopore volume. The sum of the two was the micropore volume. The pore size distribution was calculated using density functional theory (DFT). The micropore region was fitted based on the HK (Horvath-Kawazoe) slit model, and the mesopore region was fitted based on the BJH model.

[0048] The elemental distribution and nitrogen-containing functional group types on the carbon framework surface were measured using a Thermo Fisher ESCALAB250Xi X-ray photoelectron spectroscopy (XPS) instrument, excited by a monochromatic Al Kα source (hν = 1486.6 eV), with a vacuum level in the analysis chamber better than 2 × 10⁻⁶. -9 mbar, pass energy 50 eV (narrow scan) and 150 eV (full scan), binding energy corrected with C 1s (284.8 eV) as internal standard; N 1s spectrum was fitted using XPSPEAK 4.1 software, corresponding to four types of nitrogen-containing functional groups: pyridine nitrogen (398.3~398.7 eV), pyrrole nitrogen (400.0~400.5 eV), graphitic nitrogen (401.0~401.5 eV), and quaternary nitrogen oxides (402.5~403.5 eV). Particle morphology was observed using a Hitachi SU8010 field emission scanning electron microscope (SEM) with an accelerating voltage of 5 kV and a working distance of 8 mm; microporous structure was observed using a FEI Tecnai G2 F20 field emission transmission electron microscope (TEM) with an accelerating voltage of 200 kV.

[0049] The surface oxygen concentration was determined using the Boehm titration method. The specific procedure was as follows: 0.5 g of carbon-based powder sample was weighed and added to 50 mL of 0.05 mol / L NaHCO3, Na2CO3, NaOH, and HCl solutions, respectively. The solutions were sealed and shaken for 24 h. After filtration, the supernatant was collected and back-titrated with 0.05 mol / L hydrochloric acid or 0.05 mol / L NaOH. The concentrations of carboxyl groups, lactone groups, phenolic hydroxyl groups, and total basic functional groups on the carbon-based material surface were calculated based on the consumption of each alkali solution. The total oxygen concentration was the sum of the concentrations of carboxyl groups, lactone groups, and phenolic hydroxyl groups.

[0050] The bulk density was determined according to GB / T 1252.1-2019 "Determination of Packing Density of Granular Activated Carbon". The carbon-based powder sample was packed into a 100 mL graduated cylinder, freely vibrated until volume stabilized, and then weighed. The bulk density was calculated by dividing the mass by the volume, with units of g / mL. Volatile matter was tested according to GB / T 212-2008 "Industrial Analysis Methods for Coal". The carbonized material was placed in a covered crucible and ignited at 900℃ for 7 min. The volatile matter content was expressed as a weight loss fraction. Oxygen content was monitored using a Zirox SGM5 zirconia oxygen sensor (Germany), with a range of 0–25%, a resolution of 0.001%, and a response time ≤2 s. The content of ternary activated gas components was monitored online using a Shimadzu GC-2014 gas chromatograph (Japan), equipped with a TCD detector and an FID detector, with high-purity helium as the carrier gas.

[0051] To quantitatively evaluate the cyclic charge-discharge stability of the prepared carbon-based high specific surface area material in supercapacitor electrode applications, a Bio-Logic SP-150 electrochemical workstation (France) was used to perform constant current charge-discharge tests and cyclic voltammetry tests on the material. Specifically, the prepared carbon-based high specific surface area material, polytetrafluoroethylene binder, and acetylene black conductive agent were mixed at a mass ratio of 8:1:1 to prepare an electrode slurry, which was then coated onto a stainless steel current collector. The electrode active material loading was approximately 3 mg / cm³. 2 A symmetrical button-type supercapacitor was assembled using a 6 mol / L KOH aqueous solution as the electrolyte. Constant current charge-discharge tests were conducted within a voltage window of 0–1.0 V, with current densities ranging from 1 A / g to 10 A / g. Cyclic stability tests were performed by continuously cycling 10,000 times at a current density of 5 A / g, recording the initial specific capacitance and the specific capacitance after 10,000 cycles, and calculating the capacitance retention rate. The material obtained in Example 1 had a specific capacitance of 285 F / g at a current density of 1 A / g, and a capacitance retention rate of 94% after 10,000 cycles. The material obtained in Comparative Example 3 had an initial specific capacitance of 272 F / g under the same test conditions, but a capacitance retention rate of only 68% after 10,000 cycles. This quantitatively demonstrates that the two-stage post-processing technology described in this invention makes an irreplaceable and crucial contribution to the cyclic stability of the electrode.

[0052] The process parameters and performance indicators of the carbon-based high specific surface area materials prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention are summarized in Table 1.1.

[0053] Table 1.1 Summary of process parameters and performance indicators for the examples and comparative examples The performance data listed in Table 1.1 can be used to demonstrate the nonlinear synergistic effect of the process integration described in this invention from three levels.

[0054] The first level is the pore-forming gain of ternary atmosphere activation compared to single water vapor activation. Comparing Example 2 (ternary atmosphere activation, no catalyst, post-treatment) with Comparative Example 1 (single water vapor activation, no catalyst, no post-treatment), Example 2 achieves a specific surface area of ​​1652 m². 2 / g, compared to 1152 m in Comparative Example 1 2 / g increased by 43.5%; pore volume increased from 0.6 mL / g to 0.7 mL / g, an increase of 16.7%. This gain indicates that the introduction of ammonia and carbon dioxide, compared with a single water vapor atmosphere, can simultaneously increase the pore-forming rate and pore-forming depth. The nitrogen free radicals generated by the decomposition of ammonia play a dual role as a catalyst and nitrogen source in the pore-forming reaction.

[0055] The second level is the independent contribution of the dual-salt catalyst. Comparing Example 1 (ternary gas + dual-salt catalyst + post-treatment) and Comparative Example 3 (ternary gas + dual-salt catalyst + no post-treatment), the specific surface areas of Example 1 and Comparative Example 3 are 1756 m², respectively. 2 / g and 1720 m 2 / g, the difference is only about 30 m 2 / g indicates that the dibasic catalyst, in the presence of a ternary atmosphere, can advance the activation depth to near its limit; further comparison between Comparative Example 2 (ternary atmosphere + no catalyst + no post-treatment) and Comparative Example 3 (ternary atmosphere + dibasic catalyst + no post-treatment) shows that the dibasic catalyst... The chemical agent increased the specific surface area from 1483 m² 2 / g increased to 1720 m 2 / g, independent contribution 237 m 2 / g, proving that the dual-base catalyst has an irreplaceable pore-forming and deepening effect in a ternary atmosphere.

[0056] The third level involves the crucial role of the two-stage post-treatment in shaping surface chemical properties. Comparing Example 1 (ternary atmosphere + dual-salt catalyst + post-treatment) with Comparative Example 3 (ternary atmosphere + dual-salt catalyst + no post-treatment), the specific surface area, pore volume, and packing density are almost identical, but the surface oxygen concentrations are 0.50 mmol / g and 1.80 mmol / g, respectively, a difference of 3.6 times. This result quantitatively demonstrates that the nitrogen passivation-hydrogen reduction two-stage post-treatment process has a specific stabilizing effect on the surface chemical properties of carbon-based materials and does not destructively affect the carefully constructed pore structure in the preceding stage. In summary, the integrated three-stage process of ternary atmosphere + dual-salt catalyst + two-stage post-treatment described in this invention produces a comprehensive performance (specific surface area ≥1600 m²). 2 The combined index of / g+surface oxygen content ≤0.5 mmol / g+bulk density ≥0.44 g / mL far exceeds the simple summation of the independent contributions of each component, exhibiting a significant nonlinear synergistic effect. Comparative Example 4 further demonstrates that the discharge rate process parameter boundary (preferably 1.0~1.1 g / min) described in this invention has substantial technical significance. Exceeding this boundary will lead to insufficient residence time of the carbonized material, preventing the synergistic effect of the ternary atmosphere and the dual-salt catalyst from being fully realized.

[0057] The fourth level is the electrochemical application performance comparison. Based on the constant current charge-discharge and cycle stability tests described in the above detection methods, the material obtained in Example 1 of this invention has a specific capacitance of 285 F / g at a current density of 1 A / g, and the capacitance retention rate reaches 94% after 10,000 cycles; the material obtained in Example 2 has a specific surface area reduced to 1650 m² due to the lack of a dibasic catalyst. 2 / g, the specific capacitance correspondingly decreased to 265 F / g, and the cycle retention rate was 90%; although the material obtained in Example 3 had a specific surface area of ​​1790 m² 2 The specific capacitance was the highest at 0.7 mmol / g, but due to the relatively high surface oxygen concentration of 0.7 mmol / g, the specific capacitance was only 278 F / g, and the cycle retention rate was 87%. The material obtained in Comparative Example 1 had a specific surface area of ​​only 1150 m². 2 The surface oxygen concentration is as high as 2.0 mmol / g, while the specific capacitance and cycle retention are only 185 F / g and 52%, respectively, which are far lower than the levels in the embodiments of this invention. The specific capacitance data shows a strong correlation with the surface oxygen concentration and specific surface area, while the cycle retention data shows a significant negative correlation with the surface oxygen concentration. The electrochemical performance characterization results further verify the synergistic gains of the process integration described in this invention at the application level.

[0058] The synergistic gain mechanism of the carbon-based high specific surface area material preparation method described in this invention can be explained in depth from the following three dimensions.

[0059] The first dimension concerns the synergistic pore-forming and nitrogen-intercalating mechanism of simultaneous introduction of three gases. Under high-temperature activation conditions of 800 to 1000℃, water vapor reacts with disordered carbon atoms in the carbon skeleton via a water-gas reaction (C + H₂O → CO + H₂), dominating the vertical expansion of pores; carbon dioxide reacts with the carbon skeleton via a Baudelaire reaction (C + CO₂ → 2CO), dominating the lateral expansion of pores and regulating pore size distribution; ammonia partially decomposes into nitrogen free radicals at high temperatures (NH₃ → ·NH₂ + ·H, ·NH + ·H₂), and these nitrogen free radicals undergo substitution reactions with carbon atoms at the carbon skeleton edges, embedding nitrogen atoms into the carbon skeleton to form various nitrogen-containing sites such as pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen. Compared to binary or single-atmosphere systems, the simultaneous introduction of these three gases enables precise spatiotemporal coupling between the pore-forming and nitrogen-intercalating processes. The nitrogen free radicals generated by ammonia decomposition preferentially fill the active sites at the edges of pores newly etched by water vapor and carbon dioxide, avoiding the uneven distribution of nitrogen sites caused by sequential gas introduction where pore-forming occurs before nitrogen intercalation. Meanwhile, real-time control of oxygen content in the activation furnace minimizes the oxidation loss of ammonia to nitrogen-containing oxide byproducts, maximizes the utilization rate of ammonia as a nitrogen source, and enriches the surface of the resulting carbon-based material with basic nitrogen-containing functional groups such as pyridine nitrogen, giving it high selectivity in applications such as carbon dioxide adsorption and acid gas removal.

[0060] The second dimension concerns the precise control mechanism of pore-forming depth through the injection of a dual-base catalyst. A dual-base catalyst of potassium carbonate and sodium hydroxide is dispersed into the activation furnace atmosphere via atomized injection. Compared to the solid-phase premixing of traditional chemical activation methods, the catalyst dispersion scale on the carbon skeleton surface formed by this injection method can be refined to the nanometer scale, significantly amplifying the contact interface between the catalyst and the carbon skeleton. Simultaneously, the catalyst dosage is reduced to 0.4%~0.6% of the carbonized material mass, far lower than the approximately 20%~50% of the traditional catalyst dosage in chemical activation methods. Under high-temperature activation conditions, potassium carbonate decomposes into potassium oxide and carbon dioxide (K2CO3→K2O+CO2). Potassium oxide is further reduced by the carbon skeleton to metallic potassium vapor (K2O+C→2K↑+CO). The metallic potassium vapor, with a boiling point above 762℃ at 800~1000℃, exists in a gaseous state and can enter the interlayer voids of the carbon skeleton for in-situ activation. Sodium hydroxide forms a eutectic system with potassium oxide at high temperatures, further reducing the apparent activation energy of the activation reaction and synergistically enhancing the pore-forming rate. The synergistic effect of the two salts enables the achievement of a high specific surface area level close to that of the chemical activation method even with a low catalyst dosage level of physical activation. Furthermore, due to the low catalyst dosage, the subsequent acid washing and water washing load is significantly reduced.

[0061] The third dimension concerns the surface chemical stabilization mechanism of the two-stage nitrogen passivation-hydrogen reduction post-treatment. After the initial ternary atmosphere activation and acid washing process, the resulting carbon-based powder, while possessing a well-developed porous structure and a certain nitrogen atom embedding degree, still retains a significant number of oxygen-containing functional groups such as carboxyl groups, lactone groups, and phenolic hydroxyl groups (typically at 1.5~2.0 mmol / g). These oxygen-containing functional groups can undergo irreversible redox reactions in supercapacitor electrode applications, leading to continuous capacity decay, increased leakage current, and intensified self-discharge during electrode cyclic charging and discharging. In the two-stage post-treatment process described in this invention, nitrogen is first introduced to completely purge the air and residual moisture in the atmosphere reduction furnace until the oxygen content is below the detection threshold. The key function of this step is to prevent the subsequent high-temperature hydrogen from reacting with the residual oxygen and damaging the porous structure of the carbon-based powder. After stopping the nitrogen introduction, the flow rate is 0.01 to 0.02 m³ / g. 3 A low-flow-rate hydrogen gas ( / min) at 800-1100℃ undergoes a reduction reaction with residual oxygen-containing functional groups on the surface of carbon-based powder: hydrogen reacts with carboxyl groups to generate water and CH bonds, reacts with lactone groups to generate water and CH bonds, and reacts with phenolic hydroxyl groups to generate water vapor for removal. All these reactions convert oxygen-containing functional groups into stable CH or C=C bonds, ultimately reducing the surface oxygen concentration to below 0.5 mmol / g. The low-flow-rate hydrogen gas avoids the secondary etching of the pore structure that might be caused by high-flow-rate hydrogen gas. In summary, the integrated process of the present invention—front-stage ternary gas activation for pore formation and nitrogen embedding, mid-stage three-stage acid washing for impurity removal, and rear-stage hydrogen reduction for surface chemical stabilization—enables the prepared carbon-based high specific surface area material to simultaneously meet the requirement of a specific surface area ≥1600 m². 2 It possesses comprehensive performance indicators including a pore volume ≥0.7 mL / g, a surface oxygen concentration ≤0.5 mmol / g, and a bulk density ≥0.44 g / mL, and also exhibits excellent cyclic charge-discharge stability and acid gas adsorption selectivity.

[0062] The fourth dimension concerns the causal chain coupling mechanism of the three major process features. The three major process features described in this invention—ternary atmosphere activation, dual-base catalyst injection, and two-stage nitrogen passivation-hydrogen reduction post-treatment—are not simply independent stacks, but rather form a causal recursive process chain. The high proportion of pyridine nitrogen sites (approximately 45% of the total nitrogen atoms) in the nitrogen-doped carbon framework generated by the initial ternary atmosphere activation is determined by the synchronous pairing reaction between the open edge carbon active sites formed by the simultaneous etching of water vapor and carbon dioxide and the nitrogen free radicals generated by ammonia decomposition. If only a single atmosphere or sequential gas flow is used, nitrogen free radicals will not be able to effectively occupy the newly generated edge carbon active sites, and the proportion of pyridine nitrogen will decrease significantly. The nanoscale dispersed catalytic interface formed by the injection of the mid-stage dual-base catalyst further reduces the apparent activation energy of the three-gas activation reaction, allowing the activation reaction to proceed fully within the relatively mild temperature range of 800 to 1000 °C. This avoids the risk of excessive gasification of the carbon skeleton and pore wall collapse at higher temperatures. Precise control of this temperature range, in turn, is a prerequisite for the stable retention of pyridine nitrogen sites without thermal decomposition. The oxygen-containing functional groups removed by the two-stage reduction process originally originated from oxygen atoms introduced by water vapor and carbon dioxide in the preceding ternary atmosphere. Since acid washing cannot completely remove all oxygen-containing functional groups, the subsequent stage must use high-temperature hydrogen reduction as the final deoxygenation barrier, and the hydrogen flow rate must be controlled at a low velocity to avoid damaging the carefully constructed pyridine nitrogen sites in the preceding stage. These three process characteristics form a complete closed loop through the core mechanism of the formation, retention, and stabilization of pyridine nitrogen sites, and none of them can be omitted. This causal chain coupling mechanism explains why the overall performance of the materials prepared in Comparative Example 1 (without ternary catalyst), Comparative Example 2 (without dual-salt catalyst), and Comparative Example 3 (without post-treatment) all failed to reach the level of Example 1 of this invention. Furthermore, the performance loss directions of each comparative example were different. Comparative Example 1 mainly suffered from a dual deficiency in specific surface area and pyridine nitrogen density; Comparative Example 2 mainly suffered from the difficulty in forming a bimodal structure in pore size distribution and a low specific surface area; and Comparative Example 3 mainly suffered from poor cycle stability in electrochemical applications due to excessively high surface oxygen concentration. This difference in the direction of performance loss is itself the strongest evidence of the independent contribution and synergistic coupling of the three major process characteristics.

[0063] The process route described in this invention also has significant advantages in industrial-scale application. First, the externally heated, closed-atmosphere rotary activation furnace used is a mature piece of equipment in the existing carbon industry. It only requires the addition of an ammonia and carbon dioxide metering and mixing device, a catalyst atomization and injection device, and an online oxygen content monitoring device to the existing steam activation furnace, making the increase in equipment investment controllable. Second, the catalyst dosage is reduced by approximately one order of magnitude compared to traditional chemical activation methods, significantly reducing raw material costs and post-treatment loads such as acid washing and water washing. The production cost per ton of product and environmental governance costs decrease simultaneously. Third, the resulting carbon-based high specific surface area material possesses comprehensive performance indicators combining high specific surface area, pyridine-rich nitrogen surface chemistry, and a stable electrochemical interface. It can simultaneously meet the technical requirements of three major downstream application areas: supercapacitor electrode materials, carbon dioxide selective adsorbents, and desulfurization and denitrification catalyst carriers. A single product process line can cover multiple high-value-added markets, thus diversifying market risks.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., 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 preparing a carbon-based high specific surface area material, characterized in that, Includes the following steps: S1. Wood biomass raw materials containing sawdust are carbonized at high temperature under anaerobic conditions to obtain carbonized material; S2. After crushing and screening, the carbonized material is placed in an externally heated, sealed rotary activation furnace. Activation gas is introduced at 800-1000°C for 4-8 hours. During the activation process, a catalyst is simultaneously injected into the activation furnace, and the composition content of the activation gas and the oxygen content in the activation furnace are controlled in real time. The activation gas is a ternary mixture of ammonia, water vapor, and carbon dioxide, and the catalyst contains potassium carbonate and sodium hydroxide. S3. The activated material is washed with inorganic acid, then washed with water until pH 6~7, dried and ground to obtain carbon-based powder; S4. Place the carbon-based powder in an atmosphere reduction furnace, first passivate it with nitrogen until the oxygen content in the furnace is lower than the detection threshold, then stop passing nitrogen and pass hydrogen at 800~1100℃ for reduction treatment to obtain the carbon-based high specific surface area material.

2. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The oxygen-free carbonization process described in step S1 is a two-stage carbonization process. The first stage carbonization temperature is 480℃ and the carbonization time is 2~3 h. The second stage carbonization temperature is 700℃ and the carbonization time is 1~2 h. The volatile matter mass fraction of the carbonized material is controlled at 10%~25%.

3. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The particle size of the carbonized material after crushing and screening in step S2 is 16~40 mesh; the feed rate of the carbonized material is 3 g / min, and the discharge rate of the activation furnace is 0.8~1.5 g / min.

4. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The input flow rates of the activation gas in step S2 meet the following requirements: water vapor flow rate is 2.0~2.5 g / min, and ammonia flow rate is 0.3~0.6 g / min.

5. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, In step S2, the mass percentage of the catalyst relative to the carbonized material injected is: potassium carbonate 0.3%~0.35%, sodium hydroxide 0.1%~0.25%.

6. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The inorganic acid washing in step S3 is a three-stage segmented washing process, in which hydrochloric acid, nitric acid and hydrofluoric acid are used sequentially to remove residual metal carbonates, residual nitrogen-containing oxides and silicon-based ash from the activated material.

7. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The median particle size D50 of the carbon-based powder obtained by drying and grinding in step S3 is 5~7 μm.

8. The method for preparing carbon-based high specific surface area materials according to claim 1, characterized in that, The nitrogen flow rate in step S4 is 0.05 m³. 3 The hydrogen flow rate is 0.01~0.02 m³ / min. 3 The reduction process is carried out at a rate of 900~1100℃ per minute.

9. The method for preparing carbon-based high specific surface area materials according to claim 8, characterized in that, The prepared carbon-based high specific surface area material meets at least two of the following performance indicators: specific surface area ≥ 1600 m² 2 / g; surface oxygen concentration ≤0.5 mmol / g; bulk density ≥0.44 g / mL.

10. The method for preparing carbon-based high specific surface area materials according to any one of claims 1 to 9, characterized in that, The prepared carbon-based high specific surface area materials are used as active materials for supercapacitor electrodes, selective adsorbents for carbon dioxide, or carriers for desulfurization and denitrification catalysts.

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