A method for preparing a bamboo-based porous carbon

Abstract

The application belongs to the technical field of biomass carbon material preparation, and particularly relates to a preparation method of bamboo-based porous carbon. Deionized water, anhydrous ethanol, an aqueous orthophosphoric acid solution, urea, boric acid, glucose monohydrate, polyvinylpyrrolidone and a nitrogen-phosphorus-boron gradient complex activating salt are mixed to obtain a pre-impregnation solution. After being cleaned, dried and crushed, bamboo chips are added into the pre-impregnation solution for vacuum impregnation, stirring impregnation and hydrothermal treatment to obtain a pre-complex bamboo-based precursor. Then, the pre-complex bamboo-based precursor is mixed with flaky potassium hydroxide, anhydrous potassium carbonate and a silicon-magnesium-potassium interlayer limited pore-forming agent, and is subjected to pre-carbonization, high-temperature carbonization, carbon dioxide activation, acid-alkali washing, drying and stabilization treatment to obtain the bamboo-based porous carbon. The method is conducive to improving the pore structure controllability, the heteroatom distribution uniformity and the carbon material stability.

Description

Technical Field

[0001] This invention belongs to the field of biomass carbon material preparation technology, specifically relating to a method for preparing bamboo-based porous carbon. Background Technology

[0002] Porous carbon materials, due to their well-developed pore structure, high specific surface area, good chemical stability, and tunable surface functional groups, have wide applications in adsorption separation, catalyst supports, electrochemical energy storage, environmental purification, and functional fillers. Traditional porous carbon is mostly produced from raw materials such as coal, petroleum coke, and phenolic resin through carbonization and activation. Although the process is relatively mature, it suffers from problems such as non-renewable raw materials, high energy consumption during preparation, difficulty in controlling ash and impurities, and reliance on highly corrosive activators for pore structure regulation. With the increasing demand for green manufacturing and resource recycling, the preparation of porous carbon using agricultural and forestry biomass as a carbon source is gradually gaining attention. Bamboo, with its short growth cycle, abundant sources, and low price, and its natural multi-level structure containing fiber bundles, vessels, and thin-walled cells, is suitable as a precursor for preparing hierarchical porous carbon materials.

[0003] Existing methods for preparing bamboo-based porous carbon typically involve pretreatment, carbonization, chemical activation, physical activation, and washing and purification. Commonly used activation systems include phosphoric acid, potassium hydroxide, potassium carbonate, and carbon dioxide or water vapor. Phosphoric acid can promote the dehydration and cross-linking of bamboo components and improve carbon yield. Potassium hydroxide and potassium carbonate can etch the carbon framework at high temperatures and form micropores. Carbon dioxide activation can further expand pores and improve pore connectivity. However, a single activation method often fails to simultaneously achieve micropore formation, mesopore regulation, and carbon framework stability. Strong alkali activation can easily cause localized over-etching and reduced yield, while excessively strong phosphoric acid pretreatment may lead to excessive dehydration of bamboo, structural shrinkage, or pore blockage. Furthermore, the non-uniform internal structure of bamboo makes it difficult for ordinary impregnation methods to uniformly introduce activators and dopants into the interfiber gaps and cell cavities, easily resulting in porous carbon with a wide pore size distribution, insufficient batch stability, and uneven distribution of surface active sites.

[0004] Furthermore, existing bamboo-based porous carbon still has shortcomings in terms of functionalization. To improve wettability, conductivity, adsorption activity, and electrochemical reaction sites, heteroatoms such as nitrogen, phosphorus, and boron are often introduced. However, the common methods of adding urea, boric acid, or phosphates are prone to uneven migration, precipitation, or thermal decomposition of dopant components, making it difficult to form stable synergistic effects. On the other hand, mesoporous and interconnected pore structures usually rely on template agents for regulation, but conventional template agents are costly, have complex removal steps, and limited compatibility with bamboo-based precursors. Therefore, there is an urgent need to develop a method for preparing bamboo-based porous carbon that takes into account low-cost raw materials, uniform pre-complexation, synergistic introduction of heteroatoms, confined pore formation, and acid-base purification, in order to improve the controllability of pore structure, uniformity of heteroatom distribution, stability of carbon framework, and adaptability for industrial preparation. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing bamboo-based porous carbon, comprising the following steps:

[0006] S1. By weight, mix 220.0-360.0 parts deionized water, 15.0-45.0 parts anhydrous ethanol, 18.0-42.0 parts orthophosphoric acid aqueous solution, 8.0-24.0 parts urea, 2.0-8.0 parts boric acid, 3.0-12.0 parts glucose monohydrate, 0.5-2.5 parts polyvinylpyrrolidone and 5.0-14.0 parts nitrogen-phosphorus-boron gradient complexing activated salt to obtain a pre-impregnation solution;

[0007] S2. Clean and dry 100.0-120.0 parts of bamboo strips to obtain pretreated bamboo strips; crush the pretreated bamboo strips to obtain bamboo powder; add the bamboo powder to the pre-impregnation liquid for vacuum impregnation and stirring impregnation to obtain impregnated bamboo powder; subject the impregnated bamboo powder to hydrothermal treatment, filter, and dry to obtain pre-complexed bamboo-based precursor.

[0008] S3. Mix the pre-complexed bamboo-based precursor, 65.0-135.0 parts of flake potassium hydroxide, 8.0-26.0 parts of anhydrous potassium carbonate, and 3.0-10.0 parts of potassium magnesium silicate interlayer confinement pore-forming agent to obtain an activated mixture; under nitrogen protection, pre-carbonize and high-temperature carbonize the activated mixture to obtain a carbonized activated material; activate the carbonized activated material with carbon dioxide gas, cool it, and wash it sequentially with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water, then dry and stabilize it.

[0009] In this invention, the preparation mechanism of bamboo-based porous carbon is to use the natural vascular bundles and fiber channels of moso bamboo as the initial structural basis, and to achieve synergistic regulation of pore structure and heteroatom components through pre-impregnation, hydrothermal pre-complexation, alkali-salt activation, carbon dioxide gas activation and acid-base washing. Deionized water and anhydrous ethanol together improve the dispersion and wetting state of orthophosphoric acid aqueous solution, urea, boric acid, glucose monohydrate, polyvinylpyrrolidone, and nitrogen-phosphorus-boron gradient complex activated salt in the preimpregnation solution. Orthophosphoric acid aqueous solution can promote the dehydration, bond breaking, condensation, and pre-crosslinking of cellulose, hemicellulose, and lignin in bamboo chips, which is beneficial to improving the subsequent carbon skeleton retention rate. During hydrothermal treatment, glucose monohydrate undergoes dehydration and condensation to form carbon intermediates rich in oxygen-containing functional groups, which can supplement the carbon source and bind the inner wall of the bamboo powder pores. Urea and boric acid provide nitrogen and boron sources, respectively, while nitrogen-phosphorus-boron gradient complex activated salt provides pre-dispersed nitrogen, phosphorus, boron, and potassium salt components. Polyvinylpyrrolidone improves the wetting and dispersion uniformity of the bamboo powder surface by the preimpregnation solution. After cleaning and drying, bamboo chips are free of surface impurities and free water. Pulverization exposes more cell cavities, vessels, and interfiber spaces. Vacuum impregnation removes air from the bamboo powder, allowing the pre-impregnation solution to enter the natural pores. Stirring during impregnation ensures the active components adhere evenly to the surface and internal pore walls of the bamboo powder. During hydrothermal treatment, the natural polymers in the bamboo powder undergo hydrolysis, dehydration, and condensation. Orthophosphoric acid aqueous solution, boric acid, urea, glucose monohydrate, and nitrogen-phosphorus-boron gradient complexing activated salts form a pre-complexed bamboo-based precursor with the bamboo matrix structure. This precursor, mixed with flake potassium hydroxide, anhydrous potassium carbonate, and potassium magnesium silicate interlayer confinement pore-forming agent, undergoes pre-carbonization under nitrogen protection. Volatile components are gradually released, forming an initial carbon skeleton. During high-temperature carbonization, flake potassium hydroxide and anhydrous potassium carbonate undergo etching and vaporization-related reactions with the carbon skeleton, accompanied by potassium species intercalation and diffusion, promoting the formation of numerous micropores. Nitrogen, phosphorus, and boron components condense with the carbon skeleton and enter surface or edge defect sites, forming heteroatom-doped structures. The silicon-magnesium-potassium interlayer confinement pore-forming agent provides inorganic spatial barriers around the carbon skeleton, reducing skeleton collapse caused by local strong alkali enrichment and inducing the formation of mesopores and interconnected pores. Subsequently, carbon dioxide gas activation further vaporizes the activated carbon sites, expanding some micropores and improving pore connectivity. After cooling, sequential washing with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water removes residual potassium salts, magnesium-silicon inorganic components, and soluble impurities. Drying and stabilization treatments further shrink and rearrange the carbon skeleton, ultimately forming bamboo-based porous carbon with rich pore structure, uniform heteroatom distribution, and stable structure.

[0010] According to a preferred embodiment of the present invention, in step S1, the mass fraction of the orthophosphoric acid aqueous solution is 85%; the polyvinylpyrrolidone is polyvinylpyrrolidone K30; the mixing temperature is 45-60°C, and the mixing time is 1-3 hours.

[0011] According to a preferred embodiment of the present invention, in step S2, the vacuum impregnation time is 1-3 hours; the stirring impregnation time is 2-4 hours; the hydrothermal treatment temperature is 160-190°C; and the hydrothermal treatment time is 4-8 hours.

[0012] According to a preferred embodiment of the present invention, in step S3, the pre-carbonization temperature is 430-480℃, and the pre-carbonization time is 0.5-1.5h; the high-temperature carbonization temperature is 780-860℃, and the high-temperature carbonization time is 1.0-2.5h; the activation temperature is 820-880℃, and the activation time is 20-70min; the stabilization treatment temperature is 850-950℃, and the stabilization treatment time is 0.5-1.5h.

[0013] According to a preferred embodiment of the present invention, the method for preparing the nitrogen-phosphorus-boron gradient complexing activated salt includes:

[0014] A1. By weight, mix 100.0-130.0 parts deionized water, 12.0-20.0 parts citric acid monohydrate, 25.0-40.0 parts urea, 20.0-35.0 parts ammonium dihydrogen phosphate, 6.0-14.0 parts boric acid and 3.0-8.0 parts sodium gluconate monohydrate, stir at 55-65℃, add 10.0-22.0 parts anhydrous potassium carbonate, adjust the pH to 6.2-6.8, continue stirring, concentrate under reduced pressure to obtain a concentrated nitrogen-phosphorus-boron complex salt solution;

[0015] A2. Add 80.0-160.0 parts of anhydrous ethanol to the nitrogen-phosphorus-boron complex salt concentrate, let stand, filter, dry, carry out solid-phase complexation and shaping under nitrogen protection, cool, pulverize, and sieve.

[0016] In this invention, the preparation mechanism of the nitrogen-phosphorus-boron gradient complex activated salt lies in the formation of a uniformly dispersed composite activation system of nitrogen, phosphorus, boron, and potassium sources through aqueous phase complexation, salting buffering, solvent precipitation, and solid-phase fixation. Deionized water fully dissolves and disperses citric acid monohydrate, urea, ammonium dihydrogen phosphate, boric acid, and sodium gluconate monohydrate. Citric acid monohydrate contains carboxyl and hydroxyl groups, which can form multi-point complexes and hydrogen bonds with the ammonium, potassium, boric acid, and phosphate components. Sodium gluconate monohydrate contains carboxyl groups and multiple hydroxyl groups, which can form synergistic complexes with ammonium, potassium, and boric acid, thereby improving the aqueous phase stability of the composite salt system and reducing local salt precipitation and aggregation. In this system, urea acts as the nitrogen-containing component. Its carbonyl and amino groups form hydrogen bonds with the carboxylates, phosphates, and borates of citric acid monohydrate, sodium gluconate monohydrate, ammonium dihydrogen phosphate, and boric acid. Ammonium dihydrogen phosphate partially dissociates in the aqueous phase, providing phosphorus and ammonium ions, while boric acid provides boron. Acidic hydrogen bonds form between phosphates and borates. Upon addition of anhydrous potassium carbonate, the acidic environment formed by citric acid monohydrate and ammonium dihydrogen phosphate is gradually neutralized and buffered. Potassium ions enter the complex salt network, and the system transitions from an acidic state to a near-neutral state with suitable complexation, strengthening the salting-out effects between hydrogen phosphate, phosphate, borate, citrate, and gluconate ions and ammonium and potassium ions. Continued stirring and vacuum concentration increase the concentration of each component, further enhancing the interactions between carboxylates, phosphates, borates, ammonium salts, and potassium salts, resulting in a uniformly dispersed nitrogen-phosphorus-boron complex salt concentrate. After adding anhydrous ethanol, the solvent polarity of the system decreases, the solubility of the composite salt component decreases and it gradually precipitates. After standing, filtering and drying, a solid composite salt precursor is formed. Solid-phase complexation and shaping under nitrogen protection can avoid significant oxidation of nitrogen-containing components and carbon-containing organic components, and allow the nitrogen, phosphorus, boron and potassium components in the composite salt precursor to further form a stable gradient complex structure. The resulting nitrogen-phosphorus-boron gradient complex activated salt can simultaneously provide nitrogen, phosphorus, boron and potassium salt activation components in the subsequent preparation of bamboo-based porous carbon, and improve the dispersion uniformity of dopant components in the bamboo-based precursor through the pre-complexation state.

[0017] According to a preferred embodiment of the present invention, in step A1, the stirring time at 55-65°C is 20-40 min; the stirring temperature is 75-85°C, and the stirring time is 1.5-3.0 h.

[0018] According to a preferred embodiment of the present invention, in step A2, the standing temperature is 4-8°C and the standing time is 6-12h; the drying temperature is 70-80°C and the drying time is 6-10h; the solid phase complexation and shaping temperature is 110-125°C and the solid phase complexation and shaping time is 2-4h.

[0019] According to a preferred embodiment of the present invention, the preparation method of the silicon-magnesium-potassium interlayer confinement pore-forming agent includes:

[0020] B1. By weight, mix 50.0-70.0 parts of deionized water and 18.0-32.0 parts of sodium metasilicate pentahydrate, and stir at 40-50℃ to obtain a silicate solution; mix 50.0-70.0 parts of deionized water, 12.0-24.0 parts of magnesium chloride hexahydrate, 8.0-18.0 parts of anhydrous potassium chloride, 3.0-8.0 parts of potassium citrate monohydrate, and 4.0-10.0 parts of urea to obtain a magnesium potassium salt solution; add the magnesium potassium salt solution to the silicate solution, adjust the pH to 9.5-10.5, add 1.0-4.0 parts of polyethylene glycol 400, and continue stirring to obtain an interlayer confined suspension;

[0021] B2. The interlayer confined suspension is subjected to hydrothermal reaction, cooling, solid-liquid separation, washing, drying, calcination, and pulverization.

[0022] In this invention, the preparation mechanism of the magnesium-potassium interlayer confined pore-forming agent lies in utilizing sodium metasilicate pentahydrate to provide silicate structural units, magnesium chloride hexahydrate to provide magnesium ions, and anhydrous potassium chloride and potassium citrate monohydrate to regulate the ionic environment. Through hydrothermal rearrangement and calcination, an inorganic layered structure capable of confined activation reactions is formed. Sodium metasilicate pentahydrate dissolves in deionized water to form an alkaline silicate solution, where the silicate structural units exhibit hydrolysis and condensation tendencies. Magnesium chloride hexahydrate releases magnesium ions upon dissolving in deionized water, while anhydrous potassium chloride provides potassium ions. The carboxylate groups in potassium citrate monohydrate complex and disperse magnesium ions, reducing the coarse agglomeration caused by the instantaneous precipitation of magnesium ions with silicate structural units. When the magnesium-potassium salt solution is added to the silicate solution, magnesium ions gradually enter the silicate hydrolysis and condensation system, forming a hydrated magnesium silicate precursor with the silicate structural units. Potassium ions are distributed on the particle surface and in the interlayer region, giving the resulting precursor a potassium salt environment. After adjusting the pH to a suitable weakly alkaline range, the magnesium-silicon deposition transitions from rapid gelation to more uniform nucleation and growth, which is conducive to the formation of lamellar, loosely interlayered magnesium-silicon potassium precursors. Urea undergoes slow hydrolysis during the hydrothermal reaction, releasing alkaline components. Combined with the complexing effect of potassium citrate monohydrate, this makes the growth of the magnesium-silicon structure more gradual and orderly. Polyethylene glycol 400 plays a dispersing and spatial isolating role in the system; its flexible segments adsorb onto the surface of inorganic particles, reducing hard agglomeration between particles and leaving fine pores during subsequent heat treatment. After hydrothermal reaction, the hydrated magnesium silicate structure of the interlayer confined suspension further rearranges, with potassium and magnesium ions stably distributed between the silicate layers, forming a lamellar, ordered magnesium-silicon potassium interlayer framework. After cooling, solid-liquid separation, washing, and drying, the calcination process removes adsorbed water, some structural water, and residual polyethylene glycol 400, solidifying the interlayer structure and forming an inorganic framework that can participate in confined pore formation. This silicon-magnesium-potassium interlayer confining pore-forming agent does not consume the bamboo-based carbon skeleton as a strong reactant during high-temperature carbonization. Instead, it exists as a dispersed inorganic confining phase, which can buffer the excessive etching of the local carbon skeleton by the flake potassium hydroxide and anhydrous potassium carbonate, and provide spatial constraints and template guidance for the formation of mesopores and interconnecting pores.

[0023] According to a preferred embodiment of the present invention, in step B1, the stirring time at 40-50°C is 30-50 min.

[0024] According to a preferred embodiment of the present invention, in step B2, the hydrothermal reaction temperature is 140-170°C and the hydrothermal reaction time is 8-12h; the drying temperature is 90-105°C and the drying time is 8-12h; the calcination temperature is 450-550°C and the calcination time is 2-3h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) This invention uses bamboo chips as a carbon source and prepares a pre-impregnation solution by mixing deionized water, anhydrous ethanol, orthophosphoric acid aqueous solution, urea, boric acid, glucose monohydrate, polyvinylpyrrolidone, and nitrogen-phosphorus-boron gradient complexing activation salts. This allows the bamboo powder to fully contact the active components during vacuum impregnation and stirring impregnation. The orthophosphoric acid aqueous solution promotes the dehydration and cross-linking of bamboo matrix components, glucose monohydrate can supplement the carbon source, polyvinylpyrrolidone improves the wetting and dispersion state, and the nitrogen-phosphorus-boron gradient complexing activation salts allow nitrogen, phosphorus, boron, and potassium salt components to enter the bamboo matrix structure in a more uniform state, thereby improving the compositional uniformity of the pre-complexed bamboo matrix precursor and reducing structural fluctuations caused by local activator enrichment.

[0027] (2) In this invention, a pre-complexed bamboo-based precursor is used in combination with flake potassium hydroxide, anhydrous potassium carbonate, and potassium magnesium silicate interlayer confinement pore-forming agent to achieve carbon skeleton construction, alkali salt activation, and heteroatom introduction during pre-carbonization and high-temperature carbonization. Flake potassium hydroxide and anhydrous potassium carbonate are beneficial for forming microporous structures, and nitrogen-phosphorus-boron gradient complexing activation salt can improve the uniformity of nitrogen, phosphorus, and boron components on the carbon skeleton surface and defect sites, so that the resulting bamboo-based porous carbon has a good degree of pore development, surface polarity, and number of active sites, which is beneficial for improving its application performance in adsorption separation, catalyst support, and electrochemical energy storage materials.

[0028] (3) This invention employs a silicon-magnesium-potassium interlayer confinement pore-forming agent to regulate the pore-forming behavior during the high-temperature carbonization process. The inorganic interlayer structure formed by sodium metasilicate pentahydrate, magnesium chloride hexahydrate, anhydrous potassium chloride, potassium citrate monohydrate, urea, and polyethylene glycol 400 can play a spatial confinement and template guiding role around the carbon skeleton, reducing the excessive etching of the local carbon skeleton by the sheet-like potassium hydroxide and anhydrous potassium carbonate, and promoting the formation of mesopores and interconnected pores. Carbon dioxide gas activation further improves the pore connectivity. Sequential washing with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water can remove residual potassium salts and inorganic template components, thereby obtaining bamboo-based porous carbon with rich pore structure, uniform heteroatom distribution, low ash residue, and stable structure. Detailed Implementation

[0029] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing bamboo-based porous carbon, the steps of which include:

[0032] S1. Add 290.0g of deionized water to a stirring container, then add 30.0g of anhydrous ethanol, 30.0g of 85% orthophosphoric acid aqueous solution, 16.0g of urea, 5.0g of boric acid, 7.5g of glucose monohydrate, 1.5g of polyvinylpyrrolidone K30 and 9.5g of nitrogen-phosphorus-boron gradient complexing activated salt in sequence. Mix at 52.5°C for 2 hours to fully disperse the orthophosphoric acid aqueous solution, urea, boric acid, glucose monohydrate, polyvinylpyrrolidone K30 and nitrogen-phosphorus-boron gradient complexing activated salt in deionized water and anhydrous ethanol to obtain a pre-impregnation solution.

[0033] S2. Wash 110.0g of bamboo chips three times with deionized water to remove surface dust and visible impurities. Dry at 90°C for 10 hours to obtain pretreated bamboo chips. Crush the pretreated bamboo chips and pass them through a 60-mesh sieve to obtain bamboo powder. Add all the bamboo powder to the pre-impregnation solution, ensuring the bamboo powder is completely submerged and wetted. Vacuum impregnate at -0.08MPa for 2 hours, then restore to normal pressure and stir for 3 hours to obtain impregnated bamboo powder. Transfer the impregnated bamboo powder and the remaining pre-impregnation solution to a hydrothermal reactor, filling the reactor to 70% of its effective volume. Seal the reactor and hydrothermally treat at 175°C for 6 hours. After the reaction, allow it to cool naturally to 25°C. Filter and collect the solid. Dry the obtained solid at 105°C to constant weight to obtain a pre-complexed bamboo-based precursor. Constant weight means that the mass difference between two consecutive weighings is no greater than 0.1%.

[0034] S3. Add all the pre-complexed bamboo-based precursor, 100.0g of flake potassium hydroxide, 17.0g of anhydrous potassium carbonate, and 6.5g of potassium magnesium silicate interlayer confinement pore-forming agent to a mixing container. Mix thoroughly until the flake potassium hydroxide, anhydrous potassium carbonate, and potassium magnesium silicate interlayer confinement pore-forming agent are uniformly adhered to the surface of the pre-complexed bamboo-based precursor to obtain an activated mixture. Place the activated mixture in a tube furnace and purge with nitrogen gas (99.99% purity, 300mL / min) for protection. Pre-carbonize at 455°C for 1 hour, then high-temperature carbonize at 820°C for 1.75 hours to obtain a carbonized activated material. After high-temperature carbonization, switch to carbon dioxide gas. The purity was 99.9%, the carbon dioxide gas flow rate was 200 mL / min, and it was activated at 850°C for 45 min. After activation, nitrogen protection was switched and the mixture was cooled to 25°C. The cooled carbonized activated material was washed sequentially with 1.0 mol / L hydrochloric acid aqueous solution until no obvious bubbles were generated, washed with deionized water until the pH of the washing solution was 7.0, washed with 0.5 mol / L sodium hydroxide aqueous solution, and washed again with deionized water until the pH of the washing solution was 7.0. The solid was collected by filtration, dried at 105°C to constant weight, and then stabilized at 900°C for 1 h. After stabilization, the mixture was cooled to 25°C under nitrogen protection to obtain bamboo-based porous carbon.

[0035] Preparation steps of nitrogen-phosphorus-boron gradient complexing activated salt:

[0036] A1. Add 115.0g of deionized water to a reaction vessel, then add 16.0g of citric acid monohydrate, 32.5g of urea, 27.5g of ammonium dihydrogen phosphate, 10.0g of boric acid, and 5.5g of sodium gluconate monohydrate sequentially. Stir at 60°C for 30 minutes to completely dissolve the citric acid monohydrate, urea, ammonium dihydrogen phosphate, boric acid, and sodium gluconate monohydrate, forming a uniform, transparent to slightly turbid mixture. Slowly add 16.0g of anhydrous potassium carbonate to the mixture, controlling the system to prevent obvious clumping during the addition process. After the addition is complete, continue stirring, use a pH meter to detect and adjust the pH to 6.5. Then, raise the temperature of the system to 80°C and continue stirring for 2.25 hours to allow the acidic component, ammonium salt component, boric acid component, gluconate component, and potassium salt component to fully complex. After the reaction is complete, concentrate under reduced pressure at 55°C and -0.08MPa until the system is in a uniform viscous state with a solid content of 50.0%, obtaining a concentrated nitrogen-phosphorus-boron complex salt solution.

[0037] A2. Add 120.0g of anhydrous ethanol to the concentrated NPK compound salt solution and stir at 25°C for 15min to mix the system evenly. Then transfer it to a 6°C environment and let it stand for 9h to allow the compound salt components to precipitate. After standing, filter the solution with a 200-mesh filter cloth and collect the precipitated solid. Place the obtained solid in a 75°C forced-air drying environment for 8h and then transfer it to a nitrogen-protected environment with a nitrogen purity of 99.99% and a nitrogen flow rate of 200mL / min. Perform solid-phase complexation and fixation at 117.5°C for 3h. After fixation, cool the solution to 25°C under nitrogen protection, remove the solid, pulverize it, and sieve it to obtain the NPK gradient complex activated salt.

[0038] Preparation steps of silicon-magnesium-potassium interlayer confinement pore-forming agent:

[0039] B1. Add 60.0g of deionized water to a reaction vessel, add 25.0g of sodium metasilicate pentahydrate, and stir at 45°C for 40min to obtain a silicate solution; separately take 60.0g of deionized water, and add 18.0g of magnesium chloride hexahydrate, 13.0g of anhydrous potassium chloride, 5.5g of potassium citrate monohydrate and 7.0g of urea in sequence, stirring until the solids are completely dissolved and evenly dispersed to obtain a magnesium potassium salt solution; slowly add the magnesium potassium salt solution to the silicate solution, keeping the system continuously stirred during the addition process, controlling the system to prevent the formation of obvious large gel blocks, after the addition is complete, adjust the pH to 10.0 with hydrochloric acid aqueous solution, add 2.5g of polyethylene glycol 400, and continue stirring until the system is in a uniform milky white suspension state to obtain an interlayer confined suspension;

[0040] B2. The interlayer confinement suspension was transferred into a hydrothermal reactor, with the liquid volume being 70% of the effective volume of the hydrothermal reactor. After sealing, the mixture was hydrothermally reacted at 155°C for 10 hours. After the reaction was completed, it was naturally cooled to 25°C for solid-liquid separation. The obtained solid was washed with deionized water until the conductivity of the washing liquid was no higher than 50 μS / cm. Then, it was dried in a 97.5°C forced-air drying environment for 10 hours. Subsequently, it was calcined at 500°C for 2.5 hours. After calcination, it was cooled to 25°C, pulverized, and sieved to obtain the silicon-magnesium-potassium interlayer confinement pore-forming agent.

[0041] Example 2

[0042] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing bamboo-based porous carbon, the steps of which include:

[0043] S1. Add 220.0g deionized water, 15.0g anhydrous ethanol, 18.0g 85% phosphoric acid aqueous solution, 8.0g urea, 2.0g boric acid, 3.0g glucose monohydrate, 0.5g polyvinylpyrrolidone and 5.0g nitrogen-phosphorus-boron gradient complexing activated salt to a stirring container and mix at 45°C for 1 hour to disperse the components evenly and obtain the pre-impregnation solution.

[0044] S2. Wash 100.0g of bamboo chips with deionized water until there is no obvious floating dust and impurities on the surface, and dry to constant weight to obtain pretreated bamboo chips; crush the pretreated bamboo chips to obtain bamboo powder; add the bamboo powder to the pre-impregnation liquid to completely wet the bamboo powder, vacuum impregnate for 1 hour, and then stir and impregnate for 2 hours to obtain impregnated bamboo powder; transfer the impregnated bamboo powder to a hydrothermal reaction device and hydrothermally treat at 160°C for 4 hours. After the reaction is completed, cool, filter and collect the solid, and dry to constant weight to obtain pre-complexed bamboo-based precursor.

[0045] S3. Mix the pre-complexed bamboo-based precursor, 65.0g of flake potassium hydroxide, 8.0g of anhydrous potassium carbonate, and 3.0g of potassium magnesium silicate interlayer confinement pore-forming agent to ensure uniform adhesion of the flake potassium hydroxide, anhydrous potassium carbonate, and potassium magnesium silicate interlayer confinement pore-forming agent to the surface of the pre-complexed bamboo-based precursor, thus obtaining an activated mixture. Under nitrogen protection, pre-carbonize the activated mixture at 430°C for 0.5h, and then carbonize it at 780°C for 1.0h to obtain a carbonized activated material. Activate the carbonized activated material with carbon dioxide gas at 820°C for 20min. Cool to room temperature and wash successively with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water until the washing solution is nearly neutral. Dry to constant weight and then stabilize at 850°C for 0.5h to obtain bamboo-based porous carbon.

[0046] Preparation steps of nitrogen-phosphorus-boron gradient complexing activated salt:

[0047] A1. Add 100.0g deionized water, 12.0g citric acid monohydrate, 25.0g urea, 20.0g ammonium dihydrogen phosphate, 6.0g boric acid and 3.0g sodium gluconate monohydrate to a reaction vessel and stir at 55°C for 20min to fully dissolve the components and form a homogeneous mixture. Add 10.0g anhydrous potassium carbonate to the mixture, stir and adjust the pH to 6.2, then continue stirring at 75°C for 1.5h. Concentrate under reduced pressure until the system is in a homogeneous viscous state to obtain a concentrated nitrogen-phosphorus-boron complex salt solution.

[0048] A2. Add 80.0g of anhydrous ethanol to the concentrated NPK compound salt solution, mix well, and let stand at 4°C for 6h to allow the compound salt components to separate. Filter and collect the solid, dry the obtained solid at 70°C for 6h, and then place it in a nitrogen-protected environment for solid-phase complexation and shaping at 110°C for 2h. Cool to room temperature, pulverize, and sieve to obtain NPK graded complex activated salt.

[0049] Preparation steps of silicon-magnesium-potassium interlayer confinement pore-forming agent:

[0050] B1. Add 50.0g of deionized water and 18.0g of sodium metasilicate pentahydrate to a reaction vessel and stir at 40°C for 30 min to obtain a silicate solution. Separately, mix 50.0g of deionized water, 12.0g of magnesium chloride hexahydrate, 8.0g of anhydrous potassium chloride, 3.0g of potassium citrate monohydrate, and 4.0g of urea, and stir until the solid dissolves and is evenly dispersed to obtain a magnesium potassium salt solution. Add the magnesium potassium salt solution to the silicate solution, keeping the system stirred evenly during the addition process. Adjust the pH to 9.5, add 1.0g of polyethylene glycol 400, and continue stirring until the system is in a uniform suspension state to obtain an interlayer confined suspension.

[0051] B2. The interlayer confinement suspension was transferred into a hydrothermal reactor and hydrothermally reacted at 140°C for 8 hours. After the reaction was completed, it was cooled to room temperature and solid-liquid separation was performed. The obtained solid was washed until the washing liquid was clear, then dried at 90°C for 8 hours, followed by calcination at 450°C for 2 hours, cooled, and pulverized to obtain the silicon-magnesium-potassium interlayer confinement pore-forming agent.

[0052] Example 3

[0053] The difference between this embodiment and Embodiment 1 is that this embodiment provides a method for preparing bamboo-based porous carbon, the steps of which include:

[0054] S1. Add 360.0g deionized water, 45.0g anhydrous ethanol, 42.0g 85% phosphoric acid aqueous solution, 24.0g urea, 8.0g boric acid, 12.0g glucose monohydrate, 2.5g polyvinylpyrrolidone and 14.0g nitrogen-phosphorus-boron gradient complexing activated salt to a stirring container and mix at 60°C for 3 hours to disperse the components evenly and obtain a pre-impregnation solution.

[0055] S2. Wash 120.0g of bamboo chips with deionized water until there is no obvious floating dust and impurities on the surface, and dry to constant weight to obtain pretreated bamboo chips; crush the pretreated bamboo chips to obtain bamboo powder; add the bamboo powder to the pre-impregnation liquid to completely wet the bamboo powder, vacuum impregnate for 3h, and then stir and impregnate for 4h to obtain impregnated bamboo powder; transfer the impregnated bamboo powder to a hydrothermal reaction device and hydrothermally treat at 190°C for 8h. After the reaction is completed, cool, filter and collect the solid, and dry to constant weight to obtain pre-complexed bamboo-based precursor.

[0056] S3. Mix the pre-complexed bamboo-based precursor, 135.0g of flake potassium hydroxide, 26.0g of anhydrous potassium carbonate, and 10.0g of potassium magnesium silicate interlayer confinement pore-forming agent to ensure uniform adhesion of the flake potassium hydroxide, anhydrous potassium carbonate, and potassium magnesium silicate interlayer confinement pore-forming agent to the surface of the pre-complexed bamboo-based precursor, thus obtaining an activated mixture. Under nitrogen protection, pre-carbonize the activated mixture at 480°C for 1.5h, and then carbonize it at 860°C for 2.5h to obtain a carbonized activated material. Activate the carbonized activated material with carbon dioxide gas at 880°C for 70min. Cool to room temperature and wash successively with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water until the washing solution is nearly neutral. Dry to constant weight and then stabilize at 950°C for 1.5h to obtain bamboo-based porous carbon.

[0057] Preparation steps of nitrogen-phosphorus-boron gradient complexing activated salt:

[0058] A1. Add 130.0g deionized water, 20.0g citric acid monohydrate, 40.0g urea, 35.0g ammonium dihydrogen phosphate, 14.0g boric acid and 8.0g sodium gluconate monohydrate to a reaction vessel and stir at 65°C for 40min to fully dissolve the components and form a homogeneous mixture. Add 22.0g anhydrous potassium carbonate to the mixture, stir and adjust the pH to 6.8, then continue stirring at 85°C for 3.0h. Concentrate under reduced pressure until the system is in a homogeneous viscous state to obtain a concentrated nitrogen-phosphorus-boron complex salt solution.

[0059] A2. Add 160.0g of anhydrous ethanol to the concentrated NPK compound salt solution, mix well, and let stand at 8°C for 12h to allow the compound salt components to separate. Filter and collect the solid, dry the obtained solid at 80°C for 10h, and then place it in a nitrogen-protected environment for solid-phase complexation and shaping at 125°C for 4h. Cool to room temperature, pulverize, and sieve to obtain NPK graded complex activated salt.

[0060] Preparation steps of silicon-magnesium-potassium interlayer confinement pore-forming agent:

[0061] B1. Add 70.0g of deionized water and 32.0g of sodium metasilicate pentahydrate to a reaction vessel and stir at 50°C for 50 min to obtain a silicate solution. Separately, mix 70.0g of deionized water, 24.0g of magnesium chloride hexahydrate, 18.0g of anhydrous potassium chloride, 8.0g of potassium citrate monohydrate, and 10.0g of urea, and stir until the solid dissolves and is evenly dispersed to obtain a magnesium potassium salt solution. Add the magnesium potassium salt solution to the silicate solution, keeping the system stirred evenly during the addition process. Adjust the pH to 10.5, add 4.0g of polyethylene glycol 400, and continue stirring until the system is in a uniform suspension state to obtain an interlayer confined suspension.

[0062] B2. The interlayer confinement suspension was transferred into a hydrothermal reaction apparatus and hydrothermally reacted at 170°C for 12 hours. After the reaction was completed, it was cooled to room temperature and solid-liquid separation was performed. The obtained solid was washed until the washing liquid was clear, and then dried at 105°C for 12 hours. Subsequently, it was calcined at 550°C for 3 hours, cooled, and pulverized to obtain the silicon magnesium potassium interlayer confinement pore-forming agent.

[0063] Comparative Example 1

[0064] The difference between this comparative example and Example 1 is that 9.5g of nitrogen-phosphorus-boron gradient complexing activating salt is not added in step S1, while 6.5g of silicon-magnesium-potassium interlayer confinement pore-forming agent is still added in step S3. The rest is the same as in Example 1.

[0065] Comparative Example 2

[0066] The difference between this comparative example and Example 1 is that 6.5g of silicon-magnesium-potassium interlayer confinement pore-forming agent is not added in step S3, while 9.5g of nitrogen-phosphorus-boron gradient complexing activating salt is still added in step S1. The rest is the same as in Example 1.

[0067] Comparative Example 3

[0068] The difference between this comparative example and Example 1 is that 9.5g of nitrogen-phosphorus-boron gradient complexing activating salt is not added in step S1, and 6.5g of silicon-magnesium-potassium interlayer confinement pore-forming agent is not added in step S3. The rest is the same as Example 1.

[0069] The performance of the bamboo-based porous carbon provided in the above embodiments and comparative examples was tested using the following methods:

[0070] Bamboo-based porous carbon samples prepared in Examples 1-3 and Comparative Examples 1-3 were placed in a 105°C forced-air drying oven for 6 hours, then removed and placed in a desiccator to cool to 25°C and sealed for storage.

[0071] For specific surface area testing, 0.2000 g of sample was weighed and placed into an adsorption test sample tube. The sample was degassed at 200°C under vacuum for 6 hours. After degassed, the sample was cooled to 25°C and weighed. Subsequently, nitrogen adsorption testing was performed at 77 K. Adsorption data were collected within the relative pressure range of 0.05-0.30. The specific surface area was calculated using a multi-point method. Each sample was tested in triplicate, and the average value was taken. The result is expressed in m³. 2 / g.

[0072] For the total pore volume test, the same nitrogen adsorption test data was used to read the nitrogen adsorption amount at a relative pressure of 0.995. The adsorption amount was converted into liquid nitrogen volume and normalized according to the mass of the sample after degassing to obtain the total pore volume. Each sample was tested in triplicate, and the average value was taken. The result is in cm. 3 / g.

[0073] During the mesopore ratio test, the pore size distribution was calculated based on the nitrogen adsorption-desorption curve. The pore volume in the pore size range of 2-50 nm was counted as the mesopore volume, and the proportion of the mesopore volume to the total pore volume was used as the mesopore ratio. Each sample was tested in parallel 3 times, and the average value was taken. The result is in units of .

[0074] During the total heteroatom content test, the dried bamboo-based porous carbon sample was pressed into a flat sample sheet. At least three test areas were selected on the sample surface to determine the content of nitrogen, phosphorus and boron elements respectively. The atomic percentages of the three elements were added together to obtain the total heteroatom content. The average value of the three test areas for each sample was taken, and the result was expressed in at.

[0075] For ash content testing, 1.0000g of dried sample was weighed and placed in a pre-weighed crucible. The sample was heated to 800°C in air and kept at that temperature for 2 hours. Then it was cooled to 25°C and the mass of the residue was weighed. The ash content was calculated as the ratio of the mass of the residue to the mass of the initial sample. Each sample was tested in parallel 3 times and the average value was taken. The result is in units of .

[0076] For the specific capacitance test, bamboo-based porous carbon, acetylene black, and polyvinylidene fluoride were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone was added to grind into a uniform slurry. The slurry was coated onto the surface of a nickel foam current collector, vacuum dried at 80°C for 12 hours, and then pressed into a sheet to obtain the working electrode. A platinum sheet was used as the counter electrode, a saturated calomel electrode as the reference electrode, and a 6 mol / L potassium hydroxide aqueous solution as the electrolyte. A constant current charge-discharge test was performed at a current density of 1 A / g. The specific capacitance was calculated based on the discharge time, current, and mass of the active material. Three electrodes were prepared for each sample and tested separately. The average value was taken, and the result was expressed in F / g.

[0077] The performance test data above are shown in Table 1.

[0078] Table 1: Performance Test Results

[0079]

[0080] As can be seen from the above, Examples 1-3 show significant advantages over Comparative Examples 1-3 in terms of specific surface area, total pore volume, mesopore ratio, total heteroatom content, ash control, and specific capacitance. This indicates that the present invention solves the problems of uneven activator distribution, insufficient pore structure control, low heteroatom doping efficiency, carbon skeleton collapse caused by local over-etching, and high inorganic residue in the preparation of bamboo-based porous carbon by means of the synergistic effect of nitrogen-phosphorus-boron gradient complexation activating salt and silicon-magnesium-potassium interlayer confinement pore-forming agent.

[0081] Specifically, the specific surface area of ​​Examples 1-3 was 2520-2865 m² / g, which was significantly higher than that of Comparative Example 1 (2146 m² / g). 2 / g, 1988m of Comparative Example 2 2 / g and 1715m of Comparative Example 3 2 / g indicates that after the simultaneous addition of nitrogen-phosphorus-boron gradient complexing activating salt and silicon-magnesium-potassium interlayer confining pore-forming agent, the activation effect of flake potassium hydroxide and anhydrous potassium carbonate can be carried out more uniformly in the bamboo-based precursor, forming a more developed pore structure.

[0082] The total pore volume of Examples 1-3 is 1.34-1.62 cm³. 3 / g, higher than the 0.86-1.18cm of comparative examples 1-3. 3 / g indicates that the nitrogen-phosphorus-boron gradient complexing activated salt improves the dispersion of activated components and heteroatom components in the bamboo powder pores, while the silicon-magnesium-potassium interlayer confining pore-forming agent reduces the local enrichment of strong bases through spatial confinement, making the pore formation more complete.

[0083] The mesopore content of Examples 1-3 ranged from 39.6% to 45.3%, with Example 3 reaching 45.3%, which was significantly higher than the 24.7% of Comparative Example 2 without the addition of the silicon-magnesium-potassium interlayer confinement pore-forming agent and the 21.3% of Comparative Example 3 without the addition of both nitrogen-phosphorus-boron gradient complexing activating salt and silicon-magnesium-potassium interlayer confinement pore-forming agent. This indicates that the silicon-magnesium-potassium interlayer confinement pore-forming agent can effectively induce the formation of mesopores and interconnected pores, and improve the problem that simple alkali salt activation tends to favor micropores and has insufficient mesopores.

[0084] The total heteroatom content of Examples 1-3 was 5.86-6.35 at%, which was significantly higher than that of Comparative Example 1 (3.21 at%) and Comparative Example 3 (2.74 at%) without the addition of nitrogen-phosphorus-boron gradient complexing activated salt. This indicates that the nitrogen-phosphorus-boron gradient complexing activated salt can introduce nitrogen, phosphorus, and boron components into the bamboo-based precursor in a pre-complexed state, thereby improving the uniformity and retention rate of heteroatom doping.

[0085] The ash content of Examples 1-3 was 1.18-1.46%, which was lower than that of Comparative Example 2 (2.74%) and Comparative Example 3 (2.96%). This indicates that the combination of nitrogen-phosphorus-boron gradient complexing activated salt and silicon-magnesium-potassium interlayer confinement pore-forming agent with acid and alkali washing helps to reduce inorganic template and potassium salt residue, thus improving the problem of high ash content in existing processes.

[0086] The specific capacitance of Examples 1-3 was 276-312 F / g, which was significantly higher than that of Comparative Example 1 (226 F / g), Comparative Example 2 (218 F / g), and Comparative Example 3 (176 F / g). This indicates that the bamboo-based porous carbon obtained in this invention has a high specific surface area, large pore volume, reasonable mesopore ratio, and high heteroatom content, which can provide more available active sites and smoother ion transport channels, thereby improving electrochemical energy storage performance.

[0087] Comparative Example 1 lacked the nitrogen-phosphorus-boron gradient complexing activation salt, resulting in a significant decrease in the total heteroatom content and specific capacitance. Comparative Example 2 lacked the silicon-magnesium-potassium interlayer confinement pore-forming agent, leading to a significant deterioration in the mesopore ratio, total pore volume, and ash content control. Comparative Example 3 lacked both modified compounds, resulting in the lowest performance levels across all categories. This further demonstrates that the nitrogen-phosphorus-boron gradient complexing activation salt and the silicon-magnesium-potassium interlayer confinement pore-forming agent are not simply additive, but rather work synergistically in heteroatom introduction, pore structure regulation, framework protection, and residue removal. This effectively solves the existing technical problems of uneven carbon pore structure, insufficient mesopores, low doping efficiency, and unstable overall performance in bamboo-based porous materials.

Claims

1. A method for preparing bamboo-based porous carbon, characterized in that the steps include... include: S1. By weight, mix 220.0-360.0 parts deionized water, 15.0-45.0 parts anhydrous ethanol, 18.0-42.0 parts orthophosphoric acid aqueous solution, 8.0-24.0 parts urea, 2.0-8.0 parts boric acid, 3.0-12.0 parts glucose monohydrate, 0.5-2.5 parts polyvinylpyrrolidone and 5.0-14.0 parts nitrogen-phosphorus-boron gradient complexing activated salt to obtain a pre-impregnation solution; S2. Clean and dry the surface of 100.0-120.0 parts of bamboo strips to obtain pretreated bamboo strips; Pretreated bamboo chips are crushed to obtain bamboo powder; the bamboo powder is added to a pre-impregnation solution for vacuum impregnation and stirring impregnation to obtain impregnated bamboo powder; the impregnated bamboo powder is subjected to hydrothermal treatment, filtered, and dried to obtain a pre-complexed bamboo-based precursor. S3. Mix the pre-complexed bamboo-based precursor, 65.0-135.0 parts of flake potassium hydroxide, 8.0-26.0 parts of anhydrous potassium carbonate, and 3.0-10.0 parts of potassium magnesium silicate interlayer confinement pore-forming agent to obtain an activated mixture; under nitrogen protection, pre-carbonize and high-temperature carbonize the activated mixture to obtain a carbonized activated material; activate the carbonized activated material with carbon dioxide gas, cool it, and wash it sequentially with hydrochloric acid aqueous solution, deionized water, sodium hydroxide aqueous solution, and deionized water, then dry and stabilize it.

2. The method for preparing bamboo-based porous carbon according to claim 1, characterized in that, In step S1, the mass fraction of the orthophosphoric acid aqueous solution is 85%; the polyvinylpyrrolidone is polyvinylpyrrolidone K30; the mixing temperature is 45-60℃, and the mixing time is 1-3h.

3. The method for preparing bamboo-based porous carbon according to claim 1, characterized in that, In step S2, the vacuum impregnation time is 1-3 hours; the stirring impregnation time is 2-4 hours; the hydrothermal treatment temperature is 160-190℃, and the hydrothermal treatment time is 4-8 hours.

4. The method for preparing bamboo-based porous carbon according to claim 1, characterized in that, In step S3, the pre-carbonization temperature is 430-480℃, and the pre-carbonization time is 0.5-1.5h; the high-temperature carbonization temperature is 780-860℃, and the high-temperature carbonization time is 1.0-2.5h; the activation temperature is 820-880℃, and the activation time is 20-70min; the stabilization treatment temperature is 850-950℃, and the stabilization treatment time is 0.5-1.5h.

5. The method for preparing bamboo-based porous carbon according to claim 1, characterized in that, The preparation method of the nitrogen-phosphorus-boron gradient complexing activated salt includes: A1. By weight, mix 100.0-130.0 parts deionized water, 12.0-20.0 parts citric acid monohydrate, 25.0-40.0 parts urea, 20.0-35.0 parts ammonium dihydrogen phosphate, 6.0-14.0 parts boric acid and 3.0-8.0 parts sodium gluconate monohydrate, stir at 55-65℃, add 10.0-22.0 parts anhydrous potassium carbonate, adjust the pH to 6.2-6.8, continue stirring, concentrate under reduced pressure to obtain a concentrated nitrogen-phosphorus-boron complex salt solution; A2. Add 80.0-160.0 parts of anhydrous ethanol to the nitrogen-phosphorus-boron complex salt concentrate, let stand, filter, dry, carry out solid-phase complexation and shaping under nitrogen protection, cool, pulverize, and sieve.

6. The method for preparing bamboo-based porous carbon according to claim 5, characterized in that, In step A1, the stirring time is 20-40 minutes at 55-65℃; the stirring temperature is 75-85℃ and the stirring time is 1.5-3.0 hours.

7. The method for preparing bamboo-based porous carbon according to claim 5, characterized in that, In step A2, the standing temperature is 4-8℃ and the standing time is 6-12h; the drying temperature is 70-80℃ and the drying time is 6-10h; the solid phase complexation and shaping temperature is 110-125℃ and the solid phase complexation and shaping time is 2-4h.

8. The method for preparing bamboo-based porous carbon according to claim 1, characterized in that, The preparation method of the silicon-magnesium-potassium interlayer confinement pore-forming agent includes: B1. By weight, mix 50.0-70.0 parts of deionized water and 18.0-32.0 parts of sodium metasilicate pentahydrate, and stir at 40-50℃ to obtain a silicate solution; mix 50.0-70.0 parts of deionized water, 12.0-24.0 parts of magnesium chloride hexahydrate, 8.0-18.0 parts of anhydrous potassium chloride, 3.0-8.0 parts of potassium citrate monohydrate, and 4.0-10.0 parts of urea to obtain a magnesium potassium salt solution; add the magnesium potassium salt solution to the silicate solution, adjust the pH to 9.5-10.5, add 1.0-4.0 parts of polyethylene glycol 400, and continue stirring to obtain an interlayer confined suspension; B2. The interlayer confined suspension is subjected to hydrothermal reaction, cooling, solid-liquid separation, washing, drying, calcination, and pulverization.

9. The method for preparing bamboo-based porous carbon according to claim 8, characterized in that, In step B1, the stirring time at 40-50℃ is 30-50 minutes.

10. The method for preparing bamboo-based porous carbon according to claim 8, characterized in that, In step B2, the hydrothermal reaction temperature is 140-170℃ and the hydrothermal reaction time is 8-12h; the drying temperature is 90-105℃ and the drying time is 8-12h; the calcination temperature is 450-550℃ and the calcination time is 2-3h.

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