Method for preparing porous carbon and silicon powder from silicon-rich biomass

Abstract

The invention discloses a method for preparing porous carbon and silicon powder from silicon-rich biomass. Silicon-rich biomasses such as rice husks, straws, bagasse and coconut shells are used as raw materials, and a silicon dioxide component is dissolved out by activating potassium hydroxide in calcium chloride-sodium chloride-calcium oxide molten salt, so that a porous carbon material is obtained; and reducing silicon oxide in the molten salt by an electrochemical method, depositing on a cathode to form silicon powder, and simultaneously purifying and recycling the molten salt leachate. The silicon-rich biomass is used as a raw material, potassium hydroxide is used as an activation dissolution enhancer, recyclable calcium chloride-sodium chloride-calcium oxide fused salt is used as a dissolution separation liquid, the operation temperature is 600-900 DEG C, and the silicon-rich biomass is controllably converted into the silicon powder and the porous carbon functional material in a constant-voltage / constant-current electro-deposition-purification mode. Separation of silicon and carbon components in the silicon-rich biomass and direct preparation, regulation and control of the high-value silicon powder and the porous carbon are achieved, the technological process is simple, and industrial production can be achieved easily.

Description

Technical Field

[0001] The present application belongs to the field of value-added utilization of biomass solid waste, and relates to a method for preparing porous carbon and silicon powder using silicon-rich biomass. Background Art

[0002] The efficient development and utilization of biomass can give full play to the comprehensive benefits of reducing pollution and carbon emissions and ensuring energy security. Silicon-rich biomass (such as rice husks, straw, bagasse, coconut shells, etc.) is a combination of organic carbon and silicon dioxide. However, the current development and utilization of silicon-rich biomass is mostly focused on the separation and extraction of silicon dioxide or carbon components. The product value is low and involves a multi-step processing process, resulting in low utilization and high development costs.

[0003] For example, patent CN112675814B discloses a preparation method and application of a silicon-rich biomass-based biochar / mesoporous silica composite material. The preparation method uses waste silicon-rich biomass as raw material, first pyrolyzes it to obtain pyrolytic carbon, and then extracts the silicon element therefrom by alkali fusion (dissolution); after washing and separation, silicon-free biochar and silicon-rich liquid are obtained respectively; the obtained silicon-free biochar is used as the carbon source and the silicon-rich liquid is used as the silicon source, and the biochar / mesoporous silica composite material is prepared by an in-situ reconstruction process. Patent CN115465864A discloses a nano-silicon material prepared by a low-temperature molten salt thermal method, and its preparation method and application. The biomass material is heated in a water bath with a hydrochloric acid solution, and then filtered and dried; the dried biomass is calcined, and bio-based silica is obtained after cooling; the obtained bio-based silica is fully ground with a reducing agent and a metal salt under a protective atmosphere, and then the mixture is transferred to a closed container for a molten salt thermal reaction; after the reaction is completed, the product is soaked in hydrochloric acid and hydrofluoric acid in turn, washed and vacuum dried to obtain the product.

[0004] In summary, existing technologies have many defects in the utilization of silicon-rich biomass. On the one hand, most of the current development and utilization methods focus only on the separation and extraction of silicon dioxide or carbon components, and the product value is low, making it difficult to fully utilize the potential advantages of silicon-rich biomass. On the other hand, the multi-step processing process not only leads to low resource utilization, but also greatly increases the development cost, limiting the economic benefits of related industries.

[0005] In this context, it is of great significance to carry out research on silicon-rich biomass. Porous carbon materials and silicon materials have broad prospects in the fields of electronic equipment, energy storage technology, environmental engineering, etc. If these two materials can be efficiently prepared from silicon-rich biomass, it will greatly promote the development of my country's resource efficient utilization industry. This will not only help improve resource utilization efficiency and reduce costs, but also create higher economic value and meet the needs of multiple fields for high-performance materials. Therefore, in-depth research on silicon-rich biomass is urgently needed. Summary of the invention

[0006] Based on the above shortcomings in the prior art, the purpose of the present application is to provide a method for preparing porous carbon and silicon powder using silicon-rich biomass.

[0007] The present invention directly uses silicon-rich biomass as raw material, activates and dissolves silicon dioxide components in silicon-rich biomass in calcium chloride-sodium chloride-calcium oxide molten salt by potassium hydroxide, thereby obtaining porous carbon materials; then, the silicon oxide in the molten salt is electrochemically reduced by an electrochemical method, and the elemental silicon deposited and formed at the cathode and the purification of the molten salt are simultaneously realized; the microstructure of carbon can be regulated by the amount of potassium hydroxide added, the ratio of calcium chloride-sodium chloride-calcium oxide molten salt, and the activation dissolution temperature and time; silicon powder can be controllably extracted by electrochemical parameters. Finally, the purpose of directly using silicon-rich biomass to prepare porous carbon and silicon materials is achieved.

[0008] One of the technical solutions of the present invention provides a method for preparing porous carbon and silicon powder using silicon-rich biomass, the method comprising the following steps:

[0009] a. The silicon-rich biomass or the ash after pyrolysis of the silicon-rich biomass is washed, then dried and crushed to obtain a silicon-rich biomass powder;

[0010] b. The silicon-rich biomass powder obtained in step a is mixed with potassium hydroxide and then a solvent is added to prepare a silicon-rich biomass-potassium hydroxide slurry;

[0011] c. drying and grinding the silicon-rich biomass-potassium hydroxide slurry obtained in step b to obtain a silicon-rich biomass-potassium hydroxide powder;

[0012] d. In an inert gas atmosphere, the silicon-rich biomass-potassium hydroxide powder obtained in step c is activated and dissolved in a calcium chloride-sodium chloride-calcium oxide molten salt to obtain a silicon-rich biomass activation dissolution product;

[0013] e. The activated dissolution product of the silicon-rich biomass obtained in step d is then placed in a calcium chloride-sodium chloride-calcium oxide molten salt for activation and dissolution, and the treatment is performed multiple times; after the treatment is completed, a solid phase product and a calcium chloride-sodium chloride-calcium oxide-silicon oxide molten salt dissolution solution are obtained by filtration and screening;

[0014] f. washing and drying the solid phase product obtained in step e to obtain a porous carbon material;

[0015] g. In an inert gas atmosphere, the calcium chloride - sodium chloride - calcium oxide - silicon oxide molten salt solution obtained in step e is used as an electrolyte, kept warm, and electrodeposited with graphite or zinc as a cathode and graphite as an anode to obtain a cathode having a silicon product deposited thereon;

[0016] h. The cathode with the silicon product deposited thereon prepared in step g is taken out from the reaction vessel, and after cleaning and drying, silicon powder is finally obtained.

[0017] Furthermore, the silicon-rich biomass raw material in step a includes one or more of rice husks, rice stalks, straw, reeds, bagasse or coconut shells; the ash after pyrolysis of the silicon-rich biomass is one or more of the ash obtained after pyrolysis of rice husks, rice stalks, straw, reeds, bagasse or coconut shells; the cleaning refers to cleaning with deionized water and anhydrous ethanol to remove dust; the drying temperature is 50-90°C and the time is 2-6 hours.

[0018] Furthermore, in step b, the mass ratio of the silicon-rich biomass powder to potassium hydroxide is 1:(0-1), wherein the mass of potassium hydroxide is not 0; and the solvent in the silicon-rich biomass-potassium hydroxide slurry is deionized water.

[0019] Furthermore, the drying temperature in step c is 50-90° C. and the drying time is 2-6 hours.

[0020] Furthermore, in the calcium chloride-sodium chloride-calcium oxide molten salt described in step d, the mass fraction ratio of calcium chloride: sodium chloride: calcium oxide is: (0-100wt%): (0-50wt%): (0-10wt%), wherein the mass fractions of the three are not 0; the inert gas is preferably argon or nitrogen; the mass ratio between the silicon-rich biomass-potassium hydroxide powder and the calcium chloride-sodium chloride-calcium oxide molten salt is (0-2): 5, wherein the mass of the silicon-rich biomass-potassium hydroxide powder is not 0; the activation dissolution time is 0-12 hours, and the temperature is 600-900°C.

[0021] Furthermore, the purpose of the multiple treatments in step e is to achieve activated pore formation and controlled dissolution of silica; the number of multiple treatments is preferably 0 to 5 times; the filter screen used for the filtering and screening in step e is any one of an alumina ceramic screen, a quartz screen or a graphite screen.

[0022] Furthermore, the washing in step f refers to washing with dilute hydrochloric acid and deionized water; the drying temperature is 50 to 90° C. and the drying time is 2 to 6 hours.

[0023] Furthermore, the silicon product in step g is deposited on the cathode, and this step can simultaneously achieve the purification of the electrodeposited silicon and the molten salt; the graphite is a solid cathode and the zinc is a liquid cathode.

[0024] Furthermore, the inert gas in step g is preferably argon or nitrogen; the insulation temperature is 600-900°C; the electrodeposition conditions are 1.5-3.0 volts or 10-50 mA / cm2; the purified molten salt obtained in step g is continuously used in step d to achieve the recycling of the molten salt.

[0025] Furthermore, the cleaning in step h is: cleaning with dilute hydrochloric acid and deionized water in sequence; the drying temperature is 50-90° C. and the time is 2-6 hours.

[0026] Furthermore, in this method, the microstructure of carbon can be regulated by the amount of potassium hydroxide added, the ratio of calcium chloride-sodium chloride-calcium oxide molten salt, and the activation dissolution temperature and time; the micromorphology of silicon can be regulated by electrochemical parameters.

[0027] A second technical solution of the present invention provides a porous carbon obtained by the above-mentioned method of preparing porous carbon and silicon powder using silicon-rich biomass.

[0028] A third technical solution of the present invention provides a silicon powder obtained by the above-mentioned method of preparing porous carbon and silicon powder using silicon-rich biomass.

[0029] In summary, the present invention proposes a new method for preparing porous carbon and silicon powder using silicon-rich biomass. This technical route has the characteristics of short process, low cost, and controllable morphology and structure of carbon and silicon products.

[0030] Compared with the prior art, the present invention has the following technical effects and improvements:

[0031] (1) The present invention aims to prepare porous carbon and silicon powder using silicon-rich biomass, which has significant raw material advantages. Silicon-rich biomass or its ash has a wide range of sources, such as crop straw, forestry waste, etc., and making full use of it not only avoids waste of resources but also reduces costs. At the same time, the carbon and silicon resources in the biomass are comprehensively transformed, which greatly improves the efficiency of resource utilization and conforms to the concept of sustainable development.

[0032] (2) The overall process of the method provided by the present invention covers a variety of conventional operations, the process is simple, and it is conducive to industrialization. Activation dissolution in calcium chloride-sodium chloride-calcium oxide molten salt can effectively treat silicon-rich biomass, form a porous structure and promote silicon dissolution. The activated dissolution product of silicon-rich biomass is treated multiple times to ensure the purity of the product. The electrodeposition method is used to prepare silicon products from molten salt dissolution solution, which has high selectivity and efficiency and can obtain high-purity silicon powder.

[0033] (3) The porous carbon material prepared by the present invention has abundant pores and a large specific surface area, and has great application potential in the fields of adsorption and catalysis. The obtained silicon powder has high purity, can meet the needs of industries such as electronics and photovoltaics that have strict requirements on silicon purity, and has high application value.

[0034] (4) The method provided by the present invention is environmentally friendly. It uses renewable silicon-rich biomass as raw material, which reduces environmental pollution and dependence on non-renewable resources compared to traditional fossil fuel raw materials. In the preparation process, inert gas atmosphere and other means are used to reduce harmful gas emissions, showing good environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 . Schematic diagram of the process of preparing porous carbon and silicon materials using silicon-rich biomass in the present invention;

[0036] Figure 2 The microscopic morphology (left) and X-ray diffraction pattern (right) of the porous carbon prepared in Example 1 of the present invention;

[0037] Figure 3 . X-ray diffraction pattern of silicon powder prepared in Example 1 of the present invention;

[0038] Figure 4 . The microscopic morphology of silicon powder prepared in Example 1 of the present invention;

[0039] Figure 5 . The specific surface area of ​​the porous carbon prepared in Example 2 of the present invention;

[0040] Figure 6 The microscopic morphology (left) and energy spectrum component analysis diagram (right) of the porous carbon prepared in Example 2 of the present invention;

[0041] Figure 7 . X-ray diffraction pattern of silicon powder prepared in Example 2 of the present invention;

[0042] Figure 8 .Microscopic morphology of silicon powder prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with specific embodiments. It should be noted that the following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0044] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0045] Example 1

[0046] a. Take the reeds, clean them, dry them at 80℃ for 3h, and crush them to obtain reed powder;

[0047] b. Weigh 9 grams of reed, mix with 1 gram of potassium hydroxide, add to 100mL of deionized water, stir evenly to obtain a reed - potassium hydroxide slurry;

[0048] c. The reed-potassium hydroxide slurry was dried at 80°C and then ground to obtain a 5-purpose reed-potassium hydroxide powder;

[0049] d. The above-mentioned 10 grams of reed-potassium hydroxide powder and 150 grams of calcium chloride (90%)-sodium chloride (8%)-calcium oxide (2%) molten salt are placed in an alumina crucible, and the crucible temperature is raised to 850° C. by a high-temperature resistance furnace and kept warm for 4 hours under the protection of high-purity nitrogen. During this process, the reed will be directly activated-pyrolyzed, and the silicon dioxide therein will be dissolved; this step finally obtains a solid phase product and a calcium chloride (90%)-sodium chloride (8%)-calcium oxide (2%)-silicon oxide dissolution solution;

[0050] e. Calcium chloride (90%) - sodium chloride (8%) - calcium oxide (2%) - silicon oxide and solid phase product separated by filtration using a 10-mesh corundum sieve;

[0051] f. The solid phase product is washed with dilute hydrochloric acid and deionized water in turn, and then dried at 70°C for 4 hours, and then ground to obtain porous carbon; the obtained porous carbon can be used as a supercapacitor electrode material, a lithium-ion battery negative electrode, etc.;

[0052] g. The obtained calcium chloride (90%) - sodium chloride (8%) - calcium oxide (2%) - silicon oxide solution was then used as an electrolyte and kept at 850°C in high-purity nitrogen; two graphite sheets were placed in the above electrolyte as an anode and a cathode, respectively, and then electrodeposited at a constant current density of 10 mA / cm2 for 1 hour;

[0053] h. After the electrodeposition is completed, the electrodeposition product attached to the cathode is washed with dilute hydrochloric acid and deionized water in turn, and dried to obtain silicon powder; the calcium chloride (90%)-sodium chloride (8%)-calcium oxide (2%) molten salt purified after the electrodeposition in this step can be added to step d for recycling.

[0054] The flow chart of preparing porous carbon and silicon powder using reeds in this embodiment is as follows Figure 1 The microstructure and X-ray diffraction pattern of porous carbon are shown in Figure 2 As shown, it has typical amorphous carbon characteristics, and the graphite (002) crystal plane diffraction peak 2θ is located at about 26°. Figure 3 This is the X-ray diffraction diagram of the electrodeposited silicon powder. Crystalline silicon has obvious diffraction peaks at positions 2θ of approximately 28.4°, 47.3°, and 56.1°, which correspond to the diffraction of crystal planes such as (111), (220), and (311), respectively. Figure 4The microscopic morphology of the electrodeposited silicon powder shows a typical nanowire morphology with a relatively uniform diameter. These nanowires have good crystallinity, which is conducive to the transmission of electrons in the nanowires, and is crucial for their application in electronic devices and other fields. The above results fully prove that the method proposed by the present invention can effectively use reeds to prepare silicon porous carbon and silicon materials (silicon powder).

[0055] Example 2

[0056] a. Wash the rice husk ash, dry it at 50°C for 6h, and grind it to obtain rice husk ash powder;

[0057] b. Weigh 20 g of rice husk ash, mix with 5 g of potassium hydroxide, add to 150 mL of deionized water, stir evenly to obtain a rice husk ash - potassium hydroxide slurry;

[0058] c. The rice husk ash - potassium hydroxide slurry was dried at 70 ° C, and then ground to obtain 8 purpose rice husk ash - potassium hydroxide powder;

[0059] d. The above-mentioned 25 grams of rice husk ash-potassium hydroxide powder and 200 grams of calcium chloride (80%)-sodium chloride (15%)-calcium oxide (5%) molten salt are placed in an alumina crucible, and the crucible temperature is raised to 800° C. by a high-temperature resistance furnace under the protection of high-purity nitrogen and kept warm for 10 hours. During this process, the rice husk ash will be directly activated-pyrolyzed, and the silicon dioxide therein will be dissolved; this step finally obtains a solid phase product and a calcium chloride (80%)-sodium chloride (15%)-calcium oxide (5%)-silicon oxide dissolution solution;

[0060] e. The calcium chloride (80%) - sodium chloride (15%) - calcium oxide (5%) - silicon oxide solution and solid phase product were separated by filtration using a 10-mesh corundum sieve;

[0061] f. The solid phase product was washed with dilute hydrochloric acid and deionized water in turn, and then dried at 80 ° C for 4 h, and then ground to obtain porous carbon;

[0062] g. The obtained calcium chloride (80%) - sodium chloride (15%) - calcium oxide (5%) - silicon oxide solution was then used as an electrolyte and kept at 800°C in high-purity nitrogen; a high-purity graphite plate and zinc particles were used as an anode and a cathode, respectively, and then electrodeposited at a constant voltage of 3 volts for 2 hours;

[0063] h. After the electrodeposition is completed, the electrodeposition product attached to the cathode is washed with hydrochloric acid and deionized water in turn to remove zinc and residual salt, and then dried to obtain silicon powder.

[0064] The specific surface area analysis results of the porous carbon obtained in this example are as follows: Figure 5The results show that the porous carbon has a high specific area of ​​735 square meters per gram. The high specific area provides a large number of surface sites for the porous carbon, which is conducive to its wide application in environmental protection, catalysis, carrier, energy storage and other fields. The scanning electron microscopy and energy spectrum element analysis results of the porous carbon are shown in Figure 6 As shown, the results show that porous carbon with higher purity is prepared. Figure 7 The X-ray diffraction pattern of electrodeposited silicon (silicon powder) is shown, and the results are similar to those of Example 1 ( Figure 3 )The characterization results of the silicon powder obtained are similar. Figure 8 The microscopic morphology of electrodeposited silicon (silicon powder) presents typical irregular particles with specific surface area and complex pore structure. The above results fully prove that the method proposed by the present invention can effectively prepare porous carbon and silicon materials (silicon powder).

[0065] In addition, by comparing the porous carbon and silicon powder products obtained in Example 1 and Example 2, it can be seen that:

[0066] (1) When the KOH ratio is high (the KOH ratio in Example 2 is 1 / 4 of that in rice husk ash, and the KOH ratio in Example 1 is 1 / 9 of that in reed), the SiO2 dissolution rate is fast and the porous carbon pores are more abundant (as can be seen). Figure 2 Middle left picture and Figure 6 (Comparison between the left and right images).

[0067] (2) When calcium chloride-sodium chloride-calcium oxide is used as the molten salt and the proportion of sodium chloride is high (the proportion of sodium chloride in Example 2 is 15%, which accounts for 13.3% of the total mass after mixing; the proportion of sodium chloride in Example 1 is 8%, which accounts for 7.5% of the total mass after mixing), the molten salt temperature can be reduced (the molten salt temperature in Example 1 is 850°C, and the molten salt temperature in Example 2 is 800°C).

[0068] In summary, in the technical solution of the present application, the microstructure of carbon can be regulated by the amount of potassium hydroxide added, the ratio of calcium chloride-sodium chloride-calcium oxide molten salt, and the activation dissolution temperature and time; the micromorphology of silicon can be regulated by electrochemical parameters.

[0069] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing porous carbon and silicon powder using silicon-rich biomass, characterized in that: The method comprises the following steps: a. The silicon-rich biomass or the ash after pyrolysis of the silicon-rich biomass is washed, then dried and crushed to obtain a silicon-rich biomass powder; b. The silicon-rich biomass powder obtained in step a is mixed with potassium hydroxide and then a solvent is added to prepare a silicon-rich biomass-potassium hydroxide slurry; c. drying and grinding the silicon-rich biomass-potassium hydroxide slurry obtained in step b to obtain a silicon-rich biomass-potassium hydroxide powder; d. In an inert gas atmosphere, the silicon-rich biomass-potassium hydroxide powder obtained in step c is activated and dissolved in a calcium chloride-sodium chloride-calcium oxide molten salt to obtain a silicon-rich biomass activated dissolution product; e. The activated dissolution product of the silicon-rich biomass obtained in step d is then placed in a calcium chloride-sodium chloride-calcium oxide molten salt for activation and dissolution, and the treatment is performed multiple times; after the treatment is completed, a solid phase product and a calcium chloride-sodium chloride-calcium oxide-silicon oxide molten salt dissolution solution are obtained by filtration and screening; f. washing and drying the solid phase product obtained in step e to obtain a porous carbon material; g. In an inert gas atmosphere, the calcium chloride - sodium chloride - calcium oxide - silicon oxide molten salt solution obtained in step e is used as an electrolyte, kept warm, and electrodeposited with graphite or zinc as a cathode and graphite as an anode to obtain a cathode having a silicon product deposited thereon; h. The cathode with the silicon product deposited thereon prepared in step g is taken out from the reaction vessel, and after cleaning and drying, silicon powder is finally obtained.

2. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: The silicon-rich biomass raw material in step a includes one or more of rice husks, rice straws, reeds, bagasse or coconut shells; the ash after pyrolysis of the silicon-rich biomass is one or more of the ash obtained after pyrolysis of rice husks, rice straws, reeds, bagasse or coconut shells; the drying temperature is 50-90°C and the time is 2 to 6 hours.

3. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: The mass ratio of the silicon-rich biomass powder to potassium hydroxide in step b is 1:(0-1), wherein the mass of potassium hydroxide is not 0; the solvent in the silicon-rich biomass-potassium hydroxide slurry is deionized water; The drying temperature in step c is 50-90° C. and the drying time is 2-6 hours.

4. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: In the calcium chloride-sodium chloride-calcium oxide molten salt described in step d, the mass fraction ratio of calcium chloride: sodium chloride: calcium oxide is: (0-100wt%): (0-50wt%): (0-10wt%), wherein the mass fractions of the three are not 0; the inert gas is any one of argon or nitrogen; the mass ratio between the silicon-rich biomass-potassium hydroxide powder and the calcium chloride-sodium chloride-calcium oxide molten salt is (0-2): (5), wherein the mass of the silicon-rich biomass-potassium hydroxide powder is not 0; the activation dissolution time is 0-12 hours, and the temperature is 600-900°C.

5. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: The number of multiple treatments in step e is 0 to 5 times; the filter screen used in the filtering and screening is any one of an alumina ceramic screen, a quartz screen or a graphite screen.

6. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: The drying temperature in step f is 50-90° C. and the drying time is 2-6 hours.

7. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: In step g, the graphite is a solid cathode and the zinc is a liquid cathode; the inert gas is either argon or nitrogen; the insulation temperature is 600-900° C.; and the electrodeposition conditions are a voltage of 1.5-3.0 volts or a current of 10-50 mA / cm2.

8. The method for preparing porous carbon and silicon powder using silicon-rich biomass according to claim 1, characterized in that: The drying temperature in step h is 50 to 90° C. and the drying time is 2 to 6 hours.

9. A porous carbon, characterized in that: Obtained by the method for preparing porous carbon and silicon powder using silicon-rich biomass as described in any one of claims 1 to 8.

10. A silicon powder, characterized in that: Obtained by the method for preparing porous carbon and silicon powder using silicon-rich biomass as described in any one of claims 1 to 8.

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