Preparation method of nanometer-sized porous silicon with controllable size

Abstract

The present invention discloses a method for preparing size-controllable nano-scale porous silicon, comprising: (1) preparing a precursor Si x O y Preparation of the obtained precursor Si x O y Surface activation treatment was performed, and then the precursor Si was washed with deionized water until neutral and freeze-dried; (3) the activated precursor Si x O y The mixture is uniformly mixed with a reducing agent and an inorganic salt, calcined and reduced under an inert atmosphere, and then naturally cooled to room temperature under an inert atmosphere to obtain a mixture; (4) the obtained solid mixture is etched with an acid, a dispersant is added, and then washed with deionized water until it is neutral, and freeze-dried to obtain dispersed porous silicon materials of different sizes. The preparation method of the present invention is environmentally friendly, and the obtained porous silicon material has uniform pore size, dispersed particles without agglomeration, and no structural collapse.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material processing, and particularly relates to a preparation method of nano-sized porous silicon with controllable size. BACKGROUND

[0002] Porous silicon is a three-dimensional nano-porous material, which has the characteristics of large specific surface area, photoluminescence and excellent anti-reflection performance. The porous structure also brings abundant active sites and high connectivity. At present, the research on porous silicon has been involved in a series of energy conversion and storage devices such as biological and chemical sensors, drug delivery, lithium ion batteries, supercapacitors and the like.

[0003] According to different etching processes, the preparation of porous silicon mainly includes electrochemical etching method (anodic oxidation method), photochemical etching method, chemical etching method, dealloying method and magnesium hot reduction method. The electrochemical etching method is the most commonly used method for preparing porous silicon material at present. HF is used as the electrolyte, p / n type silicon material is used as the anode, and Pt or graphite is used as the cathode to carry out anodic oxidation reaction. However, in the reaction process, silicon plate is generally used, and the composition and concentration of the electrolyte, the resistivity and crystal phase of silicon, the temperature during electrolysis and the light conditions all have important influence on the film formation speed of porous silicon, and the current density is not uniformly distributed on the silicon material, resulting in uneven and incomplete etching of the material surface, and the material is doped with many impurities. The photochemical etching method is to immerse bulk silicon in a solution of HF under the action of light to carry out etching reaction. The main factors affecting the etching speed are the concentration of the solution, the doping degree of the silicon wafer and the light intensity. The chemical etching method is to use noble metals such as Pt and Au on the surface of bulk Si, and then etch the noble metals to form a porous structure. However, the correlation and mutual restriction between the internal variables of the etching reaction (such as the type and morphology of noble metals, etchant, internal characteristics of Si substrate, temperature, etc.) are still not accurately mastered, and the repeatability is poor. The dealloying method is to etch the metal in the Si-metal alloy to obtain porous silicon material. However, the proportion of Si-metal greatly affects the morphology and performance of the final porous silicon. The higher the metal content, the larger the specific surface area of the formed porous silicon, and the higher the porosity. However, if the metal content in the alloy exceeds a certain amount, the porous silicon after etching will not be able to maintain the original structure, the specific surface area and porosity will decrease, and the cycle stability of the material will also decrease. Therefore, the performance of the porous silicon prepared by the dealloying method is closely related to the alloy type, size, silicon content in the alloy and other parameters, so the electrochemical performance obtained by using silicon alloys made by different manufacturers as precursors to prepare porous silicon for performance test is also quite different. For silicon alloys produced by the same manufacturer, the silicon content in the alloy also affects the performance of the product. The magnesium hot reduction method is to synthesize silicon by reducing SiO2 with Mg, and then use HF etching treatment to remove residual SiO2 to obtain porous silicon with good electrochemical performance. The existing magnesium hot reduction method for producing porous silicon material has the following problems: incomplete reaction, leading to the generation of by-product Mg2Si, non-uniform surface of powder particles, collapse of pore structure, environmental unfriendliness (using HF for etching) and other problems.

[0004] In summary, the main problems of the existing porous silicon preparation are: (1) the raw material used in the existing method is mainly bulk silicon, which is irregular or two-dimensional in morphology. The size of the porous silicon prepared from the raw material is uncontrollable, and the particle size is micron level. When used to prepare electrode materials, the agglomeration is serious, the performance of the prepared electrode material is poor, and the cycle stability of the electrode is not good; (2) in the etching process, HF solution is mostly used, which is not environmentally friendly, and the powder particles obtained by etching have uneven pore size and collapsed pore structure. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a preparation method of size-controllable nanoscale porous silicon.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A preparation method of size-controllable nanoscale porous silicon, comprising the following steps:

[0008] (1) Preparation of precursor: ammonia water is added to an ethanol aqueous solution to adjust the pH, and then tetraethyl orthosilicate is added after sufficient stirring. After the reaction is completed, the precipitate is washed with deionized water and freeze-dried to obtain Si x O y precursor material A; wherein x is 1-2, and y is 1-6;

[0009] (2) The Si x O y precursor material A obtained in step (1) is dispersed in anhydrous ethanol, a dispersing agent is added, and then ultrasonic dispersion and stirring reaction are performed. The precipitate is washed with deionized water to obtain Si x O y precursor material B;

[0010] (3) The Si x O y precursor material B obtained in step (2) is added to an activation solution, and stirring is performed. The precipitate is washed with deionized water to neutralization, and then freeze-dried to obtain Si x O y precursor material C;

[0011] (4) The Si x O y precursor material C obtained in step (3) is mixed with a reducing agent and an inorganic salt, and then calcination reduction is performed under an inert atmosphere. After cooling to room temperature, a solid mixture is obtained.

[0012] (5) The solid mixture obtained in step (4) is etched with an acid, and a dispersing agent is added. Then, the mixture is washed with deionized water to neutralization, and then freeze-dried to obtain nanoscale porous silicon.

[0013] As preferred, in step (2), the dispersant is at least one of polyethylene glycol, polyvinylpyrrolidone and Tween@80.

[0014] Polyethylene glycol, as a non-ionic dispersant, has good solubility and wettability, and can form hydrogen bonds or Van der Waals forces with Si x O y The surface O or adsorbed H2O molecules form hydrogen bonds or Van der Waals forces, and when hydrogen bonds are formed with H2O molecules, the interaction force between Si x O y Particles is effectively reduced; the hydrophilic groups in the molecular structure of polyvinylpyrrolidone interact with the surface of Si x O y Particles to form an adsorption film, resulting in repulsion and surface tension between particles, changing the hydrophilicity and lipophilicity of the particle surface, and the molecular structure has a certain stability, while adjusting the rheological properties of the solution, and the protective film formed can improve the stability of the particles; Tween@80 is an oleate, as a non-ionic surfactant, has strong hydrophilicity and emulsifying property, can competitively occupy the interface position, inhibit Si x O y Adsorption to the gas-liquid interface, thereby reducing oxidation or aggregation caused by contact with air, and also effectively preventing Si x O y From the interface during the reaction.

[0015] As preferred, in step (3), the surface activator is at least one of palladium chloride, copper sulfate, silver nitrate and stannous chloride.

[0016] Palladium chloride, copper sulfate, silver nitrate and stannous chloride all contain excess electrons, which can provide additional electron donors; and all have leaving group properties, forming relatively stable negative ions after leaving the corresponding ions; and all have a certain reducing property, which can participate in the reduction reaction by giving electrons or negative charges, thereby accelerating the reaction.

[0017] As preferred, in step (4), the reducing agent is at least one of magnesium powder, magnesium diboride, magnesium carbide and magnesium oxide.

[0018] Si x O y Is fully reduced, while reducing the generation of by-products.

[0019] As preferred, in step (5), the acid is at least one of hydrochloric acid, nitric acid and acetic acid.

[0020] Hydrofluoric acid has strong corrosiveness and the volatilized gas has strong stimulation to human skin and respiratory tract, and can react with the human body to produce insoluble substances and block blood vessels.

[0021] As preferably, in step (5), the dispersant is at least one of polyethylene glycol, sodium oleate, polyvinylpyrrolidone and Tween@80.

[0022] As preferably, in step (1), the volume ratio of tetraethyl orthosilicate to ammonia water is 1:(1-25), the volume ratio of ethanol to deionized water in the ethanol-water solvent is (4-20):1; the reaction temperature is 25-80℃, and the reaction time is 4-12h.

[0023] As preferably, in step (2), the dispersant and Si x O y The mass ratio of precursor material A is (0.5-2):1, the mass-volume ratio of dispersant to anhydrous ethanol is (1.5-1500)g:(10-1000)mL; the stirring time after ultrasonic treatment is 6-12h.

[0024] As preferably, in step (3), the activator and Si x O y The mass ratio of precursor material B is (0.01-0.5):1, the mass-volume ratio of activator to ethanol aqueous solution is (0.04-2)g:(20-1000)mL; the activation treatment time is 0.5-2h.

[0025] As preferably, in step (4), the Si x O y The molar ratio of precursor material C to reducing agent is 1:(1-2.5), the Si x O y The molar ratio of precursor material C to inorganic salt is 1:(1-10); the calcination reduction temperature is 500-900℃, and the calcination reduction time is 2-10h.

[0026] As preferably, in step (5), the concentration of acid is (0.1-10)mol / L; the temperature of acid etching treatment is 25-65℃, and the time is 0.5-12h.

[0027] The beneficial effects of the present application are:

[0028] 1、The present application can synthesize Si x O y Precursor materials of different sizes by adopting hydrolysis and polycondensation reaction of tetraethyl orthosilicate in ethanol aqueous solution. x Oy The precursor material is mixed with inorganic salt and reducing agent after dispersion activation treatment and calcination reduction, and granular dispersed nano-Si x O y The precursor material; the obtained nano-Si x O y The precursor material is etched in acid liquid with added dispersant, and granular complete dispersed, pore size uniform spherical nano-porous silicon material can be obtained; the preparation is convenient and simple, low cost, and the preparation process uses non-toxic and harmless chemical reactants, which is environment-friendly and green.

[0029] 2、The present application can effectively remove excess heat generated in the high exothermic reaction by introducing inorganic salt in the calcination reduction step, preventing the collapse and crosslinking of the pore structure of the obtained porous silicon. Moreover, the inorganic salt can act as an agglomeration inhibitor, effectively preventing the generation of by-product Mg2Si and the agglomeration of the product porous silicon, not only maintaining the advantages of nanostructure in cycle stability, but also inhibiting the formation of excess SiO x . BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The XRD pattern of the SiO x precursor material of example 1, 2, 3.

[0031] Figure 2 The XRD pattern of the porous silicon material of example 1, 2, 3.

[0032] Figure 3 The SEM pattern of the SiO x precursor material of example 1.

[0033] Figure 4 The SEM pattern of the SiO x precursor material of example 2.

[0034] Figure 5 The SEM pattern of the SiO x precursor material of example 3.

[0035] Figure 6 The SEM pattern of the 50nm porous silicon material of example 1.

[0036] Figure 7 The SEM pattern of the 200nm porous silicon material of example 2.

[0037] Figure 8 The SEM pattern of the 500nm porous silicon material of example 3.

[0038] Figure 9 The SEM pattern of the 50nm porous silicon material of example 4.

[0039] Figure 10 SEM image of 200nm porous silicon material of Example 5.

[0040] Figure 11 SEM image of 500nm porous silicon material of Example 6. Detailed method

[0041] In order to better understand the present application, the following further illustrates the content of the present application in combination with examples, but the content of the present application is not limited to the following examples only.

[0042] Example 1

[0043] A preparation method of 50nm porous silicon, specifically:

[0044] S1: Synthesis of 50nm SiO2 precursor material: add ammonia water to 100mL deionized water to adjust the PH to 8.5, then add 20mL tetraethyl orthosilicate and 80mL anhydrous ethanol to the solution, react at 60℃ for 12h, wash the precipitate with deionized water to neutral, freeze-drying to obtain 50nm SiO2 precursor material, and the XRD and SEM tests of the material are as shown in Figure 1 、 Figure 3 .

[0045] As can be seen from Figure 1 , the SiO2 precursor material is successfully synthesized, and as can be seen from Figure 3 , the size of the synthesized SiO2 precursor material is 50nm.

[0046] S2: Pretreatment of the SiO2 precursor material prepared in step S1: disperse 0.2g SiO2 in 20mL anhydrous ethanol, add 0.9g polyethylene glycol solution, ultrasonic dispersion for 0.5h, then stir for 6h, wash with deionized water, then add it to 20mL, 10g / L SnCl2 solution, stir for 0.5h, then add it to 5g / L PdCl2 solution and activate for 0.5h, wash with deionized water to neutral, freeze-drying for standby;

[0047] S3: uniformly mix the pretreated SiO2 precursor material prepared in step S2, Mg2C3 and NaCl, and the amount-of-substance ratio of the substances in the mixture is 1:1:0.005;

[0048] S4: heat the mixture prepared in step S3 to 500℃ in a nitrogen atmosphere, keep constant temperature for 4h, then naturally cool to room temperature in an inert gas atmosphere, to obtain the corresponding solid powder;

[0049] S5: The solid powder prepared in step S4 was added into 20 mL of 0.5 M HNO3 solution, 1.5 mL of Tween@80 was added, and the mixture was stirred for 1 h, then washed with deionized water until neutral, and freeze-dried to obtain 50 nm porous silicon material.

[0050] The XRD and SEM tests of the 50 nm porous silicon material obtained in Example 1 are shown in Figure 2 , Figure 6 It can be seen from Figure 2 that the porous silicon is successfully synthesized in this example, and it can be seen from Figure 6 that the synthesized 50 nm porous silicon forms a rich porous structure, the pore size is uniform, and the pores are not collapsed and crosslinked.

[0051] Example 2

[0052] A method for preparing 200 nm porous silicon, specifically comprising:

[0053] S1: Synthesis of 200 nm SiO2 precursor material: 15 mL of tetraethyl orthosilicate was added into 150 mL of ethanol aqueous solution (volume ratio of anhydrous ethanol and deionized water is 2:1) after the solution was stirred well, and the pH was adjusted to 8 by adding ammonia water. The solution was reacted at 40℃ for 6 h, washed with deionized water until neutral, and freeze-dried to obtain 200 nm SiO2 precursor material. The XRD and SEM tests of the material are shown in Figure 1 , Figure 4 It can be seen from Figure 1 that the SiO2 is successfully synthesized in this example, and it can be seen from Figure 4 that the synthesized SiO2 is 50 nm;

[0054] S2: Pretreatment of the SiO2 precursor material prepared in step S1: 0.2 g of SiO2 was dispersed in 20 mL of anhydrous ethanol, 0.9 g of polyethylene glycol solution was added, and the mixture was ultrasonically dispersed for 0.5 h, then stirred for 6 h, and washed with deionized water until clean. Then it was added into 20 mL of 10 g / L CuSO4 solution and activated for 2 h, washed with deionized water until neutral, and freeze-dried for standby use;

[0055] S3-S5: Same as Example 1.

[0056] The XRD and SEM tests of the 200 nm porous silicon material obtained in Example 2 are shown in Figure 2 , Figure 7 . Figure 2 It can be seen that the Si is successfully synthesized in this example, Figure 7 and it can be seen that the synthesized 200 nm porous silicon is not agglomerated and the particles are dispersed.

[0057] Example 3

[0058] A preparation method of 500nm porous silicon, specifically comprising:

[0059] S1: synthesis of 500nm SiO2 precursor material: in 50mL ethanol aqueous solution (volume ratio of anhydrous ethanol and deionized water is 19:1) add ammonia water to adjust PH to 9, then add 2mL tetraethyl orthosilicate in the solution, react at room temperature for 12h, wash with deionized water to neutral, freeze-drying to obtain 500nm SiO2 precursor material, XRD and SEM test of the material is shown in Figure 1 、 Figure 5 From Figure 1 , we successfully synthesized SiO2, Figure 5 It can be seen that the synthesized SiO2 is 50nm;

[0060] S2: pretreatment of SiO2 precursor material prepared in step S1: disperse 0.2g SiO2 in 20mL anhydrous ethanol, add 0.9g polyethylene glycol solution, ultrasonic dispersion for 0.5h, then stir for 6h, wash with deionized water. Then add it to 30mL of 8g / L AgNO3 solution and activate for 0.5h, wash with deionized water to neutral, freeze-drying for standby;

[0061] S3-S5: same as example 1.

[0062] XRD and SEM test of 500nm porous silicon material obtained in example 3 is shown in Figure 2 、 Figure 8 . Figure 2 From Figure 8 , we successfully synthesized Si, It can be seen that the synthesized 500nm porous silicon is arranged in order, the porous structure is dense and uniform.

[0063] Example 4

[0064] A preparation method of 50nm porous silicon, specifically comprising:

[0065] S1: same as example 1;

[0066] S2: pretreatment of 50nm SiO2 precursor prepared in step S1: disperse 0.2g SiO2 in 20mL anhydrous ethanol, add 1.2g polyvinylpyrrolidone, ultrasonic dispersion for 0.5h, then stir for 6h, wash with deionized water. Then add it to 20mL of 10g / L SnCl2 solution, stir for 0.5h, then add to 5g / L PdCl2 solution and activate for 0.5h, wash with deionized water to neutral, freeze-drying for standby;

[0067] S3: uniformly mixing the pretreated SiO2 precursor material prepared in the step S2: Mg: NaCl, the substance amount ratio in the mixture being 1:1.2:0.005;

[0068] S4: heating the mixture prepared in the step S3 to 600℃ in a nitrogen atmosphere, keeping constant temperature for 5h, and then naturally cooling to room temperature in an inert gas atmosphere to obtain a corresponding solid powder;

[0069] S5: adding the solid powder calcined in the step S4 to 20mL of 1.2M HCl solution, adding 1.2g of polyethylene glycol, stirring for 1h, and then washing with deionized water until neutral, and freeze-drying to obtain 50nm porous silicon material.

[0070] The SEM of the 50nm porous silicon material obtained in Example 4 is shown in Figure 9 . Figure 9 It can be seen that the 50nm porous silicon synthesized by the present application forms a rich porous structure, the pore size is uniform, and the pores are not collapsed and crosslinked.

[0071] Example 5

[0072] A preparation method of 200nm porous silicon, specifically comprising:

[0073] S1: the same as Example 2;

[0074] S2: pretreating the 200nm SiO2 precursor prepared in the step S1: dispersing 0.2g of SiO2 in 20mL of anhydrous ethanol, adding 2.5mL of Tween@80 solution, ultrasonic dispersion for 0.5h, stirring for 6h, and then washing with deionized water until clean. Then, it is added to 20mL of 10g / L SnCl2 solution, stirred for 0.5h, and then added to 5g / L PdCl2 solution for activation for 0.5h, washed with deionized water until neutral, and freeze-dried for standby;

[0075] S3: uniformly mixing the pretreated SiO2 precursor material prepared in the step S2: MgB2: NaCl, the substance amount ratio in the mixture being 1:1.5:0.008;

[0076] S4: heating the mixture prepared in the step S3 to 650℃ in a nitrogen atmosphere, keeping constant temperature for 6h, and then naturally cooling to room temperature in an inert gas atmosphere to obtain a corresponding solid powder;

[0077] S5: The solid powder prepared in step S4 was added to 20 mL of 1.5 M CH3COOH solution, 0.5 g of polyvinylpyrrolidone and 0.5 g of sodium oleate were added, stirred for 1 h, then washed with deionized water to neutral, and freeze-dried to obtain 200 nm porous silicon material.

[0078] The SEM of the 200 nm porous silicon material obtained in Example 5 is shown in Figure 10 . Figure 10 It can be seen that the synthesized 200 nm porous silicon has no particle agglomeration, and the pore structure is dense and uniform.

[0079] Example 6

[0080] A method for preparing 500 nm porous silicon, specifically:

[0081] S1: The same as Example 3;

[0082] S2: The 500 nm SiO2 precursor material prepared in step S1 was pretreated: 0.2 g of SiO2 was dispersed in 20 mL of anhydrous ethanol, 1.5 g of polyethylene glycol solution was added, and ultrasonic dispersion was performed for 0.5 h, then stirred for 6 h, and washed with deionized water. Then it was added to 20 mL of 10 g / L SnCl2 solution, stirred for 0.5 h, then added to 2 g / L Ag(NO3)2 solution for activation for 0.5 h, washed with deionized water to neutral, and freeze-dried for use;

[0083] S3: The pretreated SiO2 precursor material prepared in step S2 was uniformly mixed with Mg, MgO and NaCl, and the amount-of-substance ratio of the substances in the mixture was 1:1:0.005;

[0084] S4: The mixture prepared in step S3 was heated to 800°C in a nitrogen atmosphere, kept at a constant temperature for 8 h, then naturally cooled to room temperature in an inert gas atmosphere, to obtain the corresponding solid powder;

[0085] S5: The solid powder prepared in step S4 was added to 20 mL of 5 M HCl solution, 1.5 mL of Tween@80 was added, stirred for 6 h, then washed with deionized water to neutral, and freeze-dried to obtain 500 nm porous silicon material.

[0086] The SEM test of the 500 nm porous silicon material obtained in Example 6 is shown in Figure 11 . Figure 11 It can be seen that the synthesized 500 nm porous silicon has no particle agglomeration, and the pore structure is dense and uniform.

[0087] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification of the above embodiment according to the technical essence of the present application, equivalent changes, fall within the protection scope of the present application.

Claims

1. A method for preparing a nanoscale porous silicon of controllable size, characterized in that, The method comprises the following steps: (1) Preparation of the precursor: ammonia water is added to adjust the pH in an ethanol aqueous solution, and then tetraethyl orthosilicate is added after sufficient stirring, and the reaction is stirred. After the reaction is completed, the precipitate is washed with deionized water and freeze-dried to obtain Si x O y Precursor material A; (2) The Si obtained in step (1) is dispersed in anhydrous ethanol, a dispersant is added, and after ultrasonic dispersion, the reaction is stirred, and the precipitate is washed clean with deionized water to obtain Si x O y The precursor material A is dispersed in anhydrous ethanol, a dispersant is added, and after ultrasonic dispersion, the reaction is stirred, and the precipitate is washed clean with deionized water to obtain Si x O y The precursor material B; (3) The Si obtained in step (2) is added to the activated solution, stirred, and the precipitate is washed with deionized water until neutral, and freeze-dried to obtain Si x O y The precursor material B is added to the activated solution, stirred, and the precipitate is washed with deionized water until neutral, and freeze-dried to obtain Si x O y The precursor material C; (4) Si obtained in step (3) is mixed with the reducing agent and the inorganic salt to obtain a solid mixture. x O y The precursor material C is mixed with a reducing agent and an inorganic salt, and then calcination reduction is performed under an inert atmosphere. After cooling to room temperature, a solid mixture is obtained. (5) etching the solid mixture obtained in step (4) with an acid, adding a dispersing agent, washing with deionized water until neutral, and freeze-drying to obtain nano-sized porous silicon.

2. The method for preparing size-controllable nanoscale porous silicon according to claim 1, characterized in that, In step (2), the dispersing agent is at least one of polyethylene glycol, polyvinylpyrrolidone and Tween@80.

3. The method according to claim 1, wherein the method is characterized by, In step (3), the activator in the activation solution is at least one of palladium chloride, copper sulfate, silver nitrate and stannous chloride.

4. The method according to claim 1, wherein the method is characterized by, In step (4), the reducing agent is at least one of magnesium powder, magnesium diboride, magnesium carbide and magnesium oxide.

5. The method according to claim 1, wherein the method is characterized by, In step (5), the acid is at least one of hydrochloric acid, nitric acid and acetic acid.

6. The method for preparing size-controllable nanoporous silicon according to claim 1, wherein: In step (5), the dispersing agent is at least one of polyethylene glycol, polyvinylpyrrolidone and Tween@80.

7. The method according to claim 1, wherein the method is characterized by, In step (1), the volume ratio of tetraethyl orthosilicate to ammonia water is 1:(1-25), the volume ratio of ethanol to deionized water in the ethanol-water solvent is (4-20):1; the reaction temperature is 25-80℃, and the reaction time is 4-12h.

8. The method according to claim 1, wherein the method is characterized by, In step (2), the dispersant and Si x O y The mass ratio of the precursor material A is (0.5-2):1, the mass-volume ratio of the dispersant and anhydrous ethanol is (1.5-1500) g:(10-1000) mL; and the stirring time after ultrasonic treatment is 6-12 h.

9. The method according to claim 1, wherein the method is characterized by, In step (4), Si x O y The molar ratio of the precursor material C to the reducing agent is 1:(1-2.5), Si x O y The molar ratio of the precursor material C to the inorganic salt is 1:(1-10); the calcination reduction temperature is 500-900℃, and the calcination reduction time is 2-10h.

10. The method for preparing size-controllable nano-porous silicon according to claim 1, characterized in that: In step (5), the concentration of the acid is (0.1-10) mol / L; the temperature of the acid etching treatment is 25-65℃, and the time is 0.5-12h.

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