Silicon microparticles for hydrogen production

Abstract

To provide an industrially favorable hydrogen production method using silicon fine particles.SOLUTION: A hydrogen production method according to one aspect of the present invention includes a step of bringing silicon fine particles having a crystallite diameter of 100 nm or less and a hydrophilic surface into contact with water or an aqueous solution containing ethanol. The characteristic use of the water or aqueous solution containing ethanol in this hydrogen production method makes it possible to produce a practically viable amount of hydrogen with high certainty.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to a hydrogen production device, a hydrogen production method, silicon fine particles for hydrogen production, and a method for producing silicon fine particles for hydrogen production. [Background technology]

[0002] In recent years, fuel cells have been attracting attention as one of the candidates for next-generation energy sources from the perspective of measures against resource depletion and environmental protection. Therefore, the development of technology for producing hydrogen, which is used in fuel cells as an alternative fuel to petroleum, plays a central role in predicting the success or failure of future development in the field of fuel cells. As a conventional technology for producing hydrogen as such an energy source, a technology for producing hydrogen by contacting water with fine silicon powder having an average particle size of 2 μm (microns) or less has been disclosed (for example, Patent Document 1).

[0003] Meanwhile, with regard to silicon powder, the inventors of the present application have disclosed a method for producing silicon microparticles using silicon particles, known as cutting chips, produced when forming a thin substrate (wafer) from a silicon base material (ingot), not limited to silicon powder crushed into microparticles, and a technique for applying the obtained silicon microparticles to silicon ink or solar cells (e.g., Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-115349 A [Patent Document 2] JP 2012-229146 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the hydrogen production technology disclosed in the prior art, the amount of hydrogen gas generated from 15 g of silicon powder when reacted for 1 hour is only in the range of 0.2 mmol (millimola) to 2.9 mmol, which is not sufficient for practical industrial application.

[0006] On the other hand, with regard to silicon particles, from the viewpoint of effective utilization of resources and environmental protection, it is desirable to effectively utilize silicon particles obtained from, for example, chips formed by cutting silicon or silicon polishing waste, which are usually treated as waste.

[0007] The present invention solves at least one of the technical problems described above, effectively utilizes silicon waste, and greatly contributes to the realization of a hydrogen production apparatus and method that are economically and industrially advantageous. [Means for solving the problem]

[0008] The inventors of the present application have focused on the effective utilization of silicon fine chips and shavings (hereinafter collectively referred to as "silicon chips") or silicon polishing chips, which are usually treated as waste in the cutting process of silicon in the production process of semiconductor products, which are discarded in large quantities in the semiconductor field, and have been working diligently on research into hydrogen production technology with excellent practicality and industrial applicability. As a result, they have found that it is possible to effectively utilize silicon waste and produce large amounts of hydrogen even under mild conditions. The present invention has been created based on the above-mentioned perspective.

[0009] One hydrogen production device of the present invention comprises a crushing unit that forms silicon fine particles by crushing silicon chips or silicon polishing debris, and a hydrogen generation unit that generates hydrogen by contacting the silicon fine particles with water or an aqueous solution and / or dispersing them in the water or aqueous solution.

[0010] This hydrogen production device can reliably produce a practical amount of hydrogen using silicon chips or silicon polishing waste, which is usually treated as waste from silicon cutting processing in the production process of semiconductor products, as a starting material. In this way, this hydrogen production device not only effectively utilizes silicon chips or silicon polishing waste, which can be considered waste, and greatly contributes to environmental protection, but also significantly reduces the production cost of hydrogen, which will be used as a next-generation energy resource, for example, in fuel cells. Therefore, this hydrogen production device can significantly improve industrial productivity in hydrogen production.

[0011] Furthermore, one hydrogen production method of the present invention includes a crushing step of crushing silicon chips or silicon polishing waste to form silicon fine particles, and a hydrogen generation step of generating hydrogen by contacting the silicon fine particles with water or an aqueous solution and / or dispersing them in the water or the aqueous solution.

[0012] According to this hydrogen production method, it is possible to reliably produce a practical amount of hydrogen using silicon chips or silicon polishing waste, which is usually treated as waste from, for example, silicon cutting processing in the production process of semiconductor products, as a starting material. In this way, this hydrogen production method not only effectively utilizes silicon chips or silicon polishing waste, which can be considered waste, and greatly contributes to environmental protection, but also realizes a significant reduction in the production cost of hydrogen, which will be used as a next-generation energy resource, for example, fuel cells. Therefore, according to this hydrogen production method, it is possible to significantly improve industrial productivity in hydrogen production.

[0013] Moreover, one of the silicon microparticles for hydrogen production according to the present invention has an irregular shape and a crystallite size distribution in the range of 100 nm (nanometers) or less. Among the silicon microparticles formed by pulverizing silicon cutting chips or silicon polishing waste, silicon microparticles that have been chemically treated (typically, an oxide film removal treatment using a hydrofluoric acid aqueous solution and / or an ammonium fluoride aqueous solution, or a hydrophilization treatment using a fourth liquid in each embodiment described later) are a suitable example of the silicon microparticles for hydrogen production described above.

[0014] Moreover, one method for producing silicon fine particles for hydrogen production according to the present invention includes a crushing step of crushing silicon chips or silicon polishing dust to form silicon fine particles.

[0015] According to the above-mentioned silicon microparticles for hydrogen production and the method for producing silicon microparticles for hydrogen production, it is possible to provide an intermediate material that can realize the reliable production of practical amounts of hydrogen from, for example, silicon cutting chips or silicon polishing waste that is usually treated as waste resulting from the cutting process of silicon in the production process of semiconductor products. Effect of the Invention

[0016] Furthermore, according to one of the hydrogen production devices and one of the hydrogen production methods of the present invention, it is possible to reliably produce a practical amount of hydrogen using silicon cutting chips or silicon polishing chips, which are usually considered waste, as a starting material. Therefore, the effective use of silicon cutting chips or silicon polishing chips, which can be considered waste, contributes to environmental protection and contributes to a significant reduction in the production cost of hydrogen, which will be used as a next-generation energy resource. Furthermore, according to one of the silicon fine particles for hydrogen production of the present invention and one of the production methods for silicon fine particles for hydrogen production of the present invention, it is possible to provide an intermediate material that can reliably produce a practical amount of hydrogen from silicon cutting chips or silicon polishing chips, which are usually considered waste, produced by, for example, silicon cutting processing in the production process of semiconductor products. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram showing each step of the hydrogen production method according to the first embodiment. [Diagram 2] FIG. 4 is a diagram showing each step of a hydrogen production method according to a second embodiment. [Diagram 3] FIG. 4 is a diagram showing each step of a hydrogen production method according to a third embodiment. [Figure 4] FIG. 11 is an explanatory diagram illustrating a schematic configuration of a hydrogen production device according to a fourth embodiment. [Diagram 5] 2 is a cross-sectional TEM (transmission electron microscope) photograph showing the crystal structure of silicon fine particles after the crushing step in Example 1. [Figure 6] FIG. 2 is a diagram showing the crystallite size distribution of silicon fine particles after a pulverization process. [Figure 7] 2 is a graph showing the amount of hydrogen generated in Examples 1, 2, and 3. [Figure 8] 1 is a graph showing the amount of hydrogen generated in Examples 4 and 5. [Figure 9] 1 is a graph showing the amount of hydrogen generated immediately after the start of the reaction in Examples 4 and 5. [Figure 10] FIG. 13 is an explanatory diagram illustrating a schematic configuration of a hydrogen production device according to a modified example of the fourth embodiment. [Figure 11] 1 is a graph showing the amount of hydrogen generated versus reaction time in Example 6. [Figure 12] 1 is a graph showing the difference in maximum hydrogen generation rate due to different pH values ​​in Example 6. [Figure 13] FIG. 13 is an XPS spectrum of silicon fine particles after a hydrogen generation reaction in Example 6. [Figure 14] 1 is a graph showing the amount of hydrogen generated per gram versus reaction time in Example 7. [Explanation of symbols]

[0018] 1. Silicon waste 2. Silicon microparticles 3. Silicon microparticles after removing the surface oxide film 4 Silicon microparticles after hydrophilic treatment 5. Hydrogen 10 Crusher 14 Outlet 15 Filters 30 Drying room 40 Rotary Evaporator 50 Surface oxide film removal tank 57,67,77 Mixer 58 Centrifuge 60 Hydrophilic treatment tank 70 Hydrogen generation unit 72 Reactor 75 Water or aqueous solution 79 Transfer pipe 80 Aquarium 87 Hydrogen collector 89 Hydrogen Pipe 90 Hydrogen storage container 100,200 Hydrogen production equipment 250 Additional surface oxide film removal tank 270 Additional hydrogen generation unit DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are given common reference symbols throughout the drawings unless otherwise specified. In addition, in the drawings, the elements of each embodiment are not necessarily shown to scale. In addition, some symbols may be omitted in order to make each drawing easier to see.

[0020] 1. Hydrogen production method <First embodiment> The hydrogen production method of this embodiment includes various steps using silicon cutting chips or silicon polishing waste (hereinafter also referred to as "silicon waste"), which is usually discarded as waste in the cutting process of silicon in the production process of semiconductor products, as an example of a starting material. Silicon waste also includes fine chips obtained by crushing discarded wafers. Figure 1 is a diagram showing each step of the hydrogen production method of this embodiment. As shown in Figure 1, the hydrogen production method of this embodiment includes the following steps (1) to (3). (1) Cleaning process (S1) (2) Grinding process (S2) (3) Hydrogen generation process (S3)

[0021] (1) Cleaning process In the cleaning step (S1) of this embodiment, for example, silicon waste generated during the cutting process of a monocrystalline or polycrystalline silicon ingot is cleaned. This cleaning step (S1) is mainly aimed at removing organic matter adhering to the silicon waste, typically organic matter such as cutting oil and additives used in the cutting process. First, the silicon waste to be cleaned is weighed, and then a predetermined first liquid is added, and the silicon waste is dispersed in the liquid by a ball mill. Here, the ball mill of this embodiment is a grinding machine that uses steel balls, magnetic balls, boulders, and the like as grinding media. Also, an example of the first liquid of this embodiment described above is acetone.

[0022] Thereafter, the silicon waste material that has been subjected to the cleaning process is passed through a filter, and the above-mentioned first liquid is removed by suction filtration. The removed first liquid is disposed of as waste liquid. The filtered silicon waste material is then dried using a dryer. Note that the drying temperature in this embodiment is, for example, 40°C or higher and 60°C or lower. In addition, since a ball mill machine is used in the cleaning process of this embodiment, it is possible to significantly improve the cleaning efficiency compared to a process in which the material is simply immersed in the first liquid.

[0023] (2) Crushing process Then, in the pulverization step (S2), the washed silicon sludge is pulverized to form silicon fine particles having a crystallite diameter of 100 nm or less. If the crystallite diameter of the silicon fine particles is 100 nm or less, even if the aggregate particle size distribution of the silicon fine particles is within the range of 100 nm to 5 μm, a good effect, that is, an effect equivalent to the effect of this embodiment, can be obtained. Then, a predetermined second liquid is added to the washed silicon sludge. An example of the second liquid is propanol. Then, a coarse pulverization process is performed using a ball mill. The silicon waste material that has been subjected to the coarse pulverization process is passed through a filter to remove relatively coarse particles, and the remaining silicon waste material is finely pulverized using a bead mill. Then, the second liquid is removed using a rotary evaporator, and silicon fine particles are obtained as a result of the fine pulverization process.

[0024] The pulverization step (S2) of this embodiment makes it possible to form silicon fine particles that are amorphous, have a crystallite size distribution in the range of 100 nm, and have a hydrophilic surface. In addition, in this pulverization step (S2), the pulverization process can be performed using any one of the following pulverizers: a bead mill, a ball mill, a jet mill, and a shock wave pulverizer, or a combination of these.

[0025] (3) Hydrogen generation process In the subsequent hydrogen generation step (S3), hydrogen is generated by contacting the silicon fine particles obtained in the crushing step (S2) with water or an aqueous solution and / or dispersing them in water or an aqueous solution. The water used in this hydrogen generation step does not necessarily need to be pure water, and may be water containing electrolytes or organic matter, such as general tap water or industrial water. The type of aqueous solution in this embodiment is also not particularly limited. The hydrogen ion concentration exponent (pH value) of the aqueous solution is not particularly limited, but it is more preferable that the pH value is 10 or more. This is because, according to the analysis results of the inventors, it has been confirmed that the higher the pH value, the faster the hydrogen production rate becomes and the hydrogen production reaction tends to end in a shorter time. Therefore, when it is desired to continue supplying a small amount of hydrogen for a long period of time, it is a preferable embodiment to intentionally lower the pH value of the above-mentioned aqueous solution. On the other hand, when it is desired to temporarily supply a large amount of hydrogen, it is possible to produce hydrogen according to the requirements of each industry or users of various devices by setting the pH value of the above-mentioned aqueous solution high.

[0026] The temperature of the water used in the hydrogen generation step can also be set arbitrarily to obtain a desired hydrogen production rate. In addition, in the means for contacting the silicon fine particles with water or an aqueous solution and / or dispersing them in the water or an aqueous solution, stirring, water flow, shaking, etc. can be used as necessary. Note that stirring, etc. promotes the hydrogen production reaction, and therefore the rate at which hydrogen is produced can be increased.

[0027] As described above, according to the hydrogen production method of the present embodiment, it is possible to reliably produce a practical amount of hydrogen by using silicon chips or silicon polishing waste, which is usually considered waste, as the starting material, for example, from silicon cutting processing in the production process of semiconductor products. Therefore, it contributes to environmental protection by effectively utilizing silicon chips or silicon polishing waste, which can be considered waste, and contributes to a significant reduction in the production cost of hydrogen to be used as a next-generation energy resource. Furthermore, it is worth noting that according to the present embodiment, it is possible to produce a large amount of hydrogen at a practical level without going through complicated processes.

[0028] <Second embodiment> This embodiment is the same as the first embodiment, except that a surface oxide film removing step of removing the oxide film on the surface of the silicon fine particles is added after the pulverizing step in the first embodiment.

[0029] 2 is a diagram showing each step of the hydrogen production method of the present embodiment. As shown in FIG. 2, the hydrogen production method of the present embodiment includes the following steps (1) to (4). (1) Cleaning process (T1) (2) Crushing process (T2) (3) Surface oxide film removal process (T3) (4) Hydrogen generation process (T4)

[0030] As described above, the cleaning step (S1), the pulverization step (S2), and the hydrogen generation step (S3) in the hydrogen production method of the first embodiment overlap with the cleaning step (T1), the pulverization step (T2), and the hydrogen generation step (T4) in this embodiment. Therefore, the description of each step other than the surface oxide film removal step (T3) may be omitted.

[0031] The surface oxide film removing step (T3) will be described below.

[0032] In the surface oxide film removing step (T3), the silicon fine particles obtained in the above-mentioned pulverizing step (T2) are subjected to a treatment of contacting with an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution. In this embodiment, the silicon fine particles obtained in the pulverizing step (T2) having a crystallite size distribution in the range of 100 nm or less are immersed in an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution. As a result, the silicon fine particles are brought into contact with the aqueous hydrofluoric acid solution or the aqueous ammonium fluoride solution and / or dispersed in each of the aforementioned aqueous solutions. Thereafter, the silicon fine particles and the aqueous hydrofluoric acid solution are separated by a centrifuge. Then, the silicon fine particles are immersed in a third liquid such as an ethanol solution. Then, the third liquid is removed to obtain silicon fine particles for hydrogen production.

[0033] In the surface oxide film removing step of this embodiment, the silicon fine particles are immersed in an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution to bring the silicon fine particles into contact with the aqueous hydrofluoric acid solution or the aqueous ammonium fluoride solution. However, the surface oxide film removing step of this embodiment is not limited to these aspects. For example, a step of bringing the aqueous hydrofluoric acid solution or the aqueous ammonium fluoride solution into contact with the silicon fine particles by other methods may also be adopted. For example, spraying the aqueous hydrofluoric acid solution or the aqueous ammonium fluoride solution onto the silicon fine particles in a so-called shower is another aspect that may be adopted.

[0034] In the subsequent hydrogen generation step (T4), the silicon fine particles after the removal of the surface oxide film are brought into contact with water or an aqueous solution and / or dispersed in each of the aforementioned aqueous solutions to generate hydrogen.

[0035] According to the hydrogen production method of the present embodiment, it is possible to obtain the same effects as those of the first embodiment, and also to increase the amount of hydrogen produced by removing the oxide film on the surface of the silicon fine particles.

[0036] <Third embodiment> This embodiment is the same as the second embodiment, except that a hydrophilic treatment step for hydrophilizing the surfaces of silicon fine particles is added after the surface oxide film removing step in the second embodiment.

[0037] 3 is a diagram showing each step of the hydrogen production method of the present embodiment. As shown in FIG 3, the hydrogen production method of the present embodiment includes the following steps (1) to (5). (1) Cleaning process (U1) (2) Crushing process (U2) (3) Surface oxide film removal process (U3) (4) Hydrophilic treatment process (U4) (5) Hydrogen generation process (U5)

[0038] As described above, the cleaning step (T1), the pulverization step (T2), the surface oxide film removal step (T3), and the hydrogen generation step (T4) in the hydrogen production method of the second embodiment overlap with the cleaning step (U1), the pulverization step (U2), the surface oxide film removal step (U3), and the hydrogen generation step (U5) in this embodiment. Therefore, the description of each step other than the hydrophilization step (U4) may be omitted.

[0039] The hydrophilization treatment step (U4) will be described below. In the hydrophilic treatment step (U4) in this embodiment, the surface of the silicon fine particles is treated with a surfactant or nitric acid after the surface oxide film removal step. When treating with a surfactant, a typical example of the surfactant is at least one selected from the group consisting of anionic surfactants, cationic surfactants, and nonionic surfactants. In this embodiment, for example, the silicon fine particles are brought into contact with and / or dispersed in a fourth liquid such as propanol, and a surfactant or nitric acid is added, followed by stirring. In this embodiment, after stirring, the fourth solution is removed by a rotary evaporator.

[0040] In the subsequent hydrogen generation step (U5), hydrogen is generated by contacting the hydrophilically treated silicon fine particles with water or an aqueous solution and / or dispersing them in each of the aforementioned aqueous solutions.

[0041] According to the hydrogen production method of this embodiment, the same effects as those of the first embodiment can be obtained, and the hydrophilization process can reduce the surface tension of the silicon fine particles, which is a phenomenon specific to fine particles, and highly reliably suppress the floating of the silicon fine particles to the water surface. As a result, the silicon fine particles become more compatible with water or an aqueous solution, and the contact area between the silicon fine particles and the water or an aqueous solution increases, thereby accelerating the hydrogen production reaction. Therefore, it is possible to significantly increase the amount of hydrogen produced.

[0042] As described above, among the silicon microparticles formed by pulverizing silicon cutting chips or silicon polishing waste, silicon microparticles that have been chemically treated (typically, the oxide film removal treatment using an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution in the second embodiment, or the hydrophilization treatment using the fourth liquid in the third embodiment) are a suitable example of silicon microparticles for hydrogen production in each of the above-mentioned embodiments. Therefore, in each of the above-mentioned embodiments, including a chemical treatment step in which the silicon microparticles are chemically treated as described above is a suitable aspect from the viewpoint of further promoting hydrogen generation.

[0043] 2. Hydrogen production equipment <Fourth embodiment> The hydrogen production device 100 of this embodiment will be described below. Fig. 4 is an explanatory diagram that shows a schematic configuration of the hydrogen production device 100 of this embodiment. As shown in Fig. 4, the hydrogen production device 100 of this embodiment mainly includes a pulverizer 10, a drying chamber 30, a rotary evaporator 40, a surface oxide film removal tank 50, a centrifuge 58, a hydrophilic treatment tank 60, a hydrogen generation unit 70, and a hydrogen storage container 90. The hydrogen production device 100 of this embodiment can be said to be an assembly of devices (processing units) that perform a plurality of processes described below, and therefore the hydrogen production device 100 may be called a hydrogen production system.

[0044] The pulverizer 10 of this embodiment is a wet pulverizer that receives the material to be treated together with the liquid and pulverizes and disperses the material in the liquid. The pulverizer 10 can perform processes such as dispersion, mixing, and pulverization on the material to be treated and the liquid that have been introduced. The pulverizer 10 can be any one of a group of pulverizers consisting of a bead mill, a ball mill, a jet mill, and a shock wave pulverizer, or a combination of these. In the hydrogen production device 100 of this embodiment, the pulverizer 10 has both a washing section that washes silicon waste such as silicon cutting chips or silicon polishing chips generated in the silicon cutting process, and a pulverization section that pulverizes the washed silicon waste to produce silicon fine particles having a crystallite diameter of 100 nm or less.

[0045] In the pulverizer 10, first, the silicon waste material 1, which is the object to be processed, and the second liquid of the first embodiment are fed into the pulverizer 10 from the inlet 11, and the silicon waste material 1 is washed. Then, the washed silicon waste material 1 is passed through a filter 15 provided near the outlet 14 together with the second liquid, and the second liquid is removed by suction filtration to become waste liquid. Next, the residue (silicon waste material 1) is dried in the drying chamber 30, and is fed again from the inlet 11 together with the second liquid, and the pulverizer 10 performs a pulverization process. Specifically, after coarse pulverization is performed in a ball mill or the like, the pulverized material is passed through the filter 15 together with the second liquid to remove the coarse particles. Next, fine pulverization is performed in a bead mill or the like. Next, the finely pulverized material is collected, and the second liquid is removed using a rotary evaporator 40 that automatically performs reduced pressure distillation, thereby obtaining silicon fine particles 2.

[0046] The surface oxide film removal tank 50, which is an example of a surface oxide film removal section in this embodiment, is equipped with an agitator 57, and treats the silicon fine particles 2 obtained from the crusher 10 with hydrofluoric acid or an aqueous ammonium fluoride solution 55. Thereafter, the silicon fine particles 3 after the surface oxide film removal are separated from the aqueous hydrofluoric acid solution by a centrifuge 58. When the surface oxide film of the silicon fine particles 2 is not removed, the silicon fine particles 2 are sent to a hydrogen generating section 70 described later.

[0047] The hydrophilic treatment tank 60, which is an example of the hydrophilic treatment section of this embodiment, is equipped with a stirrer 67, and the silicon fine particles 3 before or after the removal of the surface oxide film are brought into contact with and / or dispersed in the fourth liquid 65 to which a surfactant or nitric acid has been added. When the silicon fine particles 2 are not subjected to the hydrophilic treatment, the silicon fine particles before or after the removal of the surface oxide film are sent to a hydrogen generating section 70, which will be described later. In the hydrophilic treatment of this embodiment, it is possible to subject the silicon fine particles in a state before the removal of the surface oxide film to the hydrophilic treatment, but from the viewpoint of realizing the hydrophilic treatment of the silicon fine particles with a higher degree of accuracy, it is preferable to subject the silicon fine particles after the removal of the surface oxide film to the hydrophilic treatment.

[0048] The hydrogen generation unit 70 of this embodiment includes a reaction tank 72 equipped with an agitator 77, a water tank 80, a hydrogen collector 87, a transfer pipe 79, and a hydrogen pipe 89. In the reaction tank 72, at least one selected from the group consisting of silicon fine particles 2, silicon fine particles 3 after removal of a surface oxide film, and silicon fine particles 4 after hydrophilic treatment is brought into contact with water or an aqueous solution 75 and / or dispersed in the water or an aqueous solution 75 to generate hydrogen 5. The generated hydrogen 5 is sent into the water 85 in the water tank 80 via the transfer pipe 79. The hydrogen 5 collected by the hydrogen collector 87 by a water displacement method, as an example, is collected in a hydrogen storage container 90 via the hydrogen pipe 89.

[0049] According to the hydrogen production device 100 of this embodiment, it is possible to produce a practical amount of hydrogen at a relatively high speed using silicon cutting chips or silicon polishing waste as starting material, which is usually treated as waste material during the cutting process of silicon in the production process of semiconductor products, for example.

[0050] <Example> In the following, in order to explain the above-mentioned embodiment in more detail, examples will be given, but the above-mentioned embodiment is not limited to these examples. The following Examples 1 to 5 show the results of hydrogen production tests performed using the hydrogen production device 100.

[0051] Example 1 In Example 1, hydrogen was produced based on the hydrogen production method of the first embodiment by the hydrogen production device 100. Specifically, after the washing step and the crushing step, a hydrogen generation step was carried out.

[0052] (1) Cleaning process 200g (grams) of silicon chips were mixed with 200mL (milliliters, also written as "ml") of acetone and dispersed in a ball mill for 1 hour. The ball mill was a Universal Ball Mill manufactured by Masuda. A BALL MILL was used. The balls used were alumina beads with particle sizes of φ10 mm (millimeters) and φ20 mm. The liquid was then removed by suction filtration, and the residue was dried in a dryer set at 40°C.

[0053] (2) Crushing process Next, 15 g of the washed silicon sludge is weighed into a plastic container, and 285 g of 2-propanol is added. Next, alumina balls are placed in a ball mill, and coarse pulverization is performed for 2 hours at a peripheral speed of 80 rpm. The ball mill used in this example is Universal Ball Mill manufactured by Masuda Corporation. The balls used in this example are alumina balls with particle sizes of φ10 mm and φ20 mm. The product obtained by the grinding process was passed through a 180 μm mesh filter to remove coarse particles.

[0054] Next, alumina balls were placed in a bead mill and finely pulverized for 4 hours at a peripheral speed of 2908 rpm. The bead mill used in this example was Star Mill LMZ015 manufactured by Ashizawa Finding Co., Ltd. The beads used in this example were 456 g of zirconia beads with a particle size of φ0.5 mm. Next, the finely pulverized material was collected and 2-propanol was removed using a rotary evaporator to obtain silicon fine particles.

[0055] (3) Hydrogen generation process 0.86 g of silicon microparticles for hydrogen production were immersed in 50.21 g of ultrapure water. In this example, the experiment was carried out at room temperature (about 25° C.).

[0056] Example 2 In Example 2, hydrogen was produced by the hydrogen production device 100 based on the hydrogen production method of the second embodiment. Therefore, the same process as in Example 1 was performed, except that a surface oxide film removal process was added after the crushing process in Example 1. Specifically, hydrogen was produced in the following order: cleaning process, crushing process, surface oxide film removal process, and hydrogen generation process. The surface oxide film removal process is as follows.

[0057] In the surface oxide film removal process, the silicon fine particles obtained in the pulverization process of this embodiment are dispersed in a 50% aqueous solution of hydrofluoric acid, and then the silicon fine particles and the aqueous solution of hydrofluoric acid are separated by a centrifuge. The silicon fine particles obtained are then immersed in an ethanol solution. After that, the ethanol solution is removed to obtain silicon fine particles for hydrogen production.

[0058] Example 3 In Example 3, hydrogen was produced by the hydrogen production device 100 based on the hydrogen production method of the third embodiment. Therefore, the same process as Example 2 was performed, except that a treatment using a surfactant was added as a hydrophilic treatment process after the surface oxide film removal process.

[0059] Specifically, the washing step, the pulverization step, and the surface oxide film removal step were carried out under the same conditions as in Example 2. In addition, in the treatment using a surfactant in the hydrophilization treatment step, the concentration of silicon fine particles was adjusted to 5 wt% in 2-propanol, which is the fourth liquid in the third embodiment. Then, 0.05% of a nonionic surfactant polyoxyethylene noniphenyl ether ("Nonion NS206" manufactured by Nippon Oil & Fats Co., Ltd.) was added to this liquid, and the mixture was stirred for 1 hour. After that, the 2-propanol was removed by a rotary evaporator.

[0060] Furthermore, in the hydrogen generation process, 50.21 g of ultrapure water was added to 0.86 g of silicon microparticles for hydrogen production and immersed at room temperature.

[0061] Example 4 In Example 4, the hydrogen production apparatus 100 was used in the hydrogen production method of the second embodiment, and the hydrogen generation process was carried out in the same manner as in Example 2, except that a buffer solution consisting of 0.1 mol / L sodium bicarbonate and 0.1 mol / L sodium carbonate was used as the aqueous solution for the hydrogen generation process, and the pH value of the aqueous solution was adjusted to 10.

[0062] Example 5 In Example 5, the hydrogen production device 100 was used in the hydrogen production method of the second embodiment, and the hydrogen production process was carried out in the same manner as in Example 2, except that a 0.1 mol / L potassium hydroxide aqueous solution was used as the aqueous solution for the hydrogen generation process, and the pH value of the aqueous solution was adjusted to 13.

[0063] <Analysis results of the embodiment> 1. Crystal structure analysis using cross-sectional TEM images FIG. 5 is a cross-sectional TEM (transmission electron microscope) photograph showing the crystal structure of silicon microparticles after the pulverization process in Example 1. FIG. 5(a) shows a state in which the silicon microparticles have partially aggregated to form slightly larger microparticles of irregular shape. Meanwhile, FIG. 5(b) is a TEM photograph focusing on individual silicon microparticles. As shown by the circle in the center of FIG. 5(b), silicon microparticles with a size of approximately 5 nm or less were confirmed. It was also confirmed that these silicon microparticles have crystallinity.

[0064] 2. Crystallite size distribution of silicon microparticles measured by X-ray diffraction method FIG. 6 is a diagram showing the results of analyzing the crystallite size distribution of silicon fine particles after the pulverization process by X-ray diffraction. In the graph shown in FIG. 6, the horizontal axis represents the crystallite size (nm) and the vertical axis represents the frequency. The solid line represents the crystallite size distribution based on the number distribution, and the dashed line represents the crystallite size distribution based on the volume distribution. In the number distribution, the mode diameter was 1.97 nm, the median diameter (50% crystallite diameter) was 3.70 nm, and the average diameter was 5.1 nm. In the volume distribution, the mode diameter was 13.1 nm, the median diameter was 24.6 nm, and the average diameter was 33.7 nm. From these results, it was confirmed that the silicon fine particles obtained after the pulverization process are so-called silicon nanoparticles, in which the crystallite diameter is distributed in the range of 100 nm or less, especially 50 nm or less, by the treatment using the bead mill method.

[0065] 3. Hydrogen production volume Fig. 7 is a graph showing the results of measuring the amount of hydrogen generated for Example 1, Example 2, and Example 3. The horizontal axis in Fig. 7 represents the immersion time (minutes), and the vertical axis in Fig. 7 represents the amount of hydrogen generated per 1 g of silicon microparticles for hydrogen production (mL / g).

[0066] As shown in FIG. 7, in Example 1 in which the surface oxide film removing step was not performed, 10.7 mL of hydrogen was obtained after an immersion time of 7905 minutes.

[0067] 7, in Example 2 in which hydrogen was produced using the hydrogen production method of the second embodiment with the above-mentioned hydrogen production device 100, an equilibrium state was reached after an immersion time of 5700 minutes (i.e., 95 hours), and approximately 54.1 mL of hydrogen was produced. In Example 1, a large amount of hydrogen, 50 mL to 60 mL per 1 g of silicon microparticles for hydrogen production, was finally produced, and a particularly noteworthy and extremely good result was obtained.

[0068] Furthermore, in Example 3, 116.7 mL of hydrogen was obtained by immersion for 9805 minutes (i.e., about 163 hours), and even better results were obtained than in Example 2. In particular, it can be seen that the amount of hydrogen generated in Examples 2 and 3 from the beginning until 500 minutes or 1000 minutes had elapsed was much greater than the amount of hydrogen generated in Example 1. In other words, it can be seen that the rate of hydrogen generation in Examples 2 and 3 from the beginning until 500 minutes or 1000 minutes had elapsed was extremely fast. Therefore, FIG. 7 shows the remarkable effect of the surface oxide film removal step or the surface oxide film removal section.

[0069] Next, the results of Examples 4 and 5, in which silicon fine particles were reacted with an aqueous solution having a high pH value in the hydrogen generation process, were examined. Fig. 8 is a graph showing the results of measuring the amount of hydrogen generated for Examples 4 and 5. Fig. 9 is a graph showing the amount of hydrogen generated from the start of the reaction until 60 minutes have elapsed in Examples 4 and 5. The horizontal axis of Figs. 8 and 9 shows the immersion time (minutes), and the vertical axis of Figs. 8 and 9 shows the amount of hydrogen generated (mL / g) per 1 g of silicon fine particles for hydrogen production.

[0070] As shown in Fig. 8, in Example 4, in which the pH value of the aqueous solution in the hydrogen generation step was 10, equilibrium was reached after 5000 minutes (about 80 hours), and about 720 ml of hydrogen was obtained per gram of silicon microparticles for hydrogen production. On the other hand, in Example 5, in which the pH value of the aqueous solution in the hydrogen generation step was 13, equilibrium was reached after 6254 minutes (about 104 hours), and about 942.1 ml of hydrogen was obtained per gram of silicon microparticles for hydrogen production. In this way, when the pH value was made alkaline to 10 or 13, a large amount of hydrogen was obtained that was several to several tens of times larger than in Examples 1 to 3.

[0071] Furthermore, as shown in the results of Example 5 in FIG. 9, when the pH value of the aqueous solution in the hydrogen generation step was set to 13, the amount of hydrogen generation increased rapidly immediately after the silicon fine particles and the aqueous solution were reacted. More specifically, after 10 minutes, about 470 ml of hydrogen was generated per 1 g of silicon fine particles for hydrogen production, and after 30 minutes, about 590 ml of hydrogen was generated per 1 g of silicon fine particles for hydrogen production. In addition, in Example 4, in which the pH value of the aqueous solution in the hydrogen generation step was 10, after 13 minutes, about 3.5 ml of hydrogen was generated per 1 g of silicon fine particles for hydrogen production, and after 30 minutes, about 15 ml of hydrogen was generated per 1 g of silicon fine particles for hydrogen production. In Example 4, the reaction was slower than in Example 5, but a larger amount of hydrogen could be obtained in a shorter time than in Examples 1 to 3.

[0072] 8 and 9, it was confirmed that the hydrogen production rates in Examples 4 and 5 were also significantly faster than those in Examples 1 to 3. Therefore, it was found that by increasing the pH value of the aqueous solution in the hydrogen generation step (i.e., making the pH value 10 or higher), the hydrogen production reaction is promoted rapidly in a short period of time, rather than the gradual hydrogen production reaction over a long period of time as shown in Examples 1 to 3. Therefore, making the pH value of the aqueous solution in the hydrogen generation step 10 or higher (14 or lower) is a very suitable embodiment from the viewpoint of obtaining a larger amount of hydrogen more quickly.

[0073] The hydrogen production method and hydrogen production device disclosed in each of the above-mentioned embodiments are expected to be widely used in technical fields requiring hydrogen, such as fuel cells. Moreover, an interesting point of the hydrogen production method and hydrogen production device of each of the above-mentioned embodiments is that silicon cutting chips or silicon polishing chips, which are usually waste materials produced by cutting silicon in the manufacturing process of semiconductor products, are used as starting materials. Therefore, the cost per unit gram of produced hydrogen is much cheaper than that of hydrogen obtained by conventional hydrogen production methods, and therefore not only can the effective use of waste materials contribute to environmental protection, but also the economic efficiency of hydrogen production can be significantly improved. Furthermore, the hydrogen production method and hydrogen production device of each of the above-mentioned embodiments, which do not require complicated devices, facilities, or systems, or complicated processes, can greatly contribute to increasing industrial productivity.

[0074] <Other embodiments> In the above-mentioned fourth embodiment, at least one selected from the group consisting of silicon fine particles 2, silicon fine particles 3 after removal of surface oxide film, and silicon fine particles 4 after hydrophilic treatment is brought into contact with water or an aqueous solution 75 and / or dispersed in water or an aqueous solution 75 in the reaction tank 72 of the hydrogen generation unit 70 to generate hydrogen. However, the reaction may reach an equilibrium state over time, and as a result, the amount or rate of hydrogen generation may become saturated. Therefore, as a modification of the fourth embodiment for solving such a problem, the configuration of a hydrogen production device 200 shown in FIG. 10 is disclosed, and Example 6 is also disclosed.

[0075] FIG. 10 is an explanatory diagram that shows a schematic configuration of a hydrogen production device 200 in a modified example of the fourth embodiment. The hydrogen production device 200 of this embodiment is similar to the hydrogen production device 100 of the fourth embodiment, except that, as shown in (R) in FIG. 10, the silicon fine particles in the reaction vessel 72, whose hydrogen generation amount or hydrogen generation rate has once become saturated or is about to become saturated, are taken out of the reaction vessel 72, and then introduced into an additional surface oxide film removal vessel 250 constituting at least a part of the additional surface oxide film removal section in the hydrogen production device 200 to remove the oxide film on the silicon fine particle surface (additional surface oxide film removal process), and then the silicon fine particles from which the oxide film has been removed are sent again to the reaction vessel 72 to generate hydrogen (additional hydrogen generation process). The hydrogen production device 200 of this embodiment is similar to the hydrogen production device 100 of the fourth embodiment, except that the hydrogen production device 200 of this embodiment is provided with an additional hydrogen generation section 270 in which the silicon fine particles are introduced into an additional surface oxide film removal vessel 250 constituting at least a part of the additional surface oxide film removal section in the hydrogen production device 200 to remove the oxide film on the silicon fine particles (additional surface oxide film removal process). Therefore, a duplicated description may be omitted.

[0076] When the hydrogen production device 200 shown in Fig. 10 is employed, even if the amount or rate of hydrogen generation becomes saturated or nearly saturated once because the reaction in the reaction vessel 72 reaches an equilibrium state, the silicon fine particles will again have the ability to generate hydrogen by performing an additional surface oxide film removal process thereafter. That is, performing an additional surface oxide film removal process in which the silicon fine particles are again brought into contact with hydrofluoric acid or an ammonium fluoride aqueous solution during or after the hydrogen generation process in each of the above-mentioned embodiments regenerates or recovers the hydrogen generation ability of the silicon fine particles. Therefore, the utilization efficiency of the silicon fine particles for hydrogen generation is significantly improved, and this can also greatly contribute to reducing the cost of hydrogen production.

[0077] Unlike the hydrogen production apparatus 200, another aspect that can be adopted is to provide a means for supplying the silicon fine particles to the surface oxide film removal tank 50 via a flow path that communicates with the surface oxide film removal tank 50 from the reaction tank 72 after the silicon fine particles in the reaction tank 72 are separated from the water or aqueous solution 75 by a filter. In this embodiment, the silicon fine particles introduced into the surface oxide film removal tank 50 are also included in the "silicon fine particles discharged from the hydrogen generation unit" in this application. In addition, as in the fourth embodiment, another aspect that can be adopted is to carry out a hydrophilization treatment step (additional hydrophilization treatment step) after the additional surface oxide film removal step.

[0078] In addition, in the above-mentioned embodiment, the surface oxide film removal step and the additional surface oxide film removal step are performed using the same surface oxide film removal tank, and the hydrogen generation step and the additional hydrogen generation step are performed using the same reaction tank 72, but the above-mentioned embodiment is not limited to this embodiment. Therefore, the surface oxide film removal step and the additional surface oxide film removal step may be performed in separate tanks, and the hydrogen generation step and the additional hydrogen generation step may be performed in separate tanks.

[0079] Example 6 In the hydrogen generation process of Example 6, 0.86 g of silicon fine particles formed by crushing p-type silicon chips with ZiO2 beads using a bead mill in the same manner as in Example 5 were immersed in an aqueous solution (0.1 mol / L aqueous potassium hydroxide solution) 75. Note that, for the aqueous solution of Example 6, four types of aqueous solutions 75 with pH values ​​of 12.1, 12.9, 13.4, and 13.9 were prepared by changing the amount of potassium hydroxide (KOH) added.

[0080] A certain amount (0.86 g) of silicon fine particles was immersed in each aqueous solution at room temperature, and a graph of the amount of hydrogen generated versus reaction time was obtained, as shown in FIG. 11. For example, in the case of a pH value of 13.9, it was found that the amount of hydrogen generated per gram of silicon fine particles reached approximately 1100 mL or more (i.e., approximately 1100 mL / g or more) in an extremely short time (within approximately 15 minutes from the start of the reaction). It is particularly noteworthy that in the case of a pH value of 13.9, the amount of hydrogen generated exceeded 1000 mL per gram of silicon fine particles in a short time of approximately 10 minutes. At this stage, the additional surface oxide film removal process and additional hydrogen generation process described above were not performed.

[0081] Next, FIG. 12 is a graph showing the difference in maximum hydrogen generation rate due to the difference in pH value in Example 6. Each value shown in FIG. 12 indicates the maximum hydrogen generation rate per minute and per gram in the above-mentioned four types of aqueous solutions when the pH value shown in FIG. 11 is changed. From the results shown in FIG. 12, it was found that the maximum hydrogen generation rate per minute and per gram clearly depends on the pH value, and the higher the pH value, the higher the maximum hydrogen generation rate. In addition, by utilizing the fact that the hydrogen generation rate depends on the pH value of the solution, it is possible to control the hydrogen generation rate. Note that, even at this stage, the above-mentioned additional surface oxide film removal process and additional hydrogen generation process are not performed.

[0082] Here, the reaction reached an equilibrium state at a pH value of 13.9, and as a result, the amount or rate of hydrogen generation was saturated. The silicon fine particles were measured and analyzed using an XPS (X-ray Photoelectron Spectroscopy) analyzer. Fig. 13 is an XPS spectrum diagram of the silicon fine particles after the amount or rate of hydrogen generation was saturated in Example 6.

[0083] the result, Figure 13 As shown in the figure, there are several Si atoms belonging to silicon (Si) and silicon dioxide (SiO2). 2pA peak was observed. Therefore, it was revealed that a silicon dioxide (SiO2) film was formed on the surface of silicon fine particles where the reaction had reached or nearly reached equilibrium. Figure 13 From the peak intensity ratio of (Si) and (SiO2) shown in Fig. 1, it was concluded that a SiO2 film with a thickness of about 5 nm was formed on the surface of this silicon microparticle.

[0084] Therefore, in Example 6, the silicon fine particles in which the reaction had reached or nearly reached equilibrium were contacted with a 5% HF aqueous solution to remove the SiO2 film (additional surface oxide film removal step). After that, the silicon fine particles were again immersed in the above-mentioned aqueous solution 75 with a pH value of 13.9. As a result, 470 ml / g (per initial 1 g) of hydrogen was generated again from the silicon fine particles (additional hydrogen generation step).

[0085] As a result of the above, in Example 6, the total amount of hydrogen gas generated (up to saturation) and the amount of hydrogen gas generated by carrying out the additional surface oxide film removal step and the additional hydrogen generation step was about 1570 mL per 1 g of silicon fine particles. This is close to the maximum amount of hydrogen generated, 1600 mL (theoretical value), that can be generated from 1 g of silicon in a reaction in aqueous solution 75. Therefore, it was found that carrying out the additional surface oxide film removal step and the additional hydrogen generation step is very useful as a means for realizing an extremely large amount of hydrogen generation.

[0086] Example 7 Next, other results of a hydrogen production test performed using the hydrogen production device 100 will be described. In the hydrogen generation process of Example 7, the aqueous solution 75 is an aqueous solution containing sodium hydroxide or ammonia. 0.86 g of silicon fine particles were contacted with and / or dispersed in the aqueous solution 75 and reacted at room temperature.

[0087] FIG. 14 is a graph showing the amount of hydrogen generated per 1 gram versus reaction time in Example 7. Experimental value (a) is the result when 20 mL of an aqueous solution with added sodium hydroxide (NaOH, also known as caustic soda) and a pH value of 13.4 was used. Experimental value (b) is the result when 20 mL of an aqueous solution with added ammonia (NH3) and a pH value of 11.9 was used. The horizontal axis in FIG. 14 indicates the immersion time (minutes). And the vertical axis in FIG. 14 indicates the amount of hydrogen generated per 1 gram of silicon microparticles for hydrogen production (mL / g).

[0088] When silicon fine particles are immersed in the above-mentioned aqueous solution 75 to which ammonia has been added, the silicon fine particles may float on the surface of the aqueous solution unless any particular prior treatment is performed. Therefore, in Example 7, the silicon fine particles were contacted with the aqueous solution 75 to which ammonia has been added by using a method in which ethanol is dropped into the aqueous solution 75 to cause the silicon fine particles to settle to the bottom of the reaction tank 72. On the other hand, for the aqueous solution 75 to which sodium hydroxide has been added, an experiment was performed by contacting and / or dispersing the silicon fine particles in the aqueous solution 75 in the same manner as in the case of potassium hydroxide.

[0089] As shown in Fig. 14, it was confirmed that the amount or rate of hydrogen generation can be controlled by varying the type or pH value of the aqueous solution. Therefore, for example, in the hydrogen generation process in each of the above-mentioned embodiments, adjusting the hydrogen generation rate and / or amount by changing the pH value of the water or aqueous solution 75 is a very suitable mode that can be adopted. Similarly, further providing an adjustment unit that adjusts the hydrogen generation rate and / or amount by changing the pH value of the water or aqueous solution 75 in the hydrogen production device 100 or the hydrogen production device 200 in the hydrogen generation unit 70 or the additional hydrogen generation unit 270 is a very suitable mode that can be adopted.

[0090] For example, the above-mentioned adjusting unit may be equipped with a device that includes a means for dripping the above-mentioned water or each aqueous solution (such as an aqueous solution with NaOH added, an aqueous solution with KOH added, or an aqueous solution with NH3 added) capable of changing the pH value for a desired amount for a desired time and a control means for controlling the pH value. More specifically, a configuration may be employed in which a dripping means that receives feedback of the measurement result from a measuring unit that measures the pH value of water or each aqueous solution 75 drips a chemical substance for adjusting the pH value, such as NaOH, KOH, or NH3, for a desired amount for a desired time to achieve the desired pH value.

[0091] On the other hand, with regard to the pH value, in view of the results of each of the above-mentioned Examples, a pH value of 10 or more, more preferably 11.9 or more, is preferred from the viewpoint of obtaining a larger amount of hydrogen more quickly.

[0092] In addition, in the surface oxide film removal step in each of the above-mentioned examples, the treatment was performed using an aqueous hydrofluoric acid solution. However, even if the treatment is performed using an aqueous ammonium fluoride solution instead of or together with the aqueous hydrofluoric acid solution, it is possible to obtain good results similar to those in each of the above-mentioned examples.

[0093] In addition, in the hydrophilic treatment step of the above embodiment, a treatment using a surfactant was performed, but even if a treatment using nitric acid is performed instead of or together with the surfactant, it is possible to obtain results almost similar to those of the above embodiment.

[0094] Furthermore, in each of the above-described embodiments, the treatment using a surfactant or nitric acid can be carried out during the hydrogen generation process by adding a surfactant or nitric acid to the water or aqueous solution in the hydrogen generation process, rather than being carried out as an independent hydrophilization treatment process.

[0095] As described in the above-mentioned Example 6, when silicon fine particles are added and dispersed in water or an aqueous solution in the hydrogen generation process, they dissolve in the water or the aqueous solution, and silicic acid is generated on the surface of the silicon fine particles. After that, the silicic acid is oxidized to silicon dioxide (SiO2), and the hydrogen generation reaction weakens or ends over time. Therefore, in order to suppress the formation of silicon dioxide (SiO2) on the surface of the silicon fine particles and to continue the hydrogen generation reaction, another suitable embodiment that can be adopted is to add a small amount of hydrofluoric acid to the water or the aqueous solution in the hydrogen generation process to continue the hydrogen generation reaction by contacting with the water or the aqueous solution.

[0096] In addition, in each of the above-mentioned embodiments, the hydrogen generating unit 70 or the additional hydrogen generating unit 270 is adopted, which generates hydrogen by contacting the formed silicon fine particles (or their aggregates) with water or an aqueous solution 75 and / or dispersing them in the aqueous solution 75 without fixing the location. However, the method of contacting the silicon fine particles with the water or aqueous solution 75 is not limited to the above-mentioned method. For example, another embodiment that can be adopted is to generate hydrogen by contacting the formed silicon fine particles with the water or aqueous solution 75 in a state where the silicon fine particles are fixed on the surface of a solid (for example, a sponge body). For example, when the solid is formed of a material that can absorb and retain liquid to a certain extent, such as a sponge body, the possibility of suppressing the generation of silicon dioxide (SiO2) on the silicon fine particles is increased by impregnating the solid with a hydrofluoric acid aqueous solution or an ammonium fluoride aqueous solution.

[0097] The disclosure of each of the above-mentioned embodiments is described for the purpose of explaining the embodiments, and is not described for the purpose of limiting the present invention. In addition, modifications within the scope of the present invention, including other combinations of each embodiment, are also included in the scope of the claims.

Claims

1. The crystallite diameter is 100 nm or less, and the agglomerated particle size distribution of the silicon fine particles is 100 nm or more and 5 μm or less, A surface from which an oxide film has been removed; and Has hydrogen generating ability, Microscopic silicon particles for hydrogen production.

2. The crystallite size is 100 nm or less, having a hydrophilic surface; and Has hydrogen generating ability, Microscopic silicon particles for hydrogen production.

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