Silicon fine particle for hydrogen production

Abstract

To provide a silicon fine particle for hydrogen production capable of realizing hydrogen production excellent in industrial applicability.SOLUTION: One silicon fine particle for hydrogen production according to the present invention has a crystallite diameter of 100 nm or less, an oxide film on a surface thereof that is not removed, and hydrogen generation capability. According to the silicon fine particle for hydrogen production, even a silicon fine particle in which the oxide film on the surface is not removed can realize hydrogen generation that can be used industrially.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 a candidate for next-generation energy sources from the perspectives of countermeasures against resource depletion and environmental protection. Therefore, the development of technology for producing hydrogen, which can be used in fuel cells as an alternative fuel to petroleum, can be said to play a central role in predicting the success or failure of future developments in the field of fuel cells. As a conventional technology for producing hydrogen as such an energy source, a technology for producing hydrogen by bringing water into contact with fine silicon powder having an average particle size of 2 μm (microns) or less has been disclosed (for example, Patent Document 1).

[0003] On the other hand, with regard to silicon powder, the present inventors have disclosed a method for producing silicon fine particles using silicon particles, so-called cutting chips, produced when forming a thin substrate (wafer) from a silicon base material (ingot), as a raw material, in addition to silicon powder produced by pulverizing silicon wafers into fine particles, and a technology for applying the obtained silicon fine particles to silicon ink or solar cells (e.g., Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-115349 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-229146 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the hydrogen production techniques disclosed in the prior art, the amount of hydrogen gas generated from 15 g of silicon powder after one hour of reaction is limited to a 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 above-mentioned technical problems, makes effective use of silicon waste, and greatly contributes to the realization of a hydrogen production device and method that are economically and industrially superior. [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 waste, which are usually treated as waste in the silicon cutting process used in the semiconductor industry and discarded in large quantities during the semiconductor product production process. They have conducted extensive research into hydrogen production technology that is highly practical and industrially viable. As a result, they have discovered that silicon waste can be effectively utilized and large amounts of hydrogen can be produced even under mild conditions. The present invention was created based on the above perspective.

[0009] One hydrogen production device of the present invention comprises a crushing unit that crushes silicon chips or silicon polishing dust to form silicon fine particles, 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 the aqueous solution.

[0010] This hydrogen production device can reliably produce a practical amount of hydrogen using silicon chips or silicon polishing dust, which are usually treated as waste from silicon cutting processes in the production of semiconductor products, as starting materials. This hydrogen production device effectively utilizes silicon chips or silicon polishing dust, which can be considered waste, and not only significantly contributes to environmental protection, but also significantly reduces the cost of producing 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 method for producing hydrogen according to 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] This hydrogen production method makes it possible to reliably produce a practical amount of hydrogen using silicon chips or silicon polishing dust, which are usually treated as waste from silicon cutting processes in the production of semiconductor products, as starting materials. This hydrogen production method not only effectively utilizes silicon chips or silicon polishing dust, which can be considered waste, and thus significantly contributes to environmental protection, but also significantly reduces the cost of producing hydrogen, which will be used as a next-generation energy resource, for example, in fuel cells. Therefore, this hydrogen production method can significantly improve industrial productivity in hydrogen production.

[0013] Furthermore, one silicon microparticle 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 silicon microparticles formed by pulverizing silicon chips or silicon polishing dust, silicon microparticles that have been chemically treated (typically, oxide film removal treatment with a hydrofluoric acid aqueous solution and / or an ammonium fluoride aqueous solution, or hydrophilization treatment with a fourth liquid, in each embodiment described below) are a suitable example of the silicon microparticle for hydrogen production.

[0014] Furthermore, one method of producing silicon microparticles for hydrogen production according to the present invention includes a pulverization step of pulverizing silicon chips or silicon polishing dust to form silicon microparticles.

[0015] The above-described silicon microparticles for hydrogen production and the method for producing silicon microparticles for hydrogen production can provide an intermediate material that can reliably produce a practical amount of hydrogen from, for example, silicon chips or silicon polishing dust that are usually treated as waste during silicon cutting processing in the production process of semiconductor products. [Effects of the Invention]

[0016] Furthermore, according to one hydrogen production apparatus and one hydrogen production method of the present invention, it is possible to reliably produce a practical amount of hydrogen using silicon shavings or silicon polishing dust, which are normally considered waste, as a starting material. Therefore, the effective use of silicon shavings or silicon polishing dust, which can be considered waste, contributes to environmental protection and contributes to a significant reduction in the cost of producing hydrogen, which will be used as a next-generation energy resource. Furthermore, according to one silicon microparticle for hydrogen production of the present invention and one method for producing silicon microparticle 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 shavings or silicon polishing dust, which are normally considered waste, for example, resulting from silicon cutting processing in the production of semiconductor products. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating each step of a hydrogen production method according to a first embodiment. [Figure 2] FIG. 4 is a diagram illustrating each step of a hydrogen production method according to a second embodiment. [Figure 3] FIG. 4 is a diagram illustrating each step of a hydrogen production method according to a third embodiment. [Figure 4] FIG. 10 is an explanatory diagram schematically illustrating the configuration of a hydrogen production device according to a fourth embodiment. [Figure 5] 2 is a cross-sectional TEM (transmission electron microscope) photograph showing the crystal structure of silicon fine particles after the pulverization 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] 1 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. 10 is an explanatory diagram schematically illustrating the 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] 10 is a graph showing the difference in maximum hydrogen generation rate due to the difference in pH value in Example 6. [Figure 13] FIG. 10 is an XPS spectrum of silicon fine particles after the hydrogen generation reaction in Example 6. [Figure 14] 10 is a graph showing the amount of hydrogen generated per 1 g 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 Stirrer 58 Centrifuge 60 Hydrophilic treatment tank 70 Hydrogen generation unit 72 Reaction Tank 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 INVENTION

[0019] Embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this description, common parts are designated by common reference numerals throughout the drawings unless otherwise specified. In addition, in the drawings, elements of each embodiment are not necessarily shown to scale. In addition, some reference numerals may be omitted to make each drawing easier to understand.

[0020] 1. Hydrogen production method First Embodiment The hydrogen production method of this embodiment includes various steps using silicon chips or silicon polishing chips (hereinafter also referred to as "silicon waste"), which are usually discarded as waste in the silicon cutting process in the production of semiconductor products, as an example of a starting material. Silicon waste also includes fine chips obtained by pulverizing 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 primarily intended to remove 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 using a ball mill. Here, the ball mill of this embodiment is a grinder that uses steel balls, magnetic balls, boulders, and the like as grinding media. Furthermore, an example of the first liquid in this embodiment described above is acetone.

[0022] Thereafter, the silicon waste material that has undergone the cleaning process is passed through a filter, and the 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. Furthermore, since a ball mill is used in the cleaning process of this embodiment, it is possible to significantly improve 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 microparticles with a crystallite diameter of 100 nm or less. Note that, as long as the crystallite diameter of the silicon microparticles is 100 nm or less, even if the aggregate particle size distribution of the silicon microparticles is in the range of 100 nm to 5 μm, good effects, i.e., effects equivalent to those 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. Further, a coarse pulverization process is performed using a ball mill. The coarsely pulverized silicon waste is passed through a filter to remove relatively coarse particles, and the remaining silicon waste is then finely pulverized using a bead mill. Then, the second liquid is removed using a rotary evaporator, and silicon microparticles are obtained as the result of the fine pulverization process.

[0024] The pulverization step (S2) of this embodiment makes it possible to form silicon microparticles that are amorphous, have a crystallite size distribution in the 100 nm range, and have hydrophilic surfaces. The pulverization step (S2) can be performed using any one of a group of pulverizers, including a bead mill, a ball mill, a jet mill, and an impact wave pulverizer, or a combination of these.

[0025] (3) Hydrogen generation process In the subsequent hydrogen generation step (S3), hydrogen is generated by contacting and / or dispersing the silicon fine particles obtained in the crushing step (S2) with water or an aqueous solution. The water used in this hydrogen generation step does not necessarily have to be pure water; it may be water containing electrolytes or organic substances, such as ordinary tap water or industrial water. The type of aqueous solution used in this embodiment is also not particularly limited. The hydrogen ion concentration exponent (pH value) of the aqueous solution is not particularly limited, but a pH value of 10 or higher is preferable. This is because, according to the analysis results of the inventors, the higher the pH value, the faster the hydrogen production rate and the shorter the completion time of the hydrogen production reaction. Therefore, when it is desired to continuously supply a small amount of hydrogen for a long period of time, intentionally lowering the pH value of the aqueous solution is a preferred embodiment. On the other hand, when it is desired to temporarily supply a large amount of hydrogen, setting the pH value of the aqueous solution high makes it possible to produce hydrogen according to the needs of various industries or users of various devices.

[0026] The temperature of the water used in the hydrogen generation step can also be set arbitrarily to obtain a desired hydrogen production rate. Furthermore, the means for contacting and / or dispersing the silicon microparticles in water or an aqueous solution can employ stirring, water flow, shaking, etc., as needed. Stirring, etc., promotes the hydrogen production reaction, thereby increasing the rate at which hydrogen is produced.

[0027] As described above, the hydrogen production method of this embodiment makes it possible to reliably produce a practical amount of hydrogen by using silicon chips or silicon polishing dust, which are usually considered waste, as the starting material, for example, from silicon cutting processing in the production process of semiconductor products. Therefore, the effective use of silicon chips or silicon polishing dust, 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, it is noteworthy that this embodiment makes it possible to produce large amounts of hydrogen at a practical level without undergoing 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 the steps of the hydrogen production method of this embodiment. As shown in FIG. 2, the hydrogen production method of this 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 removal step (T3), the silicon microparticles obtained in the above-mentioned pulverization step (T2) are brought into contact with an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution. In this embodiment, the silicon microparticles obtained in the pulverization step (T2) and having a crystallite size distribution of 100 nm or less are immersed in an aqueous hydrofluoric acid solution or an aqueous ammonium fluoride solution. This brings the silicon microparticles into contact with and / or disperses them in the aqueous hydrofluoric acid solution or the aqueous ammonium fluoride solution. Thereafter, the silicon microparticles and the aqueous hydrofluoric acid solution are separated using a centrifuge. The silicon microparticles are then immersed in a third liquid such as an ethanol solution. The third liquid is then removed to obtain silicon microparticles for hydrogen production.

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

[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 the aforementioned aqueous solution to generate hydrogen.

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

[0036] <Third embodiment> This embodiment is the same as the second embodiment except that a hydrophilization treatment step for making the surfaces of silicon microparticles hydrophilic is added after the surface oxide film removal step in the second embodiment.

[0037] 3 is a diagram showing the steps of the hydrogen production method of this embodiment. As shown in FIG. 3, the hydrogen production method of this 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 step (U4) (5) Hydrogen generation process (U5)

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

[0039] The hydrophilization treatment step (U4) will be described below. In the hydrophilic treatment step (U4) of this embodiment, the surfaces of the silicon microparticles are treated with a surfactant or nitric acid after the surface oxide film removal step. When using 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 microparticles are brought into contact with and / or dispersed in a fourth liquid such as propanol, and then the surfactant or nitric acid is added and the mixture is stirred. Furthermore, in this embodiment, after stirring, the fourth solution is removed using a rotary evaporator.

[0040] In the subsequent hydrogen generation step (U5), the hydrophilic treated silicon fine particles are brought into contact with water or an aqueous solution and / or dispersed in the aforementioned aqueous solution to generate hydrogen.

[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 microparticles, thereby highly reliably suppressing the floating of the silicon microparticles to the water surface, a phenomenon unique to microparticles. As a result, the silicon microparticles become more compatible with water or an aqueous solution, increasing the contact area between the silicon microparticles and the water or aqueous solution, 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 chips or silicon polishing dust, chemically treated silicon microparticles (typically, oxide film removal treatment using a hydrofluoric acid aqueous solution or an ammonium fluoride aqueous solution in the second embodiment, or 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 schematically shows the 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. Note that the hydrogen production device 100 of this embodiment can also be considered an assembly of devices (processing units) that perform multiple processes described below, and therefore the hydrogen production device 100 may also be called a hydrogen production system.

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

[0045] In the crusher 10, first, the silicon waste material 1, which is the material to be processed, and the second liquid of the first embodiment are fed into the crusher 10 through 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 produce waste liquid. Next, the residue (silicon waste material 1) is dried in the drying chamber 30, and is fed again through the inlet 11 together with the second liquid to be crushed in the crusher 10. Specifically, after coarse crushing is performed using a ball mill or the like, the crushed material is passed through the filter 15 together with the second liquid to remove coarse particles. Next, fine crushing is performed using a bead mill or the like. Next, the crushed 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 unit 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. If the surface oxide film of the silicon fine particles 2 is not removed, the silicon fine particles 2 are sent to a hydrogen generation unit 70, which will be described later.

[0047] A hydrophilic treatment tank 60, which is an example of a hydrophilic treatment unit of this embodiment, is equipped with a stirrer 67, and brings silicon fine particles 3 before or after removal of a surface oxide film into contact with and / or is dispersed in a fourth liquid 65 to which a surfactant or nitric acid has been added. If the silicon fine particles 2 are not subjected to hydrophilic treatment, the silicon fine particles before or after removal of a surface oxide film are sent to a hydrogen generating unit 70, which will be described later. In the hydrophilic treatment of this embodiment, it is possible to subject silicon fine particles in a state before removal of a surface oxide film to hydrophilic treatment. However, from the viewpoint of achieving hydrophilic treatment of the silicon fine particles with a higher degree of accuracy, it is preferable to subject the silicon fine particles after removal of a surface oxide film to 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, hydrogen 5 is generated by contacting and / or dispersing at least one selected from the group consisting of silicon microparticles 2, silicon microparticles 3 after surface oxide film removal, and silicon microparticles 4 after hydrophilization with water or an aqueous solution 75. The generated hydrogen 5 is sent via the transfer pipe 79 into the water 85 in the water tank 80. Then, the hydrogen 5 collected by the hydrogen collector 87 by, for example, a water displacement method is collected via the hydrogen pipe 89 in a hydrogen storage container 90.

[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 chips or silicon polishing dust as starting materials, which are usually discarded as waste, for example, from silicon cutting processes in the production process of semiconductor products.

[0050] <Example> In the following, examples will be given to explain the above-described embodiment in more detail, but the above-described embodiment is not limited to these examples. Examples 1 to 5 below show the results of hydrogen production tests conducted 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 cleaning step and the crushing step, the hydrogen generation step was carried out.

[0052] (1) Cleaning process 200g (grams) of silicon chips were added to 200mL (milliliters, also written as "ml") of acetone and dispersed in a ball mill for 1 hour. A Universal Ball Mill manufactured by Masuda was used as the ball mill. Alumina beads with particle sizes of 10mm (millimeters) and 20mm (millimeters) were used. The liquid was then removed by suction filtration, and the residue was dried in a dryer set to 40°C.

[0053] (2) Crushing process Next, 15 g of the washed silicon sludge was weighed into a plastic container, and 285 g of 2-propanol was added. Next, alumina balls were placed in a ball mill, and coarse pulverization was carried out for 2 hours at a peripheral speed of 80 rpm. The ball mill used in this example was a Universal ball mill manufactured by Masuda Corporation. The balls used in this example were alumina balls with particle sizes of 10 mm and 20 mm. The product obtained by the milling 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 a Star Mill LMZ015 manufactured by Ashizawa Feinting Co., Ltd. The beads used in this example were 456 g of zirconia beads with a particle size of 0.5 mm. Next, the finely pulverized material was collected, and the 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 was 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 using the hydrogen production device 100 based on the hydrogen production method of the second embodiment. Therefore, the same process as in Example 1 was carried out, except that a surface oxide film removal process was added after the pulverization process in Example 1. Specifically, hydrogen was produced in the following order: cleaning process, pulverization process, surface oxide film removal process, and hydrogen generation process. The surface oxide film removal process was as follows.

[0057] In the surface oxide film removal process, the silicon microparticles obtained in the pulverization process of this example were dispersed in a 50% aqueous solution of hydrofluoric acid, and then the silicon microparticles and the hydrofluoric acid solution were separated using a centrifuge. The resulting silicon microparticles were then immersed in an ethanol solution. The ethanol solution was then removed to obtain silicon microparticles for hydrogen production.

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

[0059] Specifically, the washing process, pulverization process, and surface oxide film removal process were carried out under the same conditions as in Example 2. Furthermore, in the treatment using a surfactant in the hydrophilization treatment process, the concentration of silicon microparticles was adjusted to 5 wt% in 2-propanol, which was the fourth liquid in the third embodiment. Then, 0.05% of the 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. The 2-propanol was then removed using 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 the mixture was immersed at room temperature.

[0061] Example 4 In Example 4, the hydrogen production device 100 was used in the hydrogen production method of the second embodiment, and the aqueous solution used in the hydrogen generation process was a buffer solution consisting of 0.1 mol / L sodium bicarbonate and 0.1 mol / L sodium carbonate, and the pH value of the aqueous solution was adjusted to 10, in the same manner as in Example 2, except that 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 same method as Example 2 was used, 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 example> 1. Crystal structure analysis using cross-sectional TEM images FIG. 5 is a cross-sectional TEM (transmission electron microscope) photograph showing the crystalline 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 particles of irregular shape. On the other hand, 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 were crystalline.

[0064] 2. Crystallite size distribution of silicon microparticles using X-ray diffraction Figure 6 shows the results of analyzing the crystallite size distribution of silicon microparticles after the pulverization process using X-ray diffraction. In the graph shown in Figure 6, the horizontal axis represents crystallite size (nm) and the vertical axis represents frequency. The solid line represents the crystallite size distribution based on number distribution, and the dashed line represents the crystallite size distribution based on 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. These results confirmed that the silicon microparticles obtained after the pulverization process were so-called silicon nanoparticles, with crystallite diameters distributed in the range of 100 nm or less, particularly 50 nm or less, by 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 removal 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 excellent result was obtained.

[0068] Furthermore, in Example 3, 116.7 mL of hydrogen was obtained after immersion for 9,805 minutes (i.e., approximately 163 hours), resulting in even better results 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 1,000 minutes had elapsed was significantly 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 1,000 minutes had elapsed was extremely fast. Therefore, Figure 7 demonstrates the remarkable effect of the surface oxide film removal step or surface oxide film removal section.

[0069] Next, the results of Examples 4 and 5, in which silicon microparticles 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 in 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 represents the immersion time (minutes), and the vertical axis of Figs. 8 and 9 represents the amount of hydrogen generated (mL / g) per 1 g of silicon microparticles for hydrogen production.

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

[0071] Furthermore, as shown in the results of Example 5 in Figure 9, when the pH value of the aqueous solution in the hydrogen generation step was set to 13, the amount of hydrogen generated rapidly increased immediately after the silicon microparticles and the aqueous solution were reacted. More specifically, after 10 minutes, approximately 470 ml of hydrogen was generated per gram of silicon microparticles for hydrogen production, and after 30 minutes, approximately 590 ml of hydrogen was generated per gram of silicon microparticles for hydrogen production. In addition, in Example 4, where the pH value of the aqueous solution in the hydrogen generation step was 10, after 13 minutes, approximately 3.5 ml of hydrogen was generated per gram of silicon microparticles for hydrogen production, and after 30 minutes, approximately 15 ml of hydrogen was generated per gram of silicon microparticles for hydrogen production. In Example 4, the reaction was slower than in Example 5, but a larger amount of hydrogen was 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., by increasing the pH value to 10 or higher), the reaction rapidly promotes hydrogen production in a short period of time, rather than the gradual hydrogen production reaction over a long period of time shown in Examples 1 to 3. Therefore, increasing the pH value of the aqueous solution in the hydrogen generation step to 10 or higher (14 or lower) is a very suitable embodiment from the perspective of obtaining a larger amount of hydrogen more quickly.

[0073] The hydrogen production method and hydrogen production apparatus disclosed in each of the above-described embodiments are expected to be widely used in technical fields requiring hydrogen, such as fuel cells. Furthermore, what is interesting about the hydrogen production method and hydrogen production apparatus of each of the above-described embodiments is that they utilize, as starting materials, silicon chips or silicon polishing waste, which are typically discarded as waste during silicon cutting processing in the production of semiconductor products, for example. Therefore, the cost per gram of produced hydrogen is significantly lower than that of hydrogen obtained by conventional hydrogen production methods. This not only contributes to environmental protection through the effective use of waste materials, but also significantly improves the economic efficiency of hydrogen production. Furthermore, the hydrogen production method and hydrogen production apparatus of each of the above-described embodiments, which do not require complex devices, facilities, or systems, or complex processes, can significantly contribute to increasing industrial productivity.

[0074] <Other embodiments> In the fourth embodiment described above, hydrogen is generated by contacting and / or dispersing at least one selected from the group consisting of silicon microparticles 2, silicon microparticles 3 after surface oxide film removal, and silicon microparticles 4 after hydrophilization in the reaction tank 72 of the hydrogen generation unit 70 with water or an aqueous solution 75. However, the reaction may reach an equilibrium state over time, resulting in saturation of the amount or rate of hydrogen generation. Therefore, as a modification of the fourth embodiment to solve such problems, the configuration of a hydrogen production device 200 shown in FIG. 10 is disclosed, along with Example 6.

[0075] 10 is an explanatory diagram schematically illustrating the configuration of a hydrogen production device 200 according to a modification 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 hydrogen production device 200 includes an additional hydrogen generation unit 270 in which silicon microparticles in the reaction vessel 72 whose hydrogen generation amount or hydrogen generation rate has once reached or is about to reach saturation are removed from 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 unit in the hydrogen production device 200 to remove oxide films from the silicon microparticle surfaces (additional surface oxide film removal step), and then the silicon microparticles from which the oxide film has been removed are returned to the reaction vessel 72 to generate hydrogen (additional hydrogen generation step). Therefore, redundant explanations will be omitted.

[0076] When the hydrogen production apparatus 200 shown in Fig. 10 is employed, even if the amount or rate of hydrogen generation becomes saturated or nearly saturated once the reaction in the reaction vessel 72 reaches an equilibrium state, the silicon fine particles will regain 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-described embodiments regenerates or restores 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 significantly contribute to reducing the cost of hydrogen production.

[0077] Unlike the hydrogen production apparatus 200, another embodiment 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 connects the reaction tank 72 to the surface oxide film removal tank 50 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 embodiment that can be adopted is to perform a hydrophilization treatment step (additional hydrophilization treatment step) after the additional surface oxide film removal step.

[0078] Additionally, in the above-described 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-described embodiment is not limited to this. 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 step of Example 6, 0.86 g of silicon fine particles formed by pulverizing p-type silicon chips using ZiO2 beads in a bead mill in the same manner as in Example 5 were immersed in an aqueous solution (0.1 mol / L potassium hydroxide aqueous 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 fixed amount (0.86 g) of silicon particles was immersed in each aqueous solution at room temperature, and the graph of the amount of hydrogen generated versus reaction time was obtained, as shown in Figure 11. For example, at a pH of 13.9, it was found that the amount of hydrogen generated per gram of silicon 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 at a pH of 13.9, the amount of hydrogen generated exceeded 1000 mL per gram of silicon particles in just approximately 10 minutes. Note that 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 depending on the pH value in Example 6. The values in FIG. 12 indicate the maximum hydrogen generation rate per minute and per gram for the four types of aqueous solutions described above when the pH value shown in FIG. 11 was 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. Furthermore, by utilizing the dependence of the hydrogen generation rate on the pH value of the solution, it is possible to control the hydrogen generation rate. Note that, even at this stage, the aforementioned additional surface oxide film removal process and additional hydrogen generation process were not performed.

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

[0083] As a result, as shown in Figure 14, multiple Si atoms belonging to silicon (Si) and silicon dioxide (SiO2) were observed. 2pA peak was observed. Therefore, it became clear that a silicon dioxide (SiO2) film was formed on the surface of the silicon microparticles where the reaction had reached or nearly reached equilibrium. Furthermore, based on the peak intensity ratio between (Si) and (SiO2) shown in Figure 14, it was concluded that an SiO2 film with a thickness of approximately 5 nm had formed on the surface of the silicon microparticles.

[0084] Therefore, in Example 6, silicon fine particles for which the reaction had reached or nearly reached equilibrium were subjected to a step of removing the SiO2 film (additional surface oxide film removal step) by contacting them with a 5% HF aqueous solution. After that, the silicon fine particles were again immersed in the above-mentioned aqueous solution 75 with a pH of 13.9. As a result, an additional 470 ml / g (per initial 1 g) of hydrogen was generated 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 the additional surface oxide film removal step and the additional hydrogen generation step was approximately 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 performing the additional surface oxide film removal step and the additional hydrogen generation step is very useful as a means for generating extremely large amounts of hydrogen.

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

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

[0088] When silicon microparticles are immersed in the above-mentioned aqueous solution 75 to which ammonia has been added, the silicon microparticles may float on the surface of the aqueous solution unless any particular prior treatment is performed. Therefore, in Example 7, the silicon microparticles were brought into contact 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 microparticles to settle to the bottom of the reaction tank 72. On the other hand, experiments were conducted with the aqueous solution 75 to which sodium hydroxide has been added by contacting and / or dispersing the silicon microparticles in the aqueous solution 75 in the same manner as in the case of potassium hydroxide.

[0089] 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 step of each of the above-described embodiments, adjusting the rate and / or amount of hydrogen generation by changing the pH value of the water or aqueous solution 75 is a very suitable mode that can be adopted. Similarly, it is a very suitable mode that the hydrogen generation unit 70 or the additional hydrogen generation unit 270 in the hydrogen production device 100 or 200 further includes an adjustment unit that adjusts the rate and / or amount of hydrogen generation by changing the pH value of the water or aqueous solution 75.

[0090] For example, the adjusting unit may be an apparatus equipped with a means for dripping the above-mentioned water or each aqueous solution (such as an aqueous solution with added NaOH, an aqueous solution with added KOH, or an aqueous solution with added NH3) 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 the dripping means receives feedback of the measurement result from the measuring unit that measures the pH value of water or each aqueous solution 75, and 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, based on the results of the above-mentioned examples, a pH value of 10 or higher, more preferably 11.9 or higher, 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 carried out using an aqueous hydrofluoric acid solution. However, even if the treatment is carried out 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 the above-mentioned examples.

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

[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 the 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] Furthermore, as explained in Example 6 above, 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 aqueous solution, and silicic acid is produced on the surface of the silicon fine particles. The silicic acid is then oxidized to silicon dioxide (SiO), which weakens or terminates the hydrogen generation reaction over time. Therefore, in order to suppress the formation of silicon dioxide (SiO) on the surface of the silicon fine particles and 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 aqueous solution in the hydrogen generation process, thereby continuing the hydrogen generation reaction upon contact with the water or aqueous solution.

[0096] Furthermore, in each of the above-described embodiments, the hydrogen generating unit 70 or the additional hydrogen generating unit 270 is employed, which generates hydrogen by contacting the formed silicon microparticles (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 microparticles with water or an aqueous solution 75 is not limited to the above-described method. For example, another possible embodiment is to generate hydrogen by contacting the formed silicon microparticles with water or an aqueous solution 75 while they are fixed to the surface of a solid (e.g., a sponge). For example, if the solid is made of a material that can absorb and retain liquid to a certain extent, such as a sponge, impregnating the solid with a hydrofluoric acid aqueous solution or an ammonium fluoride aqueous solution increases the likelihood of suppressing the generation of silicon dioxide (SiO2) on the silicon microparticles.

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

Claims

1. a crushing unit for crushing silicon chips or silicon polishing waste to form silicon fine particles; a hydrogen generating unit that generates hydrogen by bringing the silicon fine particles into contact with water or an aqueous solution and / or dispersing them in the water or the aqueous solution; Equipped with Hydrogen production equipment.

2. a surface oxide film removing unit that brings the silicon fine particles obtained by the pulverizing unit into contact with hydrofluoric acid or an ammonium fluoride aqueous solution, the hydrogen generating unit generates hydrogen by bringing the silicon fine particles, which have been brought into contact with the hydrofluoric acid or the ammonium fluoride aqueous solution, into contact with water or an aqueous solution and / or dispersing the silicon fine particles in the water or the aqueous solution. The hydrogen production device according to claim 1 .

3. a hydrophilization treatment section that hydrophilizes the surfaces of the silicon fine particles that have been brought into contact with the hydrofluoric acid or the ammonium fluoride aqueous solution, The hydrophilic treatment unit brings a surfactant or nitric acid into contact with the surfaces of the silicon microparticles. The hydrogen production device according to claim 2 .

4. an additional surface oxide film removal unit that contacts the silicon fine particles discharged from the hydrogen generation unit with hydrofluoric acid or an aqueous solution of ammonium fluoride again; The method further includes an additional hydrogen generating unit that generates hydrogen by contacting and / or dispersing the silicon fine particles that have been contacted again with the hydrofluoric acid or the ammonium fluoride aqueous solution by the additional surface oxide film removing unit in water or an aqueous solution. The hydrogen production device according to any one of claims 1 to 3.

5. The hydrogen generating unit further includes an adjusting unit that adjusts the hydrogen generation rate and / or the amount of hydrogen generated by changing the hydrogen ion concentration exponent (pH) of the water or the aqueous solution. The hydrogen production device according to any one of claims 1 to 4.

6. a crushing step of crushing silicon chips or silicon polishing waste to form silicon fine particles; a hydrogen generating step of generating hydrogen by bringing the silicon fine particles into contact with water or an aqueous solution and / or dispersing the silicon fine particles in the water or the aqueous solution; Including, Hydrogen production methods.

7. a surface oxide film removal step of contacting the silicon fine particles obtained by the pulverization step with hydrofluoric acid or an ammonium fluoride aqueous solution before the hydrogen generation step; The hydrogen generating step generates hydrogen by contacting and / or dispersing the silicon fine particles, which have been contacted with the hydrofluoric acid or the ammonium fluoride aqueous solution, in water or an aqueous solution. The method for producing hydrogen according to claim 6.

8. The method further includes a hydrophilization treatment step of hydrophilizing the surfaces of the silicon fine particles that have been contacted with the hydrofluoric acid or ammonium fluoride aqueous solution before the hydrogen generation step, The method for producing hydrogen according to claim 7.

9. an additional surface oxide film removal step of contacting the silicon fine particles with hydrofluoric acid or an ammonium fluoride aqueous solution again during or after the hydrogen generation step; and an additional hydrogen generation step of generating hydrogen by contacting and / or dispersing the silicon fine particles in the water or the aqueous solution again after the additional surface oxide film removal step. The method for producing hydrogen according to any one of claims 6 to 8.

10. In the hydrogen generation step, the hydrogen generation rate and / or the amount of hydrogen generated is adjusted by changing the hydrogen ion concentration exponent (pH) of the water or the aqueous solution. The method for producing hydrogen according to any one of claims 6 to 9.

11. The hydrophilization treatment step includes contacting the surfaces of the silicon fine particles with a surfactant or nitric acid. The method for producing hydrogen according to claim 8.

12. The crystallite diameter of the silicon fine particles is 100 nm or less. The method for producing hydrogen according to any one of claims 6 to 11.

13. The pH value of the aqueous solution in the hydrogen generation step is 10 or more. The method for producing hydrogen according to any one of claims 6 to 12.

14. The shape is amorphous, the crystallite size is 100 nm or less, and the surface is hydrophilic. Microscopic silicon particles for hydrogen production.

15. The surface is hydrophilic, The silicon microparticles for hydrogen production according to claim 14.

16. The silicon fine particles include those obtained by chemically treating silicon fine particles formed by pulverizing silicon chips or silicon polishing dust. The silicon microparticles for hydrogen production according to claim 14 or 15.

17. A crushing step of crushing silicon chips or silicon polishing waste to form silicon fine particles, A method for producing silicon microparticles for hydrogen production.

18. The method further includes a surface oxide film removal step of contacting the silicon fine particles obtained by the pulverization step with hydrofluoric acid or an ammonium fluoride aqueous solution. The method for producing silicon microparticles for hydrogen production according to claim 17.

19. The method further includes a hydrophilization treatment step of hydrophilizing the surfaces of the silicon fine particles that have been brought into contact with the hydrofluoric acid or the ammonium fluoride aqueous solution. The method for producing silicon microparticles for hydrogen production according to claim 18.

20. The hydrophilization treatment step includes contacting the surfaces of the silicon fine particles with a surfactant or nitric acid. The method for producing silicon microparticles for hydrogen production according to claim 19.

21. The silicon fine particles formed by pulverizing the silicon chips or the silicon polishing waste are chemically treated to form silicon fine particles. The method for producing silicon fine particles for hydrogen production according to any one of claims 17 to 20.

22. Produced by the method for producing silicon fine particles for hydrogen production according to any one of claims 17 to 21. Microscopic silicon particles for hydrogen production.

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