Iron-based powder for hydrogen production and hydrogen producing agent

Abstract

To provide an iron-based powder capable of generating hydrogen with high efficiency.SOLUTION: An iron-based powder for hydrogen production is provided, wherein, among the diffraction peaks in X-ray diffraction, the lattice spacing derived from the diffraction intensity curve corresponding to the (110) plane of the α-Fe crystal is in the range of 2.000Å or more and 2.100Å or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an iron-based powder for producing hydrogen. [Background technology]

[0002] In recent years, the development of a highly efficient method for producing hydrogen for industrial use has been investigated.

[0003] For example, Patent Document 1 discloses a method for producing hydrogen by pulverizing and mixing inorganic substances such as silicon and aluminum with a solvent using a planetary ball mill.

[0004] Patent Document 2 discloses a method for producing hydrogen by reacting silicon powder, to which residual stress has been previously imparted, with water. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-47789 A [Patent Document 2] JP 2021-134107 A Summary of the Invention [Problem to be solved by the invention]

[0006] The method proposed in the above Patent Document 1 is a method for producing hydrogen using a mechanochemical reaction. However, this method requires the hydrogen generation reaction to proceed while applying mechanical energy to the metal material using a planetary ball mill equipped with a reaction vessel. This makes the device complicated.

[0007] In contrast, according to the method proposed in the above Patent Document 2, hydrogen can be produced simply by stirring silicon powder and a solvent. However, because hydroxide ions are required for the reaction between silicon and water, this method can only be used when the pH is relatively high. As such, there are restrictions on the reaction conditions for hydrogen generation using silicon powder, so there has been a demand for producing hydrogen using a reaction other than the reaction between silicon and water.

[0008] A method for producing hydrogen by reacting iron with water using an iron-based powder has been known as a simpler and more practical method for producing hydrogen. However, the efficiency of hydrogen generation is still not sufficient, and there is a need to further improve the efficiency.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide an iron-based powder capable of generating hydrogen with high efficiency. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the inventors have focused on the lattice spacing determined from a diffraction intensity curve corresponding to the (110) diffraction plane of an α-Fe crystal, which indicates the degree of distortion of the crystal structure of an iron-based powder, and have conducted extensive research.

[0011] As a result, they discovered that by setting the lattice spacing within a certain range, it is possible to manufacture an iron-based powder that realizes highly efficient hydrogen generation.

[0012] The present invention is based on the above findings, and has the following gist and configuration.

[0013] 1. Iron-based powder for hydrogen production, in which the lattice spacing calculated from the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal among the X-ray diffraction peaks is in the range of 2.000 Å to 2.100 Å.

[0014] 2. A hydrogen production agent using the iron-based powder for hydrogen production described in 1 above. Effect of the Invention

[0015] According to the present invention, it is possible to provide an iron-based powder capable of generating hydrogen with high efficiency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] First, the mechanism of hydrogen generation using iron-based powder will be described.

[0017] There are two types of corrosion reactions for iron: oxygen consumption corrosion, represented by the following formulas (1) and (2), and hydrogen evolution corrosion, represented by the following formulas (3) and (4). Oxygen-consuming corrosion: Fe → Fe 2+ +2e - … (1) H 2 O+1 / 2O 2 +2e - →2OH - … (2) Hydrogen-evolving corrosion: Fe → Fe 2+ +2e - … (3) 2H + +2e - →H 2 … (4)

[0018] In a typical corrosive environment under neutral conditions, oxygen-consuming corrosion progresses as shown in the above formulas (1) and (2). In this case, hydroxide ions produced by the reduction of oxygen react with iron ions produced by the oxidation of iron to produce iron hydroxide, i.e., rust, but no hydrogen is produced.

[0019] On the other hand, when a sufficient number of hydrogen ions are present in water, the hydrogen evolution corrosion represented by the above formulas (3) and (4) progresses.

[0020] Therefore, in order to produce hydrogen, it is necessary to cause the hydrogen-generating corrosion of the above formulas (3) and (4) in the iron-based powder.

[0021] Here, crevice corrosion is a typical case in which hydrogen evolution corrosion of the above formulas (3) and (4) occurs in general steel products. When a steel product has a gap and moisture is present in the gap, oxygen consumption corrosion of the above formulas (1) and (2) progresses inside the gap at first, consuming dissolved oxygen. Meanwhile, the outside of the gap is in contact with the atmosphere, so the dissolved oxygen concentration remains high. As a result, an oxygen concentration difference is formed between the inside and outside of the gap.

[0022] Furthermore, inside the gap, iron ions produced by corrosion are hydrolyzed, and hydrogen ions accumulate.

[0023] In this way, a decrease in the oxygen concentration and an increase in the hydrogen ion concentration occur inside the gap, resulting in hydrogen evolution corrosion as shown in the above formulas (3) and (4) instead of the oxygen consumption corrosion as shown in the above formulas (1) and (2).

[0024] It is believed that hydrogen generation by such a mechanism also occurs in iron-based powders. That is, when moisture penetrates into the pores of the iron-based powder, an oxygen concentration difference is formed in the moisture. Furthermore, hydrogen ions accumulate in the low oxygen concentration region due to hydrolysis of iron ions generated by corrosion. As a result, hydrogen generation corrosion of the above formulas (3) and (4) progresses in the pores, and hydrogen is generated.

[0025] Here, if the reactivity of metallic iron contained in the iron-based powder is low, the oxygen consumption corrosion and hydrogen generation corrosion described above do not progress easily, resulting in poor hydrogen generation efficiency. Therefore, in the present invention, the reactivity of metallic iron is increased, making it more susceptible to oxidation, thereby achieving excellent hydrogen generation efficiency.

[0026] [Iron-based powder] The iron-based powder according to the present invention will be specifically described below. In the following description, "%" refers to "mass %" unless otherwise specified. In the following description, "iron-based powder" refers to a metal powder containing 50 mass % or more of Fe.

[0027] The iron-based powder according to the present invention may be, for example, iron powder or iron-based alloy powder. The term "iron-based alloy powder" refers to an alloy powder containing 50 mass % or more of Fe. The term "iron powder" refers to a powder consisting of Fe and unavoidable impurities, and is generally referred to as "pure iron powder" in this technical field.

[0028] The composition of the iron-based powder is not particularly limited. However, when the iron-based powder is an iron-based alloy powder, it may further contain elements such as C, S, O, N, Si, Mn, P, S, Cr, Cu, Sn, Ni, Mo, Zn, As, Sb, and Bi in addition to Fe. When the iron-based powder is an iron powder, it may contain elements such as C, S, O, N, Si, Mn, P, S, Cr, Cu, Sn, Ni, Mo, Zn, As, Sb, and Bi as inevitable impurities.

[0029] The metallic iron content of the iron-based powder is not particularly limited. However, if the metallic iron content is 50% or more, the amount of iron ions eluted can be increased, so that the corrosion reaction proceeds more and the efficiency of hydrogen generation can be further increased. Therefore, it is preferable that the metallic iron content is 50% or more. The upper limit of the metallic iron content is not particularly limited and may be 100%. The metallic iron content is measured using the "Method for determining metallic iron" specified in JIS A 5011-2.

[0030] The iron-based powder can be produced by an atomization method, a pulverization method, or an oxide reduction method, as described below. The atomization method can be a water atomization method or a gas atomization method. That is, the iron-based powder can be an atomized iron-based powder, a pulverized iron-based powder, or a reduced iron-based powder. The atomized iron-based powder can be a water atomized iron-based powder or a gas atomized iron-based powder.

[0031] In the present invention, from the viewpoint of hydrogen generation efficiency, the lattice spacing determined from the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal among the diffraction peaks of the X-ray diffraction of the iron-based powder is set to be in the range of 2.000 Å to 2.100 Å.

[0032] When a solid substance is subjected to stress such as crushing, impact, or friction, its crystalline properties change, and in particular, lattice defects in the crystal structure increase. These lattice defects then cause a mechanochemical effect, making the substance chemically active.

[0033] Here, in the case of an iron-based powder, when mechanical energy is applied by pulverization using a pulverizer or mixing using a mixer, distortion occurs in the crystal structure of the metallic iron contained in the iron-based powder, and the reactivity of the corrosion reaction is improved. It is presumed that the reason why the iron-based powder for hydrogen production of the present invention has excellent hydrogen generation efficiency is due to the high reactivity caused by the distortion of the crystal structure of the metallic iron.

[0034] The distortion of the crystal structure can be evaluated from the value of the lattice spacing obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal among the diffraction peaks of the X-ray diffraction of the iron-based powder.

[0035] When compressive stress is applied to α-Fe crystals by mechanical energy, uniform strain is generated in the crystal lattice of the α-Fe crystals, and the lattice spacing increases. If the strain is small, sufficient hydrogen generation efficiency cannot be obtained. For the above reasons, the lattice spacing of the iron-based powder is set to 2.000 Å or more, preferably 2.010 Å or more, and more preferably 2.020 Å or more.

[0036] However, if the distortion becomes excessively large and the lattice spacing exceeds 2.100 Å, the iron-based powder becomes easily oxidized, and the iron-based powder reacts with oxygen in the air to generate an oxide film on the surface of the iron-based powder. This reduces the reactivity with water, and hydrogen generation becomes difficult. Therefore, the lattice spacing of the iron-based powder is set to 2.100 Å or less.

[0037] The lattice spacing is determined by X-ray diffraction measurement, specifically as follows.

[0038] First, an X-ray diffraction measurement is performed on the iron-based powder to be measured, and a diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal in the iron-based powder is obtained from among the diffraction peaks. The X-ray diffraction measurement is performed using Cu-Kα rays (wavelength 1.54178 Å) as characteristic X-rays, with a scanning speed of 4° / min and a measurement angle range of 35° to 55°. The lattice spacing is calculated by applying the diffraction angle of the obtained diffraction intensity curve and the wavelength of the characteristic X-rays to Bragg's law shown in the following formula (5). 2d sinθ=n λ (5) d: Lattice spacing (Å) θ: Diffraction angle (°) n: natural number λ: wavelength of X-rays (Å)

[0039] The particle size of the iron-based powder is not particularly limited as long as it is easy to handle. 50 is preferably 1 mm or less, more preferably 400 μm or less, and further preferably 200 μm or less. 50 There is no particular restriction on the lower limit of the median diameter D. However, the larger the particle size, the easier it is to handle. 50 is preferably 5 μm or more, more preferably 50 μm or more.

[0040] The median diameter D 50 is the median particle size calculated from the volume-based particle size distribution, and is measured using a laser diffraction / scattering method. The specific measurement method is as follows.

[0041] The iron-based powder to be measured is put into a solvent (e.g., ethanol) and dispersed by ultrasonic vibration for 30 seconds or more, and the volume-based particle size distribution of the iron-based powder is measured by a laser diffraction particle size distribution analyzer using the laser diffraction / scattering method.

[0042] The cumulative particle size distribution is calculated from the obtained particle size distribution, and the median value (the particle size of the particle that is 50% of the total volume of all particles) is taken as the median diameter D 50 is used as a representative value of the particle size of the iron-based powder.

[0043] The specific surface area of ​​the iron-based powder is not particularly limited. However, the smaller the specific surface area, the less likely the iron-based powder is to be oxidized, and therefore the generation of an oxide film due to the reaction between the iron-based powder and oxygen in the air can be prevented. Therefore, the reactivity with water can be maintained, and hydrogen can be generated with higher efficiency. Therefore, it is preferable to set the specific surface area to 1.00 m 2 The lower limit of the specific surface area is not particularly limited, but in order to facilitate contact with water and further increase the efficiency of hydrogen generation, it is preferably 0.01 m 2 It is preferable that the molecular weight is 1 / g or more.

[0044] The specific surface area is measured by the BET method, specifically as follows.

[0045] First, 2 g of the iron-based powder to be measured is placed in the measurement cell and subjected to a reduced pressure degassing treatment at 150°C for 30 minutes. After that, the sample and the measurement cell are cooled to -196°C, and nitrogen is introduced into the measurement cell to adsorb nitrogen to the sample. The specific surface area is calculated from the relationship between the nitrogen partial pressure and the amount of adsorption.

[0046] The pore shape of the iron-based powder is not particularly limited, and the iron-based powder may have pores of a wide range of sizes (volume, diameter) depending on the manufacturing conditions, etc. However, pores with a diameter of 3 nm to 500 μm contribute more to hydrogen generation. This is believed to be due to the following reasons. First, when the diameter is 3 nm or more, moisture easily penetrates into the pores, so the hydrogen generation reaction is likely to occur. Also, when the diameter is 500 μm or less, a difference in dissolved oxygen concentration is easily formed between the inside and outside of the pores, so the hydrogen generation reaction is also likely to occur.

[0047] Therefore, in order to increase the efficiency of hydrogen generation, it is preferable to increase the amount of pores that contribute greatly to the hydrogen generation reaction, i.e., pores with diameters of 3 nm to 500 μm. Therefore, the iron-based powder is preferably designed to increase the volume of pores with diameters of 3 nm to 500 μm per unit mass (hereinafter sometimes referred to as "pore volume") to 0.05 cm or less. 3 / g or more.

[0048] In addition, the iron-based powder preferably has an average diameter of pores having a diameter of 3 nm to 500 μm (hereinafter, sometimes referred to as "average pore diameter") of 0.10 μm or more and 100.00 μm or less. When the average pore diameter is 0.10 μm or more, moisture easily enters the pores, and the efficiency of hydrogen generation is further increased. Therefore, the average pore diameter is preferably 0.10 μm or more. When the average pore diameter is 100.00 μm or less, the difference in dissolved oxygen concentration in the moisture in the pores becomes large, and the efficiency of hydrogen generation is further increased. Therefore, the average pore diameter is preferably 100.00 μm or less.

[0049] The pore volume and average pore diameter are measured by mercury intrusion porosimetry. Specifically, first, the pore distribution of the iron-based powder is measured by mercury intrusion porosimetry using a pore distribution measuring device (Shimadzu Corporation-Micromeritics Autopore V9620). During the measurement, about 1 g of the sample is placed in a 5 cc powder cell and measured under the conditions of an initial pressure of 7 kPa, a mercury contact angle of 130°, and a mercury surface tension of 485 dynes / cm. Then, the volume and average diameter per unit mass of pores with diameters of 3 nm to 500 μm are calculated from the measurement results.

[0050] [Manufacturing of iron-based powder] Next, a method for producing the iron-based powder according to the present invention will be described.

[0051] The iron-based powder according to the present invention can be produced by subjecting an iron-based powder produced by a technique such as an atomization method, an oxide reduction method, or a pulverization method to a treatment for increasing the distortion of the α-Fe crystals. The production method will be described in detail below.

[0052] First, an iron-based powder is obtained by a technique such as atomization, oxide reduction, or pulverization. Here, the atomization is a method of obtaining a metal powder by spraying water or gas onto a molten metal to form a spray, which is then cooled and solidified. Either water atomization or gas atomization can be used as the atomization. The oxide reduction is a method of reducing (rough reduction) iron oxide (mill scale) or iron ore powder that is generated on the surface of a steel sheet during hot rolling of the steel material, for example. The pulverization is a method of obtaining a metal powder by pulverizing metal pieces.

[0053] The powder obtained by the atomization method or the oxide reduction method is preferably subjected to a finish reduction. By carrying out the finish reduction, the metallic iron content of the finally obtained iron-based powder can be increased. Note that, when the iron-based powder is obtained by the above-mentioned pulverization method, the metallic iron content is sufficiently high, so that the finish reduction is usually not required.

[0054] In order to increase the metallic iron content of the finally obtained iron-based powder, the method for producing the iron-based powder according to the present invention preferably includes a reduction treatment. The reduction treatment may be one or both of rough reduction and finish reduction. In order to increase the metallic iron content of the finally obtained iron-based powder, it is preferable to use a powder with a high total iron content as a raw material for the reduction treatment.

[0055] As the reduction furnace, for example, a tunnel furnace can be used for rough reduction, and a belt furnace can be used for finish reduction. As the reducing agent, for example, a carbon material such as coke can be used for rough reduction, and hydrogen can be used for finish reduction. As for the reduction temperature, in both the rough reduction and finish reduction, the reduction temperature is set to 0.05 cm3 or less in order to increase the metallic iron content of the finally obtained iron-based powder and to reduce the pore volume to 0.05 cm3 or less. 3 In order to obtain a specific surface area of ​​0.01 m / g or more, it is preferable to heat the powder at 800° C. or higher. 2 / g or more 1.00m 2To achieve an average pore diameter of 0.10 μm or more, the reduction temperature is preferably 800 to 1200° C. In both the rough reduction and the finish reduction, the reduction time is preferably 1 hour or more in order to achieve an average pore diameter of 0.10 μm or more.

[0056] The particle size of the obtained iron-based powder may be adjusted. Here, the powder produced by the atomization method, the oxide reduction method, or the pulverization method, or the powder after the finish reduction is called the powder before particle size adjustment. The powder before particle size adjustment, for example, the powder after reduction, may contain coarse particles of several tens of mm or more. Therefore, the powder before particle size adjustment may be classified, crushed, or mixed.

[0057] For example, the powder before particle size adjustment may be classified by a method such as sieving. The powder before particle size adjustment may be crushed to remove coarse particles. Furthermore, two or more types of powder obtained from the powder before particle size adjustment may be mixed in an appropriate ratio. The conditions for classification, crushing, or mixing can be appropriately adjusted. For example, in the crushing, the crushing time may be set to, for example, less than 10 seconds, since the minimum operation time for removing coarse particles can reduce costs and prevent an increase in oxygen concentration.

[0058] The above classification, crushing, and mixing can be appropriately combined. For example, the powder before particle size adjustment may be crushed and then fine particles may be removed, or the powder before particle size adjustment may be classified by sieving to obtain two or more powders with different particle sizes, and these powders may be mixed in an appropriate ratio.

[0059] Next, since the iron-based powder obtained by the above-mentioned method has almost no distortion of the α-Fe crystals, it is necessary to subject the iron-based powder to a treatment for increasing the distortion of the α-Fe crystals in the iron-based powder. That is, the method for producing an iron-based powder according to the present invention includes a treatment for increasing the distortion of the α-Fe crystals in the iron-based powder. The treatment is preferably a treatment for applying mechanical energy using a mixer or a pulverizer. The mixer is not particularly limited, and a V-type mixer, a double cone mixer, a conical blender, an agitation granulator, or the like can be suitably used. The pulverizer is also not particularly limited, and a ball mill, a vibration mill, a roller mill, a jet mill, a hammer mill, a disk mill, or the like can be suitably used.

[0060] When a mixer is used, D is smaller than when a grinder is used. 50 Therefore, D 50 From the viewpoint of preventing a decrease in the molecular weight and making the iron-based powder easier to handle, it is more preferable that the treatment is a treatment in which mechanical energy is applied using a mixer.

[0061] When a mixer or a pulverizer is used, mechanical energy is imparted by collisions between particles of the iron-based powder and between the particles and the inner surface of the mixer or pulverizer (e.g., inner wall, stirring blade, etc.). Therefore, appropriate mixing conditions or pulverization conditions when using the above mixer or pulverizer can be set to impart distortion to the α-Fe crystal and adjust the lattice spacing to the range of the present invention.

[0062] Specifically, the appropriate mixing time or pulverization time is generally longer than the normal operating conditions. For example, when pulverization is performed for particle size adjustment, the pulverization time may be about several seconds as described above, and pulverization for a long time increases costs. However, in the present invention, the pulverization time may be, for example, 10 seconds or more. For the same reason, the mixing time may be, for example, 3 minutes or more, 5 minutes or more, or 15 minutes or more. The upper limit of the mixing time and pulverization time is not limited, but in order to prevent the iron-based powder from being excessively oxidized, both may be, for example, 60 minutes or less. In addition, when the mixer or pulverizer has a stirring function, the stirring speed may be faster than the normal operating conditions. On the other hand, when the mixing time or pulverization time is longer than the normal operating conditions, the stirring speed may be equivalent to the normal operating conditions. Note that the above mixing time, pulverization time, and stirring speed are merely examples and are not limited, and appropriate mixing time, pulverization time, and stirring speed can be set as long as the lattice spacing is within the range of the present invention described above.

[0063] [Hydrogen production agent] The hydrogen generating agent according to the present invention is a hydrogen generating agent using the iron-based powder. As the hydrogen generating agent, the iron-based powder itself may be used, or the iron-based powder and one or more other materials may be used.

[0064] [How to use iron-based powder and hydrogen generating agent] Next, a method for using the iron-based powder and hydrogen generating agent according to the present invention will be described. Note that the following description shows an example of the method for using the iron-based powder and hydrogen generating agent, and the present invention is not limited to the following description.

[0065] The method of using the iron-based powder or hydrogen generating agent according to the present invention is not particularly limited. For example, hydrogen can be produced by reacting the iron-based powder or hydrogen generating agent according to the present invention with water. The water is not particularly limited, but it is preferable to use distilled water.

[0066] An additive may be added to the water. Examples of the additive include sodium chloride, calcium chloride, potassium chloride, and magnesium chloride, and one or more of these can be used. A passive film made of iron oxide is formed on the surface of the iron-based powder. However, by using the additive, the passive film is destroyed by chloride ions, and a phenomenon (pitting corrosion) occurs in which oxidation progresses inside the iron-based powder. As a result, corrosion progresses, and hydrogen can be produced more efficiently. An acid can be used as the additive. This lowers the pH and promotes hydrogen-generating corrosion that progresses under low pH conditions, allowing hydrogen to be produced more efficiently. For example, citric acid can be used as the acid.

[0067] Since hydrogen generation corrosion progresses under low pH conditions, hydrogen can be produced more efficiently when the pH of the water is low. Therefore, the water is preferably acidic. However, the pH of the water is not limited, and even when the pH is high, hydrogen can be produced efficiently by using the iron-based powder or hydrogen generating agent according to the present invention. This is because, as the hydrolysis of iron ions and the formation of oxygen concentrations progress based on the above-mentioned reaction mechanism, even when the pH of the solvent as a whole is high, a region with a high hydrogen ion concentration is locally generated, and hydrogen generation corrosion progresses in that region. Therefore, the water may be neutral or alkaline. EXAMPLES

[0068] Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples, and appropriate modifications can be made within the scope of the present invention, and all of these modifications are included in the technical scope of the present invention.

[0069] The iron-based powder for hydrogen production used in this example was produced by the following procedure.

[0070] Powder was produced by water atomization using molten steel as a raw material. The powder was subjected to finish reduction at 800 to 1300°C and classified to adjust the particle size to obtain iron powder. In the finish reduction, a belt furnace was used as a reduction furnace and hydrogen gas was used as a reducing agent.

[0071] Next, 1 kg of the obtained iron powder was stirred using a high-speed mixer (mixing granulator manufactured by Fukae Powtec Co., Ltd., model number: LFS-GS-2J) to obtain iron-based powders for hydrogen production used in this example. All of the iron-based powders for hydrogen production were iron powders. The stirring was performed with the agitator blade rotation speed in the sample loading container set to 500 rpm for the stirring times shown in Table 1.

[0072] In Comparative Example 1, stirring with a high-speed mixer was not performed.

[0073] The lattice spacing obtained from the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal among the diffraction peaks of the X-ray diffraction was calculated by performing X-ray diffraction measurement on the iron-based powder using an X-ray diffraction device (SmartLab manufactured by Rigaku Corporation). Specifically, it was calculated by the method described above. The calculation results are shown in Table 1.

[0074] The hydrogen generation efficiency of the iron-based powder was evaluated by the following method.

[0075] In a glass beaker with an internal volume of 150 mL, 1.0 g of each iron-based powder, 3.0 g of distilled water, and 0.9 g of sodium chloride were placed, and the glass beaker was sealed in the atmosphere using a rubber stopper. The glass beaker itself was then kept at 60°C and stirred at a rotation speed of 1800 rpm. A shaking incubator (manufactured by AS ONE Corporation) was used for keeping the temperature and stirring. 480 minutes after the start of stirring, a hole was made in the rubber stopper, and 1 mL of gas was collected from the glass beaker using a syringe, and the hydrogen concentration in the gas was measured using a gas chromatograph (manufactured by GL Sciences Inc.). The higher the hydrogen concentration, the more hydrogen was generated, and the more efficient the hydrogen generation. The measurement results of the hydrogen concentration are shown in Table 1.

[0076] As is clear from the results shown in Table 1, the iron-based powders of Examples 1 to 6, which were mixed for an appropriate time with a high-speed mixer to have a lattice spacing of 2.000 Å or more, reached a hydrogen concentration of 10 volume % or more and had good hydrogen generation efficiency, compared to the iron-based powders of Comparative Examples 1 to 3, which had a lattice spacing of less than 2.000 Å. Moreover, the iron-based powder of Comparative Example 4, which had a lattice spacing of more than 2.100 Å, had a low hydrogen concentration of less than 10 volume %, and had poor hydrogen generation efficiency.

[0077] [Table 1]

Claims

1. The iron-based powder for hydrogen production has a lattice spacing in the range of 2.000 Å to 2.100 Å, determined from a diffraction intensity curve corresponding to the (110) diffraction plane of an α-Fe crystal among the diffraction peaks of X-ray diffraction.

2. A hydrogen producing agent using the iron-based powder for producing hydrogen according to claim 1.

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