JP7417026B1 - Hydrogen production catalyst and its production method, and hydrogen production method - Google Patents

Abstract

The present invention focuses on the magnetic interaction between a catalyst metal and H+ ions (protons) to provide a novel catalyst for hydrogen production that can be obtained or supplied stably at low cost. [Solution] This is a hydrogen production catalyst used to produce hydrogen from ammonia borane (NH3BH3), a hydrogen-containing compound, and is composed of ferromagnetic cobalt (Co) and iron-based metal nickel (Ni). ) and iron (Fe), and is composed of 48 to 99.7 wt% of Co and 0.3 to 52 wt% of iron-based metals, and the components of this magnetic alloy are The average magnetic moment per atom of the alloy particles is in the range of 1.1 to 2.3 in Bohr magneton units. [Selection diagram] Figure 1

Description

The present invention relates to a catalyst for producing hydrogen, a method for producing the same, and a method for producing hydrogen from a hydrogen-containing compound.

BACKGROUND ART Hydrogen has traditionally attracted attention as an energy source that suppresses environmental destruction, and fuel cells that use hydrogen as fuel have been attracting attention and being put into practical use.

Hydrogen is in a gas phase at room temperature and pressure, and the volume of a given reaction amount is hundreds to thousands of times larger than that of a solid phase. Difficult to store and transport. In order to solve these problems with hydrogen gas and make it safe and easy to handle, hydrogen gas obtained by reforming natural gas, methanol, gasoline, etc. is used as fuel for fuel cells. ing.

This type of fuel not only has safety issues, but also has insufficient electromotive force when used as fuel for a fuel cell, making it impossible to achieve sufficient performance as a power supply source.

Therefore, for fuel cells used as the drive source of automobiles and fuel cells used as the power source for consumer mobile terminal devices, hydrogen-containing compounds that store hydrogen in high concentrations are used at low cost, stably, and with high efficiency. There is a desire to generate hydrogen using batteries, and to further downsize the batteries themselves.

In view of these problems with conventionally used hydrogen-containing media, intensive research has been carried out on fuels that are safe, easy to handle, and can generate sufficient electromotive force when used as fuel for fuel cells. Hydrogen-containing compounds containing high concentrations of hydrogen have been proposed. As this type of hydrogen-containing compound, a boron-based compound that can store a large amount of hydrogen has been proposed. One of them is borohydride compounds of alkali metals and alkaline earth metals. As another example, ammonia borane (NH ₃ BH ₃ ), which is a compound based on a complex of borane (BH ₃ ) and ammonia (NH ₃ ), has been proposed (Patent Documents 1 and 2).

Hydrogen contained in this type of hydrogen-containing compound is produced, for example, by adding a noble metal such as platinum (Pt) as a catalyst to an aqueous solution in which the hydrogen-containing compound is dissolved and hydrolyzing this aqueous solution.

Precious metals such as Pt used in catalysts are scarce and expensive, making it difficult to generate hydrogen stably at low cost from hydrogen-containing compounds such as ammonia borane.

The inventors of this application have proposed the use of tungsten carbide doped with ferromagnetic Co nanocrystals as a catalyst used to generate hydrogen from hydrogen-containing compounds, replacing noble metals such as Pt ( Patent Documents 3, 4).

Japanese Patent Application Publication No. 2006-286549 Japanese Patent Application Publication No. 2009-176556 JP2018-223932A Patent Application No. 2021-171539

By the way, Co, which is used in the catalyst for hydrogen production proposed by the inventors of the present application, is used as a material for positive electrodes of lithium batteries, and its demand is rapidly expanding and resources are becoming scarce.

Therefore, it is desired to reduce the proportion of Co used in catalysts containing Co that have been proposed for use as catalysts for hydrogen production, thereby saving the amount of Co resources.

Here, as a result of intensive research into the characteristics of catalysts used to generate hydrogen from hydrogen-containing compounds such as ammonia borane (NH ₃ BH ₃ ), the present inventors discovered that the catalytic metal and H ⁺ ions (protons) Focusing on magnetic interaction, we have realized and proposed a new catalyst for hydrogen production that can be obtained or supplied inexpensively and stably.

The present inventors focused on the effects and functions of catalysts used to generate hydrogen from hydrogen-containing compounds such as ammonia borane (NH ₃ BH ₃ ), and as a result of intensive research, discovered that they can be used as catalysts for hydrogen production. A useful catalyst for hydrogen production is realized and proposed.
The catalyst proposed by the present inventors is a hydrogen production catalyst used to generate hydrogen from ammonia borane (NH ₃ BH ₃ ), and is a catalyst that combines ferromagnetic cobalt (Co) and other ferromagnetic metals. Consisting of a magnetic alloy containing at least one kind, this magnetic alloy is an alloy containing 92 to 85 mol% of cobalt (Co), 8 to 15 mol% of iron (Fe), or 96 to 92 mol% of cobalt (Co), It consists of an alloy containing 4 to 8 mol% of nickel (Ni), and the average magnetic moment per atom of the alloy particles constituting this magnetic alloy is in the range of 1.55 to 1.87 μB in Bohr magneton units. It is characterized by

Iron (Fe) or nickel (Ni) can be used as the other ferromagnetic metal constituting this magnetic alloy. The magnetic alloy is configured to contain Co and one of Fe and Ni.

The magnetic catalyst for hydrogen production used to produce hydrogen proposed in this document is produced by the procedure shown below.

To produce a magnetic catalyst for hydrogen production, first, a mixed aqueous solution is prepared by mixing an aqueous solution of cobalt acetate containing cobalt ions, an aqueous solution of nickel acetate containing nickel ions, or an aqueous solution of iron nitrate containing iron ions. do.

Next, the mixed aqueous solution is evaporated to dryness or spray-dried to produce a dried product, this dried product is heat-treated and thermally decomposed to produce an oxide, and this oxide is reduced with hydrogen in a hydrogen atmosphere. . The hydrogen-reduced oxide is a powdered magnetic alloy containing the ferromagnetic cobalt (Co) and either ferromagnetic nickel (Ni) or iron (Fe).

As the mixed aqueous solution, a mixed aqueous solution prepared by mixing the cobalt acetate aqueous solution and the iron nitrate aqueous solution is used. This mixed aqueous solution is prepared by mixing the cobalt acetate aqueous solution and the iron nitrate aqueous solution so that it contains 99 to 47 (50) mol% of the cobalt component and 1 to 53 mol% of the iron component.

Further, as the mixed aqueous solution, a mixed aqueous solution prepared by mixing the cobalt acetate aqueous solution and the nickel acetate aqueous solution is used. This mixed aqueous solution is prepared by mixing the cobalt acetate aqueous solution and the iron nitrate aqueous solution so that it contains 99 to 48 mol% of the cobalt component and 1 to 52 mol% of the nickel component.

Note that the dried product produced by drying the mixed aqueous solution is heat-treated in an oxygen atmosphere at 500° C. to 600° C. to form an oxide. This oxide contains either ferromagnetic cobalt (Co), ferromagnetic nickel (Ni), or iron (Fe) by hydrogen reduction in a hydrogen atmosphere at 750°C to 850°C. It is considered to be a powdered magnetic metal.

By mixing any one of the above-mentioned magnetic metals proposed by the present inventors with an aqueous solution of a hydrogen-containing compound, such as ammonia borane (NH ₃ BH ₃ ), and hydrolyzing this mixed aqueous solution, the hydrogen-containing compound Hydrogen gas (H ₂ ) is generated from this.

Therefore, the magnetic alloy produced through the above-described production process is used as a magnetic catalyst for hydrogen production.

The magnetic catalyst for hydrogen production proposed in this paper has hydrophilic properties, so it can be used as a catalyst for hydrolyzing hydrogen-containing compounds such as ammonia borane (NH ₃ BH ₃ ), which allows hydrogen to be stored in high concentrations. It is suitable for use. This magnetic catalyst improves the conversion rate of hydrogen (H ₂ ) gas contained in hydrogen-containing compounds such as ammonia borane, which enables storage of hydrogen at high concentrations, and converts hydrogen (H ₂ ) stably and efficiently. Enables gas generation.

Furthermore, the magnetic catalyst proposed in this document does not use precious metals such as Pt, and furthermore, it is inexpensive because it uses an abundant resource, reducing the amount of cobalt (Co), whose resources are becoming increasingly scarce. This makes it possible to provide a stable supply.

Furthermore, since the catalyst for hydrogen production proposed in this document has magnetism, it can be easily recovered using magnetic force after being used as a catalyst for hydrogen production. By enabling reuse, hydrogen can be produced at even lower cost.

FIG. 2 is a diagram schematically showing a model of the magnetic interaction between the nuclear spin of protons released from ammonia borane into an aqueous solution and the electron spin of a single domain crystal of a magnetic metal in an aqueous solution in which the magnetic metal is dissolved. FIG. 3 is a diagram showing the relationship between the acceleration a acting on protons and the distance r between the protons and a single magnetic domain crystal of an alloy particle that is a component of a magnetic alloy. FIG. 7 is a diagram showing the potential energy Umag due to the magnetic force of the alloy particles acting on protons when the distance r between the protons and the single magnetic domain crystal of the alloy particles is 0.03 to 0.06 nm. Hydrogen production rate (HER) when the magnetic alloy of cobalt (Co) and iron (Fe) or nickel (Ni) shown in (a) is used as a catalyst for hydrolysis of ammonia borane (NH ₃ BH ₃ ), It is a figure which shows the relationship with the Slater-Pauling magnetic moment curve shown in (b).

The present inventors discovered that H ⁺ ions (protons) generated in an aqueous solution of a hydrogen-containing compound such as ammonia borane (NH ₃ BH ₃ ) and the magnetic properties of a magnetic metal functioning as a catalyst dissolved in this aqueous solution By focusing on interactions, we have realized a useful magnetic catalyst for hydrogen production that can be used to generate hydrogen by desorbing hydrogen molecules from hydrogen-containing compounds.

Therefore, we will explain the magnetic interaction between the nuclear spin of protons emitted from ammonia borane and the electron spin of single domain crystals of alloy particles constituting a magnetic alloy with reference to the model shown in Figure 1. do.

In this model, a mixed aqueous solution was used, which was a mixture of an aqueous solution containing ammonia borane and a solution containing a magnetic alloy.

In FIG. 1, which shows the magnetic interaction between the nuclear spin of a proton and the electron spin of a single-domain crystal of an alloy particle, the distance between the proton emitted from ammonia borane and the single-domain crystal of a magnetic alloy is indicated by r. Then, the protons that are hydrated in the mixed aqueous solution and move as hydronium ions (H ₃ O ⁺ ) along random walking trajectories due to Brownian motion are magnetically attracted by the magnetic force of the magnetic alloy dissolved in the mixed aqueous solution. Let rc be the critical distance at which the trajectory changes to approach the magnetic alloy.

Referring to Figure ¹ , the magnetic dipole interaction ( The potential energy Umag due to dipole interaction is defined by the following equation (1).

Umag=-(M _ferro・_MP /2πμ ₀ r ³ )...(1)

In equation (1), M _Ferro is the magnetic moment of the alloy particle, M _P is the magnetic moment of the proton, and in Figure 1, r is the relationship between the proton (H ⁺ ) and the single domain crystal of the magnetic metal. is the distance between.

Therefore, the magnetic force (F) acting on the single domain crystal of the magnetic alloy particle and the proton can be calculated by differentiating the potential energy Umag with the distance r between the single domain crystal of the magnetic alloy particle and the proton, and using the following equation (2). defined.

F=du/dr=3M _Ferro・_MP /2πμ ₀ r ⁴ ...(2)

By dividing this magnetic force F by the mass mp of the proton, the acceleration a of the proton is determined by the following equation (3).

a=F/mp=3M _Ferro・_MP /2πμ ₀ r ⁴ m _p ...(3)

Here, the mass m _p of the proton is 1.671×10 ⁻²⁷ (kg). The magnetic permeability μ ₀ of vacuum is 4π×10 ⁻⁷ (Hm ⁻¹ ).

The effect of the magnetic force of ferromagnetic metal particles on protons was simulated with reference to the reaction model shown in FIG. This simulation was performed using a ferromagnetic magnetic alloy containing cobalt (Co) and iron (Fe) as ferromagnetic metal particles.

The magnetic alloy used in this simulation contains 92.39 wt% cobalt (Co) and 7.61 wt% iron (Fe). The influence of the magnetic force of this magnetic alloy on protons was confirmed using alloy particles having a diameter of 60 nm, which is a typical single magnetic domain size in this type of magnetic alloy.

Based on the well-known Slater-Pauling magnetic moment curve shown in Figure 4, the average magnetic moment per atom of the Co-Fe alloy containing cobalt (Co) and iron (Fe) in the above-mentioned proportions used in this simulation is , in units of Bohr magnetons, is 1.808 μB. Here, the number of moles (n) contained in the alloy particles of this magnetic alloy having a diameter of 60 nm is 1.680×10 ⁻¹⁷ mol based on its density. Therefore, the number of atoms (N) contained in this alloy particle is 1.012×10 ⁷ . The average magnetic moment per atom is 1.808 _μB , and N times this average magnetic moment is the magnetic moment MFero of an alloy particle having a diameter of 60 nm, which is expressed by the following equation (4).

M _Ferro = 1.345×10 ^-21 (Wbm) ... (4)

The proton magnetic moment M _p is given by the following equation (5).

M _p =6.33×10 ^-33 (Wbm) (5)

By substituting the value shown in equation (4) and the value shown in equation (5) into equation (3), the acceleration a acting on the proton and the distance between the proton and the single domain crystal of the alloy particle mentioned above are calculated. The relationship with r was calculated. The calculated results are shown in FIG. 2.

From the above equation (3), when the distance r between the proton and the single magnetic domain crystal of the alloy particle is 2.3646 μm, the acceleration a acting on the proton is 9.807 ms ^-2 , and this value is calculated by adding a decimal point to the gravitational acceleration g. It was found that the following three digits matched. From the results of this simulation, it was found that the above-described simulation method is effective for evaluating the attractive interaction between the nuclear spin of protons and the electron spin of alloy particles constituting a magnetic metal.

By the way, it is known that protons are hydrated in an aqueous solution and exist as hydronium ions (H ₃ O ⁺ ). The hydration enthalpy ΔH ⁺ ad of this proton is −260.7±2.5 (kcal mol ⁻¹ ). That is, the enthalpy of hydration per proton is -1.811 (aJ(H ⁺ ad) ^-1 ). Therefore, protons are undergoing Brownian motion as H ₃ O ⁺ in an aqueous solution. Further, at the same time as this Brownian motion, protons are moving to separate from a certain H ₃ O ⁺ and hydrate into another H ₂ O molecule. The migration distance for this desorption and hydration is 0.06 to 0.08 nm. Note that in the H ₂ O molecule, the distance of the O--H bond is 0.0957 nm. Even considering that protons are hydrated in an aqueous solution, the above-described method for evaluating the attractive interaction between the nuclear spin of protons and the electron spin of alloy particles constituting a magnetic metal is effective.

Therefore, the above-mentioned ferromagnetic alloy particles containing 92.39 wt% of cobalt (Co) and 7.61 wt% of iron (Fe) and having a diameter of 60 nm exert magnetic force on protons at a short distance. The potential energy Umag was simulated.

FIG. 3 shows changes in potential energy Umag due to the magnetic force of the alloy particles acting on protons when the distance r between the protons and the alloy particles is 0.03 to 0.06 nm.

As shown in FIG. 3, the potential energy Umag became deeper on the negative side as the distance r between the proton and the single domain crystal of the alloy particle decreased.

Here, when the distance r is 0.04552 nm, the potential energy Umag of the proton is −1.811 (aJ(H ⁺ ad) ⁻¹ ), which is equal to the hydration enthalpy ΔH ⁺ ad of the proton. This distance r is defined as a critical distance rc. That is, when the distance r is smaller than the critical distance rc, the potential energy Umag becomes deeper than the hydration enthalpy ΔH ⁺ ad, and the protons are attracted to the magnetic material rather than hydrated. In other words, a magnetic alloy containing 92.39 wt% cobalt (Co) and 7.61 wt% iron (Fe) can attract protons within 0.04552 nm from its surface to rapidly generate hydrogen. I can do it.

On the other hand, when the distance r between the proton and the single magnetic domain crystal of the alloy particle is larger than the critical distance rc, the proton is more stable when hydrated and undergoes Brownian motion as H ₃ O ⁺ . That is, the critical distance rc is the distance r at which the proton changes from a random walking trajectory due to Brownian motion to a trajectory approaching the magnetic material.

Then, 1 mol of solid powder of ammonia borane NH ₃ BH ₃ (cr) is dissolved in an aqueous solution and undergoes hydration to produce 3 mol of gaseous hydrogen H ₂ (g) through hydrated molecules NH ₃ BH ₃ (aq). The decomposition reaction is defined by the following equation (6) based on thermodynamic equilibrium theory, with an initial state on the left side and a final state on the right side.

NH ₃ BH ₃ (cr) + 2H ₂ O (l) = BO ₂ ^- (aq) + NH ₄ ⁺ (aq) + 3H ₂ (g)
ΔrH ⁰ /kj=-155.983±6.016 (6)

In equation (6), the standard reaction enthalpy ΔrH ⁰ is a negative exothermic reaction.
Note that the standard entropy of formation ΔrS ⁰ of solid ammonia borane NH ₃ BH ₃ (cr) has not yet been measured.
In the above formula (6), the left side is 1 mol of solid ammonia borane (NH ₃ BH 3 (cr)) and 2 mol of liquid molecules (H ₂ 0(l)), while the right side is a total of 2 mol of ammonia borane (NH _{3 BH 3} (cr)) It consists of ions (BO ₂ ⁻ (aq))), NH ₄ ⁺ (aq) and 3 moles of gas molecules (H ₂ (g)), and there is no doubt that the standard enthalpy of reaction ΔrS ⁰ is positive. Therefore, the standard reaction Gibbs energy ΔrG ⁰ is negative, and it is a spontaneous reaction from the standpoint of equilibrium theory.

From the above simulation, in order for the hydrolysis reaction of ammonia borane, which is a hydrogen-containing compound, to proceed, alloy particles adsorb and decompose ammonia borane (NH ₃ BH ₃ (aq)) molecules in an aqueous solution, and protons are released. It is necessary to release the released protons, reduce them to atomic hydrogen, combine these atomic hydrogens to form hydrogen molecules, and remove these hydrogen molecules as a gas.

Therefore, in order for the protons released from ammonia borane and the moving protons to be released from H ₃ O ⁺ and hydrated to other H ₂ O molecules, the magnetic metal alloy particles must magnetically attract them. .

Therefore, based on the knowledge based on the simulation described above, the present inventors have realized a ferromagnetic magnetic alloy that has a magnetic moment sufficient to magnetically attract protons into approaching orbits in an aqueous solution containing a hydrogen-containing compound. .

In particular, in order to be able to supply this magnetic metal stably and at low cost, it is possible to efficiently generate hydrogen from hydrogen-containing compounds such as ammonia borane while reducing the usage rate of Co, which is a scarce resource. This is a metal material that functions as a catalyst.

By the way, magnetic alloys containing cobalt Co used as a catalyst for hydrogen production and either iron-based metals iron Fe or nickel Ni and manufactured with nano-sized particles vary depending on the manufacturing conditions. manufactured with a particle size of

When such magnetic alloys with various particle sizes are used as catalysts for hydrogen production, protons dissolved in an aqueous solution of a hydrogen-containing compound are magnetically attracted from random walking trajectories due to Brownian motion and approach the magnetic alloy. The critical distance rc for changing the trajectory changes depending on the various particle sizes of the magnetic alloy used as a catalyst. Therefore, the critical distance rc has a distribution width that corresponds to the particle size distribution of the magnetic metal used as the catalyst.

However, when the types of constituent metals, content ratios, and manufacturing methods are the same, the distribution width of the critical distance rc is the same when a magnetic alloy is used as a catalyst.

Therefore, the critical distance rc, which was obtained by simulating hydrogen production using a magnetic alloy whose single domain particle size is alloy particles with a diameter of 60 nm, is a parameter for efficiently assembling protons into a magnetic alloy. - is suitable for relative comparison of the catalytic properties of magnetic alloys to be produced, and is effective in designing magnetic alloys for hydrogen production. That is, it is effective in designing a magnetic alloy having an average magnetic moment sufficient to magnetically attract protons on random walking trajectories due to Brownian motion.

The catalyst for hydrogen production according to the present embodiment proposed based on the above-mentioned knowledge is a catalyst for hydrogen production used for producing hydrogen from ammonia borane (NH ₃ BH ₃ ), which is a hydrogen-containing compound. A magnetic alloy containing ferromagnetic cobalt (Co) and one of iron-based metals nickel (Ni) and iron (Fe), containing 48 to 99 wt% of Co, and containing iron-based metals such as nickel (Ni) and iron (Fe). The alloy particles contain 1 to 52 wt% of metal, and the average magnetic moment per atom of the alloy particles is in the range of 1.1 to 2.3 in Bohr magneton units.

Based on the above-mentioned knowledge, the magnetic alloy according to the present embodiment contains Co in an amount of 48 to 99 wt% and a ferromagnetic metal in an amount of 1 to 52 wt%. The average magnetic moment per atom can be 1.1 to 2.3 μB in Bohr magnetons.

By containing Co and other ferromagnetic metals in the above-mentioned content range, the magnetic alloy can produce hydrogen at a practical rate when used as a catalyst for producing hydrogen from ammonia borane. I was able to do it.

By setting the average magnetic moment per atom to at least 1.1 μB in Bohr magneton units, it is possible to generate hydrogen at a practical rate while greatly reducing the amount of Co used.

Furthermore, by achieving an average magnetic moment per atom of 2.3 μB in Bohr magneton units, it is possible to reduce the amount of Co used while realizing hydrogen production at a high rate.

According to the results of the simulation described above, a magnetic alloy composed of Co and either Ni or Fe can be used as a component constituting the magnetic alloy if the content ratio of Co is 48 Wt% or less. It becomes difficult to make the average magnetic moment per atom of the alloy particles 1.1 μB or more in Bohr magneton units, and it cannot be used as a catalyst for producing hydrogen from ammonia borane at a practical rate.

Furthermore, when the Co content exceeds 99 Wt%, hydrogen can be produced from ammonia borane at a sufficiently high rate and at a practical rate, but it becomes difficult to achieve the purpose of reducing the amount of Co used. Become.

The magnetic alloy used as the magnetic catalyst for hydrogen production according to the present embodiment can be prepared using either an aqueous solution of cobalt acetate containing cobalt ions, an aqueous solution of nickel acetate containing nickel ions, or an aqueous solution of iron nitrate containing iron ions. It is prepared using a mixed aqueous solution.

A magnetic alloy containing Co and Fe is produced using a mixed aqueous solution of an aqueous solution of cobalt acetate and an aqueous solution of iron nitrate. This mixed aqueous solution is prepared by mixing the cobalt acetate aqueous solution and the iron nitrate aqueous solution so that it contains 99 to 47 mol% of the cobalt component and 1 to 53 mol% of the iron component.

Further, a magnetic alloy containing Co and Ni is produced using a mixed aqueous solution obtained by mixing an aqueous solution of cobalt acetate and an aqueous solution of nickel acetate. This mixed aqueous solution is prepared by mixing an aqueous solution of cobalt acetate and an aqueous solution of iron nitrate so that it contains 99 to 48 mol% of a cobalt component and 1 to 52 mol% of a nickel component.

As described above, the mixed aqueous solution obtained by mixing each component is evaporated to dryness or spray-dried to produce a dried product. The dried product obtained here is thermally decomposed into oxides. Thermal decomposition of the dried material into oxides is carried out by holding it in an oxygen atmosphere at 500° C. to 600° C. for about 2 hours.

The oxide produced by thermally decomposing the dried material is hydrogen-reduced to form an alloy powder, which is an aggregate of alloy particles having a particle size of nanometers (nm). Here, the hydrogen reduction is performed by holding the oxide obtained in the above step in a hydrogen atmosphere at 750° C. to 850° C., preferably in a hydrogen atmosphere at 800° C. for about 3 hours.

Here, a magnetic alloy prepared using an aqueous solution containing an aqueous solution of cobalt acetate and an aqueous solution of iron nitrate so as to contain 99 to 50 mol% of a cobalt component and 1 to 53 mol% of an iron component contains 48% of Co. ~99 wt%, and 1~52 wt% Fe. The magnetic alloy may have an average magnetic moment per atom of the alloy particles in the range of about 1.1 to 2.3 μB in Bohr magnetons.

In addition, a magnetic alloy prepared using an aqueous solution of cobalt acetate and nickel acetate containing 99 to 48 mol% of cobalt component and 1 to 52 mol% of nickel component contains 48% of Co. ~99 wt%, and 1~52 wt% Ni. This magnetic alloy can have an average magnetic moment per atom of the alloy particles in the range of about 1.1 to 1.8 μB in Bohr magneton units.

The magnetic alloy produced according to this embodiment has an average magnetic moment per atom of the alloy particles constituting the alloy of 1.1 to 2.3 μB in Bohr magneton units, so it It is useful for use in catalysts that generate hydrogen, and it is possible to reduce the amount of Co used.

The magnetic alloy according to this embodiment contributes to the generation of hydrogen by the magnetic force of this magnetic alloy acting on protons eluted into an aqueous solution, so when it is dissolved in an aqueous solution, protons are generated in the aqueous solution. It can be used as a catalyst to generate hydrogen from hydrogen-containing compounds that elute.

In particular, the magnetic alloy according to the present embodiment is useful as a catalyst for producing hydrogen from a water-soluble hydrogen-containing compound based on boron (B) in addition to the ammonia borane described above.

Note that the magnetic metal used as the catalyst for hydrogen production according to the present embodiment may be dispersed and supported on the surface of the carrier using fine oxide particles. As this carrier, oxides such as aluminum oxide (Al ₂ O ₃ ) and silicon dioxide (SiO ₂ ) can be used. By being dispersed and supported on the surface of the carrier, the magnetic metal constituting this embodiment can improve dispersibility and improve catalytic activity.

Specific examples of the magnetic catalyst for hydrogen production proposed in this document are shown below.

(Example 1)
Example 1 is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound, and is a magnetic alloy containing 92.39 wt% Co and 7.61 wt% Fe. , produced by hydrothermal synthesis as follows.

This magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and an iron nitrate aqueous solution containing iron ions. This mixed aqueous solution was prepared by mixing cobalt acetate and iron nitrate so that the molar ratio of Co and Fe was 92:8. This mixed aqueous solution is evaporated to dryness to obtain a dry product. This dried product is kept in an oxygen atmosphere at 500° C. for 2 hours to be thermally decomposed into oxides. The thermally decomposed oxide is held in a hydrogen atmosphere at 800° C. for 2 hours to undergo hydrogen thermal reduction, and the structure at room temperature becomes a hexagonal close-packed lattice (HCP), resulting in a fine alloy powder of nanoparticle size. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 92.39 wt% Co and 7.61 wt% Fe.

The magnetic alloy containing 92.39 wt% Co and 7.61 wt% Fe according to Example 1 has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. It is assumed that the electron density is 1.818 μB and the valence electron concentration is 8.92.

That is, as shown in FIG. 4, pure Fe constituting the Co--Fe alloy has six electrons in 3d and two electrons in 4s in its atomic structure, so that the valence electron concentration is 8. As shown in FIG. 4, pure Co has 7 electrons in 3d and 2 electrons in 4s, so that the valence electron concentration is 9.

The valence electron concentration of the magnetic alloy of Example 1 containing 92.39 wt% Co and 7.61 wt% Fe can be defined as the average composition of pure Fe and pure Co that constitute the magnetic metal.8. It is 92. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 8.92 is shown to be 1.818 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 1, which was prepared with a magnetic moment of 1.818 μB in Bohr magneton units as described above, as a catalyst. .

To generate hydrogen from ammonia borane, first, the magnetic alloy powder is mixed with pure water to prepare a magnetic alloy mixture.

The magnetic alloy to be mixed with pure water is classified to have a particle size of 32 μm or less. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

By using a magnetic alloy classified to have a particle size of 32 μm or less, the particle size of the alloy particles mixed in the aqueous solution can be made uniform, and the surface area thereof can be made uniform. By making the particle size and surface area of the alloy particles uniform, the protons that are magnetically attracted to each alloy particle are also made uniform, which leads to uniform hydrogen production in the aqueous solution in which the magnetic alloy is dissolved. It is possible to achieve stable hydrogen production.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by mixing 0.5 mmol of ammonia borane powder with 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and 2.5 ml of this mixed aqueous solution (see FIG. 4) was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.

Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieves 4.195 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4. where M is a magnetic metal or alloy as a catalyst.

As described above, by using the magnetic metal of Example 1 having a magnetic moment of 1.818 μB and containing fine particles with a diameter of 60 nm as a hydrogen production catalyst, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approaching trajectory toward the magnetic metal is 0.04552 nm. _The hydrogen production reaction ^rate (R Hydrogen production was achieved at a practical rate with _HER ) of 4.195 (L(H ₂ ) min ^-1 (mol of M) ^-1) .

By the way, magnetism is produced through a manufacturing process that includes a heat treatment step for drying a mixed aqueous solution of cobalt acetate and iron nitrate, and a treatment step for reducing the oxide obtained by oxidizing this dried product with hydrogen. Metals are produced as fine particles having a constant particle size distribution with nanoparticle size.

When a magnetic metal made with a certain particle size distribution is used as a catalyst for producing hydrogen from ammonia borane, the critical distance rc mentioned above also depends on the particle size of the alloy particles constituting the magnetic metal. It has a distribution width corresponding to the distribution width of . However, the distribution width of the critical distance rc is the same when magnetic alloys made using the same types of constituent metals, content ratios, and manufacturing methods are used as catalysts.

Therefore, the critical distance rc obtained by simulating the production process of hydrogen production from ammonia borane using a magnetic alloy containing alloy particles with a particle size of 60 nm that can maintain a single magnetic domain as a catalyst is the critical distance rc that efficiently converts protons into magnetic molecules. It is a parameter for aggregation into metals, is suitable for relative comparison of catalyst properties, and is effective in catalyst design.

The magnetic alloy according to Example 1 is made by replacing a part of the Co constituting the magnetic alloy with Fe, thereby reducing the usage rate of Co, which is a scarce resource, while efficiently converting hydrogen-containing compounds such as ammonia borane. This enables the generation of good hydrogen.

(Example 2)
Example 2, like Example 1, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound, and contains 96.02 wt% Co and 3.98 wt% Ni. It is a magnetic alloy containing a ferromagnetic acid, which is produced by hydrothermal synthesis as follows.

This magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and a nickel acetate aqueous solution containing nickel ions. This mixed aqueous solution was prepared by mixing cobalt acetate and nickel acetate so that the molar ratio of Co and Ni was 96:4. This mixed aqueous solution is evaporated to dryness to obtain a dry product. This dried product is kept in an oxygen atmosphere at 500° C. for 2 hours to be thermally decomposed into oxides. The thermally decomposed oxide is maintained in a hydrogen atmosphere at 800° C. for 2 hours to undergo hydrogen thermal reduction, and is made into a fine alloy powder having a hexagonal close-packed lattice (hcp) structure at room temperature. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 96.02 wt% Co and 3.98 wt% Ni.

The magnetic alloy according to Example 2 containing 96.02 wt% Co and 3.981 wt% Ni has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. It is assumed that the electron density is 1.66 μB and the valence electron concentration is 9.04.

That is, as shown in FIG. 4, pure Ni constituting the Co--Ni alloy has eight electrons in 3d and two electrons in 4s in its atomic structure, so that the valence electron concentration is 10. As shown in FIG. 4, pure Co has 7 electrons in 3d and 2 electrons in 4s, so that the valence electron concentration is 9.

The valence electron concentration of the magnetic alloy of Example 2 containing 96.02 wt% Co and 3.92 wt% Ni can be defined as the average composition of pure Ni and pure Co that constitute the magnetic metal.8. It is 92. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 9.04 is shown to be 1.66 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 2, which was prepared as described above with a magnetic moment of 1.66 μB in Bohr magneton units, as a catalyst. .

To generate hydrogen from ammonia borane, first, a mixed solution of a magnetic alloy is prepared by mixing powder of the magnetic alloy described above with pure water.

As in Example 1, the magnetic alloy to be mixed with pure water is an alloy powder that has been classified to have a particle size of 32 μm or less to make the particle size uniform. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and 2.5 ml of this mixed aqueous solution (see FIG. 4) was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieves 3.441 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4. where M is a magnetic metal or alloy as a catalyst.

As mentioned above, by using the magnetic alloy of Example 2, which is a magnetic metal having a magnetic moment of 1.66 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approaching trajectory toward the magnetic metal is 0.04439 nm. _The hydrogen ^production reaction rate (R Hydrogen production was achieved at a practical rate with _HER ) of 3.441 (L(H ₂ ) min ^-1 (mol of M) ^-1) .

The magnetic alloy according to Example 2 replaces a part of the Co constituting this magnetic alloy with Ni, thereby reducing the usage rate of Co, which is a scarce resource, while efficiently converting hydrogen-containing compounds such as ammonia borane. It makes it possible to generate hydrogen.

(Example 3)
Example 3 is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound, in the same way as in the previous example, and contains 92.03 wt% Co and 7.97 wt% Ni. It is a magnetic alloy containing a ferromagnetic acid, which is produced by hydrothermal synthesis as follows.

Similar to Example 2, this magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and a nickel acetate aqueous solution containing nickel ions. This mixed aqueous solution was prepared by mixing cobalt acetate and nickel acetate so that the molar ratio of Co and Ni was 92:8. This mixed aqueous solution was evaporated to dryness in the same steps and conditions as in Example 2, and the dried product was thermally decomposed and then subjected to hydrothermal reduction, thereby converting the structure at room temperature into a hexagonal close-packed lattice (HCP). It is said to be a fine alloy powder. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 92.03 wt% Co and 7.97 wt% Ni.

The magnetic alloy according to Example 3 containing 92.03 wt% Co and 7.981 wt% Ni has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. Assume that it is 1.59 μB and the valence electron concentration is 9.08.

As shown in FIG. 4, pure Ni constituting the Co--Ni alloy has eight electrons in 3d and two electrons in 4s in its atomic structure, so that the valence electron concentration is 10. As shown in FIG. 4, pure Co has 7 electrons in 3d and 2 electrons in 4s, so that the valence electron concentration is 9.

The valence electron concentration of the magnetic alloy of Example 3 containing 92.03 wt% Co and 7.98 wt% Ni can be defined as the average composition of pure Ni and pure Co that constitute the magnetic metal.9. It is 08. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 9.08 is shown to be 1.59 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 3, which was prepared with a magnetic moment of 1.59 μB in Bohr magneton units as described above, as a catalyst. .

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 3, which was prepared with a magnetic moment of 1.59 μB in Bohr magneton units as described above, as a catalyst. .

To generate hydrogen from ammonia borane, first, the magnetic alloy powder is mixed with pure water to prepare a magnetic alloy mixture.

As in the above embodiments, the magnetic alloy to be mixed with pure water uses metal powder that has been classified to have a particle size of 32 μm or less to make the particle size uniform. 20 mg of the alloy powder classified to have a particle size of 32 μm or less is weighed and added to 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

Then, together with the magnetic alloy mixture, an ammonia borane aqueous solution is prepared. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) is 2.523 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 3, which is a magnetic metal having a magnetic moment of 1.59 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.043755 nm. A hydrogen production reaction in which hydrogen ions (H) ⁺ , that is, protons existing within this critical distance rc, are brought close to a magnetic metal containing fine alloy particles with a diameter of 60 nm and reacted to produce hydrogen (H ₂ ). Hydrogen production was achieved at a rate (R _HER ) of 3.441 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ that is practical.

The magnetic alloy according to Example 3 replaces a part of the Co constituting this magnetic alloy with Ni, thereby reducing the usage rate of Co, which is a scarce resource, while efficiently converting hydrogen-containing compounds such as ammonia borane. It makes it possible to generate hydrogen.

(Example 4)
Example 4, like Examples 1 to 3, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound. It is a magnetic alloy containing .95 wt%, and is produced by hydrothermal synthesis as follows.

Similar to Examples 2 and 3, this magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and a nickel acetate aqueous solution containing nickel ions. This mixed aqueous solution was prepared by mixing cobalt acetate and nickel acetate so that the molar ratio of Co and Ni was 85:15. This mixed aqueous solution was evaporated to dryness in the same steps and conditions as in Example 2, and the dried product was thermally decomposed and then subjected to hydrothermal reduction, thereby converting the structure at room temperature into a hexagonal close-packed lattice (HCP). It is said to be a fine alloy powder. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 85.05 wt% Co and 14.95 wt% Ni.

This magnetic alloy containing 85.05 wt% Co and 14.95 wt% Ni has a magnetic moment per atom of the alloy particles constituting this magnetic alloy of 1.55 μB in Bohr magneton units. It is assumed that the valence electron concentration is 9.15.

That is, the valence electron concentration of the magnetic alloy of Example 4 containing 85.05 wt% Co and 14.9 wt% Ni can be defined as the average composition of pure Ni and pure Co that constitute the magnetic metal.9. It is 15. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 9.15 is shown to be 1.55 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 4, which was prepared with a magnetic moment of 1.55 μB in Bohr magneton units as described above, as a catalyst. .

First, in order to generate hydrogen from ammonia borane, the powder of the magnetic alloy described above is mixed with pure water to prepare a mixed liquid of the magnetic alloy, as in each of the examples described above.

The magnetic alloy to be mixed with pure water is an alloy powder that has been classified to have a particle size of 32 μm or less and has a uniform particle size. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and 2.5 ml of this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieved 1.1515 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 4, which is a magnetic metal having a magnetic moment of 1.55 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.043755 nm. _The hydrogen production reaction ^rate (R Hydrogen production was achieved at a practically practicable rate with _HER ) of 1.515 (L(H ₂ ) min ^-1 (mol of M) ^-1) .

In the magnetic alloy according to Example 4, by replacing a part of the Co constituting this magnetic alloy with Ni, it is possible to reduce the usage rate of Co, which is a scarce resource, while efficiently converting hydrogen-containing compounds such as ammonia borane. It makes it possible to generate hydrogen.

(Example 5)
Example 5, similar to Examples 1 to 4, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound. It is a magnetic alloy containing .90 wt%, and is produced by hydrothermal synthesis as follows.

Similar to Examples 2 to 4, this magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and a nickel acetate aqueous solution containing nickel ions. This mixed aqueous solution was prepared by mixing cobalt acetate and nickel acetate so that the molar ratio of Co and Ni was 50:50 . This mixed aqueous solution was evaporated to dryness in the same steps and conditions as in Examples 2 to 4, and the dried product was thermally decomposed and then subjected to hydrothermal reduction to change the structure at room temperature to a face-centered hexagonal lattice. fcc) is used as a fine alloy powder. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 50.10 wt% Co and 49.90 wt% Ni.

The valence electron concentration of the magnetic alloy containing 50.10 wt% Co and 49.90 wt% Ni according to Example 5 is defined as the average composition of pure Ni and pure Co that constitute the magnetic metal. It becomes .5. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 9.5 is shown to be 1.18 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 5, which was prepared with a magnetic moment of 1.18 μB in Bohr magneton units as described above, as a catalyst. .

Then, in order to generate hydrogen from ammonia borane, the powder of the magnetic alloy is mixed with pure water to prepare a mixed liquid of the magnetic alloy, as in the above embodiments.

The magnetic alloy to be mixed with pure water is an alloy powder that has been classified to have a particle size of 32 μm or less and has a uniform particle size. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture produced as described above and 1.5 ml of the ammonia borane aqueous solution were mixed, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieved 1.515 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 5, which is a magnetic metal having a magnetic moment of 1.18 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.03966 nm. Hydrogen ions (H) ⁺ , that is, protons existing within this critical distance rc, are brought close to a magnetic metal containing fine alloy particles with a diameter of 60 nm to produce hydrogen (H ₂ ) gas. Hydrogen production was achieved at a practical rate with R _HER ) of 1.515 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ .

The magnetic alloy according to Example 5 also replaces a part of the Co constituting this magnetic alloy with Ni, which is abundant in resources, to reduce the proportion of Co, which is scarce in resources, while also incorporating materials such as ammonia borane. Enables efficient generation of hydrogen from hydrogen-containing compounds.

(Example 6)
Example 6, similar to Example 1, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound, and contains 85.67 wt% Co and 14.33 wt% Fe. %, and is produced by hydrothermal synthesis as follows.

This magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and an iron nitrate aqueous solution containing iron ions. This mixed aqueous solution was prepared by mixing cobalt acetate and iron nitrate so that the molar ratio of Co and Fe was 85:15. This mixed aqueous solution is evaporated to dryness to obtain a dry product. This dried product is kept in an oxygen atmosphere at 500° C. for 2 hours to be thermally decomposed into oxides. The thermally decomposed oxide is maintained in a hydrogen atmosphere at 800° C. for 2 hours to undergo hydrogen thermal reduction, and is made into a fine alloy powder having a hexagonal close-packed lattice (hcp) structure at room temperature. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 86.67 wt% Co and 14.33 wt% Fe.

The magnetic alloy containing 85.67 wt% Co and 14.33 wt% Fe according to Example 6 has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. It is assumed that the electron density is 1.868 μB and the valence electron concentration is 8.85.

That is, the valence electron concentration of the magnetic alloy of Example 6 containing 85.67 wt% Co and 14.33 wt% Fe can be defined as the compositional average of pure Fe and pure Co that constitute the magnetic metal.8. It is 85. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 8.85 is shown to be 1.818 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 6, which was prepared as described above with a magnetic moment of 1.818 μB in Bohr magneton units, as a catalyst. .

Then, in order to generate hydrogen from ammonia borane, the powder of the magnetic alloy is mixed with pure water to prepare a mixed liquid of the magnetic alloy, as in each of the examples described above.

For the magnetic alloy to be mixed with pure water, alloy powder classified to have a particle size of 32 μm or less and made uniform in particle size is used. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

By using an alloy powder of a magnetic alloy that has been classified to have a particle size of 32 μm or less, it can be uniformly dissolved in pure water in a short time.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by mixing 0.5 mmol of ammonia borane powder with 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.

Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) is 2.247 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ , as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 6, which is a magnetic metal having a magnetic moment of 1.868 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approaching trajectory toward the magnetic metal is 0.04602 nm. Hydrogen ions (H) ⁺ , that is, protons existing within this critical distance rc, are brought close to a magnetic metal containing fine alloy particles with a diameter of 60 nm to produce hydrogen (H ₂ ) gas. Hydrogen production was achieved at a practical rate with R _HER ) of 2.247 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ .

The magnetic alloy according to Example 6 also replaces a part of Co with Fe, making it possible to efficiently generate hydrogen from hydrogen-containing compounds such as ammonia borane while reducing the usage rate of Co, which is a scarce resource. .

(Example 7)
Example 7, similar to Examples 1 and 6, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, which is a hydrogen-containing compound. It is a magnetic alloy containing .79 wt %, and is produced by hydrothermal synthesis as follows.

This magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and an iron nitrate aqueous solution containing iron ions. This mixed aqueous solution was prepared by mixing cobalt acetate and iron nitrate so that the molar ratio of cobalt (Co) and iron (Fe) was 65:35. This mixed aqueous solution is evaporated to dryness to obtain a dry product. This dried product is kept in an oxygen atmosphere at 500° C. for 2 hours to be thermally decomposed into oxides. The thermally decomposed oxide is maintained in a hydrogen atmosphere at 800° C. for 2 hours to undergo hydrogen thermal reduction, and is turned into a fine alloy powder having a body-centered cubic lattice (BCC) structure at room temperature. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 66.21 wt% Co and 33.79 wt% Fe.

The magnetic alloy containing 66.21 wt% Co and 33.79 wt% Fe according to Example 7 has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. Assume that it is 2.225 μB and the valence electron concentration is 8.65.

That is, the valence electron concentration of the magnetic alloy of Example 7 containing 66.21 wt% Co and 33.79 wt% Fe can be defined by the compositional average of pure Fe and pure Co that constitute the magnetic metal.8. It is 65. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 8.65 is shown to be 2.225 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 6, which was prepared with a magnetic moment of 2.225 μB in Bohr magneton units as described above, as a catalyst. .

Then, in order to generate hydrogen from ammonia borane, the powder of the magnetic alloy is mixed with pure water to prepare a mixed liquid of the magnetic alloy, as in the above embodiments.

For the magnetic alloy to be mixed with pure water, alloy powder classified to have a particle size of 32 μm or less and made uniform in particle size is used. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by mixing 0.5 mmol of ammonia borane powder with 1.5 ml of pure water.

1.0 ml of the magnetic alloy mixture prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and 2.5 ml of this mixed aqueous solution (see FIG. 4) was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.

Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieved 1.737 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 7, which is a magnetic metal having a magnetic moment of 2.225 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the above-mentioned hydrogen production can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approaching trajectory toward the magnetic metal is set to 0.0486 nm. _The hydrogen production reaction ^rate (R Hydrogen production was achieved at a practical rate with _HER ) of 2.247 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ .

The magnetic alloy according to Example 7 also replaces a part of Co with Fe, making it possible to efficiently generate hydrogen from hydrogen-containing compounds such as ammonia borane while reducing the usage rate of Co, which is a scarce resource. .

(Example 8)
Example 8, like Examples 1, 6, and 7, is a magnetic catalyst for hydrogen production used to generate hydrogen from ammonia borane, and contains 48.65 wt% Co and 51.38 wt% Fe. It is a magnetic alloy containing a ferromagnetic acid, which is produced by hydrothermal synthesis as follows.

This magnetic alloy is produced using a mixed aqueous solution of a cobalt acetate aqueous solution containing cobalt ions and an iron nitrate aqueous solution containing iron ions. This mixed aqueous solution was prepared by mixing cobalt acetate and iron nitrate so that the molar ratio of Co and Fe was 50:50. This mixed aqueous solution is evaporated to dryness to obtain a dry product. This dried product is kept in an oxygen atmosphere at 500° C. for 2 hours to be thermally decomposed into oxides. The thermally decomposed oxide is maintained in a hydrogen atmosphere at 800° C. for 2 hours to undergo hydrogen thermal reduction, and is turned into a fine alloy powder having a body-centered cubic lattice (BCC) structure at room temperature. The alloy powder obtained here is a ferromagnetic magnetic alloy containing 48.65 wt% Co and 51.38 wt% Fe.

The magnetic alloy containing 48.65 wt% Co and 51.38 wt% Fe according to Example 8 has a magnetic moment per atom of the alloy particles constituting this magnetic alloy in Bohr magneton units. 2.288 μB, and the valence electron concentration is 8.5.

That is, the valence electron concentration of the magnetic alloy of Example 7 containing 48.65 wt% Co and 51.38 wt% Fe can be defined as the average composition of pure Fe and pure Co that constitute the magnetic metal.8. It is 5. The magnetic moment per atom of a magnetic alloy with a valence electron concentration of 8.5 is 2.288 μB in Bohr magneton units from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using the magnetic alloy according to Example 6, which was prepared with a magnetic moment of 2.288 μB in Bohr magneton units as described above, as a catalyst. .

Note that the magnetic alloy according to Example 8 is used as a catalyst to generate hydrogen (H ₂ ) from ammonia borane (NH ₃ BH ₃ ), so it is used in an aqueous solution in which ammonia borane is dissolved. When dissolved in ammonia borane, the alloy is sized so that protons released from ammonia borane and located on random walking trajectories due to Brownian motion in this aqueous solution can be magnetically attracted and reliably approached to a critical distance rc sufficient to exert a magnetic influence. A material containing particles is used.

Preferably, when the magnetic alloy according to Example 8 is used as a catalyst for producing hydrogen from ammonia borane, it can exert a magnetic influence on protons on random walking trajectories due to Brownian motion in an aqueous solution, and can magnetically attract them. In order to realize the critical distance rc, it is desirable to use a material containing fine particles with a diameter of 60 nm or less, as shown in the simulation described above. ”

Then, in order to generate hydrogen from ammonia borane, the powder of the magnetic alloy is mixed with pure water to prepare a mixed liquid of the magnetic alloy, as in each of the examples described above.

For the magnetic alloy to be mixed with pure water, alloy powder classified to have a particle size of 32 μm or less and made uniform in particle size is used. 20 mg of the alloy powder, which has been classified to have a particle size of 32 μm or less, is weighed and poured into 1.0 ml of pure water. The pure water into which the alloy powder has been added is stirred using a stirrer to form a mixed liquid containing the magnetic alloy.

By using an alloy powder of a magnetic alloy that has been classified to have a particle size of 32 μm or less, it can be uniformly dissolved in pure water in a short time.

Then, an ammonia borane aqueous solution is prepared together with the magnetic alloy mixture. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

The mixed solution of the magnetic alloy prepared as described above and the aqueous solution of ammonia borane were mixed, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.

Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) achieved 1.585 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ as shown in FIG. 4).

As mentioned above, by using the magnetic alloy of Example 8, which is a magnetic metal having a magnetic moment of 2.288 μB and containing fine particles with a diameter of 60 nm, as a catalyst for hydrogen production, the hydrogen production described above can be achieved. As shown in the simulation, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.0489 nm. _The hydrogen production reaction ^rate (R Hydrogen production was achieved at a practical rate with _HER ) of 1.585 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ .

The magnetic alloy according to Example 8 is suitable for cost reduction by increasing the content ratio of Fe and making it possible to efficiently generate hydrogen from a hydrogen-containing compound such as ammonia borane while increasing the reduction in Co. .

(Comparative example 1)
In Comparative Example 1, hydrogen was generated using pure Ni metal powder as a catalyst for generating hydrogen from ammonia borane.

The pure Ni metal powder used as a catalyst here is obtained by evaporating an aqueous nickel acetate solution containing nickel ions to dryness, thermally decomposing the dried product to produce an oxide, and then reducing the thermally decomposed oxide with hydrogen heat. It is made by The pure Ni metal powder produced here has a face-centered cubic (FCC) structure at room temperature.

The pure Ni metal powder has a valence electron concentration of 10, as shown in FIG. 4, because Ni has eight electrons in 3d and two electrons in 4s in its atomic structure.

The magnetic moment per atom of Ni with a valence electron concentration of 10 is assumed to be 0.6 μB in units of Bohr magneton from the Slater-Pauling magnetic moment curve shown in FIG.

Using the pure Ni metal powder obtained here as a catalyst, hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) according to the following procedure.

Note that pure Ni metal powder is used as a catalyst to generate hydrogen (H ₂ ) from ammonia borane (NH ₃ BH ₃ ), so when it is dissolved in an aqueous solution containing ammonia borane, it is released from ammonia borane. In this aqueous solution, particles containing Ni particles are used, which are sized so that they can reliably approach to a critical distance rc sufficient to magnetically attract and exert a magnetic influence on protons that are on a random walking trajectory due to Brownian motion.

When this pure Ni metal powder is used as a catalyst to generate hydrogen from ammonia borane, it achieves a critical distance rc that can magnetically influence and magnetically attract protons on random walking trajectories due to Brownian motion in an aqueous solution. Therefore, as shown in the simulation described above, a material containing fine particles having a diameter of 60 nm or less is used.

In order to generate hydrogen from ammonia borane, a mixed solution of pure Ni metal powder mixed with pure water is prepared in the same manner as in each of the above embodiments.

As the pure Ni metal powder to be mixed with pure water, powder classified to have a particle size of 32 μm or less is used. 20 mg of the metal powder classified to have a particle size of 32 μm or less was weighed and poured into 1.0 ml of pure water. The pure water into which the pure Ni metal powder has been added is stirred using a stirrer to form a liquid mixture containing the pure Ni metal powder.

Then, together with a mixed solution of pure Ni and metal powder, an aqueous solution of ammonia borane is prepared. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the mixed solution of metal powder made of pure Ni prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) was 1.199 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ , as shown in FIG.

As mentioned above, by using pure Ni metal powder with a magnetic moment of 1.199 μB and containing fine particles with a diameter of 60 nm as a catalyst for hydrogen production, it is possible to perform the hydrogen production simulation described above. As shown, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.031745 nm, and this critical distance rc is 0.031745 nm. Hydrogen production reaction rate (R _{HER )} in which hydrogen ions (H) ⁺ , that is, protons existing within a distance rc, approach a magnetic metal containing fine alloy particles with a diameter of 60 nm to produce hydrogen (H ₂ ) gas. was 1.199 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹ .

The magnetic moment of the metal powder made of pure Ni is as small as 0.6 μB, and the critical distance Rc for protons to change from the aforementioned Brownian motion to the approach orbit where they are attracted to the pure Ni metal particles is also small, and as a result, hydrogen production The reaction rate (R _HER ) is also lower than that of the magnetic metals shown in Examples 1 to 8, making it impractical to use as a catalyst for producing hydrogen from a hydrogen-containing compound.

(Comparative example 2)
In Comparative Example 2, hydrogen was produced using pure Fe metal powder as a catalyst for producing hydrogen from ammonia borane.

The pure Fe metal powder used as a catalyst here is obtained by evaporating an aqueous iron nitrate solution containing iron ions to dryness, thermally decomposing the dried product to produce an oxide, and then reducing the thermally decomposed oxide with hydrogen heat. It is made by The pure Fe metal powder produced here has a body-centered cubic lattice (BCC) structure at room temperature. As shown in FIG. 4, the pure Fe metal powder has six electrons in 3d and two electrons in 4s in the Fe atomic structure, so that the valence electron concentration is 8.

The magnetic moment per Fe atom with a valence electron concentration of 8 is assumed to be 2.2 μB in units of Bohr magneton from the Slater-Pauling magnetic moment curve shown in FIG.

Using this metal powder as a catalyst, hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) according to the following procedure.

Note that pure Fe metal powder is used as a catalyst to generate hydrogen (H ₂ ) from ammonia borane (NH ₃ BH ₃ ), so when it is dissolved in an aqueous solution containing ammonia borane, it is released from ammonia borane. In this aqueous solution, particles containing Fe particles are used that have a size that allows them to reliably approach to a critical distance rc sufficient to magnetically attract protons on random walking trajectories due to Brownian motion and exert a magnetic influence.

In this example, in order to achieve a critical distance rc that can magnetically influence and magnetically attract protons on random walking trajectories due to Brownian motion in an aqueous solution, the pure Fe metal powder has a diameter as shown in the simulation described above. A material containing fine particles having a diameter of 60 nm or less is used.

In order to generate hydrogen from ammonia borane, a mixed solution in which pure Fe metal powder is dissolved in pure water is prepared in the same manner as in Comparative Example 1.

As the pure Fe metal powder to be mixed with pure water, a powder classified to have a particle size of 32 μm or less and made uniform in particle size is used. 20 mg of the metal powder classified to have a particle size of 32 μm or less was weighed and poured into 1.0 ml of pure water. The pure water into which the pure Ni metal powder has been added is stirred using a stirrer to form a liquid mixture containing the pure Ni metal powder.

Then, together with a mixed solution of pure Fe and metal powder, an aqueous solution of ammonia borane is prepared. An ammonia borane aqueous solution was prepared by mixing 0.5 mmol of ammonia borane powder with 1.5 ml of pure water.

1.0 ml of the mixed solution of the metal powder made of pure Ni produced as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.
Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) was 1.071 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ , as shown in FIG. 4.

As mentioned above, by using a pure Fe metal powder having a magnetic moment of 2.2 μB and containing fine particles with a diameter of 60 nm as a catalyst for hydrogen production, it is possible to perform the hydrogen production simulation described above. As shown, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.04776 nm, and this critical distance rc is 0.04776 nm. Protons existing within a distance rc were brought close to pure Fe metal particles to generate hydrogen (H ₂ ) gas. The hydrogen production reaction rate (R _HER ) at this time was 1.071 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ .

The metal powder made of pure Fe has a magnetic moment of 2.2 μm, a critical distance rc of 0.04776 nm, and has a magnetic property equal to or greater than that of the magnetic metal made of Fe-Co in Example 1 and Examples 6 to 8. Although the magnetic alloys had the moment and the critical distance rc, the hydrogen production reaction rate (R _HER ) was smaller than that of the magnetic alloys according to Examples 1 to 8.

When pure Fe metal powder was used as a catalyst, red rust was observed during the process of generating hydrogen from ammonia borane. This appears to be because pure Fe has a high affinity for oxygen, and oxidation progressed during the process of generating hydrogen from ammonia borane, deteriorating the catalyst function.

Therefore, pure Fe metal powder, although theoretically having a large magnetic moment and critical distance, cannot be used as a catalyst for producing hydrogen from hydrogen-containing compounds including ammonia borane.

(Comparative example 3)
Comparative Example 3 shows an example in which hydrogen was produced from ammonia borane using pure Co metal powder as a catalyst.

The pure Co metal powder used as a catalyst here is obtained by evaporating an aqueous cobalt acetate solution containing cobalt ions to dryness, thermally decomposing the dried product to produce an oxide, and then reducing the thermally decomposed oxide with hydrogen heat. It is made by The pure Co metal powder produced here has a hexagonal close-packed lattice (hcp) structure at room temperature. As shown in FIG. 4, pure Co metal powder has a valence electron concentration of 9 by having 7 electrons in 3d and 2 electrons in 4s in the atomic structure of Co.

The magnetic moment per atom of Co with a valence electron concentration of 9 is assumed to be 1.7 μB in units of Bohr magneton from the Slater-Pauling magnetic moment curve shown in FIG.

Hydrogen (H ₂ ) gas was generated from ammonia borane (NH ₃ BH ₃ ) using pure Co metal powder with a magnetic moment of 1.7 μB in Bohr magneton units as a catalyst.

Note that pure Co metal powder is used as a catalyst to generate hydrogen (H ₂ ) from ammonia borane (NH ₃ BH ₃ ), so when it is dissolved in an aqueous solution containing ammonia borane, it is released from ammonia borane. In this aqueous solution, particles containing Co particles are used that have a size that allows them to reliably approach to a critical distance rc sufficient to magnetically attract protons on random walking trajectories due to Brownian motion and exert a magnetic influence.

In this example, the pure Co metal powder has a diameter of 60 nm or less, as shown in the above simulation, in order to achieve a critical distance rc that can magnetically attract protons by exerting a magnetic influence on them in a random walking trajectory due to Brownian motion. A material containing fine particles is used.

In order to generate hydrogen from ammonia borane, a mixed solution of pure Co metal powder mixed with pure water is prepared in the same manner as in each of the above embodiments.

As the pure Co metal powder to be mixed with pure water, powder classified to have a particle size of 32 μm or less is used. 20 mg of the metal powder classified to have a particle size of 32 μm or less was weighed and poured into 1.0 ml of pure water. The pure water into which the pure Co metal powder has been added is stirred using a stirrer to form a liquid mixture containing the pure NI metal powder.

Then, together with a mixed solution of pure Co and metal powder, an aqueous solution of ammonia borane is prepared. An ammonia borane aqueous solution was prepared by dissolving 0.5 mmol of ammonia borane powder in 1.5 ml of pure water.

1.0 ml of the mixed solution of metal powder made of pure Ni prepared as described above was mixed with 1.5 ml of the ammonia borane aqueous solution, and this mixed aqueous solution was hydrolyzed.

The amount of hydrogen (H ₂ ) gas generated during this hydrolysis process was measured in terms of volume (HEV). This volume was converted into 1 mol of the magnetic metal of this example used as a catalyst. The amount of hydrogen (H ₂ ) gas generated was evaluated over time, and the hydrogen production reaction rate (R _HER ) was evaluated.

Note that the amount of hydrogen (H ₂ ) gas generated was measured at a temperature of 308K. According to the measured results, the hydrogen production reaction rate (R _HER ) was 1.071 (L(H ₂ ) min ⁻¹ (mol of M) ⁻¹⁾ , as shown in FIG. 4.

As mentioned above, by using a pure Co metal powder with a magnetic moment of 2.2 μB and containing fine particles with a diameter of 60 nm as a catalyst for hydrogen production, the hydrogen production simulation described above can be performed. As shown, the critical distance rc at which protons in a mixed aqueous solution of an ammonia borane aqueous solution and a magnetic metal aqueous solution change from a random walking trajectory due to Brownian motion to an approach trajectory toward the magnetic metal is 0.04776 nm, and this critical distance rc is 0.04776 nm. Hydrogen production reaction rate (R _{HER )} in which hydrogen ions (H) ⁺ , that is, protons existing within a distance rc, approach a magnetic metal containing fine alloy particles with a diameter of 60 nm to produce hydrogen (H ₂ ) gas. was 3.646 (L(H ₂ )min ⁻¹ (mol of M) ⁻¹ .

Pure Co metal powder can produce hydrogen from ammonia borane at a sufficiently practical hydrogen production rate and is useful as a catalyst for hydrogen production.

Pure Co metal powder is useful as a catalyst for aqueous production, but since the catalyst is entirely made of Co, which is a scarce resource, it is not only impossible to reduce the amount of Co used, but it is also expensive. Put it away.

(Evaluation of Examples and Comparative Examples)
Here, a comparative evaluation will be made regarding the production ability of hydrogen when producing hydrogen from ammonia borane using the magnetic metal of the present example and the metal powder shown in the comparative example as catalysts.

As described above, the hydrogen production rate (R _HER ) when the magnetic alloys of Examples 1 to 8 and the pure metals of Comparative Examples 1 to 3 were used as catalysts are shown in FIG. 4, as described above. In Examples 1 to 8, when the magnetic metal of Example 1 was used as a catalyst, the hydrogen production reaction rate (R _HER ) was the highest.

The magnetic metal made of the Fe-Co alloy of Example 1 and the magnetic alloys of Examples 6 to 8 made of the Fe-Co alloy of the same type as the magnetic metal of Example 1 have an increased Fe content. The hydrogen production reaction rate (R _HER ) was decreased accordingly.

Among the magnetic metals of Example 1 and Examples 6 to 8, the magnetic moment and critical distance rc of the magnetic metal of Example 8, which had the largest Fe content, were the largest.

On the other hand, the magnetic moment of the metal powder made of pure iron (Fe) shown in Comparative Example 2 is 2.2 μB, which is almost the same as that of the magnetic metal of Example 8, and the critical distance rc is also the same as that of the magnetic metal of Examples 6 to 8. It has a wavelength of 0.04776 nm, which is almost the same as that of metal.

As described above, the pure iron (Fe) metal powder has a magnetic moment and critical distance rc that are equal to or larger than the magnetic metals of Example 1 and Examples 6 to 8.

Furthermore, it has a magnetic moment and a critical distance rc that are greater than the magnetic alloys made of Ni--Co alloys of Examples 2 to 5.

However, the pure iron (Fe) metal powder of Comparative Example 2 has a high affinity for oxygen, and red rust was observed during the process of generating hydrogen from ammonia borane, deteriorating the hydrogen generation reaction rate (R _HER ). and cannot be used as a catalyst for hydrogen production.

In this way, when a magnetic alloy in which a part of Co is replaced with an iron-based metal such as Fe or Ni is used as a catalyst for hydrogen production, it cannot be evaluated only by the magnetic moment and critical distance rc.

When using this type of magnetic alloy as a catalyst for hydrogen production, it is desirable that the catalyst function not be degraded by oxidation or the like during the hydrogen production process.

In particular, when using a magnetic alloy in which a portion of Co is replaced with Fe, which has a high affinity for oxygen and is easily oxidized, as a catalyst, instead of focusing only on the magnetic moment and critical distance rc required for hydrogen production, It is also necessary to consider factors that degrade the catalyst's function during the hydrogen production process.

Therefore, when a magnetic alloy made of Fe--Co is used as a catalyst for hydrogen generation, it is desirable to configure it so that it does not oxidize during the hydrogen generation process and cause rust, especially red rust.

In the magnetic metal made of Fe--Co proposed here, it is desirable that the Fe content be 50 wt% or less in terms of total weight ratio. The magnetic metal of Example 8 has an Fe content of 48.65 wt% in terms of total weight ratio, but rust due to oxidation that significantly deteriorates the hydrogen production rate (R _HER ) during the hydrogen production process is avoided. Could not confirm.

In addition, in the case of a magnetic metal made of Fe--Co, when the content of Fe is 52 wt% in total weight ratio, the average magnetic moment is 2.3 μB.

Since the magnetic alloy used as the hydrogen production catalyst according to the present invention is hydrophilic, it is useful as a catalyst when ammonia borane is mixed and dissolved in pure water for hydrolysis.

Claims (6)

A hydrogen production catalyst used for producing hydrogen from ammonia borane (NH ₃ BH ₃ ),
Made of a magnetic alloy containing ferromagnetic cobalt (Co) and either iron (Fe) or nickel (Ni),
The magnetic alloy is an alloy containing 92 to 85 mol% of the cobalt (Co) and 8 to 15 mol% of the iron (Fe), or an alloy containing 96 to 92 mol% of the cobalt (Co) and 4 to 4 mol% of the nickel (Ni). ~ 8 mol% of the alloy, and the average magnetic moment per atom of the alloy particles constituting the magnetic alloy is in the range of 1.55 to 1.87 μB in Bohr magneton units.
A hydrogen production catalyst characterized by: A method for producing a hydrogen production catalyst used for producing hydrogen from ammonia borane (NH ₃ BH ₃ ), the method comprising:
The catalyst is made of a magnetic alloy containing cobalt (Co) and either iron (Fe) or nickel (Ni),
The magnetic alloy is
A mixed aqueous solution is prepared by mixing an aqueous solution of cobalt acetate containing cobalt ions, an aqueous solution of an aqueous solution of iron nitrate containing iron ions, and an aqueous solution of nickel acetate containing nickel ions,
The mixed aqueous solution is evaporated to dryness or spray-dried to produce a dried product,
Next, the dried material is heat-treated and thermally decomposed to produce an oxide,
A method for producing a catalyst for hydrogen production, characterized in that the oxide is produced by reducing the oxide with hydrogen in a hydrogen atmosphere. A mixed aqueous solution in which the cobalt acetate aqueous solution and the iron nitrate aqueous solution are mixed contains 92 to 85 mol% of a cobalt component and 8 to 15 mol% of an iron component. Item 2. A method for producing a catalyst for hydrogen production according to item 2. A mixed aqueous solution in which the cobalt acetate aqueous solution and the nickel acetate aqueous solution are mixed contains 96 to 85 mol% of a cobalt component and 4 to 15 mol% of a nickel component. 2. The method for producing a catalyst for hydrogen production according to 2. The dried product produced by drying the mixed aqueous solution is heat-treated in an oxygen atmosphere at 500° C. to 600° C. to form an oxide,
3. The method for producing a catalyst for hydrogen production according to claim 2, wherein the oxide is reduced with hydrogen in a hydrogen atmosphere at 750°C to 850°C. A method for producing hydrogen by producing hydrogen from ammonia borane (NH ₃ BH ₃ ), the method comprising:
Producing an aqueous solution in which the magnetic catalyst for hydrogen production according to claim 1 and ammonia borane (NH ₃ BH ₃ ) are dissolved and mixed,
A method for producing hydrogen, characterized in that the aqueous solution is then hydrolyzed to generate hydrogen gas (H ₂ ) from the ammonia borane (NH ₃ BH ₃ ).