Catalyst for hydrogen production, method for producing the same, and method for producing hydrogen

Abstract

To provide high-efficiency and stable production of hydrogen gas (H2(g)) from ammonia borane (NH3BH3).SOLUTION: A catalyst for generating hydrogen from NH3BH3 is composed of a tungsten carbide (WC) in which Co-Fe alloy nanocrystals are solid-solved into the WC lattice to impart ferromagnetism. The tungsten carbide is mixed into an aqueous solution of NH3BH3 to hydrolyze the NH3BH3. Here, the NH3BH3 is adsorbed onto the WC surface and cleaved to release protons (H+). Magnetic dipole interaction between the protons (H+) and the electron spins from the Co-Fe alloy nanocrystals induces accumulated reduction of the protons (H+), thereby generating hydrogen molecules (H2). Magnetic repulsive interaction between the Co-Fe alloy nanocrystals and the diamagnetic hydrogen molecules (H2) suppresses oscillations in the temporal change of the time derivative (d2Sirr / dt2) of the entropy production rate (dSirr / dt) of the irreversible process, thereby enabling stable hydrogen generation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a catalyst for producing hydrogen and a method for producing the same, and further to a method for producing hydrogen using the catalyst for producing hydrogen. [Background technology]

[0002] BACKGROUND ART Hydrogen has been attracting attention as an energy source that can prevent environmental destruction, and fuel cells that use hydrogen as fuel have attracted attention and are now in practical use.

[0003] Hydrogen is in a gaseous phase under normal temperature and pressure conditions, and the volume of a given reaction volume is several hundred to a thousand times larger than that of the solid phase. Furthermore, hydrogen is explosive, making it difficult to safely store large quantities of hydrogen. To overcome these problems associated with hydrogen gas and ensure safe and easy handling, hydrogen gas obtained by reforming natural gas, methanol, gasoline, etc. is used as fuel for fuel cells.

[0004] This type of fuel not only poses safety problems, but also does not generate sufficient electromotive force when used as fuel for fuel cells, making it impossible to achieve sufficient performance as a power supply source.

[0005] In view of the problems inherent in conventional hydrogen-containing media, extensive research has been conducted into fuels that are safe, easy to handle, and capable of generating sufficient electromotive force when used as fuel for fuel cells. Ammonia borane (NH3BH3), a hydrogen-containing compound with a high hydrogen concentration, has been proposed as one such fuel (Patent Documents 1 and 2).

[0006] The hydrogen contained in ammonia borane (NH3BH3) is produced by adding platinum (Pt) as a catalyst to an aqueous solution in which ammonia borane (NH3BH3) is dissolved, and then hydrolyzing the aqueous solution.

[0007] Conventionally, precious metals such as platinum (Pt) used as catalysts are scarce and expensive, making it difficult to produce hydrogen from ammonia borane (NH3BH3) at low cost and stably. Therefore, the applicant of the present application has proposed catalysts that are alternatives to precious metals such as platinum (Pt) (Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-286549 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-176556 [Patent Document 3] Japanese Patent Publication No. 2023-61564 [Patent Document 4] Patent No. 7417026 Summary of the Invention [Problem to be solved by the invention]

[0009] In the case of fuel cells used as a driving source for mobile devices such as automobiles and fuel cells used as a power source for consumer portable terminal devices, it is desirable to generate hydrogen inexpensively, stably, and efficiently from hydrogen-containing compounds that store hydrogen at high concentrations, and further to achieve miniaturization of the battery itself. [Means for solving the problem]

[0010] The inventors have focused on the catalytic action and function of platinum (Pt), which is used in producing hydrogen from hydrogen-containing compounds, particularly ammonia borane (NH3BH3), and have conducted extensive research, resulting in the creation of a hydrogen production catalyst that is capable of achieving catalytic action equivalent to or even greater than that of platinum (Pt).

[0011] In particular, the inventors have conducted extensive research into the characteristics of platinum (Pt), which is used as a catalyst, and as a result have noticed that platinum (Pt) has magnetic properties, and have completed a catalyst for hydrogen production that is cheaper than platinum (Pt) and can be obtained or supplied stably.

[0012] The hydrogen production catalyst proposed here is a catalyst that can be used in place of platinum (Pt), and is characterized by consisting of tungsten carbide (WC) in which ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals are dissolved in a solid solution within the lattice of tungsten carbide, and which is made ferromagnetic by the application of an internal magnetic field. The tungsten carbide that constitutes this catalyst is characterized by having an internal magnetic field imparted to it by encapsulating cobalt-iron (Co-Fe) alloy nanocrystals composed of ferromagnetic cobalt (Co) at 99.5 to 91.5 mol % and iron (Fe) at 0.5 to 8.5 mol %.

[0013] The tungsten carbide used as the proposed catalyst for hydrogen production is preferably a fine powder with a particle size of 32 μm or less in order to stably generate hydrogen (H2).

[0014] The tungsten carbide that constitutes the hydrogen production catalyst used to generate hydrogen (H2) from ammonia borane (NH3BH3) is produced through the following process.

[0015] First, a mixed aqueous solution is prepared by mixing a tungsten component with a ferromagnetic cobalt component and an iron component, and then the mixed aqueous solution is evaporated to dryness or spray-dried to produce a solid containing the cobalt component and the iron component. This solid is then thermally decomposed to produce an oxide powder, or further hydrogen-thermally reduced to produce a cobalt-iron (Co-Fe) alloy solid solution tungsten alloy powder.

[0016] The cobalt-iron (Co-Fe) alloy solid solution tungsten alloy powder is then carbonized to produce tungsten carbide that contains ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals and is made ferromagnetic by the application of an internal magnetic field.

[0017] In the carbonization process of the cobalt-iron (Co-Fe) alloy solid solution tungsten alloy powder, tungsten complex carbides (W6(Co-Fe)6C, (Co-Fe)2W4C) are produced along with tungsten carbides that contain ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals and are made ferromagnetic by the application of an internal magnetic field.

[0018] The mixed aqueous solution used to produce the tungsten carbide is a mixture of a cobalt-iron (Co-Fe) alloy component, which is a mixture of cobalt (Co) in a ratio of 99.5 to 91.5 mol% and iron (Fe) in a ratio of 0.5 to 8.5 mol%, and a tungsten component in a molar ratio of 20:80.

[0019] The tungsten carbide, which functions as a catalyst and has the above-mentioned structure, is mixed with an aqueous solution of ammonia borane (NH3BH3). The aqueous solution of ammonia borane (NH3BH3) mixed with the tungsten carbide is hydrolyzed, causing the tungsten carbide to function as a catalyst and generating hydrogen gas (H2(g)) from the ammonia borane (NH3BH3).

[0020] When generating hydrogen gas from ammonia borane (NH3BH3) by hydrolyzing an aqueous solution containing dissolved ammonia borane mixed with tungsten carbide, which acts as a catalyst, the repulsive interaction between the diamagnetic hydrogen gas and the ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals encapsulated in the tungsten carbide causes the hydrogen gas (H2(g)) to desorb from the surface of the tungsten carbide.

[0021] When producing hydrogen (H2) from ammonia borane (NH3BH3) using the hydrogen production catalyst made of tungsten carbide described above, an aqueous solution is prepared by mixing tungsten carbide with an aqueous solution of ammonia borane (NH3BH3). When this aqueous solution is hydrolyzed, ammonia borane (NH3BH3) is adsorbed onto the surface of tungsten carbide (WC) that constitutes the tungsten carbide, which functions as a catalyst, and is split into protons (H +) is released. Here, the released proton (H + ) and the electron spins from the ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals encapsulated in tungsten carbide, causing protons (H + ) and reduce it to generate diamagnetic hydrogen molecules (H2). Here, the magnetic repulsive interaction between the ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals and the diamagnetic hydrogen molecules (H2) causes the time derivative (dSirr / dt) of the entropy generation rate of the irreversible process to 2 Sirr / dt 2 The unstable oscillation of the time-dependent changes in the cobalt-iron (Co-Fe) alloy nanocrystal surface is suppressed, and hydrogen molecules (H2) are desorbed from the surface to generate hydrogen gas (H2(g)). [Effects of the Invention]

[0022] The tungsten carbide proposed here, which encapsulates cobalt-iron (Co-Fe) alloy nanocrystals and is subjected to an internal magnetic field, is hydrophilic and therefore suitable for use as a catalyst in the hydrolysis of ammonia borane (NH3BH3), a hydrogen-containing compound that enables high-concentration hydrogen storage.

[0023] This hydrogen production catalyst using tungsten carbide enables highly efficient production of hydrogen gas (H2(g)) from the hydrogen-containing compound ammonia borane (NH3BH3). In particular, the efficiency of hydrogen gas (H2(g)) production is equal to or even exceeds that achieved when platinum (Pt) is used as a catalyst.

[0024] Furthermore, hydrogen production catalysts using tungsten carbide improve the conversion rate of hydrogen gas (H2(g)) produced by hydrolysis of ammonia borane (NH3BH3), enabling stable and highly efficient production of hydrogen gas (H2(g)), and can even contribute to the realization of smaller fuel cells themselves.

[0025] The catalyst using tungsten carbide described above does not use a precious metal such as platinum (Pt), but uses a material that is an abundant resource with no risk of depletion, making it possible to supply it cheaply and stably.

[0026] In addition, the proposed catalyst reduces the time derivative (dSirr / dt) of the entropy production rate of the irreversible process that produces hydrogen gas (H2(g)). 2 Sirr / dt 2 This suppresses unstable oscillations in the time-dependent changes of hydrogen (H2), enabling stable generation of hydrogen (H2).

[0027] The magnetic repulsive interaction between ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals and diamagnetic hydrogen molecules (H2) enables rapid desorption of hydrogen molecules (H2) from the surface of the cobalt-iron (Co-Fe) alloy nanocrystals, enabling highly efficient hydrogen production. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a schematic diagram showing a mechanism for producing hydrogen (H2) by hydrolyzing ammonia borane (NH3BH3) using the tungsten carbide according to the present invention as a catalyst. FIG. [Figure 2] FIG. 1 shows an energy dispersive X-ray spectroscopy (EDX) image of tungsten carbide encapsulating a cobalt-iron (Co-Fe) alloy nanocrystalline phase produced according to the present example. [Figure 3] FIG. 1 is a characteristic diagram showing the change over time in the amount of hydrogen gas generated from ammonia borane (NH3BH3) using the tungsten carbide according to this example, a reference catalyst (Pt-NPs Ball) distributed by the Catalysis Society of Japan, which is made by supporting platinum (Pt) nanoparticles on alumina nanoparticles and molding them into granules, and a catalyst (Pt-NPs) made by finely crushing this catalyst. [Figure 4]FIG. 10 is a graph showing the change over time in the time derivative (dSirr / dt) of entropy production in the irreversible process in the hydrogen evolution reaction when the tungsten carbide according to this example and Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) shown as comparative examples are used as catalysts. [Figure 5] FIG. 10 is a graph showing the change over time in the second-order time derivative (d2Sirr / dt2) of entropy production in the irreversible process in the hydrogen evolution reaction when the tungsten carbide of this example is used as a catalyst. [Figure 6] FIG. 1 shows the change over time in the second-order time derivative (dSirr / dt) of entropy production in the irreversible process in the hydrogen production reaction when Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) shown as comparative examples were used as catalysts. [Figure 7] This is a diagram that shows a schematic diagram of the mechanism by which hydrogen molecules (H2) produced by the hydrolysis of ammonia borane (NH3BH3) are desorbed as gaseous hydrogen gas. [Figure 8] 1 is a schematic diagram showing the mechanism of hydrogen (H2) production when ammonia borane (NH3BH3) is hydrolyzed using platinum (Pt) as a catalyst. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present embodiment described below is a catalyst for hydrogen production used to generate hydrogen (H) from ammonia borane (NH3BH3), a hydrogen-containing compound. This catalyst is made of tungsten carbide that contains a cobalt-iron (Co-Fe) alloy nanocrystalline phase and is given magnetic properties. This tungsten carbide is produced by carbonizing a cobalt-solubilized tungsten alloy powder in which ferromagnetic cobalt (Co) and iron (Fe) are forcedly dissolved in a non-equilibrium solid solution in a tungsten carbide (WC) lattice.

[0030] The cobalt (Co) and iron (Fe) solid solution tungsten alloy powder used to prepare the tungsten carbide of this embodiment is prepared by using the mixed aqueous solution that is obtained by mixing the aqueous solution of ammonium tungstate that contains tungsten ions with the aqueous solution of cobalt acetate that contains cobalt ions and the aqueous solution of iron nitrate that contains iron ions.

[0031] This mixed aqueous solution is preferably a mixture of a cobalt-iron (Co-Fe) alloy component, which is a mixture of 99.5 to 91.5 mol% of cobalt (Co) and 0.5 to 8.5 mol% of iron (Fe), and a tungsten component in a molar ratio of 20:80.

[0032] The mixed aqueous solution is evaporated to dryness or spray-dried to produce a dried product. The dried product is then thermally decomposed into oxides. The thermal decomposition of the dried product into oxides is carried out by holding it in an oxygen atmosphere at 500°C to 600°C, preferably at 570°C, for about 2 hours.

[0033] The oxide produced by pyrolyzing the dried product is reduced with hydrogen to produce a cobalt (Co) and iron (Fe) dissolved tungsten oxide powder. This hydrogen reduction is carried out by holding the oxide obtained in the above process in a hydrogen atmosphere at 750°C to 850°C, preferably at 800°C, for about 3 hours. This oxide is reduced with hydrogen to produce a cobalt (Co) and iron (Fe) dissolved tungsten alloy powder.

[0034] The cobalt (Co) and iron (Fe) solid solution tungsten alloy powder produced here is a non-equilibrium forced solid solution of cobalt (Co) and iron (Fe) in the tungsten (W) lattice.

[0035] The cobalt (Co) and iron (Fe) solid solution tungsten alloy powder prepared as described above is carbonized to form tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase and having an internal magnetic field applied thereto. This tungsten carbide having an internal magnetic field applied thereto is used as a catalyst for hydrogen production, which is used to generate hydrogen (H2) from the hydrogen-containing compound ammonia borane (NH3BH3).

[0036] The carbonization process of the cobalt (Co) and iron (Fe) solid solution tungsten alloy powder is carried out by heating in a carbon dioxide (CO2) gas atmosphere. For example, after the cobalt (Co) and iron (Fe) solid solution tungsten alloy powder is placed in a reactor, CO2 gas is introduced into the reactor, and the reactor is heated to an atmosphere of about 900°C for about 20 hours.

[0037] However, in the case of cobalt (Co) and iron (Fe) solid solution tungsten alloy powder, if the content ratio of cobalt (Co) and iron (Fe) relative to tungsten (W) is excessive, carbonization is inhibited, and it has been difficult to produce tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase. In the state of the above-mentioned mixed aqueous solution, if the total of the cobalt (Co) component and the iron (Fe) component exceeds 30 mol%, carbonization is inhibited, and it has been impossible to produce tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase.

[0038] Furthermore, when the ferromagnetic cobalt (Co) and iron (Fe) components are less than 1 mol% in the mixed aqueous solution, the proportion of cobalt (Co) and iron (Fe) components dissolved in the tungsten carbide is insufficient, making it impossible to obtain high catalytic activity. This is thought to be because the tungsten carbide containing the cobalt-iron (Co-Fe) alloy nanocrystalline phase is not sufficiently magnetized, preventing the magnetic catalytic properties from being obtained. Therefore, it is insufficient for use as a catalyst for hydrogen production, which is used to generate hydrogen (H2) from ammonia borane (NH3BH3).

[0039] Therefore, a mixed aqueous solution of a cobalt-iron (Co-Fe) alloy component, which is a mixture of cobalt (Co) at a ratio of 99.5 to 91.5 mol% and iron (Fe) at a ratio of 0.5 to 8.5 mol%, and a tungsten (W) component at a molar ratio of 20:80, is used as a starting material.

[0040] This tungsten carbide has a structure in which ferromagnetic cobalt-iron (Co-Fe) nanocrystals are encapsulated within a tungsten carbide (WC) framework. The cobalt-iron (Co-Fe) nanocrystals are polycrystalline bodies with a structure in which cobalt (Co) and iron (Fe) atoms are crystalline, with grain sizes ranging from several nanometers to several tens of nanometers.

[0041] The tungsten carbide according to this embodiment, which is used as a catalyst for hydrogen production, is preferably pulverized to a particle size of 32 μm or less, for example, to form a mixed aqueous solution in which it is uniformly mixed with an aqueous solution of ammonia borane (NH3BH3).

[0042] The tungsten carbide according to the present embodiment, produced through the above-described process, contains a ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystalline phase within a tungsten carbide (WC) framework, and exhibits ferromagnetic properties, as indicated by a hysteresis loop in its magnetic field-magnetization curve. Ferromagnetic tungsten carbide achieves high catalytic activity and functions effectively as a hydrogen production catalyst used to generate hydrogen (H) from ammonia borane (NHBH).

[0043] To generate hydrogen (H2) from ammonia borane (NH3BH3) using the above-mentioned tungsten carbide as a catalyst, a mixture of this tungsten carbide and water is mixed with an aqueous solution of ammonia borane in which crystalline ammonia borane (NH3BH3) is dissolved. When this aqueous solution of ammonia borane mixed with tungsten carbide is hydrolyzed, hydrogen gas (H2(g)) is generated according to the following formula (1).

[0044] NH3BH3+2H2O=NH4 + +BO2- +3H2···(1)

[0045] The aqueous solution of ammonia borane (NH3BH3) may be prepared by directly adding ammonia borane to a mixed solution containing tungsten carbide and dissolving it therein.

[0046] Tungsten carbide encapsulating a nanocrystalline cobalt-iron (Co-Fe) alloy phase acts as a catalyst in the hydrolysis of aqueous solutions of ammonia borane (NH3BH3), promoting the production of hydrogen (H2) from the borane.

[0047] Here, the mechanism by which the above-mentioned tungsten carbide functions as a catalyst when ammonia borane (NH3BH3) is hydrolyzed to produce hydrogen (H2) will be described with reference to FIG.

[0048] When an aqueous solution (NH3BH3(aq)) containing the crystalline solid ammonia borane (NH3BH3(cr)) is mixed with an aqueous solution containing tungsten carbide encapsulating a cobalt-iron (Co-Fe) alloy nanocrystalline phase, the ammonia borane (NH3BH3) molecules are attracted into the WC skeleton by the attractive interaction of the WB bond. Then, the BN bond, which is the bond between boron (B) and nitrogen (N) that make up ammonia borane (NH3BH3), is broken, generating the stable molecule NH3(aq) and the unstable molecule BH3(aq). At this time, protons (H + ) is generated. The generated protons (H + The nuclear spins of the cobalt (Co) align to cancel out the electron spins of the cobalt (Co), producing hydrogen gas (H2(g)). Hydrogen gas (H2(g)) is diamagnetic, and therefore undergoes repulsive interactions with the ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystalline phase. As a result, the time derivative (d 2 Sirr / dt 2This suppresses unstable oscillations in the time-dependent changes of hydrogen gas (H2(g)), enabling stable generation of hydrogen gas (H2(g)). Furthermore, rapid desorption of hydrogen molecules (H2) from the surface of the cobalt-iron (Co-Fe) alloy nanocrystals is realized, enabling highly efficient production of hydrogen (H2). [Example]

[0049] Next, specific examples of the catalyst for producing hydrogen according to the present invention will be described. This example describes tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase, which is used as a catalyst for hydrogen production. The tungsten carbide is produced by carbonizing a cobalt (Co) and iron (Fe)-doped tungsten alloy powder. The cobalt (Co) and iron (Fe)-doped tungsten alloy powder used to produce the tungsten carbide is prepared using a mixed aqueous solution of ammonium tungstate containing tungsten ions, cobalt acetate containing cobalt ions, and iron nitrate containing iron ions. This mixed aqueous solution was prepared by mixing an aqueous solution of ammonium tungstate with an aqueous solution of cobalt acetate and iron nitrate. The mixed aqueous solution was prepared by mixing an aqueous solution of ammonium tungstate with an aqueous solution of cobalt acetate and iron nitrate, so that the molar ratio of the cobalt-iron (Co-Fe) alloy component (92 mol% cobalt (Co) and 8 mol% iron (Fe)) to the tungsten component was 20:80.

[0050] This mixed aqueous solution is evaporated to dryness to produce a dried product. This dried product is then held in an oxygen atmosphere at 570°C for two hours to thermally decompose into oxides. The thermally decomposed oxides are then held in a hydrogen atmosphere at 800°C for three hours to undergo hydrogen reduction. This oxide is then hydrogen-reduced to produce a cobalt-iron (Co-Fe) solid solution tungsten alloy powder in which cobalt is forcedly dissolved in a non-equilibrium state.

[0051] 1 g of the obtained cobalt-doped tungsten alloy powder was placed in a reactor, carbonized by introducing carbon dioxide (CO2) gas into the reactor and heating the reactor to 900°C and maintaining the temperature for 24 hours.

[0052] When performing this carbonization treatment, since it is impossible to directly carbonize using CO2 gas, a compressed compact of Al-Fe alloy powder was placed in the reactor beforehand, and this compact was carbonized as an agent for converting CO2 gas to carbon monoxide (CO) gas.

[0053] The cobalt and iron-dissolved tungsten alloy powder carbonized through the above-mentioned treatment process is converted into tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase. An energy dispersive X-ray spectroscopy (EDX) image of this tungsten carbide containing a cobalt-iron (Co-Fe) alloy nanocrystalline phase is shown in Figure 2.

[0054] In Figure 2, Area #1 is a cobalt-iron (Co-Fe) alloy nanocrystalline phase (92Co-8Fe) with a cobalt (Co) to iron (Fe) molar ratio of 92:8. Area #2 is a tungsten carbide (WC) skeleton. Area #3 is a region where tungsten complex carbides (W6(Co-Fe)6C and (Co-Fe)2W4C) are mixed. Area #4, like Area #2, is a tungsten carbide (WC) skeleton.

[0055] Using the obtained Co-WC solid solution phase-encapsulated tungsten carbide as a catalyst, hydrogen gas (H2(g)) was produced from ammonia borane (NH3BH3) through the process shown below.

[0056] First, the powder of tungsten carbide encapsulated in a nanocrystalline phase of a cobalt-iron (Co-Fe) alloy, prepared through the above process, was mixed with pure water to prepare a mixed solution. This mixed solution was prepared by weighing out 20 mg of tungsten carbide encapsulated in a nanocrystalline phase of a cobalt-iron (Co-Fe) alloy with a particle size of 32 μm or less, adding it to 1 ml of pure water, and stirring it with a stirrer.

[0057] Here, the tungsten carbide encapsulating the nanocrystalline phase of a cobalt-iron (Co-Fe) alloy was pulverized and classified to a particle size of 32 μm or less. Hereinafter, the tungsten carbide encapsulating the nanocrystalline phase of a cobalt-iron (Co-Fe) alloy will be abbreviated as WC-(Co0.92-Fe0.08) carbide.

[0058] Next, 1.5 ml of 0.5 mmol of ammonia borane (NH3BH3) powder was mixed with 1.5 ml of pure water to prepare an aqueous ammonia borane solution.

[0059] The mixed solution of tungsten carbide (WC-(Co0.92-Fe0.08) carbide) prepared as described above was mixed with an aqueous solution of ammonia borane, and ammonia borane (NH3BH3) was hydrolyzed.

[0060] The amount of hydrogen gas (H2(g)) generated during this hydrolysis process was measured by volume (HEV) and converted to molar amount. The amount of hydrogen gas (H2(g)) generated was evaluated over time to evaluate the rate of the hydrogen evolution reaction (HER). The amount of hydrogen gas (H2(g)) generated was measured at a temperature of 308 K. The measurement results are shown in Figure 3, A.

[0061] The measured values ​​of the hydrogen gas (H2(g)) generation rate over time shown in Figure 3 were averaged over four runs conducted to evaluate reusability. Specifically, after the first measurement of the hydrogen gas (H2(g)) generation rate was completed, the ammonia borane solution was drained from the hydrolysis solution. The ammonia borane solution was then injected a second time, and the hydrogen gas (H2(g)) generation rate was measured again. After this was completed, the ammonia borane solution was similarly drained from the hydrolysis solution. The ammonia borane solution was then injected a third time, and the hydrogen gas (H2(g)) generation rate was measured again. After this was completed, the ammonia borane solution was drained from the hydrolysis solution. This measurement was repeated three times. After the measurement, the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) used as the catalyst was removed from the hydrolysis solution and exposed to the atmosphere for 24 hours. The extracted tungsten carbide mixture was mixed with an aqueous solution of ammonia borane to prepare an aqueous solution, which was then hydrolyzed and the amount of hydrogen gas (H2(g)) generated was measured for the fourth time.

[0062] Here, we compared the ability to produce hydrogen gas (H2(g)) from ammonia borane (NH3BH3) when using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) according to this example as a catalyst with when using a platinum (Pt)-based noble metal as a catalyst.

[0063] The catalysts used in the comparative examples were a reference catalyst (Pt-NPs(Ball)) distributed by the Catalysis Society of Japan, which consisted of platinum (Pt) nanoparticles supported on alumina nanoparticles and formed into granules, and a finely crushed catalyst (Pt-NPs(1)). Experiments on hydrogen gas (H2(g)) production using these comparative catalysts were also conducted four times to compare with the results obtained using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) used in this example.

[0064] When Pt-NPs (Ball) and Pt-NPs (1), which are given as comparative examples, are used as catalysts, these catalysts are mixed with pure water to prepare mixed water, similar to the case of using WC-(Co0.92-Fe0.08) carbide in this example. These mixed waters are prepared by adding 20 mg of Pt-NPs (Ball) or Pt-NPs (1) powder to 1 ml of pure water and stirring with a stirrer.

[0065] Pt-NPs (1), which are finely crushed granular Pt-NPs (balls), were discharged from the mixed aqueous solution along with the ammonia borane (NH3BH3) solution discharged during each experiment to generate hydrogen gas (H2(g)) by hydrolysis, and a decrease in the amount of hydrogen gas (H2(g)) generated was observed. Therefore, to clarify the inherent catalytic activity of platinum (Pt) when using Pt-NPs as a catalyst, new finely crushed granular Pt-NPs (balls) were used each time the amount of hydrogen gas (H2(g)) generated was measured. This is referred to as Pt-NPs (2). This new crushed Pt-NPs (2) was also mixed with pure water each time it was used as a catalyst, forming the mixed water. This mixed water was also prepared by adding 20 mg of Pt-NPs (2) powder to 1 ml of pure water and stirring with a stirrer.

[0066] To hydrolyze ammonia borane (NH3BH3), ammonia borane (NH3BH3) powder was mixed with pure water to prepare an aqueous solution of ammonia borane (NH3BH3). This solution was prepared by mixing 1.5 ml of 0.5 mmol of ammonia borane (NH3BH3) powder with 1.5 ml of pure water.

[0067] Then, the mixtures of the aforementioned Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) were mixed with an aqueous solution of ammonia borane to hydrolyze ammonia borane (NH3BH3).

[0068] The amount of hydrogen gas (H2(g)) generated during this hydrolysis process was measured in terms of volume (HEV) and converted to molar amount. The amount of hydrogen gas (H2(g)) generated was evaluated over time to evaluate the rate of the hydrogen evolution reaction (HER). The amount of hydrogen gas (H2(g)) generated was measured at a temperature of 308 K. The measurement results are shown in Figure 3. The measurement results when Pt-NPs (Ball) was used as the catalyst are shown in B in Figure 3. The measurement results when Pt-NPs (1) was used as the catalyst are shown in C in Figure 3. The measurement results when Pt-NPs (2) was used as the catalyst are shown in D in Figure 3.

[0069] The amount of hydrogen gas (H(g)) produced by hydrolyzing ammonia borane (NH3BH3) using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example and the comparative examples Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) as catalysts was evaluated by normalizing it to the mass of hydrogen product per specific surface area of ​​each catalyst. That is, for Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2), it was evaluated as the mass of hydrogen product per specific surface area of ​​platinum (Pt) nanoparticles supported on alumina nanoparticles.

[0070] First, considering reusability, we compared the amount of hydrogen gas (H2(g)) generated when using WC-(Co0.92-Fe0.08) carbide, Pt-NPs (Ball), and Pt-NPs (1) as catalysts. As shown in Figure 3, the amount of hydrogen gas (H2(g)) generated when using WC-(Co0.92-Fe0.08) carbide in this example was nearly three times the amount of hydrogen gas (H2(g)) generated when using Pt-NPs (Ball) and Pt-NPs (1).

[0071] Next, when comparing the amount of hydrogen (H2) gas generated when the WC-(Co0.92-Fe0.08) carbide of this example was used with Pt-NPs (2), which was made by finely crushing granular Pt-NPs (balls) each time, the initial gas generation rate was similar, as shown in Figure 3. However, after 40 minutes, the amount of hydrogen gas (H2(g)) generated when WC-(Co0.92-Fe0.08) carbide was used was approximately 2.5 times that of Pt-NPs (2).

[0072] From the above, it is recognized that the WC-(Co0.92-Fe0.08) carbide of this example is superior as a catalyst to platinum (Pt)-based noble metals.

[0073] The change over time in the amount of hydrogen gas (H2(g)) produced by hydrolysis of ammonia borane (NH3BH3) was confirmed using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example and Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) given as comparative examples as catalysts.

[0074] Here, we defined the entropy production (Sirr) and entropy rate (dSirr / dt) in the hydrolysis reaction of ammonia borane (NH3BH3) shown in the above-mentioned formula (1).

[0075] The entropy production (Sirr) represents the entropy of hydrogen gas (H(g)) produced from ammonia borane (NH3BH3) through an irreversible process, and the entropy rate (dSirr / dt) is the entropy production (Sirr) differentiated with respect to time (t).

[0076] From the relationship between the amount of hydrogen (H2) gas produced by the hydrolysis of ammonia borane (NH3BH3) and the stoichiometric coefficient, the amount of NH4 produced by the hydrolysis reaction of ammonia borane (NH3BH3) shown in Equation (1) can be calculated. + (aq) and BO2 - The change in the number of moles of (aq) over time was calculated and converted into the change in the mass molar concentration b over time.

[0077] Next, the ionic strength I was evaluated using the following formula (2). m was evaluated.

[0078] JPEG2025137213000002.jpg1757

[0079] Here, z i is the valence of the ion, and b ° is the standard molality (b ° = 1 mol kg -1 ). Next, in order to evaluate the activity of the ionic species generated by the hydrolysis of ammonia borane (NH3BH3), the activity coefficient was evaluated using the Davies equation shown in the following formula (3). The applicable range of the Davies equation is 0.01 < I < 0.3. As shown in the calculation results of the ionic strength shown later, the hydrogen evolution reaction (HER) by the hydrolysis of ammonia borane (NH3BH3) described here is within the applicable range of the Davies equation.

[0080] JPEG2025137213000003.jpg17110

[0081] Next, the activity of each ionic species was evaluated from the values of the activity coefficient and the molality, and shown in the following formula (4). The affinity A was evaluated according to the definition of the affinity.

[0082] JPEG2025137213000004.jpg59115(4)

[0083] Here, Δ r G ° and p H2 are the standard reaction Gibbs energy of the hydrogen evolution reaction (HER) and the partial pressure of hydrogen, respectively. The partial pressure of hydrogen is 1.01325 bar. That is, up to the hydrogen recovery section in the hydrolysis device was regarded as the system of hydrogen generation.

[0084] The thermochemical equations for the hydrogen production reaction from the hydrolysis of ammonia borane (NH3BH3(cr)) at 298.15 K are shown in the following equations (I) to (VI).

[0085] Table 1 also lists the compounds of ammonia borane (NH3BH3(cr)), ammonia (NH3(aq)), orthoboric acid (B(OH)3(aq)), ammonium (NH4 + (aq) ), metaboric acid (BO2(aq)), H2O(l) 、 Thermodynamic quantities at 298.15 K for standard substances of N2(g) and B(cr) are shown.

[0086] The standard enthalpy of formation of ammonia borane (NH3BH3(cr)) (Δ f H ° m ) and third law entropy (S ° m ) adopted the measurement results of Shaulov et al. and Wolf et al. The standard entropy of formation (Δ f S ° m ) to the standard state hydrogen (H2(g)), nitrogen (N2(g)), and boron (B(cr)) in terms of the third law entropy (S ° m ) and the standard enthalpy of formation (Δ f H ° m ) and the standard Gibbs energy of formation (Δ f G ° m =-59.615±5.864 (kJ mol -1 )) was adopted. In addition, H2O(l), ammonia (NH3(aq)), orthoboric acid (B(OH)3(aq)), ammonium (NH4 + (aq), the standard Gibbs energy of metaboric acid (BO2(aq)) (Δ f G ° m ) cited values ​​from a data book.

[0087] The following equation (I) is the hydration reaction of ammonia borane (NH3BH3(aq)), whose thermodynamic values ​​are unknown, and its thermochemical quantities are also unknown. The following equation (II) is the hydrogen production reaction (HER) by hydrolysis of ammonia borane (NH3BH3(cr)). The sum of equations (I) and (II) can be rewritten as the following equation (III). Equation (IV) is the reaction of ammonium (NH4 + Equation (V) shows the formation of metaboric acid (BO(aq)). Equation (VI) is rewritten as the sum of these reactions, with the left side showing the initial state and the right side showing the final state.

[0088] JPEG2025137213000005.jpg88154

[0089] The standard reaction Gibbs energy (Δ f G ° m ) was used, and the temperature of the system was assumed to be approximately constant at 25°C (298.15K).

[0090] The change in thermodynamic force A / T over time was evaluated by dividing the calculated affinity A by the temperature.

[0091] The production of hydrogen gas (H2) from ammonia borane (NH3BH3) through hydrolysis is an irreversible process, and entropy is generated within the system during this process. This is defined as the entropy generation Sirr. The entropy rate (dSirr / dt) is the entropy generation (Sirr) differentiated with respect to time (t). The entropy rate (dSirr / dt) was defined by the following equation (5).

[0092] dSirr / dt=(A / T)(dξ / dt) ···(5) Here, A is the affinity and ξ indicates the reaction progress.

[0093] The enthalpy production (Sirr) was determined by integrating the entropy rate (dSirr / dt) obtained from equation (5).

[0094] Table 1 Thermodynamic quantities used to determine entropy production and their errors U. JPEG2025137213000006.jpg92168

[0095] Figure 4 shows the time-dependent change in the time derivative of entropy production (dSirr / dt) of the irreversible process in the hydrogen production reaction produced by hydrolysis of ammonia borane (NH3BH3) using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example and Pt-NPs (Ball), Pt-NPs (1), and Pt-NPs (2) as catalysts for comparison.

[0096] In FIG. 4, A shows the change in entropy generation over time when the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example is used as a catalyst, B shows the change in entropy generation over time when Pt-NPs (Ball) is used as a catalyst, C shows the change in entropy generation over time when Pt-NPs (1) is used as a catalyst, and D shows the change in entropy generation over time when Pt-NPs (2) is used as a catalyst.

[0097] As shown in Figure 4, when hydrogen was generated using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example and Pt-NPs (2) as catalysts, the entropy generation rate (dSirr / dt) decreased gradually over time. In contrast, when Pt-NPs (Ball) and Pt-NPs (1) were used as catalysts, the entropy generation rate (dSirr / dt) decreased with an oscillating pattern.

[0098] Figure 5 shows the second-order time derivative (d 2 Sirr / dt 2) over time is shown in A. Figure 6 shows the second-order time derivative (d 2 Sirr / dt 2 In Figure 6, B shows the change when Pt-NPs (Ball) was used, C shows the change when Pt-NPs (1) was used, and D shows the change when Pt-NPs (2) was used.

[0099] The second-order time derivative (d 2 Sirr / dt 2 ) decayed smoothly over time. In contrast, Pt-NPs (2), whose first-order time derivative (dSirr / dt) was smooth, showed a smooth change over time. 2 Sirr / dt 2 ) with time, it oscillated as shown in Figure 6D. The second-order time derivative (d 2 Sirr / dt 2 ) As shown in B and C in Figure 6, the time-dependent change showed oscillations similar to the first-order time derivative (dSirr / dt).

[0100] Furthermore, the mechanism by which ammonia borane (NH3BH3) is hydrolyzed to generate hydrogen (H2) using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example as a catalyst will be described in more detail with reference to Figure 1.

[0101] The tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example can be considered a platinum (Pt)-like substance, with an electron arrangement structure similar to that of platinum (Pt). WC, a platinum (Pt)-like substance, has a strong affinity for ammonia borane (NH3BH3), bringing them closer together.

[0102] Tungsten carbide (WC) brings ammonia borane (NH3BH3) close to it and simultaneously coordinates the B component in ammonia borane (NH3BH3). This is due to the strong attractive interaction between the W component in tungsten carbide (WC) and the B component in ammonia borane (NH3BH3).

[0103] When the B component in ammonia borane (NH3BH3) coordinates with the W of tungsten carbide (WC), ammonia borane (NH3BH3) begins to decompose into NH3(aq) and BH3(aq).

[0104] The unstable molecule BH3(aq) decomposes and reaches equilibrium, releasing three OH atoms from the three surrounding water molecules (H2O(l)). - ions to form B(OH)3(aq), while at the same time releasing three H + (aq) i.e., releases a proton.

[0105] Here, three OH - Three water molecules (H2O(l)) that release (aq) also release three protons.

[0106] The six protons released from both BH3(aq) and water molecules (H2O(l)) each have a nuclear spin. These protons with nuclear spin interact with the electron spins of the cobalt-iron (Co-Fe) alloy nanocrystals dissolved in the WC framework, resulting in their assembly and alignment on the surface.

[0107] BH3(aq), produced by decomposing ammonia borane (NH3BH3), releases three protons and discharges three electrons. Three OH(aq) molecules released from three water molecules (H2O(l)) also discharge three electrons. These six discharged electrons are transferred to the Co-Fe alloy nanocrystals via W atoms in the WC framework.

[0108] The six electrons transferred to the Co-Fe alloy nanocrystals reduce the protons collectively arranged on the surface of the Co-Fe alloy nanocrystals, generating six atomic radical hydrogen atoms (H).

[0109] Finally, three hydrogen molecules (H2) are produced from six radical hydrogen atoms (H). Due to space limitations, Figure 1 shows the intermediate steps in the cycle described above, where one proton is released from one BH3(aq) and one proton is released from one H2O(l), resulting in the release of two protons from each.

[0110] Furthermore, the mechanism by which the generated hydrogen molecules (H2) desorb as gaseous hydrogen gas (H2(g)) will be explained with reference to Figure 7. In Figure 7, when ammonia borane (NH3BH3) is hydrolyzed using the tungsten carbide (WC-(Co0.92-Fe0.08) carbide) of this example as a catalyst, the hydrogen gas (H2(g)) generated on the surface of the Co0.92-Fe0.08 alloy nanocrystals solid-solved in the WC lattice is diamagnetic and therefore magnetized in the opposite direction to the magnetic field of the ferromagnetic Co0.92-Fe0.08. As a result, a magnetic repulsive interaction occurs between the two, and the hydrogen gas (H2(g)) easily desorbs from the surface of the ferromagnetic Co0.92-Fe0.08 alloy nanocrystals.

[0111] That is, in the case of WC-(Co0.92-Fe0.08) carbide, protons (H + ) to the surface of the ferromagnetic Co0.92-Fe0.08 alloy nanocrystals by magnetic dipole action, followed by the release of protons (H + The pathway of the hydrogen evolution reaction (HER) is consistent from the accumulation and reduction of hydrogen molecules (H) to the desorption of the generated hydrogen molecules (H) due to diamagnetism. Therefore, by hydrolyzing ammonia borane (NH3BH3) using the WC-(Co0.92-Fe0.08) carbide of this example as a catalyst, the entropy production rate (dSirr / dt) and the time derivative (dSirr / dt) of the entropy production rate (dSirr / dt) in the hydrogen evolution reaction (HER) described above are 2 Sirr / dt2 ) changes smoothly over time. Therefore, by using the WC-(Co0.92-Fe0.08) carbide of this example as a catalyst for the hydrolysis of ammonia borane (NH3BH3), it is possible to generate hydrogen (H2) with a stable release rate.

[0112] Here, for comparison with the tungsten carbide according to the present invention, the mechanism when ammonia borane (NH3BH3) is hydrolyzed using platinum (Pt) as a catalyst will be explained with reference to FIG.

[0113] When platinum (Pt) is used as a catalyst in the hydrolysis of ammonia borane (NH3BH3) to produce hydrogen (H2), a sequential exchange of ammonia borane (NH3BH3) adsorption sites and hydrogen production sites occurs.

[0114] Incidentally, platinum (Pt) nanoparticles are one of the elements that have a large heat of adsorption of hydrogen gas (H2(g)). Therefore, hydrogen gas (H2(g)) is energetically stable when adsorbed on the surface of platinum (Pt) nanoparticles, as shown in Figure 8(a), and it is difficult for hydrogen gas (H2(g)) to immediately desorb from the surface of platinum (Pt) nanoparticles.

[0115] From this, hydrogen (H2(g)) molecules generated from ammonia borane (NH3BH3) gather on the surface of platinum (Pt) nanoparticles, as shown in Figure 8(b).Then, as shown in Figure 8(c), it is thought that the gathered hydrogen molecules (H2) gain enough buoyancy to be able to desorb from the surface of the platinum (Pt) nanoparticles, and then intermittently desorb as bubbles of hydrogen gas (H2(g)).

[0116] Thus, when platinum (Pt) is used as a catalyst, the entropy production rate (dSirr / dt) and the time derivative of the entropy production rate (dSirr / dt) in the hydrogen evolution reaction (HER) are 2 Sirr / dt 2) over time, vibrations occur as shown in FIGS. 5 and 6, making it difficult to generate hydrogen stably and smoothly over time, as in the case of using the tungsten carbide of this example. [Industrial Applicability]

[0117] The tungsten carbide containing a Co-WC solid solution used as a catalyst for producing hydrogen according to the present invention is hydrophilic, and therefore useful as a catalyst when ammonia borane (NH3BH3) is mixed and dissolved in pure water to be hydrolyzed.

[0118] Furthermore, the tungsten carbide constituting the catalyst for producing hydrogen according to the present invention is useful as a cathode electrode material for producing hydrogen by water electrolysis.

Claims

1. Ammonia borane (NH ３ BH ３ ) to hydrogen (H ２ Catalyst for producing hydrogen used to produce hydrogen A catalyst for hydrogen production, characterized by comprising ferromagnetic tungsten carbide in which ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals are solid-dissolved in the lattice of tungsten carbide (WC), and to which an internal magnetic field is imparted.

2. 2. The catalyst for producing hydrogen according to claim 1, wherein the tungsten carbide contains ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals composed of 99.5 to 91.5 mol % of cobalt (Co) and 0.5 to 8.5 mol % of iron (Fe), thereby providing an internal magnetic field.

3. Ammonia borane (NH ３ BH ３ 1. A method for producing a catalyst for producing hydrogen comprising tungsten carbide, which is used to produce hydrogen from a tungsten carbide, comprising the steps of: A mixed aqueous solution is prepared by mixing a tungsten component with a ferromagnetic cobalt component and an iron component, Next, the mixed aqueous solution is evaporated to dryness or spray-dried to produce a solid containing a cobalt component and an iron component; The solid is thermally decomposed to produce an oxide powder, or further subjected to hydrogen thermal reduction to produce a cobalt-iron (Co—Fe) alloy solid solution tungsten alloy powder; Thereafter, the cobalt-iron (Co-Fe) alloy solid solution tungsten alloy powder was carbonized to produce ferromagnetic tungsten carbide containing ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals and having an internal magnetic field applied thereto. A method for producing a catalyst for producing hydrogen, comprising:

4. In the step of carbonizing the cobalt-iron (Co-Fe) alloy solid solution tungsten alloy powder, a tungsten composite carbide (W ６ (Co-Fe) ６ C, (Co-Fe) ２ W ４ 4. The method for producing a catalyst for producing hydrogen according to claim 3, wherein C) is produced.

5. 5. The method for producing a catalyst for hydrogen production according to claim 3, wherein the mixed aqueous solution is a mixture of a cobalt-iron (Co-Fe) alloy component, in which cobalt (Co) is mixed at a ratio of 99.5 to 91.5 mol % and iron (Fe) is mixed at a ratio of 0.5 to 8.5 mol %, and a tungsten component at a molar ratio of 20:

80.

6. 3. A method for producing hydrogen by the catalyst according to claim 1 or 2, comprising the step of: ３ BH ３ ) is mixed with the aqueous solution, and the aqueous solution is then hydrolyzed to obtain the ammonia borane (NH ３ BH ３ ) to hydrogen gas (H ２ (g) A method for producing hydrogen.

7. The aqueous solution is hydrolyzed to produce ammonia borane (NH ３ BH ３ When hydrogen gas is generated from diamagnetic hydrogen gas (H ２ (g)) and the ferromagnetic cobalt-iron (Co-Fe) alloy nanocrystals, the hydrogen gas (H ２ 7. The method for producing hydrogen according to claim 6, wherein (g)) is desorbed from the surface of the cobalt-iron (Co-Fe) alloy nanocrystals.

8. A catalyst for hydrogen production produced by the production method according to any one of claims 3 to 5 and ammonia borane (NH ３ BH ３ ) is mixed with the aqueous solution, and the aqueous solution is then hydrolyzed to obtain the ammonia borane (NH ３ BH ３ ) to hydrogen gas (H ２ (g) A method for producing hydrogen.

9. The aqueous solution is hydrolyzed to produce ammonia borane (NH ３ BH ３ ) to hydrogen gas (H ２ When generating the hydrogen gas (H (g)), the repulsive interaction between the diamagnetic hydrogen gas and the ferromagnetic cobalt-iron (Co—Fe) alloy nanocrystals causes the hydrogen gas (H ２ 9. The method for producing hydrogen according to claim 8, wherein (g)) is desorbed from the surface of the cobalt-iron (Co-Fe) alloy nanocrystals.

10. 3. A method for producing hydrogen by the catalyst according to claim 1 or 2, comprising the step of: ３ BH ３ ) to prepare an aqueous solution, Next, the aqueous solution is hydrolyzed to form the ammonia borane (NH ３ BH ３ ) is adsorbed and cleaved to form protons (H + ) is released, The proton (H + The protons (H ) are transported to the surface of the ferromagnetic cobalt-iron (Co—Fe) alloy nanocrystals in the catalyst for hydrogen production by the magnetic dipole action between the protons (H ) and the electron spins from the cobalt-iron (Co—Fe) alloy in the catalyst for hydrogen production. + ) and reduce it to diamagnetic hydrogen molecules (H ２ ) and The ferromagnetic cobalt-iron (Co—Fe) alloy nanocrystals and the diamagnetic hydrogen molecules (H ２ ) magnetic repulsive interaction, the time derivative (d ２ Sirr / dt ２ ) from the surface of the cobalt-iron (Co—Fe) alloy nanocrystals. ２ ) to generate hydrogen gas.

11. A catalyst for hydrogen production produced by the production method according to any one of claims 3 to 5 and ammonia borane (NH ３ BH ３ ) to prepare an aqueous solution, Next, the aqueous solution is hydrolyzed to deposit the ammonia borane (NH ３ BH ３ ) is adsorbed and cleaved to form protons (H + ) is released, The proton (H + ) and the electron spin from the cobalt-iron (Co—Fe) alloy nanocrystals in the catalyst for hydrogen production, the protons (H + ) and reduce it to diamagnetic hydrogen molecules (H ２ ) and The ferromagnetic cobalt-iron (Co—Fe) alloy nanocrystals and the diamagnetic hydrogen molecules (H ２ ) magnetic repulsive interaction, the time derivative (d ２ Sirr / dt ２ ) from the surface of the cobalt-iron (Co—Fe) alloy nanocrystals. ２ ) to generate hydrogen gas.

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