Boron-containing hydrogen compositions, hydrogen production systems, and fuel cell systems

Abstract

The present invention provides a boron hydride-containing composition, a hydrogen production system, and a fuel cell system, which use a boron hydride-containing sheet to achieve further improvement in hydrogen supply source performance. The boron hydride-containing composition according to the present invention contains a boron hydride-containing sheet and an electron donor, the boron hydride-containing sheet having a two-dimensional network including (BH) n (n ≥ 4, and n is an integer). At least a part of the electron donor is carried on the boron hydride-containing sheet, and by external stimulation, the electron of the electron donor is supplied to the boron hydride-containing sheet, and hydrogen is produced from the boron hydride-containing sheet into which the electron is injected.

Description

TECHNICAL FIELD

[0001] The present application relates to a boron hydride-containing composition and a hydrogen production system. Further, a fuel cell system using the hydrogen production system is disclosed. BACKGROUND

[0002] Hydrogen is a substance that is discharged by combustion or reaction, and is water, and thus, it is attracting attention as a clean energy. As a hydrogen supply source, a high-pressure gas cylinder has been used in the past, but since hydrogen is an explosive gas, development of a hydrogen supply system with high safety has been actively conducted.

[0003] As a hydrogen supply method for fuel cells, a method using a hydrogen storage alloy has been disclosed (Patent Literature 1). In addition, the present inventors have recently proposed a boron hydride-containing sheet that can release hydrogen by heat treatment at a relatively low temperature of 200°C or lower (Non-Patent Literature 1, Patent Literature 2). Furthermore, a method in which a boron hydride-containing sheet releases hydrogen simply by ultraviolet irradiation under mild conditions at room temperature has also been reported (Patent Literature 3).

[0004] Prior Art Documents

[0005] Patent Literature

[0006] Patent Literature 1: Japanese Patent No. 2005-063703

[0007] Patent Literature 2: International Publication No. 2018 / 074518

[0008] Patent Literature 3: Japanese Patent No. 2019-218251

[0009] Non-Patent Literature

[0010] Non-Patent Literature 1: Kondo T., Miyauchi M. et al., Photoinduced hydrogen release from hydrogen boride sheets, Nature Communications, 10, 4880 (2019). SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] Since the boron hydride-containing sheet has a hydrogen storage capacity of about 8.5 wt% per unit mass, which is high, and has excellent lightness, it is desirable to further improve the performance of the boron hydride-containing sheet for practical use as a hydrogen supply source.

[0013] The present application has been made in view of the above-described background, and aims to provide a boron hydride-containing composition, a hydrogen production system, and a fuel cell system which use a boron hydride-containing sheet to achieve further improvement in hydrogen supply source performance, energy saving in hydrogen production.

[0014] Means for solving the problem

[0015] The present inventors have conducted intensive studies and found that the problem of the present application can be solved in the following aspects to complete the present application.

[0016] [1] A boron hydride-containing composition comprising a boron hydride-containing sheet and an electron donor, the boron hydride-containing sheet having a two-dimensional network including (BH) n (n ≥ 4, and n is an integer);

[0017] At least a part of the electron donor is carried on the surface of the boron hydride-containing sheet;

[0018] Through external stimulation, electrons of the electron donor are supplied to the boron hydride-containing sheet, and hydrogen is produced from the boron hydride-containing sheet into which the electrons are injected.

[0019] [2] The boron hydride-containing composition according to [1], wherein a LUMO (lowest unoccupied molecular orbital) or a conduction band level of the electron donor is lower than a conduction band level of the boron hydride-containing sheet.

[0020] [3] The boron hydride-containing composition according to [1] or [2], wherein the electron donor is excited by visible light, and hydrogen is produced from the boron hydride-containing sheet by supplying the excited electron to the boron hydride-containing sheet.

[0021] [4] The boron hydride-containing composition according to any one of [1] to [3], wherein the electron donor is an organic compound.

[0022] [5] The boron hydride-containing composition according to any one of [1] to [4], wherein the electron donor has at least any one of a carboxyl group, a phosphono group, and a sulfonic acid group.

[0023] [6] The boron hydride-containing composition according to any one of [1] to [5], wherein a solvent is contained.

[0024] [7] The boron hydride-containing composition according to any one of [1] to [6], further comprising a hole-trap agent.

[0025] [8] The boron hydride-containing composition according to [7], characterized in that a redox potential of the hole-trap agent is lower than a HOMO (highest occupied molecular orbital) or a valence band level of the electron donor.

[0026] [9] The boron hydride-containing composition according to any one of [1] to [8], further comprising a proton donor.

[0027]

[10] The boron hydride-containing composition according to [9], wherein the proton donor is an acid.

[0028]

[11] A hydrogen production system comprising the boron hydride-containing composition according to any one of [1] to

[10] , the hydrogen production system comprising:

[0029] a boron hydride-containing composition;

[0030] a control unit that controls on-off of external stimulation to the boron hydride-containing composition; and

[0031] a hydrogen production unit that takes out hydrogen to the outside.

[0032]

[12] A fuel cell system comprising the hydrogen production system according to

[11] and a fuel cell, the hydrogen production system supplying hydrogen to the fuel cell.

[0033] Effects of the Invention

[0034] According to the present application, an excellent effect of providing a boron hydride-containing composition, a hydrogen production system, and a fuel cell system that use a boron hydride-containing sheet to further improve the performance of a hydrogen supply source and achieve energy-saving hydrogen production can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic view showing a partial structure of a two-dimensional network including (BH) n (n≥4) of the present embodiment.

[0036] Figure 2 is a schematic view showing a partial structure of a two-dimensional network including (BH) n (n≥4) of the present embodiment.

[0037] Figure 3 is a schematic view showing a partial structure of a two-dimensional network including (BH) n (n≥4) of the present embodiment.

[0038] Figure 4 is a schematic view showing an example of a hydrogen release mechanism of the present composition using a pigment.

[0039] Figure 5 is a schematic view showing an example of a hydrogen release mechanism of the present composition using a semiconductor.

[0040] Figure 6 is a schematic view showing an example of a hydrogen release mechanism of the present composition using a metal.

[0041] Figure 7 is a schematic diagram showing an example of hydrogen release mechanism from the present composition due to heat.

[0042] Figure 8 is a schematic diagram showing an example of hydrogen release mechanism from the present composition using a dye and a hole-trap agent.

[0043] Figure 9 is a schematic diagram showing an example of hydrogen release mechanism from the present composition using a dye, a hole-trap agent, and a proton donor.

[0044] Figure 10 is a schematic diagram showing another example of hydrogen release mechanism from the present composition using a dye, a hole-trap agent, and a proton donor.

[0045] Figure 11 is a schematic diagram showing an example of main parts of the hydrogen generation system of the first embodiment.

[0046] Figure 12 is a schematic diagram showing an example of main parts of the hydrogen generation system of the second embodiment.

[0047] Figure 13 is a schematic diagram showing an example of main parts of the hydrogen generation system of the third embodiment.

[0048] Figure 14 is a schematic diagram showing an example of main parts of the hydrogen generation system of the fourth embodiment.

[0049] Figure 15 is a schematic diagram showing an example of the thin film used in the hydrogen generation system of the fifth embodiment.

[0050] Figure 16 is a transmission electron microscope photograph of the product of Example 1.

[0051] Figure 17 is a graph showing the measurement results of EELS of the product of Example 1.

[0052] Figure 18 is a graph showing the measurement results of FT-IR of the product of Example 1.

[0053] Figure 19 is a UV-Vis spectrum of the composition of Example 1 and Comparative Example 1.

[0054] Figure 20 is a UV-Vis spectrum of the composition of Example Four.

[0055] Figure 21 is a TEM image of the composition of Example Five.

[0056] Figure 22 This is a TEM image of the composition of Example 6.

[0057] Figure 23 This is a TEM image of the composition of Example 7.

[0058] Figure 24 This is a TEM image of the composition of Example 8.

[0059] Figure 25 This is a schematic diagram illustrating a device for evaluating hydrogen release.

[0060] Figure 26 It is the spectrum of the irradiated light used in the device for evaluating hydrogen release.

[0061] Figure 27 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the compositions in Example 1, etc.

[0062] Figure 28 These are the effect spectrum and UV-Vis absorption spectrum of the composition in Example 1.

[0063] Figure 29 The graph shows the results of visible light irradiation intensity and hydrogen release of the composition of Example 1.

[0064] Figure 30 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the compositions in Example 2, etc.

[0065] Figure 31 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the compositions in Examples 1 and 3.

[0066] Figure 32 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the composition of Example 1 (the effect of adding pigment and proton donor).

[0067] Figure 33 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the composition of Example 4.

[0068] Figure 34 This is a graph showing the amount of hydrogen released relative to the visible light irradiation time of the compositions in Examples 9 and 10.

[0069] Figure 35 These are plots of wide band gaps of the powdered products of Comparative Examples 4 and 5 and Reference Example 1, drawn according to the Tauc-plot. Detailed Implementation

[0070] Hereinafter, an example of applying the embodiment of the present application will be described. Note that other embodiments are also included in the scope of the present application as long as the purpose of the present application is achieved. In addition, the size and ratio of each component in the following drawings are for facilitating the description and are not limited thereto.

[0071] The boron hydride composition of the present embodiment (hereinafter, also referred to as the present composition) contains a boron hydride sheet (hereinafter, also referred to as "boron hydride sheet") having a two-dimensional network including (BH) n (n≥4, and n is an integer) as a sheet-shaped substance, and an electron donor. At least a part of the electron donor is carried on the surface of the boron hydride sheet. Also, by an external stimulus, the electron of the electron donor is supplied to the boron hydride sheet, and hydrogen is generated from the boron hydride sheet into which the electron is injected.

[0072] In the present specification, the "carrying" includes a state of being chemically adsorbed on the surface of the boron hydride sheet, or a state of being physically attached to the boron hydride sheet. In addition, the "external stimulus" means a certain stimulus applied to the boron hydride composition, and the stimulus is only required to be able to supply the electron of the electron donor to the boron hydride sheet to generate hydrogen gas. As a specific example, energy ray irradiation of heat energy, infrared rays, visible light, ultraviolet rays, or electron rays can be given.

[0073] According to the present composition, since the electron donor that induces the boron hydride sheet to generate hydrogen is contained, the hydrogen generation efficiency can be improved. In addition, there is an excellent advantage described later that by the selection of the type of the electron donor, the external stimulus can be selected according to the demand and the use. For example, hydrogen can be released not only by ultraviolet rays but also by visible light contained in a large amount in sunlight or white lighting, and thus, as a hydrogen release material that utilizes a renewable energy and ambient lighting, a wide use development can be expected. Note that the present embodiment can generate hydrogen at normal temperature and pressure, but does not exclude the use of a heating process or a pressurization process. Hereinafter, each component will be described in detail.

[0074] [Boron hydride sheet]

[0075] In the present specification, the "boron hydride sheet" means a sheet-shaped substance having a two-dimensional network including (BH) n (n≥4, and n is an integer). In the two-dimensional network including (BH) n (n≥4), it is formed at a ratio of 1:1 of boron atoms (B) and hydrogen atoms (H) (see Non-Patent Literature 1).

[0076] The boron hydride sheet only needs to have a two-dimensional network including (BH) n (n≥4), and includes a two-dimensional network including (BH) na compound having a two-dimensional network of boron-hydrogen sheets (BH) n (n≥4) as a main skeleton (for example, a compound including (BH) n a compound in which a dopant is introduced in a part of the two-dimensional network of (BH) n (n≥4), a compound in which a terminal is closed by an oxide, a carbide, a nitride, a hydroxide, a sulfide, or the like, a compound in which a terminal is bonded to an organic group). Here, the main skeleton refers to a substance in which the proportion of the boron-hydrogen sheet in the compound is 80% or more.

[0077] As the dopant, for example, at least one element selected from the group consisting of carbon, nitrogen, oxygen, fluorine, phosphorus, sulfur, chlorine, arsenic, selenium, bromine, antimony, tellurium, iodine, or a metal element such as titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, cadmium, indium, tin, yttrium, niobium, molybdenum, tungsten, tantalum, lead, or a noble metal element such as ruthenium, rhodium, palladium, silver, gold, iridium, platinum, or the like can be exemplified.

[0078] Figures 1-3 a compound including (BH) n a schematic view of a partial structure of the two-dimensional network of (BH) n (n≥4). As shown in Figure 1 the boron atoms of the two-dimensional network are arranged in a honeycomb-shaped hexagonal lattice (a mesh shape in which hexagons formed of the boron atoms are connected), and the two-dimensional network has a site at which two adjacent boron atoms among the boron atoms are bonded to the same hydrogen atom. The boron atoms are arranged in a honeycomb-shaped sheet-shaped hexagonal lattice structure, as shown in Figure 2 Figure 3 one hydrogen atom is bridgingly bonded to two adjacent boron atoms among the boron atoms of the hexagonal lattice structure, above and below the sheet, respectively. In addition, two hydrogen atoms are arranged so as to face each other above and below the structure, via the sheet-shaped hexagonal lattice structure. Note that the arrangement of the hydrogen in the borohydride can not have long-range order. In addition, a structure in which the bond between the atoms is tilted in the Z direction of Figure 2 or Figure 3 , or the sheet itself is bent, can be formed. In addition, not all of the hydrogen atoms can be bridgingly bonded.

[0079] The borohydride sheet is a thin film-like substance, and can be a single layer or can be composed of multiple layers. In the borohydride sheet of the present embodiment, the total number of boron atoms (B) and hydrogen atoms (H) forming the mesh-shaped planar structure described above is 1000 or more.

[0080] The bonding distance d1 (refer to Figure 1 ) between two adjacent boron atoms (B) is, for example, 0.155 nm to 0.190 nm. In addition, when viewed in the Z direction, the bonding distance d2 (refer to Figure 2 ​For example, 0.155 nm to 0.190 nm. In addition, the bonding distance d3 between the adjacent boron atoms (B) and hydrogen atoms (H) (refer to FIG. 2) is, for example, 0.12 nm to 0.15 nm. Figure 2 For example, 0.155 nm to 0.190 nm. In addition, the bonding distance d3 between the adjacent boron atoms (B) and hydrogen atoms (H) (refer to FIG. 2) is, for example, 0.12 nm to 0.15 nm.

[0081] The thickness of the boron-containing hydrogen sheet is, for example, 0.2 nm to 10 nm. The length of at least one direction of the boron-containing hydrogen sheet (for example, the length of the X direction or the Y direction in FIG. 1) is preferably 100 nm or more. By setting the length of at least one direction to 100 nm or more, the boron-containing hydrogen sheet can be more effectively utilized as an electronic material, a carrier material for a catalyst, a catalyst material, a superconducting material, or the like. The size (area) of the boron-containing hydrogen sheet is not particularly limited and can be formed to an arbitrary size. Figure 1

[0082] The boron-containing hydrogen sheet of the present embodiment is a substance having a crystal structure. In addition, according to the boron-containing hydrogen sheet of the present embodiment, the bonding force between the boron atoms (B) forming the hexagonal ring and between the boron atoms (B) and the hydrogen atoms (H) is strong. Therefore, the boron-containing hydrogen sheet of the present embodiment, even when a crystal (agglomerate) formed by stacking a plurality of layers is formed at the time of production, can be easily cleaved along the crystal plane like graphite and separated (recovered) as a single-layer two-dimensional sheet.

[0083] According to the boron-containing hydrogen sheet, the lightness is very excellent compared to a hydrogen storage alloy. In addition, since it can be used at normal pressure, the safety is excellent. Note that the use in a state other than normal pressure is not excluded.

[0084] The method for producing the boron-containing hydrogen sheet is not particularly limited. For example, it can be produced by the following method. Specifically, first, a metal diboride of an MB2 type structure and an ion exchange resin to which an ion capable of ion exchange with the metal ion constituting the metal diboride is coordinated are mixed in a polar organic solvent. The M is at least one selected from the group consisting of Al, Mg, Ta, Zr, Re, Cr, Ti, and V. The mixing process can be performed under an inert atmosphere composed of an inert gas such as nitrogen (N2) or argon (Ar).

[0085] As the metal diboride of an MB2 type structure, a metal diboride having a hexagonal ring structure can be used. For example, aluminum diboride (AlB2), magnesium diboride (MgB2), tantalum diboride (TaB2), zirconium diboride (ZrB2), rhenium diboride (ReB2), chromium diboride (CrB2), titanium diboride (TiB2), and vanadium diboride (VB2) can be used. It is preferable to use magnesium diboride because it can be easily ion exchanged with the ion exchange resin in a polar organic solvent.

[0086] ​The ion exchange resin having ions capable of ion exchange with the metal ions constituting the metal diboride is not particularly limited. As such an ion exchange resin, for example, a polymer of styrene having a functional group (hereinafter, referred to as "functional group a") having ions capable of ion exchange with the metal ions constituting the metal diboride, a polymer of divinylbenzene having the functional group a, a copolymer of styrene having the functional group a and divinylbenzene having the functional group a can be exemplified. As the functional group a, for example, a sulfo group and a carboxyl group can be exemplified. Among these functional groups, the sulfo group is preferred because the sulfo group can easily ion exchange with the metal ions constituting the metal diboride in a polar organic solvent.

[0087] An acid can also be further added in the mixing step. As the acid, for example, acetic acid, carbonic acid, tartaric acid, malic acid, maleic acid, propionic acid, formic acid, succinic acid, citric acid, oxalic acid, lactic acid, hydrochloric acid, sulfuric acid and phosphoric acid can be exemplified. By adding the acid, the time for ion exchange of the metal ions constituting the metal diboride with the ion exchange resin in a polar solvent can be easily and greatly shortened.

[0088] As the polar organic solvent, there is no particular limitation, and for example, acetonitrile, N,N-dimethylformamide and methanol can be exemplified.

[0089] In the mixing step, the acid is removed as necessary in the case where the acid is used. The method for removing the acid is not particularly limited, and heating, reduced pressure drying and precipitation recovery method, etc. can be exemplified.

[0090] Then, the mixed solution is filtered. For example, a method such as natural filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, etc. can be used. The precipitate is separated by filtration, and the recovered solution containing the product is dried by natural drying, reduced pressure drying or heating, etc. to finally obtain the boron hydride containing sheet having a two-dimensional network as the product.

[0091] [Electron donor]

[0092] In the present specification, the so-called "electron donor" as described above means a substance capable of supplying an electron to the boron hydride sheet by an external stimulus, and generating hydrogen from the boron hydride sheet into which the electron is injected. The LUMO (lowest unoccupied molecular orbital) or conduction band level of the electron donor is preferably lower than the conduction band level of the boron hydride sheet. As specific examples of the electron donor, a light absorber and a heat absorber can be exemplified. As specific examples thereof, an organic compound can be exemplified. In addition, a substance exhibiting metallic properties and a substance exhibiting semiconductor properties can be exemplified. As the substance exhibiting metallic properties, a metal, a metal oxide, a metal nitride, a metal carbide, a metal oxynitride, and a metal oxycarbide can be exemplified. In addition, as the substance having semiconductor properties, a semiconductor, a metal nitride, a metal sulfide, and a metal oxide can be exemplified. These exemplified substances can be used alone or in any combination. In the case where visible light is used as the external stimulus, as a preferable example of the organic compound, a pigment can be cited. Here, the so-called pigment means a compound selectively absorbing visible light in a specific wavelength region, thereby causing color vision.

[0093] In the electron donor, a functional group can also be introduced to improve the carrying rate of the boron hydride sheet. As such a functional group, a carboxyl group, a phosphono group, and a sulfonic acid group can be exemplified. Among them, the carboxyl group is preferable.

[0094] Using Figure 4 An example of the mechanism of the hydrogen generation mechanism of the present composition when a pigment is used as the electron donor will be described. However, the present application is not limited to this mechanism. In the case where the external stimulus is visible light, the mechanism of the hydrogen generation mechanism of the present composition will be described. Figure 4 In the example, an example using visible light as the external stimulus will be described. By the pigment, visible light is absorbed, and by the absorption of the light, the electron of the pigment is excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital). Thereby, a hole (h + +) is generated in the pigment. Further, it is considered that by a process of injecting the excited electron into the hydrogen ion in the conduction band level of the antibonding orbital of hydrogen constituting the boron hydride sheet, the 2H + + 2e - → H2↑ reaction occurs, and hydrogen is taken out.

[0095] Using Figure 5An example of a mechanism of a hydrogen production mechanism when a semiconductor is used as an electron donor will be described. However, the present application is not limited to this mechanism. In this example, an example in which light irradiation is used as an external stimulus will be described. With a semiconductor, light is absorbed, and by this absorption of light, electrons are excited from a valence band of the semiconductor to a conduction band. Furthermore, it is considered that by injecting this excited electron into a hydrogen ion at a conduction band level which is a π* orbital of hydrogen of the boron-containing hydrogen sheet, hydrogen is released. As an external stimulus, heat can be used instead of or in addition to light irradiation. In addition, the irradiation wavelength can be appropriately selected according to the semiconductor used. A plurality of semiconductors having different excitation wavelengths can be used in combination, and a plurality of irradiation wavelengths or irradiation bands can be used.

[0096] Using Figure 6 An example of a mechanism of a hydrogen production mechanism when a metal is used as an electron donor will be described. However, the present application is not limited to this mechanism. In this example, an example in which light irradiation is used as an external stimulus will be described. With a metal, light is absorbed, and by this absorption of light, electrons are excited from a HOMO of the metal to an unoccupied molecular orbital of the metal such as an s or d orbital. Furthermore, it is considered that by injecting this excited electron into a hydrogen ion at a conduction band level which is a π* orbital of hydrogen of the boron-containing hydrogen sheet, hydrogen is released. As an external stimulus, heat can be used instead of or in addition to light irradiation. In addition, the irradiation wavelength can be appropriately selected according to the semiconductor used. A plurality of semiconductors having different excitation wavelengths can be used in combination, and a plurality of irradiation wavelengths or irradiation bands can be used.

[0097] The dye is not particularly limited as long as it has a photosensitive effect. As preferred examples, there can be mentioned, for example, cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid)ruthenium(II) (hereinafter, also referred to as "N3"), bis-TBA salt of cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid)ruthenium(II) (hereinafter, also referred to as "N719"), tetra-TBA salt of cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid)ruthenium(II) (hereinafter, also referred to as "N712"), tri-tetrabutylammonium salt of tris(thiocyanato)-(4,4',4"-tricarboxy-2,2':6',2"-terpyridine)ruthenium (hereinafter, also referred to as "N749"), mono-tetrabutylammonium salt of cis-di(thiocyanato)-(2,2'-bipyridyl-4,4'-dicarboxylic acid)(4,4'-bis(5'-hexylthio-5-(2,2'-bithiophene))bipyridine)ruthenium(II) (hereinafter, also referred to as "black dye"), C106, and the like, ruthenium-based sensitizing dyes; iridium-based sensitizing dyes such as tris(2-phenylpyridine)iridium(III). In addition, various organic sensitizing dyes such as coumarin-based dyes, polyene-based dyes, cyanine-based dyes, hemicyanine-based dyes, thiophene-based dyes, indolene-based dyes, xanthene-based dyes, carbazole-based dyes, perylene-based dyes, porphyrin-based dyes, phthalocyanine-based dyes, squarylium-based dyes, catechol-based dyes, azo-based dyes, oxazine-based dyes, and squaraine-based dyes are also preferred. In addition, donor-acceptor complex sensitizing dyes and the like in which these sensitizing dyes are combined can also be used. The dye can be used singly or in combination of two or more. The dye preferably contains at least one of N3, N719, N712, and C106.

[0098] The substance having metallic properties is not particularly limited as long as it has a metallic electronic structure, and refers to a substance in which the electrons of the metal are excited by light or heat, and the excited electrons can be supplied to the boron hydride sheet. As preferred examples, there can be mentioned alloys containing at least one metal selected from the group consisting of gold, platinum, silver, copper, palladium, rhodium, ruthenium, rhenium, iridium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, zirconium, niobium, molybdenum, indium, tin, germanium, tantalum, tungsten, osmium, and lead. In addition, compounds such as metal carbides and metal nitrides can also be used. As the metal carbides, there can be mentioned TiC, ZrC, HfC, TaC, WC, and the like. Since these metal carbides exhibit metallic properties, they can be used as electron donors. In addition, as the metal nitrides, there can be mentioned TiN, ZrN, HfN, TaN, WN, and the like. These metal nitrides exhibit metallic properties, and all function as electron donors. In addition, metal oxynitrides, metal oxycarbides, and compounds containing oxygen ions and having metallic properties can also be used.

[0099] The substance having semiconductor properties means a substance that, by irradiation of light or heat excitation of the substance, the excited electron can supply to the boron hydride sheet. The kind is not particularly limited. As a preferable example, oxides such as tungsten oxide, bismuth oxide, iron oxide, nickel oxide, cobalt oxide, bismuth vanadate, calcium ferrite, nitrides such as tantalum nitride, sulfides such as cadmium sulfide, zinc sulfide, indium sulfide, tin sulfide, lead sulfide, selenium sulfide, tellurium sulfide, phosphorus sulfide, and the like can be exemplified. From the viewpoint of electron injection efficiency and control of the response wavelength, semiconductor quantum dots having a diameter of about 5 to 20 nm are preferable.

[0100] When light is absorbed in the metal (including a substance exhibiting metallic properties) or the semiconductor (including a substance having semiconductor properties), recombination of the excited carriers generates heat, as shown in Figure 7 The heat can become an external stimulus to induce generation of hydrogen from the boron hydride sheet. In particular, in the metal, occurrence of plasmonic absorption generates a near field, thereby causing a photothermal effect, and by the heat, the boron hydride sheet can be promoted to efficiently generate hydrogen. In the case of hydrogen generation by light heating, it is not necessarily required to inject electrons from the electron donor to the boron hydride sheet, but the use of the electron donor can improve the hydrogen generation efficiency.

[0101] [Solvent]

[0102] The present composition can be used in a powder without using a solvent, but can be dissolved or dispersed in a solvent. The solvent can be exemplified by water or an organic solvent. The organic solvent is not particularly limited, and for example, amide-based solvents, alcohol-based solvents, ester-based solvents, ketone-based solvents, nitrile-based solvents, aromatic hydrocarbon-based solvents, halogenated hydrocarbons, ethers, amides, carbonates, hydrocarbons, nitromethane, and the like can be exemplified. As the nitrile-based solvent, acetonitrile, isobutyronitrile, propionitrile can be exemplified. As the alcohol-based solvent, methanol, ethanol, propanol, and the like can be exemplified. The solvent can be used alone or in combination of two or more.

[0103] [Hole Trapper]

[0104] The present composition can further contain a hole trapper. The hole trapper can trap a hole generated in the electron donor by an external stimulus, and itself becomes an oxidized state, and thus can prevent degradation of the electron donor due to oxidation of itself. The oxidation-reduction potential of the hole trapper is preferably lower than the HOMO (highest occupied molecular orbital) or the valence band energy level of the electron donor.

[0105] Figure 8is a schematic diagram showing an example of hydrogen production mechanism when a hole trapping agent is used in the present composition. However, the present application is not limited to this mechanism. In this example, an example using visible light as an external stimulus is described. By the pigment, visible light is absorbed, and by the absorption of this light, the electron of the pigment is excited from HOMO (highest occupied molecular orbital) to LUMO (lowest unoccupied molecular orbital). At this time, although a hole (h + ) is generated in the pigment, since the hole trapping agent supplies an electron to the pigment, the self-oxidation of the pigment can be inhibited. By this reaction, the hole trapping agent is oxidized, and the pigment continuously functions as an electron donor. By appropriately replenishing the hole trapping agent, the hydrogen production ability can be improved while the amount of the pigment added is inhibited.

[0106] The hole trapping agent is not particularly limited as long as it has the above function. As a preferred example, triethanolamine (TEOA), ascorbic acid; 1-benzyl-1,4-dihydronicotinamide; benzimidazole derivatives; alcohols such as methanol, ethanol, butanol, and propanol; aldehydes such as formaldehyde and acetaldehyde; carboxylic acids such as formic acid, acetic acid, and propionic acid; redox reagents such as bromide ions, iodide ions, iodate ions, iron ions (Fe 2+ ), ferrocene, and the like; photocatalytically active ethylenediaminetetraacetic acid (EDTA); and sodium formate, polysulfide ions can be given.

[0107] The hole trapping agent can be reused by reducing the oxidized state in which the hole is trapped. As a method of reducing the hole trapping agent, a method in which a chemical reducing agent such as sodium borohydride, hydrazine, or an aldehyde is mixed into the present composition can be given. Alternatively, or in addition to the above method, the hole trapping agent can be electrochemically reduced by bringing a cathode electrode (not shown) into contact with the present composition.

[0108] [Proton Donor]

[0109] The present composition can also contain a proton donor. The proton donor is a compound that can supply protons, and can be dissolved in a liquid or dispersed without being dissolved. As a preferred example of the proton donor, inorganic acids, organic acids such as carboxylic acids, sulfonic acids, and phenols, alcohols, mercaptans, 1,3-dicarbonyl compounds can be given. In addition, solid acids such as zeolites and ion exchange resins are also preferred. As a preferred example of the proton donor, an acid such as formic acid can be given.

[0110] Figure 9 is a schematic diagram showing an example of hydrogen production mechanism when a proton donor is used in the present composition. According to this diagram, an example of the mechanism of the hydrogen production mechanism is described. However, the present application is not limited to this mechanism. As a hydrogen supply source, in addition to the boron hydride sheet, a proton donor is also used. Thereby, the hydrogen source lost by boron hydride can be supplied, and the amount of hydrogen released can be increased.

[0111] [Other additives]

[0112] The present composition can be added with a high molecular compound or a low molecular compound such as a binder resin, a dispersant, and the like, within the scope of the object of the present application. In addition, an antistatic agent, a thermally conductive filler, a flame retardant, and the like, can be added as appropriate.

[0113] [Borohydride-containing composition]

[0114] The present composition can be used as a powder. In addition, a solvent can be added to be used as a solution, a dispersion, a slurry. In addition, the present composition can be a thin film or a shaped body of an arbitrary shape. The thin film or the shaped body can be a porous body. A laminated body containing a borohydride sheet and a layer containing an electron donor supported thereon can be used, the laminated body having a hole-trapping agent layer laminated on one major surface of the thin film and a proton donor layer laminated on the other major surface.

[0115] The method for producing the borohydride-containing composition is not particularly limited. It can be obtained by mixing the raw materials of the composition in any order. In addition to adjusting the composition in advance, the components of the composition can be put in at the time of use to prepare it.

[0116] [Continuous hydrogen production system]

[0117] By containing a renewable hole-trapping agent and a proton donor in the present composition, the degradation of the borohydride sheet and the electron donor due to external stimuli can be prevented, and hydrogen can be continuously produced. That is, even after the hydrogen originating from the borohydride sheet is released, the hydrogen source can be supplied from the proton donor. In addition, the electron-hole pair of the electron donor moves to the borohydride sheet and the hole-trapping agent, respectively, and the degradation of the electron donor itself due to self-oxidation or self-reduction can be suppressed.

[0118] In Figure 10 , an example of a method for electrochemically reducing the hole-trapping agent is described. In the figure, a dye is used, and visible light is used as an external stimulus to release hydrogen, while a cathode and an anode are added to a solvent dispersion system in which the present composition is dispersed, and the redox reagent is regenerated in the dark by an external electric field. In this way, the hole-trapping agent is electrochemically reduced, and the hole-trapping agent can be continuously reused. In addition, by adding a proton donor, the hydrogen released from the borohydride sheet can be supplemented.

[0119] [Hydrogen production system]

[0120] The hydrogen production system of the present embodiment uses the above-described boron-containing hydrogen compound, and has the boron-containing hydrogen compound, a control unit that controls the ON / OFF of external stimulation to the boron-containing hydrogen compound, and a hydrogen production unit that takes out hydrogen to the outside. The hydrogen production system can be applied to all uses in which it is desired to produce hydrogen by external stimulation such as light irradiation. Hereinafter, one example of a specific embodiment of the hydrogen production system will be described. The embodiments can be appropriately combined.

[0121] (First Embodiment)

[0122] In Figure 11 , a schematic explanatory view of the hydrogen production system of the first embodiment is shown. The hydrogen production system 1 has a hydrogen production unit 10 and an external stimulation control unit 20. In the hydrogen production unit 10, a raw material supply tank 11, a solvent supply path 12, a gas recovery path 13, and a discharge path 14 are connected, and has a container that contains a boron-containing hydrogen compound 30 and a stirring unit 15 that performs stirring. In Figure 11 , an example in which a composition other than the solvent in the boron-containing hydrogen compound is supplied from the raw material supply tank 11. The boron-containing hydrogen compound including the solvent can also be supplied from the raw material supply tank. Alternatively, the boron-containing hydrogen sheet, the electron donor, and the hole-trap agent and the proton donor as needed can be supplied respectively or in any combination. For example, a tank that supplies the electron donor carried on the boron-containing hydrogen sheet, a tank that supplies the hole-trap agent, and a tank that supplies the proton donor can be provided respectively. In this way, the optimum materials can be supplied according to the use.

[0123] The external stimulation control unit 20 functions to supply external stimulation to the boron-containing hydrogen sheet 31 that carries the electron donor dispersed in the solvent 32 in the hydrogen production unit 10 at a desired timing. For example, in the case where visible light is used as the external stimulation, the external stimulation control unit 20 has a function of irradiating visible light and a function of controlling the ON / OFF of the visible light irradiation. That is, the external stimulation control unit 20 has a visible light source and an irradiation control function of the light source. Alternatively, the light source can not be built-in, and external light such as sunlight can be used. In this case, the external stimulation control unit 20 has a function of controlling the transmission and shading of the external light.

[0124] The hydrogen produced in the hydrogen production unit 10 is trapped by the gas recovery path 13. According to the hydrogen production system 1 of the first embodiment, the amount of hydrogen can be easily adjusted by controlling the conditions (intensity, time, etc.) of the external stimulation or the conditions (amount, concentration, shape, etc.) of the boron-containing hydrogen compound. Therefore, hydrogen can be supplied by light irradiation without the need to store hydrogen gas in a storage tank in advance. Of course, a structure in which hydrogen is stored in a hydrogen storage tank by the gas recovery path 13 is not excluded. In the case where such a hydrogen storage tank is provided, the advantage that the required amount of hydrogen can be taken out instantaneously is obtained.

[0125] To prevent the decrease in the amount of hydrogen released as the reaction time elapses, the present composition 30 needs to be replaced at an appropriate timing. The discharged present composition 30 is recovered by filtration or centrifugal separation of the boron-containing substance as a byproduct, and the solvent can be directed again to the solvent supply path 12 for reuse.

[0126] The hydrogen production system of the first embodiment can be variously modified. For example, it can be configured so that the container that accommodates the present composition 30 and the stirring section 15 are not provided in the hydrogen production section 10, but a flow path (not shown) is provided, the present composition 30 is caused to flow into the flow path at a desired flow rate, and hydrogen is produced by supplying an external stimulus thereto.

[0127] The hydrogen production system according to the first embodiment does not require a high-pressure tank and can produce hydrogen simply at normal temperature and pressure. Moreover, since the production of hydrogen can be controlled by light irradiation, the on-off control of the production of hydrogen can be performed instantaneously and simply as compared with the heating method. Furthermore, the mass can be greatly reduced as compared with a hydrogen storage alloy.

[0128] (Second Embodiment)

[0129] Next, an example of a hydrogen production system different from the first embodiment will be described. The hydrogen production system of the second embodiment differs from the first embodiment in that a gas is used as a dispersion medium and the composition does not contain a solvent. Note that in the following drawings, the same reference numerals are given to element parts having the same functions as the aforementioned functions. In addition, the description overlapping with the first embodiment is appropriately omitted.

[0130] In Figure 12 , a schematic explanatory view of the hydrogen production system of the second embodiment is shown. The hydrogen production system 2 has a hydrogen production section 10 and an external stimulus control section 20. The hydrogen production section 10 is connected to a raw material supply tank 11, a gas recovery path 13, a discharge path 14, and a gas supply path 16, and the like. In addition, the hydrogen production section 10 has a gas flow generation section 17 for causing the present composition to fly and diffuse in a gas.

[0131] In the hydrogen production section 10, the boron-containing hydride composition 30 is supplied from the raw material supply tank 11 and nitrogen or an inert gas is supplied from the gas supply path 16 at a desired timing. The gas flow generation section 17 functions to cause the boron-containing hydride composition 30 dispersed in the gas as a dispersion medium to fly within the hydrogen production section 10.

[0132] The external stimulus control section 20 functions to supply an external stimulus to the boron-containing hydride composition 30 dispersed in the gas flow at a desired timing. The structure can be the same as that of the first embodiment.

[0133] The hydrogen generated in the hydrogen generation section 10 is captured by the gas recovery path 13. The gas containing a large amount of hydrogen is recovered by the upward displacement. According to the hydrogen generation system of the second embodiment, by controlling the conditions (intensity, time, etc.) of the external stimulus or the conditions (amount, shape, kind of electron donor, carrying amount, etc.) of the composition, the amount of hydrogen generated at normal temperature and pressure can be easily adjusted.

[0134] To prevent the decrease in the amount of hydrogen released, the gas containing the residue is discharged through the discharge path 14 at an appropriate timing. The recovered residue can be separated into gas and residue by a filter and reused respectively.

[0135] According to the hydrogen generation system of the second embodiment, the same effects as the first embodiment can be obtained. In addition, since the gas-using method is employed, further weight reduction can be achieved compared to the first embodiment.

[0136] (Third Embodiment)

[0137] The hydrogen generation system of the third embodiment is different from the above embodiments in that the hydrogen generation section 10 is composed of a thin container and the light source as the external stimulus control section is a thin container built in the hydrogen generation section 10.

[0138] In Figure 13 , a schematic explanatory view of the main part of the hydrogen generation system of the third embodiment is shown. The hydrogen generation section 10 has a plurality of thin containers 18. In the thin container 18, a LED light source 21 as the external stimulus control section is built in. In the hydrogen generation section 10, a supply path (not shown) for supplying a dispersion medium (composition) in which a boron hydride sheet carrying an electron donor is dispersed, a gas recovery path (not shown), a discharge path (not shown) for the dispersion medium, etc. are connected. The dispersion medium can be a liquid or a gas.

[0139] The thin container 18 is configured to supply the dispersion medium in which the boron hydride sheet is dispersed from the supply path at a desired timing. In the hydrogen generation section 10, at a timing at which hydrogen is desired to be generated, light is irradiated from the LED light source 21 to the dispersed boron hydride composition 30.

[0140] The hydrogen generated in the thin container 18 is captured by the gas recovery path. According to the hydrogen generation system of the third embodiment, the same effects as the first embodiment can be obtained. In addition, by using a plurality of thin containers 18, hydrogen can be generated as needed. Note that, depending on the use, only the gas recovery path can be provided without providing the supply path or the discharge path, and used as a disposable or replaceable filter cartridge.

[0141] (Fourth Embodiment)

[0142] The hydrogen production system of the fourth embodiment differs from the above-described embodiments in that the present composition is supported on a support.

[0143] In Figure 14 In FIG. 4, an example of a schematic explanatory view of the main part of the hydrogen production system of the fourth embodiment is shown. In the hydrogen production system 4, the powdered boron hydride-containing composition 30 is supported on the beads 41 that are transparent to irradiation light. By using the support beads 40 on which the boron hydride-containing composition 30 is supported, the area of the present composition that is subjected to external stimulation can be increased, and the efficiency of hydrogen release can be improved.

[0144] In the hydrogen production section 10, a conveyer belt 19 that conveys the support beads 40 at a desired speed is provided, and the support beads 40 supplied to the conveyer belt 19 are subjected to light irradiation at a desired timing using an external stimulation control section 20. Also, the hydrogen generated in the hydrogen production section 10 is captured by the gas recovery path 13. The support beads 40 on the conveyer belt 19 adjust the light irradiation conditions, the convey speed of the conveyer belt 19, and the amount of conveyance of the support beads 40 so that the amount of hydrogen release is not reduced.

[0145] The hydrogen production system according to the fourth embodiment can achieve the same effects as the first embodiment. In addition, the device can be miniaturized. Note that, instead of the beads, an adhesive sheet, a porous body, a film, or the like can be used as the support.

[0146] (Fifth Embodiment)

[0147] The hydrogen production system of the fifth embodiment differs from the above-described embodiments in that the powder of the present composition is dispersed in a binder.

[0148] In Figure 15 In FIG. 5, an example of a schematic explanatory view of a film used in the hydrogen production system of the fifth embodiment is shown. The film 50 is composed of a molded body in which the powder of the boron hydride-containing composition 30 is dispersed in a binder 51. The molded body can also be formed on a support. By dispersing the boron hydride-containing composition 30 in the binder 51, the present composition can be easily shaped into a desired shape. The binder 51 is preferably a foamed resin or a porous body that does not hinder hydrogen production. In addition, the binder is preferably a material that is highly transparent to light in the case where the external stimulation is light, so that the efficiency of hydrogen release is not reduced.

[0149] The hydrogen production system according to the fifth embodiment can achieve the same effects as the first embodiment. In addition, the present composition mounted on the hydrogen production section can be shaped into a desired shape.

[0150] [Fuel Cell System]

[0151] The fuel cell system of this embodiment, compared to known fuel cells, incorporates the aforementioned hydrogen production system as a hydrogen supply source. According to this embodiment, the fuel cell can easily supply hydrogen to the fuel cell at room temperature without the need for a high-pressure tank.

[0152] Example

[0153] (Synthesis Example 1)

[0154] Based on non-patent literature 1, a borohydride-containing sheet was synthesized, which has (BH) n A two-dimensional network with n≥4 was constructed. Specifically, 500 mg of magnesium diboride (Sigma Aldrich) and 30 mL of cation exchange resin (Organo) were added to acetonitrile, and the mixture was stirred at room temperature for 3 days. The solution was filtered through a 0.2 μm filter, and the filtrate was dried under reduced pressure at 80 °C to obtain a yellow product.

[0155] Transmission electron microscope images of the product obtained in Synthesis Example 1 are shown below. Figure 16 As shown in the figure, the product is confirmed to be a plate-like substance. Furthermore, the electron energy loss spectrum (EELS) results of this product are as follows... Figure 17 As shown, the splitting peaks at 193 eV and 202 eV can be confirmed. The former belongs to the transition from the 1s orbital to the π* orbital of boron, and the latter belongs to the transition from the 1s orbital to the σ* orbital, demonstrating that boron is composed of a two-dimensional sp2 hybrid orbital network. Figure 18 The figure shows the infrared spectrum (FT-IR) of the product. As shown in the figure, at 2500 cm⁻¹... -1 and 1400cm -1 BH and BHB vibrations were observed, confirming that it is a borohydride sheet with a two-dimensional network.

[0156] (Example 1)

[0157] 2.8 mg of the borohydride tablets obtained in Synthesis Example 1 and 0.2 mg of N3 pigment (cis-bis(isothiocyanate)bis(2,2'-bipyridine-4,4'-dicarboxylic acid)ruthenium(II)) as shown in chemical formula (1) were dispersed in 5 mL of acetonitrile to obtain the borohydride composition of Example 1.

[0158] [Chemical Formula 1]

[0159]

[0160] The UV-Vis spectrum of the obtained composition is as follows Figure 19 As shown in the figure. The UV-Vis spectrum of Comparative Example 1, described later, is also shown in this figure. As shown in the figure, the composition of Example 1 has absorption over a wide visible light region.

[0161] (Example 2)

[0162] 2.8 mg of the boron hydride sheet obtained in Synthesis Example 1 was mixed with 0.2 mg of N3 dye to obtain a powder of the composition of Example 2.

[0163] (Example 3)

[0164] 2.8 mg of the boron hydride sheet obtained in Synthesis Example 1, 0.2 mg of N3 dye, and 2 mL of TEOA (triethanolamine) as a hole-trapping agent were dispersed in 3 mL of acetonitrile to obtain the composition of Example 3.

[0165] (Example 4)

[0166] An acetonitrile dispersion liquid (0.05 mol / L) of the boron hydride sheet was mixed with an acetonitrile dispersion liquid (0.000065 mol / L) of AuCl3 (manufactured by Fuji Photo Film Co., Ltd.). The UV-Vis spectrum of the mixture after 1 hour is shown in Fig. 4. As shown in the figure, the composition of Example 4 has an absorption in a wide visible light region. Figure 20

[0167] (Example 5)

[0168] A powder of the composition of Example 5 was obtained by vacuum drying the composition of Example 4. The amount of gold added to the entire composition of Example 5 was 2.7 mass%. The TEM image of the obtained powder is shown in Fig. 5. As shown in Fig. 6, it was confirmed that gold was supported on the boron hydride sheet. Figure 21 Figure 21

[0169] (Examples 6 to 8)

[0170] The compositions of Examples 6 to 8 were obtained by the same method as in Examples 4 and 5, except that the amount of gold added to the entire composition was changed to 5, 10, and 13 mass%, respectively. The TEM images of the powder of the compositions of Examples 6 to 8 are shown in Figs. 7 to 9, respectively. In all of the compositions, it was confirmed that gold was supported on the boron hydride sheet. Figures 22-24

[0171] (Examples 9 and 10)

[0172] A powder of Example 9 was obtained by vacuum drying the composition of Example 1. In addition, a powder of Example 10 was obtained by vacuum drying a composition synthesized by replacing the dye of Example 1 with 4-4' bipyridine from N3.

[0173] (Comparative Example 1)

[0174] ​​​​2.8 mg of the boron hydride-containing sheet obtained in Synthesis Example One was dispersed in 5 mL of acetonitrile to obtain the composition of Comparative Example One.

[0175] (Comparative Example Two)

[0176] 0.2 mg of the N3 pigment was dispersed in 5 mL of acetonitrile to obtain the composition of Comparative Example Two.

[0177] (Reference Example One)

[0178] The powder of the boron hydride-containing sheet obtained in Synthesis Example One was used as Reference Example One.

[0179] (Comparative Example Three)

[0180] Magnesium (Mg) powder, boron (B) powder, and graphite (C) powder were mixed in a molar ratio of Mg:B:C = 1:2-2x:2x (x is an arbitrary value) and calcined at 900°C for 48 hours under an inert atmosphere by the Powder-in-closed-tube method described in A. Yamamoto, et al. Supercond. Sci. Technology. 17, 921, 2004. to obtain a powder in which carbon was doped in the lattice of MgB2. In Comparative Example Three, the value of x was 0.02, i.e., MgB2 powder in which the amount of carbon doping was 2% was synthesized.

[0181] Next, as in Synthesis Example One, 500 mg of the MgB2 powder in which the amount of carbon doping was 2% was mixed with 30 mL of a cation exchange resin (Organo Co., Ltd.) in acetonitrile and stirred at room temperature for 3 days. The solution was filtered using a filter having a pore size of 0.2 μm, and the filtrate was dried under reduced pressure at 80°C to obtain a product.

[0182] (Comparative Example Four)

[0183] A product of Comparative Example Four was obtained by the same method as in Comparative Example Three, except that the value of x in Comparative Example Three was changed to 0.04.

[0184] (Evaluation One)

[0185] The hydrogen release amount of the composition obtained in Example One was evaluated by the following method. That is, 5 mL of the composition obtained in Example One was put in a closed quartz glass container 60, and the container was heated at a rate of 5°C / min to 800°C and held at 800°C for 1 hour, and then cooled to room temperature at a rate of 5°C / min. The amount of hydrogen released from the composition was measured by a gas chromatograph. Figure 25As shown, a light source is disposed to irradiate visible light to the measurement sample 63 through the quartz glass plate. The quartz glass container 60 is set to a nitrogen atmosphere, and the amount of hydrogen released is measured by analyzing the gas in the container with a micro GC. The distance between the lower surface of the measurement sample 63 and the visible light source is 2 cm. The measurement sample 63 is left in a dark room for 2 hours, and then the amount of hydrogen released when visible light is irradiated is measured with a gas chromatograph GC-2010 Plus (manufactured by Shimadzu Corporation) equipped with a dielectric barrier discharge ionization detector. As the visible light source, a super bright 500XEF-501S (manufactured by Tokina Corporation, 500 W, 25.0 A) is used, and light of 470 nm or less is cut off by the cut filter 61. Figure 26 The spectrum of the irradiated light is shown.

[0186] In Figure 27 , a graph showing the amount of hydrogen released with respect to the visible light non-irradiation (dark) and the visible light irradiation time for Example 1, Comparative Example 1, and 2 is shown. As shown in the graph, it is confirmed that all the samples do not substantially generate hydrogen when not irradiated, and the amount of hydrogen released by the composition of Example 1 is significantly higher than that of Comparative Example 1 by visible light irradiation. The internal quantum efficiency with respect to the amount of hydrogen released of Example 1 is 4.42%. The internal quantum efficiency is calculated from the absorption spectrum of the composition and the spectrum of the light source, the number of absorbed photons is calculated, and the value after subtracting the number of electrons required for hydrogen generation as a 2-electron reaction is calculated.

[0187] (Evaluation 2)

[0188] With respect to the composition of Example 1, the hydrogen generation rate per 1 hour of light irradiation is measured by the same method as Evaluation 1 except that the light source is used as a monochromatic light source. With respect to the monochromatic light source, the visible light source super bright 500XEF-501S (manufactured by Tokina Corporation, 500 W, 25.0 A) described in Evaluation 1 is used, and the sample is irradiated with various bandpass filters (wavelength: 757, 650, 550, 450, 340 nm). The results (action spectrum) thereof, which overlap with the UV-Vis absorption spectrum of the composition of Example 1, are shown in Figure 28 As shown in the graph, since the action spectrum and the absorption spectrum coincide, it is shown that the generation of hydrogen is induced by photoexcitation of the composition of Example 1.

[0189] (Evaluation 3)

[0190] With respect to the composition of Example 1, the amount of hydrogen released is measured by the same method as Evaluation 1 except that the distance between the light source and the sample is changed over time, and 3 mL of the composition obtained in Example 1 is used. The results thereof are shown in Figure 29As shown in the figure, it is confirmed that the amount of hydrogen released varies with the distance from the light source, that is, with the intensity of the light.

[0191] (Evaluation 4)

[0192] use Figure 25 The apparatus shown was used to determine the hydrogen release of the powdered composition of Example 2. The results are as follows: Figure 30 As shown in the figure, hydrogen is indeed released in the powder system.

[0193] (Evaluation 5)

[0194] use Figure 25 The apparatus shown was used to determine the hydrogen release of the composition of Example 3. Specifically, 5 mL of the sample was placed in a quartz glass container 60, and the position of the light source was adjusted so that the distance between the quartz glass container 60, which was in contact with the sample, and the xenon light source 62 (super bright 500XEF-501S (Tokina), 500W, 25.0A) was 2 cm. Additionally, a cutoff filter 61 was used to block light below 470 nm. The results, as well as the results of Example 1 obtained in Evaluation 1, are as follows... Figure 31 As shown in the figure, it is confirmed that adding a hole trap increases hydrogen release.

[0195] (Evaluation 6)

[0196] Regarding the composition of Example 1, the hydrogen release was determined using the same method as in Evaluation 1, except that the following procedures were performed. Specifically, in this Evaluation 5, after 90 hours of visible light irradiation, light irradiation was stopped, and 1 mg of N3 as a pigment was added. Then, after 5 hours of non-irradiation, visible light irradiation was performed again for 45.5 hours, after which light irradiation was stopped, and 1 mL of formic acid as a proton donor was added. Then, after 7.5 hours of non-irradiation, visible light irradiation was performed again. The hydrogen release at this time was as follows... Figure 32 As shown in the figure, even with the addition of N3, the hydrogen release did not increase, but the hydrogen release increased with the addition of formic acid. The saturation of hydrogen release after about 100 hours of irradiation was not caused by pigment decomposition, but by the release of hydrogen from the borohydride-containing tablets, confirming that hydrogen can be continuously produced from the borohydride-containing tablets by adding a proton donor.

[0197] (Evaluation 7)

[0198] Regarding the composition of Example 5, the hydrogen release was determined using the same method as in Evaluation 1. The results are as follows: Figure 33 As shown in the figure, it is confirmed that hydrogen release is significantly increased by visible light irradiation compared to the unirradiated state.

[0199] (Evaluation 8)

[0200] The results of measuring the amount of hydrogen released with respect to the powdered composition of Examples 9 and 10, in which visible light was irradiated in nitrogen, are shown in Figure 34 In the graph, the time at which visible light irradiation was started is indicated by an arrow. In the graph, the results of Reference Example 1 (boron hydride sheet to which no electron donor was added) are also shown for comparison. As shown in the graph, it was confirmed that the amount of hydrogen released was significantly increased by visible light irradiation when the powdered composition was irradiated with visible light, as compared with the case where no irradiation was performed.

[0201] (Evaluation 9)

[0202] With respect to the powdered products of Comparative Examples 3 and 4, the wide band gap was calculated by Tauc-plot. The calculation results are shown in Figure 35 In the graph, the results of Reference Example 1 (boron hydride sheet to which no electron donor was added) are also shown for comparison. As shown in the graph, it was confirmed that the wide band gap energy was increased when carbon was doped in the boron hydride sheet, as compared with the case where no electron donor was added to the boron hydride sheet (C: 0%). That is, it was found that the boron hydride sheet could not absorb visible light due to the expansion of the light absorption band of the boron hydride sheet. It was thus found that even if only a heterogeneous element such as carbon was doped in the boron hydride sheet, absorption of visible light would not occur.

[0203] This application claims priority from Japanese Application No. 2021-117864, filed July 16, 2021, the entire disclosure of which is incorporated herein by reference.

[0204] Explanation of Reference Numerals

[0205] 1-5 Hydrogen production system

[0206] 10 Hydrogen production section

[0207] 11 Raw material supply tank

[0208] 12 Solvent supply path

[0209] 13 Gas recovery path

[0210] 14 Discharge path

[0211] 15 Agitation section

[0212] 16 Gas supply path

[0213] 17 Gas flow generation section

[0214] 18 Thin container

[0215] 19 Conveyor belt

[0216] 20 External stimulus control section

[0217] 21 LED light source

[0218] 30 boron hydride containing composition

[0219] 31 boron hydride containing sheet

[0220] 32 solvent

[0221] 40 carrier bead

[0222] 41 bead

[0223] 50 film

[0224] 51 adhesive

Claims

1. A boron hydride containing composition comprising a boron hydride containing sheet and an electron donor, the boron hydride containing sheet having a two-dimensional network comprising (BH)n, n > 4, and n is an integer. n 2. The boron hydride containing composition of claim 1, wherein the boron hydride containing sheet has a two-dimensional network comprising (BH)n, n > 4, and n is an integer, and the electron donor is selected from the group consisting of amines, ethers, alcohols, at least a part of the electron donor is carried on the surface of the boron hydride sheet, a LUMO (lowest unoccupied molecular orbital) or a conduction band level of the electron donor is lower than a conduction band level of the boron hydride sheet, by an external stimulus, an electron of the electron donor is supplied to the boron hydride sheet, and hydrogen is generated from the boron hydride sheet into which the electron is injected.

2. The boron hydride composition according to claim 1, wherein the electron donor is excited by visible light, and by supplying the excited electron to the boron hydride sheet, hydrogen is generated from the boron hydride sheet.

3. The boron hydride composition according to claim 1, wherein the electron donor is an organic compound.

4. The boron hydride composition according to claim 1, wherein the electron donor has at least any one of a carboxyl group, a phosphono group, and a sulfonic acid group.

5. The boron hydride composition according to claim 1, wherein the boron hydride composition contains a solvent.

6. The boron hydride composition according to claim 1, wherein the boron hydride composition further contains a hole-trapping agent.

7. The boron hydride composition according to claim 6, wherein a redox potential of the hole-trapping agent is lower than a HOMO (highest occupied molecular orbital) or a valence band level of the electron donor.

8. The boron hydride composition according to claim 1, wherein the boron hydride composition further comprises a proton donor.

9. The boron hydride composition according to claim 8, wherein the proton donor is an acid.

10. A hydrogen generation system comprising the boron hydride composition according to any one of claims 1 to 9, the hydrogen generation system having: a boron hydride composition; a control section that controls on-off of an external stimulus to the boron hydride composition; and a hydrogen generation section that takes out hydrogen to the outside.

11. A fuel cell system having the hydrogen generation system according to claim 10 and a fuel cell, the hydrogen generation system supplying hydrogen to the fuel cell. ​ ​ ​

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