Boric acid-containing composition, hydrogen generation system, and fuel cell system

Abstract

The present invention provides: a borohydride-containing composition which enables further improvement in the performance of a hydrogen supply source that uses a borohydride-containing sheet; a hydrogen generation system; and a fuel cell system. A borohydride-containing composition according to the present invention comprises: a borohydride-containing sheet which has a two-dimensional network that is composed of (BH)n (wherein n ≥ 4, provided that n is an integer); and an electron donor. At least some of the electron donor is supported by the borohydride-containing sheet; electrons of the electron donor are supplied to the borohydride-containing sheet by external stimuli; and hydrogen is generated from the borohydride-containing sheet into which the electrons have been injected.

Description

[Technical Field] 【0001】 This invention relates to a hydrogen boride-containing composition and a hydrogen generation system. It also relates to a fuel cell system using the hydrogen generation system. [Background technology] 【0002】 Hydrogen is attracting attention as a clean energy source because its combustion or reaction emits water. While high-pressure cylinders have traditionally been used as a hydrogen source, the explosive nature of hydrogen has led to vigorous efforts to develop safer hydrogen supply systems. 【0003】 A method of supplying hydrogen for fuel cells using a hydrogen storage alloy has been disclosed (Patent Document 1). In addition, the present inventors recently proposed a boron-containing sheet from which hydrogen can be extracted by heat treatment at a relatively low temperature of 200°C or less (Non-Patent Document 1, Patent Document 2). Furthermore, they reported a method for easily releasing hydrogen from a boron-containing sheet by ultraviolet irradiation under mild conditions at room temperature (Patent Document 3). [Prior art documents] [Patent Documents] 【0004】 [Patent Document 1] Japanese Patent Publication No. 2005-063703 [Patent Document 2] International Publication No. 2018 / 074518 [Patent Document 3] Japanese Patent Publication No. 2019-218251 [Non-patent literature] 【0005】 [Non-Patent Document 1] Kondo T., Miyauchi M. et al., Photoinduced hydrogen release from hydrogen boride sheets, Nature Communications, 10, 4880 (2019). [Overview of the Initiative] [Problems that the invention aims to solve] 【0006】 Boron-containing sheets have a high hydrogen storage capacity of approximately 8.5 wt% per unit mass and are also lightweight, so further improvements in the performance of boron-containing sheets are desired for practical use as a hydrogen supply source. This invention has been made in view of the above background, and aims to provide a borohydride-containing composition, a hydrogen generation system, and a fuel cell system that further improve the performance of a hydrogen supply source using a borohydride-containing sheet and achieve energy savings in hydrogen production. [Means for solving the problem] 【0007】 After diligent research by the inventors, we discovered that the problems of the present invention can be solved in the following embodiment, and thus completed the present invention. [1]: (BH) n The material contains a borohydride-containing sheet having a two-dimensional network consisting of (n≧4, where n is an integer) and an electron donor. At least a portion of the electron donor is supported on the surface of the borohydride-containing sheet. A borohydride-containing composition in which, upon external stimulation, electrons from the electron donor are supplied to the borohydride-containing sheet, and hydrogen is generated from the borohydride-containing sheet to which the electrons have been injected. [2]: The borohydride-containing composition according to [1], characterized in that the LUMO (lowest unoccupied orbital) or conduction band level of the electron donor is less noble than the conduction band level of the borohydride-containing sheet. [3]: The boron-containing composition according to [1] or [2], wherein the electron donor is excited by visible light, and hydrogen is generated from the boron-containing sheet by supplying the excited electrons to the boron-containing sheet. [4]: The borohydride-containing composition according to any one of [1] to [3], characterized in that the electron donor is an organic compound. [5]: The borohydride-containing composition according to any one of [1] to [4], characterized in that the electron donor has at least one of a carboxyl group, a phosphono group, and a sulfonic acid group. [6]: A borohydride-containing composition according to any one of [1] to [5], characterized by containing a solvent. [7]: A borohydride-containing composition according to any one of [1] to [6], further comprising a hole-catching agent. [8]: The hydrogen boride-containing composition according to [7], characterized in that the oxidation-reduction potential of the hole trapper is lower than the HOMO (highest occupied orbital) or valence band level of the electron donor. [9]: A borohydride-containing composition according to any one of [1] to [8], further characterized by containing a proton donor.

[10] : The boron-containing composition according to [9], characterized in that the proton donor is an acid.

[11] : A hydrogen generation system comprising a borohydride-containing composition as described in any of [1] to

[10] , A composition containing hydrogen boride, A control unit that controls the on / off switching of external stimuli to the borohydride-containing composition, A hydrogen generation system equipped with a hydrogen generation unit that extracts hydrogen to the outside.

[12] : A fuel cell system comprising the hydrogen generation system described in

[11] and a fuel cell supplied with hydrogen from the hydrogen generation system. [Effects of the Invention] 【0008】 According to the present invention, there is an excellent effect that a hydrogen source using a boron hydride-containing sheet can be provided, and a boron hydride-containing composition, a hydrogen generation system, and a fuel cell system that can realize further performance improvement of the hydrogen source and energy saving of hydrogen generation can be provided. 【Brief Description of Drawings】 【0009】 [Figure 1] Schematic diagram showing a local structure of a two-dimensional network composed of (BH)n (n≥4) according to this embodiment. [Figure 2] Schematic diagram showing a local structure of a two-dimensional network composed of (BH)n (n≥4) according to this embodiment. [Figure 3] Schematic diagram showing a local structure of a two-dimensional network composed of (BH)n (n≥4) according to this embodiment. [Figure 4] Schematic diagram showing an example of a hydrogen release mechanism of this composition using a dye. [Figure 5] Schematic diagram showing an example of a hydrogen release mechanism of this composition using a semiconductor. [Figure 6] Schematic diagram showing an example of a hydrogen release mechanism of this composition using a metal. [Figure 7] Schematic diagram showing an example of a hydrogen release mechanism of this composition by heat. [Figure 8] Schematic diagram showing an example of a hydrogen release mechanism of this composition using a dye and a hole scavenger. <00001​​​​​​​​​​​​​​​A schematic diagram showing an example of the main components of a hydrogen generation system according to the fourth embodiment. [Figure 15] A schematic diagram showing an example of a film used in a hydrogen generation system according to the fifth embodiment. [Figure 16] Transmission electron microscope image of the product from Example 1. [Figure 17] A graph showing the EELS measurement results of the product from Example 1. [Figure 18] A graph showing the FT-IR measurement results of the product from Example 1. [Figure 19] UV-Vis spectra of the compositions of Example 1 and Comparative Example 1. [Figure 20] UV-Vis spectrum of the composition of Example 4. [Figure 21] TEM image of the composition of Example 5. [Figure 22] TEM image of the composition of Example 6. [Figure 23] TEM image of the composition of Example 7. [Figure 24] TEM image of the composition of Example 8. [Figure 25] A schematic diagram illustrating a device for evaluating hydrogen gas emission levels. [Figure 26] The spectrum of the irradiation light used in the hydrogen gas emission evaluation device. [Figure 27] A graph plotting the amount of hydrogen gas released against the visible light irradiation time of compositions such as Example 1. [Figure 28] Action spectrum and UV-Vis absorption spectrum of the composition of Example 1. [Figure 29] A graph showing the results of visible light irradiation intensity and hydrogen gas emission for the composition of Example 1. [Figure 30] A graph plotting the amount of hydrogen gas released against the visible light irradiation time for compositions such as Example 2. [Figure 31] A graph plotting the amount of hydrogen gas released from the compositions of Examples 1 and 3 against visible light irradiation time. [Figure 32] A graph plotting the amount of hydrogen gas released from the composition of Example 1 against visible light irradiation time (effect of post-addition of dye and proton donor). [Figure 33] A graph plotting the amount of hydrogen gas released from the composition of Example 4 against the visible light irradiation time. [Figure 34] A graph plotting the amount of hydrogen gas released from compositions such as those in Examples 9 and 10 against the visible light irradiation time. [Figure 35] Graphs plotting the band gaps of the powdered products of Comparative Examples 4 and 5 and Reference Example 1 using Tauc-plot. [Modes for carrying out the invention] 【0010】 The following describes an example of an embodiment to which the present invention is applied. Other embodiments are also included within the scope of the present invention, as long as they are consistent with the spirit of the present invention. Furthermore, the sizes and proportions of the components in the following figures are for illustrative purposes only and are not limiting. 【0011】 The borohydride-containing composition of this embodiment (hereinafter also referred to as "this composition") is (BH) n The material contains a boron-containing sheet (hereinafter also referred to as the "boron-containing sheet"), which is a sheet-like material having a two-dimensional network consisting of (n≧4, where n is an integer), and an electron donor. At least a portion of the electron donor is supported on the surface of the boron-containing sheet. When an external stimulus is applied, electrons from the electron donor are supplied to the boron-containing sheet, and hydrogen is generated from the boron-containing sheet to which the electrons have been injected. 【0012】 In this specification, "supported" includes a state in which the borohydride-containing composition is chemically adsorbed onto the surface of the borohydride-containing sheet, or a state in which it is physically attached to the borohydride-containing sheet. Furthermore, "external stimulus" refers to any stimulus that can be applied to the borohydride-containing composition to supply electrons from an electron donor to the borohydride-containing sheet, thereby generating hydrogen gas. Specific examples include irradiation with energy rays such as heat, infrared rays, visible light, ultraviolet rays, and electron beams. 【0013】 This composition contains an electron donor that induces hydrogen generation from a borohydride-containing sheet, thereby increasing hydrogen generation efficiency. Furthermore, the selection of the electron donor type offers the excellent advantage of allowing the selection of external stimuli according to needs and applications. For example, since hydrogen can be released not only by ultraviolet light but also by visible light, which is abundant in sunlight and white lighting, it is expected to have a wide range of applications as a hydrogen-releasing material utilizing renewable energy and everyday lighting. While this embodiment can generate hydrogen at room temperature and atmospheric pressure, it does not preclude the use of heating or pressurizing processes. Each component will be described in detail below. 【0014】 [Boric acid-containing sheet] In this specification, "boronide-containing sheet" means (BH) n This refers to a sheet-like material having a two-dimensional network consisting of (n≧4, where n is an integer). (BH) n A two-dimensional network consisting of (n≧4) is formed with boron atoms (B) and hydrogen atoms (H) in a molar ratio of 1:1 (see Non-Patent Document 1). 【0015】 Boric acid-containing sheets are (BH) n It is sufficient to have a two-dimensional network consisting of (n≧4), (BH) n Compounds whose main framework consists of a two-dimensional network of (n≧4) (e.g., (BH) n This includes compounds in which a dopant has been introduced into a part of a two-dimensional network consisting of (n≧4), compounds whose ends are sealed with oxides, carbides, nitrides, hydroxides, sulfides, etc., and compounds in which organic groups are bonded to the ends. Here, the main skeleton refers to a substance in which the proportion of a boron-containing sheet in the compound is 80% or more. 【0016】 Examples of the dopant include, for example, at least one element selected from the group consisting of elements such as carbon, nitrogen, oxygen, fluorine, phosphorus, sulfur, chlorine, arsenic, selenium, bromine, antimony, tellurium, and iodine; metallic elements such as titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, cadmium, indium, tin, yttrium, niobium, molybdenum, tungsten, tantalum, and lead; and precious metallic elements such as ruthenium, rhodium, palladium, silver, gold, iridium, and platinum. 【0017】 Figures 1 to 3 show (BH) n A schematic diagram of the local structure of a two-dimensional network consisting of (n≧4) is shown. As shown in Figure 1, the two-dimensional network has boron atoms arranged in a hexagonal honeycomb pattern (forming a mesh-like structure made up of interconnected hexagons formed by the boron atoms), and each boron atom has a region where two adjacent atoms bond to the same hydrogen atom. The boron atoms take on a honeycomb-like (honeycomb-like) sheet-like hexagonal lattice structure, and at the top and bottom of the sheet, as shown in Figures 2 and 3, one hydrogen atom is bridge-bonded to two adjacent boron atoms in the hexagonal lattice structure. In addition, there is a configuration where two hydrogen atoms face each other at the top and bottom of the sheet-like hexagonal lattice structure. Note that the arrangement of hydrogen atoms in hydrogen boride does not necessarily have to have long-range order. Also, the bonds between atoms may be tilted in the Z direction in Figures 2 and 3, or the sheet itself may be curved to form a structure. Furthermore, not all hydrogen atoms necessarily have to be bonded to a bridge. 【0018】 The borohydride-containing sheet is a thin film and may consist of a single layer or multiple layers. In the borohydride-containing sheet of this embodiment, the total number of boron atoms (B) and hydrogen atoms (H) that form the above-mentioned mesh-like surface structure is 1000 or more. 【0019】 The bond distance d1 between two adjacent boron atoms (B) (see Figure 1) is, for example, 0.155 nm to 0.190 nm. Also, when viewed from the Z direction, the bond distance d2 between two adjacent boron atoms (B) via one hydrogen atom (H) (see Figure 2) is, for example, 0.155 nm to 0.190 nm. Furthermore, the bond distance d3 between adjacent boron atoms (B) and hydrogen atoms (H) (see Figure 2) is, for example, 0.12 nm to 0.15 nm. 【0020】 The thickness of the borohydride-containing sheet is, for example, 0.2 nm to 10 nm. Preferably, the length of the borohydride-containing sheet in at least one direction (for example, the length in the X or Y direction in Figure 1) is 100 nm or more. By making the length in at least one direction 100 nm or more, the borohydride-containing sheet can be used more effectively as an electronic material, a catalyst support material, a catalyst material, a superconducting material, etc. The size (area) of the borohydride-containing sheet is not particularly limited and can be formed to any size. 【0021】 The boron-containing sheet of this embodiment is a material having a crystalline structure. Furthermore, the boron-containing sheet of this embodiment exhibits strong bonding forces between boron atoms (B) that form hexagonal rings, and between boron atoms (B) and hydrogen atoms (H). Therefore, even if the boron-containing sheet of this embodiment forms a crystal (aggregate) consisting of multiple layers during manufacturing, it can be easily cleaved along the crystal planes, similar to graphite, and separated (recovered) as a single-layer two-dimensional sheet. 【0022】 Compared to hydrogen storage alloys, boric acid-containing sheets offer significantly superior lightness. Furthermore, they are safer because they can be used at atmospheric pressure. However, this does not preclude use under conditions other than atmospheric pressure. 【0023】 The method for producing a borohydride-containing sheet is not particularly limited. For example, it can be produced by the following method. Specifically, first, a metal diboride with an MB2 structure and an ion exchange resin coordinated with ions that can exchange ions with the metal ions constituting the metal diboride 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. This mixing step can be carried out under an inert atmosphere consisting of an inert gas such as nitrogen (N2) or argon (Ar). 【0024】 As MB2-type metal diborides, those having a hexagonal ring structure are 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) are used. Magnesium diboride is preferred because it can easily perform ion exchange with ion exchange resins in polar organic solvents. 【0025】 The ion exchange resin having coordinated ions capable of ion exchange with the metal ions constituting the metal diboride is not particularly limited. Examples of such ion exchange resins include polymers of styrene having a functional group (hereinafter referred to as "functional group α") coordinated with ions capable of ion exchange with the metal ions constituting the metal diboride, polymers of divinylbenzene having functional group α, and copolymers of styrene having functional group α and divinylbenzene having functional group α. Examples of functional group α include sulfo groups and carboxyl groups. Among these, sulfo groups are preferred because they can easily perform ion exchange with the metal ions constituting the metal diboride in polar organic solvents. 【0026】 Acids may be added further during the mixing process. Examples of acids include 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. By adding an acid, the time required for ion exchange between the metal ions constituting the metal diboride and the ion exchange resin in a polar solvent can be significantly reduced. 【0027】 The polar organic solvent is not particularly limited, and examples include acetonitrile, N,N-dimethylformamide, and methanol. 【0028】 If acid is used in the mixing process, remove the acid as necessary. The method of acid removal is not particularly limited, but examples include heating, vacuum drying, and precipitation recovery. 【0029】 Subsequently, the mixed solution is filtered. For example, methods such as natural filtration, vacuum filtration, pressure filtration, and centrifugal filtration are used. The solution containing the product, which has been separated from the precipitate by filtration, is dried by natural drying, vacuum drying, heating, etc., to finally obtain a boron-containing sheet having a two-dimensional network, which is the final product. 【0030】 [Electron Child Donor] As described above, in this specification, an "electron donor" refers to a substance that can supply electrons to a boron hydride-containing sheet upon external stimulation, and hydrogen can be generated from the boron hydride-containing sheet into which the electrons are injected. It is preferable that the LUMO (lowest unoccupied molecular orbital) or conduction band level of the electron donor is lower than the conduction band level of the boron hydride-containing sheet. Specific examples of the electron donor include a light absorber and a heat absorber. As these specific examples, organic compounds can be exemplified. Further, substances exhibiting metallic properties and substances exhibiting semiconductor properties can be exemplified. Examples of substances exhibiting metallic properties include metals, metal oxides, metal nitrides, metal carbides, metal oxynitrides, and metal oxycarbides. Examples of substances having semiconductor properties include semiconductors, metal nitrides, metal sulfides, and metal oxides. These can be used alone or in any combination. When visible light is used as the external stimulation, a dye is a preferred example of an organic compound. Here, a dye refers to a compound that selectively absorbs visible light in a specific wavelength range and thereby causes color vision. 【0031】 Functional groups may be introduced into the electron donor to increase the loading rate on the boron hydride-containing sheet. Examples of such functional groups include a carboxy group, a phosphono group, and a sulfonic acid group. Among these, the carboxy group is preferred. 【0032】 An example of the mechanism of the hydrogen generation mechanism of this composition when a dye is used as the electron donor will be described using FIG. 4. However, the present invention is not limited to this mechanism. In the example of FIG. 4, an example using visible light as the external stimulation will be described. Visible light is absorbed by the dye, and the electrons of the dye are excited from the HOMO (highest occupied molecular orbital) to the LUMO (lowest unoccupied molecular orbital) by this light absorption. As a result, holes (h + ) are generated in the dye. Then, through the process of injecting the excited electrons into the hydrogen ions at the conduction band level that constitutes the anti-bonding orbital of hydrogen in the boron hydride-containing sheet, the reaction of 2H + + 2e - → H2↑ occurs, and it is considered that hydrogen is extracted. 【0033】 An example of the hydrogen generation mechanism when a semiconductor is used as an electron donor will be explained using Figure 5. However, the present invention is not limited to this mechanism. In this example, an example in which light irradiation is used as an external stimulus will be explained. Light is absorbed by the semiconductor, and this light absorption excites electrons from the valence band to the conduction band of the semiconductor. It is thought that hydrogen is released when these excited electrons are injected into the hydrogen ions in the conduction band level, which are the antibonding orbitals of hydrogen in the hydrogen boride-containing sheet. Heat may be used as an external stimulus instead of or in combination with light irradiation. The irradiation wavelength may be appropriately selected depending on the semiconductor used. Multiple semiconductors with different excitation wavelengths may be used in combination, and multiple irradiation wavelengths or irradiation bands may be utilized. 【0034】 An example of the hydrogen generation mechanism when a metal is used as an electron donor will be explained using Figure 6. However, the present invention is not limited to this mechanism. In this example, an example in which light irradiation is used as an external stimulus will be explained. Light is absorbed by the metal, and this light absorption excites electrons from the metal's HOMO to empty orbitals of the metal, such as s or d orbitals. It is thought that hydrogen is released when these excited electrons are injected into hydrogen ions in the conduction band level, which are the antibonding orbitals of hydrogen in the hydrogen boride-containing sheet. Heat may be used as an external stimulus instead of or in combination with light irradiation. The irradiation wavelength may be appropriately selected depending on the metal used. Multiple metals with different excitation wavelengths may be used in combination, and multiple irradiation wavelengths or irradiation bands may be utilized. 【0035】 The aforementioned dye is not particularly limited as long as it has photosensitizing properties. Preferred examples include 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"), and tri(thiocyanato)-(4,4',4''-tricarboxy Examples of ruthenium-based sensitizing dyes include tris-tetrabutylammonium salt of c-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'-bitienyl))bipyridyl)ruthenium(II) (hereinafter also referred to as "black dye"), C106, and iridium-based sensitizing dyes such as tris(2-pyridylphenyl)iridium(III). Furthermore, various organic sensitizing dyes such as coumarin, polyene, cyanine, hemicyanine, thiophene, indoline, xanthene, carbazole, perylene, porphyrin, phthalocyanine, merocyanine, catechol, azo, azine, and squarylium are also suitable. In addition, donor-acceptor complex sensitizing dyes, which are combinations of these sensitizing dyes, may be used. The dyes can be used individually or in combination of two or more. It is preferable that the dyes contain at least one of N3, N719, N712, and C106. 【0036】 A substance having metallic properties is defined as a substance that possesses a metallic electronic structure, in which the electrons of the metal are excited by photosensitization or heat, and the excited electrons can be supplied to a borohydride-containing sheet. The type of substance is not particularly limited. Preferred examples include metals containing at least one 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, as well as alloys thereof. Compounds such as metal carbides and metal nitrides can also be used. Examples of metal carbides include TiC, ZrC, HfC, TaC, and WC. These exhibit metallic properties and can be used as electron donors. Examples of metal nitrides include TiN, ZrN, HfN, TaN, and WN. These metal nitrides exhibit metallic properties and all function as electron donors. Alternatively, metallic oxynitrides, metallic carbides, and compounds containing oxygen ions with metallic properties can also be used. 【0037】 A semiconductor-like substance is one in which electrons are excited by light irradiation or heat, and these excited electrons can be supplied to a borohydride-containing sheet. The type of substance is not particularly limited. Preferred examples include oxides such as tungsten oxide, bismuth oxide, iron oxide, nickel oxide, cobalt oxide, bismuth vanadate, and calcium iron ferrite; nitrides such as tantalum nitride; sulfides such as cadmium sulfide, zinc sulfide, indium sulfide, tin sulfide, and lead sulfide; and semiconductors such as selenides, tellurides, and phosphides. Semiconductor quantum dots with a diameter of about 5 to 20 nm are preferred from the viewpoint of electron injection efficiency and control of response wavelength. 【0038】 When light absorption occurs in metals (including materials exhibiting metallic properties) or semiconductors (including materials exhibiting semiconducting properties), heat is generated by the recombination of excited carriers. This heat acts as an external stimulus, as shown in Figure 7, and can induce hydrogen production from a boron-containing sheet. In particular, in metals, plasmon absorption occurs, creating a near-field that triggers a photothermal effect. This heat promotes efficient hydrogen production from the boron-containing sheet. While electron injection from an electron donor to the boron-containing sheet is not always necessary when generating hydrogen by photoheating, using an electron donor can increase the hydrogen production efficiency. 【0039】 [solvent] This composition can be used in powder form without a solvent, but it may also be dissolved or dispersed in a solvent. Examples of solvents include water or organic solvents. Organic solvents are not particularly limited, but examples include amide solvents, alcohol solvents, ester solvents, ketone solvents, nitrile solvents, aromatic hydrocarbon solvents, halogenated hydrocarbons, ethers, amides, carbonate esters, hydrocarbons, and nitromethane. Examples of nitrile solvents include acetonitrile, isobutyronitrile, and propyronitrile, and examples of alcohol solvents include methanol, ethanol, and propanol. The solvent may be used alone or in combination of two or more. 【0040】 [Hole trapping agent] This composition may further contain a hole trapper. The hole trapper traps holes generated in the electron donor by external stimuli and enters an oxidized state itself, thereby preventing degradation of the electron donor due to self-oxidation. The oxidation-reduction potential of the hole trapper is preferably lower than the HOMO (highest occupied orbital) or valence band level of the electron donor. 【0041】 Figure 8 shows a schematic diagram illustrating an example of the hydrogen generation mechanism when a hole trapping agent is used in this composition. However, the present invention is not limited to this mechanism. In this example, an example using visible light as an external stimulus is described. Visible light is absorbed by the dye, and this light absorption excites the electrons of the dye from the HOMO (highest occupied orbital) to the LUMO (lowest unoccupied orbital). At this time, the dye is filled with holes (h + Although this reaction occurs, the hole trapper supplies electrons to the dye, thus suppressing the dye's self-oxidation. Through this reaction, the hole trapper is oxidized, and the dye continues to function as an electron donor. By appropriately replenishing the hole trapper, it is possible to increase the hydrogen generation capacity while suppressing the amount of dye added. 【0042】 The hole trapper is not particularly limited as long as it has the above-mentioned function. Suitable examples include triethanolamine (TEOA), ascorbic acid; 1-benzyl-1,4-dihydronicotinamide; benzimidazole derivatives; alcohols such as methanol, ethanol, butanol, and propyl alcohol; aldehydes such as formaldehyde and acetaldehyde; carboxylic acids such as formic acid, acetic acid, and propionic acid; bromide ions, iodide ions, iodate ions, and iron ions (Fe 2+ Examples include redox reagents such as ferrocene, photocatalytically active ethylenediaminetetraacetic acid (EDTA), sodium formate, and polysulfide ions. 【0043】 The hole trapper may be reused by reducing the oxidized state in which it has trapped holes. Examples of methods for reducing the hole trapper include mixing a chemical reducing agent such as sodium borohydride, hydrazine, or aldehydes into the composition. Alternatively, or in combination with the above method, the hole trapper can also be reduced electrochemically by contacting the composition with a cathode electrode (not shown). 【0044】 [Proton donor] This composition may further contain a proton donor. A proton donor is a compound that can donate protons, and may be soluble in liquid or dispersed without dissolving. Preferred proton donors include inorganic acids, organic acids such as carboxylic acids, sulfonic acids and phenols, alcohols, mercaptans, and 1,3-dicarbonyl compounds. Solid acids such as zeolites and ion exchange resins are also suitable. Formic acid is an example of a suitable proton donor. 【0045】 Figure 9 shows a schematic diagram illustrating an example of the hydrogen generation mechanism when a proton donor is used in this composition. An example of the hydrogen generation mechanism will be explained from this figure. However, the present invention is not limited to this mechanism. In addition to the boron-containing sheet, a proton donor is used as a hydrogen supply source. This provides a hydrogen source to replace the lost boron, and the amount of hydrogen released can be increased. 【0046】 [Other additives] This composition may contain polymeric or low molecular weight compounds such as binder resins and dispersants, without departing from the spirit of the present invention. Furthermore, additives such as antistatic agents, thermally conductive fillers, and flame retardants may be added as appropriate. 【0047】 [Hydrogen boride-containing composition] This composition can be used as a powder. It may also be used as a solution, dispersion, or slurry by adding a solvent. Furthermore, this composition may be made into a film or a molded body of any shape. The film or molded body may be porous. A laminate may be used in which a hole-catching agent layer is laminated on one main surface of a film containing a borohydride-containing sheet and an electron donor supported thereon, and a proton-donor layer is laminated on the other main surface. The method for producing a 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 preparing the composition in advance, the components of the composition may be added at the time of use. 【0048】 [Sustainable hydrogen generation system] By incorporating a regenerative hole trapper and a proton donor into this composition, degradation of the boron-containing sheet and electron donor due to external stimuli can be prevented, and hydrogen can be continuously generated. That is, even after hydrogen is released from the boron-containing sheet, a hydrogen source is supplied from the proton donor. In addition, the electron-hole pairs of the electron donor move to the boron-containing sheet and hole trapper, respectively, suppressing degradation of the electron donor itself due to self-oxidation or self-reduction. 【0049】 Figure 10 illustrates an example of a method for electrochemically reducing a hole trapper. In this figure, a dye is used, and hydrogen is released using visible light as an external stimulus. Simultaneously, a cathode and anode are placed in a solvent dispersion system containing the composition, and the redox reagent is regenerated in the dark using an external electric field. This electrochemically reduces the hole trapper, making it possible to continuously reuse the hole trapper. Furthermore, by adding a proton donor, hydrogen release from the boron-containing sheet can be supplemented. 【0050】 [Hydrogen generation system] The hydrogen generation system according to this embodiment utilizes the boron-containing composition described above and comprises the boron-containing composition, a control unit that controls the on / off switching of external stimuli to the boron-containing composition, and a hydrogen generation unit that extracts hydrogen to the outside. This hydrogen generation system can be applied to a wide range of applications where hydrogen generation is desired by external stimuli such as light irradiation. A specific example of an embodiment of the hydrogen generation system will be described below. Each embodiment can be suitably combined. 【0051】 (First Embodiment) Figure 11 shows a schematic diagram of a hydrogen generation system according to the first embodiment. The hydrogen generation system 1 includes a hydrogen generation unit 10 and an external stimulus control unit 20. The hydrogen generation unit 10 is connected to a raw material supply tank 11, a solvent supply passage 12, a gas recovery passage 13, and a discharge passage 14, and includes a container for containing a boron-containing composition 30 and a stirring unit 15 for stirring it. In the example in Figure 11, the boron-containing composition excluding the solvent is supplied from the raw material supply tank 11. The boron-containing composition including the solvent may also be supplied from the raw material supply tank. In addition, the boron-containing sheet, electron donor, and, if necessary, hole scavenger and proton donor may be supplied separately or in any combination. For example, a tank for supplying the electron donor supported on the boron-containing sheet, a tank for supplying the hole scavenger, and a tank for supplying the proton donor may be provided. In this way, the system can be designed to supply the optimal material according to the usage conditions. 【0052】 The external stimulus control unit 20 is responsible for supplying external stimuli to the borohydride-containing sheet 31, on which electron donors dispersed in the solvent 32 within the hydrogen generation unit 10 are supported, at the desired timing. For example, when visible light is used as the external stimulus, the unit has a visible light irradiation function and a function to control the on / off state of visible light irradiation. In other words, it has a visible light source and a function to control the irradiation of this light source. Alternatively, the unit may use ambient light such as sunlight without a built-in light source. In this case, the external stimulus control unit 20 has a function to control the transmission and blocking of ambient light. 【0053】 The hydrogen generated in the hydrogen generation unit 10 is collected via the gas recovery passage 13. According to the hydrogen generation system 1 of the first embodiment, the amount of hydrogen can be easily adjusted by controlling the conditions of the external stimulus (intensity, time, etc.) and the conditions of the borohydride-containing composition (amount, concentration, shape, etc.). Therefore, it is possible to supply hydrogen by light irradiation without storing hydrogen gas in a storage tank in advance. Of course, this does not preclude the configuration of storing hydrogen in a hydrogen storage tank via the gas recovery passage 13. If such a hydrogen storage tank is provided, there is the advantage that the desired amount of hydrogen can be extracted instantaneously. 【0054】 To prevent a decrease in hydrogen release over time during the reaction, it is necessary to replace the composition 30 at appropriate intervals. The discharged composition 30 can be reused by recovering the boron-containing by-products through filtration or centrifugation, and the solvent can be guided back into the solvent supply channel 12. 【0055】 The hydrogen generation system according to the first embodiment can be modified in various ways. For example, the hydrogen generation unit 10 may not have a container for containing the composition 30 and a stirring unit 15, but instead may have a flow path (not shown), through which the composition 30 is flowed at a desired flow rate, and hydrogen may be generated by supplying an external stimulus to it. 【0056】 According to the hydrogen generation system of the first embodiment, a high-pressure tank is not required, and hydrogen can be easily generated at room temperature and atmospheric pressure. Moreover, since hydrogen generation can be controlled by light irradiation, on / off control of hydrogen generation can be performed instantaneously and easily compared to heating methods. Furthermore, the mass can be significantly reduced compared to hydrogen storage alloys. 【0057】 (Second Embodiment) Next, an example of a hydrogen generation system different from the first embodiment will be described. The hydrogen generation system according to the second embodiment differs from the first embodiment in that it uses a gas as a dispersion medium and does not contain a solvent in its composition. In the following figures, elemental members having the same function as described above will be denoted by the same reference numerals. Also, descriptions that overlap with the first embodiment will be omitted as appropriate. 【0058】 Figure 12 shows a schematic diagram of the hydrogen generation system according to the second embodiment. The hydrogen generation system 2 includes a hydrogen generation unit 10 and an external stimulus control unit 20. The hydrogen generation unit 10 is connected to a raw material supply tank 11, a gas recovery passage 13, a discharge passage 14, a gas supply passage 16, etc. The hydrogen generation unit 10 also has an airflow generating unit 17 for aerating and diffusing the composition in the gas. 【0059】 The hydrogen generation unit 10 is configured to receive a boron-containing composition 30 via a raw material supply tank 11 and nitrogen gas or an inert gas via a gas supply passage 16 at desired timings. The airflow generation unit 17 is responsible for circulating the boron-containing composition 30, which is dispersed in the gas dispersion medium, within the hydrogen generation unit 10. 【0060】 The external stimulus control unit 20 is responsible for supplying external stimuli to the borohydride-containing composition 30 dispersed in the airflow at a desired timing. The configuration can be the same as in the first embodiment. 【0061】 The hydrogen generated in the hydrogen generation unit 10 is collected via the gas recovery path 13. The system is configured to recover gas containing a large amount of hydrogen gas by upward displacement. According to the hydrogen generation system of the second embodiment, the amount of hydrogen generated at room temperature and atmospheric pressure can be adjusted by controlling the conditions of the external stimulus (intensity, time, etc.) and the conditions of the composition (amount, shape, type of electron donor, amount supported, etc.). 【0062】 To prevent a reduction in hydrogen emissions, residual gas is discharged from the discharge channel 14 at an appropriate time. The recovered residual can be separated into gas and residue by a filter and reused separately. 【0063】 The hydrogen generation system according to the second embodiment provides the same effects as the first embodiment. Furthermore, since it employs a gas-based system, it can be made even lighter than the first embodiment. 【0064】 (Third embodiment) The hydrogen generation system according to the third embodiment differs from the embodiments described above in that the hydrogen generation unit 10 is made of a thin container, and the light source, which is an external stimulus control unit, is a thin container built into the hydrogen generation unit 10. 【0065】 Figure 13 shows a schematic diagram illustrating the main components of the hydrogen generation system according to the third embodiment. The hydrogen generation unit 10 has a plurality of thin containers 18. An LED light source 21, which is an external stimulus control unit, is built into each of these thin containers 18. The hydrogen generation unit 10 is connected to a supply path (not shown) for supplying a dispersion medium (this composition) in which a borohydride-containing sheet on which an electron donor is supported is dispersed, a gas recovery path (not shown), a dispersion medium discharge path (not shown), and the like. The dispersion medium may be a liquid or a gas. 【0066】 The thin container 18 is configured to receive a dispersion medium containing a boron-containing sheet from a supply channel at a desired timing. Light from the LED light source 21 is irradiated onto the boron-containing composition 30 dispersed in the hydrogen generation unit 10 at the timing when hydrogen generation is desired. 【0067】 The hydrogen generated in the thin container 18 is collected via a gas recovery path. The hydrogen generation system according to the third embodiment provides the same effects as the first embodiment. Furthermore, by using multiple thin containers 18 in combination, hydrogen gas can be generated according to the needs. Depending on the application, it is also possible to provide only a gas recovery path and use it as a disposable or replaceable cartridge without supply or discharge paths. 【0068】 (Fourth Embodiment) The hydrogen generation system according to the fourth embodiment differs from the embodiments described above in that the composition is supported on a carrier. 【0069】 Figure 14 shows an example of a schematic explanatory diagram of the main parts of the hydrogen generation system according to the fourth embodiment. In the hydrogen generation system 4, a powdered boron-containing composition 30 is supported on beads 41 that are transparent to irradiated light. By using supported beads 40 on which the boron-containing composition 30 is supported on beads 41, the surface area of ​​the composition that is exposed to external stimuli can be increased, and the hydrogen release efficiency can be improved. 【0070】 The hydrogen generation unit 10 has a conveyor belt 19 that transports the supported beads 40 at a desired speed, and the supported beads 40 supplied to the conveyor belt 19 are irradiated with light at a desired timing using an external stimulus control unit 20. The hydrogen generated in the hydrogen generation unit 10 is collected via a gas recovery path 13. The light irradiation conditions, the transport speed of the conveyor belt 19, and the amount of supported beads 40 transported on the conveyor belt 19 are adjusted so that the amount of hydrogen released from the supported beads 40 is not reduced. 【0071】 The hydrogen generation system according to the fourth embodiment provides the same effects as the first embodiment. Furthermore, it enables miniaturization of the device. In addition, instead of beads, an adhesive sheet, a porous material, a film, etc., may be used as the carrier. 【0072】 (Fifth embodiment) The hydrogen generation system according to the fifth embodiment differs from the embodiments described above in that the powder of the composition is dispersed in a binder. 【0073】 Figure 15 shows a schematic diagram of a film used in the hydrogen generation system according to the fifth embodiment. The film 50 is made of a molded body in which powder of the boron-containing composition 30 is dispersed in a binder 51. The molded body may be formed on a support. Dispersing the boron-containing composition 30 in the binder 51 makes it easy to mold into a desired shape. The binder 51 is preferably a foamed resin or a porous material so as not to hinder hydrogen generation. Furthermore, in order to not reduce the hydrogen release efficiency, the binder is preferably made of a material that is highly transparent to light when the external stimulus is light. 【0074】 According to the hydrogen generation system of the fifth embodiment, the same effects as in the first embodiment can be obtained. Furthermore, it becomes possible to mold the composition to be mounted in the hydrogen generation unit into a desired shape. 【0075】 [Fuel cell system] The fuel cell system according to this embodiment is equipped with the hydrogen generation system described above as a hydrogen supply source in addition to a known fuel cell. According to the fuel cell according to this embodiment, hydrogen can be easily supplied to the fuel cell even at room temperature without using a high-pressure tank. [Examples] 【0076】 (Synthesis Example 1) Based on Non-Patent Document 1, (BH) n We synthesized a borohydride-containing sheet having a two-dimensional network consisting of (n≧4) elements. Specifically, 500 mg of magnesium diboride (Sigma-Aldrich) and 30 mL of cation exchange resin (Organo) were stirred in acetonitrile at room temperature for 3 days. This solution was filtered through a 0.2 μm pore size filter, and the filtrate was dried under reduced pressure at 80°C to obtain a yellow product. 【0077】 Figure 16 shows a transmission electron microscope image of the product obtained in Synthesis Example 1. As shown in the figure, it was confirmed to be a sheet-like material. Furthermore, the results of electron energy loss spectroscopy (EELS) of this product are shown in Figure 17, and two separate peaks were observed at 193 eV and 202 eV. The former is attributed to the transition from the 1s orbital to the π* orbital of boron, and the latter to the transition from the 1s orbital to the σ* orbital, indicating that boron is a network consisting of two-dimensional sp2 hybrid orbitals. Figure 18 shows the infrared spectroscopy spectrum (FT-IR) of the product. As shown in the figure, at 2500 cm⁻¹ -1 and 1400cm -1 BH vibrations and BHB vibrations were observed in each, confirming that the sheet contained hydrogen boride and had a two-dimensional network. 【0078】 (Example 1) A boron-containing composition according to Example 1 was obtained by dispersing 2.8 mg of the boron-containing sheet obtained in Synthesis Example 1 and 0.2 mg of the N3 dye (cis-bis(isothiocyanate)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)) represented by chemical formula (1) in 5 mL of acetonitrile. [ka] The UV-Vis spectra of the obtained compositions are shown in Figure 19. The UV-Vis spectra of Comparative Example 1, described later, are also shown in the same figure. As shown in the figure, the composition of Example 1 has absorption over a wide visible light range. 【0079】 (Example 2) 2.8 mg of the borohydride-containing sheet obtained in Synthesis Example 1 and 0.2 mg of N3 dye were mixed to obtain the powdered composition according to Example 2. 【0080】 (Example 3) A composition according to Example 3 was obtained by dispersing 2.8 mg of the borohydride-containing sheet obtained in Synthesis Example 1, 0.2 mg of N3 dye, and 2 mL of TEOA (triethanolamine) as a hole-catching agent in 3 mL of acetonitrile. 【0081】 (Example 4) A 0.05 mol / L acetonitrile dispersion of a borohydride-containing sheet and a 0.000065 mol / L acetonitrile dispersion of AuCl3 (manufactured by Fujifilm Corporation) were mixed. The UV-Vis spectrum after 1 hour of mixing is shown in Figure 20. As shown in the figure, the composition of Example 4 has absorption over a broad visible light range. 【0082】 (Example 5) The composition according to Example 4 was vacuum-dried to obtain the powdered composition according to Example 5. The amount of gold in the total composition according to Example 5 was 2.7% by mass. A TEM image of the obtained powder is shown in Figure 21. As shown in Figure 21, it can be seen that the gold is supported on a boron-containing sheet. 【0083】 (Examples 6-8) The compositions for Examples 6 to 8 were obtained in the same manner as in Examples 4 and 5, except that the amount of gold added to the total composition was changed to 5, 10, and 13% by mass, respectively. TEM images of the powdered compositions of Examples 6 to 8 are shown in Figures 22 to 24, respectively. It was confirmed that in all compositions, gold was supported on a boron-containing sheet. 【0084】 (Examples 9, 10) The composition of Example 1 was vacuum-dried to obtain the powdered Example 9. Furthermore, the composition synthesized by replacing the dye in Example 1 from N3 to 4-4'-bipyrudyl was vacuum-dried to obtain the powdered Example 10. 【0085】 (Comparative Example 1) A composition according to Comparative Example 1 was obtained by dispersing 2.8 mg of the boron-containing sheet obtained in Synthesis Example 1 in 5 mL of acetonitrile. 【0086】 (Comparative Example 2) A composition according to Comparative Example 2 was obtained by dispersing 0.2 mg of N3 dye in 5 mL of acetonitrile. 【0087】 (Reference example 1) The powder of the boron-containing sheet obtained in Synthesis Example 1 is referred to as Reference Example 1. 【0088】 (Comparative Example 3) Magnesium (Mg) powder, boron (B) powder, and graphite (C) powder were mixed so that the molar ratio of Mg:B:C was 1:2-2x:2x (where x is arbitrary). Under an inert atmosphere, the mixture was calcined at 900°C for 48 hours using the Powder-in-closed-tube method described in A. Yamamoto, et al. Supercond. Sci. Technol. 17, 921, 2004. to obtain a powder in which carbon was doped into the crystal lattice of MgB2. In Comparative Example 3, a value of x was 0.02, i.e., MgB2 powder with a carbon doping amount of 2% was synthesized. Next, 500 mg of MgB2 powder with a carbon dope content of 2% was mixed with 30 mL of cation exchange resin (organo) in acetonitrile, as in Synthesis Example 1, and stirred at room temperature for 3 days. This solution was filtered through a 0.2 μm pore size filter, and the filtrate was dried under reduced pressure at 80°C to obtain the product. 【0089】 (Comparative Example 4) In Comparative Example 3, the product of Comparative Example 4 was obtained using the same method as in Comparative Example 3, except that the value of x was changed to 0.04. 【0090】 (Rating 1) The amount of hydrogen released from the composition obtained in Example 1 was evaluated by the following method. Specifically, 5 mL of the composition obtained in Example 1 was placed in a closed quartz glass container 60, and a light source was set up so that visible light was irradiated onto the measurement sample 63 through a quartz glass plate, as shown in Figure 25. The quartz glass container 60 was kept under a nitrogen atmosphere, and the amount of hydrogen gas released was measured by analyzing the gas inside the container using microGC. The distance between the bottom surface of the measurement sample 63 and the visible light source was 2 cm. The measurement sample 63 was left to stand in a dark room for 2 hours, and then the amount of hydrogen released when irradiated with visible light was measured using a gas chromatograph GC-2010Plus (Shimadzu Corporation), not shown, equipped with a barrier discharge ionization detector. A super bright 500 XEF-501S (Tokina Corporation, 500W, 25.0A) was used as the visible light source, and light below 470 nm was cut off by a cut filter 61. Figure 26 shows the spectrum of the irradiated light. 【0091】 Figure 27 shows a plot of hydrogen release amounts against visible light irradiation time and without visible light irradiation for Example 1 and Comparative Examples 1 and 2. As shown in the figure, virtually no hydrogen was generated in any of the samples when not irradiated, and it was confirmed that the composition of Example 1 released significantly more hydrogen than Comparative Example 1 when irradiated with visible light. The internal quantum efficiency of Example 1 with respect to hydrogen release was 4.42%. The internal quantum efficiency was calculated by determining the number of absorbed photons from the absorption spectrum of the composition and the spectrum of the light source, and dividing this value by the number of electrons required for hydrogen production, which is a two-electron reaction. 【0092】 (Rating 2) For the composition of Example 1, the hydrogen production rate per hour of light irradiation was measured using the same method as in Evaluation 1, except that a monochromatic light source was used. For the monochromatic light source, the visible light source super bright 500 XEF-501S (Tokina, 500W, 25.0A) described in Evaluation 1 was used, and the sample was irradiated through various bandpass filters (wavelengths: 757, 650, 550, 450, 340 nm). Figure 28 shows the results (action spectra) and the UV-Vis absorption spectrum of the composition of Example 1 superimposed. As shown in the figure, the action spectrum and absorption spectrum matched, indicating that hydrogen production was induced by photoexcitation of the composition of Example 1. 【0093】 (Rating 3) For the composition of Example 1, the amount of hydrogen released was measured using the same method as in Evaluation 1, except that the distance between the light source and the sample was changed over time, and 3 mL of the composition obtained in Example 1 was used. The results are shown in Figure 29. As shown in the figure, it was confirmed that the amount of hydrogen released changed depending on the irradiation distance from the light source, i.e., the light intensity. 【0094】 (Rating 4) The amount of hydrogen released from the powdered composition of Example 2 was measured using the apparatus shown in Figure 25. The results are shown in Figure 30. As shown in the figure, it was confirmed that hydrogen is released even in powder form. 【0095】 (Rating 5) The hydrogen release amount of the composition of Example 3 was measured using the apparatus shown in Figure 25. 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 in contact with the sample and the xenon light source 62 (super bright 500 XEF-501S (manufactured by Tokina), 500 W, 25.0 A) was 2 cm. In addition, a cut filter 61 was used to cut out light below 470 nm. The results, as well as the results of Example 1 obtained in Evaluation 1, are shown in Figure 31. As shown in the figure, an increase in hydrogen release was confirmed by the addition of the hole trapper. 【0096】 (Rating 6) For the composition of Example 1, the amount of hydrogen released was measured in the same manner as in Evaluation 1, except that the following procedure was performed. Specifically, in this Evaluation 5, light irradiation was stopped 90 hours after visible light irradiation, and 1 mg of the dye N3 was added. Then, after 5 hours of non-irradiation, visible light irradiation was performed again for 45.5 hours, at which point light irradiation was stopped, and 1 mL of the proton donor formic acid was added. Then, after 7.5 hours of non-irradiation, visible light irradiation was performed again. The amount of hydrogen released at this time is shown in Figure 32. As shown in the figure, no increase in the amount of hydrogen released was observed with the addition of N3, while an increase in the amount of hydrogen released was observed with the addition of formic acid. The saturation of the amount of hydrogen released at around 100 hours of irradiation was not due to dye decomposition, but rather to the release of hydrogen from the boron-containing sheet, confirming that hydrogen can be continuously generated from the boron-containing sheet by adding a proton donor. 【0097】 (Rating 7) For the composition of Example 5, the amount of hydrogen released was measured using the same method as in Evaluation 1. The results are shown in Figure 33. From this figure, it was confirmed that the amount of hydrogen released increased significantly with visible light irradiation compared to the non-irradiated state. 【0098】 (Rating 8) Figure 34 shows the results of measuring the amount of hydrogen released by irradiating the powdered compositions of Examples 9 and 10 with visible light in nitrogen gas. Visible light irradiation was started at the timing indicated by the arrows in the figure. For comparison, the results of Reference Example 1 (a boron-containing sheet without an electron donor) are also shown in the same figure. As shown in the figure, it was confirmed that irradiating the powdered compositions with visible light significantly increased the amount of hydrogen released compared to the unirradiated state. 【0099】 (Rating 9) The band gap of the powdered products of Comparative Examples 3 and 4 was calculated using a Tauc-plot. The calculation results are shown in Figure 35. For comparison, the results for Reference Example 1 (a borohydride-containing sheet without electron donors) are also shown in the same figure. As shown in the figure, it was confirmed that when carbon is doped into the borohydride-containing sheet, the band gap energy increases compared to the borohydride-containing sheet without electron donors (C:0%). In other words, it was found that the light absorption band of the borohydride-containing sheet broadened, making it unable to absorb visible light. From this, it was found that simply doping a borohydride-containing sheet with a different element such as carbon does not cause absorption of visible light. 【0100】 This application claims priority based on Japanese Patent Application No. 2021-117864, filed on 16 July 2021, and incorporates all of its disclosures herein. [Explanation of Symbols] 【0101】 1-5 Hydrogen generation system 10 Hydrogen generation unit 11 Raw material supply tank 12 Solvent supply path 13 Gas recovery route 14 Exhaust channel 15. Stirring section 16 Gas supply lines 17 Airflow generation section 18 Thin containers 19. Conveyor belt 20 External Stimulus Control Unit 21 LED light source 30. Composition containing boric acid 31. Boric acid-containing sheet 32 Solvents 40 Supporting beads 41 beads 50 film 51 Binders

Claims

[Claim 1] (BH) ｎ The material contains a borohydride-containing sheet having a two-dimensional network consisting of (n≧4, where n is an integer) and an electron donor. The electron donor is an organic compound, At least a portion of the electron donor is supported on the surface of the borohydride-containing sheet. A borohydride-containing composition in which, upon external stimulation, electrons from the electron donor are supplied to the borohydride-containing sheet, and hydrogen is generated from the borohydride-containing sheet to which the electrons have been injected. [Claim 2] The borohydride-containing composition according to claim 1, characterized in that the LUMO (lowest unoccupied orbital) or conduction band level of the electron donor is less negative than the conduction band level of the borohydride-containing sheet. [Claim 3] The boron-containing composition according to claim 1, wherein the electron donor is excited by visible light, and hydrogen is generated from the boron-containing sheet by supplying the excited electrons to the boron-containing sheet. [Claim 4] The borohydride-containing composition according to claim 1, characterized in that the electron donor has at least one of a carboxyl group, a phosphono group, and a sulfonic acid group. [Claim 5] The hydrogen boride-containing composition according to claim 1, characterized by containing a solvent. [Claim 6] Furthermore, the borohydride-containing composition according to claim 1 further contains a hole-trapping agent. [Claim 7] The hydrogen boride-containing composition according to claim 6, characterized in that the oxidation-reduction potential of the hole trapper is lower than the HOMO (highest occupied orbital) or valence band level of the electron donor. [Claim 8] Furthermore, the hydrogen boride-containing composition according to claim 1 is characterized by containing a proton donor. [Claim 9] The borohydride-containing composition according to claim 8, characterized in that the proton donor is an acid. [Claim 10] A hydrogen generation system comprising a borohydride-containing composition according to any one of claims 1 to 9, A composition containing hydrogen boride, A control unit that controls the on / off switching of external stimuli to the borohydride-containing composition, A hydrogen generation system equipped with a hydrogen generation unit that extracts hydrogen to the outside. [Claim 11] A fuel cell system comprising a hydrogen generation system according to claim 10, and a fuel cell supplied with hydrogen from the hydrogen generation system.

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