Hydrogen generating composition, hydrogen generating system, and fuel cell system

Abstract

To provide a hydrogen generating composition capable of generating hydrogen by an external stimulus, and a hydrogen generating system and a fuel cell system equipped with the hydrogen generating composition.SOLUTION: A hydrogen generating composition comprising a nitrogen-containing aromatic compound which has accepted one proton and one electron. A hydrogen boride-containing sheet having a two-dimension network composed of (BH) n (n ≥ 4, where n is an integer) as the material that donates protons and electrons.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydrogen generating composition, a hydrogen generating system, and a fuel cell system. [Background technology]

[0002] Hydrogen is attracting attention as a clean energy source because the only substance emitted by combustion or reaction is water. High-pressure cylinders have traditionally been used as hydrogen supply sources. However, because hydrogen is an explosive gas, there has been vigorous research into the development of safer hydrogen supply systems.

[0003] Compositions aimed at improving the performance of the hydrogen supply source include (BH) n (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, and in response to an external stimulus, electrons from the electron donor are supplied to the borohydride-containing sheet, causing hydrogen to be generated from the borohydride-containing sheet into which the electrons have been injected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 286830 [Non-patent literature]

[0005] [Non-Patent Document 1] Kondo T., Miyauchi M. et al., Photoinduced hydrogen release from hydrogen bor ide sheets, Nature Communications, 10, 4880 (2019). Summary of the Invention [Problem to be solved by the invention]

[0006] However, the borohydride-containing composition of Patent Document 1 has the problem that self-oxidation of the electron donor inhibits continuous hydrogen production, and the problem of high costs due to the use of expensive ruthenium dyes and noble metal particles (platinum, etc.) to sensitize light.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a hydrogen generating composition that can generate hydrogen when irradiated with visible light, as well as a hydrogen generating system and a fuel cell system that include the hydrogen generating composition. [Means for solving the problem]

[0008] The present inventors have conducted extensive research and have found that the problems of the present invention can be solved in the following manner, thereby completing the present invention. [1] A hydrogen generating composition comprising a nitrogen-containing aromatic compound that has accepted one proton and one electron. [2] The hydrogen generating composition according to [1], wherein the nitrogen-containing aromatic compound absorbs light having a wavelength of 500 nm or more. [3] The hydrogen generating composition according to [1], wherein the nitrogen-containing aromatic compound is phenanthroline or a derivative thereof. [4] As the substance that donates the protons and the electrons, (BH) n (n≧4, where n is an integer) [5] The hydrogen generating composition according to [4], which contains a nitrogen-containing aromatic compound that has accepted electrons and protons from the borohydride-containing sheet, and generates hydrogen when irradiated with visible light. [6] The hydrogen generating composition according to [1], which contains a solvent. [7] The hydrogen generating composition according to any one of [1] to [6], a control unit that controls irradiation of the hydrogen generating composition with visible light; A hydrogen generation system comprising: a hydrogen generation unit that extracts hydrogen to the outside. [8][7] and the hydrogen generation system described in a fuel cell to which hydrogen is supplied from the hydrogen generation system. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a hydrogen generating composition capable of generating hydrogen when irradiated with visible light, as well as a hydrogen generating system and a fuel cell system that include the hydrogen generating composition. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the local structure of a two-dimensional network consisting of (BH)n (n≧4) of a borohydride-containing sheet. [Figure 2] FIG. 1 is a schematic diagram showing the local structure of a two-dimensional network consisting of (BH)n (n≧4) of a borohydride-containing sheet. [Figure 3] FIG. 1 is a schematic diagram showing the local structure of a two-dimensional network consisting of (BH)n (n≧4) of a borohydride-containing sheet. [Figure 4] 1 is a diagram illustrating a method for generating hydrogen using a hydrogen generating composition according to one embodiment of the present invention. [Figure 5] 1 is a diagram illustrating a hydrogen generation system according to an embodiment of the present invention. [Figure 6] 1 is a diagram illustrating a hydrogen generation system according to an embodiment of the present invention. [Figure 7] 1 is a diagram illustrating a hydrogen generation system according to an embodiment of the present invention. [Figure 8] 1 is a diagram illustrating a hydrogen generation system according to an embodiment of the present invention. [Figure 9] 1 is a diagram illustrating a hydrogen generation system according to an embodiment of the present invention. [Figure 10] 1 is a transmission electron microscope image of the product obtained in Synthesis Example 1. [Figure 11]FIG. 2 is a graph showing the results of measurement of the bond energy of the product obtained in Synthesis Example 1, measured by X-ray photoelectron spectroscopy. [Figure 12] FIG. 1 is a diagram showing the results of measuring the infrared spectrum of the product obtained in Synthesis Example 1. [Figure 13] FIG. 1 shows the results of linear sweep voltammetry measurements of 1,10-phenanthroline (Phen), a mixture of 1,10-phenanthroline and hydrochloric acid (Phen+acid), and a solution containing no 1,10-phenanthroline or acid (blank) in Example 1. [Figure 14] FIG. 1 shows the results of ultraviolet-visible spectrophotometric analysis of a composition containing 1,10-phenanthroline (Phen) and a boron hydride-containing sheet in Example 2, with a PhenPhen content of 30 μmol, and 1,10-phenanthroline that underwent LSV measurement in the presence of hydrochloric acid. [Figure 15] FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from 1,10-phenanthroline that has been subjected to LSV measurement in the presence of hydrochloric acid in Example 3. [Figure 16] FIG. 10 is a diagram showing the results of measuring the infrared spectra of 1,10-phenanthroline, a borohydride-containing sheet, and a composition containing 1,10-phenanthroline and a borohydride-containing sheet in Example 4. [Figure 17] FIG. 10 is a diagram showing the results of measuring the ultraviolet-visible absorption spectra of 1,10-phenanthroline, a boron-containing sheet, and a composition containing 1,10-phenanthroline and a boron-containing sheet in Example 5. [Figure 18] FIG. 10 is a diagram showing the results of calculating the absorption spectrum of 1,10-phenanthroline by density functional theory in Example 6. [Figure 19] FIG. 2 is a diagram schematically illustrating an evaluation device for hydrogen release characteristics. [Figure 20] FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from sample solution A in Example 7. [Figure 21]FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from sample solution A in Example 8. [Figure 22] FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from sample solution A in Example 9. [Figure 23] FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from sample solution A in Example 10. [Figure 24] FIG. 10 is a graph showing the results of measuring the ultraviolet-visible absorption spectra of compositions α and β in Comparative Example 21. [Figure 25] FIG. 10 is a graph showing the results of measuring the amount of hydrogen generated from composition α in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of an embodiment to which the present invention is applied will be described below. Note that 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 size and proportions of each component in the following drawings are for the convenience of explanation and are not intended to be limiting.

[0012] [Hydrogen generating composition] (First embodiment) A hydrogen generating composition according to one embodiment of the present invention is a composition containing a nitrogen-containing aromatic compound that has accepted one proton and one electron.

[0013] "Nitrogen-containing aromatic compounds" The nitrogen-containing aromatic compound is not particularly limited as long as it can accept one proton and one electron, but it is preferable that the compound absorbs light having a wavelength of 500 nm or more.

[0014] Examples of the nitrogen-containing aromatic compound include 2,2'-bipyridine and its derivatives represented by the following chemical formula (1) (here, the derivatives of 2,2'-bipyridine are those in which the hydrogen atoms at the 4,4'-positions are substituted with a halogen element, an alkyl group having 1 to 3 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, or a hydroxy group), 3,3'-bipyridine and its derivatives represented by the following chemical formula (2) (here, the derivatives of 3,3'-bipyridine are, for example, 4,4' 4,4'-bipyridine and its derivatives represented by the following chemical formula (3) (here, the derivatives of 4,4'-bipyridine are those in which the hydrogen atoms at the 3,3', 2,3', 2,2', etc. positions are substituted with a halogen element, an alkyl group having 1 to 3 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group or a hydroxy group). and hydroxy groups.), 2,3'-bipyridine and derivatives thereof represented by the following chemical formula (4) (here, the 2,3'-bipyridine derivatives are those in which the hydrogens at the 4,4'-positions are substituted with halogen elements, alkyl groups having 1 to 3 carbon atoms which may have a substituent, phenyl groups which may have a substituent, carboxy groups, and hydroxy groups.), 2,4'-bipyridine and derivatives thereof represented by the following chemical formula (5) (here, the 2,4'-bipyridine derivatives are those in which the hydrogens at the 3,3'-positions are substituted with halogen elements, alkyl groups having 1 to 3 carbon atoms which may have a substituent, phenyl groups which may have a substituent, carboxy groups, and hydroxy groups.), 3,4'-bipyridine and derivatives thereof represented by the following chemical formula (6) (here, the 3,4'-bipyridine derivatives are those in which the hydrogens at the 2,2'-positions are substituted with halogen elements, alkyl groups having 1 to 3 carbon atoms which may have a substituent, phenyl groups which may have a substituent, carboxy groups, and hydroxy groups.), 1,10-phenanthroline represented by the following chemical formula (7) and its derivatives (here, 1,10-phenanthroline derivatives are those in which hydrogen atoms at the 5th, 4th, 7th, etc. positions are substituted with a halogen atom, an alkyl group having 1 to 3 carbon atoms which may have a substituent, a phenyl group which may have a substituent, a carboxy group, or a hydroxy group). Examples of 1,10-phenanthroline derivatives include 5-chloro-1,10-phenanthroline represented by the following chemical formula (8), 4,7-dichloro-1,10-phenanthroline represented by the following chemical formula (9), and 4,7-dimethyl-1,10-phenanthroline represented by the following chemical formula (10).

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[0025] These nitrogen-containing aromatic compounds generate hydrogen when irradiated with visible light after accepting one proton and one electron. Examples of methods that can be used to donate one proton and one electron to a nitrogen-containing aromatic compound include electrochemical methods in the coexistence of an acid and methods in the coexistence of an acid and a chemical reducing agent.

[0026] In the electrochemical method, a nitrogen-containing aromatic compound and an acid are added to an electrolyte, a working electrode, a counter electrode, and a reference electrode are inserted into the electrolyte, and a negative potential is applied to the working electrode using a device such as a potentiostat, thereby donating one proton and one electron to the nitrogen-containing aromatic compound.

[0027] When the nitrogen-containing aromatic compound is present together with an acid, examples of the acid that can be used include hydrochloric acid, nitric acid, and carboxylic acids such as formic acid and acetic acid. When protons are supplied to a nitrogen-containing aromatic compound by an acid, the amount of acid added per mole of nitrogen-containing aromatic compound is preferably 0.1 mol or more, more preferably 1.0 mol to 10 mol. If the amount of acid added is less than 0.1 mol, the amount of protons supplied is small, resulting in reduced visible light absorption. If the amount of acid added is more than 10 mol, a salt is generated, causing precipitation.

[0028] Here, the wavelength of the visible light is preferably 450 nm to 750 nm, more preferably 470 nm to 720 nm, and even more preferably 500 nm to 700 nm. When the wavelength of the visible light is equal to or greater than the lower limit, hydrogen can be efficiently produced. When the wavelength of the visible light is equal to or less than the upper limit, the nitrogen-containing aromatic compound that has accepted one proton and one electron cannot absorb light and cannot produce hydrogen.

[0029] Taking 1,10-phenanthroline as an example of a nitrogen-containing aromatic compound, the state in which 1,10-phenanthroline has accepted one proton and one electron is represented by the following chemical formula (11): As a source of electrons to 1,10-phenanthroline, for example, chemical reducing agents such as oxalic acid, sodium phosphinate, iron (II) ions, lithium aluminum hydride (LiAlH4), sodium amalgam, sodium borohydride (NaBH4), tin (II) ions, sulfite, hydrazine, zinc amalgam (Zn(Hg)), and diisobutylaluminum hydride (DIBAH) can be used. As a proton donor, for example, hydrochloric acid, nitric acid, and carboxylic acids such as formic acid and acetic acid are used.

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[0031] When visible light is irradiated onto 1,10-phenanthroline in the state represented by the above chemical formula (11), one more electron is accepted by the 1,10-phenanthroline, as represented by the following chemical formula (12).

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[0033] When one more proton is donated to 1,10-phenanthroline in the state represented by the above chemical formula (12), one more proton is accepted by 1,10-phenanthroline, as represented by the following chemical formula (13). Examples of the proton donor include the aforementioned hydrochloric acid, nitric acid, and carboxylic acids such as formic acid and acetic acid.

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[0035] When 1,10-phenanthroline is in the state represented by the above chemical formula (13), the two hydrogen atoms (H) at the 7-position become hydrogen molecules (H2) and are released. This causes hydrogen to be generated from 1,10-phenanthroline. As described above, when the hydrogen generating composition of this embodiment contains only a nitrogen-containing aromatic compound that has accepted one proton and one electron, it can generate hydrogen as described above when irradiated with visible light.

[0036] "Boron hydride-containing sheet" The hydrogen generating composition of the present embodiment preferably contains a borohydride-containing sheet as a substance that donates protons and electrons to the nitrogen-containing aromatic compound.

[0037] The borohydride-containing sheet is (BH) n (n≧4, where n is an integer) (BH) n The two-dimensional network consisting of (n≧4) is formed by a molar ratio of boron atoms (B) and hydrogen atoms (H) of 1:1 (see Non-Patent Document 1).

[0038] The borohydride-containing sheet is (BH) n It is sufficient to have a two-dimensional network consisting of (n≧4), (BH) n Compounds with a two-dimensional network structure (n≧4) as the main skeleton (e.g., (BH) n(compounds in which a dopant is introduced into a part of a two-dimensional network consisting of (n≧4), compounds in which the ends are blocked 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 boron-containing sheets in the compound is 80% or more.

[0039] Examples of dopants include 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; metal elements such as titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, cadmium, indium, tin, yttrium, niobium, molybdenum, tungsten, tantalum, and lead; and noble metal elements such as ruthenium, rhodium, palladium, silver, gold, iridium, and platinum.

[0040] Figures 1 to 3 show (BH) n The figure shows a schematic diagram of the local structure of a two-dimensional network consisting of n≧4. As shown in FIG. 1, in the two-dimensional network, boron atoms are arranged in a hexagonal honeycomb pattern (a mesh formed by interconnected hexagons formed by the boron atoms), and two adjacent boron atoms have sites where they bond to the same hydrogen atom. The boron atoms form a honeycomb-like (honeycomb) sheet-like hexagonal lattice groove structure, and one hydrogen atom is bonded to two adjacent boron atoms in the hexagonal lattice structure above and below the sheet in a bridge-like manner, as shown in FIGS. 2 and 3. Furthermore, two hydrogen atoms are arranged facing each other above and below the sheet-like hexagonal lattice structure. Note that the arrangement of hydrogen atoms in borohydride does not need to have long-range order. Furthermore, the bonds between atoms may be tilted in the Z direction in FIGS. 2 and 3, or the sheet itself may be curved. Also, not all hydrogen atoms necessarily need to be bonded to the bridge.

[0041] The boron-containing sheet is a thin film material and may be composed of a single layer or multiple layers. In the boron-containing sheet of this embodiment, the total number of boron atoms (B) and hydrogen atoms (H) forming the mesh-like surface structure is 1,000 or more.

[0042] The bond distance d1 (see FIG. 1) between two adjacent boron atoms (B) is, for example, 0.155 nm to 0.190 nm. When viewed from the Z direction, the bond distance d2 (see FIG. 2) between two adjacent boron atoms (B) separated by one hydrogen atom (H) is, for example, 0.155 nm to 0.190 nm. The bond distance d3 (see FIG. 2) between adjacent boron atoms (B) and hydrogen atoms (H) is, for example, 0.12 nm to 0.15 nm.

[0043] The thickness of the boron-containing sheet is, for example, 0.2 nm to 10 nm. The length of the boron-containing sheet in at least one direction (for example, the length in the X or Y direction in FIG. 1) is preferably 100 nm or more. By making the length in at least one direction 100 nm or more, the boron-containing sheet can be more effectively used as an electronic material, a catalyst support material, a catalyst material, a superconducting material, etc. The size (area) of the boron-containing sheet is not particularly limited, and it can be formed to any size.

[0044] The boron-containing sheet is a substance with a crystalline structure. Furthermore, the boron-containing sheet has strong bonding forces between the boron atoms (B) that form the hexagonal rings, and between the boron atoms (B) and the hydrogen atoms (H). Therefore, even if the boron-containing sheet forms a crystal (aggregate) consisting of multiple layers during production, it can be easily cleaved along the crystal planes, just like graphite, and separated (recovered) as a single two-dimensional sheet.

[0045] The boron hydride-containing sheet is significantly lighter than hydrogen storage alloys. Furthermore, the boron hydride-containing sheet can be used at normal pressure, making it safe. However, this does not preclude its use under conditions other than normal pressure.

[0046] The method for producing the boron-containing sheet is not particularly limited. For example, it can be produced by the following method. Specifically, first, a metal diboride having an MB2 structure and an ion-exchange resin in which the metal ions constituting the metal diboride and ion-exchangeable ions are 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. This mixing process can be carried out in an inert atmosphere consisting of an inert gas such as nitrogen (N2) or argon (Ar).

[0047] As the metal diboride having the MB2 structure, one having a hexagonal ring structure is used. Examples of the metal diboride having the MB2 structure include aluminum diboride (AIB2), magnesium diboride (MgB2), tantalum diboride (TaB2), zirconium diboride (ZrB2), rhenium diboride (ReB2), chromium diboride (CrB2), titanium diboride (TiB2), and vanadium diboride (VB2). Magnesium diboride is preferably used because it can be easily ion-exchanged with an ion-exchange resin in a polar organic solvent.

[0048] The ion exchange resin in which ion-exchangeable ions are coordinated with the metal ions constituting the metal diboride is not particularly limited. Examples of such ion exchange resins include styrene polymers having a functional group (hereinafter referred to as "functional group a") in which ion-exchangeable ions are coordinated with the metal ions constituting the metal diboride, divinylbenzene polymers having functional group a, and copolymers of styrene having functional group a and divinylbenzene having functional group a. Examples of functional groups include sulfo groups and carboxy groups. Among these, sulfo groups are preferred because they can easily be ion-exchanged with the metal ions constituting the metal diboride in a polar organic solvent.

[0049] An acid may be further added in the mixing step. Examples of the acid 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 shortened.

[0050] The polar organic solvent is not particularly limited, and examples thereof include acetonitrile, N,N-dimethylformamide, and methanol.

[0051] When an acid is used in the mixing step, the acid is removed as necessary. The method for removing the acid is not particularly limited, but examples thereof include heating, drying under reduced pressure, and precipitation recovery.

[0052] The mixed solution is then filtered. Examples of the filtration method include natural filtration, vacuum filtration, pressure filtration, and centrifugal filtration. The solution containing the product recovered by filtration and separated from the precipitate is dried naturally, or dried under reduced pressure, by heating, or the like, to finally obtain the product, a boron-containing sheet having a two-dimensional network.

[0053] The borohydride-containing sheet has protons and electrons and functions as a donor that supplies protons and electrons to the nitrogen-containing aromatic compound.

[0054] "solvent" The hydrogen generating composition of this embodiment can be used in powder form without using a solvent, or the nitrogen-containing aromatic compound, or the nitrogen-containing aromatic compound and the borohydride-containing sheet, may be dissolved or dispersed in a solvent. The solvent can be water or an organic solvent. The organic solvent is not particularly limited as long as it can dissolve or disperse the nitrogen-containing aromatic compound and the borohydride-containing sheet. Examples of the organic solvent include high-purity ethanol, high-purity methanol, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N,N-dimethylformamide, propylene carbonate, acetonitrile, ethyl acetate, tetrahydrofuran, pyridine, hexane, toluene, and xylene. When the nitrogen-containing aromatic compound, or the nitrogen-containing aromatic compound and the borohydride-containing sheet, are dissolved or dispersed in these solvents, the resulting solution or dispersion exhibits a color (discoloration) in the visible light range.

[0055] "Other additives" The hydrogen generating composition of the present embodiment may contain a high molecular weight compound or a low molecular weight compound such as a binder resin, a dispersant, etc., within the scope of the present invention. Furthermore, the hydrogen generating composition of the present embodiment may contain additives such as an antistatic agent, a thermally conductive filler, a flame retardant, etc., as appropriate.

[0056] "Hydrogen-generating composition" The hydrogen generating composition of this embodiment can be used as a powder. Alternatively, a solvent may be added to use the composition as a solution, dispersion, or slurry. Alternatively, the hydrogen generating composition of this embodiment may be dispersed in a resin to form a film or a molded body of any shape. The film or molded body may also be porous. When the hydrogen generating composition of this embodiment is used as a film or molded body, it is preferable that the powder particles are in contact with each other (connected) in the film or molded body. The presence of the powder particles in contact with each other improves the hydrogen generation efficiency.

[0057] The method for producing the hydrogen generating composition is not particularly limited. The hydrogen generating composition can be obtained by mixing raw materials for the hydrogen generating composition, such as a solvent, a nitrogen-containing aromatic compound, and a boron-containing sheet, in any order. The intermediate composition may be prepared in advance, or the components of the intermediate composition may be added at the time of use.

[0058] "Sustainable Hydrogen Generation System" The hydrogen generating composition of this embodiment is a mixture containing a nitrogen-containing aromatic compound and a borohydride-containing sheet, and hydrogen can be generated continuously by irradiating the mixture with visible light.

[0059] 4 is a diagram showing a method for generating hydrogen using the hydrogen generating composition of this embodiment, in which 1,10-phenanthroline is used as an example of the nitrogen-containing aromatic compound. As shown in Figure 4, when 1,10-phenanthroline and a borohydride-containing sheet coexist, one proton is donated from the borohydride-containing sheet to 1,10-phenanthroline (state A). Furthermore, one electron is donated from the borohydride-containing sheet to 1,10-phenanthroline (state B). When 1,10-phenanthroline in state B is excited by irradiation with visible light, one more electron is generated in 1,10-phenanthroline (state C). The 1,10-phenanthroline in state C receives one more proton from the borohydride-containing sheet (state D). When 1,10-phenanthroline reaches state D, one hydrogen atom (H) at the 7-position acts as a hydride anion and reacts with a proton of the borohydride-containing sheet, resulting in hydrogen gas being released from the 1,10-phenanthroline. When hydrogen is generated from 1,10-phenanthroline, 1,10-phenanthroline returns to state A. Therefore, the above cycle can be repeated again, allowing hydrogen to be continuously generated.

[0060] (Second embodiment) A hydrogen generating composition according to one embodiment of the present invention is a composition containing a nitrogen-containing aromatic compound described below.

[0061] "Nitrogen-containing aromatic compounds" Examples of the nitrogen-containing aromatic compound include 5,6-dimethyl-1,10-phenanthroline represented by the following chemical formula (14), bathophenanthroline represented by the following chemical formula (15), and neocuproine represented by the following chemical formula (16).

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[0065] The hydrogen generating composition of the present embodiment can generate hydrogen immediately by mixing the nitrogen-containing aromatic compound with the borohydride-containing sheet, without irradiation with visible light.

[0066] [Hydrogen generation system] A hydrogen generation system according to one embodiment of the present invention utilizes the hydrogen generation composition described above, and includes the hydrogen generation composition, a control unit that controls the irradiation of visible light onto the hydrogen generation composition, and a hydrogen generation unit that extracts hydrogen to the outside. The hydrogen generation system of this embodiment can be applied to a wide range of applications where hydrogen needs to be generated by irradiation of visible light. An example of a specific embodiment of the hydrogen generation system will be described below. Each embodiment can be suitably combined.

[0067] (First embodiment) FIG. 5 is a diagram schematically illustrating the hydrogen generation system of the first embodiment. 5, hydrogen generation system 1 of this embodiment includes hydrogen generation unit 10 and visible light control unit 20. Hydrogen generation unit 10 is connected to raw material supply tank 11, solvent supply channel 12, gas recovery channel 13, and discharge channel 14. Hydrogen generation system 1 of this embodiment includes a container for storing borohydride-containing composition 30 and a stirring unit 15 for stirring the container.

[0068] In this embodiment, the hydrogen generating composition other than the solvent is supplied from the raw material supply tank 11. The hydrogen generating composition including the solvent may be supplied from the raw material supply tank. Alternatively, the borohydride-containing sheet and the nitrogen-containing aromatic compound may be supplied separately or in any combination. In this way, the system can be designed to supply optimal materials depending on the usage situation.

[0069] The visible light control unit 20 serves to irradiate the borohydride-containing sheet 31 and the nitrogen-containing aromatic compound dispersed in the solvent 32 in the hydrogen generation unit 10 with visible light at the desired timing. The visible light control unit 20 has, for example, a visible light irradiation function and a function to control the on / off of the visible light irradiation. In other words, it has a visible light source and a function to control the irradiation of this light source. It is also possible to use external light such as sunlight instead of a built-in light source. In this case, the visible light control unit 20 has a function to control the transmission and blocking of external light.

[0070] The hydrogen generated in the hydrogen generation unit 10 is collected via the gas recovery path 13. According to the hydrogen generation system 1 of this embodiment, the amount of hydrogen can be easily adjusted by controlling the conditions of the visible light (intensity, time, etc.) and the conditions of the hydrogen generating composition (amount, concentration, shape, etc.). This makes it possible to supply hydrogen by irradiating it with visible light without storing hydrogen gas in a storage tank in advance. Of course, this does not exclude a configuration in which hydrogen is stored in a hydrogen storage tank via the gas recovery path 13. Providing such a hydrogen storage tank has the advantage of allowing the desired amount of hydrogen to be extracted instantaneously.

[0071] To prevent the amount of hydrogen released from decreasing over time as the reaction proceeds, it is necessary to replace the hydrogen generating composition 30 at an appropriate timing. The discharged hydrogen generating composition 30 can be filtered or centrifuged to recover the boron-containing by-product, and the solvent can be reused by being guided back to the solvent supply line 12.

[0072] The hydrogen generation system 1 of this embodiment can be modified in various ways. For example, the hydrogen generation unit 10 may be configured not to be provided with a container for storing the hydrogen generating composition 30 and the stirring unit 15, but to have a flow path (not shown), to flow the hydrogen generating composition 30 through this flow path at a desired flow rate, and to supply an external stimulus to the hydrogen generating composition 30.

[0073] The hydrogen generation system 1 of this embodiment does not require a high-pressure tank and can easily generate hydrogen at room temperature and pressure. Moreover, because hydrogen generation can be controlled by light irradiation, on / off control of hydrogen generation can be performed instantaneously and easily compared to heating methods. In addition, the mass can be significantly reduced compared to hydrogen storage alloys.

[0074] (Second embodiment) An example of a hydrogen generation system different from the first embodiment will be described. The hydrogen generation system of the second embodiment differs from the first embodiment in that a gas is used as the dispersion medium and that the composition does not contain a solvent. In the following sections, elements having the same functions as those described above will be given the same reference numerals. Also, descriptions that overlap with the first embodiment will be omitted as appropriate.

[0075] FIG. 6 is a diagram schematically illustrating a hydrogen generation system according to the second embodiment. 6, the hydrogen generation system 2 of this embodiment includes a hydrogen generation unit 10 and a visible light control unit 20. The hydrogen generation unit 10 is connected to a raw material supply tank 11, a gas recovery channel 13, an exhaust channel 14, a gas supply channel 16, etc. The hydrogen generation unit 10 also includes an airflow generation unit 17 for suspending and diffusing the hydrogen generating composition in the gas.

[0076] The hydrogen generating unit 10 is configured so that the hydrogen generating composition 30 is supplied at a desired timing via a raw material supply tank 11, and nitrogen gas or an inert gas is supplied via a gas supply path 16. The airflow generating unit 17 plays a role in making the hydrogen generating composition 30 dispersed in the gas serving as a dispersion medium float within the hydrogen generating unit 10.

[0077] The visible light control unit 20 serves to irradiate the hydrogen generating composition 30 dispersed in the airflow with visible light at a desired timing. The visible light control unit 20 may have the same configuration as in the first embodiment.

[0078] The hydrogen generated in the hydrogen generation unit 10 is collected via the gas recovery line 13. The system is configured to recover a gas containing a large amount of hydrogen gas by hydrogen substitution. According to the hydrogen generation system 2 of this embodiment, the amount of hydrogen generated at room temperature and pressure can be adjusted by controlling the conditions of visible light (intensity, time, etc.) and the conditions of the hydrogen generating composition (amount, concentration, shape, etc.).

[0079] To prevent a decrease in the amount of hydrogen released, the residue-containing gas is discharged at an appropriate time from the discharge path 14. The collected residue can be separated into gas and residue using a filter, and each can be reused.

[0080] The hydrogen generation system 2 of this embodiment does not require a high-pressure tank and can easily generate hydrogen at room temperature and pressure. Moreover, because hydrogen generation can be controlled by light irradiation, on / off control of hydrogen generation can be performed instantaneously and easily compared to heating methods. In addition, the mass can be significantly reduced compared to hydrogen storage alloys. Furthermore, because a gas-based system is used, even lighter weight can be achieved than in the first embodiment.

[0081] (Third embodiment) The hydrogen generation system of the third embodiment differs from the above-described embodiments in that the hydrogen generation unit 10 is made of a thin container and a light source, which is a visible light control unit, is built into the hydrogen generation unit 10.

[0082] FIG. 7 is a diagram schematically illustrating a hydrogen generation system according to the third embodiment. As shown in FIG. 7, in the hydrogen generation system of this embodiment, a hydrogen generation unit 10 has a plurality of thin containers 18. An LED light source 21, which is a visible light control unit, is built into each thin container 18. A supply path (not shown) for supplying a dispersion medium (hydrogen generating composition) in which a borohydride-containing sheet and a nitrogen-containing aromatic compound are dispersed, a gas recovery path (not shown), a dispersion medium discharge path (not shown), and the like are connected to the hydrogen generation unit 10. The dispersion medium may be either a liquid or a gas.

[0083] The thin container 18 is configured so that a dispersion medium in which the borohydride-containing sheet and the nitrogen-containing aromatic compound are dispersed is supplied from a supply channel at a desired timing to the thin container 18. The hydrogen generating composition 30 dispersed in the hydrogen generating unit 10 is irradiated with light from the LED light source 21 at a timing when hydrogen is to be generated.

[0084] The hydrogen generated in the thin container 18 is captured via a gas recovery path. The hydrogen generation system of this embodiment provides the same effects as the first embodiment. Furthermore, by using multiple thin containers 18 in combination, it is possible to generate hydrogen gas according to needs. Depending on the application, it may be possible to provide only a gas recovery path, without providing a supply path or a discharge path, and use the system as a disposable or replaceable cartridge.

[0085] (Fourth embodiment) The hydrogen generation system of the fourth embodiment differs from the above-described embodiments in that the hydrogen generation composition is supported on a support.

[0086] FIG. 8 is a diagram schematically showing the main components of a hydrogen generation system according to the fourth embodiment. 8, in the hydrogen generation system 4 of this embodiment, a powdered hydrogen generating composition 30 is supported on beads 41 that are transparent to the irradiated light. By using support beads 40 in which the hydrogen generating composition 30 is supported on beads 41, the area of ​​the hydrogen generating composition that receives visible light can be increased, thereby improving the hydrogen release efficiency.

[0087] The hydrogen generation unit 10 has a conveyor belt 19 that transports the support beads 40 at a desired speed. In the hydrogen generation unit 10, the support beads 40 supplied to the conveyor belt 19 are irradiated with visible light at a desired timing using a visible light control unit 20. The hydrogen generated in the hydrogen generation unit 10 is then collected via a gas recovery path 13. The light irradiation conditions, the transport speed of the conveyor belt 19, and the transport amount of the support beads 40 on the conveyor belt 19 are adjusted so as not to reduce the amount of hydrogen released.

[0088] The hydrogen generation system 4 of this embodiment does not require a high-pressure tank and can easily generate hydrogen at room temperature and pressure. Moreover, because hydrogen generation can be controlled by light irradiation, on / off control of hydrogen generation can be performed instantaneously and easily compared to heating methods. In addition, the mass can be significantly reduced compared to hydrogen storage alloys. Furthermore, the hydrogen generation system 4 of this embodiment can achieve a more compact device. Note that instead of beads, adhesive sheets, porous bodies, films, etc. may be used as the support.

[0089] (Fifth embodiment) The hydrogen generating system of the fifth embodiment differs from the above-described embodiments in that the hydrogen generating composition powder is dispersed in a binder.

[0090] FIG. 9 is a diagram schematically showing a film used in the hydrogen generation system of the fifth embodiment. As shown in FIG. 9, the film 50 is made of a molded body in which powder of the hydrogen generating composition 30 is dispersed in a binder 51. This molded body may be formed on a support. Dispersing the hydrogen generating composition 30 in the binder 51 makes it easy to mold it into a desired shape. The binder 51 is preferably a foamable resin or a porous body so as not to interfere with hydrogen generation. In addition, the binder is preferably made of a material that is highly transparent to visible light so as not to reduce hydrogen release efficiency.

[0091] The hydrogen generation system of this embodiment does not require a high-pressure tank and can easily generate hydrogen at room temperature and pressure. Moreover, because hydrogen generation can be controlled by light irradiation, on / off control of hydrogen generation can be performed instantaneously and easily compared to heating methods. In addition, the mass can be significantly reduced compared to hydrogen storage alloys. Furthermore, the hydrogen generating composition to be mounted in the hydrogen generating unit can be formed into a desired shape.

[0092] [Fuel cell system] A fuel cell system according to one embodiment of the present invention includes the above-described hydrogen generation system and a fuel cell to which hydrogen is supplied from the hydrogen generation system. The hydrogen generation system is a hydrogen supply source that supplies hydrogen to the fuel cell. Examples of fuel cells include phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and solid polymer fuel cells. According to the fuel cell of this embodiment, hydrogen can be easily supplied to the fuel cell even at room temperature without using a high-pressure tank. [Example]

[0093] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0094] [Synthesis example] Based on Non-Patent Document 1, (BH) n We synthesized a boron hydride-containing sheet with a two-dimensional network consisting of (n≧4). 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. The solution was filtered through a 0.2 μm pore filter, and the filtrate was dried under reduced pressure at 80°C to obtain a yellow product.

[0095] A transmission electron microscope image of the product obtained in Synthesis Example 1 is shown in Figure 10. The transmission electron microscope used was a JEM-2100F manufactured by JEOL Ltd. As shown in Figure 10, the obtained product was confirmed to be a sheet-like substance. The bond energy of the product obtained in Synthesis Example 1 was also measured. An X-ray photoelectron spectrometer (trade name: JPS 9010 TR, manufactured by JEOL Ltd.) was used to measure the bond energy. The results are shown in Figure 11. From the results shown in Figure 11, it was confirmed that a boron signal appeared. Furthermore, the infrared spectrum of the product obtained in Synthesis Example 1 was measured. The infrared spectrum was measured using a Fourier transform infrared spectrophotometer (FT-IR, product name: FT / IR-6100, manufactured by JASCO Corporation). From the results shown in FIG. 12, it is clear that the peak at 2500 cm -1 and 1400cm -1 Peaks due to BH vibration and BHB vibration were observed at the peaks, respectively, and it was confirmed that the product obtained in Synthesis Example 1 was a borohydride-containing sheet having a two-dimensional network.

[0096] [Example 1] Linear sweep voltammetry (LSV) measurements were performed on 1,10-phenanthroline (Phen), a mixture of 1,10-phenanthroline and hydrochloric acid (Phen + acid), and a solvent containing no 1,10-phenanthroline or acid (blank). A potentiostat (product name: HZ-7000, manufactured by Hokuto Denko Corporation) was used for the LSV measurements. The results are shown in Figure 13. The results shown in Figure 13 confirm that current flows under cathodic polarization when 1,10-phenanthroline and hydrochloric acid are mixed. This current is due to hydrogen generation, which will be discussed later. No current was observed under cathodic polarization under phenanthrone-only or blank conditions.

[0097] [Example 2] A composition containing 1,10-phenanthroline (Phen) and a borohydride-containing sheet (HB) with a Phen content of 30 μmol, and a mixture of 1,10-phenanthroline and acid (Phen + acid) that had undergone LSV measurement, were subjected to UV-visible spectrophotometric analysis. A UV-visible spectrophotometer (UV-Vis, product name: V-670, manufactured by JASCO Corporation) was used for the analysis. Measurements were performed at wavelengths ranging from 450 nm to 700 nm. The results are shown in Figure 14. The results shown in FIG. 14 reveal that the above composition and 1,10-phenanthroline that has been subjected to LSV measurement and reduced in the presence of an acid absorb light with wavelengths of 450 nm to 700 nm.

[0098] [Example 3] The amount of hydrogen generated when a mixture of 1,10-phenanthroline and hydrochloric acid (Phen+acid) that had undergone LSV measurement was irradiated with visible light was measured. The hydrogen generation amount measurement device described below was used to measure the amount of hydrogen generated. The visible light irradiated onto the sample had a wavelength of 470 nm or more. The results are shown in Figure 15. The results shown in Figure 15 show that when the sample was not irradiated with visible light, no hydrogen was generated from the sample. When the sample was irradiated with visible light, hydrogen was generated from the sample, and it was confirmed that the amount of hydrogen generated increased over time.

[0099] [Example 4] Infrared spectra were measured for 1,10-phenanthroline (Phen), boron-hydride-containing sheet (HB), and compositions containing 1,10-phenanthroline (Phen) and boron-hydride-containing sheet (HB) (Phen contents of 10 μmol, 30 μmol, 50 μmol, 80 μmol, and 100 μmol). A Fourier transform infrared spectrophotometer (FT-IR, product name: FT / IR-6100, manufactured by JASCO Corporation) was used to measure the infrared spectra. The results are shown in Figure 16. From the results shown in Figure 16, it can be seen that HB and compositions containing Phen and HB exhibited a peak intensity of 2500 cm -1A peak due to BH vibration was observed near the peak. It was also confirmed that as the Phen content increased, the peak due to BH vibration shifted to a lower wavenumber.

[0100] [Example 5] The ultraviolet-visible absorption spectra were measured for 1,10-phenanthroline (Phen), a boron-containing sheet (HB), and a composition containing 1,10-phenanthroline (Phen) and a boron-containing sheet (HB) (Phen contents of 10 μmol, 30 μmol, 50 μmol, 80 μmol, and 100 μmol). A UV-visible spectrophotometer (product name: V-670, manufactured by JASCO Corporation) was used to measure the ultraviolet-visible absorption spectra. The results are shown in Figure 17. The results shown in Figure 17 indicate that Phen does not absorb visible light. It was also confirmed that HB and a composition containing Phen and HB absorb visible light, and that the absorption wavelength shifted to longer wavelengths as the Phen content increased.

[0101] [Example 6] The absorption spectrum of 1,10-phenanthroline (Phen) was calculated using density functional theory (DFT), and the results are shown in Figure 18. From the results shown in Figure 18(a), Phen and [H-Phen] + (Phen that has accepted one proton) [H-Phen] + It was confirmed that the energy difference between the HOMO and LUMO (LUMO+1) is smaller in [H-Phen]. + and [H-Phen] · (Phen, which has accepted one proton and one electron), [H-Phen] · The energy difference between SOMO and SUMO+1 (SUMO+2) is [H-Phen] + It was confirmed that the energy difference between the HOMO and LUMO (LUMO+1) is smaller than that of the HOMO and LUMO (LUMO+1) of the HOMO. Furthermore, the results shown in Figure 18(b) suggest that nitrogen-containing aromatic compounds that have accepted one proton and one electron can absorb visible light.

[0102] [Example 7] The hydrogen release characteristics of a composition containing 1,10-phenanthroline (Phen) and a borohydride-containing sheet (HB) (Phen content: 30 μmol) were evaluated. The evaluation device shown in FIG. 19 was used to evaluate the hydrogen release characteristics. The evaluation device 100 includes a reaction vessel 110, a short-wavelength cut filter 120, and a light source 130. The reaction vessel 110 includes a cylindrical vessel body 111 having a bottom and accommodating a sample solution, a quartz window 112 provided at the top of the vessel body 111, and a sampling port 113 provided at the side of the vessel body 111. A stirrer 140 is disposed within the vessel body 111. A short-wavelength cut filter 120 is fixed to the top of the reaction vessel 110, specifically, to the quartz window 112, by a fixing jig 150. The short-wavelength cut filter 120 blocks light emitted from the light source 130 with wavelengths less than 470 nm and transmits light with wavelengths of 470 nm or greater. The light source 130 is disposed above the reaction vessel 110 via the short-wavelength cut filter 120. A xenon lamp was used as the light source 130.

[0103] The above-described evaluation device 100 was placed in a glove box. In the glove box, the evaluation device 100 was placed on a magnetic stirrer. A sample solution A containing 237 μmol of the borohydride-containing sheet and 30 μmol of 1,10-phenanthroline in 5 mL of acetonitrile was prepared in the reaction vessel 110. The total volume of the sample solution A was 5 mL. While stirring sample solution A by rotating stirring bar 150 with a magnetic stirrer, light with a wavelength of 470 nm or more was irradiated onto the sample solution from light source 130 through short wavelength cut filter 120. During the light irradiation, sample solution A was cooled with cooling water to maintain the temperature of sample solution A at 20°C. After starting to irradiate sample solution A with light, the gas in the space between sample solution A and the quartz window 112 was sampled, and the amount of hydrogen contained in the gas was measured using a gas chromatograph (product name: GC-2014AT, manufactured by Shimadzu Corporation), thereby measuring the amount of hydrogen generated from sample solution A. For comparison, similar measurements were also performed for the cases of 1,10-phenanthroline (Phen) alone and the case of the borohydride-containing sheet (HB) alone. The results are shown in Figure 20. From the results shown in FIG. 20, it was confirmed that when sample solution A was irradiated with visible light, hydrogen was generated from sample solution A, and the amount of hydrogen generated increased with the passage of time.

[0104] [Example 8] The amount of hydrogen generated from sample solution A was measured in the same manner as in Example 7, except that the content of 1,10-phenanthroline in sample solution A was changed to 10 μmol, 52 μmol, 83 μmol, or 100 μmol. The results are shown in FIG. From the results shown in FIG. 21, it was confirmed that the amount of hydrogen generated was maximum when the content of 1,10-phenanthroline was 52 μmol.

[0105] [Example 9] The amount of hydrogen generated from sample solution A was measured in the same manner as in Example 7, except that the wavelength of light irradiated onto the sample solution from light source 130 was changed to 470 nm, 500 nm, 600 nm, and 700 nm. The results are shown in Figure 22. The results shown in Figure 22 confirm that the amount of hydrogen generated increases as the wavelength becomes shorter. Hydrogen was also generated using visible light with wavelengths of 500 nm and 470 nm.

[0106] [Example 10] The amount of hydrogen generated over time was measured in the same manner as in Example 1 for the cases where sample solution A was irradiated with light and where sample solution A was not irradiated with light. The results are shown in FIG. From the results shown in Figure 23, it was confirmed that when sample solution A was irradiated with light, the amount of hydrogen generated increased over time. On the other hand, when sample solution A was not irradiated with light, it was confirmed that almost no hydrogen was generated even over time.

[0107] [Comparative Example 1] The above-described evaluation device 100 was placed in a glove box. In the glove box, the evaluation device 100 was placed on a magnetic stirrer. 10 μmol of 1,10-phenanthroline, 237 μmol of sodium phosphinate, and 237 μmol of formic acid were added to 5 mL of acetonitrile in a reaction vessel 110, and the stirring bar 150 was rotated with a magnetic stirrer to prepare composition α. As a comparative example, composition β was also prepared by dissolving 1,10-phenanthroline (Phen) in acetonitrile, and the UV-visible absorption spectrum was measured. For composition α, the UV-visible absorption spectrum was measured for both compositions irradiated with visible light and those not irradiated with visible light. A UV-visible spectrophotometer (product name: V-670, manufactured by JASCO Corporation) was used to measure the UV-visible absorption spectrum. The results are shown in Figure 24. From the results shown in Figure 24, it was found that composition α absorbs visible light both when irradiated with visible light and when not irradiated with visible light. It was also found that composition β, in which 1,10-phenanthroline (Phen) was dissolved in acetonitrile, does not absorb visible light.

[0108] Comparative Example 2 While stirring the sample solution by rotating a stirring bar 150 of a magnetic stirrer, the sample solution was irradiated with light having a wavelength of 470 nm or more from a light source 130 through a short wavelength cut filter 120. During the light irradiation, the sample solution was cooled with cooling water to maintain the temperature of the sample solution at 20°C. After the start of light irradiation of the sample solution, the gas in the space between the sample solution and the quartz window 112 was sampled, and the amount of hydrogen contained in the gas was measured using a gas chromatograph (product name: GC-2014AT, manufactured by Shimadzu Corporation), thereby measuring the amount of hydrogen generated from the sample solution. For comparison, a similar measurement was also performed without light irradiation. The results are shown in Figure 25. From the results shown in Figure 25, it was confirmed that when the sample solution was irradiated with visible light, hydrogen was generated from the sample solution, and the amount of hydrogen generated increased over time. However, the amount of hydrogen generated was smaller than in the above-mentioned examples. On the other hand, it was confirmed that almost no hydrogen was generated when the sample solution was not irradiated with light. [Explanation of symbols]

[0109] 1~5 Hydrogen generation system 10 Hydrogen generation unit 11 Raw material supply tank 12 Solvent supply path 13 Gas recovery line 14 Exhaust channel 15 Stirring section 16 Gas supply line 17 Airflow generating section 18 Thin container 19 Conveyor belt 20 Visible light control unit 21 LED light source 30 Borohydride-containing composition 31 Borohydride-containing sheet 32 Solvent 40 Support beads 41 beads 50 films 51 Binder 100 Evaluation Device 110 Reaction vessel 111 Container body 112 Quartz window 113 Sampling port 120 Short wavelength cut filter 130 Light source 140 Stirring bar 150 Fixture

Claims

1. A hydrogen generating composition comprising a nitrogen-containing aromatic compound that has accepted one proton and one electron.

2. The hydrogen generating composition according to claim 1 , wherein the nitrogen-containing aromatic compound absorbs light having a wavelength of 500 nm or more.

3. The hydrogen generating composition according to claim 1 , wherein the nitrogen-containing aromatic compound is phenanthroline and its derivatives.

4. As the substance that donates the protons and the electrons, (BH) ｎ 2. The hydrogen generating composition of claim 1, comprising a borohydride-containing sheet having a two-dimensional network consisting of (n≧4, where n is an integer).

5. 5. The hydrogen generating composition according to claim 4, which comprises a nitrogen-containing aromatic compound that has accepted electrons and protons from the borohydride-containing sheet, and which generates hydrogen when irradiated with visible light.

6. The hydrogen generating composition of claim 1 , comprising a solvent.

7. The hydrogen generating composition according to any one of claims 1 to 6, a control unit that controls irradiation of the hydrogen generating composition with visible light; A hydrogen generation system comprising: a hydrogen generation unit that extracts hydrogen to the outside.

8. A hydrogen generation system according to claim 7; a fuel cell to which hydrogen is supplied from the hydrogen generation system.

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