Methods and apparatus for using hydrogen storage materials and fuel cell systems

Abstract

To provide a method and an apparatus that enable rehydrogenation after hydrogen release of borohydride composed of (HB)n(n≥4) as a hydrogen storage material so that the borohydride can be used repeatedly and the rehydrogenation can be performed without using a heating process.SOLUTION: A method for using a hydrogen storage material includes a rehydrogenation step of placing a hydrogen desorbed boron given by hydrogen being desorbed from borohydride composed of (HB)n(n≥4) under pressurized hydrogen of 4 MPa or more, whereby hydrogen is recombined with the hydrogen desorbed boron to form the borohydride. The rehydrogenation can be carried out without using a heating process. An exemplary embodiment of the hydrogen storage material is a hydrogen storage material supported on a bendable resin carrier.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for using hydrogen boride as a hydrogen storage material, and to a fuel cell system using the apparatus. [Background technology]

[0002] Hydrogen is attracting attention as a clean energy source because its combustion or reaction emits water. For example, there is vigorous development underway to use hydrogen as the negative electrode active material in fuel cells, and to use it as fuel for automobiles and power supply equipment.

[0003] One method for storing hydrogen and supplying it when needed involves combining (hydrogenating) hydrogen into a hydrogen storage material and then desorbing and releasing it when needed. Hydrogen storage alloys are well-known as hydrogen storage materials, but in recent years, complex hydrides have attracted attention as materials with high storage density. However, complex hydrides require a lot of energy, such as heating, when releasing and re-hydrogenating hydrogen, and if they are to be used in an actual hydrogen storage system, a heat exchanger will be necessary, which will reduce the overall storage efficiency of the system.

[0004] Patent Document 1 describes a mixed material containing LiH and MgB2 as a hydrogen storage material, and states that if the MgB2 is pre-treated with a predetermined ball mill without external heating, the mixed material containing LiH and MgB2 can then be hydrogenated at a temperature of 300-375°C, which is lower than the temperature of the conventional technology (400°C or higher). However, external heating is still necessary for hydrogenation. Furthermore, when desorbing and releasing hydrogen from a mixed material containing hydrogenated LiH and MgB2, heating up to 450°C is required.

[0005] Patent Document 2 describes (HB) as a hydrogen storage material with high storage density. nA two-dimensional network structure of hydrogen boride consisting of (n≧4) has been investigated, and it has been described that hydrogen can be released at room temperature and atmospheric pressure without using a heating process by irradiating the hydrogen boride with light. However, in order to repeatedly use hydrogen boride as a hydrogen storage material, it is necessary to rehydrogenate the hydrogen boride after it has released its hydrogen. Since a method for doing so has not yet been established, it is currently not possible to reuse it repeatedly. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-148644 [Patent Document 2] Japanese Patent Publication No. 2019-218251 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Therefore, the objective of the present invention is to use (HB) as a hydrogen storage material. n The objective is to enable the rehydrogenation of hydrogen boride (n≧4) after hydrogen release, thereby allowing for repeated use of hydrogen boride, and to perform rehydrogenation without using a heating process. [Means for solving the problem]

[0008] [1] (HB) as a hydrogen storage material n A method for using a hydrogen storage material, comprising a rehydrogenation step in which hydrogen is recombined with hydrogen-desorbed boron, which is obtained by desorbing hydrogen from hydrogen boride consisting of (n≧4), under a hydrogen pressure of 4 MPa or more, thereby converting part or all of the hydrogen-desorbed boron into hydrogen boride.

[0009] [2] (HB) as a hydrogen storage material n A hydrogen release step involves irradiating hydrogen boride (n≧4) with light to remove hydrogen from the hydrogen boride to obtain hydrogen-desorbed boron, and A method for using a hydrogen storage material, comprising a rehydrogenation step of recombining hydrogen with the hydrogen-desorbed boron by placing it under a hydrogen pressure of 4 MPa or more to convert part or all of the hydrogen-desorbed boron into the hydrogen boride.

[0010] [3] A method of using the hydrogen storage material described in [1] or [2] above, wherein hydrogen boride is supported on a bendable resin carrier.

[0011] [4] (HB) as a hydrogen storage material n A hydrogen storage material usage apparatus comprising a rehydrogenation device that recombines hydrogen with hydrogen-desorbed boron, which is obtained by desorbing hydrogen from hydrogen boride consisting of (n≧4), under a pressurized hydrogen of 4 MPa or more, thereby converting some or all of the hydrogen-desorbed boron into the aforementioned hydrogen boride.

[0012] [5] (HB) as a hydrogen storage material n A hydrogen release device that removes hydrogen from hydrogen boride consisting of (n≧4) by irradiating it with light to produce hydrogen-desorbed boron, A device for using hydrogen storage materials, comprising a rehydrogenation device that recombines hydrogen with the hydrogen-desorbed boron by placing the hydrogen-desorbed boron under a pressurized hydrogen of 4 MPa or more, thereby converting part or all of the hydrogen-desorbed boron into the hydrogen boride.

[0013] [6] A device for using the hydrogen storage material described in [4] or [5] above, wherein hydrogen boride is supported on a bendable resin carrier.

[0014] [7] A fuel cell system comprising a device for using the hydrogen storage material described in [4] or [5] above, combined with a fuel cell.

[0015] [Effect] In the above [1] or [4], (HB) nWhen hydrogen desorbed boron hydride formed by desorbing hydrogen from boron hydride consisting of (n≧4) is placed under pressurized hydrogen of 4 MPa or more, hydrogen recombines with the hydrogen desorbed boron hydride. This is presumably because the site from which hydrogen has desorbed from the boron hydride reacts with the pressurized hydrogen while maintaining its activity. Thus, for the first time, the rehydrogenation after hydrogen release of boron hydride, which has not been established until now, has become possible. Moreover, since the rehydrogenation can be carried out without using a heating process, it is simple, and it is also possible to apply boron hydrides to a resin carrier or fill them into a resin container, etc.

[0016] Furthermore, according to the above [2] or [5], hydrogen release can also be carried out without using a heating process. That is, since both hydrogen release and rehydrogenation can be carried out without using a heating process, it is very simple.

[0017] Also, according to the above [3] or [6], since the resin carrier carrying the hydrogen storage material can be bent, the degree of freedom in attaching it to a container or the like increases, and it also becomes easier to control the light irradiation surface, etc.

Effects of the Invention

[0018] According to the present invention, rehydrogenation after hydrogen release of boron hydride (HB) n consisting of (n≧4), and thus repeated use of boron hydride becomes possible for the first time, and moreover, it has an excellent effect that the rehydrogenation can be carried out without using a heating process.

Brief Description of the Drawings

[0019] [Figure 1] Figure 1 is a schematic diagram showing the local structure of boron hydride. [Figure 2] Figure 2 is a schematic diagram showing the outline of the present invention. [Figure 3] Figure 3(a) is a perspective view of the hydrogen release device in Example 1, and (b) is a wavelength spectrum diagram of a mercury xenon lamp. [Figure 4] Figure 4 is a graph showing the relationship between the amount of hydrogen generated and the light irradiation time in the same hydrogen release. [Figure 5] Figure 5 is a schematic diagram of the rehydrogenation apparatus in Example 1. [Figure 6] Figure 6 is a graph showing the temperature change and pressure change in the same rehydrogenation. [Figure 7] Figure 7 is a schematic diagram showing Blank Measurement Part 1 by the same rehydrogenation apparatus. [Figure 8] Figure 8 is a schematic diagram showing Blank Measurement Part 2 by the same rehydrogenation apparatus. [Figure 9] Figure 9 is a graph showing the hydrogen storage amount at each pressure in the same rehydrogenation. [Figure 10] Figure 10 is a schematic diagram showing the hydrogen release step and rehydrogenation step of Example 2.

Mode for Carrying Out the Invention

[0020] [1] (HB) n Borohydride consisting of (n ≧ 4) (HB) n The borohydride consisting of (n ≧ 4) is a sheet-like substance having a two-dimensional network formed by boron atoms (B) and hydrogen atoms (H) in a molar ratio of 1:1 (see Patent Document 2). Fig. 1(a) shows a schematic diagram of the local structure of the borohydride.

[0021] (HB) n The borohydride consisting of (n ≧ 4) may be a derivative thereof, or may include both the borohydride and its derivative, or may be a composition obtained by adding additives such as dopants thereto. Here, "its derivative" refers to a compound obtained by introducing other elements using the borohydride as a starting material, as well as a compound having the borohydride as a main skeleton (for example, a compound whose terminal is sealed with an oxide), regardless of whether or not the borohydride is used as a starting material. Here, the main skeleton refers to a substance in which the proportion of the borohydride contained in the compound is 80% or more. As the borohydride-containing substance, a structure in which a plurality of sheets of the borohydride (sheet-like) are stacked may be used.

[0022] [2] Hydrogen release step and hydrogen release apparatus The conditions for irradiating hydrogen boride with light (wavelength, intensity, time, irradiation area, etc.) are not limited to those that can induce the reaction shown in Chemical Formula 1 below and generate hydrogen. [C1] 2HB→H2↑+2B The desired amount of hydrogen generated can be designed by adjusting the irradiation conditions. From the viewpoint of ease of handling, the irradiation band is preferably ultraviolet light (240-400 nm) and / or visible light (above 400 nm, below 750 nm). This embodiment enables hydrogen generation by light irradiation at room temperature and atmospheric pressure, but this does not preclude the use of a heating process in combination.

[0023] The light spectrum that induces the above chemical formula 1 varies depending on the boronide-containing material. When using only a two-dimensional boronide sheet as the boronide-containing material, ultraviolet light is preferred. By using a derivative of the two-dimensional boronide sheet, or by doping at least one of the two-dimensional boronide sheet and its derivative with a dopant, the spectrum in which hydrogen is generated can be shifted to the longer wavelength side or the shorter wavelength side. From the viewpoint of efficiently utilizing sunlight and indoor light, boronide-containing materials that decompose with visible light are preferred. Furthermore, in order to generate hydrogen with visible light, in addition to the doping, another substance that absorbs visible light may be supported on the surface of the boronide-containing material.

[0024] [3] Hydrogen-desorbed boron Hydrogen-desorbed boron is (HB) n It is sufficient that the hydrogen is removed from (n≧4) hydrogen boride, and the amount of removal is not particularly limited.

[0025] [4] Rehydrogenation step and rehydrogenation apparatus As described above, hydrogenation of hydrogen-desorbed boron with pressurized hydrogen can be carried out without a heating process, and therefore it is preferable to carry it out at room temperature or at a temperature that has been raised by pressurizing from room temperature. However, this does not preclude the use of a heating process in combination.

[0026] [5]Usage The hydrogen storage material apparatus of the present invention can be applied to a wide range of applications where hydrogen is desired, and is particularly suitable for use in combination with fuel cells. [Examples]

[0027] As outlined in Figure 2, the synthesized hydrogen boride underwent a hydrogen release step and a rehydrogenation step. Specifically, Example 1, which involved measurements, and Example 2, which was an application, were performed.

[0028] [Example 1] First, we will describe Example 1 shown in Figures 3 to 9. <1> Synthesis of hydrogen boride According to the method described in "Example 1: Synthesis" of Patent Document 2, (HB) n We synthesized hydrogen boride consisting of (n≧4).

[0029] <2> Hydrogen release step Using the hydrogen release device shown in Figure 3, the above <1> A hydrogen release step was performed in which hydrogen was removed from the hydrogen boride synthesized by irradiating it with light to obtain hydrogen-desorbed boron. Specifically, the hydrogen release step was as follows (a) to (c), and the amount of hydrogen generated was measured as follows (d).

[0030] (a) 100 mg of powdered hydrogen boride was placed in a petri dish (φ32 mm), 5 drops of acetonitrile were added, and then it was vacuum dried. (i) Inside a glove box (not shown) under an argon atmosphere, the petri dish containing the above-mentioned hydrogen boride was placed inside a transparent quartz glass collection container (internal volume 500 ml), which was then placed on a stand inside the glove box and sealed. (c) A mercury xenon lamp (Hayashi Repic "LA-410UV 200W", wavelength spectrum shown in Figure 3(b)) was used to irradiate the top surface of the hydrogen boride in the petri dish from directly above the collection container, through the transparent lid of the collection container.

[0031] (e) Gas samples were taken from the collection container at 60 minutes and 120 minutes after the start of light irradiation, and the hydrogen concentration was measured using a gas chromatograph with a barrier discharge ionization detector (BID) (Shimadzu Corporation "Tracera, BID-2010Plus"). As shown in Figure 4, the hydrogen concentration was 7229 ppm at 60 minutes and 7781 ppm at 120 minutes, confirming the generation of hydrogen due to light irradiation and the dependence of the amount of hydrogen generated on the light irradiation time.

[0032] Here, the hydrogen concentration of 7781 ppm in the collection container (internal volume 500 ml) is converted to a hydrogen generation amount of 0.35 mg. This hydrogen generation amount of 0.35 mg is 0.35 wt% relative to 100 mg of hydrogen boride, and is 4.1 wt% relative to the maximum amount of hydrogen generated from the above amount of hydrogen boride (amount of hydrogen contained in hydrogen boride) of 8.5 mg. Thus, the amount of hydrogen generated was small compared to the maximum amount of hydrogen generated, which is thought to be because, in the irradiation method of hydrogen boride in this embodiment, the hydrogen desorption reaction proceeded only on the surface of the hydrogen boride. As mentioned above, the amount of desorption is not limited, so even if some hydrogen is desorbed from the hydrogen boride in this embodiment, it will be considered hydrogen-desorbed boron.

[0033] <3> Rehydrogenation step The PCT characteristic measuring device (PCT-2SDWIN, manufactured by Suzuki Shokan, P: pressure, C: storage capacity, T: temperature) shown in Figure 5 was used as a rehydrogenation apparatus. In this apparatus, a gas source (not shown) is connected to the reservoir via an electromagnetic valve V3, a sample tube is connected via an electromagnetic valve V2 and a flow path, and a vacuum pump is connected via an electromagnetic valve V1. The main lower part of the sample tube can be heated in an electric furnace, but it is not heated in this embodiment. The flow path below electromagnetic valve V2 and the part of the sample tube that exits the electric furnace are collectively called the "line (room temperature portion)," and the part of the sample tube that enters the electric furnace is called the "reactor (heatable portion)." Thermocouples are provided to measure the reservoir temperature T1, the line temperature T2, and the reactor temperature T3, respectively.

[0034] Using the same device, <2> A rehydrogenation step was performed in which hydrogen-desorbed boron, after light irradiation (120 minutes), was placed under a pressurized hydrogen of 4 MPa or more to recombine hydrogen with the hydrogen-desorbed boron and return it to the aforementioned hydrogen boride. Specifically, the rehydrogenation step was as follows (a), and the measurement of the amount of hydrogen restored was as follows (a) to (d). The measurements were performed in the order of (b), (c), and (a), but for convenience, they will be explained in the order of (a), (b), and (c).

[0035] (a) As shown in Figure 5(a), 20 mg of the above-mentioned hydrogen-desorbed boron was placed in a sample tube as a sample, valve V3 was opened with valves V1 and V2 closed, and hydrogen gas and helium gas were pressurized and introduced into the reservoir. After that, valve V3 was closed, and the temperature and pressure (T1, P) after the reservoir temperature and pressure reached equilibrium were recorded. Next, as shown in Figure 5(b), valve V2 was opened, and hydrogen in the reservoir was introduced into the line and reactor (room temperature, ~8 MPa), and sufficient time was waited for equilibrium to be reached at each pressure (30 minutes or more each), and the temperature change and pressure change were recorded (T1', T2', T3', P'). The results are shown in Figure 6.

[0036] (i) Blank measurement part 1 As shown in Figure 7, with no hydrogen-desorbed boron placed in the sample tube as a sample, helium gas was used instead of hydrogen gas as the introduction gas, and blank measurement 1 was performed using the same procedure (a) and (b) as in (a) above (room temperature, ~5 MPa). The samples were allowed to stand for a sufficient amount of time to reach equilibrium at each pressure (30 minutes or more each), and the temperature and pressure changes were recorded.

[0037] (c) Blank measurement part 2 As shown in Figure 8, 20 mg of the hydrogen-desorbed boron sample was placed in the sample tube as in (a) above, and helium gas was used as the introduction gas instead of hydrogen gas. Blank measurement 2 was performed using the same procedure (a) and (b) as in (a) above (room temperature, ~5 MPa). At each pressure, the sample was allowed to reach equilibrium (approximately 10 minutes each), and the temperature and pressure changes were recorded.

[0038] (e) Calculation of hydrogen recombination amount From the results of the blank measurement 1 described above, the sum of the line volume and reactor volume was calculated. Based on the results of the blank measurement 2 described above (c), the sum of the line and reactor volumes was calculated. It can be assumed that helium gas has low reactivity with the sample and does not exhibit storage phenomena. The difference in volume obtained from (i) and (iii) above represents the volume occupied by the sample, and from this, the true density of the sample was determined. He and H2 densities were referenced from NIST data (https: / / webbook.nist.gov / chemistry / fluid / ). In (a) above, if there is a difference in the weight of gaseous hydrogen between Figures 5(a) and (b), that difference is hydrogen that has recombined (stored) with hydrogen-desorbed boron, and the amount of recombination (hydrogen storage) was calculated from Equation 1 below. The hydrogen storage amount (percentage of hydrogen-desorbed boron) calculated at each pressure is shown in Figure 9. The hydrogen storage amount at 7.9 MPa was 0.41 wt%.

number

[0039] This hydrogen storage amount of 0.41 wt% is as described above. <1> The amount of hydrogen generated was approximately 0.35 wt%, which is similar to that observed in the previous case. This suggests that a rehydrogenation reaction proceeded at the active site (Figure 2) where hydrogen was removed from the hydrogen-desorbed boron, indicating that the hydrogen-desorbed boron was converted back to hydrogen boride.

[0040] [Example 2] Next, in Example 2 shown in Figure 10, hydrogen boride synthesized in the same manner as in Example 1 was used, and the hydrogen release step and rehydrogenation step were carried out as follows.

[0041] <1> Hydrogen release step As shown in (a), a bendable resin carrier (for example, a 15 mm square flat plate made of polypropylene, polyethylene naphthalate, etc.) was prepared. As shown in (b), a solution of hydrogen boride (100 mg) dissolved or dispersed in 5 ml of acetonitrile was dropped onto the upper surface of a horizontally positioned resin carrier until it could be held by surface tension. As shown in (c), acetonitrile was removed by vacuuming, and a hydrogen boride coating was applied. As shown in (d), hydrogen was removed from the hydrogen boride by irradiating it with light from the same mercury xenon lamp as in Example 1, thereby obtaining hydrogen-desorbed boron. The released hydrogen can be collected and utilized using a collection container as in Example 1.

[0042] <2> Rehydrogenation step As shown in (e), the resin support body with hydrogen-desorbed boron was placed in a reaction vessel for hydrogen pressurization with cylindrical side walls. At this time, the resin support body could be easily inserted into the reaction vessel by bending it into a cylindrical shape. As shown in (f), the reaction vessel was sealed, and pressurized hydrogen of 4 MPa or more was introduced into the reaction vessel to recombine hydrogen with hydrogen-desorbed boron to produce the hydrogen boride.

[0043] It should be noted that the present invention is not limited to the embodiments described above, and can be appropriately modified and implemented without departing from the spirit of the invention.

Claims

1. (HB) as a hydrogen storage material ｎ A method for using a hydrogen storage material, comprising a rehydrogenation step in which hydrogen is recombined with hydrogen-desorbed boron, which is obtained by desorbing hydrogen from hydrogen boride (n≧4), under a hydrogen pressure of 4 MPa or more, thereby converting part or all of the hydrogen-desorbed boron into hydrogen boride.

2. (HB) as a hydrogen storage material ｎ A hydrogen release step involves irradiating hydrogen boride (n≧4) with light to remove hydrogen from the hydrogen boride to obtain hydrogen-desorbed boron, and A method for using a hydrogen storage material, comprising a rehydrogenation step of recombining hydrogen with the hydrogen-desorbed boron by placing it under a hydrogen pressure of 4 MPa or more to convert part or all of the hydrogen-desorbed boron into the hydrogen boride.

3. A method for using the hydrogen storage material according to claim 1 or 2, wherein hydrogen boride is supported on a bendable resin carrier.

4. (HB) as a hydrogen storage material ｎ A hydrogen storage material usage apparatus comprising a rehydrogenation device that recombines hydrogen with hydrogen-desorbed boron, which is obtained by desorbing hydrogen from hydrogen boride (n≧4), under a pressurized hydrogen of 4 MPa or more, thereby converting some or all of the hydrogen-desorbed boron into hydrogen boride.

5. (HB) as a hydrogen storage material ｎ A hydrogen release device that removes hydrogen from hydrogen boride (containing n≧4) by irradiating it with light to obtain hydrogen-desorbed boron, A device for using hydrogen storage materials, comprising a rehydrogenation device that recombines hydrogen with the hydrogen-desorbed boron by placing the hydrogen-desorbed boron under a hydrogen pressure of 4 MPa or more to convert part or all of the hydrogen-desorbed boron into the hydrogen boride.

6. The apparatus for using a hydrogen storage material according to claim 4 or 5, wherein hydrogen boride is supported on a bendable resin support.

7. A fuel cell system comprising a device for using the hydrogen storage material according to claim 4 or 5, combined with a fuel cell.

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