Hydrogen adsorbent material and method of making same

Abstract

One embodiment of the present application relates to a lithium-modified boron hydride containing lithium and boron hydride, in which an absorption peak is observed in the range of 1100 cm ‑1 - 1500 cm ‑1 -1 when an IR spectrum is measured by a total reflection absorption method, and the absorption peak is a peak in which an absorption peak (la) having a maximum value in the range of 1300 cm ‑1 - 1400 cm ‑1 -1 overlaps with an absorption peak (lb) having a maximum value in the range of 1200 cm ‑1 - 1300 cm ‑1 -1.

Description

Technical Field

[0001] One aspect of the present invention relates to hydrogen adsorption materials and methods for manufacturing the same. Background Technology

[0002] In recent years, hydrogen, as a decarbonization measure and a clean energy source, has attracted much attention. In fuel cell electric vehicles, hydrogen is filled at high pressure (70 MPa), requiring technologies that can store hydrogen at lower pressures and with a higher density than compressed gas.

[0003] For example, Japanese Patent Application Publication No. 2023-151415 discloses a material containing a metal-supported two-dimensional boron sheet, which has the properties of (M... x H 1-x B) n (M is an alkali metal atom or a group IIA element, H is a hydrogen atom, B is a boron atom, 0.01≤x≤1, n≥6) constitutes a two-dimensional network, wherein the B atoms are arranged in a hexagonal ring, and the network is a two-dimensional network formed by connecting the hexagons formed by the B atoms, and at least the M atoms and the B atoms are bonded by a three-center two-electron bond or a two-center two-electron bond. Summary of the Invention

[0004] The report shows that when hydrogen boride (HB) can be dispersed at the atomic level and endowed with alkali metal atoms and / or alkaline earth metal atoms, the hydrogen adsorption capacity of the resulting composite compound is theoretically increased (Phys. Chem. Chem. Phys., 2018, 20, 30304-30311 and International Journal of Hydrogen Energy, 2021, 46, 39273-39283).

[0005] One method for imparting alkali metal atoms and alkaline earth metal atoms to compounds is vacuum vapor deposition. However, in vapor deposition, alkali metal atoms and alkaline earth metal atoms tend to aggregate, making it difficult to disperse these atoms at the atomic level and uniformly introduce them into the powder sample.

[0006] In addition, there is a method, as shown in Japanese Patent Application Publication No. 2023-151415, which involves introducing alkali metals or alkaline earth metals in the form of salts, ionizing them in a solvent, mixing them with the compound, and then drying them. However, in this case, these atoms are introduced into the compound in an ionized state, making it difficult to introduce them in the form of atoms.

[0007] Therefore, in the prior art, there is no established hydrogen adsorption material that can demonstrate sufficient hydrogen adsorption capacity, nor is there a simple method for manufacturing such a hydrogen adsorption material.

[0008] Therefore, one objective of the present invention is to provide a hydrogen adsorption material having a high hydrogen adsorption capacity and a simple method for manufacturing the hydrogen adsorption material.

[0009] The inventors investigated various methods for solving the aforementioned problems. As a result, they discovered that by applying shear force to lithium metal and hydrogen boride and mixing them, the hydrogen adsorption capacity of the resulting lithium-modified hydrogen boride increased. Based on the above, the inventors completed one aspect of the present invention.

[0010] That is, the gist of one aspect of the present invention is as follows.

[0011] (1) A lithium-modified borohydride comprising lithium and borohydride, which, when measured by total reflectance absorption spectra, exhibits a high IR spectrum at 1100 cm⁻¹. -1 ~1500cm -1 An absorption peak was observed within the range of [a certain value], with a maximum value at 1300 cm⁻¹. -1 ~1400cm -1 The absorption peak (Ia) and maximum value exist in the range of 1200 cm⁻¹. -1 ~1300cm -1 The peak is formed by the overlap of absorption peaks (Ib) in the range.

[0012] (2) The lithium-modified hydrogen borate according to (1), wherein the area ratio (Ia / Ib) of the separated absorption peak (Ia) to the absorption peak (Ib) is in the range of 0.5 to 0.8.

[0013] (3) Lithium-modified hydrogen borate according to (1) or (2), wherein the molar ratio of boron to lithium (B / Li) calculated by ICP is in the range of 0.8 or more.

[0014] (4) Lithium-modified hydrogen borate according to any one of (1) to (3), wherein the molar ratio (H / B) of hydrogen calculated by TPD to boron calculated by ICP is in the range of 1.2 or less.

[0015] (5) Lithium-modified borohydride according to any one of (1) to (4), wherein the temperature-hydrogen intensity curve obtained by TPD determination has a hydrogen release peak with the peak apex in the range of 500°C to 600°C.

[0016] (6) A method for manufacturing lithium-modified borohydride comprising lithium and borohydride, comprising a step of applying shear force to lithium metal and borohydride and mixing them.

[0017] (7) The method according to (6), wherein the mixing is carried out using a mortar and pestle under an inactive atmosphere.

[0018] According to one aspect of the present invention, a hydrogen adsorption material with high hydrogen adsorption capacity and a simple method for manufacturing the hydrogen adsorption material are provided. Attached Figure Description

[0019] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, wherein like symbols denote like elements, wherein:

[0020] Figure 1 This is a schematic diagram illustrating the structure of lithium-modified hydrogen boride according to one aspect of the present invention (in which the molar ratio of hydrogen to boron (H / B) is 1).

[0021] Figure 2A This is a graph showing the amount of hydrogen adsorbed at 298 K under various pressures for Li / HB, HB, and LiB2.

[0022] Figure 2B This is a graph showing the amount of hydrogen adsorbed at 77K under various pressures for Li / HB and HB.

[0023] Figure 3A This is a graph representing the IR spectrum of HB based on the total reflection absorption (ATR) method.

[0024] Figure 3B This is a graph showing the IR spectrum of Li / HB based on total reflectance absorption (ATR).

[0025] Figure 4A This is a graph showing the EEM spectrum of HB.

[0026] Figure 4B This is a graph showing the EEM spectrum of Li / HB.

[0027] Figure 5A This is a chart showing the amount of hydrogen released from HB at various temperatures.

[0028] Figure 5B This is a graph showing the amount of hydrogen released at various temperatures for Li / HB. Detailed Implementation

[0029] Hereinafter, a preferred embodiment of one aspect of the present invention will be described in detail.

[0030] In this specification, features of one aspect of the invention are described with appropriate reference to the accompanying drawings. In the drawings, for clarity, the dimensions and shapes of various parts are sometimes exaggerated and do not accurately depict the actual dimensions and shapes. Therefore, the technical scope of one aspect of the invention is not limited to the dimensions and shapes of the parts shown in these drawings. It should be noted that the hydrogen adsorption material and its manufacturing method according to one aspect of the invention are not limited to the following embodiments, and can be implemented in various ways by modifications and improvements that can be made by those skilled in the art without departing from the spirit of one aspect of the invention.

[0031] One embodiment of the present invention comprises lithium and hydrogen borate.

[0032] In the lithium-modified hydrogen borodide IR spectrum of one embodiment of the present invention, based on total reflectance absorption (ATR), at 1100 cm⁻¹ -1 ~1500cm -1 An absorption peak (hereinafter also referred to as peak (Iab)) was observed in the range.

[0033] The peak (Iab) is not a single absorption peak, but rather a shape formed by the overlap of two or more absorption peaks. In one embodiment, the peak (Iab) consists of two absorption peaks, i.e., the maximum value (peak apex) is located at 1300 cm⁻¹. -1 ~1400cm -1 The absorption peaks (hereinafter also referred to as peak (Ia)) are located in the range of 1200 cm⁻¹, and the maximum value exists at 1200 cm⁻¹. -1 ~1300cm -1 The peak is formed by the overlap of absorption peaks (hereinafter also referred to as peak (Ib)) within the range of Ia. In this embodiment, the area ratio (Ia / Ib) of the separated peak (Ia) to peak (Ib) is typically in the range of 0.5 to 0.8, and in one embodiment it is in the range of 0.6 to 0.7.

[0034] Here, the IR spectra based on ATR are measured in an inactive atmosphere, such as an argon atmosphere, and at room temperature, such as 20°C to 25°C.

[0035] It should be noted that, under the same conditions, the IR spectrum of hydrogen boride measured at 1100 cm⁻¹... -1 ~1500cm -1 An absorption peak was observed within the range, but the maximum value of this absorption peak was observed at 1300 cm⁻¹. -1 ~1400cm -1 The single peak within the range is presumed to be an absorption peak based on the B-H-B vibration. Therefore, in the lithium-modified borohydride of one embodiment of the present invention, peak (Ia) is presumed to be an absorption peak based on the B-H-B vibration, and peak (Ib) is presumed to be an absorption peak based on the Li-B vibration.

[0036] In the ATR-based IR spectrum of lithium-modified borohydride according to one aspect of the present invention, since there is an absorption peak formed by the overlap of two absorption peaks in the above range, it can be known that lithium is not ionized in the lithium-modified borohydride but is uniformly dispersed in the borohydride at the atomic level.

[0037] In one embodiment of the lithium-modified borohydride of the present invention, the molar ratio of boron to lithium (B / Li) calculated by ICP (Inductively Coupled Plasma) is typically in the range of 0.8 or higher, in one embodiment it is in the range of 1.0 or higher, in another embodiment it is in the range of 1.2 or higher, in another embodiment it is in the range of 1.4 or higher, in another embodiment it is in the range of 1.6 or higher, in another embodiment it is in the range of 1.8 or higher, and in another embodiment it is in the range of 1.9 or higher. There is no upper limit to the molar ratio of boron to lithium (B / Li) calculated by ICP. The molar ratio of boron to lithium (B / Li) calculated by ICP is typically in the range of 2.1 or lower, and in one embodiment it is in the range of 2.0 or lower.

[0038] Here, the ICP measurement conditions are well known in the art. In one embodiment, the ICP measurement conditions are as follows: using an ICP luminescence analyzer ICPS-8100 manufactured by Shimadzu Corporation, and setting the measurement wavelengths for lithium and boron to 670.785 nm and 249.773 nm, respectively, for quantitative analysis.

[0039] Furthermore, in one aspect of the lithium-modified hydrogen boride of the present invention, the molar ratio (H / B) of hydrogen calculated by TPD (Temperature-Programmed Desorption) to boron calculated by ICP is typically in the range of 1.2 or less, and in one embodiment, it is in the range of 1.1 or less. There is no lower limit to the molar ratio (H / B) of hydrogen calculated by TPD to boron calculated by ICP. The molar ratio (H / B) of hydrogen calculated by TPD to boron calculated by ICP is typically in the range of 0.9 or more, and in one embodiment, it is in the range of 1.0 or more.

[0040] Furthermore, in one aspect of the present invention, the lithium-modified borohydride exhibits a hydrogen release peak (hydrogen release peak) in the temperature-hydrogen intensity curve obtained by TPD measurement, with a maximum value (peak) in the range of 500°C to 600°C. More specifically, in one aspect of the present invention, the amount of hydrogen released increases with increasing temperature from around 100°C, reaching a maximum value in the range of 150°C to 250°C. Then, although the amount of hydrogen released gradually decreases while repeatedly increasing and decreasing with increasing temperature, it increases again with increasing temperature from around 360°C, reaching a maximum value in the range of 500°C to 600°C, and then decreases with increasing temperature. In this case, the lithium-modified borohydride of one aspect of the present invention exhibits at least a hydrogen release peak with a maximum value in the range of 150°C to 250°C and a hydrogen release peak with a maximum value in the range of 500°C to 600°C in the temperature-hydrogen intensity curve obtained by TPD measurement. It should be noted that, when hydrogen boride (HB) is used alone, no peak (with a apex) indicating hydrogen release is observed in the temperature-hydrogen intensity curve obtained by TPD determination in the range of 500℃ to 600℃.

[0041] Here, the ICP determination conditions are as described above. TPD determination is performed by quantifying the hydrogen produced during heating of the sample in a device consisting of a high-sensitivity differential thermal balance and a quadrupole mass spectrometer at a heating rate of 10 K / min.

[0042] By ensuring that the molar ratio of boron to lithium calculated via ICP and the molar ratio of hydrogen to boron calculated via TPD in lithium-modified hydrogen boride fall within the aforementioned ranges, it can be confirmed that lithium is stably modified into hydrogen boride.

[0043] The lithium-modified hydrogen borate of one embodiment of the present invention does not emit light even when irradiated with light of wavelengths from 250 nm to 650 nm.

[0044] It should be noted that hydrogen boride exhibits a maximum light peak around 400 nm when illuminated with light at a wavelength of 332 nm. Therefore, since the lithium-modified hydrogen boride of one embodiment of the present invention does not exhibit luminescence, it can be understood that the lithium-modified hydrogen boride of one embodiment of the present invention is a substance with properties different from hydrogen boride.

[0045] Figure 1The diagram illustrates the structure of lithium-modified borosilicate (BH) in one embodiment of the present invention, where the molar ratio of hydrogen to boron (H / B) is 1. B has a six-membered ring network, B:H = 1:1. H exists in the form of BHB, which crosslinks the BB of the six-membered ring, but can also form B-H bonds at the edges or around defects in the form of terminal B-H bonds. Li is located on top of BHB, but can also be located in the center of the six-membered ring, on top of B, and / or on top of H in BH. It should be noted that the six-membered ring can also be flexible rather than completely planar.

[0046] In one embodiment of the present invention, the hydrogen adsorption capacity of lithium-modified borohydride is, relative to the total mass of lithium-modified borohydride, in the range of 0.17% to 0.19% by mass at 298 K, 5.0% to 5.3% by mass at 6.1 MPa, and 1.0% to 1.1% by mass at 10 MPa.

[0047] In one embodiment of the present invention, the hydrogen adsorption capacity of lithium-modified borohydride is, relative to the total mass of lithium-modified borohydride, in the range of 0.057% to 0.071% by mass at 77 K, 0.25% to 0.34% by mass at 1.1 MPa, and 2.5% to 3.0% by mass at 11 MPa.

[0048] Therefore, the lithium-modified hydrogen boride of one aspect of the present invention typically has a hydrogen adsorption capacity that is more than 3 times greater than that of hydrogen boride monomer, and thus can be used as a material for hydrogen adsorption.

[0049] One aspect of the present invention provides lithium-modified borohydride that can be manufactured by applying shear force to lithium metal and borohydride and mixing them. "Mixing with shear force" refers to repeatedly compressing and / or stretching the lithium metal and borohydride while they are in contact and / or colliding with each other, thereby breaking them apart and mixing them simultaneously.

[0050] In one aspect of the invention, mixing is carried out in an inert atmosphere, such as an atmosphere of an inert gas, like nitrogen or argon.

[0051] In one aspect of the invention, the mixing is not limited as long as shear force can be applied to the raw materials, and can be carried out, for example, by using a mortar and pestle, a ball mill or other pulverizer.

[0052] In one aspect of the invention, the mixing time is not limited. The mixing time is typically in the range of 20 to 40 minutes, and in one embodiment, it is in the range of 25 to 35 minutes.

[0053] In one aspect of the invention, the mixing temperature is not limited. The mixing temperature is typically in the range of 20°C to 25°C, and in one embodiment, it is in the range of 22°C to 24°C.

[0054] One method for manufacturing lithium-modified hydrogen borate according to the present invention is as follows.

[0055] (1) Physically mix lithium metal with hydrogen boroide to obtain a physical mixture. Here, "physical mixing" means stirring lithium metal with hydrogen boroide, for example, by placing it in a sealed container and shaking it up and down and / or rotating it until it is uniform.

[0056] (2) The above physical mixture is manually ground in an inert gas using an agate mortar. The manual grinding is carried out at the above mixing time and mixing temperature.

[0057] (3) In order to remove adsorbed water, etc., vacuum drying is performed at a temperature of 60°C to 100°C, for example, at 80°C for 16 hours to 48 hours, for example, about 32 hours.

[0058] In one aspect of the invention, lithium-modified borohydride can be readily produced by mechanically and chemically mixing lithium metal and hydrogen borohydride with shear force, thereby ensuring that lithium is not ionized and is uniformly dispersed in hydrogen borohydride at the atomic level.

[0059] The following describes several embodiments related to one aspect of the present invention, but it is not intended to limit the scope of the present invention to the contents shown in these embodiments.

[0060] 1. Preparation of lithium-modified hydrogen borate

[0061] (1) Prepare HB (185.8mg) and metal Li (15.6mg) cut into small pieces with scissors.

[0062] (2) The HB and Li prepared in (1) are manually ground and mixed in a mortar and pestle for 30 minutes at 25°C in a glove box under an argon atmosphere.

[0063] (3) After mixing in (2), a gray product (120.6 mg, also known as "Li / HB") is obtained.

[0064] ICP was determined for the obtained Li / HB ratio. ICP was obtained using a Shimadzu ICPS-8100 ICP analyzer, with the measurement wavelengths for lithium and boron set to 670.785 nm and 249.773 nm, respectively. The results showed that the molar ratio of HB:Li was 1:0.14, and the ICP-based molar ratio was B:Li = 1:0.52 (0.66:0.34).

[0065] 2. Evaluation of lithium-modified hydrogen borate

[0066] 2-1. PCT (P: pressure, C: adsorption, T: temperature) evaluation

[0067] For the Li / HB, HB, and LiB2 manufactured above, the hydrogen adsorption capacity at various pressures was determined using BELSORPHP from Microtrac BEL at 298 K (25 °C) or 77 K. It should be noted that the Li:B molar ratio of LiB2 used as a comparative example was 3:7 in the ICP determination. Each sample underwent pretreatment heating (80 °C, 32 hours for degassing) before the determination. For room temperature (298 K) determinations, the sample tube containing the sample was immersed in a constant temperature bath (298 K). For 77 K determinations, the sample tube was immersed in a Dewar flask filled with liquid nitrogen.

[0068] The results are shown in Figure 2A , Figure 2B .exist Figure 2A , Figure 2B In the study, four determinations of Li / HB were performed at 298 K, and two determinations of HB and LiB2 were performed separately. Two determinations of Li / HB and HB were performed separately at 77 K. According to... Figure 2A , Figure 2B It can be seen that, under temperature conditions of 298K and 77K, the hydrogen adsorption capacity of the obtained Li / HB is more than 3 times higher than that of HB or LiB2 alone without Li modification.

[0069] 2-2. IR Spectral Evaluation

[0070] For Li / HB and HB, IR spectra were determined by total reflectance absorption (ATR) using a Bruker Alpha spectrometer (ALPHA II, manufactured by Bruker, Billerica, MA, USA). Measurements were performed in a glove box under an argon atmosphere at room temperature (25°C), with a total of 16 measurements.

[0071] The results are shown in Figure 3A , Figure 3B .according to Figure 3B It can be seen that the obtained Li / HB ratio is at 1100 cm⁻¹ -1 ~1500cm -1 It has an absorption peak (Iab) within the range.

[0072] The obtained Li / HB absorption peak (Iab) is not a single absorption peak, but two absorption peaks, with the maximum value located at 1300 cm⁻¹. -1 ~1400cm -1The absorption peak (Ia) and maximum value exist in the range of 1200 cm⁻¹. -1 ~1300cm -1 Range (1280cm) -1 The peak is formed by the overlap of the absorption peak (Ib) near the same location.

[0073] The area ratio (Ia / Ib) of the separated absorption peak (Ia) to the absorption peak (Ib) is 0.68.

[0074] It should be noted that, according to Figure 3A In the IR spectrum of HB measured under the same conditions, at 1100 cm⁻¹ -1 ~1500cm -1 An absorption peak was observed in the range, but the maximum value of this absorption peak was observed at 1300 cm⁻¹. -1 ~1400cm -1 A single peak within a range.

[0075] Therefore, it is inferred that peak (Ia) is an absorption peak based on the B-H-B vibration, and peak (Ib) is an absorption peak based on the Li-B vibration.

[0076] Based on the above results, it can be seen that in the obtained Li / HB, lithium is not ionized but is uniformly dispersed in hydrogen borate at the atomic level.

[0077] 2-3. EEM Spectral Evaluation

[0078] For Li / HB and HB, excitation-fluorescence matrix (EEM) spectra were measured using a Duetta fluorescence spectrophotometer (manufactured by Horiba Corporation). Solutions of each sample were prepared by dispersing them in acetonitrile at a concentration of 1 mg / ml, and measurements were performed using 1 cm cuvettes.

[0079] The results are shown in Figure 4A , Figure 4B .according to Figure 4A , Figure 4B It can be seen that the obtained Li / HB does not exhibit luminescence.

[0080] It should be noted that HB exhibits luminescence with a maximum peak around 400 nm when illuminated with light of a wavelength of 332 nm.

[0081] Therefore, since Li / HB does not exhibit luminescence, it can be concluded that Li / HB is a substance with different properties from HB.

[0082] 2-4. TPD Evaluation

[0083] For Li / HB and HB, the amount of hydrogen released from the compounds was determined using a combination of a high-sensitivity differential thermal balance (STA-2500 Regulus, NETZSCH, Tokyo, Japan) and a quadrupole mass spectrometer (Microvision2, MKS Instruments). 10 mg of the sample was weighed into an alumina beaker and heated using the STA-2500 Regulus at a heating rate of 10 K / min. The hydrogen produced during heating was quantified using the Microvision2.

[0084] The results are shown in Figure 5A , Figure 5B .according to Figure 5A , Figure 5B It can be seen that the obtained Li / HB ( Figure 5B ) except in HB ( Figure 5A In addition to the hydrogen release peak observed at 200℃, a hydrogen release peak was also observed near 550℃.

[0085] Based on the TPD determination of Li / HB (10 mg) and the comparison with the standard curve after subtracting the background, it can be seen that Li / HB releases 0.35±0.03 mmol (0.70±0.06 mmol converted to H) of H2.

[0086] Based on the results of ICP and TPD, the molar ratio of H to B to Li in Li / HB can be calculated as follows. First, the molar ratio of B to Li in Li / HB is 0.66:0.34. The total amount of boron and lithium per 10 mg of Li / HB is 10 - 0.70 = 9.3 ± 0.06 mg. Therefore, (B + Li) is 9.3 / (10.8 × 0.66 + 6.9 × 0.34) = 0.98 mmol (calculated based on the atomic weight of B being 10.8 and Li being 6.9). Based on the above, H:B:Li = 0.7:(0.66 × 0.98):(0.34 × 0.98), therefore the molar ratio of H to B to Li in Li / HB is H:B:Li = 1 ± 0.09:0.92 ± 0.09:0.48 ± 0.09.

Claims

1. A lithium-modified hydrogen boride comprising lithium and hydrogen boride, When measuring the IR spectrum using the total internal reflection absorption method, at 1100 cm⁻¹ -1 ~1500cm -1 Absorption peaks were observed within the range of [the observed range]. The absorption peak has a maximum value at 1300 cm⁻¹. -1 ~1400cm -1 The absorption peak Ia and maximum value exist in the range of 1200 cm⁻¹. -1 ~1300cm -1 The peak is formed by the overlap of absorption peaks Ib within the range.

2. The lithium-modified borohydride according to claim 1, wherein, The area ratio of the separated absorption peak Ia to the absorption peak Ib, i.e., Ia / Ib, is in the range of 0.5 to 0.

8.

3. The lithium-modified borohydride according to claim 1 or 2, wherein, The molar ratio of boron to lithium, calculated by ICP, is in the range of 0.8 or higher. The molar ratio of hydrogen to boron calculated by TPD and by ICP, i.e., H / B, is in the range of less than 1.

2.

4. The lithium-modified borohydride according to claim 1 or 2, wherein, The temperature-hydrogen intensity curve obtained by TPD measurement has a hydrogen release peak with the peak located in the range of 500℃ to 600℃.

5. A method for manufacturing lithium-modified borohydride comprising lithium and borohydride, comprising the steps of applying shear force to lithium metal and borohydride and mixing them.

6. The method according to claim 5, wherein, Mixing is carried out using a mortar and pestle under an inactive atmosphere.

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