JP2005095869A - Hydrogen storing material and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storing material which uses a lightweight non-metallic compound, has high performance and can act at low temperature and to provide its production method. <P>SOLUTION: The hydrogen storing material contains at least a nano- structured / organized lithium imide compound precursor complex. The nano- structured / organized lithium imide compound precursor complex is produced by treating a mixture obtained by adding fine powdery lithium hydride to fine powdery lithium amide at a prescribed rate as a starting raw material by a prescribed composite treating method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hydrogen storage material that efficiently stores hydrogen as a raw material for fuel cells and the like, and a method for producing the same.

  Fuel cells have been actively developed as a clean energy source, and have already been put into practical use. As an important technology that supports fuel cell technology, there is a technology for storing hydrogen as a raw material for fuel cells. As storage forms of hydrogen, compression storage by high-pressure cylinders and cooling storage as liquid hydrogen have been proposed, but storage by a hydrogen storage material that is advantageous for distributed storage and transport has attracted attention.

Examples of hydrogen storage materials include rare earth-based, titanium-based, vanadium-based, and magnesium-based metal materials, and light element inorganic compound-based materials such as alanate (eg, NaAlH ₄ ) using a reversible disproportionation reaction. Carbon materials such as materials, carbon nanotubes, and activated carbon are known. Of these, lightweight elemental inorganic compounds and carbon-based materials are promising as lightweight materials, and development of efficient storage technologies using such lightweight materials, specifically hydrogen with a high hydrogen storage rate per unit weight. Development of storage materials, development of hydrogen storage materials with a high hydrogen storage rate per unit volume, development of hydrogen storage materials that exhibit hydrogen absorption / release performance in a low temperature range, development of hydrogen storage materials with good durability, Is desired.

Alanate materials such as NaAlH ₄ and LiAlH ₄ are well known and studied as lightweight hydrogen storage materials. Also, Non-Patent Document 1 reports a hydrogen storage method using lithium nitride represented by the following formula (1). Recently, a hydrogen storage system using lithium nitride represented by the following formula (1) has been reconfirmed and reported in Non-Patent Document 2.
Li ₃ N + 2H ₂ ⇔Li ₂ NH + LiH + H ₂ ⇔LiNH ₂ + 2LiH (1)

According to these documents, absorption of hydrogen by lithium nitride (Li ₃ N) starts from about 100 ° C., and 9.3 mass% hydrogen absorption is confirmed at 255 ° C. for 30 minutes. In addition, the release characteristics of absorbed hydrogen are reported to pass through two steps: 6.3% by mass at a little less than 200 ° C. and 3% by mass at 320 ° C. or higher by slowly heating at a lower temperature rise rate. ing.

That is, the reaction of lithium amide (LiNH ₂ ) and lithium hydride (LiH) represented by the following formula (2) corresponding to the right part of the above formula (1) starts to proceed at a temperature of less than 200 ° C., and the above formula (1) It has been shown that the reaction of lithium imide (Li ₂ NH) and LiH represented by the following formula (3) corresponding to the left side portion of γ begins to proceed at 320 ° C. or higher.
LiNH ₂ + 2LiH → Li ₂ NH + LiH + H ₂ ↑ (2)
Li ₂ NH + LiH → Li ₃ N + H ₂ ↑ (3)

The present inventors pay attention to the reaction system of the above formula (1), and after storing Li ₃ N at a hydrogen pressure of 3 MPa and 200 ° C. by the same method as in the above document, the sample is heated to remove desorbed gas. Got. The emission spectrum characteristic diagram is shown in FIG. Here, the heating rate of the sample was 5 ° C./min. A characteristic line A in FIG. 11 represents a hydrogen emission spectral line, and a characteristic line B in FIG. 11 represents an ammonia gas (NH ₃ (g)) emission spectral line. As is apparent from FIG. 11, the hydrogen release characteristic in the conventional method has a wide temperature range of 200 ° C. to 400 ° C., and has a large peak on the high temperature side (around 320 ° C.).

Thus, although the technique of the above-mentioned document is an effective hydrogen storage method using a light metal compound called lithium nitride, the effective hydrogen storage rate in a low temperature range of about 200 ° C. is small, and high-capacity hydrogen absorption. -In order to implement | achieve discharge | release, there exists a problem that it is necessary to heat to the high temperature range of 320 degreeC or more. Further, in the technique described in the above-mentioned document, heating is performed over a long time by slowing the rate of temperature rise as the peak temperature of hydrogen absorption / release approaches, so it is not highly responsive and practical. is not.
Ruff, O., and Goerges, H., Berichte derDeutschen Chemischen Gesellschaft zu Berlin, Vol. 44, 502-6 (1911) Ping Chen et al., Interaction ofhydrogen with metal nitrides and imides, NATURE Vol.420, 21 NOVEMBER 2002, p302-304

  The present invention has been made in view of such circumstances, and an object thereof is to provide a hydrogen storage material capable of high-efficiency and low-temperature operation using a light non-metallic compound and a method for producing the same.

  According to the present invention, a hydrogen storage material containing at least a nanostructured / organized lithium imide compound precursor complex, wherein the lithium imide compound precursor complex is finely powdered into a fine powder lithium amide as a starting material. Provided is a hydrogen storage material characterized in that it is nanostructured and organized by treating a mixture to which lithium hydride is added in a prescribed ratio by a prescribed composite treatment method.

  Further, according to the present invention, such a method for producing a hydrogen storage material, that is, a mixture obtained by mixing fine powder lithium amide and fine powder lithium hydride as a starting material in a predetermined ratio is processed by a predetermined composite processing method. Thus, there is provided a method for producing a hydrogen storage material, characterized in that a nanostructured and organized lithium imide compound precursor composite is obtained.

  In the present invention, the compounding treatment method includes microscopic collision of the starting material mixture with the grinding medium in an inert gas, hydrogen gas, nitrogen gas atmosphere or a mixed atmosphere thereof. The mechanical milling process which repeats is preferably used. The starting material is a mixture of the finely powdered lithium hydride added in excess to the finely powdered lithium amide at a mixing molar ratio of 1: 1 normal reaction ratio or 20 mass% or less from the normal reaction ratio. Preferably there is.

  The lithium imide compound precursor composite is used as a catalyst for enhancing hydrogen absorption / release capability as B, C, Mn, Fe, Co, Ni, Pt, Pd, Rh, Li, Na, Mg, K, Ir, Nd, Nb, One or more metals selected from the group consisting of La, Ca, V, Ti, Cr, Cu, Zn, Al, Si, Ru, Os, Mo, W, Ta, Zr, In, Hf, and Ag Preferably, the catalyst further contains a simple substance, an alloy or a compound, and such a catalyst is mixed with the finely powdered lithium hydride and the finely powdered lithium amide at the time of the mechanical milling process to form a nanostructured and organized can do. A preferable processing atmosphere pressure in the composite processing method is in the range of 0.1 to 10 MPa.

  ADVANTAGE OF THE INVENTION According to this invention, the hydrogen storage material which can operate | move efficiently and low temperature using a lightweight nonmetallic compound is implement | achieved.

  The hydrogen storage material of the present invention contains at least a nanostructured and organized lithium imide compound precursor complex. The hydrogen storage capacity of metal-based and non-metallic compounds in powder-based hydrogen storage materials is related to the structure and structure of the nanometer scale, and the structure and structure control on the nanometer scale (ie, the nanostructure and structure) High-performance hydrogenation material can be produced by

Such a nanostructured / organized lithium imide compound precursor composite is obtained by adding a mixture of fine powder lithium hydride (LiH) at a predetermined ratio to fine powder lithium amide (LiNH ₂ ) as a starting material. It can manufacture by processing by a composite processing method.

  Here, in the compounding method, a method using a mechanical milling process (hereinafter referred to as “MeM process”) in which a sample is pulverized and mixed using a hard ball, or a jet in which a sample is pulverized and mixed by blowing pressurized gas. A method using a mill or the like can be used. In the present invention, it is most preferable to use MeM treatment for the composite treatment method. This is because, as will be described later, according to the MeM treatment, the mixture of starting materials can be sufficiently nanostructured and organized.

More specifically, this MeM treatment is carried out by putting a raw material and a hard ball called a grinding medium into a closed container, and rolling or mechanically stirring to crush, press contact, and knead the raw material, and have different physical properties from the raw material. It is a method of obtaining the indicated material. More specifically, a mixed powder composed of a plurality of components and a steel ball are put together in a sealed container, and the atmosphere inside the container is reduced to a reducing gas atmosphere or an inert gas (for example, nitrogen (N ₂ ) A helium (He), argon (Ar)) atmosphere or a mixed atmosphere thereof is used, and the sample is kneaded and compounded in a nanometer size by rotating and revolving the container. In such a MeM process, the starting raw material mixture is repeatedly subjected to impact compression force by microscopic collision with the grinding medium, plastically deformed (forged deformation), work-hardened, crushed, flaked, Eventually kneaded.

  In the present specification, “kneading” means that when a mixed sample has a property of being easily plastically deformed, it is crushed, stretched, folded, folded, entangled and split, and further split and entangled. It means that the mixed sample is nanostructured and organized.

In the present invention, starting from LiNH ₂ and LiH, attention was paid to a hydrogen absorption / release reaction using a reversible disproportionation reaction of the following formula (4). That is, a LiNH ₂ and LiH starting material mixture is treated with MeM in a hydrogen atmosphere to prepare a nanostructured and organized lithium imide compound precursor composite, and this is heated to raise the temperature (4) According to the reaction of the formula, lithium imide (Li ₂ NH) is generated, and at the same time, hydrogen is generated.
LiNH ₂ + LiH → Li ₂ NH + H ₂ ↑ (4)

According to this reaction, it is possible to reversibly absorb and release 6.5% by mass of hydrogen in theory. At this time, the standard enthalpy of the hydrogenation reaction is ΔH = −44.5 (kJ / mol H ₂ ), and the absorption and release of hydrogen at a low temperature is expected from the thermodynamic viewpoint.

By making the ratio of LiH to LiNH ₂ in the starting material larger than the normal reaction ratio (referring to the reaction ratio of the above formula (4)), the generation of NH ₃ (g) by the reaction of the following formula (5) is suppressed. It is preferable to suppress.
2LiNH ₂ → Li ₂ NH + NH ₃ (g) ↑ (5)

In this case, the LiH excess addition amount is desirably 20% by mass or less of the normal LiH reaction amount with respect to LiNH ₂ (reaction amount represented by the above formula (4)). That, LiH The total amount of reaction volume normal LiH for LiNH ₂ (100 wt%) it is desirable that the super-120 mass% or less. This is because the amount of excessive addition of LiH for suppressing the generation of NH ₃ (g) is sufficient, and when this amount is exceeded, there is a disadvantage that the effective hydrogen storage rate decreases. . Therefore, the upper limit of LiH excess amount relative LiNH ₂ was set to 20 wt% of the reaction volume of normal LiH in the present invention.

Furthermore, B, C, Mn, Fe, Co, Ni, Pt, Pd, Rh, Li, Na, Mg, K, Ir, Nd, Nb, La, Ca, V, and the starting material (LiNH ₂ and LiH) One or more kinds of simple metals, alloys or compounds selected from the group consisting of Ti, Cr, Cu, Zn, Al, Si, Ru, Os, Mo, W, Ta, Zr, In, Hf, and Ag. It is preferable to add as a catalyst, and thereby the reaction of the above formula (4) can be efficiently advanced. In addition, the hydrogen storage rate per unit weight or per unit volume is increased, and sharp hydrogen absorption / release is possible in a low temperature range, so that good durability can be obtained.

  The amount of such a catalyst added is preferably 0.5 to 5 mol%. When the amount of the catalyst added is less than 0.5 mol%, it becomes difficult to uniformly disperse in the lithium imide compound precursor composite. On the other hand, when the addition amount of the catalyst exceeds 5 mol%, the effective hydrogen storage rate is reduced.

It is preferable that the catalyst is nanostructured and organized by mixing with LiNH ₂ and LiH at the time of producing a lithium imide compound precursor complex by MeM treatment. This is because it is difficult to newly enter the catalyst particles into the nanostructure of the lithium imide compound precursor composite when the catalyst particles are separately added to the composite-treated sample.

  In the composite treatment method, the treatment atmosphere pressure is preferably in the range of 0.1 to 10 MPa, and thereby the hydrogen absorption efficiency can be improved. When the processing atmosphere pressure is lower than atmospheric pressure (0.1 MPa), hydrogen and nitrogen as active components may be lost. On the other hand, the high pressure capability limit of the MeM processing apparatus developed by the present inventors is 10 MPa, and the processing atmosphere pressure exceeding this is not realistic.

After a LiM ₂ and LiH powder mixture as a starting material is subjected to MeM treatment to produce a lithium imide compound precursor composite (that is, after the composite treatment), the lithium imide compound precursor composite is heated to a predetermined temperature range, A reversible disproportionation reaction can be generated by reacting nanostructured / organized LiNH ₂ and LiH to form Li ₂ NH. In this case, the heating temperature for the reversible disproportionation reaction is preferably 250 ° C. or less, and more preferably 200 ° C. or less. In the present specification, “reversible disproportionation reaction” means that the reaction proceeds reversibly and decomposes into a plurality of different components.

  Next, an example of a conventional procedure for producing a hydrogen storage material and an example of a procedure for producing a nanostructured / structured hydrogen storage material by the MeM process performed by the present inventors will be described in comparison examples and examples. This will be described below. Needless to say, the specific method, conditions, and the like of the MeM process are not limited to the examples shown here.

(Comparative Example 1)
Commercially available LiNH ₂ and LiH were weighed at a molecular ratio of 1: 1 and mixed for several minutes in an agate mortar. The mixture thus obtained (that is, the sample according to Comparative Example 1) was heated at a heating rate of 5 ° C./min, and mass number analysis of the desorbed gas accompanying the heating was performed.

FIG. 1 shows a gas emission spectrum diagram representing the mass number analysis result of the desorbed gas accompanying the temperature rise of the sample of Comparative Example 1. In FIG. 1, the horizontal axis represents temperature (° C.), and the vertical axis represents desorption gas mass number (MASS) analysis method (arbitrary unit) as the temperature rises. Further, a characteristic line C in FIG. 1 represents a hydrogen emission spectrum line, and a characteristic line D represents an ammonia gas (NH ₃ (g)) emission spectrum line. As is clear from FIG. 1, in the sample of Comparative Example 1, a large amount of NH ₃ (g) was released simultaneously with the hydrogen release. This is considered to be due to the thermal decomposition reaction of LiNH ₂ shown in the above-described formula (5) (reproduced below).
2LiNH ₂ → Li ₂ NH + NH ₃ (g) ↑ (5)

This result supports that the hydrogen releasing reaction by LiNH ₂ and LiH preferentially occurs when LiNH ₂ and LiH are in microscopic contact. However, when LiNH ₂ and LiH are not in microscopic contact, since the decomposition reaction of formula (5) preferentially proceeds before the reaction of formula (4) proceeds, the heat of LiNH ₂ alone Only the decomposition reaction occurs, and as a result, a large amount of NH ₃ (g) is released.

(Comparative Example 2)
For the purpose of increasing the microscopic contact between LiNH ₂ and LiH and suppressing the release of NH ₃ (g), LiNH ₂ and LiH are weighed at a molecular ratio of 1: 2 for several minutes in an agate mortar. A mixed mixture (sample of Comparative Example 2) was prepared, and the obtained sample was subjected to mass number analysis of the desorbed gas accompanying a temperature increase as in Comparative Example 1.

FIG. 2 shows a gas emission spectrum diagram showing the mass number analysis result of the desorbed gas accompanying the temperature rise of the sample of Comparative Example 2. A characteristic line E in FIG. 2 indicates a hydrogen emission spectral line, and a characteristic line F indicates an NH ₃ (g) emission spectral line. As is clear from FIG. 2, NH ₃ (g) is released simultaneously with hydrogen release in the sample of Comparative Example 2, but compared with Comparative Example 1, the release of NH ₃ (g) is suppressed. It has been found. From this result, in the hydrogen storage system in the present reaction system (the above reaction formula (4)), it was found that the nanoscale structure is a parameter that largely governs the hydrogen absorption / release characteristics.

(Example 1)
For the purpose of achieving microscopic contact where LiNH ₂ and LiH overlap, LiNH ₂ fine powder and LiH fine powder were weighed at a molecular ratio of 1: 1, and MeM treatment was performed for 2 hours. As the LiNH ₂ fine powder and LiH fine powder, reagents having an average particle diameter of several tens of μm (20 to 40 μm) were used.

Specifically, in the MeM treatment, a powder of a mixed powder sample LiNH ₂ and LiH mixed at a ratio of 1: 1 in a steel pot (internal volume 30 cc) and a small amount of catalyst 0.3 grams. , 20 steel balls (diameter 7 mm) were charged, the inside of the container was made an atmosphere of a reducing gas such as hydrogen or an inert gas such as argon (Ar), and rotated and revolved at a rotational speed of 400 rpm. The sample was kneaded to obtain nanometer-sized powder particles having a size of several microns in which LiNH ₂ and LiH were combined. As the MeM processing apparatus, a P7-planet type ball mill manufactured by Fritsch of Germany was used.

  Here, the microscopic effect of the MeM process will be described with reference to FIGS. The mixed sample sealed in the sealed container is subjected to impact compression force by repeatedly colliding with a hard steel ball (grinding medium), undergoes plastic deformation (forging deformation), work hardens, is pulverized, sliced, Eventually they are kneaded. Such kneading of the mixed sample proceeds in stages as follows.

  In the initial stage of kneading, the sample particles 502 are sandwiched between the steel balls 504 and 504 in the dispersed particles 503 as shown in FIG. In the middle stage of kneading, as shown in FIG. 4, the sample particles 502 are further crushed, stretched, thinned and laminated. Further, when reaching the later stage of kneading, as shown in FIG. 5, the sample particles 502 are folded and folded in a state where they are laminated in a thin piece, and fractured to show a fracture surface 502a, so that a so-called kneading effect is recognized. become. In this way, mixed powder particles having a size of several microns are obtained which are nanostructured and organized.

About the mixture obtained by such MeM process, the mass number analysis of the desorption gas accompanying a temperature rise was performed similarly to the said Comparative Examples 1 and 2. FIG. FIG. 6 shows a gas emission spectrum diagram showing the mass number analysis result of the desorbed gas accompanying the temperature rise of the sample of Example 1. The characteristic line G in FIG. 6 represents the hydrogen emission spectrum line, and the characteristic line H represents the NH ₃ (g) emission spectrum line.

As is clear from FIG. 6, the sample of Example 1 has remarkably suppressed NH ₃ (g) release compared to Comparative Examples 1 and 2 mixed in the above-described agate mortar. That is, it has been found that the MeM treatment plays a very effective and important role in the hydrogen storage system utilizing the disproportionation reaction of the above formula (4). However, the release of NH ₃ (g) is still observed.

(Example 2)
Then, the manufacturing method of the hydrogen storage material which added the metal particle as a catalyst is demonstrated. By using the MeM treatment, it is possible to easily add a catalyst that increases the reaction rate of hydrogen absorption / release. A sample obtained by mixing 1 mol% of Ni particles with respect to the number of moles of Li into a mixture of LiNH ₂ and LiH mixed at a molar ratio of 1: 1 and performing the same MeM treatment as in Example 1 above. did. At this time, both LiNH ₂ fine powder and LiH fine powder having an average particle diameter of several tens of μm were used. Further, Ni nanoparticles having an average particle diameter of 20 nm were used as Ni particles.

The obtained sample was subjected to mass analysis of the desorbed gas accompanying the temperature increase in the same manner as in Example 1 above. FIG. 7 shows a gas emission spectrum diagram representing the mass number analysis result of the desorbed gas accompanying the temperature increase of the sample of Example 2. In FIG. 7, a characteristic line indicated by a solid line indicates a hydrogen emission spectral line, and a characteristic line indicated by a broken line indicates an NH ₃ (g) emission spectral line.

As is clear from comparison between FIG. 6 and FIG. 7, it can be seen that the hydrogen emission spectrum is sharpened by adding the catalyst. Further, in the sample according to Example 2, hydrogen release was almost completed between 150 ° C. and 300 ° C. at a temperature rising rate of 5 ° C./min, and NH ₃ (g) was released between 300 ° C. and 400 ° C. The hydrogen emission accompanied by the hydrogen emission spectrum was observed, but the peak height of the NH ₃ (g) emission spectrum relative to the peak height of the hydrogen emission spectrum was lower than that of Example 1. . That is, it can be seen that the generation of NH ₃ (g) is suppressed.

(Example 3)
Then, the manufacturing method of the hydrogen storage material which added the metal compound particle catalyst is demonstrated. Again, by using the MeM treatment, it is possible to easily add a catalyst that increases the reaction rate of hydrogen absorption / release. 1 mol% of titanium trichloride (TiCl ₃ ) particles (average particle diameter: 2 to 4 μm) with respect to the number of moles of Li are mixed in a mixture of LiNH ₂ and LiH mixed at a molecular ratio of 1: 1. A sample subjected to the same MeM treatment as in Example 1 was prepared.

The obtained sample was subjected to mass analysis of the desorbed gas accompanying the temperature increase in the same manner as in Example 1 above. FIG. 8 shows a gas emission spectrum diagram showing the result of mass number analysis of the desorbed gas accompanying the temperature increase in Example 3. In FIG. 8, a characteristic line J indicated by a solid line indicates a hydrogen emission spectral line, and a characteristic line K indicated by a broken line indicates an NH ₃ (g) emission spectral line. As is clear from comparison between FIG. 6 and FIG. 8, it can be seen that the hydrogen emission spectrum is sharpened by adding the catalyst. Further, at a rate of temperature increase of 5 ° C. per minute, hydrogen release was completed between 150 ° C. and 300 ° C., and NH ₃ (g) release was not measured at all during the measurement.

When TiCl ₃ is added, it is presumed that TiCl ₃ is decomposed by the subsequent heating of the hydrogen storage material and exists in the lithium imide compound precursor composite in the form of metallic titanium Ti.

(Cycle test and its evaluation results)
Subsequently, the cycle characteristics of the lithium imide compound precursor composite containing TiCl ₃ as a catalyst will be described. A sample obtained by mixing 1 mol% of TiCl ₃ particles with respect to the number of moles of Li into a mixture of LiNH ₂ and LiH mixed at a molecular ratio of 1: 1 and performing the MeM treatment in the same manner as in Example 1. One cycle sample is used. Then, the first cycle sample was vacuum degassed at 220 ° C. for 12 hours, and then the sample obtained by reacting with hydrogen under 180 ° C. and 3 MPa hydrogen pressure for 12 hours was used as the second cycle sample. A sample obtained by performing the same treatment once more was used as a third cycle sample.

  FIG. 9 shows a gas emission spectrum line representing the result of the temperature-programmed desorption gas analysis of the three types of samples thus obtained and a mass loss line representing the result of thermogravimetry. The characteristic line P1 in FIG. 9 shows the gas emission spectral line of the first cycle sample, the characteristic line Q1 shows the gas emission spectral line of the second cycle sample, and the characteristic line R1 shows the gas emission spectral line of the third cycle sample. ing. Further, the characteristic line P2 in FIG. 9 represents the mass loss line of the first cycle sample, the characteristic line Q2 represents the mass loss line of the second cycle sample, and the characteristic line R2 represents the mass loss line of the third cycle sample. Yes.

  As is clear from FIG. 9, the second and third cycle samples show some deterioration in characteristics in terms of the hydrogen release temperature and the hydrogen release amount as compared with the first cycle sample. This is considered to be because the impurities (which are supposed to be mixed into the additive (catalyst) or the raw material from the beginning have become stable substances that are not involved in the storage and release of hydrogen in the first temperature rising process. However, since there is no significant difference between the second cycle sample and the third cycle sample, it is considered that the cycle characteristics are very good. Furthermore, when desorption gas analysis was performed at a heating rate of 1 ° C./min, the peak position of the desorption curve decreased to 200 ° C. or lower, and it was confirmed that hydrogen storage and release at 200 ° C. or lower is possible. .

  Although all the hydrogen storage experiments described above were performed under a pressure condition of about 3 MPa, it is of course possible to carry out under a wide range of pressure conditions of about 1 to 10 MPa from the viewpoint of improving the hydrogen absorption efficiency. It is.

The improvement of hydrogen release characteristics (sharpening of the emission spectrum, lowering of the emission temperature) by the addition of such a catalyst is not unique to the Ni particles and TiCl ₃ particles, and elements having the same catalytic action, for example, B, C, Mn, Fe, Co, Ni, Pt, Pd, Rh, Li, Na, Mg, K, Ir, Nd, Nb, La, Ca, V, Ti, Cr, Cu, Zn, Al, Si , Ru, Os, Mo, W, Ta, Zr, In, Hf, and Ag. Next, the embodiment will be described.

(Examples 4 to 26)
Example 4 is composed of LiH and LiNH ₂ as in Example 1, but the test method is different as described below. The examples 5 to 26, in the same manner as in Example 2, but in which the addition of various catalysts in LiH and LiNH _2, as follows, test methods differ. As shown in Table 1 below, in Examples 5 to 23, LiH, LiNH ₂ , and various catalysts were in a molar ratio of 1: 1: 0.01, and high purity so that the total amount thereof was 1.3 g. Weighed in an Ar glove box. In Example 24, as shown in Table 1, LiH, LiNH ₂ , chromium chloride (CrCl ₃ ), and TiCl ₃ were used at a molar ratio of 1: 1: 0.01: 0.01, and the total amount thereof. Was weighed in a high purity Ar glove box so as to be 1.3 g. Further, for Example 25 and Example 26, as shown in Table 1, the molar ratio of LiH, LiNH ₂ and a predetermined catalyst was 1.2: 1: 0.01, and the total amount thereof was 1.3 g. Weighed in a high purity Ar glove box.

Next, the weighed sample was put into a high-chromium steel valve-equipped mill container (250 cm ³ ) in a high-purity Ar glove box. Subsequently, after evacuating the inside of the mill container, high purity Ar was introduced into the mill container so that the inside of the mill container became 1 MPa, and a planetary ball mill apparatus (manufactured by Fritsch, P5) was used. Milling was performed at 250 rpm for 120 minutes to prepare a sample. After the inside of the mill container was evacuated and filled with Ar, the mill container was opened in a high purity Ar glove box, and a sample was taken out. Metal Ni, metal Co, and metal Fe are samples manufactured by Vacuum Metallurgical Co., Ltd. (Ni: average particle size 20 nm, BET specific surface area: 43.8 m ² / g, Co: average particle size 20 nm, BET specific surface area: 47 0.9 m ² / g, Fe: average particle diameter 20 nm, BET specific surface area: 46.0 m ² / g). All other metal chlorides manufactured by Aldrich (purity 95% or more) were used.

500 mg of each of the samples of Examples 4 to 26 was weighed in a high-purity Ar glove box and filled into a SUS reaction vessel (internal volume: about 50 cm ³ ) with an internal volume of 50 cm ^{3 and} a valve. Note that a thermocouple is attached to the reaction vessel so that the temperature near the top of the sample can be measured. The reaction vessel filled with this sample is attached to an experimental apparatus (internal volume: about 300 cm ³ ) attached with a pressure sensor, a vacuum pump and a gas chromatograph (manufactured by Shimadzu Corp., GC9A, TCD detector, column: Molecular Sieve 5A). After mounting and evacuating, the sample is heated from room temperature to 300 ° C. at a heating rate of 10 ° C./min, and the gas released in the reaction vessel at room temperature, 150 ° C., 200 ° C. and 250 ° C. is attached to the attached gas chromatograph. The amount of hydrogen was measured. The hydrogen release rate in each temperature range was a value obtained by dividing the hydrogen amount measured in each temperature range by the sample amount before heating. The hydrogen release rate was corrected by calculating the amount of hydrogen that had been collected and lost in the gas chromatograph at each temperature.

  FIG. 10 shows the hydrogen release rate released at a temperature rising rate of 10 ° C./min and released in the temperature ranges of room temperature to 150 ° C., room temperature to 200 ° C., and room temperature to 250 ° C. In addition, when it hold | maintains at each temperature, it generally improves from the hydrogen release rate obtained by temperature rising. As shown in FIG. 10, each sample except Example 7, Example 13, and Example 15 showed a hydrogen release rate of about 1 mass% at a temperature rise of room temperature to 250 ° C. Release characteristics were shown. In Example 15, the hydrogen release rate from room temperature to 200 ° C. exceeds 0.4 mass%, indicating a high hydrogen release rate in a relatively low temperature region. In Example 7 and Example 13, the hydrogen release rate in the low temperature region from room temperature to 150 ° C. exceeded 0.4 mass%, and a high hydrogen release rate was shown in the low temperature region of 150 ° C. or less.

  The hydrogen storage material according to the present invention can be suitably used for a fuel cell that generates power using hydrogen and oxygen as fuel, and more specifically, includes automobiles, domestic power generation, vending machines, mobile phones, and notebook computers. It can be used in a wide range of technical fields as a power source for cordless home appliances or self-supporting robots / micromachines.

FIG. 6 is a gas emission spectrum diagram showing a mass number analysis result of desorbed gas accompanying a temperature increase in Comparative Example 1. The gas emission spectrum diagram showing the mass number analysis result of the desorption gas accompanying the temperature rise of Comparative Example 2. The expanded cross-sectional schematic diagram which shows the initial kneading | mixing state of MeM process. The expanded cross-sectional schematic diagram which shows the kneading | mixing state of the middle stage of MeM process. The expanded cross-sectional schematic diagram which shows the kneading | mixing state of the latter stage of MeM process. 2 is a gas emission spectrum diagram showing the result of mass number analysis of desorbed gas accompanying the temperature increase in Example 1. FIG. FIG. 6 is a gas emission spectrum diagram showing the result of mass spectrometry of desorbed gas accompanying the temperature increase in Example 2. FIG. 6 is a gas emission spectrum diagram showing the result of mass spectrometry of desorbed gas accompanying a temperature increase in Example 3. The characteristic line figure showing the change of the amount of mass loss at the time of a gas emission spectrum line and temperature rise when hydrogen discharge | release and hydrogen storage are repeated with the hydrogen storage material which concerns on this invention. The graph which shows the hydrogen release rate in the predetermined | prescribed temperature range of each sample of Examples 4-26. Gas emission spectrum diagram of the desorbed gas in the conventional lithium nitride (Li 3 _N) in the hydrogen storage material as a starting material.

Explanation of symbols

502; Sample particle 502a; Fracture surface 503; Dispersed particle 504; Steel ball

Claims (10)

A hydrogen storage material containing at least a nanostructured / organized lithium imide compound precursor complex,
The lithium imide compound precursor composite was nanostructured and organized by treating a mixture of fine powder lithium amide added to fine powder lithium amide at a predetermined ratio as a starting material by a predetermined composite processing method. A hydrogen storage material characterized by being a thing.   As the composite treatment method, mechanical milling in which microscopic collision of the starting material mixture with the grinding medium is repeated in an atmosphere of any of inert gas, hydrogen gas, nitrogen gas, or a mixed atmosphere thereof. The hydrogen storage material according to claim 1, wherein treatment is used.   The starting material is obtained by adding the fine powder lithium hydride to the fine powder lithium amide in an excess of a mixing molar ratio of 1: 1 normal reaction ratio or 20 mass% or less from the normal reaction ratio. The hydrogen storage material according to claim 1 or 2, wherein The lithium imide compound precursor composite is used as a catalyst for enhancing hydrogen absorption / release capability as B, C, Mn, Fe, Co, Ni, Pt, Pd, Rh, Li, Na, Mg, K, Ir, Nd, Nb, One or more metals selected from the group consisting of La, Ca, V, Ti, Cr, Cu, Zn, Al, Si, Ru, Os, Mo, W, Ta, Zr, In, Hf, and Ag Further comprising a simple substance, an alloy or a compound;
4. The catalyst according to claim 2, wherein the catalyst is mixed with the fine powder lithium hydride and the fine powder lithium amide at the time of the mechanical milling process, and is nanostructured and organized. The hydrogen storage material as described.   The hydrogen storage material according to any one of claims 2 to 4, wherein a treatment atmosphere pressure in the composite treatment method is in a range of 0.1 to 10 MPa.   By treating a mixture of finely powdered lithium amide and finely powdered lithium hydride as a starting material in a predetermined ratio by a predetermined composite processing method, a nanostructured and organized lithium imide compound precursor composite is obtained. A method for producing a hydrogen storage material, characterized by comprising:   As the composite treatment method, mechanical milling in which microscopic collision of the starting material mixture with the grinding medium is repeated in an atmosphere of any of inert gas, hydrogen gas, nitrogen gas, or a mixed atmosphere thereof. The method for producing a hydrogen storage material according to claim 6, wherein treatment is used.   The fine powder lithium hydride is added in excess to the fine powder lithium amide in a mixture molar ratio of 1: 1 normal reaction ratio or 20 mass% or less from the normal reaction ratio. The method for producing a hydrogen storage material according to claim 7.   B, C, Mn, Fe, Co, Ni, Pt, Pd, Rh, Li, Na, Mg, K, Ir, Nd, Nb, La, Ca, V, Ti, Cr, Cu, Zn, Al, Si, Ru, Os, Mo, W, Ta, Zr, In, Hf, Ag selected from the group consisting of one or more kinds of simple metals, alloys or The compound is further added, and the catalyst is nanostructured and organized together with the fine powder lithium hydride and the fine powder lithium amide during the mechanical milling treatment. A method for producing a hydrogen storage material.   The method for producing a hydrogen storage material according to any one of claims 7 to 9, wherein a treatment atmosphere pressure in the composite treatment method is in a range of 0.1 to 10 MPa.

Images