JP2009011899A - Hydrogen occluding material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen occluding material which efficiently occludes hydrogen gas, is light in weight and is excellent in chemical stability. <P>SOLUTION: The hydrogen occluding material comprises a porous substrate made of a microporous amorphous metal oxide, and hydrogen occluding metal nanoparticles dispersed in the porous substrate. Preferably, the metal oxide is made of at least one kind selected from alumina and silica-alumina, and the hydrogen occluding metal nanoparticle is made of a group 8 element. In the hydrogen occluding material, the hydrogen occluding metal nanoparticle is dispersed in the microporous amorphous metal oxide to form a complex. The hydrogen occluding material is widely used in a field using the storage and transportation of hydrogen gas, such as a fuel cell and the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrogen storage material and a method for producing the same, and more particularly, the present invention relates to a metal-added amorphous metal oxide hydrogen storage material that is lightweight and excellent in chemical stability, and a method for producing the same. is there.

In recent years, there has been a strong interest in the construction of an environmentally low-load energy system that uses hydrogen, which is attracting attention as a clean energy, and expectations for the establishment and practical application of high-efficiency fuel cell system technology using hydrogen as fuel. Is growing. In order to store and transport hydrogen as a fuel, conventionally, storage using compressed hydrogen gas and transportation using a high-pressure cylinder are performed. However, the cylinder is heavy. On the other hand, when hydrogen as fuel is stored and transported as liquid hydrogen, since the density of liquid hydrogen is 70.8 kg / m ³ , the volume is 1/850 that of hydrogen gas, and the liquid has a high weight energy density. Hydrogen is more compact than compressed hydrogen. However, liquefaction of hydrogen requires a lot of power and cost, and there are problems such as leakage.
Further, hydrogen storage alloys such as LaNi ₅ and TiFe (see Patent Document 1) are alloys that reversibly absorb and release a large amount of hydrogen, and the alloy reacts with hydrogen gas. However, the hydrogen storage alloy may crack during the hydrogenation process, and may be pulverized due to repeated absorption and release of hydrogen. Moreover, since it is a metal, there is a problem that the weight is large, and further, the hydrogen storage alloy is expensive, so that the equipment cost is increased.

JP 09-0255529 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hydrogen storage material that is lightweight and inexpensive, and further excellent in chemical stability, and a method for producing the same.

The present invention is as follows.
[1] A composite comprising a porous substrate composed of a microporous amorphous metal oxide and hydrogen storage metal nanoparticles dispersed in the porous substrate, wherein the metal oxide includes silica, alumina and silica- A hydrogen storage material comprising at least one selected from alumina.
[2] The hydrogen storage material according to [1], wherein the metal element constituting the hydrogen storage metal nanoparticles is nickel and / or cobalt.
[3] The hydrogen storage material according to [1] or [2], wherein an average particle diameter of the hydrogen storage metal nanoparticles is 0.1 to 10 nm.
[4] The composition ratio between the metal (I) in the metal oxide constituting the composite and the metal (M) in the hydrogen storage metal nanoparticles is 0.1 in terms of M / (I + M) in terms of molar ratio. The hydrogen storage material according to any one of [1] to [3], which is ˜0.5.
[5] The composition ratio of the metal (I) in the metal oxide composing the composite to the metal (M) in the hydrogen storage metal nanoparticles is 0.15 in terms of molar ratio in terms of M / (I + M). The hydrogen storage material in any one of said [1] thru | or [4] which are -0.35.
[6] A method for producing a hydrogen storage material according to any one of [1] to [5] above, wherein a precursor solution is prepared by dissolving a metal alkoxy compound and a metal salt in an organic solvent. A solution preparation step, a precursor formation step of concentrating the precursor solution or distilling off the organic solvent to synthesize the precursor, and heating the precursor to form hydrogen-absorbing metal nanoparticle in the porous substrate skeleton. And a heat treatment step of forming a composite in which particles are dispersed.
[7] The method for producing a hydrogen storage material according to [6], wherein hydrogen peroxide is further added in the precursor solution preparation step.
[8] The method for producing a hydrogen storage material according to [6] or [7], wherein the heat treatment step includes an air firing step and a reduction treatment step.
[9] The method for producing a hydrogen storage material according to any one of [6] to [8], wherein the metal alkoxy compound is Si (OR ¹ ) ₄ .
(However, R ¹ is an alkyl group having 1 to 4 carbon atoms, and R ¹ may be the same or different from each other.)
[10] The method for producing a hydrogen storage material according to [9], wherein the alkyl group of R ¹ is at least one selected from a methyl group, an ethyl group, and a propyl group.
[11] The method for producing a hydrogen storage material according to any one of [8] to [10], wherein the air baking step is baking at a temperature of 400 to 1100 ° C. in the air.
[12] The method for producing a hydrogen storage material according to any one of [8] to [11], wherein the reduction treatment step is performed at a temperature of 300 to 700 ° C. while hydrogen gas is flowing.

  According to the metal-added amorphous metal oxide hydrogen storage material of the present invention, the hydrogen storage metal nanoparticles form a composite dispersed in the microporous amorphous metal oxide, and hydrogen is absorbed by the dispersed hydrogen storage metal nanoparticles. It can be occluded efficiently.

According to the method for producing a metal-added amorphous metal oxide hydrogen storage material of the present invention, a hydrogen storage metal nanoparticle having an average particle size of nanometer order is a composite dispersed in a microporous amorphous metal oxide. Can be formed.
Moreover, according to the manufacturing method of the metal addition amorphous metal oxide hydrogen storage material of this invention, the magnitude | size of the particle diameter of the hydrogen storage metal nanoparticle disperse | distributed in a hydrogen storage material can also be adjusted.

The present invention will be described in detail below.
[1] Hydrogen storage material The hydrogen storage material of the present invention comprises a composite comprising a porous substrate made of a microporous amorphous metal oxide and hydrogen storage metal nanoparticles dispersed in the porous substrate, The metal oxide is characterized by comprising at least one selected from silica, alumina, and silica-alumina.

  The above porous substrate made of microporous amorphous metal oxide (hereinafter also simply referred to as “porous substrate”) has a three-dimensional network structure. This porous substrate has a large number of pores penetrating in a mesh shape, and the communication path has a three-dimensional network structure.

The pores of the “porous substrate” have a micro diameter and are usually 2 nm or less. The average diameter of the pores of this porous substrate is not particularly limited, but is preferably 0.1 to 2 nm, more preferably 0.1 to 1 nm, still more preferably 0.1 to 0.4 nm, and particularly preferably Is 0.3 to 0.4 nm. Since the molecular diameter of hydrogen is 0.289 nm, when the average pore diameter is 0.3 nm, gases having a molecular diameter larger than 0.30 nm, such as N ₂ , Ar, and CO gas, cannot pass through. From this, hydrogen can be selected by the molecular sieve effect.

  The “metal oxide” is alumina, silica, or silica-alumina. Of these, silica is preferable.

The metal constituting the “hydrogen storage metal nanoparticles” is not particularly limited as long as it has a hydrogen storage capability, but is preferably a transition metal, and among these, in particular, Group 8 such as Co, Ni, Pd, Ru, Rh, etc. Elements are preferred, and among these, Co and Ni are more preferred. Moreover, 1 type may be sufficient as the metal to disperse | distribute, and 2 or more types of combinations may be sufficient as it.
In addition, although this metal nanoparticle consists only of a metal normally, it may contain the trace amount of the metal oxide.

  The particle size of the hydrogen storage metal nanoparticles is not particularly limited as long as it is a nanoparticle size, but the average particle size of the metal particles is preferably 0.1 to 20 nm, more preferably 0.1 to 15 nm, and still more preferably 0. .1 to 10 nm.

  The hydrogen storage metal nanoparticles may be dispersed in any way, but it is preferable that the hydrogen storage metal nanoparticles are uniformly dispersed in the porous substrate. Note that a large amount of hydrogen storage metal nanoparticles may be dispersedly disposed on the surface side of the porous substrate.

  The composition ratio M / (I + M) of the metal (I) in the metal oxide and the metal (M) in the hydrogen storage metal nanoparticles forming the composite of the hydrogen storage material of the present invention is not particularly limited, but preferably Is 0.1 to 1, more preferably 0.1 to 0.5, and still more preferably 0.15 to 0.35. Moreover, when the metal which comprises the said hydrogen storage metal nanoparticle is Ni, 0.15-0.30 is especially preferable, and when Co is 0.2-0.35, it is especially preferable. The composition ratio M / (I + M) is a molar ratio.

The shape of the hydrogen storage material is not particularly limited. Depending on the purpose and application, etc., crushed products, powders, granulated products (spherical, columnar, etc.), plates (flat plates, curved plates, etc.), cylinders (cylinders, rectangular tubes, etc.), rods, various types And a film formed on the support.
The size is also selected according to the purpose, application, and the like.

[2] Method for Producing Hydrogen Storage Material The method for producing a hydrogen storage material according to the present invention is a method for producing the above hydrogen storage material, wherein a metal alkoxy compound and a metal salt are dissolved in an organic solvent, and a precursor solution is prepared. A precursor solution preparation step to be prepared, a precursor formation step for synthesizing a precursor by concentrating the precursor solution or distilling off the organic solvent, and heating the precursor, into the porous substrate skeleton. And a heat treatment step of forming a composite in which hydrogen storage metal nanoparticles are dispersed.

[1] Precursor solution preparation step A precursor solution is prepared by dissolving a metal alkoxy compound and a metal salt containing the predetermined metal element in an organic solvent.
When silica is used as a constituent material of the porous substrate, an alkoxysilane compound given by the following general formula is preferable, and more preferably, the following alkyl group is a methyl group, an ethyl group, or a propyl group (particularly an isopropyl group), More preferably, it is an ethyl group.
Si (OR ¹ ) ₄ (However, R ^{1 in} the formula represents an alkyl group having 1 to 4 carbon atoms, and R ¹ may be the same as or different from each other.)
When alumina is used as the constituent material of the porous substrate, an alkoxyaluminum compound given by the following general formula is preferable, and more preferably, the following alkyl group is a methyl group, an ethyl group or a propyl group (particularly an isopropyl group). More preferably an isopropyl group.
Al (OR ² ) ₃ (wherein R ² represents an alkyl group having 1 to 4 carbon atoms, and R ² may be the same as or different from each other).
When silica-alumina is used as the constituent material of the porous substrate, an Al—O—Si composite alkoxide can be used, and a mixture of the Si (OR ¹ ) ₄ and the Al (OR ² ) ₃ . Etc. can be used.

The metal constituting the metal salt is a metal constituting the hydrogen-absorbing metal nanoparticle, and a transition metal is preferable, and among these, elements of Group 8 such as Co, Ni, Pd, Ru, and Rh are particularly preferable. Of these, Co and Ni are more preferable.
Moreover, as said metal salt, nitrate, acetate, etc. are mentioned, However, Preferably it is nitrate. The metal salt may be a hydrate salt or an anhydrous salt.
Specifically, Ni (NO ₃ ) ₂ , Co (NO ₃ ) _3, or a hydrate thereof can be used. These metal salts can be used alone or in combination of two or more.
The content ratios of the metal alkoxy compound and the metal salt contained in the precursor solution are adjusted so as to obtain the desired composition ratio of the hydrogen storage material in the molar composition ratio.

  The organic solvent is not particularly limited as long as it is an organic solvent that dissolves a metal salt, but is preferably a water-soluble alcohol having 1 to 4 carbon atoms, more preferably methanol, ethanol, propyl alcohol (particularly isopropyl alcohol). It is. The content of the organic solvent is preferably 1 to 20 mol / l, more preferably 1 to 15 mol / l.

The precursor solution can contain a catalyst for polymerizing the metal alkoxy compound. The catalyst is one that dissolves in the organic solvent to be used, and includes hydrogen peroxide. The content thereof is preferably 1 to 30 times mol, more preferably 5 to 20 times mol, and still more preferably 5 to 15 times mol with respect to the content (mol) of the metal alkoxy compound. By using this hydrogen peroxide, a uniform and stable precursor solution can be obtained.
At this time, usually, water is added to form a skeleton by polymerizing the metal alkoxide. And, it is considered that metal ions are disposed and held inside this skeleton.

A predetermined amount of the above ingredients are mixed and mixed. The mixing method is not particularly limited, but is usually mixed by stirring. Although this mixing temperature is not specifically limited, Usually, it is -5-30 degreeC, Preferably it is -5-20 degreeC.
A uniform precursor solution can be obtained by stirring at a temperature in the above range for 1 to 3 hours.

[2] Precursor forming step A precursor is formed by a precursor forming step of concentrating the precursor solution or distilling off the organic solvent. This precursor forming step is usually performed in an air atmosphere. The heating temperature in a precursor formation process is 30-100 degreeC normally, Preferably it is 40-80 degreeC, More preferably, it is 50-70 degreeC. The heating time in the precursor forming step is usually 1 to 10 days, preferably 4 to 9 days, and more preferably 5 to 8 days. In addition, in this precursor formation step, it is considered that the metal alkoxide is polymerized together with the concentration of the precursor solution or the evaporation of the organic solvent to obtain a polymer having a Si—O—Si bond.

[3] Heat treatment step The composite is formed by heating the precursor. This heat treatment step only needs to reduce the metal salt to fine metal particles, and usually includes an air firing step and a reduction treatment step in this order.

(1) Atmospheric calcination step In this step, when an alkoxy group is eliminated from a metal alkoxide and the metal is I, a three-dimensional network skeleton of an IO bond is formed. Further, in the case of metal nitrates, NO- ^{and the} like are eliminated from nitrate ions, and metal oxides are formed from most metal nitrates. This air baking step is usually performed in an air atmosphere. The heating temperature for the firing is usually 400 to 1100 ° C, preferably 500 to 700 ° C, more preferably 550 to 650 ° C. By performing heat treatment in this range, the skeleton can be formed efficiently. When the temperature is lower than 400 ° C., the generation of pores is incomplete, while when it exceeds 1100 ° C., crystallization tends to occur. The heating time is 1 to 8 hours, preferably 1 to 5 hours, preferably 2 to 4 hours.
Further, in this atmospheric firing step, the elimination of CO ₂ from the alkoxy group of the metal alkoxy compound and the elimination of NO from the metal salt (nitrate) are simultaneously performed at substantially the same temperature (see FIGS. 1 and 2). ), The I-O skeleton is rearranged and formed, and at the same time, a fine oxide of a hydrogen storage metal is generated and is well dispersed and held in the skeleton.

(2) Reduction treatment step After the atmospheric firing step, a reduction treatment step is further provided. By this step, the metal component of the hydrogen storage metal can be reduced to metal. The reducing atmosphere in this reduction treatment step can be an atmosphere containing hydrogen in an inert gas (such as nitrogen or argon) or an atmosphere made of hydrogen, and the latter atmosphere is usually used. Moreover, this atmosphere may be distribute | circulated reducing atmosphere gas and does not need to distribute | circulate.
The heating temperature in this reduction treatment step is usually 300 to 800 ° C, preferably 400 to 600 ° C, more preferably 450 to 550 ° C. The heating time is 5 to 30 hours, preferably 10 to 20 hours, and more preferably 12 to 18 hours.
In addition, even if it does not pass through two processes of an atmospheric baking and a reduction process in this way, depending on the metal used, the above-mentioned two processes are unnecessary when only a high temperature heating produces | generates a metal microparticle.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
(1) Production of Ni-microporous amorphous silica composite hydrogen storage material Si (OC ₂ H ₅ ) ₄ (TEOS) and Ni (NO ₃ ) ₂ · 6H ₂ O are dissolved in ethanol, and 30% by mass Hydrogen peroxide water was added to prepare a mixed solution. The mixed solution was prepared so that the Ni / (Si + Ni) composition ratio (hereinafter also simply referred to as Ni composition ratio) was 0.1, 0.2, 0.33, and 0.5. Table 1 shows the composition of each composition ratio. In addition, 2-6 mol, preferably 3-5 mol of water is added to 1 mol of hydrogen peroxide.
Then, the uniform precursor solution was obtained by stirring the mixed solution of each composition ratio in ice-cooling for about 2 hours.
The precursor solution was heat-treated at a temperature of about 60 ° C. for about 1 week in an air atmosphere. And the precursor solution was concentrated etc. and the precursor (a) was obtained.

The precursor (a) obtained above was calcined at a temperature of about 600 ° C. for about 3 hours in an air atmosphere to obtain a powder (b). Then, the reduction process of powder (b) was performed. The reduction treatment was performed by reduction firing in which the powder (b) was fired in a hydrogen stream at a temperature of about 500 ° C. for about 15 hours.
From the above, a Ni-microporous amorphous silica composite hydrogen storage material was obtained.

(2) TG-DTA-Mass spectrum result About the said precursor (a) sample of Ni composition ratio 0.1, TG-DTA is shown in FIG. 1, and a Mass spectrum is shown in FIG.
From FIG. 1, an endothermic peak is observed with DTA at about 300 ° C., and a mass = 30 fragment is desorbed from the mass spectrum measurement of FIG. It was confirmed that the accompanying desorption of NO was progressing. At the same time, since the fragment of Mass ₂ of CO ₂ is desorbed, it can be seen that desorption of the ethoxy group of the Si—Ni—O complex portion is also progressing.
From the above, the elimination of ethoxy groups and NO groups simultaneously results in the reconstruction of the silica network and the uniform precipitation of NiO particles in the silica. As a result, NiO nanoparticle-dispersed amorphous silica can be synthesized. It is thought.

(3) XRD spectrum results before and after reduction treatment Next, XRD measurement (Rigaku Rint 2000) of the powder (b) was performed. The measured XRD spectrum is shown in FIG. Amorphous silica and NiO were produced in any of the Ni composition ratios of 0.1, 0.2, 0.33 and 0.5.
Next, in order to reduce the NiO nanoparticles to Ni particles, the powder (b) (NiO nanoparticle-dispersed silica) was reduced in a hydrogen stream at a temperature of about 500 ° C. The XRD analysis result of each sample heat-processed in hydrogen stream is shown in FIG. In the samples with reduced Ni composition ratios of 0.1, 0.2, 0.33, and 0.5, a peak of Ni was also present in addition to the peak of amorphous silica.

(4) Microstructure of Ni-microporous amorphous silica composite Electron microscope with Ni composition ratios of 0.1, 0.2 and 0.33 for the Ni-microporous amorphous silica composite obtained as described above Observation (manufactured by JEOL Ltd .: JEM3000F) was performed. FIG. 5 shows a microstructure with a Ni composition ratio of 0.1, FIG. 6 shows a microstructure with 0.2, and FIG. 7 shows a microstructure with 0.33. In the figure, the black contrast portions are Ni particles.
From FIG. 5 to FIG. 7, Ni particles dispersed in the silica matrix were observed. It can also be seen that as the amount of Ni added increases, the amount of Ni formed in situ in the amorphous silica matrix also increases. Furthermore, it was confirmed that Ni particles were dispersed in the silica matrix even when the Ni addition amount was increased.

(5) Average particle diameter measurement evaluation of Ni nanoparticles The average particle diameter of the Ni nanoparticles dispersed in the Ni-microporous amorphous silica composite obtained as described above was measured. The measurement method was calculated from the result of reading the particle size distribution of nickel particles from a TEM image and statistically plotting the particle size distribution. Regarding the results of the particle diameter plot, FIG. 8 shows the Ni composition ratio 0.1, FIG. 9 shows the Ni composition ratio, and FIG.
From the measurement results, the average particle diameter of the Ni nanoparticles at each Ni composition ratio is 2.3 nm for Ni composition ratio 0.1, 3.6 nm for Ni composition ratio 0.2, and 4. 4 for Ni composition ratio 0.33. It was 3 nm.
From the above, it was confirmed that the Ni-microporous amorphous silica composite obtained as described above was a composite in which nanometer-order Ni particles were dispersed in amorphous silica. Furthermore, it was confirmed that by increasing the Ni composition ratio, the average particle diameter of the Ni particles dispersed in the amorphous silica can be increased, and the particle diameter can be controlled.

(6) Hydrogen Adsorption (Occlusion) Measurement Method The Ni-microporous amorphous silica composite hydrogen occlusion material was evaluated by measuring the hydrogen occlusion at measurement temperatures of 30 ° C, 150 ° C and 300 ° C.
This measurement method was performed by a method in accordance with “Measurement method of PCT characteristics of JIS H 7201 hydrogen storage alloy”. The sample sealed in the sample tube was first activated in a hydrogen atmosphere (about 0.1 MPa) at a sample tube temperature of 400 ° C. for 1 hour, and then vacuum heated for 2 hours (also about 350 ° C., about 10 ⁻³ Torr). . Thereafter, hydrogen was introduced up to 10 MPa at each measurement temperature, and the pressure reduction was similarly set. For 300 ° C and 150 ° C, temperature control is performed while checking the temperature of the sample tube with a heater block, and for 30 ° C, measurement is performed while adjusting the temperature using a constant temperature water bath (temperature control accuracy 0.01 ° C). Went. After setting the pressure, the determination standard of the equilibrium pressure was set to 0.0020 MPa for the sample tube pressure addition time (equilibrium time) of 420 sec (7 minutes). That is, it was determined whether the pressure change width was 0.0020 MPa within 420 seconds during pressurization, and if the determination pressure was exceeded, the determination measurement was continued until it was stable again.

(7) Results of hydrogen storage characteristics The results of hydrogen storage characteristics of Ni composition ratios of 0.1, 0.2 and 0.33 are shown in FIGS. 11, 12 and 13 and the results of hydrogen storage characteristics of silica alone containing no Ni. 14 shows.
(I) Regarding SiO ₂ porous body containing no metal particles (see FIG. 14)
In the case of silica alone at the measurement temperature of 30 ° C., the hydrogen storage amount up to 2 MPa was about 0.02 wt%, and the hydrogen storage amount up to 10 MPa was about 0.1 wt%.
(Ii) About Ni particle containing composite (refer FIGS. 11-13)
(A) The hydrogen storage amount up to 2 MPa and the hydrogen storage amount up to 10 MPa at each composition ratio at the measurement temperature of 30 ° C. were the following results in order.
When Ni composition ratio is 0.1: 0.055 wt%, 0.13 wt%.
When Ni composition ratio is 0.2: 0.09 wt%, 0.16 wt%.
When Ni composition ratio is 0.33: 0.10 wt%, 0.15 wt%.
(B) The hydrogen storage amount up to 2 MPa and the hydrogen storage amount up to 10 MPa at each composition ratio at the measurement temperature of 150 ° C. were as follows.
When Ni composition ratio is 0.1: 0.035 wt%, 0.09 wt%.
When Ni composition ratio is 0.2: 0.05 wt%, 0.11 wt%.
When Ni composition ratio is 0.33: 0.05 wt%, 0.10 wt%.
(C) The hydrogen storage amount up to 2 MPa and the hydrogen storage amount up to 10 MPa at each composition ratio at the measurement temperature at 300 ° C. were as follows.
When Ni composition ratio is 0.1: 0.015 wt%, 0.04 wt%.
When the Ni composition ratio is 0.2: 0.05 wt%, 0.10 wt%.
When Ni composition ratio is 0.33: 0.05 wt%, 0.09 wt%.

(8) Evaluation of hydrogen storage characteristics
From the results of hydrogen storage characteristics of Ni-microporous amorphous silica composite powder having a Ni composition ratio of 0.1, the hydrogen storage amount at 10 MPa at a measurement temperature of 30 ° C. was 0.13 wt%.
The hydrogen storage characteristics of Ni-microporous amorphous silica composite powders with Ni composition ratios of 0.2 and 0.33 are up to 2 MPa at both measurement temperatures of 150 ° C. and 300 ° C. with Ni composition ratios of 0.2 and 0.33. The hydrogen storage amount increased, and at 10 MPa, the hydrogen storage amount of 0.1 wt% or more was obtained for both Ni composition ratios of 0.2 and 0.33. Furthermore, at a Ni composition ratio of 0.33, a high hydrogen storage amount of 0.10 wt% at 2 MPa was obtained at a measurement temperature of 30 ° C., and the highest hydrogen storage amount at a measurement temperature of 30 ° C. When compared with silica alone at 2 MPa, a hydrogen storage amount of about 5 times was obtained by using a metal-added amorphous metal oxide with a Ni composition ratio of 0.33. When the Ni composition ratio was 0.2, a high hydrogen storage amount of 0.16 wt% or more was obtained at 10 MPa at a measurement temperature of 30 ° C.
From the above, it can be seen that the metal-added amorphous metal oxide hydrogen storage material of the present invention is excellent in hydrogen storage.

(9) Calculation of hydrogen adsorption amount Further, the hydrogen adsorption site was calculated as follows.
The estimated amount of hydrogen adsorption was calculated assuming that hydrogen was adsorbed at the interface between the nickel nanoparticles dispersed in the silica and the silica. As a result of reading the particle diameter of the nickel particles when the Ni composition ratio is 0.1, 0.2 and 0.33 from the TEM image and plotting the particle diameter distribution statistically, the average particle diameter is 2. They were 3 nm, 3.6 nm, and 4.3 nm.
The surface area of the particles of each average particle size was determined, and the amount of hydrogen adsorbed on the Ni particle surface when the nanoparticles were assumed to be dispersed in the silica was calculated from the amount of added Ni. The area occupied on the nickel particle occupied by one hydrogen atom when one hydrogen was adsorbed on the nickel particle was calculated as 6.49 × 10 ⁻²⁰ m ² . The amount of hydrogen estimated to be further adsorbed on the entire nanoparticle-silica interface was 0.037 wt% when the Ni composition ratio was 0.1, 0.2 and 0.3 at a measurement temperature of 500 ° C. %, 0.047 wt%, and 0.065 wt%. At 30 ° C., when the hydrogen pressure is 2 MPa or more, the occlusion amount (0.1 wt% or more) higher than these values is obtained, so that hydrogen is occluded not only in one layer on the surface of Ni nanoparticles but also in multiple layers. It was suggested that it can be done. This is considered to be a contribution of compositing as a Ni nanoparticle-dispersed silica composite sample.
Further, when the Ni composition ratio is 0.2, a high hydrogen storage amount is obtained at a hydrogen pressure of 10 MPa at a measurement temperature of 30 ° C., and when the Ni composition ratio is 0.33, a high hydrogen storage amount is obtained at a hydrogen pressure of 2 MPa. Therefore, when the average particle diameter of the dispersed Ni particles is 3.6 to 4.3 nm, it is considered that the contribution of the composite as the Ni nanoparticle-dispersed silica composite sample is excellent.

<Example 2>
[1] Production of Co-amorphous silica composite hydrogen storage material Si (OC ₂ H ₅ ) ₄ (TEOS) and Co (NO ₃ ) ₂ · 6H ₂ O are dissolved in ethanol and 30% by mass peroxidation. Hydrogen water was added to prepare a mixed solution. The mixed solution was prepared so that the Co / (Si + Co) composition ratio (hereinafter also simply referred to as Co composition ratio) was 0.2 and 0.33. Table 2 shows the composition of each composition ratio.
Then, the uniform Si-Co-O precursor solution was obtained by stirring the mixed solution of each composition ratio in ice-cooling for 2 hours.
Thereafter, polymerization treatment, atmospheric firing, reduction firing and the like were performed in the same manner as in Example 1 to obtain a Co-microporous amorphous silica composite hydrogen storage material.

[2] Evaluation of Co-microporous amorphous silica composite (1) Evaluation of XRD spectrum before and after reduction treatment As in Example 1, the XRD spectrum of the precursor after heat treatment in the atmosphere at 600 ° C. was examined. As a result (FIG. 15), it was confirmed that amorphous silica and Co ₃ O ₄ were formed in both cases where the Co composition ratio was 0.2 and 0.33.
Next, in order to reduce the Co ₃ O ₄ nanoparticles to Co particles, the Co ₃ O ₄ nanoparticle-dispersed silica was reduced in a hydrogen stream at 500 ° C. The XRD spectrum of each sample heat-treated in a hydrogen stream was examined. As a result (FIG. 16), the samples of Co composition ratio 0.2 and 0.33 composition subjected to reduction treatment each had a peak of Co in addition to the peak of amorphous silica. A trace amount of CoO peak as an impurity is detected.

(2) Microstructural evaluation of Co-microporous amorphous silica composite The Co-microporous amorphous silica composite obtained as described above was obtained from a composite having a Co composition ratio of 0.33 using a high-resolution transmission electron microscope. Observed. A microstructure with a Co composition ratio of 0.33 is shown in FIG. As a result, Co particles dispersed in the silica matrix were observed as in the case of Ni in Example 1. In the figure, the black contrast is Co particles.

(3) Hydrogen Storage Results of Co-Microporous Amorphous Silica Composite Hydrogen Storage Material FIG. 18 and FIG. 19 show the results of hydrogen storage characteristics with Co composition ratios of 0.33 and 0.2.
The hydrogen storage amount up to 2 MPa and the hydrogen storage amount up to 10 MPa at each composition ratio at the measurement temperature at 30 ° C. were as follows.
When Co composition ratio is 0.33: 0.06 wt%, 0.19 wt%.
When the Co composition ratio is 0.2: 0.06 wt%, 0.13 wt%.

(4) Evaluation of hydrogen storage characteristics In the case of silica alone at a measurement temperature of 30 ° C., the hydrogen storage amount up to 2 MPa is about 0.02 wt%, and the hydrogen storage amount up to 10 MPa is about 0.1 wt%. On the other hand, by adding Co so that the Co composition ratio is 0.2 to 0.33, it can be seen that the hydrogen storage amount is excellent, and the hydrogen storage amount at a measurement temperature of 30 ° C. is It turns out that it is excellent.

  The present invention is widely used in the field using hydrogen gas storage and transportation. That is, for example, it is used in hydrogen storage materials and fuel cells.

It is a graph which shows TG-DTA of the precursor of a Ni-amorphous silica composite. It is a graph which shows the MASS spectrum of the precursor of a Ni-amorphous silica composite. The XRD diffraction pattern of the precursor (b) after atmospheric baking and before reduction treatment is shown. The XRD diffraction pattern of the Ni-amorphous silica composite after a reduction process is shown. It is a transmission electron microscope image of Ni-amorphous silica composite powder having a composition ratio of 0.1. It is a transmission electron microscope image of Ni-amorphous silica composite powder having a composition ratio of 0.2. It is a transmission electron microscope image of Ni-amorphous silica composite powder having a composition ratio of 0.33. It is a graph which shows the Ni particle diameter distribution plot in the Ni-amorphous silica composite of composition ratio 0.1. It is a graph which shows the Ni particle diameter distribution plot in the Ni-amorphous silica composite of composition ratio 0.2. It is a graph which shows the Ni particle diameter distribution plot in the Ni-amorphous silica composite with a composition ratio of 0.33. It is a graph which shows the hydrogen storage amount of the Ni-amorphous silica composite of composition ratio 0.1. It is a graph which shows the hydrogen storage amount of the Ni-amorphous silica composite of composition ratio 0.2. It is a graph which shows the hydrogen storage amount of the Ni-amorphous silica composite of composition ratio 0.33. It is a graph which shows the hydrogen occlusion amount of only an amorphous silica. The XRD diffraction pattern of the precursor of the Co-amorphous silica composite after atmospheric baking and before reduction treatment is shown. The XRD diffraction pattern of the Co-amorphous silica composite after a reduction process is shown. It is a transmission electron microscope image of Co-amorphous silica composite powder having a composition ratio of 0.33. It is a graph which shows the hydrogen storage amount of the Co-amorphous silica composite of composition ratio 0.33. It is a graph which shows the hydrogen storage amount of the Co-amorphous silica composite of composition ratio 0.2.

Claims (12)

A composite comprising a porous substrate made of a microporous amorphous metal oxide, and hydrogen storage metal nanoparticles dispersed in the porous substrate;
The metal oxide comprises at least one selected from silica, alumina, and silica-alumina.   The hydrogen storage material according to claim 1, wherein the metal element constituting the hydrogen storage metal nanoparticles is nickel and / or cobalt.   The hydrogen storage material according to claim 1 or 2, wherein an average particle diameter of the hydrogen storage metal nanoparticles is 0.1 to 10 nm.   The composition ratio of the metal (I) in the metal oxide composing the composite and the metal (M) in the hydrogen storage metal nanoparticles is 0.1 to 0.00 in terms of molar ratio. The hydrogen storage material according to any one of claims 1 to 3, which is 5.   The composition ratio of the metal (I) in the metal oxide composing the composite and the metal (M) in the hydrogen storage metal nanoparticles is M / (I + M) of 0.15 to 0.00 in terms of molar ratio. The hydrogen storage material according to claim 1, which is 35. A method for producing a hydrogen storage material according to any one of claims 1 to 5, wherein a precursor solution preparation step of preparing a precursor solution by dissolving a metal alkoxy compound and a metal salt in an organic solvent;
A precursor forming step of concentrating the precursor solution or distilling off the organic solvent to synthesize a precursor; and
And a heat treatment step of heating the precursor to form a composite in which hydrogen-absorbing metal nanoparticles are dispersed in the porous substrate skeleton.   The method for producing a hydrogen storage material according to claim 6, wherein hydrogen peroxide is further added in the precursor solution preparation step.   The method for producing a hydrogen storage material according to claim 6 or 7, wherein the heat treatment step includes an air firing step and a reduction treatment step. The method for producing a hydrogen storage material according to claim 6, wherein the metal alkoxy compound is Si (OR ¹ ) ₄ .
(Wherein, R ¹ is an alkyl group having 1 to 4 carbon atoms, R ¹ is may be the same to each other or may be different.) The method for producing a hydrogen storage material according to claim 9, wherein the alkyl group of R ¹ is at least one selected from a methyl group, an ethyl group, and a propyl group.   The method for producing a hydrogen storage material according to any one of claims 8 to 10, wherein the air firing step is performed at a temperature of 400 to 1100 ° C in the air.   The method for producing a hydrogen storage material according to any one of claims 8 to 11, wherein the reduction treatment step is performed at a temperature of 300 to 700 ° C in a hydrogen gas flow.