JP2000281303A - Hydrogen occlusion body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the volume packing efficiency of a carbon-based hydrogen occlusion material by constituting a porous material from a mixture of metals and a nonmetal in org. material. SOLUTION: Oxides of transition metals such as Fe, Ni, Co having <=50 nm particle size of the primary particles, or oxides of transition metals mixed with 1 to 10 % volume ratio of fine particles such as aluminum oxide having a smaller particle size than the transition metal oxides are uniformly pulverized and mixed by a ball mill, or the like. Then the mixture is introduced into an electric furnace, and only the transition metal oxides are reduced in a hydrogen atmosphere to obtain a mixture of transition metals and oxides. Then the mixture is formed by sintering or the like. in an inert atmosphere to obtain a porous material having >=50% porosity. Then, a carbon material such as carbon nanofiber is synthesized in the open pores of the porous body by a thermal CVD method, or the like, in an atmosphere containing hydrocarbon gas such as ethylene gas or carbonic acid gas such as carbon monoxide to obtain a hydrogen occlusion material. A hydrogen occlusion alloy is preferably incorporated into the structural phase of the porous material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a high-capacity hydrogen storage material.

[0002]

2. Description of the Related Art A hydrogen storage material is an important material as an energy storage material, and is particularly indispensable when considering an energy storage method for an electric vehicle or the like.

A typical hydrogen storage material is a LaNi alloy or the like, which is widely used as a secondary battery.

[0004] However, these metal-based hydrogen storage materials have a problem that they are not suitable for use in electric vehicles and the like, in particular, because the weight relative to the amount of stored hydrogen is too large.

[0005] In recent years, new carbon-based materials such as fullerenes, carbon nanotubes, and carbon nanofibers have been discovered. These materials are attracting attention as a next-generation energy storage method because they are lightweight and simultaneously absorb a large amount of hydrogen.

A practical problem with these materials is that there is no way to densely fill containers of fixed volume.

[0007] In particular, carbon fiber materials such as carbon nanotubes and carbon nanofibers, once synthesized, are intended to be filled in a rectangular parallelepiped or columnar container.
Even if a method such as pressing is used, the filling rate does not increase and there is a limit. Now, even if the hydrogen storage amount per volume of the carbon fiber material itself is 10 kgH / m3, if the filling rate is 50%, the practical hydrogen storage amount is 5% of 50% of the storage amount of carbon fiber alone.
kgH / m3.

[0008] The low volume filling rate of hydrogen increases the capacity of the energy tank, and as a result, it is a great hindrance to various practical uses as well as the density with respect to weight.

Since the above problems cannot be solved, there is a hydrogen storage carbon material having a higher capacity than a conventional hydrogen storage alloy, but there is a problem that it is not practical.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. That is, the present invention proposes a method for increasing the volume filling ratio of the carbon-based hydrogen storage material in practical use.

[0011]

The embodiments of the present invention will be described below in order.

Fe, N having a primary particle size of 50 nm or less
i, a transition metal oxide such as Co, or aluminum oxide, magnesium oxide, zirconium oxide, which are smaller than the particle diameter of the transition metal oxide and the transition metal oxide;
Fine particles such as silicon oxide are uniformly crushed and mixed by a ball mill or the like.

After mixing the above-described oxide particles, the mixture is introduced into an electric furnace, and only the transition metal oxide is reduced under a hydrogen atmosphere, and the transition metal fine particles are mixed with aluminum oxide, magnesium oxide, zirconium oxide, and silicon oxide. And mixed powder with fine particles.

Next, the transition metal and oxide fine particle mixed powder is formed into a porous body having a porosity of 50% or more by a method such as sintering.

The mixing ratio of the transition metal particles to the fine particles of aluminum oxide, magnesium oxide, zirconium oxide, silicon oxide or the like is preferably 1% to 10% by volume. This is because the growth of the transition metal particles can be effectively suppressed in this range.

The mixed powder is preferably handled in an inert atmosphere. This is because the transition metal fine powder is rapidly oxidized when exposed to oxygen.

At this time, it is preferable that the process from reduction to sintering is performed continuously without exposure to the atmosphere.

Since the oxide has the fine particles dispersed therein, it is possible to suppress the grain growth of the transition metal constituting the porous body.

Next, under an atmosphere containing a hydrocarbon gas such as ethylene gas or acetylene gas, or a carbon dioxide gas such as carbon monoxide or carbon dioxide, carbon nanofibers, carbon nanotubes, fullerenes, etc. Synthesize carbon-based materials.

The synthesis method is not particularly limited.
VD method and the like can be mentioned. Thereby, decomposition of the raw material gas occurs on the transition metal forming the porous body,
Carbon deposits.

The process from the reduction of hydrogen to the synthesis of the carbon-based material is preferably performed continuously without exposing it to the atmosphere.

By the above process, it is possible to form a composite of a porous body and a carbon-based material such as carbon nanotubes, carbon nanofibers and fullerenes grown at a high density inside the porous body.

A second aspect of the present invention is that the constituent phase of the porous body contains a hydrogen storage alloy.

The reason for mixing the hydrogen storage alloy is that the total amount of hydrogen storage can be increased by adding the hydrogen storage alloy.

In this case, the hydrogen storage alloy and Fe, Ni, C
o and catalysts and oxide fine particles with a high grain growth suppression effect,
After mixing, the mixture is formed into a porous body having a predetermined porosity.

After the formation of the porous body, the porous body is introduced into an electric furnace or the like, and a carbon-based material is synthesized by a method such as thermal CVD.

It is preferable that a series of processes of mixing, molding, and synthesizing the carbon-based material be performed in an inert atmosphere.

[0028]

(Embodiment 1) An embodiment will be described with reference to FIG. 1 and FIG. Nickel oxide powder having a primary particle size of 50 nm or less, and aluminum oxide powder (grain growth suppressing material) having a particle size of not more than the nickel oxide powder 1
Are uniformly mixed and then reduced under a hydrogen atmosphere to produce a fine powder in which 5% by volume of aluminum oxide is mixed with respect to nickel (metal catalyst) 2.

After the fine powder is produced, it is continuously introduced into a sintering furnace without being exposed to the atmosphere, and has a porosity of 90% of 1000 m
A cubic porous body of m3 was formed.

After the formation, a mixed gas of ethylene and hydrogen (1: 4) was further introduced into the same furnace, and carbon nanotubes (carbon fibers) 3 were synthesized at 600 ° C.

After the synthesis, it was taken out of the electric furnace and the porosity was measured to be 7%. The procedure of the synthesis is shown in FIG.

Subsequently, the composite of the carbon nanotube and the transition metal porous body was evaluated for occlusion in a hydrogen atmosphere at room temperature and -10 atm using a hydrogen occlusion apparatus. did. (Comparative Example 1) On the other hand,
10 tons inside a cubic mold with a volume of 1000 mm3
The same carbon nanofibers as those synthesized in Example 1 were filled at a press pressure of. The porosity of the carbon nanofiber pressed body was measured and found to be 45%.

The pressed body of carbon nanofibers (hydrogen storage body 4) was introduced into a hydrogen storage evaluation apparatus, and hydrogen storage evaluation was performed under the same conditions as in Example 1.
6 g of hydrogen were stored.

[0034]

As described above, according to the present invention, it is possible to manufacture an energy storage unit having a high filling rate of the hydrogen storage carbon material and a large hydrogen storage amount.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating an embodiment of the present invention.

[Explanation of symbols]

 1 Grain Growth Inhibitor 2 Metal Catalyst 3 Carbon Fiber 4 Hydrogen Storage

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasuhiro Gonohe 1-term, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center (reference) 4G040 AA32 AA34 AA42 4G046 CB01 CB08

Claims (3)

[Claims] 1. A hydrogen storage body characterized in that carbon fibers are filled in pores of a porous body, wherein the porous body is made of a mixture of a metal and a nonmetallic inorganic material. Characterized by hydrogen storage. 2. The hydrogen storage body according to claim 1, wherein the porous body contains a hydrogen storage alloy as a constituent phase. 3. A hydrogen storage material, wherein the nonmetallic inorganic material mixed with the porous material according to claim 1 or 2 has a smaller particle size than the metal particles constituting the porous material.