JP2000063121A - Oxide-based hydrogen storage materials - Google Patents

Abstract

(57) Abstract: The present invention relates to an oxide-based hydrogen storage material, and more particularly to a hydrogen storage material comprising vanadium oxide having hydrogen storage characteristics.
Provided is an oxide-based hydrogen storage material that is reduced in weight and cost and has improved surface poisoning. SOLUTION: The hydrogen storage oxide is at least one of V ₂ O _{5 and} KVO ₃ among vanadium oxides.
Containing a seed or as a VO-based oxide in atomic%,
O: 68.5 to 77.5%, balance: V or KV-
As an O-based oxide, K: 15.5 to 24.5%, O: 5
It is characterized by containing at least one oxide of 5.5 to 64.5%, with the balance being V.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide-based hydrogen storage material, and more particularly, to an oxide composed of vanadium oxide having hydrogen storage characteristics, which is lightweight and cost-effective and has improved surface poisoning. Physical hydrogen storage material.

[0002]

2. Description of the Related Art From the viewpoint of global environmental problems, as new energy to replace fossil fuel, solar heat, nuclear power, hydraulic power,
Recycling of wind power, geothermal heat and waste heat has been proposed. However, in all cases, the common problem is how to store and transport that energy. A system that uses solar heat or hydraulic power to electrolyze water and uses hydrogen obtained as an energy medium is the ultimate in that the raw material is water and the product of energy consumption is water. Can be said to be clean energy.

As a means for storing and transporting hydrogen, the hydrogen storage alloy is capable of storing and storing hydrogen gas of about 1000 times or more the volume of platinum itself, and its volume density is liquid or solid hydrogen. Nearly equal or better. As the hydrogen storage material, AB ₅ type alloy, AB ₂
Type alloys have been put to practical use and BCC type alloys have been developed.

As described above, a hydrogen storage alloy is generally used as the hydrogen storage material. However, although it can be expected that the oxide system may have a hydrogen storage capacity, it has been completely unknown as a hydrogen storage material has not been studied. In the hydrogen storage alloy, an oxide is intended to be used, for example, as described in JP-A-6-81011, an alloy is used as a raw material so that an oxide powder is reduced and sintered to form an alloy. As disclosed in JP-A-7-258703, there is one that is dispersed in an alloy to prevent pulverization of the alloy. However, all of them have only auxiliary functions, and no one pays attention to the storage capacity of the oxide itself. Therefore, it is desired to use the oxide itself as a hydrogen storage material and develop it from the viewpoints of characteristics superior to alloys, in particular, weight reduction and improvement of poisoning.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to investigate an oxide having a hydrogen storage function, and to provide an oxide-based hydrogen storage material showing new characteristics which are not present in current hydrogen storage alloys. is there. Another object of the present invention is to provide an oxide-based hydrogen storage material by including, as the oxide, a vanadium-based oxide that is easy to be made into powder and whose initial activation is relatively easy. To do.

Another object of the present invention is to investigate the optimum composition of the vanadium oxide in the V--O binary system and the K--V--O ternary system, and improve the surface activation as a powder. An object is to provide an oxide-based hydrogen storage material that can be formed and exhibits excellent durability.

[0007]

[Means for Solving the Problems] The above object is to absorb hydrogen.
Of oxides for vanadium, which are V₂O _Five
Or KVO₃Containing at least one of
Oxide-based hydrogen storage material characterized by having
Will be achieved.

Further, the above-mentioned object is as a V—O type oxide, in atomic%, O: 68.5 to 77.5%, balance: V,
Alternatively, as a K-V-O-based oxide, K: 15.5 to 2
It is also achieved by an oxide-based hydrogen storage material characterized by containing at least one kind of oxide consisting of 4.5%, O: 55.5 to 64.5%, and the balance: V.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Since the hydrogen storage material of the present invention is an oxide, the composition can be adjusted relatively easily, and the powder can be purified in advance, and the purified powder is mixed. It can be manufactured by a simple process consisting of steps. Further, as the oxide having the above composition, an oxide having a large hydrogen storage amount can be obtained. Even with an oxide containing V, an oxide having another composition cannot obtain a sufficient hydrogen storage amount.

FIG. 1 is a VO system binary state diagram. Figure 2
Is a binary system state in the range of O: 53 at% to 73 at% in FIG.
(RP Elliott: binary system state diagram, 1
965, pp. 1796). In this system, V-O solid
Solution phase, NaCl type VO phase, V _nO_2n-1Represented by
Gunelli phase (V₂O₃-VO₂System) and V_2nO_5n-2Wa
Zurei (VO₂-V₂O_FiveSystem)). Of that
Then, the VO solid solution phase is in the order of oxygen atomic% as shown in FIG.
The α ', β and γ phases are present up to about 35 at%,
Above that, it looks like Figure 2. From FIG. 2, the oxide phase
For stabilization of a single phase,
It's changing a lot.

These non-stoichiometric compounds have a compositional deviation as plane defects in the crystal regardless of vacancies or interstitial atoms. None of these intermediate oxides have been sorted out by paying attention to their hydrogen storage characteristics, but the fact that the defects in the crystals greatly contribute to the hydrogen storage characteristics from the above equilibrium theory indicates that The behavior is considered to be one in which the dependence on microstructure is shown.

V ₂ O ₅ of the present invention is synthesized by thermal decomposition of ammonium metavanadate. Since the raw material ammonium metavanadate is easily mixed with impurities, it is necessary to purify it in advance in order to remove these impurities. V ₂ O ₅ is relatively easy to use V ₂ O ₃
Is reduced to. The method for synthesizing KVO ₃ of the present invention includes:
There is a method in which the reduction reaction of vanadium oxide is interrupted midway. Alternatively, a solid phase reaction method or a hydrothermal synthesis method from a mixture of two phases may be used.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 This example was carried out to study a V—O binary oxide. A sample of the hydrogen storage material was prepared as follows. In the sample of this example, the raw material powder was adjusted to have a particle size of 5 μm to 100 μm. Purity of high purity (3 nine to 4 nine) was activated at 40 ° C. at 10 ⁻⁴ torr vacuum evacuation +4 MPa hydrogen pressurization was repeated 4 times. The method is performed by the vacuum origin method defined in the pressure composition isotherm measurement method (JIS, H7201). Table 1 shows the hydrogen storage results of this example and the comparative example.

[0014]

[Table 1]

From Table 1, V ₂ O ₅ (O: 71.
4 at%), the hydrogen storage amount is 5.26 wt%, while on the other hand, in VO ₂ , V ₂ O ₃ and V ₆ O _{13 of} Comparative Examples, 0.03 to 0.08 wt%, and You can see that it does not occlude.

Example 2 This example is based on the A-V-O ternary system (A: Li, Mg, C).
a) It was carried out to study oxides. The method for preparing the sample and measuring the hydrogen storage amount are the same as in Example 1. Table 2 shows the hydrogen storage results of this example and the comparative example.

[0017]

[Table 2]

From Table 2, the KVO of the embodiment is shown.₃(K: 20at
%, O: 60.0 at%), the hydrogen storage amount is 2.00 wt%
In contrast, Li of the comparative example₃VO_Four, Mg (VO
₃) ₂And Ca₂V₂O₇Then, 0.00 to 0.17
It can be seen that the wt% hardly occludes.

[0019]

EFFECTS OF THE INVENTION According to the present invention, an oxide type hydrogen storage material can be manufactured, and it has excellent characteristics in weight reduction and poisoning compared with conventional metal type materials. Also, it can be expected as a material for battery electrodes.

[Brief description of drawings]

FIG. 1 is a diagram showing a state diagram of a V—O binary system according to the present invention.

FIG. 2 is a part of a phase diagram of a V—O binary system according to the present invention.
It is a figure which shows the area | region of 3 at% -73 at% O.

Claims (2)

[Claims] 1. A hydrogen storage oxide, which is at least one of V ₂ O _{5 and} KVO ₃ among vanadium oxides.
An oxide-based hydrogen storage material containing a seed and having a hydrogen storage property. 2. As a V—O-based oxide, in atomic%, O:
68.5 to 77.5%, balance: V, or as K-VO oxide, K: 15.5 to 24.5%, O: 55.
An oxide-based hydrogen storage material, characterized by containing at least one kind of oxide consisting of 5 to 64.5% and the balance: V.