JP2743123B2 - Materials for hydrogen storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage material that stores and releases hydrogen by reversibly reacting with hydrogen.

[0002]

2. Description of the Related Art As is well known, a hydrogen storage material has the property of reversibly reacting with hydrogen to absorb and release hydrogen with the entrance and exit of reaction heat. The technology to store and transport hydrogen using this chemical reaction has been put into practical use.
Furthermore, the technology for constructing heat storage and heat transport systems using reaction heat is being developed and put into practical use.

[0003] In practical use of various applications, it is necessary to further improve the characteristics of the hydrogen storage material. For example, increasing the amount of hydrogen storage, lowering the cost of raw materials, and improving the plateau characteristics are cited as major issues. . Conventionally, materials for hydrogen storage include La-Ni, Mg-Ni, Ti-Fe, M
m-Ni, Ti-Cr and the like have been developed and proposed, and are being applied to various applications described above and put to practical use.

Among the above hydrogen storage materials, Mg-N
i indicates an excellent hydrogen storage amount of about 400 cc / g, while the other materials only show a hydrogen storage amount of about 200 cc / g. However, the hydrogen storage / release reaction is slow, and if the temperature is not higher than 350 ° C., hydrogen storage / release cannot be performed smoothly. For this reason, the development of a material which has a fast hydrogen storage / release reaction and can be used at a lower temperature is being promoted. Japanese Patent Publication No. 59-38293 proposes a Ti-Cr-V alloy. According to the Ti-Cr-V alloy, there is an advantage that the hydrogen storage / release reaction is fast and that it can be used in a temperature range that can exist as industrial waste heat.

[0005]

However, the above-mentioned Ti-
In a Cr-V alloy, the equilibrium pressure of the plateau is about 150 ° C. at normal pressure.
Requires a high heat source of about 00 ° C. Therefore, although it is an effective material for utilizing waste heat as described above, it is not practical to prepare a high-temperature heat source when it is used for applications such as storage and transportation of hydrogen, and lacks practicality. There is a point.

SUMMARY OF THE INVENTION The present invention has as its basic object to solve the above problems, and can effectively absorb and release hydrogen at normal temperature.
Moreover, it is an object of the present invention to provide a hydrogen storage material exhibiting an excellent hydrogen storage capacity as compared with conventional materials.

[0007]

Means for Solving the Problems] hydrogen storage material of the present invention for solving the above-general formula _{Ti x Cr 2-yz V y} Fe
_It has a composition represented by _z . However, in the formula, x, y, and z are 0.5 ≦ x ≦ 1.
2, 0 <y ≦ 1.5, 0 <z ≦ 0.5, 0 <y + z <
2.0.

[0009]

According to the present invention, Ti, Cr,
The temperature at which the plateau equilibrium pressure becomes normal pressure is reduced to normal temperature by the action of the composition components of V and Fe, and hydrogen can be effectively absorbed and released at normal temperature. In addition, the hydrogen storage amount is increased and the platability is improved, so that the efficiency of hydrogen storage / transport is improved.

Here, the reason why the composition ratio x of Ti is limited is as follows. When x exceeds 1.2, the stability of hydrogen in the alloy becomes remarkably high. A heat source at a high temperature of 100 ° C. or higher is required, which is not practical. When x is less than 0.5, a long-time degassing treatment at a temperature of 100 ° C. or more is required as an initial activation condition, and the treatment itself becomes difficult.

The reason why the composition ratio y of V is limited is as follows. Although the amount of hydrogen occlusion is remarkably increased by the inclusion of V, when the composition ratio y exceeds 1.5, the case where Ti exceeds the upper limit is considered. Similarly, the range was determined because the stability of hydrogen in the alloy was significantly increased and was not practical.

Further, the reason why the composition ratio z of Fe is limited is that, when z exceeds 0.5, the hydrogen storage capacity is reduced, and the storage capacity is equal to or less than that of the above-mentioned Ti-Cr-V alloy. This is because it does not have a sufficient storage amount. In order to verify the relationship between z and the hydrogen storage amount, FIG. 1 shows the hydrogen storage amount when x is fixed to 1 and y is fixed to 1.2, and z is used as a parameter. As is apparent from FIG. 1, when z exceeds 0.5, the hydrogen storage amount is lower than that in the case where Fe is not contained, indicating that the excessive amount of Fe inhibits the storage capacity. I have.

[0013]

EXAMPLES Examples of the present invention (materials of the invention) will be described below in comparison with comparative materials outside the scope of the present invention. Ti,
The raw materials for each of Cr, V, and Fe were weighed and blended to have the composition shown in Table 1. This mixture was placed in a crucible of an arc vacuum melting apparatus, melted in an arc under a high purity Ar gas atmosphere, cooled to room temperature in the apparatus, and solidified. The obtained alloy is 100 to 20 in air.
The sample was pulverized to 0 mesh to obtain measurement samples, and 5 g of each sample was sealed in a stainless steel reaction vessel in a high-pressure metal hydride manufacturing apparatus.

Note that an activation process was performed as a process before measuring the hydrogen storage / release characteristics using the sample. That is, after degassing by heating at 50 ° C. for about 1 hour while evacuating the reaction vessel under reduced pressure (about 10 ⁻² mmHg),
At the same temperature, high-purity hydrogen at a pressure of 40 kgf / cm ² was introduced, and then cooled to 20 ° C. By such treatment, the sample immediately began to absorb hydrogen, and after 30 minutes, the absorption of hydrogen was completed. Further, the vessel was evacuated while being heated to 50 ° C. to release hydrogen from the sample. These processes were repeated plural times to complete the activation process.

Next, the hydrogen storage / release characteristics of each sample were measured. That is, after the vessel temperature was lowered to 20 ° C. and maintained, a predetermined amount of high-purity hydrogen was introduced into the vessel. After hydrogen was absorbed by the sample and the pressure in the container was stabilized, the amount of hydrogen absorbed in the sample was determined using the hydrogen pressure in the container and the constant volume method. Again, a predetermined amount of hydrogen was introduced into the container, and after the pressure was stabilized, the hydrogen pressure and the amount of absorbed hydrogen were determined. The above operation,
The process was repeated until the pressure in the vessel became 50 kgf / cm ^2, and a hydrogen pressure-absorption amount-isothermal curve was obtained. Hydrogen pressure of each sample-
The absorption amount-isothermal curve was measured, and the hydrogen storage amount at a hydrogen pressure of 50 kgf / cm ² is shown in Table 1.

As described above, hydrogen was applied to each sample at 50 kgf /
After occlusion to a pressure of cm ^2, a predetermined amount of hydrogen was discharged from the vessel while the reaction vessel was kept at the aforementioned 20 ° C. After the hydrogen pressure in the container was stabilized, the amount of hydrogen released from the sample was determined using the pressure in the container and the constant volume method. A predetermined amount of hydrogen was discharged again from the reaction vessel. The above operation was repeated until the pressure in the vessel became 0.2 kgf / cm ^2, and a hydrogen pressure-absorption amount-isothermal curve in a hydrogen releasing process was obtained. The plateau property was evaluated from the slope of the curve at the center of the plateau on the hydrogen pressure-absorption amount-isothermal curve at the time of hydrogen release. Specifically, Table 1 shows Δ (LnP) / Δ (H / M) as a plateau evaluation value. Note that P indicates the hydrogen pressure, and H / M indicates the amount of hydrogen (atomic ratio between hydrogen and metal) absorbed by the sample. In addition, comparative material No. 1 and N
o. In the case of No. 2, the plate-equilibrium pressure becomes normal pressure at a higher temperature than that of the inventive material, and therefore, for other materials, 20 ° C.
In comparison material no. 1 and N
o. No. 2 absorbed hydrogen at 100 ° C. (including activation treatment).

[0017]

[Table 1]

As is clear from Table 1, all of the materials of the present invention (Nos. 4 to 7) showed a hydrogen storage capacity of Comparative material No.
It is much larger than 1-3. In addition, the platen properties of the inventive materials were all good, but the comparative materials were no. 3
Except for, the platiness was inferior. In addition, comparative material No.
In No. 3, although the platability was good due to the inclusion of Fe, the hydrogen storage amount was greatly reduced due to the excessive Fe content. As described above, the inventive material has excellent characteristics in both the hydrogen storage capacity and the plateau property.
In addition, it exhibited a plateau-equilibrium pressure of normal pressure at normal temperature (20 ° C.), and was able to efficiently absorb and release hydrogen at normal temperature. On the other hand, the comparative material No. 1 and N
o. 2, as described above, the temperature at which the plate-equilibrium pressure becomes normal pressure exceeds normal temperature, and hydrogen is effectively absorbed at normal temperature.
It was difficult to discharge.

[0019]

As described above, according to the present invention,
Formula Ti _x Cr composition represented by _2-yz V _y Fe _z (where in the formula, x, y, z are, 0.5 ≦ x ≦ 1.2,0 <y
≦ 1.5, 0 <z ≦ 0.5, 0 <y + z <2.0), so that hydrogen can be effectively absorbed and released at room temperature, and the hydrogen storage amount Can be increased, and there is an effect that the plateability is improved. Therefore, there is an effect that it can be effectively used for applications such as storage and transportation of hydrogen.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the Fe content on the amount of hydrogen absorbed.

Claims (1)

(57) [Claims] 1. A general formula hydrogen storage material and having a composition represented by _{Ti x Cr 2-yz V y} Fe z In the formula, x, y, z are, 0.5 ≦ x ≦ 1.2, 0 <y
≦ 1.5, 0 <z ≦ 0.5, 0 <y + z <2.0