JP2002097535A - Hydrogen absorbing alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cheap and light hydrogen absorbing alloy with a high, effective hydrogen-absorbing capacity V of 0.6 mass% or more, which absorbs and desorbs hydrogen promptly, and does not deteriorate even by repetitive uses. SOLUTION: The hydrogen absorbing alloy with an effective hydrogen absorbing quantity of 0.6 mass% or more comprises having a composition expressed by the following general formula (1) or (2), and enabling the alloy to absorb hydrogen under a condition at 0-50 deg.C and at a hydrogen pressure of 0.5-1.1 MPa, and to release hydrogen under a condition between 60 deg.C and a boiling point of water and at a hydrogen pressure of 0.01-0.3 MPa; Ca1-xMgxNiz (1) wherein, 0.60<=x<=0.85; and 1.8<=z<=2.2 Ca1-xMgx(Ni1-yMy)z (2) wherein, M is at least one kind of elements selected from a subgroup consisting of Al, Si, P, Cr, Mn, Fe, Co, Cu, and Zn; 0.60<=x<=0.85; 0<=y<=0.2; and 1.8<=z<=2.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrogen storage alloy suitable for use in a hydrogen fuel cell, a hydrogen storage container or the like as a hydrogen storage means, or as a heat pump or a heat storage device as a thermo-chemical energy conversion means. About.

[0002]

2. Description of the Related Art A hydrogen fuel cell, which supplies hydrogen as a fuel to a negative electrode and reacts with oxygen supplied to a positive electrode to take out electricity, unlike a generator using fossil fuel, is different from a generator using fossil fuel during operation.
Since it is a clean energy source that does not generate O ₂ , NO _x , SO _x, etc., and has high energy conversion efficiency, it is currently used as a power generation system for small-scale local power generation and home power generation, and as a battery for electric vehicles. Development is underway.

In this hydrogen fuel cell, a hydrogen storage alloy can be used as hydrogen storage means. That is,
The hydrogen gas of the fuel is stored in a hydrogen storage alloy, and the hydrogen gas is released little by little from the alloy and supplied to the negative electrode. In this case, the supply of hydrogen to the hydrogen storage alloy may be performed by storing hydrogen supplied from the outside into the alloy, or supplying external electricity such as surplus electric power at night to the fuel cell to generate hydrogen generated by the fuel cell. Can be stored in the hydrogen storage alloy.

[0004] In the hydrogen storage alloy, the hydrogenation reaction when storing hydrogen is an exothermic reaction, and the decomposition reaction when releasing hydrogen is an endothermic reaction. Due to the property that the hydrogen storage / release reaction is a reversible reaction involving heat absorption / release, the hydrogen storage alloy has a heat-chemical energy conversion function. Using this function, it has been attempted to apply the hydrogen storage alloy to heat storage and chemical heat pumps.

[0005] For example, a hydrogen storage alloy is used for heat storage and heat transport of solar heat (eg, hot water of a solar collector) and waste heat (eg, waste hot water) of a cleaning plant as a clean energy source like a fuel cell. Can be used. That is, when heat is supplied to the alloy storing hydrogen, the heat is used to release hydrogen from the alloy, and the heat is stored as chemical energy in the hydrogen storage alloy. Next, when the released hydrogen reacts with the alloy, the alloy generates heat. The heat is used for an appropriate application (eg, heating a greenhouse).

In a heat pump to which a hydrogen storage alloy is applied, first, an alloy storing hydrogen is heated to a certain temperature to release hydrogen. Next, when the released hydrogen is pressurized to a temperature equal to or higher than the equilibrium dissociation pressure at that temperature and then hydrogen is occluded again in the alloy, a temperature higher than that temperature is obtained. By utilizing this, heat can be pumped from the low temperature side to the high temperature side.

In the applications described above, the hydrogen storage alloy reversibly stores and releases hydrogen by a gas-solid reaction shown in the following equation (a). (a) 2M + xH ₂ ⇔2MH _X (M: hydrogen storage alloy, reaction to the right direction is an exothermic reaction) That is, if the hydrogen pressure is increased and / or the temperature is lowered from the equilibrium state, the reversible reaction of the equation (a) occurs. Proceeding to the right, hydrogenation of the alloy occurs and hydrogen is stored in the alloy. Conversely, when the hydrogen pressure is lowered and / or the temperature is raised, the reaction proceeds to the left where hydrides decompose and hydrogen dissociates,
Hydrogen is released from the alloy.

This reversible reaction is a different reaction from the electrochemical reversible reaction represented by the following formula (b) in a hydrogen storage electrode used as a negative electrode in a nickel-hydrogen battery. (b) M + H ₂ O + e ⁻ ⇔OH ⁻ + MH Therefore, in order to use the hydrogen storage alloy for the above-mentioned applications in order to expand the use of clean energy, it is necessary to use hydrogen for nickel-hydrogen batteries which has already been put to practical use. It is necessary to develop a hydrogen storage alloy that is different from the storage alloy and is suitable for hydrogenation and hydrogen dissociation reactions in the gaseous solid phase.

[0009]

The general reaction conditions of a hydrogen storage alloy for hydrogen storage utilizing the reaction of the above-mentioned formula (a) are to store at low temperature / high pressure and release at high temperature / low pressure. Was. Recently, the practical use of hydrogen storage alloys has been approached, and the hydrogenation reaction has been carried out at room temperature, that is, at a temperature higher than the conventional temperature of about 20 ° C, and at a hydrogen gas pressure of about 1 MPa, which is not subject to the High Pressure Gas Control Law. To attempt to occlude hydrogen. In this case, the conditions of the dehydrogenation reaction when releasing hydrogen are such that the temperature is 100 ° C. or less and the hydrogen pressure is atmospheric pressure, that is, about 0.1 MPa because the heating source is generally hot water. It is. A hydrogen storage alloy that absorbs and releases a large amount of hydrogen under such conditions is extremely useful for hydrogen storage such as a hydrogen fuel cell, heat storage using (waste) hot water, and a heat pump.

FIG. 1 schematically shows the hydrogen absorption / desorption characteristics required for a hydrogen storage alloy that absorbs and releases hydrogen under such conditions. FIG. 1 is a pressure-composition isotherm diagram (P-C-T curve) (hereinafter, isothermal) in which the horizontal axis represents hydrogen concentration (% by mass, the same applies hereinafter) and the vertical axis represents hydrogen equilibrium dissociation pressure (Peq, MPa). This is called a diagram). This isotherm is created by measuring the amount of hydrogen storage that becomes equilibrium while changing the hydrogen pressure at a constant temperature.

As shown in FIG. 1, the effective hydrogen storage amount V when storing and releasing hydrogen under the above conditions is 20 ° C., 1MPa.
It can be expressed as a difference between the hydrogen storage amount V1 at a and the hydrogen storage amount V2 at 100 ° C. and 0.1 MPa. Therefore, to increase the effective hydrogen storage amount V, V1 is larger and V2 is larger.
Should be smaller. In other words, hydrogen storage alloys used for hydrogen storage such as hydrogen fuel cells, heat storage, and heat pumps have a large hydrogen storage capacity V1 at 20 ° C. and 1 MPa, and have a large hydrogen storage capacity V1 at 100 ° C. and 0.1 MPa. It is required that the hydrogen storage amount V2 is small and the effective hydrogen storage amount V is as large as possible.

It is also desirable that the hydrogen storage alloy be lightweight. This is necessary especially when a hydrogen fuel cell is mounted on an electric vehicle. In addition, in applications such as hydrogen storage and heat storage, large amounts of hydrogen storage alloy are used, so the production cost of hydrogen storage alloys is also important, and hydrogen storage alloys that can be manufactured from abundant and inexpensive raw materials are required. ing.

A typical practical hydrogen storage alloy, the MmNi ₅ series alloy, has a very flat plateau, and the effective hydrogen storage amount V under the above conditions is about 1% by mass. However, this alloy is known as Mm (Misch metal, a mixture of rare earth metals)
Ni is an alloy composed of relatively expensive components, which is disadvantageous in terms of cost.

In a Mg ₂ Ni alloy which is a lightweight and inexpensive hydrogen storage alloy using Mg, V1 is very large at 3.6% by mass under the above conditions, but V2 is also about 3.6% by mass. Release of hydrogen in the atmosphere is not possible.

The reduction of V2 by increasing the hydrogen absorption / desorption pressure of the Mg ₂ Ni alloy includes the enhancement of the hydrogen absorption / desorption pressure by elemental substitution, and the improvement of the hydrogen absorption / desorption pressure by amorphousization and nanometer scale. However, there is no report that can be used under the above conditions.

As a Mg-based hydrogen storage alloy having a small V2, A
B ₂ C ₉ alloy (A: rare earth element, B: alkaline earth element such as Mg, C: Ni and other transition metal elements) emits up to 1.8% by mass of hydrogen at a temperature of 100 ° C or less. Kaihei 11-
It is disclosed in Japanese Patent No. 217643. However, this alloy requires an expensive rare earth element.

Ca _0.5 Mg _0.5 Ni ₂ , which is an alloy obtained by adding Ca, which is inexpensive and lightweight to Mg, as in Mg, is disclosed in Mat. Res. Bull., Vol.
5 (1980) 275-283. V1 of this alloy
Is about 1.7 wt%, greater than MmNi ₅ is hydrogen absorption and desorption pressures low, V2 is since the size of about 1.3 wt%, the effective hydrogen storage quantity V is only about 0.4 mass%.

[0018] Journal of Alloys and Compounds 284 (1
999) 145-154 reports a CaMg ₂ Ni ₉ alloy as an Mg—Ca alloy having a high hydrogen release pressure. This alloy is MmNi
_{Like the 5} series alloy, the plateau is very flat and V2 is 0.
1% by mass or less. However, on the contrary, since the hydrogen absorption / desorption pressure is too high, the temperature must be set to 0 to absorb hydrogen sufficiently.
It must be lowered to around ℃.

Japanese Patent Application Laid-Open No. 11-264401 discloses Ca _1-a Mg _a
(Ni _1-x M _x ) _Z (0 <a <0.5, 0 <X ≦ 0.8, 2 <Z <
The effective hydrogen storage amount at 30 ° C. in 4.5) is disclosed. The effective hydrogen storage amount in this publication is a constant temperature of 30 ° C., which is different from the effective hydrogen storage amount V in the present invention. Since this publication does not show an isotherm around 100 ° C., V2 cannot be estimated. Therefore,
The effective hydrogen storage amount V under the above-mentioned conditions is unknown, and it is not suggested that this alloy is useful for applications of absorbing and releasing hydrogen under the above-mentioned conditions.

As described above, the effective hydrogen storage amount V in the range from room temperature to 100 ° C. and the atmospheric pressure to 1.0 MPa is large.
Further, a hydrogen storage alloy which can rapidly absorb and release hydrogen and is obtained from an inexpensive raw material has not yet been developed.

According to the present invention, the effective hydrogen storage amount V in the above range is
Is as large as 0.6% by mass or more, quickly absorbs and releases hydrogen,
It is an object to provide a hydrogen storage alloy which is inexpensive, lightweight, and does not deteriorate even when used repeatedly.

[0022]

According to the present invention, according to the present invention, the above-mentioned object is achieved by (1) having a composition represented by the following general formula (1),
It can absorb hydrogen under the condition of 50 ° C and hydrogen pressure 0.5-1.1MPa, release hydrogen under the condition of temperature 60 ° C-boiling point of water and hydrogen pressure 0.01-0.3MPa.
0.6% by mass or more hydrogen storage alloy.

Ca _1-x Mg _x Ni _Z (1) In the above formula, 0.60 ≦ x ≦ 0.85, 1.8 ≦ z ≦ 2.2 (2) having a composition represented by the following general formula (2) , Temperature 0
It can absorb hydrogen under the condition of 50 ° C and hydrogen pressure 0.5-1.1MPa, release hydrogen under the condition of temperature 60 ° C-boiling point of water and hydrogen pressure 0.01-0.3MPa.
0.6% by mass or more hydrogen storage alloy.

Ca _1-x Mg _x (Ni _1-y M _y ) _z (2) In the above formula, M is Al, Si, P, Cr, Mn, Fe, Co, Cu and
At least one element selected from the group consisting of Zn, which is solved by 0.60 ≦ x ≦ 0.85, 0 ≦ y ≦ 0.2, 1.8 ≦ z ≦ 2.2.

The above-mentioned effective hydrogen storage amount of 0.6% by mass or more refers to the difference between the hydrogen storage amounts when measured under the conditions of 20 ° C., 1.1 MPa and 100 ° C., 0.1 MPa.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have focused on Ca and Mg in consideration of lightness and low cost. As a result of measuring V1 and V2 of various Ca—Mg alloys, it was found that when the Ca site of CaNi ₂ was replaced with Mg, the hydrogen absorption / desorption pressure could be adjusted to control V1 and V2. In addition, Ni site is Al, Si,
At least one selected from P, Cr, Mn, Fe, Co, Cu, Zn
It has been found that one or more elements may be substituted.

The hydrogen storage alloy of the present invention has a temperature of 0 to 50 ° C.
At a hydrogen pressure of 0.5 to 1.1 MPa, hydrogen is absorbed and the temperature is
A hydrogen storage alloy for releasing hydrogen under the conditions of 60 ° C. to boiling point of water and a hydrogen pressure of 0.01 to 0.3 MPa, that is, hydrogen storage means such as a hydrogen fuel cell using (waste) hot water as a heat source, heat storage, and a heat pump. It is useful as a hydrogen storage alloy used as a thermal-chemical energy conversion means.

In the hydrogen storage alloy of the present invention having the composition represented by the above formula (1), the ratio (Z) of the Ca site and the Mg site to the Ni site slightly increases or decreases with respect to the ratio of 2 in CaNi _2. Is allowed, and 1.8 ≦ Z ≦ 2.2. If Z is less than 1.8,
CaMg _{2 which} is hard to release hydrogen precipitates as a second phase, and V2
Increase. As Z becomes greater than 2.2, V1 decreases.

The Ca site in the hydrogen storage alloy of the present invention
The Mg substitution rate (X) is preferably 0.60 ≦ X ≦ 0.85.
If X is less than 0.60, the isotherm at 100 ° C shown in FIG.
As shown in the curve of FIG.
And V2 becomes extremely large, so effective hydrogen
The storage amount V decreases. If X is less than 0.60, repeat
The alloy deteriorates significantly due to hydrogen absorption and release of X, and X is 0.60 or less.
The above can improve this. CaNi _TwoIs the half atom of Ca
The diameter is 0.197 nm, Ni is 0.125 nm, and the difference is large.
It is an unstable alloy due to compressive stress. Atomic radius 0.16
By substituting Mg of 0 nm for Ca, the compressive stress is relaxed and X
It is presumed that the effect becomes remarkable at 0.60 or more.
When the value of X is 0.60 or more, the curve shown in FIG.
The flatness of the curve of the isotherm at 100 ° C
V2 decreases, so that the effective hydrogen storage amount V increases.
Become.

It is desirable that the upper limit value of X is 0.85 or less. If X is larger than 0.85, the main phase changes from the C15-type Laves phase to the C36-type Laves phase, which is less likely to absorb hydrogen, and V1 decreases as shown in FIG.

The preferred range of the substitution rate (Y) of the Ni site in the present hydrogen storage alloy by another metal M is 0 ≦ Y ≦ 0.2.
It is. Where M is Al, Si, P, Cr, Mn, Fe, Co, C
represents one or more elements of u and Zn. If Y is larger than 0.2, a second phase that is difficult to be hydrogenated is generated, V2 increases, and the effective hydrogen storage amount V decreases significantly.

The hydrogen absorbing alloy of the present invention can be produced by any of a sintering method in which raw material powder is compacted and sintered in an inert atmosphere, and a melting method in which the raw material is melted and solidified by high-frequency heating, arc heating, or the like. Is also possible.

The alloying treatment temperature is preferably 600 ° C. to 1250 ° C. for the sintering method and 1250 ° C. or more for the melting method. In addition, as a raw material, in addition to pure metals such as Ca, Mg, and Ni, CaMg ₂ , CaNi ₂ , and a mother alloy such as MgNi ₂ can also be used, and in the case of a sintering method, a powder is preferable. However, in the case of the dissolution method, ingots other than powder can be used.

The reason why the effective hydrogen storage amount is 0.6% by mass or more is that practical use is difficult if the effective hydrogen storage amount is 0.6% by mass or less. The hydrogen storage alloy of the present invention has a temperature of 0 to 50 ° C and a hydrogen pressure of 0.5 to
It is useful for absorbing hydrogen under the conditions of 1.1 MPa and releasing hydrogen under the conditions of a temperature of 60 ° C. to the boiling point of water and a hydrogen pressure of 0.01 to 0.3 MPa.

Since the temperature during hydrogen storage is 0 to 50 ° C.,
In many areas, alloys can store hydrogen at room temperature without the need for heating or cooling. Since the hydrogen gas pressure at the time of storing hydrogen is 1.1 MPa or less, it is out of the range of the High Pressure Gas Control Law, and hydrogen gas can be handled relatively safely and easily. The lower limit of the hydrogen gas pressure during hydrogen storage may be higher than the pressure during hydrogen release, but is set to 0.5 MPa or more in consideration of the hydrogen storage amount.

Since the temperature at the time of releasing hydrogen is preferably a temperature at which hot water or waste hot water of a solar collector can be used as a heat source, the upper limit is the boiling point of water. The lower limit is preferably 60 ° C. or higher. This is because if the temperature is too low, the amount of released hydrogen decreases. The hydrogen gas pressure at the time of releasing hydrogen may be lower than the pressure at the time of occlusion, but is preferably in the range of 0.01 MPa or more and 0.3 MPa or less. If it is too high, the amount of released hydrogen is small, and if it is too low, it takes too much time to reduce the pressure. The discharge pressure is preferably set to an atmospheric pressure around 0.1 MPa, since pressurization and decompression are unnecessary and simple.

The hydrogen storage alloy of the present invention is suitable for use as a means for storing hydrogen gas as a fuel in a hydrogen fuel cell. In this case, for example, a hydrogen storage alloy can be used as follows.

Before the operation of the fuel cell, a pressurized hydrogen gas of 0.5 to 1.1 MPa is supplied to the hydrogen-absorbing alloy at room temperature at room temperature, so that the alloy stores hydrogen gas at room temperature. When operating the fuel cell, the hydrogen storage alloy is heated to 60 to 100 ° C using hot water as a heat source, and when the hydrogen gas pressure is reduced to atmospheric pressure, hydrogen gas is released. Supply at a constant flow rate. This hydrogen gas is the oxygen-containing gas supplied to the positive electrode.
It reacts with oxygen in the air (usually air) to generate electricity and turn into water.

When the release of the hydrogen gas is completed, the temperature of the hydrogen storage alloy is lowered to room temperature, and the above-described pressurized hydrogen gas is supplied again to store the hydrogen gas in the alloy. By installing a plurality of hydrogen storage containers made of a hydrogen storage alloy and using them alternately, the hydrogen fuel cell can be operated continuously.

The type of hydrogen fuel cell is not particularly limited as long as it uses hydrogen as fuel. It can be applied to any of alkali type, solid polymer electrolyte type, phosphoric acid type, molten carbonate type, solid electrolyte type, etc. which are currently under development. Among them, a solid polymer electrolyte fuel cell which can be operated at room temperature and can use air as an oxygen supply source is preferable. The polymer electrolyte fuel cell can be a compact battery that operates at 100 ° C or lower, and has been put into practical use as a small-scale regional power generation system or a home power generation system. .

The hydrogen storage alloy of the present invention can be used for heat storage or heat pump as a means for converting heat to chemical energy. Also in this case, the conditions of the temperature and the hydrogen gas pressure at the time of storing and releasing hydrogen may be the same as those described above.

The hydrogen storage alloy of the present invention gives a large effective hydrogen storage amount of 0.6% by mass or more when hydrogen is stored and released under the above-described conditions, so that it is necessary to store a predetermined amount of hydrogen. The amount of the hydrogen storage alloy can be reduced, and the device can be downsized. In addition, absorption and release of hydrogen occur quickly. Furthermore, since it is a lightweight and low-cost alloy because it contains a large amount of Ca and Mg, it is suitable for mass use.

[0043]

EXAMPLE Ca, Mg, Ni and optionally Al or
Using Cr as a raw material, a sample of a hydrogen storage alloy was prepared by a sintering method or a melting method as described below. The raw materials used were all commercial products having a purity of 99% by mass or more. In both the sintering method and the melting method, all operations were performed in an argon atmosphere.

Raw materials for preparing a hydrogen storage alloy sample by a sintering method were weighed and blended so as to have a predetermined composition, and pulverized in a mortar to obtain a mixed powder having a particle size of 100 μm or less. Using a hydraulic press with a load of 9.8 MPa, the mixed powder was 10 mm in diameter ×
It was formed into a pellet having a thickness of 5 mm to obtain a green compact. The obtained green compact was heated at 900 ° C. for 2 hours using an electric resistance furnace, sintered and alloyed. The obtained sintered body is treated with a particle size of 100.
The powder was crushed in a mortar until the powder became not more than μm.

Using this powder, the steps of molding, sintering and pulverization were repeated once again to obtain a powdery hydrogen storage alloy sample. The powder of each composition was subjected to wet chemical analysis to determine the ratio of each element in the sample. As a result, it was confirmed that there were no elements volatilized during sintering, and the desired alloy composition was obtained.

The raw materials for preparing the hydrogen storage alloy sample by the melting method were weighed and blended so as to have a predetermined composition, each sample was melted in a vacuum high-frequency melting furnace by about several kg, and the thickness was reduced into a flat water-cooled mold. A molten sample was prepared by casting to a thickness of 1 to 2 cm. Chemical analysis of the prepared alloy sample powder by wet method,
The ratio of each element in the sample was determined. Thereafter, the alloy sample was pulverized to a size of about several cm square, and subjected to a heat treatment at 800 ° C. for 10 hours in an argon stream. Also in this sample, there was no element volatilized during melting and heat treatment, and the desired alloy composition was obtained.

Table 1 shows the composition of the hydrogen storage alloy thus produced and the production method. The structure of each hydrogen storage alloy sample shown in Table 1 was examined by X-ray diffraction. As a result, it was found that the structure had a C15 Laves structure as the main phase when the Mg substitution ratio of the Ca site was 0.85 or less. did. On the other hand, when X was larger than 0.85, the structure was found to have a C36 Laves phase as a main phase.

After confirming the above, the hydrogen storage amounts V1 and V2 were measured under the conditions shown in Table 1 using a Geebelt type hydrogen storage amount measuring device, and the effective hydrogen storage amount V = V1−
V2 was determined. The values of V1, V2, and V are also shown in Table 1.

[0049]

[Table 1] From Table 1, depending on the composition of the alloy, the values of V1 and V2 change variously, but the effective hydrogen storage amount V calculated as V1−V2 is determined when the hydrogen storage alloy has a composition within the range of the present invention. As a result, the hydrogen storage alloy of the present invention has a large effective hydrogen storage amount that can be actually used and has high practicality. In addition, the effect of the present invention that the effective hydrogen storage amount V was large was obtained regardless of whether the alloy was manufactured by the sintering method or the melting method.

As can be seen from a comparison between the example and the comparative example, when _{X of} Ca _1-x Mg _x (Ni _1-y M _y ) _z is less than 0.60, V 2 increases, so that the effective hydrogen storage amount decreases. Is declining. When X is larger than 0.85, the main phase has a C36 Laves structure which is hard to occlude hydrogen, and therefore, in Comparative Example 15, V1 is remarkably reduced and effective hydrogen storage amount is also reduced as compared with Example 8 of the present invention. .

In Comparative Examples 16 and 17 in which Y of Ca _1-x Mg _x (Ni _1-y M _y ) _z is out of the range of the present invention, the ratio of the second phase which is hard to absorb hydrogen is increased, As a result of the remarkable decrease in V1, the effective hydrogen storage amount was reduced.

Comparative Example 13 in which Z of Ca _1-x Mg _x (Ni _1-y M _y ) _z is smaller than the range of the present invention is a subphase CaMg in which hydrogen is hardly released.
₂ increased, V2 increased, and the effective hydrogen storage amount decreased. In Comparative Example 14 where Y was larger than the range of the present invention, the ratio of the Ni phase, which was difficult to store hydrogen, increased, V1 decreased, and the effective hydrogen storage amount decreased.

[0053]

The hydrogen storage alloy according to the present invention is lighter and less expensive than conventional materials, and is easy to use when hot water is used as a heating source, in the range of normal temperature to 100 ° C. and atmospheric pressure to 1.0 MPa. Since the effective hydrogen storage capacity at this point is greater than this conventional material,
It is a hydrogen storage alloy suitable for practical use. Therefore, the hydrogen storage alloy of the present invention is useful for applications such as a hydrogen storage container as a hydrogen supply source of a hydrogen fuel cell, a heat pump, and heat storage.
In addition, a refrigerant is not required at the time of storing hydrogen, and waste hot water can be used at the time of releasing hydrogen, so that it is possible to advantageously cope with environmental problems.

[Brief description of the drawings]

FIG. 1 is a pressure-composition isotherm diagram showing a concept of an effective hydrogen storage amount V.

FIG. 2 is a pressure-composition isotherm at a temperature of 100 ° C. when the Mg substitution ratio X of Ca sites is 0.65 and 0.50 in a hydrogen storage alloy having a composition of Ca _1-x Mg _x Ni ₂ .

FIG. 3 is a pressure-composition isotherm diagram at a temperature of 20 ° C. in a hydrogen storage alloy having a composition of Ca _1-x Mg _x Ni _{2 when} the Mg-substitution ratio X of Ca site is 0.90 and 0.65. Show.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoshi Maeda 1-8 Fuso-cho, Amagasaki-shi, Hyogo Sumitomo Metal Industries, Ltd. Inside Electronics Technology Research Laboratory (72) Inventor Kouji Yonemura 1-8 Fuso-cho, Amagasaki-shi, Hyogo No. Sumitomo Metal Industries, Ltd. Electronics Technology Research Laboratories (72) Inventor Takashi Terashita 5-9-6, Tokodai, Tsukuba City, Ibaraki Pref. Japan Heavy Industries, Ltd. Tsukuba Research Laboratories (72) Inventor Seiji Takahashi Tsukuba, Ibaraki Pref. 5-9-6 Tokodai, Tsukuba-shi, Japan Tsukuba Research Laboratories, Japan (72) Inventor Koji Sasai 5-9-6 Tokodai, Tsukuba-shi, Ibaraki Pref. Reference) 5H027 AA02 AA03 AA04 AA05 AA06 BA14

Claims (2)

[Claims] (1) having a composition represented by the following general formula (1),
Absorbs hydrogen under the conditions of temperature 0 to 50 ° C and hydrogen pressure 0.5 to 1.1MPa, temperature 60 ° C to boiling point of water, hydrogen pressure 0.01 to 0.3MPa.
A hydrogen storage alloy capable of releasing hydrogen under the following conditions and having an effective hydrogen storage amount of 0.6% by mass or more. Ca _1-x Mg _x Ni _z・ ・ ・ (1) In the above formula, 0.60 ≦ x ≦ 0.85, 1.8 ≦ z ≦ 2.2 2. Absorbing hydrogen under the conditions of a temperature of 0 to 50 ° C. and a hydrogen pressure of 0.5 to 1.1 MPa having a composition represented by the following general formula (2), a temperature of 60 ° C. to a boiling point of water and a hydrogen pressure of 0.01-0.
A hydrogen storage alloy that can release hydrogen under 3MPa conditions and has an effective hydrogen storage amount of 0.6% by mass or more. Ca in _{1-x Mg x (Ni 1} -y M y) z ····· (2) the above formula, M is Al, Si, P, Cr, Mn, Fe, Co, from the group consisting of Cu and Zn At least one selected element, 0.60 ≦ x ≦ 0.85, 0 ≦ y ≦ 0.2, 1.8 ≦ z ≦ 2.2