JP2000336444A - Hydrogen storage alloy and hydrogen feeding system using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the amt. of available hydrogen to be occluded in the alloy and its reaction rate with hydrogen and to prolong its cycle life by allowing it to have a Laves phase structure and a specified compsn. composed of Zr, Hf, Ti, Mn, Cr, Nb, Ni and C. SOLUTION: This hydrogen storage allay is expressed by the formula of (ZaHfgTi1-a-g)MnbCrcNbdNieCf. In the formula, 0.7<=a<=0.9, 0.6<=b<=0.8, 0<=c<=0.2, 0.1<=d<=3, 0.8<=e<=1.2, 0<=f<=0.03 and 0<=g<=0.01 are satisfied, and also, 1.8<=b+c+d+e+f<=2.2 is satisfied. In this alloy, its plateau pressure can be controlled to <=10 atmospheric pressure at room temp. Moreover, it has characteristics of good plateau flatness, a high amt. of available hydrogen to be occluded, a high reaction rate with hydrogen, a long cycle life or the like and is therefore preferably applicable as a hydrogen feeding system, particularly as a hydrogen feeding source of a fuel battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy capable of reversibly storing and releasing hydrogen, and a hydrogen supply system using the same.

[0002]

2. Description of the Related Art In general, a fuel cell has a high power generation efficiency because a fuel such as hydrogen is chemically reacted with oxygen to directly convert chemical energy into electric energy. Further, since the fuel cell has a small number of mechanical driving units, the noise is extremely low and the size can be reduced. Since such a fuel cell is relatively easy to install and operate, it is used as a distributed power supply or a power supply for communication equipment.

In recent years, fuel cells and hydrogen storage alloys have been combined.
Fuel cell system used as a portable power source
Have been. MmNi as a hydrogen supply source for fuel cells
_4.8Mn_0.2Alloy, Ca_0.7Mm_0.3Ni_4.8Al_0.2Alloy
Which AB_FiveType alloy, TiFe_{0. 8}Mn_0.2AB such as alloy
Mold alloy, Ti_1.2Cr_1.2Mn_0.8AB such as alloy_TwoType color
Beth phase alloy (JP-A-4-181659) and further
Is a Ti—Cr—V alloy (5 <Ti (at%) <60;
10 <Cr (at%) <80, 10 <V (at%) <8
0) and other hydrogen storage alloys have been proposed.
(Japanese Patent Application Laid-Open No. 9-31585).

However, MmNi_4.8Mn_0.2Alloy, Ca
_0.7Mm_0.3Ni_4.8Al_0.2AB such as alloy_FiveMold alloy, T
ife_0.8Mn_0.2AB type alloy such as alloy, Ti_1.2Cr
_1.2Mn_{0 .8}AB such as alloy_TwoType Laves phase alloy
Alloy material whose composition is determined in view of toe pressure control
Water, which is one of the most necessary properties
Element storage is not very high. In addition, mainly
Hydrogen absorption of VCrTi-based alloy with one crystal structure part
Although the storage amount is 3.6% by weight, the hydrogen pressure composition isotherm
The plateau is two steps. And the first plateau
Effective because the pressure is much lower than the practical pressure
Storage and release of hydrogen is limited to the second stage and can be used effectively
The effective hydrogen storage amount is 2.1% by weight. In addition, VCr
Ti-based alloys have a relatively slow reaction rate with hydrogen,
The problem is that the cycle life associated with occlusion and release is short.
Yes, and have not yet reached a practical level.

In the field of hydrogen sources for fuel cells,
The volume of the hydrogen source is a technically important factor. Therefore, the amount of hydrogen that can be absorbed and released by a fixed volume of alloy, that is, the effective hydrogen storage amount of the alloy is important. Further, practically, it is required that the reaction rate with hydrogen is high and the cycle life is long.

[0006]

When a hydrogen storage alloy is used, first, it is desired that the hydrogen storage / release capability at the operating temperature is large. However, said AB ₅ type, AB
And AB ₂ type alloys are intended to set the supply pressure of hydrogen to the fuel cell to 10 atm or less, and under these pressures, all alloys have insufficient effective hydrogen storage capacity. The effective hydrogen storage capacity of VCrTi based alloy is 2.1 wt%, AB ₅ type, AB-type, A
Higher than the B ₂ type alloys, but relatively slow rate of reaction with hydrogen, there is a problem that shorter cycle life.

The present invention has been made in view of the above points, and has been made in view of the above circumstances. A hydrogen storage alloy having a high effective hydrogen storage amount, a high reaction rate with hydrogen, and a long cycle life, and a hydrogen supply using the same are provided. It is an object to provide a system. For example, when the hydrogen storage alloy of the present invention is applied to a fuel cell, an excellent hydrogen supply system is obtained.

[0008]

Means for Solving the Problems The present invention has a Laves phase structure, Formula _{(1): (Zr a Hf} g Ti 1-ag) Mn b Cr c Nb d Ni e C f (1) ( Formula Where a to g are 0.7 ≦ a ≦ 0.9, 0.6 ≦ b ≦
0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8
≦ e ≦ 1.2, 0 ≦ f ≦ 0.03, 0 ≦ g ≦ 0.1,
It satisfies 1.8 ≦ b + c + d + e + f ≦ 2.2. )). In addition, the present invention provides a hydrogen storage alloy in which f = 0 and 0 ≦ g ≦ 0.1, a hydrogen storage alloy where 0.01 ≦ f ≦ 0.03 and g = 0, and The present invention relates to a hydrogen supply system using a storage alloy.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As an alloy having a high effective hydrogen storage capacity, a high reaction rate with hydrogen and a long cycle life, AB
There is a type ₂ Laves phase alloy. Among the AB ₂ type Laves phase alloys, (ZrTi) (MnC) is particularly preferred from the viewpoints of control of plateau pressure, effective hydrogen storage amount, and plateau flatness.
rNbNi) _2- base Laves phase alloy, (ZrHfTi)
(MnCrNbNi) _2- based Laves phase alloy and (Zr
Ti) (MnCrNbNiC) _2- based Laves phase alloy is selected as preferred. The present inventors have designed and manufactured various new alloys having different compositions in these alloy systems while adding the above metallographic considerations, and measured the hydrogen storage characteristics. _{1): (Zr a Hf g} Ti 1-ag) Mn b Cr c Nb d Ni e C f (1) ( wherein, a to g are, 0.7 ≦ a ≦ 0.9,0.6 ≦ b ≤
0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8
≦ e ≦ 1.2, 0 ≦ f ≦ 0.03, 0 ≦ g ≦ 0.1,
It satisfies 1.8 ≦ b + c + d + e + f ≦ 2.2. ) Was found to be excellent as a hydrogen storage alloy for a hydrogen supply system.

[0010] The plateau pressure of the hydrogen storage alloy at room temperature (27 ° C) can be controlled to 10 atm or less. Further, the hydrogen storage alloy has good plateau flatness, a high effective hydrogen storage amount, a high reaction rate with hydrogen, and a long cycle life. In view of the above characteristics, the hydrogen storage alloy is preferably applied as a hydrogen supply system, particularly as a hydrogen supply source for a fuel cell.
In the formula (1), if a falls outside the above range, the plateau pressure becomes 10 atmospheres or more or 1 atmosphere or less. When the plateau flatness or hysteresis becomes poor, and d is out of the above range, the maximum hydrogen storage amount is reduced. Deviates from the range, the maximum hydrogen storage amount decreases, and when g is out of the range, the maximum hydrogen storage amount decreases. Further, from the viewpoint that a better plateau flatness can be obtained and a large effective hydrogen storage amount can be obtained, a to g are respectively 0.77 ≦ a ≦ 0.82 and 0.68 ≦ b ≦
0.72, 0.08 ≦ c ≦ 0.10, 0.15 ≦ d ≦
0.25, 0.95 ≦ e ≦ 1.05, 0 ≦ f ≦ 0.01
5, it is preferable that 0 ≦ g ≦ 0.06.

The effective hydrogen storage amount refers to the amount of hydrogen that can be reversibly stored by the hydrogen storage alloy per unit volume. The effective hydrogen storage amount is defined as the effective and stable hydrogen release pressure range of 1
Assuming that the pressure is 10 to 10 atm, for example, in the hydrogen pressure composition isotherm diagram showing the relationship between the hydrogen storage amount per unit volume and the hydrogen equilibrium pressure as shown in FIGS. Of hydrogen per unit volume and the hydrogen storage amount per unit volume when the hydrogen equilibrium pressure is 1 atm.

The rate of reaction with hydrogen is as follows.
It refers to the rate at which hydrogen reacts with the hydrogen gas and stores the hydrogen and the rate at which the stored hydrogen is released. The rate of reaction with hydrogen is, for example,
The time required to occlude 80% of the effective hydrogen storage capacity measured using a general reaction rate measuring device, and the time required to release 80% of the effective hydrogen storage capacity as in the examples described later. Can be indicated by

The cycle life is evaluated based on the rate of deterioration of the effective hydrogen storage amount of the hydrogen storage alloy due to repeated storage and release of hydrogen.

In the formula (1), in particular, f = 0 and g = 0
Alloys, i.e., formula (2): in _{(Zr a Ti 1-a)} Mn b Cr c Nb d Ni e (2) ( wherein, a to e is, 0.7 ≦ a ≦ 0.9,0.6 ≦ b ≦
0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8
≤ e ≤ 1.2 and 1.8 ≤ b + c + d + e ≤ 2.2. The alloy represented by ()) is particularly suitable as a general-purpose hydrogen supply system for fuel cells from the viewpoint of alloy production cost. In the formula (2), when a to e are out of the above range,
The effective hydrogen storage capacity of the alloy decreases.

The alloy represented by the formula (2) has an effective hydrogen storage amount of 1400 mL / cm ³ or more,
A value of 00 to 1440 mL / cm ³ can be taken.
For example, in the embodiment described later, the value is 1420 mL / c.
m is ^3. This alloy has an effective hydrogen storage capacity of 80%.
% Or less, more preferably 5 to 10 seconds as the time required to occlude%, 15 seconds or less as the time required to release 80% of the effective hydrogen storage amount, and more preferably 10 to 1
The value of 5 seconds can be taken as a deterioration rate of 8% or less, and further, a value of 2 to 8% as a deterioration rate in an example described later.

In the formula (1), in particular, f = 0,
0 <g ≦ 0.1 alloy, i.e. the formula _{(3): (Zr a Hf} g Ti 1-ag) Mn b Cr c Nb d Ni e (3) ( wherein, a to e and g are 0. 7 ≦ a ≦ 0.9, 0.
6 ≦ b ≦ 0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.
3, 0.8 ≦ e ≦ 1.2, 0 <g ≦ 0.1, 1.8 ≦ b
+ C + d + e ≦ 2.2 is satisfied. The alloy represented by)
In addition to Zr, Ti, Mn, Cr, Nb and Ni, H
Since it contains f, it is more preferable than the alloy represented by the formula (2) in terms of hysteresis characteristics. This alloy is suitable from the viewpoint of low hysteresis characteristics, particularly as a hydrogen supply system for a fuel cell in which an increase in the pressure in the container needs to be suppressed as much as possible. In the formula (3), when a to e are out of the above range, the effective hydrogen storage amount of the alloy decreases, and when g exceeds 0.1, the hysteresis of the alloy increases and the maximum hydrogen storage amount decreases.

The alloy represented by the formula (3) has an effective hydrogen storage amount of 1410 mL / cm ³ or more,
Values of 10 to 1450 mL / cm ³ can be taken.
For example, in the embodiment described later, the value is 1430 mL / c.
m is ^3. This alloy has an effective hydrogen storage capacity of 80%.
% Or less, and more preferably 5 to 10 seconds as the time required to occlude%, 15 seconds or less as the time required to release 80% of the effective hydrogen storage amount, and even 10 to 1
The value of 5 seconds can be taken as a deterioration rate of 8% or less, and further, a value of 2 to 8% as a deterioration rate in an example described later.

In the formula (1), in particular, 0.01
≦ f ≦ 0.03, g = 0 the alloy, i.e. the formula _{(4): (Zr a Ti} 1-a) Mn b Cr c Nb d Ni e C f (4) ( wherein, a to f is 0 0.7 ≦ a ≦ 0.9, 0.6 ≦ b ≦
0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8
≦ e ≦ 1.2, 0.01 ≦ f ≦ 0.03, 1.8 ≦ b +
It satisfies c + d + e + f ≦ 2.2. The alloy represented by the formula (2) further contains C (carbon) in addition to Zr, Ti, Mn, Cr, Nb, and Ni, so that the effective hydrogen storage amount is more than that of the alloy represented by the formula (2). This is preferable in terms of increasing the size. This alloy is suitable for a hydrogen supply system for a fuel cell, in which the amount of stored hydrogen per volume needs to be increased as much as possible, in particular, because the effective hydrogen storage amount is large. In the formula (4), when a to e are out of the above range, the effective hydrogen storage amount of the alloy decreases, and when f is smaller than 0.01, the effect of further improving the effective hydrogen storage amount of the alloy decreases, and f Is greater than 0.03, the maximum hydrogen storage capacity of the alloy decreases.

The alloy represented by the formula (4) has an effective hydrogen storage capacity of 1430 mL / cm ³ or more,
Values of 30-1470 mL / cm ³ can be taken.
For example, in the embodiment described later, the value is 1450 mL / c.
m is ^3. This alloy has an effective hydrogen storage capacity of 80%.
%, A value of 12 seconds or less, more preferably 6 to 12 seconds, as a time required for releasing 80% of the effective hydrogen storage amount, and a value of 6 to 12 seconds, and further, 12 to 1
The value of 8 seconds can be taken as a deterioration rate of 10% or less, and further, a value of 4 to 10% in the examples described later.

The hydrogen storage alloy according to the present invention comprises Zr, H
The necessary raw materials are selected and weighed from each of the metals f, Ti, Mn, Cr, Nb, and Ni and the compound TiC, and they can be obtained by melting and alloying together in an arc melting furnace in an argon atmosphere. At that time, it is preferable to re-melt the ingot about five times while inverting the ingot up and down so that the alloy is homogeneously formed. The obtained button ingot is heat-treated at 1100 to 1250 ° C for 6 to 24 hours by a conventional method.

[0021]

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

First, evaluation methods used in the following examples and comparative examples will be described below.

(Measurement of Effective Hydrogen Storage Amount) The effective hydrogen storage amount is defined as the hydrogen equilibrium pressure in the hydrogen pressure composition isotherm diagram showing the relationship between the hydrogen storage amount per unit volume and the hydrogen equilibrium pressure.
It was determined from the difference between the hydrogen storage amount per unit volume at 0 atm and the hydrogen storage amount per unit volume at a hydrogen equilibrium pressure of 1 atm.

The hydrogen pressure composition isotherm was measured by the vacuum origin method. This is a method of activating a sample and measuring the amount of dissolved hydrogen in a vacuum degassed state as zero. The activation of the alloy was performed by repeating three cycles of storing and releasing hydrogen at room temperature.

(Measurement of Reaction Rate with Hydrogen) The reaction rate with hydrogen was determined by quantifying the rate at which a given alloy reacted with hydrogen gas and absorbed hydrogen using a reaction rate measuring device. . Specifically, after the sample is dehydrogenated, the accumulator is filled with hydrogen at a predetermined pressure, hydrogen is absorbed, and the relationship between the change in hydrogen pressure and time is recorded.
The amount of hydrogen reacted with the sample was plotted on the y-axis and determined from these relationships. Here, as a representative value for evaluating the reaction rate, the time required for storing 80% of the effective hydrogen storage amount and the time required for releasing 80% of the effective hydrogen storage amount were determined.

(Measurement of cycle life) Using a thermal cycle life test apparatus, the lower limit temperature was set at 10 ° C and the upper limit temperature was set at 80 ° C.
℃, the time required per cycle is 500 seconds,
The rate of deterioration (%) of the effective hydrogen storage capacity of a given alloy when heating and cooling were repeated 10,000 cycles was determined. The lower the deterioration rate, the longer the cycle life.

Example 1 One of the alloys represented by the formula (2)
In the formula, Zr _0.8 Ti _0.2 Mn _0.7 Cr _0.1 Nb _0.2
An alloy represented by Ni _1.0 was produced by the following procedure. First, a predetermined amount of each of Zr, Ti, Mn, Cr, Nb, and Ni was weighed and melted together in an arc melting furnace in an argon atmosphere to form an alloy. At that time, the ingot was re-melted about five times while inverting the ingot up and down so as to form a homogeneous alloy. The obtained button ingot was heat-treated at 1100 ° C. for 24 hours and then pulverized to obtain a hydrogen pressure composition isotherm measurement sample. Using the obtained sample, the effective hydrogen storage amount, the reaction rate with hydrogen, and the cycle life were measured in accordance with the above-mentioned method.

FIG. 1 is a hydrogen pressure composition isotherm at room temperature of the alloy of this embodiment. The horizontal axis indicates the hydrogen storage amount per unit volume, and the vertical axis indicates the hydrogen equilibrium pressure. FIG.
Shows that this alloy has excellent plateau flatness. The effective hydrogen storage amount is 1420 mL / cm
^{Was 3} . The effective hydrogen storage capacity per unit volume of the conventional VCrTi-based alloy was 1420 m
L / cm ³ , which was the same as the value of the alloy of this example.

On the other hand, this alloy accounts for 80% of the effective hydrogen storage amount.
The time required to store hydrogen is 5 seconds, and the effective hydrogen storage amount is 8 seconds.
The time required to release 0% was 10 seconds, indicating that the reaction rate with hydrogen was high. This reaction rate is La
This level is equivalent to the reaction rate of the Ni ₅ alloy.

The deterioration rate indicating the cycle life was 5%, indicating that the cycle life of this alloy was long.

Incidentally, all the alloys having compositions close to the alloy composition of the present example showed similar results. That is,
Formula is represented by _{(Zr a Ti 1-a)} Mn b Cr c Nb d Ni e,
0.7 ≦ a ≦ 0.9, 0.6 ≦ b ≦ 0.8, 0 ≦ c ≦
0.2, 0.1 ≦ d ≦ 0.3, 0.8 ≦ e ≦ 1.2,
When the same measurement was performed for other alloys satisfying 1.8 ≦ b + c + d + e ≦ 2.2, the variation between the plateau pressure of the alloy of the present embodiment and the plateau pressure of these alloys was about 2 atm. Was. The effective hydrogen storage capacity of these alloys is 1
In the range of 400 to 1440 mL / cm ³ ,
Falls outside the above range, the effective hydrogen storage amount sharply decreased.

Example 2 Zr, Hf, T
The same operation as in Example 1 was performed except that a predetermined amount of each metal of i, Mn, Cr, Nb and Ni was weighed, and as one of the alloys represented by the formula (3), the formula: Zr _0.775 Hf _0.05 T
It manufactures i _0.175 Mn _0.7 Cr _0.1 Nb _0.2 alloy represented by Ni _1.0, and hydrogen pressure composition isotherm measurement sample. Using the obtained sample, the effective hydrogen storage amount, the reaction rate with hydrogen, and the cycle life were measured in accordance with the above-mentioned method.

FIG. 2 is a hydrogen pressure composition isotherm diagram at room temperature of the alloy of this embodiment. FIG. 2 shows that this alloy has excellent plateau flatness. Further, the effective hydrogen storage amount of this alloy was slightly increased to 1430 mL / cm ³ compared to the alloy of Example 1 due to the effect of further improving the plateau flatness due to the addition of Hf. This value is larger than the effective hydrogen storage capacity of the VCrTi-based alloy.

On the other hand, this alloy accounts for 80% of the effective hydrogen storage capacity.
The time required to store hydrogen is 5 seconds, and the effective hydrogen storage amount is 8 seconds.
The time required to release 0% was 10 seconds, indicating a fast reaction rate. This reaction rate is at the same level as the reaction rate of the LaNi ₅ alloy.

The deterioration rate indicating the cycle life was 5%, indicating that the cycle life of this alloy was long.

Incidentally, all the alloys having compositions close to the alloy composition of the present example showed similar results. That is,
Formula is represented by _{(Zr a Hf g Ti 1-} ag) Mn b Cr c Nb d Ni e, 0.7 ≦ a ≦ 0.9,0.6 ≦ b ≦ 0.8,0
≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8 ≦ e ≦ 1.
2, 0 <g ≦ 0.1, 1.8 ≦ b + c + d + e ≦ 2.2
When the same measurement was performed for other alloys satisfying the above, the variation between the plateau pressure of the alloy of the present example and the plateau pressure of these alloys was about 2 atm. The effective hydrogen storage amounts of these alloys were in the range of 1410 to 1450 mL / cm ³ , but when a to e were out of the above range, the effective hydrogen storage amounts decreased sharply. When g exceeded 0.1, the effective hydrogen storage amount of the alloy decreased.

Example 3 As raw materials, Zr, Ti, M
n, Cr, Nb, Ni metal and compound TiC
Except for the quantitative weighing, the same operation as in Example 1 was performed, and the equation
As one of the alloys represented by (4), the formula: Zr_0.8Ti
_0.2Mn_0.7Cr_0.1Nb_0.2Ni_0.985C_{0.01 Five}Represented by
An alloy was manufactured and used as a hydrogen pressure composition isotherm measurement sample. Get
Using the obtained sample, the effective hydrogen storage amount according to the above method,
The rate of reaction with hydrogen and the cycle life were measured.

FIG. 3 is a hydrogen pressure composition isotherm at room temperature of the alloy of this embodiment. FIG. 3 shows that this alloy has excellent plateau flatness. Further, the effective hydrogen storage amount of this alloy is larger than that of the alloy of Example 1 due to the effect of increasing the maximum hydrogen storage amount by the addition of C.
It was 0 mL / cm ³ . This value is larger than the effective hydrogen storage capacity of the VCrTi-based alloy.

On the other hand, this alloy accounts for 80% of the effective hydrogen storage amount.
The time required to occlude hydrogen was 6 seconds, and the effective hydrogen occlusion amount was 8 seconds.
The time required to release 0% was 12 seconds, indicating a fast reaction rate. This reaction rate is at a level equivalent to the reaction rate of the LaNi ₅ alloy.

Further, the deterioration rate indicating the cycle life was 6%, indicating that the cycle life of this alloy was long.

Incidentally, all the alloys having compositions close to the alloy composition of the present example showed similar results. That is,
_{Formula: (Zr a Ti 1-a} ) is represented by _{Mn b Cr c Nb d Ni e} C f, 0.7 ≦ a ≦ 0.9,0.6 ≦ b ≦ 0.8,0 ≦ c
≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8 ≦ e ≦ 1.2,
0.01 ≦ f ≦ 0.03, 1.8 ≦ b + c + d + e + f
When other alloys satisfying ≤ 2.2 were measured in the same manner as described above, the variation between the plateau pressure of the alloy of the present embodiment and the plateau pressure of these alloys was about 2 atm. The effective hydrogen storage capacity of these alloys is 1430-1470 mL / c
Although it was in the range of m ³ , when a to e were out of the above range, the effective hydrogen storage amount rapidly decreased. Further, when f was smaller than 0.01, the effect of further improving the effective hydrogen storage amount of the alloy was reduced, and when f was larger than 0.03, the effective hydrogen storage amount of the alloy was reduced.

These results indicate that the use of the hydrogen storage alloy according to the present invention, which simultaneously satisfies the effective hydrogen storage amount, the reaction rate with hydrogen, and the cycle life at a high level, makes it possible to operate for a longer time than in the past. This shows that a high-performance fuel cell system can be obtained.

Although the above embodiment is based on the assumption of a hydrogen supply source suitable for a fuel cell, any hydrogen source used at room temperature and 10 atm or less can be used without departing from the gist of the present invention. The hydrogen storage alloy of the present invention can also be used in the supply system, and the same effect is exerted. In the present embodiment, the Laves phase alloy in which b + c + d + e + f = 2 is mainly described, but 1.8 ≦ b + c + d + e + f ≦
2.2, that is, b + c + d + e + within the solid solution limit
The same effect can be obtained even if f = 2.

[0044]

According to the present invention, hydrogen having a hydrogen plateau pressure of 10 atm or less, a high effective hydrogen storage capacity, a high reaction rate with hydrogen, a long cycle life, and particularly a hydrogen suitable for a fuel cell. A hydrogen storage alloy for a supply system can be obtained. The main reason is that the alloy composition was designed and optimized from the viewpoint of plateau pressure and plateau flatness. By using the hydrogen storage alloy for a hydrogen supply system of the present invention, it is possible to improve the performance of a fuel cell in which a hydrogen supply source is required to have a higher hydrogen storage / release capability than before.

[Brief description of the drawings]

FIG. 1 is a hydrogen pressure composition isotherm diagram at room temperature of a hydrogen storage alloy according to one embodiment of the present invention.

FIG. 2 is a hydrogen pressure composition isotherm diagram at room temperature of a hydrogen storage alloy according to another embodiment of the present invention.

FIG. 3 is a hydrogen pressure composition isotherm at room temperature of a hydrogen storage alloy according to still another embodiment of the present invention.

Continued on the front page (72) Inventor Yoshiaki Yamamoto 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H027 AA02 BA14

Claims (4)

[Claims] 1. A has a Laves phase structure, Formula _{(1): (Zr a Hf} g Ti 1-ag) Mn b Cr c Nb d Ni e C f (1) ( wherein, a to g is 0 0.7 ≦ a ≦ 0.9, 0.6 ≦ b ≦
0.8, 0 ≦ c ≦ 0.2, 0.1 ≦ d ≦ 0.3, 0.8
≦ e ≦ 1.2, 0 ≦ f ≦ 0.03, 0 ≦ g ≦ 0.1,
It satisfies 1.8 ≦ b + c + d + e + f ≦ 2.2. A hydrogen storage alloy represented by). 2. The method according to claim 1, wherein f = 0 and 0 ≦ g ≦ 0.1.
The hydrogen storage alloy according to item 1. 3. The hydrogen storage alloy according to claim 1, wherein 0.01 ≦ f ≦ 0.03 and g = 0. 4. A hydrogen supply system using the hydrogen storage alloy according to claim 1.