Catalyzed hydrogen desorption in Mg-based hydrogen storage material and methods for production thereof

Abstract

A magnesium-based hydrogen storage material including magnesium or a magnesium-based hydrogen storage alloy and a hydrogen desorption catalyst which is insoluble in said magnesium-based hydrogen storage alloy and is in the form of: 1) discrete dispersed regions of catalytic material in the bulk of said magnesium or magnesium-based hydrogen storage alloy; 2) discrete dispersed regions on the surface of particles of said magnesium or magnesium-based hydrogen storage alloy; 3) a continuous or semi-continuous layer of catalytic material on the surface of said magnesium or magnesium-based hydrogen storage alloy which is in bulk or particulate form; or 4) combinations thereof. Methods of producing the material are also disclosed.

Description

FILED OF THE INVENTION [0001] The instant invention relates generally to hydrogen storage materials and more specifically magnesium-based hydrogen storage materials in which hydrogen desorption is catalyzed by materials which are insoluble in said magnesium-based hydrogen storage material. The insoluble catalytic material may be in the form of: 1) discrete dispersed regions of catalytic material in a hydrogen storage material bulk; 2) discrete dispersed regions on the surface of particles of the hydrogen storage material; 3) a continuous or semi-continuous layer of catalytic material on the surface of bulk or particulate hydrogen storage material; or 4) combinations thereof. BACKGROUND OF THE INVENTION [0002] Growing energy needs have prompted specialists to take cognizance of the fact that the traditional energy resources, such as coal, petroleum or natural gas, are not inexhaustible, or at least that they are becoming costlier all the time, and that it is advisable to consider rep...

AI Technical Summary

Benefits of technology

[0058] The catalyst may be distributed in multiple ways by combining the above techniques. The bulk or particulate magnesium or magnesium-based hydrogen storage alloy may be produced by; a) forming a melt of said magnesium or magnesium-based hydrogen s

Problems solved by technology

One of the problems posed by the use of hydrogen is its storage and transportation.

Hydrogen may be stored under high pressure in steel cylinders, but this approach has the drawback of requiring hazardous and heavy containers which are difficult to handle (in addition to having a low storage capacity of about 1% by weight).

Hydrogen may also be stored in cryogenic containers, but this entails the disadvantages associated with the use of cryogenic liquids; such as, for example, the high cost of the containers, which also require careful handling.

Although this property and the relatively low price of magnesium make the MgH2—Mg seem the optimum hydrogen storage system for transportation, for hydrogen-powered vehicles that is, its unsatisfactory kinetics have prevented it from being used up to the present time.

Moreover, the hydrogen storage capacity of a magnesium reserve diminishes during the charging / discharging cycles.

The high temperature level and the high energy requirement for expelling the hydrogen have the effect that, for example, a motor vehicle with an internal combustion engine, cannot exclusively be operated from these alloys.

For example, this alloy can be titanium / iron hydride (a typical low-temperature hydride store) which can be operated at temperatures down to below 0° C. These low-temperature hydride alloys have the disadvantage of having a low hydrogen storage capacity.

In addition to this relatively low storage capacity, these alloys also have the disadvantage that the price of the alloy is very high when metallic vanadium is used.

Although alloys of this type have a greater storage capacity for hydrogen than the alloy according to U.S. Pat. No. 4,160,014, hereby incorporated by reference, they have the disadvantage that temperatures of at least 250° C. are necessary in order to completely expel the hydrogen.

However, a high discharge capacity, particularly at low temperatures, is frequently necessary in industry because the heat required for liberating the hydrogen from the hydride stores is often available only at a low temperature level.

Although these attempts did improve the kinetics somewhat, certain essential disadvantages have not yet been eliminated from the resulting systems.

Furthermore, the storage capacity of such systems are generally far below what would theoretically be expected for MgH2.

However, there were encountered problems during the adhesion and the distribution of the nickel over the magnesium surface.

The storage capacity per volume of material which is achieved through this magnesium-containing granulate does not, however, meet any high demands because of the quantity of magnesium copper which is required for the eutectic mixture.

A high desorption temperature (above, for example, 150° C.) severely limits the uses to which the system may be put.

The use by Matsumato et al of amorphous structure materials to achieve better desorption kinetics due to the non-flat hysteresis curve is an inadequate and partial solution.

The other problems found in crystalline hydrogen storage materials, particularly low useful hydrogen storage capacity at moderate temperature, remain.

This is in contrast to multi-component single phase host crystalline materials which generally have a very limited range ofstoichiometry available.

A continuous range of control of chemical and structural modification of the thermodynamics and kinetics of such crystalline materials therefore is not possible.

One drawback to these disordered materials is that, in the past, some of the Mg based alloys have been difficult to produce.

Also, the most promising materials (i.e. magnesium based materials) were extremely difficult to make in bulk form.

That is, while thin-film sputtering techniques could make small quantities of these disordered alloys, there was no bulk preparation technique.

Conventional techniques like induction melting have been found to be inadequate for such purposes.

. . Indeed, when crystalline symmetry is destroyed, it becomes impossible to retain the same short-range order.

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