Destabilized and catalyzed borohydrided for reversible hydrogen storage
A hydrogen storage material and process is provided in which catalyzed alkali borohydride materials and partially substituted borohydride materials are created and which may contain effective amounts of catalyst(s) which include transition metal oxides, halides, and chlorides of titanium, zirconium, tin, vanadium, iron, cobalt and combinations of the various catalysts and the destabilization agents which include metals, metal hydrides, metal chlorides and complex hydrides of magnesium, calcium, strontium, barium, aluminum, gallium, indium, thallium and combinations of the various destabilization agents. When the catalysts and destabilization agents are added to an alkali borodydride such as a lithium borohydride, the initial hydrogen release point of the resulting mixture is substantially lowered. Additionally, the hydrogen storage material may be rehydrided with weight percent values of hydrogen of at least about nine percent.
1 . A process of forming a hydrogen storage material comprising the steps of:
providing a quantity of an alkali borohydride;
mixing with the alkali borohydride a substitution agent selected from the group consisting of alkali earth elements, metal chlorides, metal hydrides, complex hydrides, and mixtures thereof;
ball milling the alkali borohydride with said substitution agent;
sintering the ball milled mixture of said metal borohydride with said substitution agent at a temperature below the melting point of said metal borohydride and at a hydrogen pressure greater than the decomposition pressure of the metal borohydride at said temperature, thereby achieving a solid diffusion substitution between said substitution agent, a metal component of said metal borohydride and thereby providing a sintered block of partially substituted borohydride;
crushing and ball milling said block of partially substituted borohydride so as to achieve an average particle size of between about 20 nanometers to about 100 nanometers; and,
optionally introducing a catalyst during said ball milling of said partially substituted borohydride.
2 . The partially substituted metal borohydride made according to the process of claim 1 .
3 . A process of forming a metal borohydride comprising the steps of:
providing a supply of metal borohydride;
substituting metal cations of the metal borohydride with metal cations having a lower metallic ion strength, thereby lowering the stability of the boron to hydrogen bonds in a [BH 4 ] −1 tetrahedron;
optionally substituting boron atoms in the tetrahedron with other elements selected from the group consisting of Al, Ga, In, Tl, and combinations thereof;
thereby providing a substituted metal borohydride having improved hydrogen kinetics.
4 . The process according to claim 1 wherein said substituted hydrogen storage material may be rehydrided.
5 . The process according to claim 1 wherein when said hydrogen storage material is rehydrided, said hydrogen storage material thereafter reversibly releases at least about 8wt % hydrogen.
6 . The hydrogen storage material according to claim 3 wherein the amount of hydrogen released following rehydriding is at least about 8wt % hydrogen.
7 . The process according to claim 1 wherein said alkali borohydrides are selected from the group consisting of lithium borohydride, sodium borohydride, potassium borohydride, or combinations thereof.
8 . The process according to claim 3 wherein said alkali borohydrides are selected from the group consisting of lithium borohydride, sodium borohydride, potassium borohydride, and combinations thereof.
9 . The process according to claim 1 wherein said alkali earth elements consisting of magnesium, calcium, strontium, barium, aluminum, and mixtures thereof.
10 . The process according to claim 1 wherein said metal chlorides are selected from the group consisting of MgCl 2 , CaCl 2 , SrCl 2 , BaCl 3 and combinations thereof.
11 . The process according to claim 1 wherein said metal hydrides are selected from the group consisting of MgH 2 , AlH 3 , CaH 2 , TiH 2 , ZrH 2 and combinations thereof.
12 . The process according to claim 1 wherein said complex hydrides are selected from the group LiAlH 4 , NaAl