Hydrogen storage materials and methods including hydrides and hydroxides Number:7,521,036 from the United States Patent and Trademark Office (PTO) owispatent In one aspect, the invention provides a hydrogen storage composition having a hydrogenated state and a dehydrogenated state. In the hydrogenated state, such composition comprises a hydride and a hydroxide. In a dehydrogenated state, the composition comprises an oxide. The present invention also provides methods of producing hydrogen, including for mobile fuel cell device applications.<H hydroxides, including, Hydrogen, storag, 7521036.html, Patent, pto, 7521036

Title: Hydrogen storage materials and methods including hydrides and hydroxides

Abstract: In one aspect, the invention provides a hydrogen storage composition having a hydrogenated state and a dehydrogenated state. In the hydrogenated state, such composition comprises a hydride and a hydroxide. In a dehydrogenated state, the composition comprises an oxide. The present invention also provides methods of producing hydrogen, including for mobile fuel cell device applications.

Patent Number: 7,521,036 Issued on 04/21/2009 to Vajo, et al.

Inventors: Vajo; John J (Westhills, CA), Mertens; Florian O (Birmingham, MI), Jorgensen; Scott W (Bloomfield Township, MI)
Assignee: General Motors Corporation (Detroit, MI)

Appl. No.: 10/787,292

Filed: February 26, 2004

Current U.S. Class: 423/644 ; 423/645; 423/646; 423/647; 423/648.1; 423/658.2

Current International Class: C01B 3/02 (20060101); C01B 6/00 (20060101); C01B 6/02 (20060101); C01B 6/04 (20060101); C01B 6/06 (20060101); C01B 6/26 (20060101)

Field of Search: 423/644,645,646,647,648.1,658.2

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Primary Examiner: Langel; Wayne

Claims

What is claimed is:

1. A method of producing hydrogen comprising: conducting a reaction between a hydride composition and a dehydrated hydroxide composition to form hydrogen and an oxide composition, wherein said hydroxide composition is represented by the formula: MII.sup.y(OH).sub.y, where MII represents one or more cationic species other than hydrogen and is selected from the group consisting of Al, As, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof and y represents an average valence state of MII.

2. The method according to claim 1 wherein said hydride composition has one or more cationic species other than hydrogen.

3. The method according to claim 2 wherein said oxide composition comprises at least one of said one or more cations other than hydrogen derived from either of said hydride or said hydroxide compositions, respectively.

4. The method according to claim 1 wherein said hydride composition is represented by the formula: MI.sup.xH.sub.x, where MI represents said one or more cationic species other than hydrogen and x represents an average valence state of MI.

5. The method of claim 1 wherein said hydride composition is represented by MI.sup.xH.sub.x, where MI represents one or more cationic species other than hydrogen, and x represents an average valence state of MI.

6. The method of claim 5 wherein MI and MII are different cationic species.

7. The method claim 5 wherein MI and MII are the same cationic species.

8. The method of claim 5 wherein MI is a complex cationic species comprising two distinct cationic species.

9. The method of claim 5 wherein MII is a complex cationic species comprising two distinct cationic species.

10. of claim 5 wherein MI is selected from the group consisting of Al, As, B, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, K, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof.

11. The method of claim 5 wherein MI and MII are each elements independently selected from the group consisting of Al, Ba, Be, Ca, Cs, Li, Mg, Na, Rb, Si, Sr, Ti, V and mixtures thereof.

12. The method of claim 11 wherein MI and MII are each elements independently selected from the group consisting of Al, Be, Ca, Li, Mg, Na, Sr, Ti, and mixtures thereof.

13. The method according to claim 1 wherein said hydride composition is selected from the group consisting of: lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH), beryllium hydride (BeH.sub.2), magnesium hydride (MgH.sub.2), calcium hydride (CaH.sub.2), strontium hydride (SrH.sub.2), titanium hydride (TiH.sub.2), aluminum hydride (AlH.sub.3), boron hydride (BH.sub.3), lithium borohydride (LiBH.sub.4), sodium borohydride (NaBH.sub.4), magnesium borohydride (Mg(BH.sub.4).sub.2), calcium borohydride (Ca(BH.sub.4).sub.2), lithium alanate (LiAlH.sub.4), sodium alanate (NaAlH.sub.4), magnesium alanate (Mg(AlH.sub.4).sub.2), calcium alanate (Ca(AlH.sub.4).sub.2), and mixtures thereof.

14. The method according to claim 1 wherein said hydroxide composition is selected from the group consisting of: lithium hydroxide (LiOH), sodium hydroxide (NaOH), beryllium hydroxide (Be(OH).sub.2), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), strontium hydroxide (Sr(OH).sub.2), titanium hydroxide (Ti(OH).sub.2), aluminum hydroxide (Al(OH).sub.3), and mixtures thereof.

15. The method according to claim 1 wherein said hydride composition comprises LiH and said hydroxide composition comprises LiOH.

16. The method according to claim 15 wherein said reaction proceeds according to a reaction mechanism of LiH+LiOH.fwdarw.Li.sub.2O+H.sub.2.

17. The method according to claim 1 wherein said hydride composition comprises NaH and said hydroxide composition comprises LiOH.

18. The method according to claim 17 wherein said reaction proceeds according to a reaction mechanism of NaH+LiOH.fwdarw.1/2 Li.sub.2O+1/2 Na.sub.2O+H.sub.2.

19. The method according to claim 1 wherein said hydride composition comprises MgH.sub.2 and said hydroxide composition comprises Mg(OH).sub.2.

20. The method according to claim 19 wherein said reaction proceeds according to a reaction mechanism of MgH.sub.2+Mg(OH).sub.2.fwdarw.MgO+2 H.sub.2.

21. The method according to claim 1 wherein said hydride composition comprises AlH.sub.3 and said hydroxide composition comprises Al(OH).sub.3.

22. The method according to claim 21 wherein said reaction proceeds according to a reaction mechanism of AlH.sub.3+Al(OH).sub.3.fwdarw.Al.sub.2O.sub.3+3H.sub.2.

23. The method according to claim 1 wherein said hydride composition comprises CaH.sub.2 and said hydroxide composition comprises Ca(OH).sub.2.

24. The method according to claim 23 wherein said reaction proceeds according to a reaction mechanism of CaH.sub.2+Ca(OH).sub.2.fwdarw.CaO+2 H.sub.2.

25. The method according to claim 1 wherein said hydride composition comprises SrH.sub.2 and said hydroxide composition comprises Sr(OH).sub.2.

26. The method according to claim 25 wherein said reaction proceeds according to a reaction mechanism of SrH.sub.2+Sr(OH).sub.2.fwdarw.SrO+2 H.sub.2.

27. The method according to claim 1 wherein said hydride composition comprises BeH.sub.2 and said hydroxide composition comprises Be(OH).sub.2.

28. The method according to claim 27 wherein said reaction proceeds according to a reaction mechanism of BeH.sub.2+Be(OH).sub.2.fwdarw.BeO+2 H.sub.2.

29. The method according to claim 1 where said hydride composition comprises LiBH.sub.4 and said hydroxide composition comprises LiOH.

30. The method according to claim 29 where said reaction proceeds according to a reaction mechanism of LiBH.sub.4+4LiOH.fwdarw.LiBO.sub.2+2Li.sub.2O+4H.sub.2.

31. The method according to claim 1 where said hydride composition comprises NaBH.sub.4 and said hydroxide composition comprises Mg(OH).sub.2.

32. The method according to claim 31 where said reaction proceeds according to a reaction mechanism of NaBH.sub.4+2 Mg(OH).sub.2.fwdarw.NaBO.sub.2+2MgO+4H.sub.2.

33. The method according to claim 1 where said hydride composition comprises NaBH.sub.4 and said hydroxide composition comprises NaOH.

34. The method according to claim 33 where said reaction proceeds according to a reaction mechanism of NaBH.sub.4+4NaOH.fwdarw.NaBO.sub.2+2Na.sub.2O+4H.sub.2.

35. The method according to claim 1 wherein said reaction is reversible to form a species of said hydride composition or said hydroxide composition.

36. The method according to claim 35 wherein said reversible reaction is conducted by exposing said oxide composition to hydrogen to form said species.

37. The method according to claim 36 wherein said reversible reaction regenerates said hydride composition and said hydroxide composition.

38. The method according to claim 1 wherein said reaction is conducted at an elevated temperature relative to ambient conditions.

39. The method according to claim 38 wherein said reaction is conducted at a temperature 40.degree. C. or greater.

40. The method according to claim 1 wherein said hydride composition and said hydroxide composition are in particle form and said reaction is a solid-state reaction.

41. The method according to claim 40 wherein said hydride composition and said hydroxide composition are reduced in particle size prior to said reaction.

42. The method according to claim 1 wherein before conducting said reaction, said hydride composition and said hydroxide composition are essentially homogeneously mixed together.

43. The method according to claim 1 wherein during said reaction, said oxide composition, said hydrogen, or both, are removed from said hydride composition and said hydroxide composition, as said reaction proceeds.

44. The method according to claim 1 wherein during said reaction said hydrogen is removed as said reaction proceeds.

45. The method according to claim 1 wherein said reaction is conducted in the presence of a catalyst in contact with said hydride composition and said hydroxide composition.

46. The method according to claim 45 wherein said catalyst comprises a compound comprising an element selected from the group consisting of Ti, V, Cr, C, Fe, Mn, Ni, Nb, Pd, Si, Al, and mixtures thereof.

47. A method for releasing hydrogen from hydrogen storage materials comprising: mixing a first hydrogen storage material with a second hydrogen storage material, where said first hydrogen storage material comprises a hydride composition represented by MI.sup.xH.sup.x and said second hydrogen storage material comprises a dehydrated hydroxide composition represented by MII.sup.y(OH).sub.y, where MI and MII each represent a cationic species or a mixture of cationic species other than hydrogen, where MII is selected from the group consisting of Al, As, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof, and where x and y represent average valence states of respectively MI and MII; and conducting a reaction between said first storage material with said second storage material for a time and at a temperature sufficient to produce a reaction product comprising an oxide material and hydrogen.

48. The method of claim 47 wherein MI and MII are different cationic species.

49. The method of claim 47 wherein MI and MII are the same cationic species.

50. The method of claim 47 wherein MI is a complex cationic species comprising two distinct cationic species.

51. The method of claim 47 wherein MII is a complex cationic species comprising two distinct cationic species.

52. The method of claim 47 wherein MII is selected from the group consisting of OH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, Al, As, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof.

53. The method of claim 52 wherein MI and MII are each elements independently selected from the group consisting of Al, Ba, Be, Ca, Cs, Li, Mg, Na, Rb, Si, Sr, Ti, V and mixtures thereof.

54. The method of claim 53 wherein MI and MII are each elements independently selected from the group consisting of Al, Be, Ca, Li, Mg, Na, Sr, Ti, and mixtures thereof.

55. The method according to claim 47 wherein said hydride composition is selected from the group consisting of: lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH), beryllium hydride (BeH.sub.2), magnesium hydride (MgH.sub.2), calcium hydride (CaH.sub.2), strontium hydride (SrH.sub.2), titanium hydride (TiH.sub.2), aluminum hydride (AlH.sub.3), boron hydride (BH.sub.3), lithium borohydride (LiBH.sub.4), sodium borohydride (NaBH.sub.4), magnesium borohydride (Mg(BH.sub.4).sub.2), calcium borohydride (Ca(BH.sub.4).sub.2), lithium alanate (LiAlH.sub.4), sodium alanate (NaAlH.sub.4), magnesium alanate (Mg(AlH.sub.4).sub.2), calcium alanate (Ca(AlH.sub.4).sub.2), and mixtures thereof.

56. The method according to claim 47 wherein said hydroxide composition is selected from the group consisting of: lithium hydroxide (LiOH), sodium hydroxide (NaOH), beryllium hydroxide (Be(OH).sub.2), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), strontium hydroxide (Sr(OH).sub.2), titanium hydroxide (Ti(OH).sub.2), aluminum hydroxide (Al(OH).sub.3), and mixtures thereof.

57. The method according to claim 47 wherein said hydride composition comprises LiH and said hydroxide composition comprises LiOH.

58. The method according to claim 57 wherein said reaction proceeds according to a reaction mechanism of LiH+LiOH.fwdarw.Li.sub.2O+H.sub.2.

59. The method according to claim 47 wherein said hydride composition comprises NaH and said hydroxide composition comprises LiOH.

60. The method according to claim 59 wherein said reaction proceeds according to a reaction mechanism of NaH+LiOH.fwdarw.1/2 Li.sub.2O+1/2 Na.sub.2O+H.sub.2.

61. The method according to claim 47 wherein said reaction is reversed by exposing said oxide material to hydrogen to form a regenerated first storage material comprising a hydride and a regenerated second storage material comprising a hydroxide.

62. The method according to claim 61 wherein said hydride of said regenerated first storage material and said hydroxide of said regenerated second storage material are the same species as said first and said second starting materials, comprising said hydride and said hydroxide, respectively.

63. The method according to claim 47 wherein said reaction is conducted at an elevated temperature relative to ambient conditions.

64. The method according to claim 63 wherein said reaction is conducted at a temperature of 40.degree. C. or greater.

65. The method according to claim 47 wherein said first starting material and said second starting material are in particle form and said reaction is a solid state reaction.

66. The method according to claim 65 wherein said first starting material and said second starting material are reduced in particle size prior to said reaction.

67. The method according to claim 47 wherein before conducting said reaction, said first starting material and said second starting material are essentially homogeneously mixed together.

68. The method according to claim 47 wherein during said reaction, said oxide, said hydrogen, or both, are removed from said first starting material and said second starting material, as said reaction proceeds.

69. The method according to claim 47 wherein during said reaction said hydrogen is a removed from said first and said second starting materials as said reaction proceeds.

70. The method according to claim 47 wherein said reaction is conducted in the presence of a catalyst in contact with said first starting material and said second starting material.

71. The method according to claim 70 wherein said catalyst comprises a compound comprising an element selected from the group consisting of Ti, V, Cr, C, Fe, Mn, Ni, Nb, Pd, Si, Al, and mixtures thereof.

72. A method of producing a source of hydrogen gas comprising: liberating hydrogen from a solid hydrogenated starting material composition comprising a hydride and a dehydrated hydroxide selected from the group consisting of: lithium hydroxide (LiOH), sodium hydroxide (NaOH), beryllium hydroxide (Be(OH).sub.2), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), strontium hydroxide (Sr(OH).sub.2), titanium hydroxide (Ti(OH).sub.2), aluminum hydroxide (Al(OH).sub.3 and mixtures thereof, by reacting said hydride and said dehydrated hydroxide in a solid state reaction to produce a dehydrogenated reaction product and hydrogen gas.

73. The method according to claim 72 wherein said hydride and said hydroxide each have one or more cationic species other than hydrogen.

74. The method according to claim 72 further comprising regenerating said hydrogenated starting material composition by exposing said dehydrogenated product to hydrogen gas.

75. The method of claim 72 wherein said dehydrogenated product comprises an oxide.

76. The method of claim 74 wherein said regenerating is conducted at an elevated temperature relative to ambient conditions.

77. The method of claim 76 wherein said liberating of hydrogen is conducted at an elevated temperature greater than about 40.degree. C.

78. The method of claim 72 wherein said liberating is conducted by removing said hydrogen gas as said reacting proceeds.

79. The method of claim 72 wherein said liberating is conducted in the presence of a catalyst in contact with said starting material composition.

80. The method according to claim 79 wherein said catalyst comprises a compound comprising an element selected from the group consisting of Ti, V, Cr, C, Fe, Mn, Ni, Nb, Pd, Si, Al, and mixtures thereof.

81. A hydrogen storage composition having a hydrogenated state and a dehydrogenated state: (a) in said hydrogenated state, said composition comprises a hydride represented by MI.sup.xH.sub.x and a dehydrated hydroxide represented by MII.sup.y(OH).sub.y, where MI and MII respectively represent one or more cationic species other than hydrogen that are selected from the group consisting of Al, As, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof, wherein at least one of MI or MII is a complex cationic species comprising two distinct cationic species and x and y represent average valence states of MI and MII, respectively; and (b) in said dehydrogenated state, said composition comprises an oxide.

82. The composition of claim 81 wherein MI is said complex cationic species.

83. The composition of claim 81 wherein MII is a said complex cationic species.

84. The composition of claim 81 wherein MII is selected from the group consisting of Al, As, Ba, Be, Ca, Cd, Ce, Cs, Cu, Eu, Fe, Ga, Gd, Ge, Hf, Hg, In, La, Li, Mg, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sb, Sc, Se, Si, Sm, Sn, Sr, Th, Ti, Tl, V, W, Y, Yb, Zn, Zr, and mixtures thereof.

85. The composition of claim 84 wherein MI and MII is selected from the group consisting of Al, Ba, Be, Ca, Cs, Li, Mg, Na, Rb, Si, Sr, Ti, V and mixtures thereof.

86. The composition of claim 85 wherein MI or MII is selected from the group consisting of Al, Be, Ca, Li, Mg, Na, Sr, Ti, and mixtures thereof.

87. The composition of claim 81 wherein said hydride is selected from the group consisting of: lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH), beryllium hydride (BeH.sub.2), magnesium hydride (MgH.sub.2), calcium hydride (CaH.sub.2), strontium hydride (SrH.sub.2), titanium hydride (TiH.sub.2), aluminum hydride (AlH.sub.3), boron hydride (BH.sub.3), lithium borohydride (LiBH.sub.4), sodium borohydride (NaBH.sub.4), magnesium borohydride (Mg(BH.sub.4).sub.2), calcium borohydride (Ca(BH.sub.4).sub.2), lithium alanate (LiAlH.sub.4), sodium alanate (NaAlH.sub.4), magnesium alanate (Mg(AlH.sub.4).sub.2), calcium alanate (Ca(AlH.sub.4).sub.2), and mixtures thereof.

88. The composition of claim 81 wherein said hydroxide is selected from the group consisting of: lithium hydroxide (LiOH), sodium hydroxide (NaOH), beryllium hydroxide (Be(OH).sub.2), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), strontium hydroxide (Sr(OH).sub.2), titanium hydroxide (Ti(OH).sub.2), aluminum hydroxide (Al(OH).sub.3), and mixtures thereof.

89. The composition of claim 81 wherein said hydride comprises LiH.

90. The composition of claim 81 wherein said hydroxide comprises LiOH.

91. The composition according to claim 81 where said hydride composition comprises LiBH.sub.4 and said hydroxide comprises LiOH.

92. The composition according to claim 91 where said reaction proceeds according to a reaction mechanism of LiBH.sub.44 LiOH .fwdarw.LiBO.sub.2+2 Li.sub.2O+4H.sub.2.

93. The composition according to claim 81 where said hydride composition comprises NaBH.sub.4 and said hydroxide comprises Mg(OH).sub.2.

94. The composition according to claim 93 where said reaction proceeds according to a reaction mechanism of NaBH.sub.4+2 Mg(OH).sub.2.fwdarw.NaBO.sub.2+2MgO +4H.sub.2.

95. The composition according to claim 81 where said hydride composition comprises NaBH.sub.4 and said hydroxide comprises NaOH.

96. The composition according to claim 95 where said reaction proceeds according to a reaction mechanism of NaBH.sub.4+4 NaOH.fwdarw.NaBO.sub.2+2 Na.sub.2O4 H.sub.2.

97. A hydrogen storage composition having a hydrogenated state and a dehydrogenated state: (a) in said hydrogenated state, said composition comprises a hydride represented by MI.sup.xH.sub.x and a dehydrated hydroxide represented by MII.sup.y(OH).sub.y, where MI and MII respectively represent one or more cationic species other than hydrogen that are selected from the group consisting of Al, Be, Ca, Mg, Sr, and mixtures thereof, wherein x and y represent average valence states of MI and MII, respectively; and (b) in said dehydrogenated state, said composition comprises an oxide.

98. The composition according to claim 97 wherein said hydride composition comprises MgH.sub.2 and said hydroxide composition comprises Mg(OH).sub.2.

99. The composition according to claim 98 wherein said reaction proceeds according to a reaction mechanism of MgH.sub.2+Mg(OH).sub.2.fwdarw.MgO+2 H.sub.2.

100. The composition according to claim 97 wherein said hydride composition comprises AlH.sub.3 and said hydroxide composition comprises Al(OH).sub.3.

101. The composition according to claim 100 wherein said reaction proceeds according to a reaction mechanism of AlH.sub.3+Al(OH).sub.3.fwdarw.Al.sub.2O.sub.3+3H.sub.2.

102. The composition according to claim 97 wherein said hydride composition comprises CaH.sub.2 and said hydroxide composition comprises Ca(OH).sub.2.

103. The composition according to claim 102 wherein said reaction proceeds according to a reaction mechanism of CaH.sub.2+Ca(OH).sub.2.fwdarw.CaO+2 H.sub.2.

104. The composition according to claim 97 wherein said hydride composition comprises SrH.sub.2 and said hydroxide composition comprises Sr(OH).sub.2.

105. The composition according to claim 104 wherein said reaction proceeds according to a reaction mechanism of SrH.sub.2+Sr(OH).sub.2.fwdarw.SrO+2 H.sub.2.

106. The composition according to claim 97 wherein said hydride composition comprises BeH.sub.2 and said hydroxide composition comprises Be(OH).sub.2.

107. The composition according to claim 106 wherein said reaction proceeds according to a reaction mechanism of BeH.sub.2+Be(OH).sub.2.fwdarw.BeO+2 H.sub.2.

Description

FIELD OF THE INVENTION

The present invention relates to hydrogen storage compositions, the method of making such hydrogen storage compositions and use thereof.

BACKGROUND OF THE INVENTION

Hydrogen is desirable as a source of energy because it reacts cleanly with air producing water as a by-product. In order to enhance the desirability of hydrogen as a fuel source, particularly for mobile applications, it is desirable to increase the available energy content per unit volume and per unit mass of storage. Presently, this is done by conventional means such as storage under high pressure, at thousands of pounds per square inch (e.g., 5,000 to 10,000 psi), cooling to a liquid state, or absorbing into a solid such as a metal hydride. Pressurization and liquification require relatively expensive processing and storage equipment.

Storing hydrogen in a solid material such as metal hydrides, provides volumetric hydrogen density which is relatively high and compact as a storage medium. Binding the hydrogen as a solid is desirable since it desorbs when heat is applied, thereby providing a controllable source of hydrogen.

Rechargeable hydrogen storage devices have been proposed to facilitate the use of hydrogen. Such devices may be relatively simple and generally are simply constructed as a shell and tube heat exchanger where the heat transfer medium delivers heat for desorption. Such heat transfer medium is supplied in channels separate from the chamber which houses the hydrogen storage material. Therefore, when hydrogen release is desired, fluids at different temperatures may be circulated through the channels, in heat transfer relationship with the storage material, to facilitate release of the hydrogen. For certain materials, recharging the storage medium can be achieved by pumping hydrogen into the chamber and through the storage material while the heat transfer medium removes heat, thus facilitating the charging or hydrogenating process. An exemplary hydrogen storage material and storage device arranged to provide suitable heat transfer surface and heat transfer medium for temperature management is exemplified in U.S. Pat. No. 6,015,041.

Presently, the selection of relatively light weight hydrogen storage material is essentially limited to magnesium and magnesium-based alloys which provide hydrogen storage capacity of several weight percent, essentially the best known conventional storage material with some reversible performance. However, such magnesium based materials have a limitation in that they take up hydrogen at very high temperature and high hydrogen pressure. In addition, hydrogenation of the storage material is typically impeded by surface oxidation of the magnesium. Other examples, such as LaNi.sub.5 and TiFe, have relatively low gravimetric hydrogen storage density, since they are very heavy.

Therefore, in response to the desire for an improved hydrogen storage medium, the present invention provides an improved hydrogen storage composition, its use as a storage medium and a method for forming such materials.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a method of producing hydrogen comprising conducting a reaction between a hydride composition and a hydroxide composition to form hydrogen and an oxide composition, wherein the hydroxide composition has one or more cationic species other than hydrogen.

In another aspect the present invention provides a method for releasing hydrogen from hydrogen storage materials comprising mixing a first hydrogen storage material with a second hydrogen storage material. The first hydrogen storage material comprises a hydride composition represented by MI.sup.xH.sub.x and the second hydrogen storage material comprises a hydroxide composition represented by MII.sup.y(OH).sub.y, where MI and MII each represent a cationic species or a mixture of cationic species other than hydrogen, and where x and y represent average valence states of respectively MI and MII. The method further comprises conducting a reaction between the first storage material with the second storage material for a time and at a temperature sufficient to produce a reaction product comprising an oxide material and hydrogen.

In still another aspect of the invention, a hydrogen storage composition has a hydrogenated state and a dehydrogenated state, where in the hydrogenated state, the composition comprises a hydride and a hydroxide having one or more cationic species other than hydrogen. In the dehydrogenated state, the composition comprises an oxide.

Another aspect of the present invention is a method of producing a source of hydrogen gas comprising liberating hydrogen from a solid hydrogenated starting material composition comprising a hydride and a hydroxide, by reacting the hydride and the hydroxide in a solid state reaction to produce a dehydrogenated reaction product and hydrogen gas.

Yet another aspect of the present invention provides a mixture of a hydride and a hydroxide having cationic species other than hydrogen, each one characterized by promoting release of hydrogen from the other one in the presence of at least one of: a catalyst and elevated temperature.

Another aspect of the invention relates to a power device comprising a fuel cell that uses hydrogen as fuel and a storage unit containing a hydrogen storage material having a hydrogenated state and a dehydrogenated state. The storage material releases hydrogen used as fuel in the fuel cell. The hydrogenated state of the storage material comprises a hydroxide having a cationic species other than hydrogen and a hydride. A filler passage is associated with the storage unit and supplying hydrogen to the dehydrogenated storage material in the storage unit.

Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 shows hydrogen production by weight percent loss of hydrogen from a hydrogen storage material comprising lithium hydride and lithium hydroxide analyzed by a modified volumetric Sievert's apparatus analysis;

FIG. 2 is a graph showing hydrogen production for a hydrogen storage material comparing a first sample comprising lithium hydride and lithium hydroxide and a second sample comprising lithium hydride, lithium hydroxide, and a catalyst, where temperature is incrementally increased in a modified Sievert's apparatus;

FIG. 3 is a graph showing hydrogen production over time for a hydrogen storage material comprising sodium hydride and lithium hydroxide from a modified Sievert's apparatus analysis; and

FIG. 4 is a graph showing hydrogen production over time for a hydrogen storage material comprising a complex hydride of lithium boroydride and lithium hydroxide from a modified Sievert's apparatus analysis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

In one aspect, the present invention provides methods of producing and releasing hydrogen from a hydrogen storage material system. In one preferred embodiment, a method is provided for releasing hydrogen from hydrogen storage materials by conducting a hydrogen production reaction by reacting a hydride composition and a hydroxide composition having one or more cations other than hydrogen. The hydrogen production reaction produces hydrogen and a reaction byproduct comprising an oxide composition. As used herein, the term "composition" refers broadly to a substance containing at least the preferred chemical compound, but which may also comprise additional substances or compounds, including impurities. The term "material" also broadly refers to matter containing the preferred compound or composition.

In another aspect, the present invention provides hydrogen storage materials. In one preferred embodiment of the present invention, a hydrogen storage composition has a hydrogenated state and a dehydrogenated state, therein providing two distinct physical states where hydrogen can be stored and subsequently released. In the hydrogenated state, the composition comprises a hydride and a hydroxide. In the dehydrogenated state, the composition comprises an oxide.

In one preferred embodiment of the present invention, the hydride is represented by the general formula MI.sup.xH.sub.x, where MI represents one or more cationic species other than hydrogen, and x represents the average valence state of MI, where the average valence state maintains the charge neutrality of the compound.

In another preferred embodiment of the present invention, the hydroxide is represented by the general formula MII.sup.y(OH).sub.y, where MII represents one or more cationic species other than hydrogen, and y represents the average valence state of MII where the average valence state maintains the charge neutrality of the compound.

In yet another preferred embodiment of the present invention, the hydride composition is represented by MI.sup.xH.sub.x and the hydroxide composition is represented by MII.sup.y(OH).sub.y, where MI and MII respectively represent one or more cationic species other than hydrogen, and x and y represent average valence states of MI and MII, and where the average valence states maintain the charge neutrality of the compounds, respectively.

In accordance with the present invention, MI and MII each represent one or more of a cationic species or a mixture of cationic species other than hydrogen. It should be noted that MI and MII are independently selected from one another. Thus, the present invention contemplates MI and MII comprising the same cationic species, or in alternate preferred embodiments, MI and MII comprise distinct cationic species that are different from one another. Further, MI, MII, or both may be selected to be complex cations, which comprise two or more distinct cationic species. In the case where MI, MII, or both are complex cations, MI and MII may comprise one or more of the same cationic species, or may have entirely distinct cationic species from one another. Hydrides are often referred to as complex hydrides, which are further contemplated in the present invention. A complex hydride comprises two cationic species, however one of the cationic species forms an anionic group with hydrogen, which further interacts with a second cationic species. This concept can be expressed by the following formula with a hydride expressed as MI.sup.xH.sub.x, where MI comprises two distinct cationic species, M' and M'', so that MI=M'+M''. Thus, the hydride can be expressed as: M'.sub.d.sup.a(M''.sup.bH.sub.c).sub.a.sup.-d where (M''.sup.bH.sub.c) is an anionic group, where d=(c-b) and a, b, c, and d are selected so as to maintain charge balance and electroneutrality of the compound. Cationic species that are preferred for all the preferred embodiments of the present invention include metal cations, as well as non-metal cations such as boron. Further, MII is also optionally selected to be an organic cationic group non-metal cation, such as CH.sub.3.

Elements that form preferred cations and mixtures of cations for MI and MII in the type of compounds of the present invention are as follows. For both hydrides and hydroxides, certain preferred cationic species comprise: aluminum (Al), boron (B), barium (Ba), beryllium (Be), calcium (Ca), cesium (Cs), potassium (K), lithium (Li), magnesium (Mg), sodium (Na), rubidium (Rb), silicon (Si), strontium (Sr), titanium (Ti), vanadium (V), and mixtures thereof. Particularly preferred elements comprise: aluminum (Al), boron (B), beryllium (Be), calcium (Ca), potassium (K), lithium (Li), magnesium (Mg), sodium (Na), strontium (Sr), titanium (Ti), and mixtures thereof. The most preferred cationic species are Li and Na. Evaluation of the aforesaid known species produces, by analogy, the following added cationic species besides those recited above which are thought to be usable based on predictive thermodynamics, but not yet demonstrated, include arsenic (As), cadmium (Cd), cerium (Ce), europium (Eu), iron (Fe), gallium (Ga), gadolinium (Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium (In), lanthanum (La), manganese (Mn), neodymium (Nd), nickel (Ni), lead (Pb), praseodymium (Pr), antimony (Sb), scandium (Sc), selenium (Se), samarium (Am), tin (Sn), thorium (Th), thallium (Tl), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), zirconium (Zr). For MII, another feasible cationic species comprises low molecular weight organic groups, such as methyl(CH.sub.3), ethyl(C.sub.2H.sub.5), and propyl(C.sub.3H.sub.7) groups.

In view of the above, the cationic species MI or MII generally comprise: aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be), calcium (Ca), cadmium (Cd), cerium (Ce), cesium (Cs), copper (Cu), europium (Eu), iron (Fe), gallium (Ga), gadolinium (Gd), germanium (Ge), hafnium (Hf), mercury (Hg), indium (In), potassium (K), lanthanum (La), lithium (Li), magnesium (Mg), manganese (Mn), sodium (Na), neodymium (Nd), nickel (Ni), lead (Pb), praseodymium (Pr), rubidium (Rb), antimony (Sb), scandium (Sc), selenium (Se), silicon (Si), samarium (Sm), tin (Sn), strontium (Sr), thorium (Th), titanium (Ti), thallium (Tl), tungsten (W), yttrium (Y), ytterbium (Yb), zinc (Zn), and zirconium (Zr). Additionally, MII may comprise an organic cationic species, such as methyl(CH.sub.3), ethyl(C.sub.2H.sub.5), and propyl(C.sub.3H.sub.7) groups.

In preferred embodiments of the present invention, a solid-state hydride composition (i.e., in particulate form) reacts with a hydroxide composition (i.e., in particulate form) via a solid-state reaction to produce and release gaseous hydrogen and a solid-state byproduct compound comprising an oxide. Where the hydride composition is selected as MI.sup.xH.sub.x and the hydroxide composition is selected as MII.sup.y(OH).sub.y, the hydrogen production reaction proceeds by the following reaction mechanism:

.times..function.>.times..times..times..times..times. ##EQU00001## where as previously discussed, x is the average valence state of MI and y is the average valence state of MII where the average valence states maintain the charge neutrality of the respective compounds. Thus, the hydrogenated state of the hydrogen storage composition corresponds to the hydrogenated hydride and hydrogenated hydroxide, and the dehydrogenated hydrogen storage composition corresponds to the one or more byproduct compounds comprising an oxide. It should be noted that where MI and MII are the same cationic species, which can be represented by M, the above reaction mechanism can be simplified to:

.times..function.>.times..times. ##EQU00002## where z represents the average valence state of M, where the average valence state maintains the charge neutrality of the compound.

According to the present invention, it is preferred that at least one byproduct composition comprises an oxide having one or more cationic species of the hydroxide and hydride (i.e., MI, MII, or both). The independent selection of cationic species can vary the stoichiometry of the reaction and the types of byproduct compounds formed. It should be noted that the oxide byproduct compounds

.times..times..times..times..times..times. ##EQU00003## (or

.times. ##EQU00004## in the case where MI and MII are the same cation M) may thermodynamically favor forming and/or decomposing into different byproduct compounds. Further, with certain reactants and stoichiometry of the reactants, such oxide byproduct compounds may also comprise higher-order complex hydrides, for example, as will be described in more detail below. These further byproducts are formed of the same general constituents as the primary byproducts, but they have different valence states, atomic ratios, or stoichiometry, depending on the cationic species involved, as recognized by one of skill in the art.

In certain preferred embodiments of the present invention the hydrogen storage composition comprises a hydride selected from the group consisting of: lithium hydride (LiH), sodium hydride (NaH), potassium hydride (KH), beryllium hydride (BeH.sub.2), magnesium hydride (MgH.sub.2), calcium hydride (CaH.sub.2), strontium hydride (SrH.sub.2), titanium hydride (TiH.sub.2), aluminum hydride (AlH.sub.3), boron hydride (BH.sub.3), and mixtures thereof. Particularly preferred hydride compositions comprise LiH or NaH.

In alternate preferred embodiments of the present invention the hydrogen storage composition comprises a hydride which is a complex hydride selected from the group consisting of: lithium borohydride (LiBH.sub.4), sodium borohydride (NaBH.sub.4), magnesium borohydride (Mg(BH.sub.4).sub.2), calcium borohydride (Ca(BH.sub.4).sub.2), lithium alanate (LiAlH.sub.4), sodium alanate (NaAlH.sub.4), magnesium alanate (Mg(AlH.sub.4).sub.2), calcium alanate (Ca(AlH.sub.4).sub.2), and mixtures thereof. Particularly preferred complex hydrides comprise lithium borohydride (LiBH.sub.4), sodium borohydride (NaBH.sub.4), lithium alanate (LiAlH.sub.4), and sodium alanate (NaAlH.sub.4).

Further, other preferred embodiments of the present invention, comprise a hydroxide composition selected from the group consisting of: lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), beryllium hydroxide (Be(OH).sub.2), magnesium hydroxide (Mg(OH).sub.2), calcium hydroxide (Ca(OH).sub.2), strontium hydroxide (Sr(OH).sub.2), titanium hydroxide (Ti(OH).sub.2), aluminum hydroxide (Al(OH).sub.3), boron hydroxide (B(OH).sub.3) which is also known as boric acid and more conventionally is expressed as (H.sub.3BO.sub.3), and mixtures thereof. Particularly preferred hydroxide compounds comprise LiOH and NaOH.

Thus, according to one preferred embodiment of the present invention, a hydrogen production reaction is conducted by reacting a hydride comprising LiH with a hydroxide comprising LiOH. The reaction proceeds according to the reaction mechanism: LiH+LiOH.fwdarw.Li.sub.2O+H.sub.2. This reaction produces a theoretical 6.25 weight % of hydrogen on a material basis.

In an alternate preferred embodiment of the present invention a hydrogen production reaction occurs by reacting a hydride comprising NaH with a hydroxide comprising LiOH. The reaction mechanism for this reaction can be expressed as NaH+LiOH.fwdarw.1/2Li.sub.2O+1/2Na.sub.2O+H.sub.2. This reaction generates a theoretical 4.1 weight % hydrogen on a material basis. It should be noted that the byproduct compounds are generally expressed as Li.sub.2O and Na.sub.2O, however, mixed or partially mixed metal oxides may form based on the conditions at which the reaction takes place, and may be thermodynamically favored. Thus, for example, the byproduct composition may comprise an oxide composition comprising a mixed cation oxide

.times..times..times..times. ##EQU00005## formed as a byproduct, where x and y are the average valence states of MI and MII, respectively, and where the average valence state maintains the charge neutrality of the compound. In such a case, the above reaction may form LiNaO as a byproduct compound. The mixed cation oxide byproduct compound may comprise the entire oxide product, or may be mixed with the single cation oxides to result in multiple distinct oxide byproduct compounds, depending on the thermodynamics of the reaction.

In certain preferred embodiments of the present invention, the reaction mechanism for producing hydrogen from the hydride and hydroxide is reversible. By "reversible" it is meant that a species of a starting material hydroxide or hydride is regenerated at temperature and pressure conditions which are economically and industrially useful and practicable. Particularly preferred "reversible" reactions include those where exposing one or more byproduct compounds to hydrogen regenerates a species of a starting material hydroxide or hydride. In the same manner, a "non-reversible reaction" generally applies to both reactions that are irreversible via the reaction mechanism pathway, and also to those reactions where regenerating a species of a starting material hydride or hydroxide by exposure to hydrogen is carried out at impractical processing conditions, such as, extreme temperature, extreme pressure, or cumbersome product removal, which prevents its widespread and practical use. Endothermic hydrogen formation reactions according to the present invention are generally reversible at desirable temperature and pressure conditions.

One aspect of the present invention is a reduction in the overall energy requirements for a system of storing and subsequently releasing hydrogen. Minimizing the overall enthalpy changes associated with the hydrogen storage material system results in an improvement of the overall efficiency of the fuel cell system. As the overall enthalpy change increases, so do the requirements for managing heat transfer systems (heating and cooling operations). In particular, it is highly advantageous to minimize heating and cooling systems in mobile units containing fuel cells (e.g., vehicles or electronic devices), because additional systems draw parasitic energy and increase the overall weight of the mobile unit, thereby decreasing its gravimetric efficiency.

Other advantages of minimizing overall enthalpy change in the hydrogen storage system are often realized during start-up and other transient conditions (e.g., low load conditions), because there is less diversion of energy from other important system operations. Thus, one aspect of the present invention is a minimization of the overall energy necessary to both produce and regenerate a hydrogen storage material. In preferred embodiments of the present invention, the energy required for hydrogen production and recharge is relatively low, and vastly improved when compared to energy requirements of prior art hydrogen storage systems.

As previously discussed, one preferred embodiment of the present invention comprises a hydrogen storage composition where the hydride is lithium hydride LiH and the hydroxide is lithium hydroxide LiOH, which react with one another to form Li.sub.2O and H.sub.2. The enthalpy of reaction (.DELTA.H.sub.r) for the hydrogen production reaction was calculated based on the standard heat of formation (.DELTA.H.sub.f) for each of the compounds, and resulted in theoretical .DELTA.H.sub.r of -23.3 kJ/mol-H.sub.2. This .DELTA.H.sub.r indicates an exothermic reaction, with a relatively low enthalpy (and thus a low level of heat production). Minimizing the amount of heat released into the fuel cell system is preferred, because larger enthalpies result in larger quantities of emitted heat, which must be controlled by cooling systems to prevent damage to the surrounding environment, especially in a fuel cell system where certain components (e.g., control circuitry or the membrane exchange assembly (MEA)) potentially degrade upon exposure to higher temperatures. As the enthalpy of the reaction increases, the size and complexity of the heat transfer system becomes much larger. Further, larger heats of reaction have the potential to be less controllable and often cannot be stopped prior to complete reaction. The present embodiment thus provides a relatively low exothermic heat of reaction for the hydrogen production reaction. An exothermic hydrogen production reaction has an advantage of not requiring a sustained input of external energy from the fuel cell system for hydrogen generation (aside from any activation energy necessary to initiate the reaction, as will be discussed in more detail below). It is preferred that the heat released by the hydrogen generation reaction is dissipated by a heat transfer system, as it is preferred to maintain the storage materials at a constant temperature during the reaction. However, the present embodiment does not require an extensive cooling system and further provides good control over the reaction as it proceeds.

Other preferred embodiments according to the present invention have an exothermic hydrogen production reaction and include reactions between a hydride composition MI.sup.xH.sub.x and a hydroxide composition MII.sup.y(OH).sub.y, where MI and MII are selected to be the same cationic species selected from the group consisting of Al, B, Be, Ca, Mg, Sr, and Ti. These reactions have a higher enthalpy of reaction .DELTA.H.sub.r than the previous embodiment, and include for example, the following reactions. Where the hydride is selected to be MgH.sub.2 and the hydroxide is selected to be Mg(OH).sub.2, the reaction can be expressed as: MgH.sub.2+Mg(OH).sub.2.fwdarw.MgO+2H.sub.2 which has a .DELTA.H.sub.r of -101.3 kJ/mol-H.sub.2 and a theoretical hydrogen production of 4.7 wt. %. Where the hydride is selected to be AlH.sub.3 and the hydroxide is selected to be Al(OH).sub.3, the reaction can be expressed as: Al.sub.3+Al(OH).sub.3.fwdarw.Al.sub.2O.sub.3+3H.sub.2 which has a .DELTA.H.sub.r of -129.3 kJ/mol-H.sub.2 and a theoretical hydrogen production of 5.5 wt. %. In the case where the hydride is selected to be CaH.sub.2 and the hydroxide is selected to be Ca(OH).sub.2, the reaction can be expressed as: CaH.sub.2+Ca(OH).sub.2.fwdarw.CaO+2H.sub.2 which has a .DELTA.H.sub.r of -53.7 kJ/mol-H.sub.2 and a theoretical hydrogen production of 3.4 wt. %. Where the hydride is selected to be SrH.sub.2 and the hydroxide is selected to be Sr(OH).sub.2, the reaction can be expressed as: SrH.sub.2+Sr(OH).sub.2.fwdarw.SrO+2H.sub.2 which has a .DELTA.H.sub.r of -17.7 kJ/mol-H.sub.2 and a theoretical hydrogen production of 1.9 wt. %. Where the hydride is selected to be BH.sub.3 and the hydroxide is selected to be B(OH).sub.3, the reaction can be expressed as: BH.sub.3+B(OH).sub.3.fwdarw.B.sub.2O.sub.3+3H.sub.2 which has a .DELTA.H.sub.r of -94.9 kJ/mol-H.sub.2 and a theoretical hydrogen production of 7.9 wt. %. Where the hydride is selected to be BeH.sub.2 and the hydroxide is selected to be Be(OH).sub.2, the reaction can be expressed as: BeH.sub.2+Be(OH).sub.2.fwdarw.BeO+2H.sub.2 which has a .DELTA.H.sub.r of -147.4 kJ/mol-H.sub.2 and a theoretical hydrogen production of 7.4 wt. %.

An additional exothermic hydrogen production reaction according to the present invention comprises reacting lithium hydride (LiH) with boron hydroxide (B(OH).sub.3) (which is more typically known as boric acid and expressed as H.sub.3BO.sub.3), which under certain pressure, temperature, and other reaction conditions proceeds by the following reaction mechanism: 3LiH+H.sub.3BO.sub.3.fwdarw.LiBO.sub.2+Li.sub.2O+3H.sub.2 which has a .DELTA.H.sub.r of -84.2 kJ/mol-H.sub.2 and a theoretical hydrogen production of 6.9 wt. %. Under different pressure, temperature, and other reaction conditions, the same reactants can proceed according to the following reaction mechanism, where the oxide product differs from the two oxide products above (i.e., LiBO.sub.2 and Li.sub.2O), and forms a single complex higher order oxide product (Li.sub.3BO.sub.3): 3LiH+H.sub.3BO.sub.3.fwdarw.Li.sub.3BO.sub.3+3H.sub.2 which likewise has a .DELTA.H.sub.r of -84.2 kJ/mol-H.sub.2 and a theoretical hydrogen production of 6.9 wt. %.

Further preferred alternate embodiments of the present invention, are where the hydride composition is MI.sup.xH.sub.x and the hydroxide is MII.sup.y(OH).sub.y, where the hydride is a complex hydride M'.sub.d.sup.a(M''.sup.bH.sub.c).sup.-d where M' is selected to be lithium and M'' is selected to be boron, and the reaction is exothermic, include the following reactions. The first hydrogen production reaction occurs between: LiBH.sub.4+4LiOH.fwdarw.LiBO.sub.2+2Li.sub.2O+4H.sub.2 where a theoretical 6.8 weight % of hydrogen is produced and the reaction has a .DELTA.H.sub.r of -22 kJ/mol-H.sub.2. A second hydrogen production reaction with a complex hydride where M' is sodium and M'' is boron, includes the reaction: NaBH.sub.4+2Mg(OH).sub.2.fwdarw.NaBO.sub.2+2MgO+4H.sub.2 which produces a theoretical 5.2 weight % of hydrogen and a .DELTA.H.sub.r of -34 kJ/mol-H.sub.2.

Another preferred embodiment of the present invention previously discussed is that where the hydride is sodium hydride (NaH) and the hydroxide is lithium hydroxide (LiOH). A calculated heat of reaction (.DELTA.H.sub.r) is +9.7 kJ/mol-H.sub.2, which indicates an endothermic heat of reaction, which is relatively small. Thus, producing hydrogen with this hydrogen storage material system would require only slight heating throughout the hydrogen production reaction. However, because the overall quantity of heat generated is relatively low, this embodiment is preferred for certain applications. The endothermic nature of the hydrogen production reaction allows for an exothermic recharging reaction.

In certain applications, this hydrogen storage material composition may be preferred because the regeneration reaction is generally reversible at relatively low temperature and pressure conditions. For example, a predicted equilibrium pressure for the byproduct material comprising oxide is approximately 1 bar at 50.degree. C., thus upon exposure to pressurized hydrogen above the equilibrium pressure, the mater