Compact solid source of hydrogen gas

• US 6,746,496 B1
• Filed: 07/09/2002
• Issued: 06/08/2004
• Est. Priority Date: 01/15/2002
• Status: Active Grant

• Current Assignee: US Department of Energy (Government of the United States of America)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Sylwester, Alan P., Hecht, Andrew M., Bell, Nelson S., Kravitz, Stanley H.
• Primary Examiner(s): Caldarola, Glenn
• Assistant Examiner(s): RIDLEY, BASIA ANNA
• Application Number:
  US10/191,900
• Time in Patent Office: 700 Days
• Field of Search: 48/61, 48/62.R, 48/89, 481/185, 481/19, 481/20, 481/74, 481/97.R, 422/162, 422/211, 422/234, 422/236, 422/238, 422/240, 423/648.1, 423/657, 423/658.2
• US Class Current: 48/118.5
• CPC Class Codes: B01J 19/0093 Microreactors, e.g. miniaturised or microfabricated reactors laboratory containers with capillary fluid transport in microfabricated channels or chambers B01L3/5027
• CPC Class Codes: B01J 2219/00828 Silicon wafers or plates
• CPC Class Codes: B01J 2219/00835 Comprising catalytically active material
• CPC Class Codes: B01J 2219/00891 Feeding or evacuation
• CPC Class Codes: B01J 7/02 by wet methods
• CPC Class Codes: C01B 3/065 from a hydride
• CPC Class Codes: F17C 11/005 for hydrogen
• CPC Class Codes: Y02E 60/32 Hydrogen storage
• CPC Class Codes: Y02E 60/36 Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

A compact solid source of hydrogen gas, where the gas is generated by contacting water with micro-disperse particles of sodium borohydride in the presence of a catalyst, such as cobalt or ruthenium. The micro-disperse particles can have a substantially uniform diameter of 1-10 microns, and preferably about 3-5 microns. Ruthenium or cobalt catalytic nanoparticles can be incorporated in the micro-disperse particles of sodium borohydride, which allows a rapid and complete reaction to occur without the problems associated with caking and scaling of the surface by the reactant product sodium metaborate. A closed loop water management system can be used to recycle wastewater from a PEM fuel cell to supply water for reacting with the micro-disperse particles of sodium borohydride in a compact hydrogen gas generator. Capillary forces can wick water from a water reservoir into a packed bed of micro-disperse fuel particles, eliminating the need for using an active pump.

Claims

1. A compact hydrogen gas generator for using a compact solid source of hydrogen, comprising:

a substantially planar substrate having an upper surface;

a water-storage cavity recessed into the upper surface of the substrate;

a fuel-storage cavity recessed into the upper surface of the substrate;

a capillary flow channel for transporting water from the water-storage cavity to the fuel-storage cavity by capillary action;

a cover lid, sealingly attached to the upper surface of the substrate, for sealing the two cavities and flow channel;

outlet means for removing hydrogen gas produced during operation;

a packed bed of micro-disperse particles of sodium borohydride disposed within the fuel storage cavity;

and water contained within the water-storage cavity.

2. The hydrogen gas generator of claim 1, wherein the micro-disperse particles of sodium borohydride have a metal catalyst incorporated into the particles.

3. The hydrogen gas generator of claim 1, wherein the water comprises nanoparticles of a metal catalyst suspended therein.

4. The hydrogen gas generator of claim 1, further comprising a valve disposed in the capillary flow channel for controlling the flow of water from the water-storage cavity to the fuel-storage cavity, whereby the rate of hydrogen gas generation is controlled.

5. The hydrogen gas generator of claim 4, wherein the valve comprises a normally-closed MEMS valve activated by an actuator selected from the group consisting of bimetallic and bimorph actuators.

6. The hydrogen gas generator of claim 1, further comprising a pump for pumping water from the water-storage cavity to the fuel-storage cavity.

7. The hydrogen gas generator of claim 1, wherein the thickness of the substrate is less than or equal to 400 microns.

8. The hydrogen gas generator of claim 1, wherein the micro-disperse particles of sodium borohydride have a substantially uniform diameter from about 1 to about 10 microns.

9. The hydrogen gas generator of claim 1, wherein the substrate comprises a material selected from the group consisting of monocrystalline silicon, polysilicon, and silicon nitride.

10. The hydrogen gas generator of claim 1, wherein the substrate comprises silicon;

the cover lid comprises a borosilicate glass; and

the cover lid is anodically bonded to the substrate.