Method of fabricating electrode catalyst layers with directionally oriented carbon support for proton exchange membrane fuel cell

• US 7,758,921 B2
• Filed: 03/03/2006
• Issued: 07/20/2010
• Est. Priority Date: 05/26/2005
• Status: Expired due to Fees

• Current Assignee: U Chicago Argonne, LLC
• Original Assignee: UChicago Argonne LLC
• Inventors: Yang, Junbing, Liu, Di-Jia
• Primary Examiner(s): Barr; Michael
• Assistant Examiner(s): BOWMAN, ANDREW J
• Application Number:
  US11/368,116
• Publication Number:
  US 20060269827A1
• Time in Patent Office: 1,600 Days
• Field of Search: 428/408, 204/290.14, 429/34
• US Class Current: 427/249.1
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 4/9008 Organic or organo-metallic compounds
• CPC Class Codes: H01M 8/04194 Concentration measuring cells
• CPC Class Codes: H01M 8/1004 characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A method of making a membrane electrode assembly (MEA) having an anode and a cathode and a proton conductive membrane there between. A bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated in the nanotubes forms at least one portion of the MEA and is in contact with the membrane. A combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into a first reaction zone maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is transmitted to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes. The nanotubes are in contact with a portion of the MEA at production or being positioned in contact thereafter. Methods of forming a PEMFC are also disclosed.

Claims

1. A method of making a membrane electrode assembly (MEA) having an anode and a cathode and a proton conductive membrane therebetween, wherein a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated in the nanotubes forms at least one portion of the MEA and is in contact with the membrane, said method comprising the steps of:

(a) introducing a combination of a transition metal-containing carbon nanotube precursor and a gaseous mixture comprising an inert gas and a reducing gas into a first reactor zone maintained at a first temperature and for a period of time sufficient to vaporize the transition metal-containing carbon nanotube precursor, introducing the vaporized material to a second reactor zone maintained at a second temperature that is higher than the first temperature and for a period of time sufficient to pyrolyze the transition metal-containing carbon nanotube precursor, and grow longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes onto a substrate present in the second reactor zone, wherein the substrate is patterned with a template for forming longitudinally-aligned carbon nanotubes perpendicular to the substrate surface, and the carbon nanotube precursor is selected from the group consisting of a transition metal phthalocyanine, a transition metal porphyrin compound, a transition metal organometallic compound, or a combination thereof, optionally as a solution in an aromatic hydrocarbon solvent;

(b) introducing transition metal or precious metal crystallites onto the surface of the nanotubes;

(c) depositing a layer of an ionomeric polymer over the carbon nanotubes and drying the polymer to form a nanotube-containing polymeric decal having an outer polymeric side and an inner nanotube side in contact with the substrate;

(d) fusing the polymeric side of two such decals to both sides of a proton-conductive membrane at an elevated temperature and pressure; and

(e) removing the substrates to thereby form a MEA comprising a proton-conductive membrane core between an anode and a cathode, the anode and cathode each comprising a sheet of longitudinally aligned transition metal-containing carbon nanotubes, wherein the carbon nanotubes are aligned generally perpendicular to the membrane.

2. The method of claim 1, wherein the gaseous mixture comprises argon and hydrogen and optionally includes ammonia, and the transition metal-containing carbon nanotube precursor comprises Fe or Ni or Co or Cr or Mn or mixtures thereof.

3. The method of claim 1, wherein the temperature in the first reactor zone is maintained in the range of from about 150°

C. to about 700°

C. and the temperature in the second reactor zone is maintained in the range of from about 700°

C. to about 1000°

C.

4. The method of claim 1, wherein material is maintained in the reactor zones for a period of time in the range of from about 5 to about 45 minutes.

5. The method of claim 1, wherein the nanotubes form a three dimensional (3D) pattern.

6. The method of claim 1, wherein the carbon nanotube precursor contains a transition metal selected from the group consisting of Fe, Ni, Co and mixtures thereof.

7. The method of claim 1, wherein the nanotubes are generally straight or include spiral or bamboo shaped or bellows shaped nanotubes.

8. The method of claim 1 wherein one transition metal-containing nanotube decal of the MEA includes an oxidation catalyst and the other decal includes a reduction catalyst.

9. The method of claim 1, wherein a plurality of the MEAs are assembled into a proton exchange membrane fuel cell (PEMFC) by alternately stacking bipolar plates between the MEAs.

10. A method of forming a membrane electrode assembly (MEA) for a proton exchange membrane fuel cell (PEMFC), comprising forming an assembly of an anode and a cathode and a proton conductive membrane therebetween, forming longitudinally aligned graphitic nanotubes on one or more of the cathode or the anode by chemical vapor deposition (CVD), at least some of the graphitic nanotubes being in contact with the membrane, wherein the nanotubes are deposited by chemical vapor deposition by pyrolysis of a transition metal-containing organometallic material to form nanotubes that include the transition metal in the nanotube structure.

11. A method of forming a membrane for a proton exchange membrane fuel cell (PEMFC), comprising providing a proton conductive membrane, forming longitudinally aligned graphitic nanotubes with a catalytically active transition metal in the nanotubes on a substrate by chemical vapor deposition (CVD), transferring the longitudinally aligned graphitic nanotubes from or with the substrate to the proton exchange membrane with the longitudinally aligned graphitic nanotubes being generally perpendicular to the proton exchange membrane and in contact therewith, wherein the substrate is a cathode or an anode and most of the nanotubes are in contact with the membrane and the cathode or the anode.