Dry floc method for making an electrochemical cell electrode

• US 4,287,232 A
• Filed: 06/28/1978
• Issued: 09/01/1981
• Est. Priority Date: 06/28/1978
• Status: Expired due to Term

• Current Assignee: United Technologies Corporation (Rtx Corporation)
• Original Assignee: United Technologies Corporation (Rtx Corporation)
• Inventors: Goller, Glen J., Salonia, Joseph R.
• Primary Examiner(s): Smith, Ronald H.
• Assistant Examiner(s): BUEKER, RICHARD R
• Application Number:
  US05/920,036
• Time in Patent Office: 1,161 Days
• Field of Search: 427/42, 427/113, 427/115, 427/369, 427/376 R, 427/376 E, 427/185, 427/296, 427/180, 427/376.1, 427/376.6, 429/42
• US Class Current: 427/113
• CPC Class Codes: B05D 1/16 Flocking otherwise than by spraying
• CPC Class Codes: B05D 3/0493 using vacuum
• CPC Class Codes: H01M 4/8807 Gas diffusion layers
• CPC Class Codes: H01M 4/886 Powder spraying, e.g. wet or dry powder spraying, plasma spraying
• CPC Class Codes: H01M 4/8885 Sintering or firing
• CPC Class Codes: H01M 4/8896 Pressing, rolling, calendering membrane electrode assemblies H01M8/1004
• CPC Class Codes: H01M 8/0234 Carbonaceous material
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A method for making an electrochemical cell electrode involves depositing a layer of dry carbon/hydrophobic polymer floc powder on the surface of a substrate by dispersing the powder as a cloud in a chamber over the substrate and pulling the powder onto the substrate by drawing a vacuum under the substrate. The electrode is subsequently compacted and sintered. Typically the carbon component of the floc is catalyzed, such as with platinum. Thus, the method is for applying a catalyst layer on an electrode substrate. The method is particularly adapted to the high speed manufacture of electrodes.

Claims

1. A method for making an electrochemical cell electrode comprising the steps of:

applying a uniform layer of dry, powdered, carbon/hydrophobic polymer floc on the surface of a porous electrode substrate with virtually no floc within the pores of the substrate by positioning the substrate under a chamber having a bottom edge wherein the said bottom edge of the chamber fits against the edge of the substrate, dispersing the floc as a cloud of powder in the chamber over said surface of said positioned substrate and pulling the floc onto said surface by drawing a continuous vacuum under the substrate until the desired amount of powder has been deposited, wherein said substrate is graphitized carbon paper made from carbon fibers;

compacting the applied floc layer; and

,

sintering the compacted layer.

2. The method according to claim 1 wherein the hydrophobic polymer is PTFE.

3. The method according to claim 1 wherein the electrode substrate has an open porosity of at least 80%.

4. The method according to claim 1 wherein the particle size of the floc powder is no greater than about ten microns.

5. The method according to claim 1 wherein the carbon particles in the floc are precatalyzed.

6. The method according to claim 1 wherein the floc is a precatalyzed carbon/PTFE floc, the catalyst comprising platinum.

7. The method according to claim 1 wherein the mean particle size of the powdered floc is no greater than about one micron.

14. The method according to claim 1 or 8 wherein the step of dispersing the floc in the chamber includes introducing a predetermined amount of the floc into the chamber and maintaining the vacuum until all of said predetermined amount of floc has been drawn to the surface.

8. A method for making an electrochemical cell electrode comprising the steps of:

forming a co-suspension of carbon particles and hydrophobic polymer particles;

floccing the co-suspension;

drying the floc so produced and reducing it to a powder;

applying a uniform layer of the powder on the surface of a porous electrode substrate with virtually no floc within the pores of the substrate by positioning the substrate under a chamber having a bottom edge wherein the said bottom edge of the chamber fits against the edge of the substrate, dispersing the floc as a cloud of powder in the chamber over said surface of said positioned substrate and pulling the floc onto said surface by drawing a continuous vacuum under the substrate until the desired amount of powder has been deposited, wherein said substrate is graphitized carbon paper made from carbon fibers;

compacting the applied floc layer; and

,

sintering the compacted layer.

9. The method according to claim 8 wherein the dry floc powder particles have a mean particle size of about one micron or less.

10. The method according to claim 9 wherein the polymer comprises PTFE and the carbon particles are precatalyzed.

11. The method according to claim 9 wherein the electrode substrate has an open porosity of at least 80%.

12. The method according to claim 10 wherein the catalyst is platinum, said dry floc powder includes a small amount of phosphoric acid, and before compacting said floc layer moisture accumulated therein is removed by heating said layer.

13. The method according to claim 9 wherein the maximum particle size of the floc is about ten microns.