Self supporting structurally engineered non-platinum electrocatalyst for oxygen reduction in fuel cells

• US 7,678,728 B2
• Filed: 10/16/2007
• Issued: 03/16/2010
• Est. Priority Date: 10/16/2006
• Status: Active Grant

• Current Assignee: UNM Rainforest Innovations (f/k/a STC.UNM) (The University of New Mexico)
• Original Assignee: UNM Rainforest Innovations (f/k/a STC.UNM) (The University of New Mexico)
• Inventors: Olson, Tim, Atanassov, Plamen
• Primary Examiner(s): Mayes; Melvin C
• Assistant Examiner(s): Forrest; Michael
• Application Number:
  US11/872,836
• Publication Number:
  US 20080312073A1
• Time in Patent Office: 882 Days
• Field of Search: 502/164
• US Class Current: 502/164
• CPC Class Codes: B01J 2531/025 Ligands with a porphyrin ring system or analogues thereof, e.g. phthalocyanines, corroles
• CPC Class Codes: B01J 2531/845 Cobalt
• CPC Class Codes: B01J 31/06 containing polymers organometallic polymers B01J31/123; polymer-bound organometallic complexes B01J31/165; coordination polymers B01J31/1691
• CPC Class Codes: B01J 31/183 with more than one complexing nitrogen atom, e.g. phenanthroline
• CPC Class Codes: C07D 487/22 in which the condensed system contains four or more hetero rings
• CPC Class Codes: H01M 4/9008 Organic or organo-metallic compounds
• CPC Class Codes: H01M 4/9091 Unsupported catalytic particles; loose particulate catalytic materials, e.g. in fluidised state
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A highly dispersed, unsupported, electrocatalyst made of pyrolyzed porphyries and a method for synthesizing the same. The disclosed synthesis procedure allows for optimization of pore size and therefore transport properties. Compounds suitable for use include transition metal N₄-chelates such as, but not necessarily limited to, N₄-chelates containing different metal centers including Co, Fe, Mn, Ni, Ru, Cu, etc., and other N₄-chelates such as porphyrin, phthalocyanies, and structures based on their pyro products.

Claims

1. A method for producing a non-platinum electrocatalyst suitable for use in a fuel cell comprising:

providing a plurality of removable template particles;

precipitating a transition metal N₄-chelate precursor made of 50;

50 molar percent H₂ tetraphenyl porphyrin and cobalt tetraphenyl porphyrin onto the plurality of removable template particles to produce a dispersed precursor;

pyrolyzing the dispersed precursor to produce a pyropolymer; and

removing the template particles to produce a highly dispersed, self supported, high surface area electrocatalytic material;

wherein the removable template particles and N₄-chelate precursors are selected for use so as to shift the reaction mechanism of the electrocatalytic material towards the 4 e- pathway.

2. The method of claim 1 wherein the plurality of removable template particles are silica-based.

3. The method of claim 2 wherein the silica-based template particles are amorphous silica.

4. The method of claim 2 wherein the silica-based particles are mesoporous.

5. The method of claim 2 wherein the silica-based template particles are removed by chemical etching.

6. The method of claim 1 further comprising selecting removable template particles to use so as to produce electrocatalytic material with a desired pore size.

7. A highly dispersed, unsupported catalytic material substantially consisting of pyrolyzed porphyries manufactured using the method of claim 1.

8. A highly dispersed, unsupported catalytic material substantially consisting of pyrolyzed porphyries formed from a precursor made of 50:

50 molar percent H₂ tetraphenyl porphyrin and cobalt tetraphenyl porphyrin.

9. The material of claim 8 comprising pores between 3 nm and 10 nm in diameter.

10. The material of claim 8 comprising pores between 30 nm and 70 nm in diameter.

11. The material of claim 8 comprising cobalt atom centers bonded to one, two, three, or four nitrogen atoms in the 2⁺ form and cobalt particles coated in a thin oxide film deposited on the pyropolymer backbone.

12. A method for producing a non-platinum electrocatalyst suitable for use in a fuel cell comprising:

providing a plurality of removable template particles;

precipitating a transition metal N₄-chelate precursor made of 50;

50 molar percent H₂ tetraphenyl porphyrin and cobalt tetraphenyl porphyrin onto the plurality of removable template particles to produce a dispersed precursor;

pyrolyzing the dispersed precursor to produce a pyropolymer; and

removing the template particles to produce a highly dispersed, self supported, high surface area electrocatalytic material.

13. The method of claim 12 wherein the plurality of removable template particles are silica-based.

14. The method of claim 13 wherein the silica-based template particles are amorphous silica.

15. The method of claim 13 wherein the silica-based particles are mesoporous.

16. The method of claim 13 wherein the silica-based template particles are removed by chemical etching.

17. The method of claim 12 further comprising selecting removable template particles to use so as to produce electrocatalytic material with a desired pore size.