Finely particulated colloidal platinum compound and sol for producing the same, and method of preparation of fuel cell electrodes and the like employing the same

• US 4,044,193 A
• Filed: 12/20/1974
• Issued: 08/23/1977
• Est. Priority Date: 06/16/1971
• Status: Expired

• Current Assignee: WALTER JUDA AND Walter Juda Associates, Inc./OR WALTER JUDA ASSOCIATES
• Original Assignee: Prototech AS
• Inventors: Allen, Robert J., Petrow, Henry G.
• Primary Examiner(s): Mack, John H.
• Assistant Examiner(s): Feeley, H. A.
• Application Number:
  US05/534,731
• Time in Patent Office: 977 Days
• Field of Search: 136/120 FC, 252/447, 75/22, 75/102, 429/40, 429/42, 429/44
• US Class Current: 429/442
• CPC Class Codes: B01J 23/40 of the platinum group metals
• CPC Class Codes: B01J 23/42 Platinum
• CPC Class Codes: C01G 55/00 Compounds of ruthenium, rhodium, palladium, osmium, iridium, or platinum
• CPC Class Codes: C25B 11/081 the element being a noble metal
• CPC Class Codes: H01M 2004/8684 Negative electrodes
• CPC Class Codes: H01M 2004/8689 Positive electrodes
• CPC Class Codes: H01M 2300/0008 Phosphoric acid-based
• CPC Class Codes: H01M 4/92 Metals of platinum group H01M4/94 , H01M4/9058 take precedence
• CPC Class Codes: H01M 4/925 supported on carriers, e.g. powder carriers
• CPC Class Codes: H01M 4/926 on carbon or graphite
• CPC Class Codes: H01M 8/086 Phosphoric acid fuel cells [PAFC]
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

This disclosure deals with novel very fine, particulated colloidal platinum of the 15-25 Angstrom size range of unusual catalytic activity and particularly adapted for adsorption or other deposition upon carbon for use as fuel cell catalytic electrodes and the like and produced from platinum colloids and sols including complex platinum sulfite compounds and sols derived therefrom.

Claims

1. In a fuel cell and the like, a catalytic electrode comprising an electrically conductive high surface area substrate on which has been deposited platinum particles of the order of substantially 15 to 25 Angstroms in particle size and in which said particles are formed from one of an oxidative decomposition of a platinum complex comprising an oxidizable ligand, and hydrolysis of a non-complex platinum salt solution.

2. In a fuel cell and the like, a catalytic electrode as claimed in 1 and in which the platinum loads the electrode surface in the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm².

3. In a fuel cell and the like, a catalytic electrode comprising an electrically-conducting high surface area carbon substrate on which has been deposited substantially uniformly platinum particles having a particle size substantially in the range of 15 to 25 Angstroms and being formed from the oxidative decomposition of a platinum complex comprising an oxidizable ligand.

4. In a fuel cell and the like, a catalytic electrode as claimed as in claim 3 and in which said complex is selected from the group consisting of platinum sulfite and platinum nitrite complexes.

5. In a fuel cell and the like, a catalytic electrode as claimed in claim 4 and in which said particles are reduced subsequent to said oxidative decomposition.

6. In a fuel cell and the like, a catalytic electrode as claimed in claim 4 and in which the platinum loads the electrode surface in the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm².

7. In a fuel cell and the like, a catalytic electrode as claimed in claim 4 and in which said platinum sulfite complex is the compound having the composition corresponding substantially to H₃ Pt(SO₃)₂ OH.

8. A fuel cell comprising a catalytic electrode having an electrically-conducting high surface area carbon substrate on which has been deposited substantially uniformly platinum particles having a particle size substantially in the range of 15 to 25 Angstroms and formed from the oxidative decomposition of a platinum complex comprising an oxidizable ligand, said complex being selected from the group consisting of platinum sulfite and platinum nitrite complexes and said particles being reduced subsequent to said oxidative decomposition, said fuel cell being a phosphoric acid electrolyte fuel cell with air-hydrogen electrode supply means, and said electrode being provided with means for enabling the drawing of current flowing through the cell.

9. A fuel cell as claimed in claim 8 and in which said electrode is a catalytic anode, and in which said air-hydrogen electrode supply means comprise a source of hydrogen containing carbon monoxide impurity.

10. A fuel cell as claimed in claim 9 wherein said catalytic anode has a platinum loading in the range of from substantially 0.04 milligrams/cm² to 0.25 milligrams/cm².

11. A fuel cell as claimed in claim 8 and in which the said carbon is composited with fluorinated hydrocarbon polymer.

12. In the method of preparing electrodes for fuel cells and the like comprising platinum-on-carbon electro-catalyst, the steps of providing aqueous colloidal platinum-containing sol having an average platinum particle size substantially of the order of 15-25 Angstroms, depositing said platinum contained in said sol on an electrically-conducting carbon substrate, and controlling the depositing to cause the carbon to nucleate the deposit and limit the formation of platinum particles on said carbon to said size.

13. In a fuel cell and the like, an electrode comprising a platinum-on-carbon electrocatalyst, said electrode being produced by a process including the steps of oxidizing the ligand of a complex platinum compound comprising an oxidizable ligand to substantially non-complexing products by means of a non-complexing oxidant, producing therefrom an aqueous dispersion comprising the products of said oxidation, depositing the platinum compound contained in said dispersion on an electrically conducting carbon substrate, and decomposing said platinum compound thereon, thereby forming platinum particles on said carbon having an average particle size of the order of substantially 15-25 Angstroms.

14. In a fuel cell and the like, an electrode produced by the process of claim 13 wherein said complex platinum compound is platinum sulfite and it is subjected to air oxidation.

15. In a fuel cell and the like, an electrode produced by the process of claim 14 wherein said complex platinum sulfite contains groups of (OH) and H₃ Pt(SO₃)₂.

16. In a fuel cell and the like, an electrode produced by the process of claim 14 wherein said air oxidation is carried out at about 135°

C.

17. In a fuel cell and the like, an electrode produced by the process of claim 13 wherein said dispersion contains the product of said complex platinum sulfite and a non-complexing oxidant, said oxidation being carried out in said dispersion.

18. In a fuel cell and the like, an electrode produced by the process of claim 17 wherein said oxidant is selected from the group consisting of hydrogen peroxide, potassium permanganate and persulfuric acid.

19. In a fuel cell and the like, an electrode produced by the process of claim 17 wherein said complex platinum sulfite is selected from the group of compounds having substantially the composition of Na₆ Pt(SO₃)₄ and H₃ Pt(SO₃)₂ OH and mixtures thereof.

20. In a fuel cell and the like, an electrode produced by the process of claim 17 wherein said complex platinum sulfite is the compound having the composition of Na₆ Pt(SO₃)₄ and wherein said compound is in an aqueous sulfuric acid solution.

21. In a fuel cell and the like, an electrode produced by the process of claim 19 wherein said oxidation is effected with H₂ 0₂.

22. In a fuel cell and the like, an electrode produced by the process of claim 13 wherein said oxidation is carried out in the presence of said carbon substrate in finely divided form.

23. In a fuel cell and the like, an electrode produced by the process of claim 13 wherein said complex platinum compound is formed in said dispersion by reacting a solution of chloroplatinic acid and the like with a sulfiting agent.

24. In a fuel cell and the like, an electrode produced by the process of claim 23 wherein said oxidation is effected thermally in air, and said decomposing following depositing on the carbon is effected by reducing the same.

25. In a fuel cell and the like, a catalytic electrode comprising an electrically conductive high surface area carbon substrate on which has been deposited platinum particles of the order of substantially 15 to 25 Angstroms in particle size and in which said platinum loads the electrode surface in the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm².

26. A fuel cell comprising a catalytic cathode electrode having an electrically conductive high surface area carbon substrate on which has been deposited platinum particles substantially of the order of 15 to 25 Angstroms in particle size, said electrode having an electrode surface platinum loading within the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm², said fuel cell being an air-hydrogen high temperature fuel cell with a phosphoric acid electrolyte and being capable of producing in excess of 100 Amperes per square foot of electrode area at a cell voltage of at least 0.5 volts.

27. A fuel cell as claimed in claim 26 and in which the platinized carbon is admixed with a fluorinated hydrocarbon polymer.

31. A fuel cell as claimed in claim 26 and in which means is provided for operating said cathode electrode at a temperature of from substantially 135°

to substantially 190°

C.

28. A fuel cell comprising a catalytic anode electrode having an electrically conductive high surface area carbon substrate on which has been deposited platinum particles substantially of the order of 15 to 25 Angstroms in particle size, said electrode having an electrode surface platinum loading within the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm², said fuel cell being an air-hydrogen high temperature fuel cell with a phosphoric acid electrolyte, said hydrogen comprising carbon monoxide impurity, and said fuel cell being capable of producing in excess of 100 Amperes per square foot of electrode area at a cell voltage of at least 0.5 volts.

29. A fuel cell as claimed in claim 28 and in which the platinized carbon is admixed with a fluorinated hydrocarbon polymer.

30. A fuel cell as claimed in claim 28, and in which said fuel cell comprises a catalytic cathode having an electrically conductive high surface area carbon substrate on which substrate has been deposited platinum particles substantially of the order of 15 to 25 Angstroms in particle size, the platinum loading of the cathode surface being within the range of from substantially 0.04 milligrams/cm² to 0.5 milligrams/cm², said fuel cell having connected thereto fuel and oxidant supply means and means for enabling drawing current through the cell.

32. A fuel cell as claimed in claim 28 and in which means is provided for operating said anode electrode at a temperature of from substantially 170°

to substantially 190°

C.

33. A fuel cell comprising a catalytic electrode having an electrically conductive high surface area carbon substrate on which has been deposited platinum particles of the order of substantially 15 to 25 Angstroms in particle size and formed from a complex platinum sulfite selected from the group of compounds having substantially the composition of Na₆ Pt(SO₃)₄ and H₃ Pt(SO₃)₂ OH and mixtures thereof.

34. A fuel cell as claimed in claim 33 and in which said fuel cell comprises an additional electrode, an electrolyte, fuel and oxidant supply means, and means for enabling the drawing of current flowing through the cell.