Electrode catalyst for fuel cell and method for production thereof

• US 20050075240A1
• Filed: 10/04/2004
• Published: 04/07/2005
• Est. Priority Date: 10/06/2003
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Yamamoto, Shinji
• Granted Patent: US 7,205,255 B2
• Time in Patent Office: Days
• US Class Current: 502/101
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 4/921 Alloys or mixtures with metallic elements
• CPC Class Codes: H01M 4/925 supported on carriers, e.g. powder carriers
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

An electrode catalyst for a fuel cell is provided which excels in catalytic activity and catalytic durability. The electrode catalyst for the fuel cell has noble metal-containing particle deposited on an electroconductive carrier and the noble metal-containing particle possesses a core-shell structure comprising a core part formed of a noble metal alloy and a shell part formed of a noble metal layer different in composition from the core par and formed on the periphery of the core part. This core-shell structure enables the catalytic activity and the catalytic durability of the electrode catalyst to be enhanced simultaneously.

Claims

1. ) An electrode catalyst for a fuel cell having a noble metal-containing particle deposited on an electroconductive carrier, wherein said noble metal-containing particle possesses a core-shell structure comprising a core part formed of a noble metal alloy and a shell part formed of a noble metal-containing layer different in composition from said core part and formed on the periphery of said core part.

2. ) An electrode catalyst according to claim 1, wherein said noble metal-containing particle comprises a noble metal-containing alloy containing a noble metal and a transition metal.

3. ) An electrode catalyst according to claim 2, wherein said noble metal is an element selected from the group consisting of platinum, palladium, rhodium, osmium, ruthenium, iridium and mixtures of thereof and said transition metal is an element selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and mixtures of thereof.

4. ) An electrode catalyst according to claim 3, wherein said noble metal-containing particle has a platinum content in the range of 50-90 atomic %, the shell part has a platinum content in the range of 80-100 atomic %, and the core part has a platinum content in the range of 40-90 atomic %.

5. ) An electrode catalyst according to claim 3, wherein said noble metal-containing particle has a platinum content in the range of 40-90 atomic %, the shell part has a platinum content in the range of 40-90 atomic %, and the core part has a platinum content in the range of 40-90 atomic %.

6. ) An electrode catalyst according to claim 5, wherein said noble metal-containing particle comprises 40-90 atomic % of platinum, 5-30 atomic % of an element selected from the group consisting of iridium, rhodium, palladium, ruthenium, and mixtures thereof, and 5-30 atomic % of an element selected from the group consisting of cobalt, nickel, chromium, iron, manganese, and mixtures thereof, said core part has a platinum/Y (atomic ratio) in the range of 6/1-2/3 and said shell part has a platinum/X (atomic ratio) in the range of 6/1-2/3.

7. ) An electrode catalyst according to claim 6, wherein X in said shell part is iridium.

8. ) An electrode catalyst according to claim 7, wherein Y in said core part is cobalt.

9. ) An electrode catalyst according to claim 1, wherein said electroconductive carrier comprises an electroconductive carbon particles having a BET surface area in the range of 50-2,000 m²/g.

10. ) A method for the production of an electrode catalyst for a fuel cell comprising a step of depositing a noble metal-containing particle formed of a noble metal alloy on an electroconductive carrier and a step of exposing the surface of said particle to a solution capable of liquating a component other than noble metal, thereby forming a core-shell structure in said particle.

11. ) A method according to claim 10, which further comprises steps of separating said electroconductive carrier having deposited thereon a noble metal-containing particle possessing a core-shell structure from said solution, washing the separated carrier, drying the washed carrier, firing the dried carrier in an atmosphere of an inert gas stream at 200-1,100°

C., and further retaining the fired carrier at 200-600°

C.