Platinum Alloy Carbon-Supported Catalysts

1 . A carbon-supported platinum alloy catalyst obtainable by simultaneous chemical reduction of in situ-formed platinum dioxide and of at least one transition metal hydrous oxide on a carbon support.

2 . The catalyst of claim 1 wherein said carbon support is a carbon black having an active area not less than 50 m 2 /g.

3 . The catalyst of claim 1 wherein said in situ-formed platinum dioxide is obtained by conversion of dihydrogen hexahydroxyplatinate on said carbon support.

4 . The catalyst of claim 1 wherein said at least one transition metal hydrous oxide is obtained by conversion of a soluble salt on said carbon support.

5 . The catalyst of claim 4 wherein said soluble salt is a nitrate.

6 . The catalyst of claim 1 wherein said transition metal is selected from the group consisting of Ni, Cr, Co, V and Fe.

7 . The catalyst of claim 1 wherein said chemical reduction is carried out with hydrogen gas at a temperature of at least 300° C.

8 . The catalyst of claim 1 further subjected to an annealing treatment in a controlled atmosphere at a temperature of at least 600° C.

9 . The catalyst of claim 8 wherein said controlled atmosphere is an inert argon or nitrogen atmosphere.

10 . A gas-diffusion electrode comprising an electrically conductive web, and a catalyst of claim 1 incorporated therein.

11 . A membrane-electrode assembly comprising an ion-exchange membrane and at least one gas diffusion electrode of claim 10 incorporated therein.

12 . A method for the production of a carbon-supported platinum alloy catalyst comprising simultaneously reducing in situ-formed platinum dioxide and at least one transition metal hydrous oxide on a carbon support.

13 . The method of claim 12 wherein said in situ formation of platinum dioxide is obtained by converting a dihydrogen hexahydroxyplatinate precursor on said carbon support by a variation of pH and/or temperature.

14 . The method of claim 12 wherein said at least one transition metal hydrous oxide is obtained by converting a soluble salt on said platinum dioxide-containing carbon support by a variation of pH and/or temperature.

15 . The method of claim 13 wherein said variations of pH are obtained by the addition of alkali, optionally caustic soda, or ammonia.

16 . The method of claim 15 wherein said addition of alkali or ammonia is effected up to a pH between 2 and 9.

17 . The method of claim 13 wherein said variation of temperature consists of bringing said aqueous solution from room temperature to a final temperature of 30 to 100° C.

18 . The method of claim 12 wherein said carbon support is a carbon black having an active area not less than 50 m 2 /g.

19 . The method of claim 18 wherein said carbon black is slurried in a strong acid.

20 . The method of claim 12 wherein said transition metal is selected from the group consisting of Ni, Cr, Co, V and Fe.

21 . The method of claim 14 wherein said transition metal soluble salt is a nitrate.

22 . The method of claim 12 wherein said chemical reduction is carried out with hydrogen gas at a temperature of at least 300° C.

23 . The method of claim 22 further comprising an annealing treatment in a controlled atmosphere at a temperature of at least 600° C.

24 . The method of claim 23 wherein said controlled atmosphere is an inert atmosphere.