Catalyst with metal oxide doping for fuel cells
The invention relates to a catalyst for fuel cells which comprises a support, at least one catalytically active metal from the platinum group or an alloy comprising at least one metal of the platinum group and also at least one oxide of at least one metal selected from among Ti, Sn, Si, W, Mo, Zn, Ta, Nb, V, Cr and Zr. The invention further relates to a process for producing such a catalyst and its use.
1. A catalyst, comprising:
(A) a support;
(B) at least one catalytically active metal selected from the group consisting of rhodium, iridium, nickel, palladium, platinum, copper, silver, and gold, or an alloy comprising at least one of said catalytically active metals; and
(C) an oxide of at least one metal selected from the group consisting of Ti, Sn, Si, W, Mo, Zn, Ta, Nb, V, Cr, and Zr,
wherein, based on a total weight of components (A), (B), and (C):
a proportion of the at least one metal of the oxide (C) is in a range from 0.01 to 0.9% by weight;
a proportion of component (B) is in a range from 10 to 50% by weight; and
a proportion of component (A) is in a range from 49.1 to 89.99% by weight.
2. The catalyst of claim 1 , wherein the support is selected from the group consisting of a carbon support, a polymer, and a ceramic.
3. The catalyst of claim 1 , wherein (B) is an alloy selected from the group consisting of PtNi, PtFe, PtV, PtCr, PtTi, PtCu, PtPd, PtRu, PdNi, PdFe, PdCr, PdTi, PdCu, and PdRu.
4. A polymer electrolyte fuel cell comprising a cathode which comprises the catalyst of claim 1 .
5. The catalyst of claim 1 , wherein the metal oxide (C) comprises at least one selected from the group consisting of ZrO 2 , SnO 2 , and TiO 2 .
6. The catalyst of claim 1 , wherein the metal oxide (C) comprises ZrO 2 .
7. The catalyst of claim 1 , wherein the metal oxide (C) comprises TiO 2 .
8. The catalyst of claim 1 , wherein the support is carbon.
9. The catalyst of claim 1 , wherein the catalytically active metal (B) is platinum.
10. The catalyst of claim 1 , wherein the catalytically active metal (B) is palladium.
11. The catalyst of claim 1 , wherein a proportion of component (B) in the catalyst is in a range from 20 to 30% by weight, based on a total weight of components (A), (B), and (C).
12. The catalyst of claim 1 , wherein a proportion of the at least one metal of the oxide (C) in the catalyst is in a range from 0.1 to 0.65% by weight, based on a total weight of components (A), (B), and (C).
13. The catalyst of claim 1 , wherein a proportion of the at least one metal of the oxide (C) in the catalyst is in a range from 0.2 to 0.6% by weight, based on a total weight of components (A), (B), and (C).
14. The catalyst of claim 1 , wherein a proportion of component (A) in the catalyst is in a range from 69.1 to 79.99% by weight, based on a total weight of components (A), (B), and (C).
15. The catalyst of claim 1 , wherein a proportion of (C), based on the proportion of metal thereof, in the catalyst is in a range from 0.01 to 0.2% by weight, based on a total weight of components (A), (B), and (C).
16. The catalyst of claim 5 , wherein component (C) additionally comprises an oxide of at least one metal selected from the group consisting of Si, Zn, Ta, Nb, and Cr.
17. A catalyst, comprising:
(A) a support;
(B) at least one catalytically active metal selected from the group consisting of rhodium, iridium, nickel, palladium, platinum, copper, silver, and gold, or an alloy comprising at least one of said catalytically active metals; and
(C) only one oxide of at least one metal selected from the group consisting of Ti, Sn, Si, W, Mo, Zn, Ta, Nb, V, Cr, and Zr,
wherein, based on a total weight of components (A), (B), and (C):
a proportion of the at least one metal of the only one oxide (C) is in a range from 0.01 to 0.9% by weight;
a proportion of component (B) is in a range from 10 to 50% by weight; and
a proportion of component (A) is in a range from 49.1 to 89.99% by weight.
18. A process for producing the catalyst of claim 1 , the process comprising:
(a) depositing a compound comprising at least one catalytically active metal selected from the group consisting of rhodium, iridium, nickel, palladium, platinum, copper, silver, and gold on a support;
(b) depositing a hydrolyzable precursor compound comprising at least one metal oxide selected from the group consisting of Ti, Sn, Si, W, Mo, Zn, Ta, Nb, V, Cr and Zr on the support; and
(c) heat-treating the support,
wherein (a) and (b) are carried out in succession in any order or in parallel, and
wherein (c) is carried out at least twice at a different temperature, the temperature being increased in each successive heat treatment.
19. The process of claim 18 , further comprising, after (a):
mixing the support, which has been coated with a catalytically active metal, with at least one selected from the group consisting of a second catalytically active metal and at least one transition metal,
wherein (b) and (c) are subsequently carried out in any order.
20. The process of claim 18 , wherein the compound comprising the catalytically active metal is Pt(NO 3 ) 2 .
21. The process of claim 18 , wherein (c) is carried out under a reducing atmosphere.
22. The process of claim 18 , wherein the reducing atmosphere comprises hydrogen.
23. The process of claim 18 , wherein the temperature in (c) is in a range from 90 to 900° C.