Catalyst comprising Pt, Ni, and Cr
Catalysts comprising nanostructured elements comprising microstructured whiskers having an outer surface at least partially covered by a catalyst material comprising at least 90 atomic percent collectively Pt, Ni, and Cr, wherein the Pt is present in a range from 32.4 to 35.8 atomic percent, the Ni is present in a range from 57.7 to 63.7 atomic percent, and the Cr is present in a range from 0.5 to 10.0 atomic percent, and wherein the total atomic percent of Pt, Ni, and Cr equals 100. Catalyst described herein are useful, for example, in fuel cell membrane electrode assemblies.
1. A catalyst comprising nanostructured elements comprising microstructured whiskers having an outer surface at least partially covered by a catalyst material comprising at least 90 atomic percent collectively Pt, Ni, and Cr, wherein, when considering only the collective Pt, Ni, and Cr, the Pt is present in a range from 32.4 to 35.8 atomic percent, the Ni is present in a range from 57.7 to 63.7 atomic percent, and the Cr is present in a range from 0.5 to 10.0 atomic percent, and wherein the total atomic percent of the collective Pt, Ni, and Cr equals 100, wherein the catalyst has an exposed surface layer and the exposed surface layer is a sub-monolayer of chromium.
2. The catalyst of claim 1 , wherein the Pt is present in a range from 33.8 to 35.8 atomic percent, the Ni is present in a range from 60.3 to 63.7 atomic percent, and the Cr is present in a range from 0.5 to 5.9 atomic percent of the collective Pt, Ni, and Cr.
3. The catalyst of claim 1 , wherein the catalyst material comprises a layer comprising platinum and nickel and a layer comprising chromium on the layer comprising platinum and nickel.
4. The catalyst of claim 3 , wherein each layer independently has a planar equivalent thickness up to 25 nm.
5. The catalyst of claim 1 , wherein the catalyst material comprises alternating layers comprising platinum and nickel and layers comprising chromium.
6. The catalyst of claim 5 , wherein each layer independently has a planar equivalent thickness up to 25 nm.
7. The catalyst of claim 1 , wherein the catalyst material comprises a layer comprising platinum, a layer comprising nickel on the layer comprising platinum, and a layer comprising chromium on the layer comprising nickel.
8. The catalyst of claim 1 , wherein the catalyst material comprises a layer comprising nickel, a layer comprising platinum on the layer comprising nickel, and a layer comprising chromium on the layer comprising platinum.
9. The catalyst of claim 1 , wherein the weight ratio of platinum to chromium is in a range from 6:1 to 140:1.
10. The catalyst of claim 1 , wherein the catalyst material has a thickness in a range from 0.1 to 15 nm.
11. A fuel cell membrane electrode assembly comprising the catalyst of claim 1 .
12. A method comprising annealing the catalyst of claim 1 .
13. A method of making the catalyst of claim 1 , the method comprising depositing platinum and nickel from a target comprising platinum and nickel and depositing chromium from a target comprising chromium.