Nanosegregated bimetallic oxide anode catalyst for proton exchange membrane electrolyzer
A surface segregated bimetallic composition of the formula Ru 1-x Ir x wherein 0.1≦x≦0.75, wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole is provided. The surface segregated material may be produced by a method including heating a bimetallic composition of the formula Ru 1-x Ir x , wherein 0.1≦x≦0.75, at a first temperature in a reducing environment, and heating the composition at a second temperature in an oxidizing environment. The surface segregated material may be utilized in electrochemical devices.
1. A method comprising:
heating a bimetallic composition of the formula Ru 1-x Ir x wherein 0.1≦x≦0.75 at a first temperature in a reducing environment; and
heating the composition at a second temperature in an oxidizing environment,
wherein the resulting material exhibits a surface with an Ir concentration that is greater than an Ir concentration of the material as a whole.
2. The method of claim 1 , wherein the reducing environment comprises H 2 in an amount of at least about 3% up to about 5%, with the remainder being an inert gas.
3. The method of claim 1 , wherein the first temperature is at least about 300° C. up to about 500° C.
4. The method of claim 1 , wherein the oxidizing environment comprises pure O 2 .
5. The method of claim 1 , further comprising forming the bimetallic composition by:
forming a solution containing Ru and Ir;
heating the solution to a first reaction temperature;
adding a reducing agent to the solution;
heating the solution to a second reaction temperature; and
recovering nanoparticles of the bimetallic composition.
6. The method of claim 5 , wherein the nanoparticles are recovered by a process comprising:
cooling the solution; and
adding ethanol to the cooled solution to precipitate the nanoparticles.
7. The method of claim 1 , wherein the bimetallic composition is homogeneous prior to heating in the reducing environment.
8. The method of claim 1 , wherein 0.4≦x≦0.6.
9. The method of claim 1 , wherein x=0.5.
10. The method of claim 1 , wherein the Ir concentration of the surface is at least about 10% greater than the Ir concentration of the material as a whole.
11. The method of claim 1 , wherein the surface of the resulting material is substantially free of Ru.
12. A material comprising:
a bimetallic composition of the formula Ru 1-x Ir x wherein 0.1≦x≦0.75,
wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole.
13. The material of claim 12 , wherein the material is in the form of nanoparticles.
14. The material of claim 12 , wherein the material is in the form of nanoparticles with a particle size distribution centered in the range of about 5 nm up to about 10 nm.
15. The material of claim 12 , wherein 0.4≦x≦0.6.
16. The material of claim 12 , wherein x=0.5.
17. The material of claim 12 , wherein the Ir concentration of the surface is at least about 10% greater than the Ir concentration of the material as a whole.
18. The material of claim 12 , wherein the surface of the resulting material is substantially free of Ru.
19. An electrochemical apparatus comprising a bimetallic catalyst composition of the formula Ru 1-x Ir x wherein 0.1≦x≦0.75,
wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole.
20. The electrochemical apparatus of claim 19 , wherein the electrochemical apparatus is a polymer electrolyte membrane electrolyzer.