Platinum nickel nanowires as oxygen reducing electrocatalysts and methods of making the same
Aspects disclosed herein relate to methods for producing nanostructured metal catalysts that can be used in various alternative fuel applications.
1. A method comprising:
a first mixing of a starting nanostructure consisting essentially of nickel with a solution comprising a platinum salt to produce by spontaneous Galvanic displacement a first nanostructure intermediate comprising platinum at a first concentration between 7.3 wt % and 16.4 wt % and nickel;
a first annealing of the first nanostructure intermediate in the presence of a first gas comprising hydrogen (H 2 ) to produce a second nanostructure intermediate;
a second mixing of the second nanostructure intermediate with an acid to produce a third nanostructure intermediate comprising platinum at a second concentration between 17.5 wt % and 40 wt %; and
a second annealing of the third nanostructure intermediate in the presence of a second gas comprising oxygen (O 2 ) to produce a final nanostructure, wherein:
the second nanostructure intermediate lacks the platinum (111) peak, when tested by x-ray diffraction.
2. The method of claim 1 , wherein the starting nanostructure comprises at least one of a fiber, a wire, a filament, a thread, a whisker, a ribbon, or a helix.
3. The method of claim 2 , wherein:
the starting nanostructure has a length and a diameter, and
the length and the diameter define an aspect ratio between 1:1 and 100:1.
4. The method of claim 3 , wherein the diameter is between 200 nm and 300 nm.
5. The method of claim 3 , wherein the length is between 100 μm and 200 μm.
6. The method of claim 1 , wherein the acid comprises at least one of hydrochloric acid, acetic acid, nitric acid, or sulfuric acid.
7. The method of claim 1 , wherein the platinum salt comprises at least one of potassium tetrachloroplatinate or dipotassium platinum hexachloride.
8. The method of claim 1 , wherein the first mixing is performed at a temperature of about 90° C.
9. The method of claim 1 , wherein the first annealing is performed at a temperature between 150° C. and 500° C.
10. The method of claim 1 , wherein the first gas comprises H 2 at about 10 volume %.
11. The method of claim 1 , wherein the second mixing is performed at about room temperature.
12. The method of claim 1 , wherein the third nanostructure has a length between about 1 μm to about 100 μm.
13. The method of claim 1 , wherein the second annealing is performed at a temperature of about 175° C.
14. The method of claim 1 , wherein the second gas comprises O 2 at about 100 volume %.
15. The method of claim 1 , wherein the final nanostructure has an oxygen reduction reaction activity between about 1000 mA mg Pt −1 and about 2500 mA mg Pt −1 .