LAYERED PLATINUM ON FREESTANDING PALLADIUM NANO-SUBSTRATES FOR ELECTROCATALYTIC APPLICATIONS AND METHODS OF MAKING THEREOF

• US 20160276674A1
• Filed: 03/17/2015
• Published: 09/22/2016
• Est. Priority Date: 03/17/2015
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Xie, Shuifen, Choi, Sang-Il, Wang, Xue, Park, Jinho, Xia, Younan, Zhang, Lei
• Granted Patent: US 11,114,671 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B01J 23/42 Platinum
• CPC Class Codes: B01J 23/44 Palladium
• CPC Class Codes: C30B 29/02 Elements
• CPC Class Codes: C30B 29/60 characterised by shape
• CPC Class Codes: C30B 29/66 Crystals of complex geometrical shape, e.g. tubes, cylinders
• CPC Class Codes: C30B 7/005 Epitaxial layer growth
• CPC Class Codes: C30B 7/14 the crystallising materials being formed by chemical reactions in the solution
• CPC Class Codes: H01M 2008/1095 Fuel cells with polymeric electrolytes
• CPC Class Codes: H01M 4/8657 layered
• CPC Class Codes: H01M 4/92 Metals of platinum group H01M4/94 , H01M4/9058 take precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Core-shell nanostructures with platinum overlayers conformally coating palladium nano-substrate cores and facile solution-based methods for the preparation of such core-shell nanostructures are described herein. The obtained Pd@Pt core-shell nanocatalysts showed enhanced specific and mass activities towards oxygen reduction, compared to a commercial Pt/C catalyst.

Claims

1. A core-shell nanostructure comprising a palladium nano-substrate conformally coated with one or more uniform atomic overlayers of epitaxially deposited zero-valent platinum atoms.

2. The core-shell nanostructure of claim 1, wherein the palladium nano-substrate has a shape selected from the group consisting of cubic, concave cubic, tetrahedral, bipyramidal, octahedral, icosahedral, decahedral, rod, bar, wire, and plate shapes.

3. The core-shell nanostructure of claim 2, wherein the palladium nano-substrate shape is perfect or wherein edges and/or corners of the palladium nano-substrate shape are truncated.

4. The core-shell nanostructure of claim 1, wherein the palladium nano-substrate has {100}, {111} facets and/or twin defects on the nano-substrate surface.

5. The core-shell nanostructure of claim 1, wherein the number of platinum atomic overlayers deposited is in the range of about one to about ten atomic overlayers.

6. The core-shell nanostructure of claim 1, wherein the entire surface of the palladium nano-substrate is covered by a continuous and uniform shell of the one or more platinum overlayers deposited.

7. The core-shell nanostructure of claim 1, wherein the one or more zero-valent platinum overlayers formed on the palladium nano-substrate have a corrugated surface morphology.

8. The core-shell nanostructure of claim 1, wherein the core-shell nanostructure has a size of about one to about one hundred nanometers.

9. The core-shell nanostructure of claim 1, wherein the core-shell nanostructure has a shape selected from the group consisting of cubic, octahedral, and icosahedral shapes;

and the core-shell nanostructure shapes are perfect or truncated.

10. A method of producing core-shell nanostructure formed of a palladium nano-substrate conformally coated with one or more uniform overlayers of epitaxially deposited zero-valent platinum atoms, the method comprising the steps of:

(1) combining a first solution comprising a plurality of palladium nano-substrates and a reducing agent with a second solution comprising a platinum-containing compound to form a mixture; and

(2) heating the mixture at a temperature in the range of about 75°

C. to about 250°

C. to induce epitaxial layer-by-layer deposition of one or more zero-valent platinum overlayers conformally deposited on the palladium nano-substrates.

11. The method of claim 10, wherein the palladium nano-substrate has a shape selected from the group consisting of cubic, concave cubic, tetrahedral, bipyramidal, octahedral, icosahedral, decahedral, rod, bar, wire, and plate shapes.

12. The method of claim 11, wherein the palladium nano-substrate shape is perfect.

13. The method of claim 11, wherein edges and/or corners of the palladium nano-substrate shape are truncated.

14. The method of claim 10, wherein the first and second solutions are prepared in a polyol-type solvent selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol.

15. The method of claim 10, wherein the first and second solutions are prepared in deionized water as a solvent.

16. The method of claim 10, wherein the reducing agent is selected from the group consisting of L-ascorbic acid, citric acid, formaldehyde, formic acid, poly(vinyl pyrrolidone), sodium citrate, glucose, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol.

17. The method of claim 16, wherein the reducing agent is L-ascorbic acid or citric acid.

18. The method of claim 10, wherein the platinum-containing compound is selected from the group consisting of platinum(II) chloride, platinum(IV) chloride, platinum(II) bromide, chloroplatinic acid, sodium tetrachloroplatinate(II), sodium hexachloroplatinate(IV), potassium tetrachloroplatinate(II), potassium hexachloroplatinate(IV), tetraammineplatinum(II) chloride, tetraammineplatinum(II) nitrate, ammonium tetrachloroplatinate(II), ammonium hexachloroplatinate(IV) and platinum(II) acetylacetonate.

19. The method of claim 10, wherein the step of combining the first and second solutions comprises adding the second solution to the first solution in one single shot addition.

20. The method of claim 10, wherein the step of combining the first and second solutions comprises adding the second solution to the first solution at a rate of addition of about 4.0 mL h⁻

1.