Method of preparing metal catalyst and electrode including the same

Abstract

A method of preparing a metal catalyst including a conductive catalyst material and a coating layer formed of a water repellent material on the surface of the conductive catalyst material includes: obtaining a water repellent material solution by mixing a water repellent material and a first solvent; obtaining a conductive catalyst solution by mixing a conductive catalyst material and a first solvent; mixing the water repellent material solution and the conductive catalyst solution; casting the result onto a supporter, drying the cast result and then separating a metal catalyst in a solid state from the supporter; and pulverizing and sieving the product. Also provided are a metal catalyst prepared using the method, an electrode including the metal catalyst, a method of preparing the electrode, and a fuel cell employing the electrode. A metal catalyst including a coating layer formed of a water repellent material on the surface of a conductive catalyst particle can be obtained by using the method of preparing a metal catalyst. Such a metal catalyst does not sink into a liquid electrolyte since hydrophobicity is efficiently distributed around the conductive catalyst particle. Also, the distribution and movement of the liquid electrolyte, such as phosphoric acid, around the metal catalyst can be controlled. A fuel cell employing the metal catalyst has excellent efficiency and overall performance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIGS. 1A and 1B are schematic diagrams of a metal catalyst according to an embodiment of the present invention and a conventional metal catalyst, respectively;

FIG. 2 is a flow chart illustrating a preparation method of a metal catalyst and an electrode according to an aspect of the present invention; and

FIG. 3 is a graph illustrating current-voltage (I-V) and current-resistance (I-R) characteristics of electrodes prepared according to Example 1 and Comparative Example 1.

Claims

1. A method of preparing a metal catalyst comprising a conductive catalyst material and a coating layer formed of a water repellent material on a surface of the conductive catalyst material, the method comprising: obtaining a water repellent material solution by mixing the water repellent material and a first solvent;obtaining a conductive catalyst solution by mixing the conductive catalyst material and the first solvent;mixing the water repellent material solution and the conductive catalyst solution;casting the mixed water repellent material solution and conductive catalyst solution onto a supporter, drying the cast result and then separating a metal catalyst in a solid state from the supporter; andpulverizing and sieving the separated metal catalyst.

2. The method of claim 1, wherein the first solvent comprises at least one material selected from the group consisting of water, hydrofluoropolyester, N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and trifluoroacetic acid.

3. The method of claim 1, wherein the water repellent material comprises at least one material selected from the group consisting of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxol tetrafluoroethylene copolymer, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidenefluoride, and FLUOROSARF.

4. The method of claim 1, wherein the amount of the water repellent material is in the range of 1 to 50 parts by weight based on 100 parts by weight of the conductive catalyst material.

5. The method of claim 1, wherein the amount of the first solvent used for the obtaining the water repellent material solution is in the range of 500 to 1,500 parts by weight based on 100 parts by weight of the water repellent material, and the amount of the first solvent used for the obtaining the conductive catalyst solution is in the range of 200 to 1,000 parts by weight based on 100 parts by weight of the conductive catalyst material.

6. A metal catalyst prepared by the method of claim 1.

7. A metal catalyst comprising a conductive catalyst material and a coating layer of a water repellent material on surfaces of the metal catalyst.

8. The metal catalyst of claim 7, wherein the amount of the water repellent material is in the range of 1 to 50 parts by weight based on 100 parts by weight of the conductive catalyst material

9. The metal catalyst of claim 7, wherein the water repellent material comprises at least one material selected from the group consisting of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxol tetrafluoroethylene copolymer, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidenefluoride, and FLUOROSARF.

10. A method of preparing an electrode comprising: obtaining a composition for forming a catalyst layer by mixing a metal catalyst prepared using the method of claim 1 with a binder and a second solvent;coating the composition for forming the catalyst layer onto an electrode supporter and drying the composition for forming the catalyst layer; andtreating the dried composition for forming the catalyst layer with an acid solution.

11. The method of claim 10, wherein the binder comprises at least one material selected from the group consisting of polyvinylidenefluoride and vinylidenefluoride-hexafluoropropylene copolymer, and wherein the amount of the binder is in the range of 1 to 10 parts by weight based on 100 parts by weight of the metal catalyst.

12. The method of claim 10, wherein the second solvent comprises a material selected from the group consisting of N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and trifluoroacetic acid.

13. The method of claim 12, wherein the amount of second solvent is in the range of 100 to 500 parts by weight based on 100 parts by weight of the metal catalyst

14. The method of claim 10, wherein the acid solution comprises a phosphoric acid solution.

15. An electrode prepared using the method of claim 10.

16. A fuel cell employing the electrode of claim 15.