Catalyst for fuel cell and method for preparing the same
The present invention provides a support for an electrode of a polymer electrolyte membrane fuel cell, a fuel cell, and a platinum-supported catalyst, and an electrode using the same. In particular, the present invention provides a method in which linear crystalline carbon nanofibers and nonlinear crystalline carbon particles with increased surface area and improved crystallinity are used to enhance the active site of catalyst particles and ensure the durability of the catalyst by the crystalline carbon materials. The linear crystalline carbon nanofibers are grown to have a predetermined fiber diameter by heat treatment at a high temperature in a gas phase of hydrocarbon in an inert gas atmosphere using an oxide such as Ni, Fe, Mn, etc. as a catalyst. The crystallinity of the linear crystalline carbon nanofibers is also improved by the heat treatment. As the nonlinear crystalline carbon particles, commercially available acetylene black that has been heat-treated at a high temperature under steam to expand the surface area and improve the crystallinity, can be used to thereby provide high surface area and ensure excellent oxidation resistance.
1. A method for preparing a catalyst for a fuel cell electrode, the method comprising:
heat-treating a linear crystalline carbon nanofibers of catalyst support at a temperature of 2,000 to 2,800° C. in an inert gas atmosphere to improve oxidation resistance due to an improvement in crystallinity of the carbon nanofibers;
heat-treating a spherical crystalline acetylene black of catalyst support at a temperature of 1,000 to 1,500° C. in a high temperature steam atmosphere to increase the surface area of the acetylene black;
dispersing the linear crystalline carbon nanofibers of catalyst support and the spherical crystalline acetylene black of catalyst support;
mixing the linear crystalline carbon nanofibers of catalyst support and the spherical crystalline acetylene black of catalyst support in a predetermined mixing ratio to form a slurry; and
preparing a platinum-supported catalyst or a platinum alloy-supported catalyst by adding NaOH, a platinum precursor or a platinum alloy precursor, and the mixture of the linear crystalline carbon nanofibers of catalyst support and the spherical crystalline acetylene black of catalyst support to a solvent for catalyst synthesis, and refluxing at a temperature of 140 to 180° C. to reduce the platinum precursor or the platinum alloy precursor,
wherein the linear crystalline carbon nanofibers of catalyst support has a peak diameter of about 30 to 200 nm.
2. The method of claim 1 , wherein the linear crystalline carbon nanofibers of catalyst support is a herringbone carbon support, or a platelet carbon support.
3. The method of claim 1 , wherein the platinum alloy precursor is selected from the group consisting of a platinum-nickel precursor, a platinum-cobalt precursor, and a platinum-palladium precursor.
4. The method of claim 1 , wherein the catalyst is selected from the group consisting of a platinum-supported catalyst, a platinum alloy-supported catalyst in the form of a solid solution, and a platinum alloy-supported catalyst in the form of a core-shell.
5. The method of claim 1 , wherein the linear crystalline carbon nanofibers of catalyst support and the spherical crystalline acetylene black of catalyst support are mixed in a ratio of from 20:80 wt % to 80:20 wt %.
6. A catalyst for a fuel cell electrode prepared by the method of claim 1 .
7. A catalyst for a fuel cell comprising:
two types of crystalline carbon supports, the first type comprising a linear crystalline carbon nanofibers of catalyst support that have been heat-treated to improve crystallinity, the second type comprising a spherical crystalline acetylene black of catalyst support that have been heat-treated in a high temperature steam atmosphere at a temperature of 1,000 to 1,500° C. to increase their surface area,
wherein the ratio of the linear crystalline carbon nanofibers of catalyst support to the spherical crystalline acetylene black of catalyst support ranges from 20:80 wt % to 80:20 wt %,
wherein the linear crystalline carbon nanofibers of catalyst support has a peak diameter of about 30 to 200 nm.
8. The catalyst of claim 7 , wherein the catalyst is a platinum-supported catalyst or a platinum alloy-supported catalyst.