Electrode catalyst for fuel cell

Abstract

Disclosed is an electrode catalyst comprising: (a) a support with a specific surface area of at least 1200 m 2 /g; and (b) platinum or platinum-containing alloy particles on the support, wherein the platinum is supported on the electrode catalyst in an amount of 56˜90 wt % based on the total weight of the electrode catalyst. A membrane electrode assembly (MEA) comprising the electrode catalyst and a fuel cell using the MEA are also disclosed. The electrode catalyst comprises platinum or platinum-containing alloy particles highly dispersed on a support with a large surface area in an amount of 56 wt % or more, and thus has an extended catalytically active region, resulting in improvement in the quality of a fuel cell.

1 . An electrode catalyst comprising: 
 (a) a support with a specific surface area of 1200 m 2 /g or more; and    (b) platinum or platinum-containing alloy particles supported on the support,    wherein the platinum is supported on the electrode catalyst in an amount of 56˜90 wt % based on the total weight of the electrode catalyst.    
     
     
         2 . The electrode catalyst according to  claim 1 , wherein the support is selected from the group consisting of porous carbon, conductive polymers and metal oxides.  
     
     
         3 . The electrode catalyst according to  claim 1 , wherein the platinum-containing alloy comprises at least one metal selected from the group consisting of ruthenium (Ru), palladium (Pd), gold (Au), silver (Ag), iridium (Ir), rhodium (Rh) and osmium (Os).  
     
     
         4 . The electrode catalyst according to  claim 1 , wherein the platinum or platinum-containing alloy particles have a particle size of 3.5 nm or less.  
     
     
         5 . The electrode catalyst according to  claim 1 , which comprises platinum or platinum-containing alloy particles with a size of less than 3 nm, loaded on the support with a specific surface area of 1200 m 2 /g or more, wherein platinum is loaded on the support in an amount of at least 70 wt % based on the total weight of the electrode catalyst.  
     
     
         6 . The electrode catalyst according to  claim 5 , wherein the particle size of the platinum or platinum-containing alloy particles is 1.5˜2.9 nm.  
     
     
         7 . The electrode catalyst according to  claim 1 , which comprises platinum or platinum-containing alloy particles with a size of 3˜3.5 nm, loaded on the support with a specific surface area of 1200 m 2 /g or more, wherein platinum is loaded on the support in an amount of at least 80 wt % based on the total weight of the electrode catalyst.  
     
     
         8 . A membrane electrode assembly (MEA), which comprises: 
 (a) a first electrode having a first catalyst layer;    (b) a second electrode having a second catalyst layer; and    (c) an electrolyte membrane interposed between the first electrode and the second electrode,    wherein either or both of the first catalyst layer and the second catalyst layer comprise the electrode catalyst as defined in  claim 1 , which comprises (i) a support with a specific surface area of 1200 m 2 /g or more; and (ii) platinum or platinum-containing alloy particles loaded on the support, wherein platinum is supported on the electrode catalyst in an amount of 56˜90 wt % based on the total weight of the electrode catalyst.    
     
     
         9 . The membrane electrode assembly (MEA) according to  claim 8 , wherein the support is selected from the group consisting of porous carbon, conductive polymers and metal oxides.  
     
     
         10 . The membrane electrode assembly (MEA) according to  claim 8 , wherein the platinum-containing alloy comprises at least one metal selected from the group consisting of ruthenium (Ru), palladium (Pd), gold (Au), silver (Ag), iridium (Ir), rhodium (Rh) and osmium (Os).  
     
     
         11 . The membrane electrode assembly (MEA) according to  claim 8 , wherein the platinum or platinum-containing alloy particles have a particle size of 3.5 nm or less.  
     
     
         12 . The membrane electrode assembly (MEA) according to  claim 8 , which comprises platinum or platinum-containing alloy particles with a size of less than 3 nm, loaded on the support with a specific surface area of 1200 m 2 /g or more, wherein platinum is loaded on the support in an amount of at least 70 wt % based on the total weight of the electrode catalyst.  
     
     
         13 . The membrane electrode assembly (MEA) according to  claim 12 , wherein the particle size of the platinum or platinum-containing alloy particles is 1.5˜2.9 nm.  
     
     
         14 . The membrane electrode assembly (MEA) according to  claim 8 , which comprises platinum or platinum-containing alloy particles with a size of 3˜3.5 nm, loaded on the support with a specific surface area of 1200 m 2 /g or more, wherein platinum is loaded on the support in an amount of at least 80 wt % based on the total weight of the electrode catalyst.  
     
     
         15 . A fuel cell comprising the membrane electrode assembly as defined in  claim 8 .  
     
     
         16 . A method for preparing an electrode catalyst comprising 56-90 wt % of platinum supported thereon, which comprises the steps of: 
 (a) dispersing a support with a specific surface area of 1200 m 2 /g or more into a solvent to form a support dispersion, and adding a pH modifier thereto to provide an alkalified support dispersion;    (b) adding a platinum precursor or platinum-containing alloy precursor compound and a pH modifier to the dispersion obtained from step (a), and further adding a reducing agent thereto to perform reaction of the mixture; and    (c) drying the powder obtained from step (b).    
     
     
         17 . The method according to  claim 16 , wherein the dispersion in step (b) has a pH of 8˜11.  
     
     
         18 . The method according to  claim 16 , wherein steps (a) and (b) are performed at a temperature of 50° C. or higher.  
     
     
         19 . The method according to  claim 16 , wherein step (b) is performed by adding the platinum-containing solution and the pH modifier to the support dispersion, in a portionwise manner by using an amount of 1/N (wherein (1≦N<100, and N is an integer) of the total amount of the platinum-containing solution and the pH modifier.  
     
     
         20 . A method for manufacturing an electrode catalyst that comprises platinum particles on a support with a specific surface area of 1200 m 2 /g or more, wherein the platinum particles have a particle size of 3.5 nm or less by controlling the theoretical amount of Pt on the support to 60 wt % or more.