Electrode catalyst for fuel cell, method for producing the same, and polymer electrolyte fuel cell using the same

Abstract

An electrode catalyst for a fuel cell consists principally of a carbon support, and a platinum catalyst or a platinum-alloy catalyst supported on the carbon support. In the electrode catalyst, at least 0.7 mmol of an acid per gram of the electrode catalyst is present on the carbon support.

1 . An electrode catalyst for a fuel cell, comprising:
 a carbon support;   a catalyst supported on the carbon support wherein the catalyst is one of platinum and a platinum-alloy; and   one of at least 0.7 mmol of an acid per gram of the electrode catalyst when the catalyst is a platinum-alloy and at least 1.0 mmol of an acid per gram of the electrode catalyst when the catalyst is platinum, wherein said acid being present on the carbon support.   
     
     
         2 . The electrode catalyst according to  claim 1 , wherein the platinum-alloy catalyst comprises an alloy of platinum and at least one metal selected from ruthenium, molybdenum, osmium, cobalt, rhodium, iridium, iron, nickel, titanium, tungsten, palladium, rhenium, chromium, manganese, niobium, and tantalum. 
     
     
         3 . The electrode catalyst according to  claim 1 , wherein the carbon support on which the acid is present and the catalyst is supported is hydrophilic. 
     
     
         4 . (canceled) 
     
     
         5 . The electrode catalyst according to  claim 1 , wherein the acid is present on the carbon support in an amount equal to or greater than 1.31 mmol per gram of the electrode catalyst, when the catalyst is a platinum-alloy. 
     
     
         6 . A method for producing an electrode catalyst for a fuel cell according to  claim 1 , comprising:
 supporting the catalyst on the carbon support; and   treating the carbon support carrying the catalyst with an acid, so that one of at least 0.7 mmol of the acid per gram of the electrode catalyst when the catalyst is a platinum-alloy and at least 1.0 mmol of an acid per gram of the electrode catalyst when the catalyst is platinum is present on the carbon support treated with the acid.   
     
     
         7 . The method according to  claim 6 , wherein, after the carbon support carrying the catalyst is treated with the acid, the carbon support carrying the catalyst is cleaned. 
     
     
         8 . The method according to  claim 6 , wherein the platinum-alloy catalyst comprises an alloy of platinum and at least one metal selected from ruthenium, molybdenum, osmium, cobalt, rhodium, iridium, iron, nickel, titanium, tungsten, palladium, rhenium, chromium, manganese, niobium, and tantalum. 
     
     
         9 . The method according to  claim 6 , wherein the carbon support on which the acid is present and the catalyst is supported is hydrophilic. 
     
     
         10 . (canceled) 
     
     
         11 . The method according to  claim 6 , wherein the acid is present on the carbon support in an amount equal to or greater than 1.31 mmol per gram of the electrode catalyst, when the catalyst is a platinum-alloy. 
     
     
         12 . The method according to  claim 6 , wherein the acid with which the carbon support carrying the catalyst is treated is nitric acid. 
     
     
         13 . The method according to  claim 6 , wherein the acid amount in the catalyst will be determined in that 0.5 g of the catalyst are added to 20 ml of 0.1 N sodium hydroxide which is then ultrasonically stirred for 20 min, the resulting liquid is subjected to filtration, 0.05 ml of Methyl Orange as an indicator is added to 5 ml of the filtrate while stirring, and titration is conducted with 0.05N hydrochloric acid. 
     
     
         14 . A polymer electrolyte fuel cell comprising the electrode catalyst according to  claim 1 .