Method for producing fine catalyst particle and fuel cell comprising fine catalyst particle produced by the production method

A method for producing a fine catalyst particle comprising a palladium-containing particle and a platinum outermost layer covering the palladium-containing particle,

• wherein a first composite body containing palladium and platinum is formed by mixing the palladium-containing particle with a first solution in which a platinum compound is dissolved, and, as a result of bringing the palladium-containing particle into direct contact with the first solution, then covering at least part of a surface of the palladium-containing particle with platinum;
• wherein a second composite body containing palladium, platinum and copper is formed by mixing the first composite body with a second solution in which a copper compound is dissolved, and then covering at least part of a surface of the first composite body with copper using copper underpotential deposition;
• wherein the copper in the second composite body is substituted with platinum derived from a third solution in which a platinum compound is dissolved, by mixing the second composite body with the third solution;
• and
• wherein an amount of platinum atoms contained in the first solution is 70 atm % or less, when a minimum amount of platinum atoms required to cover the palladium-containing particle with a monatomic layer of platinum is 100 atm %.

A method for producing a fine catalyst particle comprising a palladium-containing particle and a platinum outermost layer covering the palladium-containing particle,

• wherein a composite body A containing palladium and copper is formed by mixing the palladium-containing particle with a second solution in which a copper compound is dissolved, and then covering at least part of a surface of the palladium-containing particle with copper using copper underpotential deposition;
• wherein a composite body B containing palladium and platinum is formed by mixing the composite body A with a third solution in which a platinum compound is dissolved, and then substituting the copper in the composite body A with the platinum derived from the third solution;
• wherein at least part of a surface of the composite body B is covered with platinum by mixing the composite body B with, in place of the third solution, a first solution in which a platinum compound is dissolved, and, as a result, bringing the composite body B into direct contact with the first solution;
• and
• wherein an amount of platinum atoms contained in the first solution is 70 atm % or less, when a minimum amount of platinum atoms required to cover the palladium-containing particle with a monatomic layer of platinum is 100 atm %.