Method for producing platinum nanoparticles

A method for producing platinum nanoparticles, comprising:

• a preparing step of preparing a carbon support, a dispersion medium, a platinum compound having platinum, an adsorbent having at least one of elements of alkali metals and alkali earth metals, which is adsorbable on surfaces of said carbon support, and a capping reagent capable of capping specific areas of crystals of platinum;
• a first mixture liquid forming step of forming a mixture liquid in which said dispersion medium, said carbon support, said platinum compound and said adsorbent are mixed with each other, wherein in said first mixture liquid forming step, said first mixture liquid is formed by mixing said platinum compound in said dispersion liquid in which said carbon support has been dispersed, and thereafter by mixing said adsorbent in said dispersion medium;
• wherein, optionally, one part of said adsorbent is mixed in said dispersion medium in which said carbon support has been dispersed, prior to said mixing of said platinum compound in said dispersion liquid;
• and
• a second mixture liquid forming step of forming a second mixture liquid in which said first mixture liquid and said capping reagent are mixed with each other;
• and
• a reducing step, wherein said second mixture liquid is reduced with a reducing agent to form platinum nanoparticles on said carbon support, wherein said method minimizes aggregation of the platinum nanoparticles formed on said carbon support.