| abstract |
In the present invention, the particle size is 3 nm or less, and the proportion of the metal binding state is 40% or more, which is measured by using an X-ray photoelectron analyzer and is attributed by waveform separation of the bond energy peak inherent to the metal. It is a metal catalyst containing certain metal fine particles. As the metal fine particles, platinum fine particles are preferable. The metal fine particles are reduced in the form of fine particles on the surface of the carrier particles by reducing the metal ions that are the basis of the metal fine particles by the action of the reducing agent in the liquid phase reaction system in which the carrier particles are dispersed. It is preferable to be supported on the surface of the carrier particles by precipitation. Further, the metal fine particles are reduced after precipitation to lower the oxidation state, whereby the ratio of the metal bonded state is adjusted to the above range. |