HIGHLY ACTIVE AND STABLE CATALYST PARTICLES, ELECTRODE CATALYST OBTAINED USING SAME, AND PROCESS FOR PRODUCING SAME
There have been a phenomenon in which during the operation of a fuel cell, an alloy component dissolves away during use, resulting in a decrease in activity and an increase in particle diameter. A purpose of the present invention is to provide catalyst particles which comprise: alloy particles that contain a noble metal and have a uniform particle diameter of the order of nanometer
and a Pt skin layer which is composed of one to five monatomic layers and with which the surface of the alloy particles has been covered. The other purpose is to provide: an electrode catalyst which comprises a support loaded with the catalyst particles disposed thereon in a highly dispersed state
and a process for producing the electrode catalyst. With the catalyst particles, it is possible to reduce the amount of a noble metal to be used, and an improvement in activity as compared with Pt alone can be attained due to an electronic action between the inner metals and the surface Pt skin layer. By entirely covering the inner alloy particles with the Pt layer, the catalyst particles can be made to have high corrosion resistance. When the catalyst particles are produced by a production process in which nanocapsules are used, the catalyst particles are rendered excellent in terms of activity and durability because the active-metal particles have a small diameter and the alloy retains a constant composition.