Core-shell particles with catalytic activity

Core-shell particles obtained according to a method comprising:

• (a) preparing an aqueous solution comprising a ferric salt, at a temperature of less than 50° C.;
• (b) adding at least one base to said aqueous solution, so as to obtain a suspension of iron oxide particles having a pH value of from 10 to 14;
• (c) washing the suspension;
• (d) adding a strong acid to the washed suspension to peptize the washed suspension;
• (e) reacting at least one base with said peptized suspension, until the pH reaches a value from 10 to 14, at a temperature of from 50 to 95° C.;
• (f) adding a cobalt salt to the heated suspension in order to obtain spherical particles having a core of iron oxide and a shell comprising cobalt oxide, wherein the spherical particles comprise a core of iron oxide and a shell of cobalt oxide, characterized in that the core-shell particles are spherical with a number average diameter, as measured by TEM, of between 1 and 20 nm.