Core-shell particles with catalytic activity

A method for the prepay of spherical core-shell particles, comprising the successive stops consisting of:

• (a) mixing a cobalt salt with (i) ammonium carbonate, bicarbonate or carbamate and (ii) ammonium hydroxide in water, so as to obtain an aqueous solution comprising a cobalt amine complex;
• (b) heating said aqueous solution to a temperature between 40 and 90° C., either before, while or after adding under agitation particles of alumina ha having a substantially spherical shape and a number average diameter of less than 30 nm measured by TEM, so as to disintegrate alumina aggregates into primary particles and precipitate cobalt carbonate unto the surface of the alumina primary particles and to obtain core-shell particles having a core of alumina and shell of cobalt carbonate;
• converting cobalt carbonate in the shell of said core-shell particles it to cobalt oxide.