Process of depositing nanoparticles of a metal or of an alloy of said metal, said metal being chosen from the metals from columns VIIIB and IB of the Periodic Table, dispersed on a substrate by chemical vapour deposition (CVD), from one or more precursors, in which the deposition is carried out in the presence of a gas comprising more than 50 vol % of a reactive oxidizing gas.Substrate comprising at least one surface, dispersed on which are nanoparticles made of a metal or of an alloy of metals, for example made of silver or a silver alloy.Use of the substrate to catalyse a chemical reaction, for example an NO.sub.x elimination reaction.