SiO₂-Ag-SiO₂ core/shell structure with a high density of Ag nanoparticles for CO oxidation catalysis

SiO₂-Ag-SiO₂, a sandwiched core/shell structure with a layer of Ag nanoparticles (∼4 nm) encapsulated between a shallow SiO₂ surface layer and a SiO₂ submicrosphere substrate (∼200 nm), has been synthesized from [Formula: see text] and SiO₂ spheres by a facile one-pot hydrothermal method. The composite is proposed to result from the dynamic balance between the [Formula: see text] reduction and the dissolution-redeposition of SiO₂ in mild basic media. The synthetic mechanism and the roles of the reaction time, temperature, and the amount of ammonia in the formation of this unique structure are investigated and discussed. The composite structure shows superior catalytic performance in CO oxidation to the control Ag/SiO₂ structure prepared by impregnation. Pre-treatment by O₂ at 600 °C significantly improves the catalytic performance of the composite structure and preserves the nanocomposite structure well.