Comparative study on sandwich-structured SiO2@Ag@SnO2 and inverse SiO2@SnO2@Ag: key roles of shell ordering and interfacial contact in modulating the photocatalytic properties

Abstract

Sandwich-structured SiO₂@Ag@SnO₂ and inverse SiO₂@SnO₂@Ag using SiO₂ spheres as cores have been systematically synthesized through hydrothermal treatment. The crystal structure, morphology, size, composition and specific surface area of products were investigated by XRD, SEM, TEM (HRTEM), XPS, UV-vis and N₂ adsorption–desorption instruments. It was found that both Ag nanoparticles and SnO₂ layers were successfully decorated or coated on the surface of the matrix. The investigation of photocatalytic properties indicated that the SiO₂@Ag@SnO₂ heterostructure possessed an excellent photocatalytic ability superior to the SiO₂@Ag, SiO₂@SnO₂ and even the inverse sample SiO₂@SnO₂@Ag, for the degradation of Rhodamine B (RhB) driven by UV light. The results indicated that Ag nanoparticles acted as the trapping centers for photo-induced electrons, and thus promoted the separation of photo-induced electron–hole pairs and charge migration. The enhanced photocatalytic ability of the heterostructure SiO₂@Ag@SnO₂ compared to the inverse sample SiO₂@SnO₂@Ag was possibly due to the larger exposed surface area under UV light irradiation, larger contact interfacial area and larger specific surface area of SiO₂@Ag@SnO₂ than SiO₂@SnO₂@Ag. Furthermore, the photocatalyst SiO₂@Ag@SnO₂ displayed benign recyclability in that its photocatalytic activity was still preserved after 5 cycles.