Synthesis and characterization of Ag@ETS-10 core-shell heterostructured photocatalyst for visible light photocatalysis

Surface modification of Engelhard titanosilicate (ETS-10) with silver (Ag) was carried out in efforts to promote the photocatalytic activity of ETS-10 towards the degradation of methylene blue (MB) under visible light irradiation. The core-shell heterostructure encapsulates the Ag nanoparticles, which would otherwise dislodge from the surface of ETS-10. The Ag@ETS-10 core-shell heterostructured photocatalyst was prepared by the photodeposition of Ag nanoparticles onto ETS-10 crystals to form the Ag-ETS-10 core, followed by secondary growth of ETS-10 shell using the Ag-ETS-10 as seeds. Ag@ETS-10 showed absorption in the visible light region, as well as a red shift in the UV region, compared to the unmodified ETS-10. The extent of shell growth depended on the seeding level. Increasing the seeding level from 1 wt.% to 50 wt.% resulted in a decreased mode of the particle size distribution of the products, and thus a decreased shell thickness. The Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼0.1 μm shell) showed higher photocatalytic activity in the photodegradation of MB under visible light irradiation (k = 0.0159 min-1) than the unmodified ETS-10 sample (k = 0.007 min-1). However, the Ag@ETS-10 photocatalyst grown using 1 wt. % seeding levels (i.e., ∼ 0.8 μm shell) showed lower photocatalytic activity compared to the Ag@ETS-10 photocatalyst grown using 50 wt.% seeding level (i.e., ∼ 0.1 μm shell). This was attributed to the suppression of the plasmon resonance peak when a thicker ETS-10 shell was grown around the Ag-ETS-10 core.