SiO2–Ag–SiO2–TiO2 multi-shell structures: plasmon enhanced photocatalysts with wide-spectral-response

Abstract

Tailorable synthesis of plasmon enhanced catalysts with high solar-light harvesting and energy-conversion efficiency has attracted wide interest due to its scientific and technological importance. In this paper, novel SiO₂–Ag–SiO₂–TiO₂ multi-shell photocatalysts with wide-spectral-response were systematically designed and controllably synthesized, where the SiO₂ spheres were used as the cores, and the SiO₂ interlayers coated on the Ag nanoparticle (NP) shells were used to separate the Ag from the TiO₂ shell. The structures of the SiO₂–Ag–SiO₂–TiO₂ multi-shell photocatalysts can be tailored by changing the thickness of SiO₂ interlayers from 1 to 2, 5, 8, 12, and 20 nm, while the anatase N-doped TiO₂ shells with visible light response are maintained at a thickness of 20 nm. The photocatalytic activity tests show that the enhanced photocatalytic efficiency under both ultraviolet (UV) and visible light irradiation is related to the existence of Ag NP shells and the thickness of SiO₂ interlayers. The complicated coupling mechanisms between TiO₂ and a plasmon are systematically discussed, and a clear physical picture for the complicated coupling processes is presented. The main reasons for the enhancement of the photocatalytic activity of the SiO₂–Ag–SiO₂–TiO₂ multi-shell structures are the localized surface plasmon resonance (LSPR) effect and scattering effect induced by Ag NPs.