Effect of Au supported TiO2 with dominant exposed {0 0 1} facets on the visible-light photocatalytic activity

Abstract

Novel visible-light-driven plasmonic photocatalyst Au/TiO2 nanosheets with a high percentage of exposed {001} facets were fabricated by hydrothermal treatment of tetrabutyl titanate and hydrofluoric acid, followed by the polyol reduction process (denoted by Au/TiO2-001). The prepared samples were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2-sorption, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectra. The variations of photoelectric response after depositing Au nanoparticles (NPs) on TiO2-001 nanosheets were investigated by the photoelectrochemical experiment. The results display that the Au NPs with average diameter of ca. 5nm were deposited on (001) facet of TiO2 nanosheets in the form of metallic state. The samples exhibited a strong absorption in the visible light region due to the surface plasmon resonance (SPR) effect of Au NPs. For the photocatalytic degradation of rhodamine B (RhB) in aqueous solution, the Au/TiO2-001 showed superior photocatalytic activities compared with bare TiO2-001 and other Au deposited photocatalysts, such as Au/P25 (Degussa TiO2), Au/anatase TiO2, and Au/rutile TiO2. The enhanced photocatalytic activities can be explained by its unique morphology, larger surface area, and smaller crystallite. Meanwhile, TiO2 dominated {001} facets with higher electron mobility and better adsorption of pollutant molecule may be another reason for the higher photocatalytic activity. In addition, the Au NPs are believed to play an essential role in enhancing the photoreactivity because they are able to generate photoelectrons and enhance the visible light absorption intensity. The effects of the Au content, the calcination temperature of TiO2-001, the supporter, and the reaction atmosphere on photocatalytic activities were investigated in detail. The decomposition mechanism of RhB over Au/TiO2-001 under visible light irradiation and the active species in the photocatalytic process had also been discussed. It is hoped that our work could render guided information for steering toward the design and application of noble metal/semiconductor nanocompositions with high visible-light photocatalytic activity.