In situ synthesis of TiO2/SnOx–Au ternary heterostructures effectively promoting visible-light photocatalysis

Abstract

TiO₂/SnO_x–Au ternary heterostructures were successfully fabricated via a simple in situ reduction of AuCl₄⁻ on TiO₂ surfaces pre-modified with Sn²⁺. The samples were characterized by XRD, TEM, XPS, N₂ physical absorption and UV-vis diffuse reflectance spectra. Photocatalytic activity toward degradation of methylene blue (MB) aqueous solution under visible light irradiation was investigated. The results suggested that the highly dispersive and ultrafine Au nanoparticles (NPs) covered with SnO_x were deposited onto the surface of TiO₂. The heterostructures significantly enhanced the photocatalytic activity compared with the traditional TiO₂/Au sample prepared by the impregnation method and also enhanced the activity more than the binary TiO₂/SnO_x sample. Moreover, the size of the Au NPs could be well controlled by simply tuning the dosage of HAuCl₄, and the optimized catalytic activity of the ternary heterostructures was obtained when the dosage of Au was 1% and the Au particle size was ∼2.65 nm. The enhancement of photocatalytic performance could be attributed to the surface plasmon resonance effect of the Au NPs and the electron-sink function of the SnO_x, which improve the optical absorption properties as well as photoinduced charge carrier separation, synergistically facilitating the photocatalysis.