The synthesis and characterization of ytterbium-doped TiO2 hollow spheres with enhanced visible-light photocatalytic activity

Abstract

Using (C16H36O4)Ti and Yb(NO3)3 solutions as raw materials, Yb-doped TiO2 hollow spheres (Yb-TiO2HS) with different doping ratios (Yb:Ti = 0.5%, 1%, and 1.5%) were successfully fabricated via a sol-gel template method with melamine-formaldehyde polymer microspheres (MF) as templates. The Yb-TiO2HS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, specific surface area and porosity analysis, ultraviolet-visible-light diffused reflection spectroscopy (UV-DRS), and luminescence spectroscopy. The Yb-TiO2HS can absorb visible-light and exhibit a lower recombination of electrons (e-) and holes (h+) when compared with commercial P25 TiO2 powder (P25). The photocatalytic activities of the prepared samples were estimated by the degradation process of methyl orange (MO) dye under irradiation with visible-light (λ > 450 nm). With H2O2 and Yb-TiO2HS (Yb:Ti = 1%) as the promoter and photocatalyst, respectively, the degradation ratio of MO achieved a maximum value (89%) after irradiation for 5 h. While excessive Yb doping resulted in a negative effect on the photocatalysis, an appropriate doping ratio restrained the recombination of electron-hole pairs and extended the light absorption range, thus enhancing the ability of the visible-light photocatalysis. Moreover, the addition of H2O2 improved the dye adsorptive activity of TiO2HS, which further enhanced the photocatalytic effect.