Abstract:

Rare earth (RE) and B co-doped (RE-B) nano-TiO₂ photocatalysts were prepared through a sol-gel method using tetrabutyl titanate, lanthanum nitrate, cerous nitrate, and boric acid. The phase constitution, surface morphology, surface elemental compositions, light responsivity, the band gap and the composite of the electronic hole of catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and ultraviolet-visible spectroscopy (UV-Vis). The results show that all the doped products were anatase TiO₂, and RE-B doping generates large lattice distortion and had the function of refining the grain, with the grain size decreasing from 27 nm (TiO₂) to 10 nm (La-B-TiO₂). The doped TiO₂ was flake structure and piled up irregularly. Co-doping enhanced the absorption in the visible region and narrowed the band gap simultaneously. The absorption edge of La-B-TiO₂ moved from 405 nm to 466 nm, and the band gap decreased 0.4 eV correspondingly. XPS results show that the doping elements have effectively doped into the titanium dioxide, and PL spectra show that the co-doping can effectively extend the life of the carrier. The photocatalytic activities of the samples were estimated by degrading methylene blue (MB) under visible and ultraviolet light irradiation for 2 h, and show much improved catalytic activity compared to un-doped TiO₂. The degradation rate of MB using La/B-TiO₂ was 80.67% under ultraviolet light, which is about 2.7 times that of un-doped TiO₂, and 74.78 % under visible light.

Key words: Sol-gel method, RE-B co-doping, TiO₂, MB, Photo-degradation