Lanthanum doped Bi₂O₃ (La-Bi₂O₃) photocatalysts were prepared by impregnation method. The doping quantity of lanthanum, crystalline phase structures and spectral properties of as-prepared photocatalysts were characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectrophotometry (UV-Vis) and photoluminescence spectroscopy (PL). The enhanced visible-light activity was tested by the photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP). Results of XRD show that appropriate amounts of lanthanum adulteration can effectively prevent the phase transformation of Bi₂O₃ from tetragonal to monoclinic. UV-Vis DRS results indicate an extension of light absorption into the visible region (higher than 550 nm). The doped lanthanum partially substitutes bismuth in the lattice of Bi₂O₃, which exists in the form of Bi—O—La chemical bond. And a new complex metal oxide compound (La_0.176Bi_0.824O_1.5) appears in the catalysts, which could inhibit the recombination between photoelectrons and holes, leading to enhanced photocatalytic quantum efficiency. Furthermore, it is found that Bi₂O₃ doped with lanthanum of 3% (in mole ratio) has the superior photocatalytic performance for 2,4-DCP.

Key words: bismuth oxide, lanthanum-doped, visible-light, photocatalytic oxidation, 2,4-dichlorophenol (2,4-DCP)