Effects of Zn²+ and Eu³+ Co-Doping on Photocatalytic Activity of TiO2

A series of Zn²⁺ and Eu³⁺ co-doped TiO₂ catalysts were prepared by a modified sol-gel method. The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy(TEM) and ultraviolet-visible diffuse reflection spectroscopy(UV-vis DRS). Characteristic results clearly show that all of Zn²⁺ and Eu³⁺ co-doped TiO₂ samples exclusively consist of primary anatase crystallites, the co-doping can retard the grain growth of TiO₂ and decrease the aggregation of TiO₂ nanoparticles. Zn²⁺ and Eu³⁺ co-doping increased the visible-light absorption ability of TiO₂ catalysts and a red shift appeared when compared to pure TiO₂. The photocatalytic activity of samples was evaluated by the photodegradation of methyl orange under natural light irradiation. Optimal doping amounts for Zn²⁺ and Eu³⁺ are 1.0% and 1.5% respectively, and two dopants of Zn²⁺ and Eu³⁺ in nanocrystalline TiO₂ show a synergistic effect, which significantly increases the photocatalytic activity of TiO₂. The photocatalytic mechanisms of Zn²⁺ and Eu³⁺ co-doped TiO₂ catalysts were tentatively discussed.