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

A series of Zn
²⁺
and Eu
³⁺
co-doped TiO
₂
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 Zn
²⁺
and Eu
³⁺
co-doped TiO
₂
samples exclusively consist of primary anatase crystallites, the co-doping can retard the grain growth of TiO
₂
and decrease the aggregation of TiO
₂
nanoparticles. Zn
²⁺
and Eu
³⁺
co-doping increased the visible-light absorption ability of TiO
₂
catalysts and a red shift appeared when compared to pure TiO
₂
. The photocatalytic activity of samples was evaluated by the photodegradation of methyl orange under natural light irradiation. Optimal doping amounts for Zn
²⁺
and Eu
³⁺
are 1.0% and 1.5% respectively, and two dopants of Zn
²⁺
and Eu
³⁺
in nanocrystalline TiO
₂
show a synergistic effect, which significantly increases the photocatalytic activity of TiO
₂
. The photocatalytic mechanisms of Zn
²⁺
and Eu
³⁺
co-doped TiO
₂
catalysts were tentatively discussed.