Photocatalytic degradation of methylene blue with TiO2 by doping with rare earth ions (Y3+, La3+and Nd3+)

Rare earth ions (Y
³⁺
,La
³⁺
,Nd
³⁺
) doped TiO
₂
catalysts were prepared by the sol-gel method, and characterized by X-ray diffraction (XRD) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activities of doped TiO
₂
were evaluated with methylene blue degradation under UV light. The anatase to rutile phase transformation of doped TiO
₂
was significantly inhibited by rare earth ions doping, and the inhibitory effect was related to ion radius with a sequence of La
³⁺
> Y
³⁺
> Nd
³⁺
. The doped rare earth ions were in form of rare earth oxides, which adsorbed on TiO
₂
surface to efficiently separate charge carriers. Rare earth ion doping in TiO
₂
can extend light absorption properties to the visible region, which indicates the reduced band gap position of doped TiO
₂
. The content of doped rare earth ions was an important factor affecting photocatalytic activity. The optimum amount of rare earth doping is 0.1~0.15wt%, at which the photo-reactivities of doped TiO
₂
were about 20% higher than that of pure TiO
₂
.