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

Rare earth ions (Y³⁺,La³⁺,Nd³⁺) doped TiO2 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 TiO2 were evaluated with methylene blue degradation under UV light. The anatase to rutile phase transformation of doped TiO2 was significantly inhibited by rare earth ions doping, and the inhibitory effect was related to ion radius with a sequence of La³⁺> Y³⁺> Nd³⁺. The doped rare earth ions were in form of rare earth oxides, which adsorbed on TiO2 surface to efficiently separate charge carriers. Rare earth ion doping in TiO2 can extend light absorption properties to the visible region, which indicates the reduced band gap position of doped TiO2. 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 TiO2 were about 20% higher than that of pure TiO2.