Effects of Yb³⁺-doping on phase transformation and photocatalytic activities of TiO₂ nano-powders

Yb³⁺-doped TiO₂ composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti (OC₄H₉)₄ and Yb(NO₃)₃ as precursors. The effects of the amount of Yb³⁺ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb₂O₃ to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO₂. The results indicate that Yb³⁺-doping can enhance the photocatalytic activity of TiO₂ nano-powders as compared with pure TiO₂. 0.125% (mass fraction) Yb³⁺ doped TiO₂ nano-powders calcined at 600°C for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO₂ nano-powders.