Visible-light excitated photocatalytic activity of rare earth metal-ion-doped titania

The rare earth ion Ce⁴⁺ doped Ti0₂ was prepared by sol-gel method. The average particle sizes are about 10 nm for sol phase and 55 nm for polycryslalline phase. The photocatalytic activities to degrade Reactive Brilliant Red Dye X-3B were investigated. The result reveals that the spectrum response of Ce⁴⁺-Ti0₂ extended to visible region from the UV region(λ<387 nm) of pure Ti0₂. Amorphous phase Ce⁴⁺-Ti0₂ sol with an electron scavenger (1.0% atom fraction Ce⁴⁺ ion doping amount) shows the capability of the photocatalytic degradation of the dye X-3B as well as the nanocrystallite Ce⁴⁺-Ti0₂ with an interband trap site. Despite of the difference in the morphology of Ce⁴⁺-Ti0₂ photocatalyst, there is no apparent difference in respect of the decoloring effects. Whereas, polycrystalline phase Ce⁴⁺-Ti0₂ exhibits strong photomineralization power in comparison with the amorphous phase. The photocatalytic oxidation mechanisms of the dye molecule mainly involved in the self-photo-sensitization photolysis process by the first excited singlet oxygen (¹O₂) and photocatalysis process by hydroxyl radicals (·OH) under visible light irradiation.