Comparative study of lanthanide oxide doped titanium dioxide photocatalysts prepared by coprecipitation and sol-gel process

Lanthanide-cloped TiO2 photocatalysts were prepared by coprecipitation and sol-gel methods and Rhodamine B was used to evaluate their photocatalytic activity. Some catalysts were characterized by XRD, X-ray photoelectron spectroscopy, N-2 adsorption-desorption and S.E.M. measurements to study the differences in physical and chemical properties. The catalysts prepared by coprecipitation exhibited a higher photocatalytic activity than those prepared by the usual sol-gel process. Both photocatalysts have a similar crystal composition, but the coprecipitation catalysts have a macro/mesoporous structure and more regular anatase phase with bigger crystallites. This could explain the difference in their photocatalytic activity. Both catalysts have a similar surface chemical state, i.e., [O]/[Ti] approximate to 2.02, the dominant substance is TiO2 along with a trace amount of lanthanide oxides, but there is some carbon residue on the surface of the sol-gel prepared samples. This may explain their lower photocatalytic activity. The morphology of the primary particles and catalyst agglomerates of the catalyst was affected by doping processes. (C) 2008 Published by Elsevier B.V.