Preparation of Nanostructured TiO 2 Powders with Additions of Various Metal–Chlorides for Efficient Photocatalyst

Preparation of nanostructured TiO 2 powders for efficient photocatalyst was investigated through a direct crystallization from aqueous TiOCl 2 solutions containing various metal–chlorides. The TiO 2 powders without any additives and those added with Ni 2+ , Fe 3+ and Nb 5+ ions, respectively, which has a similar cationic radius to Ti 4+ , were mainly crystallized to rutile phase, whereas those added with Al 3+ and Zr 4+ ions, which have a quite different positive ionic radius, were mainly crystallized to anatase phase. On the other hand, the secondary particles in the TiO 2 powder consisted of acicular and spherical primary particles corresponding to rutile and anatase phases, respectively. From these results, it seems that the cationic radius of the additives could affect phase formation as well as morphology of TiO 2 precipitates. Among the TiO 2 powders prepared, Ni 2+ doped powder, showing mainly rutile phase, had excellent photocatalytic ability in decomposition of 4-chlorophenol.