(88a) Synthesis of Visible Light-Sensitive TiO2 Coated Silica Beads by Cu(II) or Fe(III) Grafting

Visible light sensitive TiO₂ coated silica beads were prepared by grafting Cu(II) or Fe(III) ion onto TiO₂. In the experiment, the surface of silica beads (D=0.5µm) was coated by TiO₂ by applying direct hydrolysis reaction of Ti-tetraisopropoxide(TTIP) in ethanol solution. Scanning electron microscopy observation confirmed that TiO₂ was coated on the silica beads in the form of amorphous nano particles uniformly by this method. When the amount of supplied TTIP solution increased during coating process, the amount of coated TiO₂increased. After calcined at high temperature the amorphous TiO₂ nano particles changed into crystalline TiO₂and their diameter also increased to few ten~few hundred nm. When the coated amount increased, the ratio of rutile/anatase also varied even calcined at the same temperature.

To synthesize visible light-sensitive TiO₂ by Cu(II) or Fe(III) grafting, it is known that rutile phase TiO₂ shows better photocatalytic activity than in the case of using anatase phase TiO₂. Therefore, in this experiment, the TiO₂ coated beads (TCB) with higher rutile/anatase ratio was used for grafting. When Cu(II) or Fe(III) ion was grafted by the impregnation method to TCB, it showed visible light absorption (>400nm). The photocatalytic activity of the Cu(II) of Fe(III) grafted TCB were evaluated by the photocatalytic decomposition of acetic acid as a model substance under the visible light (410-530nm) irradiation using Xe lamp. The result showed that Cu(II) or Fe(III) grafted TCB demonstrated higher activity compared to the non grafted TCB. The result indicated that visible light sensitive TiO₂ coated silica beads were successfully prepared by this method.