Thesis (D.Eng)--Chulalongkorn University, 2007

In this work, pure anatase nano-TiO[subscript 2] with various crystallite sizes and metal-doped TiO[subscript 2] were synthesized by solvothermal method. The catalysts were subjected to a rapid quenching in various media such as H[subscript 2] O, 30%wt H[subscript 2]O[subscript 2], air, and liquid N[subscript 2]as a post-synthesis treatment. In order to identify the characteristics, all catalysts were characterized using N[subscript 2] physisorption, XRD, SEM, CO[subscript 2] -TPD, ESR, and XPS. The photocatalytic activities of TiO[subscript 2] catalysts were evaluated for the degradation of ethylene under UV illumination. It was found that photocatalytic activity of the nanosized TiO[subscript 2] quenched in different media is evidently different. It is likely that quenching process can modify surface properties of the TiO[subscript 2] samples i.e., enhancing the amount of surface defects (Ti[superscript 3+]) so that higher photocatalytic activity was obtained. The effect of quenching was more pronounced on the smaller crystallite size TiO[subscript 2] than on the larger ones. In addition, the selection of a suitable second metal doping can enhance photocatalytic activity of the TiO[subscript 2] . Moreover, the quenching processes tended to have positive effect on activity for CO hydrogenation reaction.