Thesis (M.Eng.)--Chulalongkorn University, 2005

A series of cerium dioxide/titanium dioxide (CeO[subscript 2]/TiO[subscript 2]) photocatalysts were prepared via a sol-gel method and were calcined at 300 ํC for 2 hr. A mixed oxide consisted of TiO[subscript 2] as the major phase and CeO[subscript 2] as the dopant phase in the range of 0-10% mol. Properties of ceria-titania mixed oxides have been investigated using X-ray diffraction (XRD), nitrogen physisorption, inductively coupled plasma atomic emission spectroscopy, UV-Visible absorption spectroscopy, electron spin resonance, fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of CeO[subscript 2]/TiO[subscript 2] catalysts were evaluated for the degradation of ethylene under UV illumination. The experimental results demonstrated that the photocatalytic activities of CeO[subscript 2]/TiO[subscript 2] catalysts dramatically decreased with increasing ceria content. This decrease was dueto the smaller amount of Ti[superscript 3+] surface defects, smaller band-gap energy, and fewer hydroxyl groups on the catalyst surface. However, when alcohol (i.e., methanol and 2-propanol) was employed as a reactant, we obtained the highest photocatalytic acitivity for the oxidation of alcohol with the mixed oxide catalyst that contained. 0.5% mole of ceria. This result can be explained by different reaction pathways.