Analysis and Comparison of the Photodecomposition Reaction of Methanol on CeO2 Impregnated TiO2 Surfaces Versus Bare TiO2 Surfaces
Date of Award
Master of Science in Chemical Sciences (MSCB)
Mark B. Mitchell
Michael Van Dyke
Titanium dioxide (TiO2) has been well-studied primarily due to its unique photocatalytic activity. Different preparation techniques have been developed to increase its photocatalytic activity by various means, including simply increasing the surface area, changing the makeup of the framework, and modifying the surface with a dopant. This study focuses on the effect cerium oxide (CeO2) has on the photocatalytic activity of TiO2 by depositing CeO2 on the TiO2 surface. Methanol is used as a probe reactant for these experiments due to its wide use in heterogeneous catalysis research and the limited products that can form. Three-dimensional CeO2 crystallites form on the 1 and 2 monolayer CeO2-TiO2 samples while crystals are not observed for the 0.5 or 0.25 monolayer samples. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) was used to characterize the surface chemistry occurring on these samples while a flow reactor was used to characterize the reaction products using a long path gas cell in a Fourier transform infrared spectrometer (FTIR). Except for the 1 monolayer sample, CeO2 seems to increase the reaction and decomposition of organic compounds, especially chemisorbed methoxy groups, on the surface. The CeO2 modified samples appear to adsorb molecular methanol less strongly than TiO2. Upon UV irradiation, the CeO2 modified samples desorb methoxy as methanol more so than TiO2. All samples consistently produce carbon dioxide, water, formaldehyde, dimethyl ether, and methanol in the presence of ultraviolet light and oxygen.