Reactions of tetraethoxysilane vapor on polycrystalline titanium dioxide

Article abstract of DOI:10.1021/j100002a042

The reactions of tetraethoxysilane (TEOS) vapor on dehydroxylated and water predosed polycrystalline TiO₂ were studied by Fourier transform infrared spectroscopy (FTIR) and temperature-programmed desorption (TPD). Exposure at 300 K leads to dissociative adsorption producing a monoethoxysilyl ligand and surface ethoxide species. The ethoxide ligands react and desorb in the range 450-650 K as gas phase ethanol and ethylene, while the monoethoxysilyl ligand decomposes at approximately 650 K to gas phase ethanol and ethylene and surface bound SiO₂. Dissociation of TEOS on TiO₂ is not affected by water predose; although, a greater amount of ethanol is produced in the gas phase at 550-650 K, and the SiO₂ which is formed exhibits vibrational features characteristic of a hydroxylated species. TEOS chemistry on TiO₂ was compared to the adsorption and reaction of ethanol on the same surface. Adsorption of ethanol at 300 K yielded surface ethoxide species which desorbed in two states as the parent alcohol and ethylene; desorption was also centered at 450 and 650 K. These results complement and supplement our previous study of TEOS on a TiO₂(110) single crystal surface.