Solid-state NMR studies of the adsorption and photooxidation of ethanol on mixed TiO2-SnO2 photocatalysts

In situ solid-state NMR methodologies have been used to investigate the photocatalytic oxidation of ethanol (CH3CH2OH) over a series of SnO2-based photocatalysts. The adsorption of ethanol on commercially available SnO2 powder was studied using both cross-polarization C-13 NMR and REDOR experiments, and showed the formation of two surface ethanol species, hydrogen-bonded ethanol at surface hydroxyl groups and ethanol chemisorbed to the SnO2 surface (Sn-OCH2CH3). C-13 NMR of the adsorbed ethanol was used to characterize the surface of monolayer SnO2-TiO2 coupled photocatalysts supported on porous Vycor glass. In situ solid-state NMR studies showed that the photooxidation of ethanol over the monolayer photocatalysts was slower than that over a supported TiO2 monolayer photocatalyst due to the build-up of reaction intermediates such as acetic acid on the catalyst surface. Sn-119 NMR experiments characterized the tin species on the porous Vycor glass support. (C) 2003 Elsevier Inc. All rights reserved.