Characterization of surface and photooxidative properties of supported metal oxide photocatalysts using solid-state NMR

In situ solid-state NMR (SSNMR) methodologies have been used to investigate the surface properties and photooxidative reactivities of a number of meta l oxide photocatalysts. Adsorption of ethanol on single monolayers of TiO2, SnO2, V2O5, and WO3 supported on porous Vycor glass results in the formati on of hydrogen-bonded ethanol species and metal-bound ethoxide species. The chemical shift of the metal-bound ethoxide species varies with the metal o xide catalyst while the chemical shift of the hydrogen-bonded species is in dependent of the metal oxide. X-ray powder diffraction, UV-VIS spectroscopy , and SSNMR investigations of ethanol adsorption show that increasing the n umber of monolayers of TiO2 on the Vycor surface changes the morphology of the catalyst from amorphous at a single monolayer coverage to anatase at a four monolayer coverage. The rate of photocatalytic oxidation of ethanol, a cetone, and 2-propanol also increases with increasing TiO2 monolayer covera ge.