Analytical Sciences

Characterization of Surface and Photooxidative Properties of Supported Metal Oxide Photocatalysts Using Solid-State NMR

Sarah PILKENTON, Weizong XU, and Daniel RAFTERY 

H. C. Brown Laboratory, Department of Chemistry, Purdue University, West Lafayette, IN 47907-1393, U.S.A.

In situ solid-state NMR (SSNMR) methodologies have been used to investigate the surface properties and photooxidative reactivities of a number of metal oxide photocatalysts. Adsorption of ethanol on single monolayers of TiO₂, SnO₂, V₂O₅, and WO₃ supported on porous Vycor glass results in the formation of hydrogen-bonded ethanol species and metal-bound ethoxide species. The chemical shift of the metal-bound ethoxide species varies with the metal oxide catalyst while the chemical shift of the hydrogen-bonded species is independent of the metal oxide. X-ray powder diffraction, UV-VIS spectroscopy, and SSNMR investigations of ethanol adsorption show that increasing the number 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, acetone, and 2-propanol also increases with increasing TiO₂ monolayer coverage.

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