The photochemistry of oriented rutile surfaces has been examined using the photoreduction of Ag+ to Ag metal from an aqueous solution onto the TiO2 surfaces. The photochemical reaction rates and quantum yields of rutile films were found to be a function of the orientation of the rutile surface. The (100) and (110) rutile orientations have lower photoreduction rates than the (101), (111), and (001). This dependence of the photochemical reaction rates on film surface orientation is observed over a range of light intensities, illumination wavelengths, and film thicknesses. Atomic force microscopy has been used to characterize the morphologies of the film surfaces and the photoreduced Ag at these surfaces. Several properties of rutile, such as the surface morphology, surface chemistry, space charge phenomena, and charge transport, are discussed in relation to their possible contributions to the orientation dependence of the photochemistry on the rutile films.

Polished and annealed surfaces of randomly textured rutile polycrystals were used to photochemically reduce Ag + to Ag metal in an aqueous solution. By correlating the surface orientations of more than 100 individual crystallites with the amount of deposited Ag, we conclude that the most reactive orientations lie near the {101} plane. Most annealed rutile surfaces are microscopically faceted so that they locally expose planes that are not parallel to the crystallite's average surface. The observations reported here indicate that the anisotropy of rutile's photochemical properties derives from differences in the properties of specific surface planes rather than the bulk crystallite orientation.

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