Anisotropic photochemical reactivity of bulk TiO2 crystals

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.