The origin of photochemical anisotropy in SrTiO₃

Photochemical reactions that deposit insoluble products on catalytic surfaces have been used to probe the anisotropy of the reactivity of SrTiO₃ microcrystals. Both reduced and oxidized products are formed preferentially on {100} surfaces. It is proposed that the anisotropic photochemical reactivity can be explained by the electronic band structure. Because direct optical transitions for charge carriers having momentum vectors in the <100> direction overlap well with the spectral distribution of the absorbed photons, more photogenerated carriers are moving toward {100} surfaces than other surfaces and, as a result, {100} surfaces are more active. Knowledge of the electronic band structure and the spectral distribution of the light allows predictions to be made about the anisotropic reactivity of photocatalysts with other crystal structures.