Photocatalytic Activities of Tin(IV) Oxide Surface-Modified Titanium(IV) Dioxide Show a Strong Sensitivity to the TiO 2 Crystal Form

Surface modification of rutile TiO 2 with extremely small SnO 2 clusters gives rise to a great increase in its UV light activity for degradation of model organic water pollutants, while the effect is much smaller for anatase TiO 2 . This crystal form sensitivity is rationalized in terms of the difference in the electronic modification of TiO 2 through the interfacial Sn–O–Ti bonds. The increase in the density of states near the conduction band minimum of rutile by hybridization with the SnO 2 cluster levels intensifies the light absorption, but this is not seen with modified anatase. The electronic transition from the valence band to the conduction band causes the bulk-to-surface interfacial electron transfer to enhance charge separation. Further, electrons relaxed to the conduction minimum are smoothly transferred to O 2 due to the action of the SnO 2 species as an electron transfer promoter.