Remarkable synergistic effect between {001} facets and surface F ions promoting hole migration on anatase TiO2

Abstract

Controllable synthesis and surface modification of TiO2 crystals with specific exposed facets using fluoride as a shape directing agent have drawn a great deal of attention in the photocatalytic field. Both the exposed facets and surface F ions are known to have a great influence on the photocatalytic performance of TiO2 crystals, while these two factors are usually considered and discussed separately. Here, we investigated the influence of surface F ions on the carrier migration when the surface F ions are present on anatase TiO2 crystals with predominant {001} or {101} facets by using the H2O photo-oxidation and NH3 photo-oxidation as the probe reactions. We observed a remarkable synergistic effect between {001} facets and surface F ions on the photogenerated hole migration. The {001} facets provide hole-trapping sites and the electrostatic effect of surface F anions attract and accelerate the holes migration to {001} facets, which synergistically promote the electron-hole pair separation and thus significantly enhance the photo-oxidation activity. However, no synergistic effect was detected between {101} facets and the surface F ions. This finding provides a new insight into the photogenerated charge migration on fluorinated TiO2 with specific exposed facets.