Highly Efficient Water Dissociation on Anatase TiO2(101)

Photoinduced water dissociation on anatase-TiO2(101) has been investigated using a laser surface photolysis technique, in combination with temperature programmed desorption and time-of-flight methods. Gaseous OH radicals have been clearly detected by the time-of-flight method during laser irradiation. Further result reveals that the water dissociation reaction occurs most likely via transferring a H atom to a two coordinated oxygen site nearby and ejecting an OH radical to the gas phase. As the water coverage increases, the yield of the water dissociation reaction is also enhanced, whereas the dissociation probability of water is nearly the same at different water coverages. In comparison with water dissociation on rutile-TiO2(110) where the dissociation probability of water is largely inhibited by the strong hydrogen bonds at high water coverage, the reaction on anatase-TiO2(101) is considerably more efficient at high water coverage, which is most likely due to the much weaker interaction between water molecules on the surface. This provides an important clue that strong hydrogen bond interaction should be avoided on a good photocatalyst for water dissociation.