Ab Initio Study of Water Adsorption and Reactivity on the (211) Surface of Anatase

Abstract

The reactivity of the anatase TiO2 (211) surface is systematically studied by ab initio calculations of the surface energy and water-adsorption energy. We find that anatase (211) has a high surface energy of 0.97J/m2, close to that of the (001) surface, and the unsaturated fourfold-coordinated Ti 4 atom is more reactive than the unsaturated fivefold-coordinated Ti 5 atom. Accordingly, for water adsorption on the (211) surface, a dissociative form is favored on Ti 4 sites, with a large adsorption energy ΔHH,OH ∼ 1.28 eV, while a nondissociative molecular form is favored on Ti 5 sites, with a smaller adsorption energy Δ H H2O ∼ 0.78 eV. Such distinct surface properties lead to a mixed dissociative and molecular adsorption configuration when the coverage is increased from 1/3 to 1 monolayer. These results suggest that, similar to the (001) surface, the anatase (211) surface exhibits high reactivity and may be useful in catalytic and photocatalytic applications as well.