Ab Initio Study of Water Adsorption and Reactivity on the (211) Surface of Anatase TiO2 Ab INITIO STUDY of WATER ADSORPTION and ⋯ XU et al.

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 0.97 J/m2, close to that of the (001) surface, and the unsaturated fourfold-coordinated Ti4 atom is more reactive than the unsaturated fivefold-coordinated Ti5 atom. Accordingly, for water adsorption on the (211) surface, a dissociative form is favored on Ti4 sites, with a large adsorption energy ΔHH,OH∼1.28 eV, while a nondissociative molecular form is favored on Ti5 sites, with a smaller adsorption energy ΔHH2O∼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.