Reactivity of anatase (001) surface from first-principles many-body Green's function theory.

The anatase (001) surface has attracted a lot of interest in surface science due to its excellent performance. However, its reactivity is under debate since it can undergo a (1 × 4) reconstruction. Herein, we applied the many-body Green's function theory to investigate the electronic properties and excitons as well as the water adsorption behavior of the (1 × 4) unreconstructed anatase (001) surface and two reconstructed patterns, namely ADM and AOM. Our results revealed that the high reactivity of the (001) surface is probably not relevant to the reconstructed shape. The unreconstructed (001) surface and reconstructed ADM surface were very reactive for dissociating H2O molecules among three surfaces, but the lower-energy singlet exciton for ADM was completely confined within the inner atomic layers in TiO2, which is unfavorable for hole transfer to the reactant on the surface. Also, the required photon energy for initiating photochemical reactions on the reconstructed ADM surface should be higher than for the unreconstructed (001) surface, implying it is more difficult for the reaction to happen on the former surface. The unreconstructed (001) surface exhibited the highest reactivity due to the smaller optical absorption edge and the photoholes distributed on surface sites.