Role of steps in the dissociative adsorption of water on rutile TiO2(110)

The water-TiO(2) interaction is of paramount importance for many processes occurring on TiO(2), and the rutile TiO(2)(110)-(1×1) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for water dissociation on rutile TiO(2)(110)-(1 × 1), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water dissociation channel exists on the surfaces of vacuum-annealed TiO(2)(110) crystals that is associated with the ⟨111⟩ step edges. This second water dissociation channel can be suppressed by blocking of the ⟨111⟩ step edges using ethanol.