Fig. 2. (a) Cyclic voltammogram of the rutile TiO2(110) electrode in 0.1 M HClO4 at a scan rate of 1 V s−1. (b) Level diagram at the TiO2 water interface in the EC-STM configuration. The light red and orange regions indicate the reduction potential of surface TiIV/TiIII states (U°) and the vertical ionization potential of the corresponding reduced TiIII state (IPR), respectively. The red and orange range solid bars show the potential ranges of the oxide sample and the STM tip adjusted to give high quality images. (c) Large area (150 × 150 nm2) of the EC-STM image of the rutile TiO2(110) in 0.1 M HClO4. EC-STM parameters are Esample = −0.38 V vs. SCE, Etip = 1.27 V vs. SCE, and Itunnel = 1 nA, respectively. (d) Magnified area (10 × 10 nm2) with atomic resolution of the white dashed square in (c). The inset shows a further magnified area of 3 × 5 nm2. (e) Top view of the atomistic model of the rutile TiO2(110) surface with a [11̄1] step. (f) Atomistic structure of the [11̄1] step. Ti and O atoms are coloured in grey and red, respectively.
