Dark and photoreactions of acetates on TiO2(1 1 0) single crystal surface

The surface reaction of acetates on TiO2(1 1 0) single crystal has been monitored in dark and under UV by XPS. XPS O(1s) data indicated that surface saturation is obtained at ≈0.5 monolayer coverage consistent with STM results [J. Chem. Phys., 106 (1997) 2924, Surf. Sci. 433–435 (1999) 322]. Annealing the surface results in a steady decrease of surface acetates that disappeared by ≈600 K. UV illumination at room temperature, and in the absence of diatomic oxygen in the gas phase, did not decrease the intensity of the XPS C(1s) and O(1s) signals attributed to surface acetates. On the other hand, UV illumination in presence of oxygen (≈10−7–10−6 Torr of diatomic oxygen) has resulted in a noticeable decrease of surface acetates. These combined results indicate that both the two-fold bridging oxygen and the three fold lattice oxygen atoms are not directly involved in the photooxidation reaction of acetates on TiO2(1 1 0) single crystal. The cross-section of the photodepletion of acetates was estimated equal to 0.6–0.8×10−17 cm2.