Direct Visualization of Oxygen Reaction with Paired Hydroxyl on TiO₂(110) Surface at 78 K by Atomic Force Microscopy

The hydroxyl defects on rutile TiO₂ surface play an important role in surface chemical reactions and understanding the catalytic reactions due to its excess electrons. In this work, the reaction behavior of oxygen molecule with paired hydroxyl defects on a rutile TiO₂(110)-(1 × 1) surface was observed at 78 K with the atomic resolution by atomic force microscopy. The high reactivity of paired OH with O₂ is attributed to the asymmetric spatial distribution of its excess electrons, and the reaction sites occupy a high distribution of excess electrons. The effect of tip to the surface reactions is discussed, and atomic contrast of their reaction product 2OH_t is associated with the tip-sample distance. The present study is expected to provide some insights into catalytic reactions on oxide surface.