The selective adsorption and kinetic behaviour of molecules on TiO2(110) observed by STM and NC-AFM

In the present paper we report a kinetic aspect of molecules on terraces and steps of a TiO2(110)-(1x1) surface as observed by scanning probe microscopy, which may be relevant to oxide catalysis. When the TiO2 surface, heated at 400-450 K, was exposed to a formic acid ambient of 1-2x10(-6) Pa, small particles were formed on terraces. Post-reaction STM observation revealed that the particle formation was strongly suppressed in the vicinity of single-atom height steps. The suppressive effect of the steps ranged 2.4 nm into the terrace. Formate ions (a possible reaction intermediate) were imaged in-situ during formic acid exposure at the reaction temperature. The local density of the formates and hence the product distribution, which were very low near the steps, were simulated by a model. The particles produced were suggested to be carbonates, CO32- on the bridging oxygen atoms of the TiO2(110) surface.