Acetic Acid Adsorption on Anatase TiO₂(101)

Abstract

The adsorption and reactivity of acetic acid on anatase TiO2(101) has been investigated with scanning tunneling microscopy (STM). At low coverage, acetic acid is observed to have a characteristic appearance in STM consistent with a dissociative bidentate binding geometry. At room temperature acetic acid has a relatively strong interaction with the anatase (101) surface and a near-unity sticking probability. When deposited at elevated temperatures (420 K), a saturated coverage displays a partially ordered superstructure with two domains across small regions of the anatase surface. The periodicity of these domains was found to be (2 × 1), again consistent with a bidentate binding geometry of the acetate to two neighboring Ti5c sites along the [010] direction. Heating the acetate-covered surface to 570 K in ultrahigh vacuum resulted in clean desorption of ∼90% of the molecules, leaving only a small fraction undesorbed that were mainly situated at the step edges of the anatase. STM tip pulsing of +6 V was also found to desorb acetate molecules from the surface.