OH Group Dynamics of 1,3-Propanediol on TiO2(110)

Abstract

Variable-temperature scanning tunneling microscopy and dispersion-corrected density functional theory were employed to study the interaction of 1,3-propanediol with reduced TiO2(110) surfaces. We find that at 300 K, 1,3-propanediol molecules dissociate via O–H bond scission of one of the OH groups on bridge-bonded oxygen (Ob) vacancy (VO) defects forming pairs of monoalkoxide (Ob–(CH2)3–OH) and bridge-bonded bonded hydroxyl (HOb) species. The OH group of the monoalkoxide species is bound to the adjacent 5-coordinated Ti4+ (Ti5c) sites. The Ob–(CH2)3–OH species are observed to rotate around their Ob anchor, switching the position of the OH between the two adjacent Ti5c rows. The rotating species are found to assist cross-Ob row HOb hydrogen transfer. The OH group of the monoalkoxide species is further observed to dissociate forming a bidentate type dioxo (Ob–(CH2)3–OTi5c) species and an additional HOb. The reversible interconversion between the mono and dioxo species illustrates the attainment of a dynamic...