Paper SS2-WeM12
Reaction of Water with Terminal Hydroxyls on TiO₂(110) Surface

Wednesday, November 2, 2011, 11:40 am, Room 109

We report a combined experimental and theoretical investigation of the reaction of molecular water with terminal hydroxyls (OH_t’s) on reduced TiO₂(110)-(1x1) surface at 300 K. We show that OH_t’s have a significant effect on the water reactivity and extract molecular-level details about the underlying reaction mechanisms. By tracking the same surface area with high-resolution scanning tunneling microscopy before and after water exposure, we demonstrate that there are two distinctive reaction pathways involving multiple proton transfers [1]. For water interaction with OH_t on an adjacent Ti row, the proton can be transferred through bridging oxygen to OH_t, which leads to the formation of a new water molecule and apparent across-row motion of OH_t due to O scrambling. This process further manifests the existence of the equilibrium between molecular and dissociated states of water on TiO₂(110) [2]. If H₂O interacts with OH_t along the same Ti row, fast multi-step OH_t motion along the Ti row is observed. Our density functional theory results show that this process is caused by the fast diffusion of (OH_t + H₂O) pairs, whereby the underlying mechanism involves proton transfer and H₂O hopping over OH_t.

[1] Y. Du, N. A. Deskins, Z. Zhang, Z. Dohnálek, M. Dupuis, and I. Lyubinetsky, Phys. Chem. Chem. Phys. 12 (2010) 6337.

[2] Y. Du, N. A. Deskins, Z. Zhang, Z. Dohnálek, M. Dupuis, and I. Lyubinetsky, Phys. Rev. Lett. 102 (2009) 096102.

This work was supported by the U.S. Department of Energy (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, and performed at EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.