Water does partially dissociate on the perfect TiO2(110) surface: A quantitative structure determination

Abstract

There has been a long-standing controversy as to whether water can dissociate on perfect areas of a TiO${}_{2}$(110) surface; most early theoretical work indicated this dissociation was facile, while experiments indicated little or no dissociation. More recently the consensus of most theoretical calculations is that no dissociation occurs. New results presented here, based on analysis of scanned-energy mode photoelectron diffraction data from the OH component of O 1$s$ photoemission, show the coexistence of molecular water and OH species in both atop (OH${}_{\mathrm{t}}$) and bridging (OH${}_{\mathrm{br}}$) sites. OH${}_{\mathrm{br}}$ can arise from reaction with oxygen vacancy defect sites (O${}_{\mathrm{vac}}$), but OH${}_{\mathrm{t}}$ have only been predicted to arise from dissociation on the perfect areas of the surface. The relative concentrations of OH${}_{\mathrm{t}}$ and OH${}_{\mathrm{br}}$ sites arising from these two dissociation mechanisms are found to be fully consistent with the initial concentration O${}_{\mathrm{vac}}$ sites, while the associated Ti-O bond lengths of the OH${}_{\mathrm{t}}$ and OH${}_{\mathrm{br}}$ species are found to be 1.85 \ifmmode\pm\else\textpm\fi{} 0.08 and 1.94 \ifmmode\pm\else\textpm\fi{} 0.07 \AA{}, respectively.