The interaction of water with TiO2 is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO2(110) interface with water. This has provided an atomic-level understanding of the water–TiO2 interaction. However, nearly all of the previous studies of water/TiO2 interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO2(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O2 and H2O on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO2 photocatalysis.
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The authors would like to thank M. Nicotra, Y. Zhang and M. Allan for assistance with some measurements. This work was funded by grants from the EPSRC (UK) (EP/C541898/1), M.E.C. (Spain) through project MAT2015-68760-C2-2-P, EU ITN SMALL, EU COST Action CM1104, ERC Advanced Grant (G.Thornton, ENERGYSURF No. 267768), ERC Consolidator Grant (A.M., HeteroIce project No. 616121) and the Royal Society. We are grateful to the London Centre for Nanotechnology and UCL Research Computing for computation resources, and to the UKCP consortium (EP/ F036884/1) for access to Archer.
The authors declare no competing financial interests.
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Hussain, H., Tocci, G., Woolcot, T. et al. Structure of a model TiO2 photocatalytic interface. Nature Mater 16, 461–466 (2017). https://doi.org/10.1038/nmat4793
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