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Structure of a model TiO2 photocatalytic interface

Nature Materials volume 16, pages 461–466 (2017)Cite this article

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Abstract

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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Figure 1: The TiO2(110) surface.
Figure 2: Selected CTRs from the SXRD measurements alongside proposed models.
Figure 3: Possible sequence of reaction steps leading to the formation of the OHt (2 × 1) overlayer.
Figure 4: Structure of the water/TiO2 interface in aqueous conditions.

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Acknowledgements

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.

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Author notes

  1. H. Hussain, G. Tocci, D. C. Grinter & J. Zegenhagen

    Present address: Present addresses: Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK (H.H.); Laboratory for Fundamental BioPhotonics and Laboratory of Computational Science and Modeling, Institutes of Bioengineering and Materials Science and Engineering, School of Engineering, and Lausanne Centre for Ultrafast Science, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland (G.T.); Chemistry Department, Building 555, Brookhaven National Laboratory, Upton, New York 11973, USA (D.C.G.); Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot OX11 0DE, UK (J.Z.).,

Authors and Affiliations

  1. London Centre for Nanotechnology and Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ, UK

    H. Hussain, G. Tocci, T. Woolcot, C. L. Pang, D. S. Humphrey, C. M. Yim, D. C. Grinter, A. Michaelides & G. Thornton

  2. ESRF, 6 rue Jules Horowitz, F-38000 Grenoble cedex, France

    H. Hussain & J. Zegenhagen

  3. Institut de Ciència de Materials de Barcelona (CSIC), Campus UAB, 08193 Bellaterra, Spain

    X. Torrelles

  4. Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, F-75005 Paris, France

    G. Cabailh

  5. Department of Physics, University of Warwick, Gibbet Hill Road, Coventry C4 7AL, UK

    O. Bikondoa

  6. Corrosion and Protection Centre, School of Materials, The University of Manchester, Sackville Street, Manchester M13 9PL, UK

    R. Lindsay

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Contributions

G.Thornton, J.Z. and A.M. designed the project. D.S.H., T.W., C.L.P., C.M.Y., D.C.G. and H.H. performed the STM measurements and T.W. analysed the data. T.W. and C.M.Y. performed the UPS experiments with T.W. analysing the data. H.H., G.C., O.B., X.T., R.L. and G.Thornton performed the SXRD measurements and H.H. and X.T. analysed the data. G.Tocci and A.M. conceived, designed and analysed the ab initio calculations. G.Tocci performed the ab initio calculations. H.H., T.W., G.Tocci, C.L.P., A.M. and G.Thornton wrote the manuscript and the Supplementary Information with input from all authors. All authors participated in discussing the data.

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Correspondence to G. Thornton.

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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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