Structure of a model TiO2 photocatalytic interface

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.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

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.

References

  1. 1

    Henderson, M. A. A surface science perspective on photocatalysis. Surf. Sci. Rep. 66, 185–297 (2011).

    CAS  Article  Google Scholar 

  2. 2

    Fujishima, A. & Honda, K. Electrochemical photolysis of water at a semiconductor electrode. Nature 238, 37–38 (1972).

    CAS  Google Scholar 

  3. 3

    Kurtz, R. L., Stock-Bauer, R., Msdey, T. E., Román, E. & De Segovia, J. L. Synchrotron radiation studies of H2O adsorption on TiO2(110). Surf. Sci. 218, 178–200 (1989).

    CAS  Article  Google Scholar 

  4. 4

    Henderson, M. A. An HREELS and TPD study of water on TiO2(110): the extent of molecular versus dissociative adsorption. Surf. Sci. 355, 151–166 (1996).

    CAS  Article  Google Scholar 

  5. 5

    Brookes, I. M., Muryn, C. A. & Thornton, G. Imaging water dissociation on TiO2(110). Phys. Rev. Lett. 87, 266103 (2001).

    CAS  Article  Google Scholar 

  6. 6

    Bikondoa, O. et al. Direct visualization of defect-mediated dissociation of water on TiO2(110). Nat. Mater. 5, 189–192 (2006).

    CAS  Article  Google Scholar 

  7. 7

    Wendt, S. et al. Formation and splitting of paired hydroxyl groups on reduced TiO2(110). Phys. Rev. Lett. 96, 066107 (2006).

    CAS  Article  Google Scholar 

  8. 8

    He, Y. et al. Nucleation and growth of 1D water clusters on rutile TiO2 (011)-2 × 1. J. Phys. Chem. C 113, 10329–10332 (2009).

    CAS  Article  Google Scholar 

  9. 9

    He, Y., Tilocca, A., Dulub, O., Selloni, A. & Diebold, U. Local ordering and electronic signatures of submonolayer water on anatase TiO2(101). Nat. Mater. 8, 585–589 (2009).

    CAS  Article  Google Scholar 

  10. 10

    Pang, C. L., Lindsay, R. & Thornton, G. Structure of clean and adsorbate-covered single-crystal rutile TiO2 surfaces. Chem. Rev. 113, 3887–3948 (2013).

    CAS  Article  Google Scholar 

  11. 11

    Ramamoorthy, M., Vanderbilt, D. & King-Smith, R. D. First-principles calculations of the energetics of stoichiometric TiO2 surfaces. Phys. Rev. B 49, 16721–16727 (1994).

    CAS  Article  Google Scholar 

  12. 12

    Kristoffersen, H. H. et al. Role of steps in the dissociative adsorption of water on rutile TiO2(110). Phys. Rev. Lett. 110, 146101 (2013).

    CAS  Article  Google Scholar 

  13. 13

    Zhang, Z. et al. Water as a catalyst: imaging reactions of O2 with partially and fully hydroxylated TiO2(110) surfaces. J. Phys. Chem. C 113, 1908–1916 (2009).

    CAS  Article  Google Scholar 

  14. 14

    Renner, F. U. et al. Initial corrosion observed on the atomic scale. Nature 439, 707–710 (2006).

    CAS  Article  Google Scholar 

  15. 15

    Zhang, Z. et al. Ion adsorption at the rutile-water interface: linking molecular and macroscopic properties. Langmuir 20, 4954–4969 (2004).

    CAS  Article  Google Scholar 

  16. 16

    Ketteler, G. et al. The nature of water nucleation sites on TiO2(110) surfaces revealed by ambient pressure X-ray photoelectron spectroscopy. J. Phys. Chem. C 111, 8278–8282 (2007).

    CAS  Article  Google Scholar 

  17. 17

    Cheng, J. & Sprik, M. Aligning electronic energy levels at the TiO2/H2O interface. Phys. Rev. B 82, 081406 (2010).

    Article  Google Scholar 

  18. 18

    Cheng, J. & Sprik, M. Acidity of the aqueous rutile TiO2(110) surface from density functional theory based molecular dynamics. J. Chem. Theory Comput. 6, 880–889 (2010).

    CAS  Article  Google Scholar 

  19. 19

    Liu, L.-M., Zhang, C., Thornton, G. & Michaelides, A. Structure and dynamics of liquid water on rutile TiO2(110). Phys. Rev. B 82, 161415 (2010).

    Article  Google Scholar 

  20. 20

    Liu, L.-M., Zhang, C., Thornton, G. & Michaelides, A. Reply to “Comment on ‘Structure and dynamics of liquid water on rutile TiO2(110)’”. Phys. Rev. B 85, 167402 (2012).

    Article  Google Scholar 

  21. 21

    Raju, M., Kim, S.-Y., van Duin, A. C. T. & Fichthorn, K. A. ReaxFF reactive force field study of the dissociation of water on titania surfaces. J. Phys. Chem. C 117, 10558–10572 (2013).

    CAS  Article  Google Scholar 

  22. 22

    Zhang, Z. et al. Structure of rutile TiO2(110) in water and 1 molal Rb+ at pH 12: Inter-relationship among surface charge, interfacial hydration structure, and substrate structural displacements. Surf. Sci. 601, 1129–1143 (2007).

    CAS  Article  Google Scholar 

  23. 23

    Mezhenny, S. et al. STM studies of defect production on the TiO2(110)-(1 × 1) and TiO2(110)-(1 × 2) surfaces induced by UV irradiation. Chem. Phys. Lett. 369, 152–158 (2003).

    CAS  Article  Google Scholar 

  24. 24

    Maeda, K. Photocatalytic properties of rutile TiO2 powder for overall water splitting. Catal. Sci. Tech. 4, 1949–1953 (2014).

    CAS  Article  Google Scholar 

  25. 25

    Lindan, P. J. D., Harrison, N. M. & Gillan, M. J. Mixed dissociative and molecular adsorption of water on the rutile (110) surface. Phys. Rev. Lett. 80, 762–765 (1998).

    CAS  Article  Google Scholar 

  26. 26

    Uetsuka, H., Sasahara, A. & Onishi, H. Topography of the rutile TiO2(110) surface exposed to water and organic solvents. Langmuir 20, 4782–4783 (2004).

    CAS  Article  Google Scholar 

  27. 27

    Sasahara, A., Kitamura, S., Uetsuka, H. & Onishi, H. Oxygen-atom vacancies imaged by a noncontact atomic force microscope operated in an atmospheric pressure of N2 gas. J. Phys. Chem. B 108, 15735–15737 (2004).

    CAS  Article  Google Scholar 

  28. 28

    Vitali, L., Ramsey, M. G. & Netzer, F. P. Unusual growth phenomena of group III and group V elements on Si(111) and Ge(111) surfaces. Appl. Surf. Sci. 175–176, 146–156 (2001).

    Article  Google Scholar 

  29. 29

    Yim, C. M., Pang, C. L. & Thornton, G. Oxygen vacancy origin of the surface band-gap state of TiO2(110). Phys. Rev. Lett. 104, 036806 (2010).

    CAS  Article  Google Scholar 

  30. 30

    Wendt, S. et al. The role of interstitial sites in the Ti3d defect state in the band gap of titania. Science 320, 1755–1759 (2008).

    CAS  Article  Google Scholar 

  31. 31

    Mao, X. et al. Band-gap states of TiO2(110): major contribution from surface defects. J. Phys. Chem. Lett. 4, 3839–3844 (2013).

    CAS  Article  Google Scholar 

  32. 32

    Cabailh, G. et al. Geometric structure of TiO2(110)(1 × 1): achieving experimental consensus. Phys. Rev. B 75, 241403 (2007).

    Article  Google Scholar 

  33. 33

    Duncan, D. A., Allegretti, F. & Woodruff, D. P. Water does partially dissociate on the perfect TiO2(110) surface: a quantitative structure determination. Phys. Rev. B 86, 045411 (2012).

    Article  Google Scholar 

  34. 34

    Allegretti, F., O’Brien, S., Polcik, M., Sayago, D. I. & Woodruff, D. P. Adsorption bond length for H2O on TiO2(110): a key parameter for theoretical understanding. Phys. Rev. Lett. 95, 226104 (2005).

    CAS  Article  Google Scholar 

  35. 35

    Serrano, G. et al. Molecular ordering at the interface between liquid water and rutile TiO2(110). Adv. Mater. Interfaces 2, 1500256 (2015).

    Article  Google Scholar 

  36. 36

    Papageorgiou, A. C. et al. Electron traps and their effect on the surface chemistry of TiO2(110). Proc. Natl Acad. Sci. USA 107, 2391–2396 (2010).

    Article  Google Scholar 

  37. 37

    Deskins, N. A., Rousseau, R. & Dupuis, M. Defining the role of excess electrons in the surface chemistry of TiO2 . J. Phys. Chem. C 114, 5891–5897 (2010).

    CAS  Article  Google Scholar 

  38. 38

    Amft, M. et al. A molecular mechanism for the water–hydroxyl balance during wetting of TiO2 . J. Phys. Chem. C 117, 17078–17083 (2013).

    CAS  Article  Google Scholar 

  39. 39

    Berkelbach, T. C., Lee, H.-S. & Tuckerman, M. E. Concerted hydrogen-bond dynamics in the transport mechanism of the hydrated proton: a first-principles molecular dynamics study. Phys. Rev. Lett. 103, 238302 (2009).

    Article  Google Scholar 

  40. 40

    Tocci, G. & Michaelides, A. Solvent-induced proton hopping at a water–oxide interface. J. Phys. Chem. Lett. 5, 474–480 (2014).

    CAS  Article  Google Scholar 

  41. 41

    Bullard, J. W. & Cima, M. J. Orientation dependence of the isoelectric point of TiO2 (Rutile) surfaces. Langmuir 22, 10264–10271 (2006).

    CAS  Article  Google Scholar 

  42. 42

    Cheng, H. & Selloni, A. Hydroxide ions at the water/anatase TiO2(101) interface: structure and electronic states from first principles molecular dynamics. Langmuir 26, 11518–11525 (2010).

    CAS  Article  Google Scholar 

  43. 43

    Cheng, J., Liu, X., Kattirtzi, J. A., VandeVondele, J. & Sprik, M. Aligning electronic and protonic energy levels of proton-coupled electron transfer in water oxidation on aqueous TiO2 . Angew. Chem. Int. Ed. 53, 12046–12050 (2014).

    CAS  Article  Google Scholar 

  44. 44

    Valdés, A., Qu, Z.-W., Kroes, G.-J., Rossmeisl, J. & Nørskov, J. K. Oxidation and photo-oxidation of water on TiO2 surface. J. Phys. Chem. C 112, 9872–9879 (2008).

    Article  Google Scholar 

  45. 45

    Renner, F. U., Gründer, Y. & Zegenhagen, J. Portable chamber for the study of UHV prepared electrochemical interfaces by hard x-ray diffraction. Rev. Sci. Instrum. 78, 033903 (2007).

    Article  Google Scholar 

  46. 46

    Kresse, G. & Hafner, J. Ab initio molecular dynamics for liquid metals. Phys. Rev. B 47, 558–561 (1993).

    CAS  Article  Google Scholar 

  47. 47

    Kresse, G. & Furthmüller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    CAS  Article  Google Scholar 

  48. 48

    Kresse, G. & Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758–1775 (1999).

    CAS  Article  Google Scholar 

  49. 49

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    CAS  Article  Google Scholar 

  50. 50

    Heyd, J., Scuseria, G. E. & Ernzerhof, M. Hybrid functionals based on a screened Coulomb potential. J. Chem. Phys. 118, 8207–8215 (2003).

    CAS  Article  Google Scholar 

  51. 51

    VandeVondele, J. et al. Quickstep: fast and accurate density functional calculations using a mixed Gaussian and plane waves approach. Comput. Phys. Commun. 167, 103–128 (2005).

    CAS  Article  Google Scholar 

  52. 52

    VandeVondele, J. & Hutter, J. Gaussian basis sets for accurate calculations on molecular systems in gas and condensed phases. J. Chem. Phys. 127, 114105 (2007).

    Google Scholar 

Download references

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.

Author information

Affiliations

Authors

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.

Corresponding author

Correspondence to G. Thornton.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 35713 kb)

Supplementary Information

Supplementary Movie 1 (MOV 22843 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

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

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing