Abstract

The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption however, here we report single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoS2−xOx crystals. Oxygen substitution sites present all over the basal plane act as single-atom reaction centres, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Data availability

The data supporting the findings of this study are available within the Article and its Supplementary Information files. All other relevant source data are available from the corresponding author upon request.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

  1. 1.

    Liu, L. et al. Graphene oxidation: thickness-dependent etching and strong chemical doping. Nano Lett. 8, 1965–1970 (2008).

  2. 2.

    Luo, Z. et al. Thickness-dependent reversible hydrogenation of graphene layers. ACS Nano 3, 1781–1788 (2009).

  3. 3.

    Chhowalla, M. et al. The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nat. Chem. 5, 263–275 (2013).

  4. 4.

    Jaramillo, T. F. et al. Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts. Science 317, 100–102 (2007).

  5. 5.

    Lauritsen, J. V. et al. Hydrodesulfurization reaction pathways on MoS2 nanoclusters revealed by scanning tunneling microscopy. J. Catal. 224, 94–160 (2004).

  6. 6.

    Lauritsen, J. V. et al. Size-dependent structure of MoS2 nanocrystals. Nat. Nanotech. 2, 53–58 (2007).

  7. 7.

    Dreyer, D. R., Park, S., Bielawski, C. W. & Ruoff, R. S. The chemistry of graphene oxide. Chem. Soc. Rev. 39, 228–240 (2010).

  8. 8.

    Mirabelli, G. et al. Air sensitivity of MoS2, MoSe2, MoTe2, HfS2, HfSe2. J. Appl. Phys. 120, 125102 (2016).

  9. 9.

    Yue, R. et al. HfSe2 films: 2D transition metal dichalcogenides grown by molecular beam epitaxy. ACS Nano 9, 474–480 (2015).

  10. 10.

    Lee, C. H. et al. Tungsten ditelluride: a layered semimetal. Sci. Rep. 5, 10013 (2015).

  11. 11.

    Li, Y., Zhou, Z., Zhang, S. & Chen, Z. MoS2 nanoribbons: high stability and unusual electronic and magnetic properties. J. Am. Chem. Soc. 130, 16739–16744 (2008).

  12. 12.

    Grønborg, S. S. et al. Synthesis of epitaxial single-layer MoS2 on Au(111). Langmuir 31, 9700–9706 (2015).

  13. 13.

    Gao, J. et al. Aging of transition metal dichalcogenide monolayers. ACS Nano 10, 2628–2635 (2016).

  14. 14.

    Longo, R. C. et al. Intrinsic air stability mechanisms of two-dimensional transition metal dichalcogenide surfaces: basal plane versus edge oxidation. 2D Mater. 4, 025050 (2017).

  15. 15.

    Martincova, J., Otyepka, M. & Lazar, P. Is single layer MoS2 stable in the air? Chem. Eur. J. 23, 13233–13239 (2017).

  16. 16.

    Santosh, K. C., Longo, R. C., Wallace, R. M. & Cho, K. Surface oxidation energetics and kinetics on MoS2 monolayer. J. Appl. Phys. 117, 135301 (2015).

  17. 17.

    Rao, R., Islam, A. E., Campbell, P. E., Vogel, E. M. & Marujama, B. In situ thermal oxidation kinetics in few layer MoS2. 2D Mater. 4, 025058 (2017).

  18. 18.

    Bonde, J., Moses, P. G., Jaramillo, T. F., Norskov, J. K. & Chorkendorff, I. Hydrogen evolution on nano-particulate transition metal sulfides. Faraday Discuss. 140, 219–223 (2009).

  19. 19.

    Angelica, A. et al. HfO2 on UV–O3 exposed transition metal dichalcogenides: interfacial reactions study. 2D Mater. 2, 014004 (2015).

  20. 20.

    Walter, T. N., Kwok, F., Simchi, H., Aldosari, H. M. & Mohney, S. E. Oxidation and oxidative vapor-phase etching of few-layer MoS2. J. Vac. Sci. Technol. 35, 021203 (2017).

  21. 21.

    Jaehyun, J. et al. Improved growth behavior of atomic-layer-deposited high-k dielectrics on multilayer MoS2 by oxygen plasma pretreatment. ACS Appl. Mater. Inter. 5, 4739–4744 (2013).

  22. 22.

    Pingli, Q. et al. In situ growth of double-layer MoO3/MoS2 film from MoS2 for hole-transport layers in organic solar cell. J. Mater. Chem. A 2, 2742–2756 (2014).

  23. 23.

    Voiry, D. et al. Conducting MoS2 nanosheets as catalysts for hydrogen evolution reaction. Nano. Lett. 13, 6222 (2013).

  24. 24.

    Juanfeng, X. et al. Controllable disorder engineering in oxygen-incorporated MoS2 ultrathin nanosheets for efficient hydrogen evolution. J. Am. Chem. Soc. 135, 17881–17888 (2013).

  25. 25.

    Liu, X. et al. Insight into the structure and energy of Mo27SxOy clusters. RSC Adv. 7, 9513–9520 (2017).

  26. 26.

    Shu, H., Li, Y., Niu, X. & Wang, J. Greatly enhanced optical absorption of a defective MoS2 monolayer through oxygen passivation. ACS Appl. Mater. Interfaces 8, 13150–13156 (2016).

  27. 27.

    Magda, G. Z. et al. Exfoliation of large-area transition metal chalcogenide single layers. Sci. Rep. 5, 14714 (2015).

  28. 28.

    inhua, H. et al. Exploring atomic defects in molybdenum disulphide monolayers. Nat. Commun. 6, 6293 (2015).

  29. 29.

    Krivanek, O. L. et al. Atom-by-atom structural and chemical analysis by annular dark field electron microscopy. Nature 464, 571–574 (2010).

  30. 30.

    Komsa, H. P. et al. Two-dimensional transition metal dichalcogenides under electron irradiation: defect production and doping. Phys. Rev. Lett. 109, 035503 (2012).

  31. 31.

    Vancsó, P. et al. The intrinsic defect structure of exfoliated MoS2 single layers revealed by scanning tunneling microscopy. Sci. Rep. 6, 29726 (2016).

  32. 32.

    Nagl, C., Haller, O., Platzgummer, E., Scmid, M. & Varga, P. Submonolayer growth of Pb on Cu (111): surface alloying and de-alloying. Surf. Sci. 321, 237–248 (1994).

  33. 33.

    Li, Z. et al. Spontaneous doping of two-dimensional NaCl films with Cr atoms: aggregation and electronic structure. Nanocale 7, 2366 (2015).

  34. 34.

    Bampoulis, P. et al. Defect dominated charge transport and Fermi level pinning in MoS2/metal contacts. ACS Appl. Mater. Interfaces 9, 19278–19286 (2017).

  35. 35.

    Chow, P. K. et al. Defect induced photoluminescence in monolayer semiconducting transition metal dichalcogenides. ACS Nano 9, 1520–1527 (2015).

  36. 36.

    Tongay, S. et al. Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged and free excitons. Sci. Rep. 3, 2657 (2013).

  37. 37.

    Lince, J. R. Mo2−xOx solid solutions in thin films produced by rf-sputter-deposition. J. Mater. Res. 5, 218–222 (1990).

  38. 38.

    Lince, J. R., Hilton, M. R. & Bommannavar, A. S. Oxygen substitution in sputter deposited MoS2 films studied by extended X-ray absorption fine-structure, X-ray photoelectron spectroscopy and X-ray diffraction. Surf. Coat. Technol. 43–44, 640–651 (1990).

  39. 39.

    Fleischauer, P. D. & Lince, J. R. A comparison of oxidation and oxygen substitution in MoS2 solid film lubricants. Tribol. Int. 32, 627–636 (1999).

  40. 40.

    Benoist, L. et al. X-ray photoelectron spectroscopy characterization of amorphous molybdenum oxysulfide thin films. Thin Solid Films 258, 110–114 (1995).

  41. 41.

    Sung, H. S. et al. Bandgap widening of phase quilted, 2D MoS2 by oxidative intercalation. Adv. Mater. 27, 3152–3158 (2015).

  42. 42.

    Henkelman, G., Uberuaga, B. P. & Jónsson, H. A climbing image nudged elastic band method for finding saddle points and minimum energy paths. J. Chem. Phys. 113, 9901–9904 (2000).

  43. 43.

    Nan, H. et al. Strong photoluminescence enhancement of MoS2 through defect engineering and oxygen bonding. ACS Nano 8, 5738–5745 (2014).

  44. 44.

    Hong, L. et al. Activating and optimizing MoS2 basal planes for hydrogen evolution through the formation of strained sulphur vacancies. Nat. Mater. 15, 48–53 (2016).

  45. 45.

    Xia, Z. Hydrogen evolution guiding principles. Nat. Energy 1, 16155 (2016).

  46. 46.

    Jiao, Y., Zheng, Y., Davey, K. & Qiao, S. Z. Activity origin and catalyst design principles for electrocatalytic hydrogen evolution on hetero-atom-doped graphene. Nat. Energy 1, 16130 (2016).

  47. 47.

    Yang, N., Zheng, X., Li, L., Li, J. & Wei, Z. Influence of phosphorus configuration on electronic structure and oxygen reduction reactions of phosphorus-doped graphene. J. Phys. Chem. C 121, 19321 (2017).

  48. 48.

    Komsa, H. P., Berseneva, N., Krashenninikov, A. & Nieminen, R. M. Charged point defects in the flatland: accurate formation energy calculations in two-dimensional materials. Phys. Rev. X 4, 031044 (2014).

  49. 49.

    Su, Y., Gao, S., Lei, F. & Xie, Y. Atomically-thin two-dimensional sheets for understanding active sites in catalysis. Chem. Soc. Rev. 44, 623–636 (2015).

  50. 50.

    Qiao, B. et al. Single-atom catalysis of CO oxidation using Pt1/FeOx. Nat. Chem. 3, 634–641 (2011).

Download references

Acknowledgements

This work was performed in the framework of a NanoFab2D ERC starting grant, H2020 Graphene Core2 project no. 785219 and the Korea Hungary Joint Laboratory for Nanosciences. L.T. acknowledges OTKA grant K108753 and the ‘Lendület’ programme. The work was also supported by a VEKOP-2.3.2-16-2016-00011 grant, supported by the European Structural and Investment Funds. Z.I.P. and P.B.S. acknowledge financial support from the Ministry of Education and Science of the Russian Federation in the framework of the Increase Competitiveness Program of NUST ‘MISIS’ (no. K2-2017-001). Z.I.P. and P.B.S. acknowledge the supercomputer cluster provided by the Materials Modelling and Development Laboratory at NUST “MISIS” (supported via a grant from the Ministry of Education and Science of the Russian Federation no. 14.Y26.31.0005), and the Information Technology Centre of Novosibirsk State University for providing access to the cluster computational resources. Z.I.P. acknowledges the financial support of the Russian Scientific Foundation according to research project no. 18-73-10135 for stability calculations. P.V. acknowledges the Plateforme Technologique de Calcul Intensif (PTCI), which was supported by the FRS-FNRS under convention no. 2.5020.11. P.B.S. acknowledges financial support from the RFBR, via research project no. 16-32-60138 mol_а_dk. The authors thank J. S. Pap for useful discussions on electrochemistry.

Author information

Affiliations

  1. Hungarian Academy of Sciences, Centre for Energy Research, Institute of Technical Physics and Materials Science, 2DNanoelectronics Lendület Research Group, Budapest, Hungary

    • János Pető
    • , Péter Vancsó
    • , Gábor Zsolt Magda
    • , Gergely Dobrik
    •  & Levente Tapasztó
  2. Hungarian Academy of Sciences, Centre for Energy Research, Institute for Energy Security and Environmental Safety, Surface Chemistry and Catalysis Department, Budapest, Hungary

    • Tamás Ollár
  3. Department of Physics, University of Namur, Namur, Belgium

    • Péter Vancsó
  4. National University of Science and Technology MISiS, Moscow, Russia

    • Zakhar I. Popov
    •  & Pavel B. Sorokin
  5. Korea Research Institute for Standards and Science, Daejeon, South Korea

    • Chanyong Hwang

Authors

  1. Search for János Pető in:

  2. Search for Tamás Ollár in:

  3. Search for Péter Vancsó in:

  4. Search for Zakhar I. Popov in:

  5. Search for Gábor Zsolt Magda in:

  6. Search for Gergely Dobrik in:

  7. Search for Chanyong Hwang in:

  8. Search for Pavel B. Sorokin in:

  9. Search for Levente Tapasztó in:

Contributions

L.T. conceived and designed the experiments. J.P. and G.Z.M. prepared the samples and performed the STM measurements. T.O. performed the chemical reduction and electrocatalytic experiments. Z.I.P., P.V. and P.B.S. performed theoretical calculations. G.D. and G.Z.M. conducted Raman and photoluminescence investigations. L.T., P.B.S. and C.H. supervised the project. L.T. wrote the paper. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Levente Tapasztó.

Supplementary information

  1. Supplementary information

    Supplementary Figures 1–15, Supplementary Methods, Supplementary Characterization

About this article

Publication history

Received

Accepted

Published

DOI

https://doi.org/10.1038/s41557-018-0136-2