Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Dopants adsorbed as single atoms prevent degradation of catalysts

Nature Materials volume 3, pages 143–146 (2004)Cite this article

An Erratum to this article was published on 01 April 2004

Abstract

The design of catalysts with desired chemical and thermal properties is viewed as a grand challenge for scientists and engineers1. For operation at high temperatures, stability against structural transformations is a key requirement. Although doping has been found to impede degradation, the lack of atomistic understanding of the pertinent mechanism has hindered optimization. For example, porous γ-Al2O3, a widely used catalyst and catalytic support2,3,4,5,6, transforms to non-porous α-Al2O3 at ∼1,100 °C (refs 7–10). Doping with La raises the transformation temperature8,9,10,11 to ∼1,250 °C, but it has not been possible to establish if La atoms enter the bulk, adsorb on surfaces as single atoms or clusters, or form surface compounds10,11,12,13,14,15. Here, we use direct imaging by aberration-corrected Z-contrast scanning transmission electron microscopy coupled with extended X-ray absorption fine structure and first-principles calculations to demonstrate that, contrary to expectations, stabilization is achieved by isolated La atoms adsorbed on the surface. Strong binding and mutual repulsion of La atoms effectively pin the surface and inhibit both sintering and the transformation to α-Al2O3. The results provide the first guidelines for the choice of dopants to prevent thermal degradation of catalysts and other porous materials.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: La atoms on g-Al2O3 flake in [100] orientation.
Figure 2: Depth-sensitive STEM experiment.
Figure 3: Fourier transforms (into direct space) of the synchrotron EXAFS La LIII-edge spectra χ(k) (where k is the wave vector) of La/γ-Al2O3 samples (R denotes distance from La atom).
Figure 4: Configurations for the (100) surface of γ-Al2O3, determined by first-principles calculations.

Similar content being viewed by others

References

  1. Bell, A.T. The impact of nanoscience on heterogeneous catalysis. Science 299, 1688–1691 (2003).

    Article  CAS  Google Scholar 

  2. Satterfield, C.N. Heterogeneous Catalysis in Practice (McGraw Hill, New York, 1980).

    Google Scholar 

  3. Knozinger, H. & Ratnasamy, P. Catalytic aluminas – surface models and characterization of the surface sites. Catal. Rev. Sci. Eng. 17, 31–69 (1978).

    Article  Google Scholar 

  4. Gates, B.C. Supported metal clusters: synthesis, structure, and catalysis. Chem. Rev. 95, 511–522 (1995).

    Article  CAS  Google Scholar 

  5. Xu, Z. et al. Size-dependent catalytic activity of supported metal clusters. Nature 372, 346–8 (1994).

    Article  CAS  Google Scholar 

  6. Lin, V.S.Y. et al. Oxidative polymerization of 1,4-diethynylbenzene into highly conjugated poly(phenylene butadiynylene) within the channels of surface-functionalized mesoporous silica and alumina materials. J. Am. Chem. Soc. 124, 9040–9041 (2002).

    Article  CAS  Google Scholar 

  7. Wefers, K. & Misra, C. Oxides and hydroxides of aluminum. (Alcoa Technical Paper No.19, Alcoa Laboratories, Pittsburgh, 1987).

    Google Scholar 

  8. Arai, H. & Machida, M. Thermal stabilization of catalyst supports and their application to high-temperature catalytic combustion. Appl. Catal. A 138, 161–176 (1996).

    Article  CAS  Google Scholar 

  9. Church, J.S., Cant, N.W. & Trimm, D.L. Surface area stability and characterization of a novel sulfate-based alumina modified by rare earth and alkaline earth ions. Appl. Catal. A 107, 267–276 (1994).

    Article  CAS  Google Scholar 

  10. Glazov, M.V., Novak, J. & Hector, L.G. Stabilization of γ-alumina: how much lanthanum do we actually need? (Alcoa Technical Paper No. 99–168, Alcoa Technical Center, Pittsburgh, 1999).

  11. Kumar, K.-N.P., Tranto, J., Kumar, J. & Engell, J.E. Pore-structure stability and phase transformation in pure and M-doped (M = La, Ce, Nd, Gd, Cu, Fe) alumina membranes and catalyst supports. J. Mater. Sci. Lett. 15, 266–270 (1996).

    Article  CAS  Google Scholar 

  12. Oudet, F., Courtine, P. & Vieux, A. Thermal stabilization of transition alumina by structural coherence with lanthanide aluminum oxide (LnAlO3, Ln = lanthanum, praseodymium, neodymium). J. Catal. 114, 112–120 (1988).

    Article  CAS  Google Scholar 

  13. Beguin, B., Garbowski, E. & Primet, M. Stabilization of alumina by addition of lanthanum. Appl. Catal. 75, 119–132 (1991).

    Article  CAS  Google Scholar 

  14. Vazquez, A. et al. X-ray diffraction, FTIR, and NMR characterization of sol–gel alumina doped with lanthanum and cerium. J. Solid State Chem. 128, 161–168 (1997).

    Article  CAS  Google Scholar 

  15. Yamamoto, T., Tanaka, T., Matsuyama, T., Funabiki, T. & Yoshida, S. Structural analysis of La/Al2O3 catalysts by La K-edge XAFS. J. Synchrotron Rad. 8, 634–636 (2001).

    Article  CAS  Google Scholar 

  16. Batson, P.E., Dellby, N. & Krivanek, O.L. Sub-ångstrom resolution using aberration corrected electron optics. Nature 418, 617–620 (2002).

    Article  CAS  Google Scholar 

  17. Blonski, S. & Garofalini, S.H. Molecular dynamics simulations of γ-alumina and α-alumina surfaces. Surf. Sci. 295, 263–274 (1993).

    Article  CAS  Google Scholar 

  18. Sohlberg, K., Pennycook, S.J. & Pantelides, S.T. Explanation of the observed dearth of three-coordinated Al on γ-alumina surfaces. J. Am. Chem. Soc. 121, 10999–11001 (1999).

    Article  CAS  Google Scholar 

  19. Pennycook, S.J. & Jesson, D.E. High-resolution incoherent imaging of crystals. Phys. Rev. Lett. 64, 938–941 (1990).

    Article  CAS  Google Scholar 

  20. Kirkland, E.J. Advanced Computing in Electron Microscopy (Plenum, New York, 1998).

    Book  Google Scholar 

  21. Shannon, R.D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Cryst. A 32, 751–767 (1976).

    Article  Google Scholar 

  22. Burtin, P., Brunelle, J.P., Pijolat, M. & Soustelle, M. Influence of surface area and additives on the thermal stability of transition alumina catalyst supports. I. Kinetic data. Appl. Catal. 34, 225–238 (1987).

    Article  CAS  Google Scholar 

  23. Rashkeev, S.N. et al. Transition metal atoms on different alumina phases: The role of subsurface sites on catalytic activity. Phys. Rev. B 67, 115414 (2003).

    Article  Google Scholar 

  24. Krivanek, O.L., Dellby, N. & Lupini, A.R. Towards sub-Å electron beams. Ultramicroscopy 78, 1–11 (1999).

    Article  CAS  Google Scholar 

  25. Kresse, G. & Furthmüller, J. Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Comput. Mater. Sci. 6, 15–50 (1996).

    Article  CAS  Google Scholar 

  26. Perdew, J.P. Density-functional approximation for the correlation energy of the inhomogeneous electron gas. Phys. Rev. B 33, 8822–8824 (1986).

    Article  CAS  Google Scholar 

  27. Becke, A.D. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A 38, 3098–3100 (1988).

    Article  CAS  Google Scholar 

  28. Vanderbilt, D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. Phys. Rev. B 41, 7892–7895 (1990).

    Article  CAS  Google Scholar 

  29. Blöchl, P.E. Projector augmented-wave method. Phys. Rev. B 50, 17953–17979 (1994).

    Article  Google Scholar 

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

    Article  CAS  Google Scholar 

Download references

Acknowledgements

We thank Valeria V. Vavilova and Yanzhao Cao for their help and John W. Novak, Jr for his support. Access to the Novosibirsk Synchrotron Facility (Russian Academy of Sciences) and to the Florida State University supercomputers (csit1 and csit2) are also gratefully acknowledged. This work was supported in part by National Science Foundation Grant DMR-0111841, Department of Energy Grant at Drexel University DE-FC02-01CH11085, by the William A. and Nancy F. McMinn Endowment at Vanderbilt University, by the Division of Materials Sciences, by Laboratory Directed R&D Program for the US Department of Energy, under contract DE-AC05-00OR22725 managed by UT-Battelle, and by an appointment to ORNL Postdoctoral Research Program administered jointly by ORNL and Oak Ridge Institute for Science and Education (ORISE).

Author information

Authors and Affiliations

  1. Department of Physics and Astronomy, Vanderbilt University, Nashville, 37235, Tennessee, USA

    Sanwu Wang, Sergey N. Rashkeev, Stephen J. Pennycook & Sokrates T. Pantelides

  2. Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831, Tennessee, USA

    Albina Y. Borisevich, Stephen J. Pennycook & Sokrates T. Pantelides

  3. Alcoa Technical Center, Alcoa Center, Pennsylvania, 15069-0001, USA

    Michael V. Glazoff

  4. Department of Chemistry, Drexel University, Philadelphia, 19104, Pennsylvania, USA

    Karl Sohlberg

Authors
  1. Sanwu Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Albina Y. Borisevich
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Sergey N. Rashkeev
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Michael V. Glazoff
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Karl Sohlberg
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Stephen J. Pennycook
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Sokrates T. Pantelides
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Albina Y. Borisevich.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Rights and permissions

Reprints and permissions

About this article

Cite this article

Wang, S., Borisevich, A., Rashkeev, S. et al. Dopants adsorbed as single atoms prevent degradation of catalysts. Nature Mater 3, 143–146 (2004). https://doi.org/10.1038/nmat1077

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat1077

This article is cited by

Search

Advanced 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