Surface analysis of zeolites: an XPS, variable kinetic energy XPS, and low energy ion scattering study

Simon R. Bare, Axel Knop-Gericke, Detre Teschner, Michael Hävacker, Raoul Blume, Tulio Rocha, Robert Schlögl, Ally S.Y. Chan, N. Blackwell, M. E. Charochak, Rik ter Veen, Hidde H. Brongersma

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Abstract

The surface Si/Al ratio in a series of zeolite Y samples has been obtained using laboratory XPS, synchrotron (variable kinetic energy) XPS, and low energy ion scattering (LEIS) spectroscopy. The non-destructive depth profile obtained using variable kinetic energy XPS is compared to that from the destructive argon ion bombardment depth profile from the lab XPS instrument. All of the data indicate that the near surface region of both the ammonium form and steamed Y zeolites is strongly enriched in aluminum. It is shown that when the inelastic mean free path of the photoelectrons is taken into account the laboratory XPS of aluminosilicates zeolites does not provide a true measurement of the surface stoichiometry, while variable kinetic energy XPS results in a more surface sensitive measurement. A comprehensive Si/Al concentration profile as a function of depth is developed by combining the data from the three surface characterization techniques. The LEIS spectroscopy reveals that the topmost atomic layer is further enriched in Al compared to subsequent layers.

Original languageEnglish
Pages (from-to)376-382
Number of pages7
JournalSurface Science
Volume648
DOIs
Publication statusPublished - 1 Jun 2016

Keywords

  • Catalysis
  • LEIS
  • Low energy ion scattering spectroscopy
  • X-ray photoelectron spectroscopy
  • XPS
  • Zeolite

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    Bare, S. R., Knop-Gericke, A., Teschner, D., Hävacker, M., Blume, R., Rocha, T., Schlögl, R., Chan, A. S. Y., Blackwell, N., Charochak, M. E., ter Veen, R., & Brongersma, H. H. (2016). Surface analysis of zeolites: an XPS, variable kinetic energy XPS, and low energy ion scattering study. Surface Science, 648, 376-382. https://doi.org/10.1016/j.susc.2015.10.048