"In situ surface characterization of catalysts by synchrotron based ambient pressure X-ray electron spectroscopy" Michael Haevecker, MPI for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Muelheim a.d. Ruhr, Germany

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Inma Hernández

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https://indico.cells.es/indico/event/149/

Abstract

The surface of functional materials like catalysts responds to the ambient conditions. X-ray photoelectron spectroscopy (XPS) and soft X-ray absorption spectroscopy (XAS) are one of the most versatile methods for the investigation of surfaces on the atomic scale providing quantitative information about the elemental composition and chemical specificity. Surface sensitive in situ spectroscopy, i.e. in the presence of a reactive environment allows studying the formation of the interface (gas/solid or liquid/solid) of a catalyst with time and thus adds a dynamic dimension to the spectroscopic characterization. The ISISS facility (Innovative Station for In Situ Spectroscopy) operated by the Fritz Haber Institute (FHI) since 2007 at the synchrotron radiation source BESSY II of the Helmholtz-Zentrum Berlin (HZB) is dedicated to this kind of in situ studies by ambient pressure XPS (AP-XPS) and variable pressure soft-XAS (vP-XAS). Examples will be presented of studies on complex mixed oxides such as MoVTeNbOx [1,2] and other technical catalysts. Some details on instrumentation for such studies will be given.

Furthermore, an outlook on future activities at HZB/BESSY to develop further synchrotron based ambient pressure characterization methodologies will be given including reaction cells based on electron transparent membranes [4,5] and EMIL, The Energy Materials In-Situ Laboratory Berlin. This novel facility will provide an unusual broad photon energy range from 80eV – 8000eV in one spot and (among others) a AP-high kinetic energy XPS endstation capable to operate at kinetic energy of photoelectrons up to 7000eV that allows studying buried layers and liquid/solid interfaces [5].

References

  1. Trunschke, A. et al. The impact of the bulk structure on surface dynamics of complex Mo-V based oxide catalysts. ACS. Catal. 7, 3061-3071 (2017).
  2. Hävecker, M. et al. Surface chemistry of phase-pure M1 MoVTeNb oxide during operation in selective oxidation of propane to acrylic acid. J. Catalysis. 285, 48-60 (2012).
  3. Stoll, J.D. et al. Electron transparent graphene windows for environmental electron scanning microscopy in liquids and dense gases. Nanotechnology. 23, 505704 (2012).
  4. Velasco-Vélez, J.J. et al. Atmospheric pressure X-ray photoelectron spectroscopy apparatus: Bridging the pressure gap. Rev. Sci. Instr. 87, 053121 (2016).
  5. Hendel, S. et al. The EMIL project at BESSY II. AIP Conf. Proc. 1741, 030038 (2016).