CAT

CAT@EMIL

The scientific aim at CAT@EMIL is to study the electronic surface/near surface structure of functional materials in the presence of a reactive environment. This includes both gas/solid interfaces (e.g. heterogeneous catalysis) and liquid/solid interfaces (e.g. catalytic water splitting).

Fig. 1: Sketch demonstrating the main components of the AP-HE-XPS (left). Photo of the complete AP-HE-XPS endstation (right, courtesy of Specs GmbH, Berlin)

Fig. 1: Sketch demonstrating the main components of the AP-HE-XPS (left). Photo of the complete AP-HE-XPS endstation (right, courtesy of Specs GmbH, Berlin)


Methods

Time-resolved absorption, NEXAFS, EXAFS, Mass Spectrometry, XPS, NAP-XPS, HAXPES

Remote access

depends on experiment - please discuss with Instrument Scientist

Station data
AP-HE-XPS
Temperature range 25 - 800 °C
Pressure range 10-12 - 20 mbar; typically 1 mbar
Detector 2D delay line detector (2D DLD) (SURFACE CONCEPT, Mainz)
Manipulators various, exchangeable for optimised sample environments
Sample holder compatibility Homemade concept. For details contact the station manager.
Additional equipment gas analytics
• electron impact mass spectrometer (differentially pumped)
• proton-transfer-reaction mass spectrometer (PTR-MS)
• (micro) gas chromatograph
Applicable at beamline(s)
UE48_EMIL 80 eV to 2000 eV
CPMU17_EMIL
  • PGM: 700-1600 eV (not available @PINK)
  • DCM: 2200-10000 eV
  • Multilayer mono @PINK: 2300-9500eV
  • Fig. 2: Sketch demonstrating the main components of the vP-XAS instrumentof the AP-HE-XPS (left). Photo of the complete AP-HE-XPS endstation (right, courtesy of Specs GmbH, Berlin)

    Fig. 2: Sketch demonstrating the main components of the vP-XAS instrumentof the AP-HE-XPS (left). Photo of the complete AP-HE-XPS endstation (right, courtesy of Specs GmbH, Berlin)

    Table. 1: Gas analytics

    Table. 1: Gas analytics


    Ambient pressure - High Energy XPS (AP-HE-XPS)

    The scientific aim at CAT@EMIL is to study the electronic surface/near surface structure of functional materials in the presence of a reactive environment. This includes both gas/solid interfaces (e.g. heterogeneous catalysis) and liquid/solid interfaces (e.g. catalytic water splitting).

    Obviously, the understanding of the interaction of a catalyst surface with the reactants plays a key role in a detailed description of catalytic processes. X-ray photoelectron spectroscopy (XPS) is a well-established powerful tool to study in detail the outermost surface of solids but it was traditionally restricted to high vacuum and low pressure conditions. However, recently a methodology based on a differentially pumped electrostatic lens system has gained much interest. Such an instrument is operated by the  Fritz-Haber-Institut der MPG (FHI-MPG) at HZB/BESSY II at the ISISS beamline in the low photon energy range. A further developed set-up will be installed at EMIL. The feasibility to investigate buried layers is added by the extension of the kinetic energy range of photo-electrons to up to 7000eV. A very flexible, modular sample environment has been developed that allows to apply AP-XPS to a huge variety of problems.

    A sketch of the main components of the AP-HE-XPS instrument and a photo of the complete set-up (courtesy of SPECS GmbH, Berlin) is shown as Fig. 1.

     

    Variable pressure soft X-ray absorption (vP-XAS)

    A variable pressure soft X-ray absorption experiment has been constructed by FHI that works in the conversion electron yield detection mode. This set-up allows to measure surface sensitive X-ray absorption spectra in a pressure range between 102 - 105 Pa, i.e. up to atmospheric pressure at temperatures up to 400ºC. This instrument makes it feasible to study heterogeneous catalytic reactions in a broad pressure range and hence allows to link results obtained with AP-XPS and measurments obtained in a catalytic reactor.

    A sketch of the set-up is shown in Fig. 2. Similar to the AP-XPS the vP-XAS set-up is rigged in a movable frame which provides the possibility to exchange instruments to be used as endstation at EMIL.

    • X-ray photoelectron spectroscopy (XPS) under high vacuum (p=10-10 Pa) and ambient pressure conditions (typically p=100 Pa).
    • X-ray aborption spectroscopy (XAS) at pressure up to 1k Pa with NAP-HE-XPS endstation. Installation of variable pressure XAS endstation instead of NAP-HE-XPS system allows NEXAFS in electron yield mode at variable pressure between 1 - 100 kPa at temperatures up to 400ºC.