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).

 

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.

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

Assigned to beamline(s)

Energy rangePolarisation
CPMU17_EMIL 2000 eV to 10000 eV
UE48_EMIL 80 eV to 2300 eV
Station data
AP-HE-XPS
Temperature range
Pressure Range
Detector
Manipulators
Sample holder compatibility
Remote Access
operated by EM-GKAT / Fritz-Haber-Institut der MPG
min. pressure 10-10 Pa
max. pressure 2500 Pa
typical pressure 500 Pa
min. sample temperature 25 °C
max. sample temperature 1000 °C
gas analytics
  • electron impact mass spectrometer (differentially pumped)
  • proton-transfer-reaction mass spectrometer (PTR-MS)
  • (micro) gas chromatograph
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


  • 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.