Institute of Materials Chemistry
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Instrumentation

Figure 1: Lab based in-situ NAP-XPS

Lab based in-situ NAP-XPS

Our in situ Near Ambient Pressure XPS (NAP-XPS) system was specially developed for (model) catalyst investigations under reaction conditions. As our current ERC project focuses on electro-catalysis (i.e. sustainable fuel production and chemical energy conversion utilizing fuel cell technology) we particularly designed the sample stage/sample holder to enable catalytic testing with simultaneous electrochemical characterization (3 electrode geometry, laser heating system with temperatures up to 1000°C).

To enable a direct correlation of catalysis with surface structure and electrochemical properties the spectroscopic cell can be operated in flow mode. Online reaction analysis is done by mass spectrometry (MS) and gas chromatography (micro GC). Electrochemical characterisation is achieved via electrochemical impedance spectroscopy (EIS) and by recording current voltage (IV) curves.

With this unique combination of the above-mentioned methods in one system, it is possible to gain information on the performance and surface properties of investigated catalysts in real time.

With our modular sample holder design and the laser heating system it is possible to study a wide variety of samples (e.g. singly crystals, thin films, foils, industrial catalysts). A load lock enables fast sample transfer into and out of the system. Furthermore, the sample stage is exchangeable, giving us the opportunity for constant developments to meet the needs of new projects.

Figure 2: XPS/PM-IRAS Setup

XPS/PM-IRAS Setup

Its main purpose is model catalyst preparation and characterisation and to investigate their properties for heterogeneous catalysis. The setup is custom build, with a high pressure cell for Polarisation Modulation Infrared Reflectance Absorption Spectroscopy (PM-IRAS) measurements (pressure range 10-9 mbar – 1000 mbar) to bridge the prominent gap between UHV and ambient conditions (“pressure gap”). It includes a UHV preparation chamber for sample preparation and characterisation with LEED, XPS, AUGER and TPD. The system is also equipped with gas dosing units and PVD evaporators. After preparation samples can be transferred to the high pressure cell. The cell is designed as circulating batch reactor. At catalytic reactions conditions adsorbed species can be identified on the model catalyst surface. Due to a special sample holder and mounting design we can operate in the temperature range 77 – 1200 K.

Figure 3: XPS/HT-STM Setup

XPS/HT-STM Setup

The system is an extended STM setup from SPECS (Germany) with 3 chambers for STM, sample preparation and a load lock for fast sample transfer into and out of UHV. The preparation chamber is equipped with LEED, TPD, hemispherical analyser and instruments for XPS, AUGER and LEIS measurements. Furthermore the system is equipped with gas dosing units and PVD evaporators. The setup is dedicated to model catalyst preparation and characterisation in UHV.

Figure 4: SFG-Setup “DAISI” with laser optics and UHV + spectroscopic cell

SFG-Setup

The setup is dedicated to model catalysts preparation and characterisation, from single crystals up to supported nanoparticles, and to study their interaction with reactive gases. The setup is comprised of three parts: a UHV preparation chamber, a load lock for fast sample transfer and a spectroscopic cell for investigations under realistic catalytic conditions. The preparation chamber is equipped with the standard tools of surface science: an ion gun, gas dosing, PVD evaporator, mass spectrometer (for TPD) and LEED + Auger optics. Samples can be transferred without breaking the vacuum to the spectroscopic cell which allows to perform SFG (sum frequency generation) spectroscopy under reaction conditions. The cell is designed as circulating batch reactor with the possibility of gas analysis via MS. SFG probes vibrationally the sample in the 1000-4500 cm-1 range and provides inherently surface specific information about the species adsorbed on the specimen. Therefore it can be applied from UHV to ambient pressure and bridges the well-known gap between the classical UHV studies and real catalysis.

Figure 5: Microreactor

Microreactor

In heterogeneous catalysis it is of high interest to investigate how single or polycrystalline model catalysts, whose surfaces have already been prepared and characterised, behave under reaction conditions (i.e. elevated pressure and temperature). This behaviour is reflected by kinetic parameters such as conversion, yield, catalytic productivity and selectivity. Commercially available systems feature reaction volumes which surpass the catalytically active surface area of model catalysts by orders of magnitude, thus lowering the detection sensitivity of reaction gases tremendously. To solve this problem a new system for both catalyst preparation under UHV and performance of reactions on the catalyst’s surface (up to 1 bar) within a dense, dismountable micro reactor was developed. The small cell volume (i.e. cell in cell design) of the continuous flow reactor allows excellent catalytic characterisation of model catalysts.