Surface chemistry, structure, and reactivity
of multi-component spinel nanoparticles
Multi-component spinel oxides are complex materials. Understanding their properties and reactivity is challenging, even more so when considering defect-rich nanoparticles under actual reaction conditions.
In P10, we will apply a comprehensive, multi-technique operando approach to investigate Fe-based spinel oxide nanoparticles used as WGS and oxidation catalysts in the gas and liquid phase. We will determine their surface composition, particularly under reaction conditions, the state, coordination environment, and role of the constituent cations, and the influence of defects. We will link these properties to the reactivity and interaction with O2, H2O, H2, CO, and CO2. Furthermore, we will evaluate how spinels and their surfaces change when exposed to the liquid phase. Our experimental approach comprises synthesis, characterization (TEM, XRD, XPS, TPD, titration of sites and defects, IR of probe molecules), steady-state and transient kinetics, and operando characterization (IR, NAP-XPS, XAS).
In close interaction with surface science (P04 Parkinson), we will compare the nanoparticulate materials to single-crystal and thin-film model systems. For understanding complex materials, a close collaboration with the surface science and theory groups is essential. In return, our results on technologically relevant nanoparticles under operation conditions will help to validate and adapt models and address the influence of high defectivity, low coordinated sites, disorder, and low crystallinity. We aim to bridge fundamental theory studies, surface science experiments, and model studies (P11 Backus) towards real-world application.
Our group has long term experience in the application of operando spectroscopy (FTIR, XPS and XAS) for studying heterogeneous catalysts. Our research interests are centered around establishing structure-performance relations of oxides and supported metal nanoparticles and identifying reaction mechanisms. Understanding the elementary reaction steps occurring at the catalyst surface and identification of the involved intermediates and surface sites under relevant conditions is a main focus and crucial for a rational design and improvement of catalytic materials.
Methods and expertise available in our lab include:
- in situ/operando FTIR (transmission, DRIFTS and ATR-IR) during catalytic reactions (steady-state and concentration modulation setups)
- several laboratory-scale flow reactors equipped with gas chromatographs and mass spectrometers for performing catalytic reactions in the gas and liquid phase
- in-situ Near Ambient Pressure XPS setup
- volumetric physisorption and chemisorption, dynamic (pulsed) chemisorption
- temperature-programmed methods (TPD, TPR, TPO)
- DR-UV/VIS spectroscopy
- thermal analysis (DSC and TGA)
- fully equipped synthesis lab
- we regularly perform in situ XAS and high resolution XRD/total scattering at synchrotron facilities using dedicated operando cells
- we frequently utilize HR-TEM with EDX and EELS, SEM, XRF, XRD (including in situ XRD) and ICP-MS available via service centers and/or collaborations
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