My research is focused on catalytic surface reactions on heterogeneous catalysts, employing a three-pronged approach: (i) surface-science based planar model catalysts, (ii) atomically-precise clusters, and (iii) technological industrial-grade nanomaterials. Molecular mechanisms of hydrogen as clean fuel, methane reforming, CO2 hydrogenation, automotive catalysis and waste remediation are studied on mono- (Pt, Pd, Rh, Cu, Ni, Au, Co) and bimetallic (PdZn, Pd2Ga, PdCu, CuNi, CuZn, PdAu, AgAu, CuAu) surfaces/nanoparticles on supporting (mixed) oxides (Al2O3, SiO2, CeO2, ZrO2, TiO2, ZnO, Ga2O3, Co3O4), perovskites (LCO, LSF), and carbon (HOPG, Graphene).
As examining functioning catalysts at near atmospheric pressure (NAP) and realistic temperature is crucial, dedicated UHV-compatible high-pressure cells have been developed for model catalysts (single crystals, thin films, nanoparticles), enabling in situ sum frequency generation (SFG) spectroscopy, polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS) and X-ray photoelectron spectroscopy (NAP-XPS). Corresponding in situ (operando) spectroscopy of nanomaterials is carried out by Fourier transform infrared spectroscopy (FTIR), X-ray absorption spectroscopy (XAS), NAP-XPS and X-ray diffraction (XRD). Significant advances were made in imaging the local kinetics of surface reactions by in situ surface microscopy, with photoemission electron microscopy (PEEM) and field emission/ion microscopy (FEM/FIM) being applied. Most studies were performed at synchrotron sources and in lock-step with theory (DFT) collaborations.
Most relevant scientific results
- I am among the first researchers in ambient pressure surface science, developing UHV-compatible high-pressure cells for combined kinetics and in situ surface spectroscopy : SFG with G.A. Somorjai, SFG/PM-IRAS with H.-J. Freund, NAP-XPS with V.I. Bukhtiyarov. One specific high-pressure cell (“Rupprechter design”) is used by several groups worldwide.
- Fundamentals and applications of (near) ambient pressure surface spectroscopy (SFG/PM-IRAS-NAP-XPS/XAS/DRIFTS) were summarized in several review articles that exemplified the power of in situ (now more precisely defined as operando) studies of catalytic reactions [1,2].
- The very first paper of SFG spectroscopy on oxide supported Pd nanoparticles, demonstrating size and pressure (UHV to mbar) effects in CO adsorption. Ref.  triggered many follow-up studies, also combined with NAP-XPS (JPC B 2003/2004, Appl. Surf. Sci. 2004). My SFG activities continue till today, including single crystals (Top. Catal. 2018), thin films, and nanoparticles .
- Developing in situ surface microscopy, i.e., locally-resolved imaging of ongoing surface reactions by PEEM (with Y. Suchorski), enabling the observation and explanation of novel phenomena such as facet-resolved catalytic ignition, multifrequential oscillations, and long-ranging metal/oxide interface effects. Refs.  and  opened a new pathway to investigate catalyst heterogeneity and structure sensitivity, based on a 10-year research effort in developing the concepts of kinetics by imaging and surface structure and particle size libraries. Combining PEEM and DFT/microkinetics (with H. Grönbeck and K.M. Neyman) yielded true fundamental insights. Recently, PEEM was combined with ESCA-microscopy (Scanning Photoelectron Microscopy) .
- Molecular-level operando insights into selective methanol steam reforming on PdZn and PdGa intermetallics (NAP-XPS, PM-IRAS, concentration modulation IR, EXAFS) and DFT (with B. Klötzer, D. Ferri, K.M. Neyman) . We could link selectivity to the catalyst atomic and electronic (VB) structure, backed by DFT (JPC C 2015). Model and applied studies blended well together.
- Connecting model and applied catalysis of ZrO2-based reforming catalysts by in situ (synchrotron) NAP-XPS and XAS spectroscopy, employing ultrathin (trilayer) ZrO2 films (Surf. Sci. 2019, JPC C 2015) and nanopowders of ZrO2 and ZrO2/CeO2 (Catal. Tod. 2016/2017). Further studies of methane dry reforming revealed SMSI effects (J. Phys. Cond. Matt. 2018), Ni surface segregation in bimetallic CuNi/ZrO2, and coke suppression for Ni/ZrO2/CeO2 .
- Operando surface spectroscopy (XAS, NAP-XPS, FTIR, XRD) of CO oxidation and PROX on Co3O4 catalysts, exploiting both static and dynamic conditions, revealed a complex reaction network (, ACS Catal. 2018; J. Phys. Cond. Matt. 2022). The presumably active (oxygen vacancy) sites were a minority species. Further studies contrasted Co3O4 to Co3O4/CeO2 and CoO.
- Single-particle catalysis by field electron microscopy (FEM), resolving interfacet coupling and its collapse. Using the ionized water product as imaging species, active sites were directly imaged in situ by field ion microscopy (FIM) .
- Surface chemistry of Au clusters on ceria-praseodymia mixed oxide supports: Au/Ce4Pr1Ox exhibited the highest activity in water gas shift, with combined experimental and theoretical studies revealing that asymmetric O vacancies facilitate H2O dissociation .
- Combining atmospheric pressure reaction kinetics of the complex 1-butene hydrogenation and isomerization on Pd/Al2O3 model catalysts with DFT calculations and microkinetic modeling (by A. Genest and N. Rösch), the particle size-dependent selectivity could be rationalized based on the abundance and the specific properties of the contributing surface facets .
- 2010–present: Head of the Institute of Materials Chemistry, TU Wien
- 2005–present: Full Professor (Chair) of Surface & Interface Chemistry, IMC, TU Wien, Austria
- 1998–2006: Group Leader for Laser Spectroscopy & Catalysis at the Fritz Haber Institute, Max Planck Society, Chemical Physics Department, Berlin, Germany (with H.-J. Freund)
- 1996–1998: Postdoc. Fellow at the Department of Chemistry, University of California at Berkeley and E.O. Lawrence Berkeley National Laboratory (with G.A. Somorjai)
- 2005: Habilitation for Physical Chemistry, Technical University Berlin, Germany
- 1996: Ph.D. Chemistry (Dr. rer. nat.), summa cum laude, University Innsbruck, Austria
- 1992: M.Sc. Chemistry (Mag. rer. nat.), summa cum laude, University Innsbruck, Austria