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 early 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 world-wide but several more HP-cell designs were developed (Rev. Sci. Instr. 2000/2001/2018, Top. Catal. 2001, PCCP 2001).
- Fundamentals and applications of (near) ambient pressure surface spectroscopy (SFG/PM-IRAS-NAP-XPS) were summarized in a number of review articles that exemplified the power of in-situ (or operando) studies of catalytic reactions (Ref. , Catal Tod. 2007, Nano Tod. 2007, J. Phys: Cond. Matt. 2008, Acc. Chem. Res. 2014, Textb. Surf. Interf. Sci. 2016, Small 2021).
- Very first paper of SFG spectroscopy on oxide supported Pd nanoparticles, demonstrating size and pressure (UHV to mbar) effects in CO adsorption. Ref.  triggered follow-up studies, combined with NAP-XPS (JPC B 2003/2004, (Appl.) Surf. Sci. 2004). My SFG activities continue till today, on single crystals (Top. Catal. 2018), thin films, nanoparticles (Rev. Sci. Instr. 2018, ACS Catal. 2021), and single atoms (Nat. Comms. 2018).
- 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 (ChemPhysChem 2010, Surf. Sci. 2011/2016/2019, ACiE 2012, Catal. Lett. 2018 (Perspective), JPC C 2013/2019). Combining PEEM and DFT/microkinetics (with H. Grönbeck and K.M. Neyman) yielded fundamental insights. Recently, PEEM was combined with ESCA-microscopy (Scanning Photoelectron Microscopy).
- Molecular level insights on selective methanol steam reforming on PdZn and PdGa intermetallics via operando surface spectroscopy (NAP-XPS, PM-IRAS, concentration modulation FTIR, EXAFS) and DFT (with B. Klötzer, D. Ferri and K.M. Neyman). In  selectivity could be linked to the catalyst atomic and electronic (VB) structure, backed by DFT (JPC C 2015). Ref.  monitors the evolution of the active phase during reaction. Further studies demonstrated how well model and applied studies blended together (J. Catal. 2010/2012, JPC Lett. 2011, 2xJPC C 2012).
- Connecting model and applied catalysis of ZrO2-based reforming catalysts by in situ (synchrotron) NAP-XPS and XAS spectroscopy, employing ultrathin (trilayer) ZrO2 films as well as nanopowders of ZrO2 and ZrO2/CeO2 (JPC C 2015). Ref.  highlights the importance of realistic gas pressures, as only the hydroxylated surface activated CO2. 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 (Top. Catal. 2016, Catal. Tod. 2016/2017).
- 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, as discussed in Ref. . The presumably active (oxygen vacancy) sites were a minority species. Further studies contrasted Co3O4 to Co3O4/CeO2 (J. Cat. 2016, Chem. Europ. J. 2021) and CoO (Cat. Tod. 2019).
- Combining experimental Pd single crystal studies of the complex 1-butene hydrogenation and isomerization with DFT calculations (with N. Rösch), not only the selectivity could be explained but it was demonstrated that isomerization proceeds different from the generally accepted Horiuti−Polanyi mechanism. The study in  was triggered by earlier ones of the even more complex 1,3-butadiene hydrogenation (J. Cat. 2005/2006, Chem. Comm. 2006).
- 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