Rupprechter is "Director of Research" (speaker) of the FWF-funded Cluster of Excellence[2] "Materials for Energy Conversion and Storage (COE MECS)",[3] including 19 research groups at 4 Austrian universities/institutions. The COE MECS (2023–2028, with an option of extension to 2033) is one of three COEs in the natural sciences (among five first Clusters of Excellence in Austria[2]).
Rupprechter's current research interests are primarily focused on catalytic surface reactions on heterogeneous catalysts. His research group[9] employs a four-pronged approach:
Surface-Science-Based Model Catalysts: Prof. Rupprechter's work on planar model catalysts aims to understand fundamental processes that occur on catalytic surfaces via in situ/operando surface spectroscopy and microscopy,[10] bridging both the materials and pressure gaps.[11]
Atomically Precise Clusters: He investigates atomically precise clusters to gain insights and control the behavior of catalytic materials.
Industrial-Grade Nanomaterials: His research extends to the study of industrial-grade nanomaterials, which have practical applications in catalytic processes.
Microkinetic Modeling and Simulation: The interpretation and verification of experimentaloperando spectra/images/patterns typically rely on theoretical support.
Rupprechter's overarching goal is to elucidate the molecular mechanisms of reactions relevant to a clean environment, energy conversion, and efficient resource utilization. Among others, molecular mechanisms ofhydrogen as clean fuel,methane reforming, CO2 and olefinhydrogenation, efficient automotive catalysis, andwaste valorization were studied. Materials of interest include mono- (Pt, Pd, Rh, Cu, Ni, Au, Co) and bimetallic (PdZn, Pd2Ga, PdCu, CuNi, CuZn, PdAu, AgAu, CuAu, RhAu) nanoparticles on supporting (mixed) oxides (Al2O3,SiO2,CeO2,PrO2,ZrO2,TiO2,ZnO,MgO,Ga2O3,Co3O4), perovskites (LCO, LSF), andcarbon (HOPG, GR, GR-NPs).
From 2011 to 2019, Rupprechter served as the Speaker/Coordinator of the FWF-funded Special Research Program (SFB) "Functional Oxide Surfaces and Interfaces (FOXSI),[12]" involving 150 researchers in 10 research groups. He directed theTU Wien funded Doctorate school "Catalysis Materials and Technology" with 11 research groups from 2011 to 2014.
Since Oct. 1st, 2023, Prof. Rupprechter holds the position of "Director of Research" of the FWF-funded Cluster of Excellence "Materials for Energy Conversion and Storage (MECS)."[3][2]
Prof. Rupprechter has/had several leadership roles in professional societies such as theAustrian Chemical Society (GÖCH) and the Chemical Physical Society.[13] He is Vicechair of the Austrian Catalysis Society, thus Austrian Representative in the European Federation of Catalysis Societies (EFCATS)[14] and the International Association of Catalysis Societies (IACS).[15] He has been Austrian Representative in variousEuropean COST Actions:[16] CA22123 - European Materials Acceleration Center for Energy (EU-MACE; Management Committee);[17] MP0903 - Nanoalloys as advanced materials: from structure to properties and applications (NANOALLOY; Management Committee);[18] CM0904 - Network for intermetallic compounds as catalysts forsteam reforming of methanol (IMC-SRM; Vice Chair, Management Committee; STSM Coordinator);[19] 540 - Photocatalytic technologies and novel nanosurfaces materials - critical issues (PHONASUM; Management Committee).[20]
Rupprechter has (co-)organized of academic conferences and summer schools, e.g. the annual "International Workshop on Chemistry and Physics of Novel Materials"[21] (with P. Blaha), the EFCATS Summer School "Engineering Materials for Catalysis 2020" (with Albin Pintar and Nataša Novak Tušar: Portorož-Portorose,Slovenia), theFaraday Discussion on "Photoelectron Spectroscopy: New Horizons in Surface Analysis",London,UK (2022), the "GÖCh-Symposium - Physikalische Chemie und Elektrochemie in Österreich 2023"[22] and the upcoming 16th Pannonian International Symposium on Catalysis (Seggau/Styria, Austria; September 1–5, 2024; with C. Rameshan).[23]
Rupprechter has received several awards and honors including:
Jochen Block Award of the German Catalysis Society (DECHEMA) in 2005 for his contributions to applying surface science methods to heterogeneous catalysis.[24]
Examining functioning catalysts at nearatmospheric pressure (NAP) and realistic temperature is crucial to obtain a fundamental understanding, Rupprechter has developed dedicated UHV-compatible high-pressure cells for model catalysts (single crystals, thin films, nanoparticles), enablingsum frequency generation (SFG)laser spectroscopy, polarization-modulation infrared reflection absorption spectroscopy (PM-IRAS), andX-ray photoelectron spectroscopy (NAP-XPS) under reaction conditions. For industrial-grade nanomaterials, corresponding in situ (operando) spectroscopy is carried out byFourier transform infrared spectroscopy (FTIR and DRIFTS),X-ray absorption spectroscopy (XAS), NAP-XPS, andX-ray diffraction (XRD). Significant advances were made in directly imaging the local kinetics of surface reactions by in situ surface (correlative) microscopy, withphotoemission electron microscopy (PEEM), scanning photoelectron microscopy (SPEM) and field emission/ion microscopy (FEM/FIM) applied to metals and metal/oxide interfaces. Most studies were carried out atsynchrotron sources and in lock-step with theory collaborations (DFT and micro-kinetics).
Rupprechter is among the early researchers in ambient pressure surface science, developing and applying UHV-compatible high-pressure (HP) cells for combined in situ surface spectroscopy and kinetics:[11][10] sum frequency generation (SFG) withGábor A. Somorjai, SFG/PM-IRAS with Hans-Joachim Freund,[32] near atmospheric pressure- X-ray photoelectron spectroscopy (NAP-XPS) with V.I. Bukhtiyarov (J. Phys. Chem. C 2003/2004).[33][34] This enabled atmospheric pressure studies of UHV-grown model systems, creating the vital link to technological catalysis. Among several constructed HP cells, one specific design[35] is used by several groups worldwide.
First demonstration of SFG spectroscopy on oxide supported Pd nanoparticles, revealing size and pressure (ultra high vacuum-UHV to mbar) effects inCO adsorption.[36] This triggered many follow-up studies, also combined with NAP-XPS. His SFG activities continue till today, including single crystals, thin films, and nanoparticles.[37][38]
Combining atmospheric pressure reaction kinetics of the complex1-butene hydrogenation andisomerization on Pd single crystals and Pd/Al2O3 model catalysts withdensity functional theory (DFT) calculations and microkinetic modeling (with A. Genest and N. Rösch), the particle size-dependent selectivity could be rationalized based on the abundance and specific properties of the contributing nanoparticle facets.[39][40]
Molecular-level operando insights into selective methanol steam reforming on PdZn and PdGa intermetallics (NAP-XPS, PM-IRAS, concentration modulation IR, EXAFS, DFT; with B. Klötzer, D. Ferri, K.M. Neyman). He was able to link reaction selectivity to the catalyst's atomic and electronic (VB) structure, backed by DFT (JPC C 2015). Model and applied studies blended well together.
Studies 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 nano powders ofZrO2 and ZrO2/CeO2 (Catal. Tod. 2016/2017). Further studies of methane dry reforming demonstrated SMSI effects (J. Phys. Cond. Matt. 2018), Ni surface segregation in bimetallic CuNi/ZrO2, and coke suppression for Ni/ZrO2/CeO2.[10]
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.[10][41] The presumably active (oxygen vacancy) sites were a minority species. Further studies contrasted Co3O4 to Co3O4/CeO2 and CoO (J. Phys.: Cond. Matt. 2022, Chem. Europ. J. 2021, Catal. Tod. 2019).
Surface chemistry of Au clusters on ceria-praseodymium mixed oxide supports: Au/Ce4Pr1Ox exhibited the highest activity in water gas shift, with combined experimental and theoretical studies showing that asymmetric O vacancies facilitate H2O dissociation.[42] Using thiolate-protected atomically preciseAu clusters on various supports as truly monodisperse catalysts.[43]
Waste-valorized synthesis and application of methanol sensors,[44] self-cleaning paint[45][46][47] and nanowebs for water purification.[48]
Locally resolved imaging of ongoing surface reactions byphotoemission electron microscopy (PEEM), directly revealing phenomena such as facet-resolved catalytic ignition, multi-frequential oscillations, anisotropic surface oxidation, coexisting multi-states, and long-ranging metal/oxide interface effects (with Y. Suchorski).[10][49][50] This opened a new pathway to investigate catalyst heterogeneity and structure sensitivity,[51] 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 K.M. Neyman and H. Grönbeck) yielded fundamental insights on interface activity.[49][52] PEEM was combined with SPEM (Scanning Photoelectron Microscopy)[50] and recently extended to XPEEM and LEEM (low energy electron microscopy) in a true in situ correlative microscopy approach.[53][54]
Fieldelectron microscopy (FEM) is applied to image an ongoing catalytic reaction on the facets of an individual metal nanocrystal in real time, enabling, e.g., to resolve interfacet coupling and its collapse due to surface restructuring.[55][56][57] When the produced water was used as imaging species, the active sites were directly identified by in situfield ion microscopy (FIM). First observation of nano-chaos in a catalytic reaction[58] and direct imaging of La-induced promotor effects.[59][60]
^Rupprechter, G.; Dellwig, T.; Unterhalt, H.; Freund, H.-J. (2001-01-01). "CO adsorption on Ni(100) and Pt(111) studied by infrared–visible sum frequency generation spectroscopy: design and application of an SFG-compatible UHV–high-pressure reaction cell".Topics in Catalysis.15 (1):19–26.doi:10.1023/A:1009063611629.ISSN1572-9028.S2CID56468057.
