A5071823705- Iron oxide chemistry and applications
- Catalytic Processes in Materials Science
- Electrocatalysts for Energy Conversion
- Catalysis and Oxidation Reactions
- Nanomaterials for catalytic reactions
- Copper-based nanomaterials and applications
- Mine drainage and remediation techniques
- Electronic and Structural Properties of Oxides
- Advanced X-ray Imaging Techniques
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Minerals Flotation and Separation Techniques
- Catalysts for Methane Reforming
- Surface and Thin Film Phenomena
- Iron Metabolism and Disorders
- Radioactive element chemistry and processing
- Electrochemical Analysis and Applications
- Magnetic Properties and Synthesis of Ferrites
- Advanced Condensed Matter Physics
- Advanced Materials Characterization Techniques
- Digital Image Processing Techniques
- X-ray Diffraction in Crystallography
- Superconducting and THz Device Technology
- Force Microscopy Techniques and Applications
- Medical Image Segmentation Techniques
TU Wien
2017-2025
Technical University of Munich
2024-2025
University of Vienna
2020
University of Applied Sciences Technikum Wien
2013
Understanding how the local environment of a "single-atom" catalyst affects stability and reactivity remains challenge. We present an in-depth study copper1, silver1, gold1, nickel1, palladium1, platinum1, rhodium1, iridium1 species on Fe3O4(001), model support in which all metals occupy same twofold-coordinated adsorption site upon deposition at room temperature. Surface science techniques revealed that CO strength single metal sites differs from respective surfaces supported clusters....
The α-Fe2O3(11̅02) surface (also known as the hematite r-cut or (012) surface) was studied using low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), ultraviolet (UPS), scanning tunneling microscopy (STM), noncontact atomic force (nc-AFM), and ab initio density functional theory (DFT)+U calculations. Two structures are stable under ultrahigh vacuum (UHV) conditions; a stoichiometric (1 × 1) can be prepared by annealing at 450 °C in ≈10–6 mbar O2, reduced (2...
Low-energy electron diffraction (LEED) is a widely used technique in surface-science laboratories. Yet, it rarely to its full potential. The quantitative information about the surface structure, contained modulation of intensities diffracted beams as function incident energy, LEED <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>I</a:mi><a:mo>(</a:mo><a:mi>V</a:mi><a:mo>)</a:mo></a:mrow></a:math>, underutilized. To acquire these data, only minor adjustments would be...
As part of the Vienna package for Erlangen LEED, low-energy electron diffraction (ViPErLEED) project, computer programs have been developed facile and user-friendly data extraction from movies LEED images. The make use some concepts astronomical image processing analysis. a first step, flat-field dark-frame corrections reduce effects inhomogeneities camera screen. In second identifying all maxima (“spots”), it is sufficient to manually mark label single spot or very few spots. Then program...
A Gaussian Approximation Potential (GAP) was trained using density-functional theory data to enable a global geometry optimization of low-index rutile IrO2 facets through simulated annealing. Ab initio thermodynamics identifies (101) and (111) (1x1)-terminations competitive with (110) in reducing environments. Experiments on single crystals find that dominate, exhibit the theoretically predicted (1x1) periodicity X-ray photoelectron spectroscopy (XPS) core level shifts. The obtained...
Abstract Single‐atom catalysts (SACs) bridge homo‐ and heterogeneous catalysis because the active site is a metal atom coordinated to surface ligands. The local binding environment of should thus strongly influence how reactants adsorb. Now, atomically resolved scanning‐probe microscopy, X‐ray photoelectron spectroscopy, temperature‐programmed desorption, DFT are used study CO binds at different Ir 1 sites on precisely defined Fe 3 O 4 (001) support. two‐ five‐fold‐coordinated adatoms bind...
Heterogeneous catalysts based on subnanometer metal clusters often exhibit strongly size-dependent properties, and the addition or removal of a single atom can make all difference. Identifying most active species deciphering reaction mechanism is extremely difficult, however, because it not clear how catalyst evolves in operando. Here, we use combination atomically resolved scanning probe microscopies, spectroscopic techniques, density functional theory (DFT)–based calculations to study CO...
Earth-abundant oxides are promising candidates as effective and low-cost catalysts for the oxygen evolution reaction (OER) in alkaline media, which remains one of bottlenecks electrolysis artificial photosynthesis. A fundamental understanding atomic-scale mechanism during OER could drive further progress, but a stable model system has yet to be provided. Here we show that Fe3O4 single crystal surfaces, prepared ultrahigh vacuum (UHV) electrolytein range pH 7–14 under conditions 1 M NaOH....
The oxygen evolution reaction (OER) is thought to occur via a four-step mechanism with *O, *OH, and *OOH as adsorbed intermediates. Linear scaling of the *OH **OOH adsorption energies proposed limit oxides' efficiency OER catalysts, but use simple descriptors screen candidate materials neglects potentially important water–water interactions. Here, we combination temperature-programmed desorption (TPD), X-ray photoemission spectroscopy (XPS), noncontact atomic force microscopy (nc-AFM),...
The structure of a catalyst often changes in reactive environments, and following the structural evolution is crucial for identification catalyst's active phase reaction mechanism. Here we present an atomic-scale study CO oxidation on model Rh/Fe3O4(001) "single-atom" catalyst, which has very different depending two reactants, O2 or CO, adsorbed first. Using temperature-programmed desorption (TPD) combined with scanning tunneling microscopy (STM) X-ray photoelectron spectroscopy (XPS), show...
Oxide-supported single-atom catalysts are commonly modeled as a metal atom substituting surface cation sites in low-index surface. Adatoms with dangling bonds will inevitably coordinate molecules from the gas phase, and adsorbates such water can affect both stability catalytic activity. Herein, we use scanning tunneling microscopy (STM), noncontact atomic force (ncAFM), X-ray photoelectron spectroscopy (XPS) to show that high densities of single Rh adatoms stabilized on α-Fe2O3(11̅02)...
Low-energy electron diffraction (LEED) is a widely used technique in surface-science. Yet, it rarely to its full potential. The quantitative information about the surface structure, contained modulation of intensities diffracted beams as function incident energy, LEED I(V), underutilized. To acquire these data, minor adjustments would be required most experimental setups, but existing analysis software cumbersome use. ViPErLEED (Vienna package for Erlangen LEED) lowers barriers, introducing...
Electrochemical water splitting is an environmentally friendly technology to store renewable energy in the form of chemical fuels. Among earth-abundant first-row transition metal-based catalysts, mixed Ni-Fe oxides have shown promising performance for effective and low-cost catalysis oxygen evolution reaction (OER) alkaline media, but synergistic roles Fe Ni cations OER mechanism remain unclear. In this work, we report how addition changes reactivity a model iron oxide catalyst, based on...
Abstract Hematite is a common iron oxide found in nature, and the α ‐Fe 2 O 3 (0001) plane prevalent on nanomaterial utilized photo‐ electrocatalytic applications. The atomic‐scale structure of surface remains controversial despite decades study, partly because it depends sample history as well preparation conditions. Here, comprehensive study performed using an arsenal techniques (non‐contact atomic force microscopy, scanning tunneling low‐energy electron diffraction, X‐ray photoemission...
Abstract Iron oxides (FeO x ) are among the most common support materials utilized in single atom catalysis. The is nominally Fe 2 O 3 , but strongly reductive treatments usually applied to activate as‐synthesized catalyst prior use. Here, Rh adsorption and incorporation on () surface of hematite (α‐Fe studied, which switches from a stoichiometric (1 × 1) termination reduced (2 reconstruction reducing conditions. atoms form clusters at room temperature both terminations, incorporate into...
Atomic-scale investigations of metal oxide surfaces exposed to aqueous environments are vital understand degradation phenomena (e.g. dissolution and corrosion) as well the performance these materials in applications. Here, we utilize a new experimental setup for UHV-compatible dosing liquids explore stability Fe3O4(001)-c(2x2) surface following exposure liquid ambient pressure water. X-ray photoelectron spectroscopy (XPS) low energy electron diffraction (LEED) data show that extensive...
Ultrathin two-dimensional silica films have been suggested as highly defined conductive models for fundamental studies on silica-supported catalyst particles. Key requirements in this context are closed that isolate the gas phase from underlying metal substrate and stability under reaction conditions. Here, we present bilayer grown Pt(111) Rh(111) characterize them by scanning tunneling microscopy X-ray photoelectron spectroscopy. We provide first report of further successfully prepared...
Determining the local coordination of active site is a prerequisite for reliable modeling single-atom catalysts (SACs). Obtaining such information difficult on powder-based systems and much emphasis placed density functional theory computations based idealized low-index surfaces support. In this work, we investigate how Pt atoms bind to (11̅02) facet α-Fe
In polarizable materials, electronic charge carriers interact with the surrounding ions, leading to quasiparticle behavior. The resulting polarons play a central role in many materials properties including electrical transport, interaction light, surface reactivity, and magnetoresistance, are typically investigated indirectly through these macroscopic characteristics. Here, noncontact atomic force microscopy (nc-AFM) is used directly image Fe
Abstract Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology environmental studies, as it closely linked to both catalytic activity material degradation. The atomic-scale details are mostly unknown, however, often ascribed poorly defined defects the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, all 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline...
We studied how nickel doping affects water adsorption at the Fe3O4(001) surface to understand enhanced performance of spinel ferrites for water-gas shift and oxygen evolution reactions. Two different configurations were prepared: 2-fold-coordinated Ni adatoms on top atoms incorporated into octahedral sites support. Using temperature-programmed desorption, X-ray photoemission spectroscopy, scanning tunneling microscopy, we show that is adsorbed dissociated room temperature, resulting in Ni–OH...
Hematite (α-Fe2O3) is one of the most investigated anode materials for photoelectrochemical water splitting. Its efficiency improves by doping with Ti, but underlying mechanisms are not understood. One hurdle separating influence on conductivity, surface states, and morphology, which all affect performance. To address this complexity, needs well-defined model systems. We build such a system growing single-crystalline, atomically flat Ti-doped α-Fe2O3(11̅02) films pulsed laser deposition...
The (111) facet of magnetite (Fe3O4) has been studied extensively by experimental and theoretical methods, but controversy remains regarding the structure its low-energy surface terminations. Using density functional theory (DFT) computations, we demonstrate three reconstructions that are more favorable than accepted Feoct2 termination under reducing conditions. All structures change coordination iron in kagome Feoct1 layer to be tetrahedral. With atomically resolved microscopy techniques,...