A5024001888- Catalytic Processes in Materials Science
- Electrocatalysts for Energy Conversion
- Catalysis and Oxidation Reactions
- Surface and Thin Film Phenomena
- Copper-based nanomaterials and applications
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Fullerene Chemistry and Applications
- Semiconductor Quantum Structures and Devices
- Graphene research and applications
- Semiconductor materials and interfaces
- nanoparticles nucleation surface interactions
- Electrochemical Analysis and Applications
- Machine Learning in Materials Science
- Molecular Junctions and Nanostructures
- Advanced Materials Characterization Techniques
- Theoretical and Computational Physics
- Photonic and Optical Devices
- Nanomaterials for catalytic reactions
- Force Microscopy Techniques and Applications
- ZnO doping and properties
- Fuel Cells and Related Materials
- Catalysis and Hydrodesulfurization Studies
- Chemical and Physical Properties of Materials
Charles University
2015-2025
Istituto Officina dei Materiali
2012
Elettra-Sincrotrone Trieste S.C.p.A.
2012
Forschungszentrum Jülich
2002-2010
Johannes Kepler University of Linz
2002-2006
Abstract Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, atoms are stabilized specific adsorption sites on catalyst substrates. Here we show combining photoelectron spectroscopy, scanning tunnelling microscopy density functional theory calculations that Pt ceria most ubiquitous defects solid surfaces—monoatomic step edges. segregation steps leads...
Platinum is the most versatile element in catalysis, but it rare and its high price limits large-scale applications, for example fuel-cell technology. Still, conventional catalysts use only a small fraction of Pt content, that is, those atoms located at catalyst's surface. To maximize noble-metal efficiency, precious metal should be atomically dispersed exclusively within outermost surface layer material. Such species can indeed prepared with exceptionally stability. Using DFT calculations...
On the graphene moire on Ir(111) a variety of highly perfect cluster superlattices can be grown as shown is for Ir, Pt, W, and Re. Even materials that do not form upon room temperature deposition may into such by low or application seeding through Ir Au, AuIr, FeIr. Criteria suitability material to superlattice are given largely confirmed. It proven at least Pt even epitaxial superlattices. The stability investigated understood basis positional fluctuations clusters around their sites...
Thin films of reduced ceria supported on metals are often applied as substrates in model studies the chemical reactivity based catalysts. Of special interest properties oxygen vacancies ceria. However, thin prepared by established methods become increasingly disordered concentration increases. Here, we propose an alternative method for preparing ordered physical vapor deposition and interfacial reaction Ce with CeO2 films. The yields bulk-truncated layers cubic c-Ce2O3. Compared to these...
Adjustable morphology and degree of reduction represent desirable properties model oxide substrates for heterogeneous catalysis. We investigate these in CeO2 (ceria) thin films on Cu(111) using scanning tunneling microscopy photoelectron spectroscopy. identify growth mechanisms ceria Cu(111): formation incomplete interfacial layer three-dimensional pyramids by stacking monolayer-high islands. Using mechanisms, we control the coverage, number open monolayers, step density Cu(111). Annealing...
Changes of stoichiometry in reducible oxides are inevitably accompanied by changes the oxide structure. We study relationship between and structure thin epitaxial films reduced ceria, CeOx, 1.5 ≤ x 2, prepared via an interface reaction a ceria film on Cu(111) Ce metal deposit. show that transition limiting stoichiometries CeO2 Ce2O3 is realized equilibration mobile oxygen vacancies near surface film, while fluorite lattice cerium atoms remains unchanged during process. identify two...
Reactions of reduced cerium oxide CeOx with water are fundamental processes omnipresent in ceria-based catalysis. Using thin epitaxial films ordered CeOx, we investigate the influence oxygen vacancy concentration and coordination on oxidation by water. Upon changing stoichiometry from CeO2 to Ce2O3, observe a transition slow surface reaction productive H2-evolving yields exceeding capacity indicating participation bulk OH species. Both experiments ab initio calculations associate effective...
Single-atom catalysts represent an essential and ever-growing family of heterogeneous catalysts. Recent studies indicate that besides the valuable catalytic properties provided by single-atom active sites, presence sites on catalyst substrates may significantly influence population supported metal nanoparticles coexisting with single atoms. Treatment ceria-based in oxidizing or reducing atmospheres was proven to provide a precise experimental control size Pt and, correspondingly, activity...
We use variable temperature scanning tunneling spectroscopy to determine the space and energy structure of adatom electron band $\mathrm{Si}(111)\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$ surface. At low $(7\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ we map wave functions electrons in real space. observe a pronounced splitting states between corner center adatoms surface reconstruction identify new spectral features unoccupied part band. The are subsequently identified spectra at...
Discontinuous ceria layers on Cu(111) represent heterogeneous catalysts with notable activities in water–gas shift and CO oxidation reactions. Ultrathin islands these are composed of monolayers exhibiting CeO2(111) surface ordering bulklike vertical stacking (O–Ce–O) down to a single monolayer representing the oxide-metal interface. Scanning tunneling microscopy (STM) reveals marked differences strain buildup structure oxygen vacancies this first compared thicker Cu(111). Ab-initio...
Abstract Platin ist das am vielseitigsten eingesetzte Element in der Katalyse. Allerdings begrenzt hohe Preis des Edelmetalls die Verwendung vielen Bereichen, z. B. Katalysatormaterialien für Brennstoffzellen. Trotzdem nutzen konventionelle Katalysatoren oftmals nur einen Bruchteil ihres Pt‐Gehaltes, nämlich diejenigen Atome, sich auf Oberfläche Katalysators befinden. Eine effizientere Edelmetallnutzung setzt somit eine höhere, bevorzugt atomare Dispersion Pt‐Atome voraus. Tatsächlich es...
Oxide supports can modify and stabilize platinum nanoparticles (NPs) in electrocatalytic materials. We studied related phenomena on model systems consisting of Pt NPs atomically defined Co3O4(111) thin films. Chemical states dissolution behavior catalysts were investigated as a function the particle size electrochemical potential by ex situ emersion synchrotron radiation photoelectron spectroscopy online inductively coupled plasma mass spectrometry. Electronic metal–support interaction...
The stabilities of monometallic Rh and Pd nanoparticles bimetallic Pd–Rh core–shell supported on Co 3 O 4 (111) thin films grown Ir(100) were investigated with respect to the oxidation state and...
The population of Ag-occupied half-unit cells (HUC's) on $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface resulting from growth and annealing experiments is observed by scanning tunneling microscopy. temperature dependence Ag-object density preference in HUC occupation are measured. results interpreted with the help a coarse-grained kinetic Monte Carlo model. key mechanisms affecting Ag motion determined, particular transient mobility deposited atoms existence highly stable...
The interaction of Pt with layers was investigated using photoelectron spectroscopy. Pt-doped 30 nm thick were deposited by radio-frequency (rf) magnetron sputtering a composite target on carbon diffusion layer micropolymer membrane fuel cell covered double-wall nanotubes. laboratory X-ray spectroscopy and synchrotron radiation soft photoemission spectra showed the formation cerium oxide completely ionized species embedded in film. A small amount is present film surface only. Hydrogen/air...
Smallest metallic (blue) and ionic (grey) Pt objects on ceria are shaped controlled by surface oxygen content.
Iridium-based materials are among the most active bifunctional catalysts in heterogeneous catalysis and electrocatalysis. We have investigated properties of atomically defined Ir/CeO2(111) model systems supported on Cu(111) Ru(0001) by means synchrotron radiation photoelectron spectroscopy, resonant photoemission near ambient pressure X-ray spectroscopy (NAP XPS), scanning tunneling microscopy, temperature programmed desorption. Electronic metal-support interactions system accompanied charge...
The formation of the metal–oxide interface in Pd/Co3O4(111) model catalyst was investigated by means density functional theory (DFT), synchrotron radiation photoelectron spectroscopy (SRPES), and scanning tunneling microscopy (STM). electronic metal–support interaction results a substantial charge transfer at yielding atomically dispersed Pd2+ species partially oxidized Pdδ+ aggregates coupled with partial reduction Co3O4(111). Atomically fcc site on Co3O4(111) surface were found to be most...
We demonstrate the ability of a double-tip scanning tunneling microscope (STM) combined with electron (SEM) to perform charge transport measurements on nanoscale. The STM tips serve as electric probes that can be precisely positioned relative surface nanostructures using SEM control and height reference provided by contact. work in contact, noncontact, modes. present vertical nanosized GaAs/AlAs resonant diodes lateral conductive 7×7 reconstructed Si(111). high stability allows...
We use scanning tunneling microscopy to establish controlled contacts single molecules of endohedrally doped Ce2@C80 fullerenes with C60 as a reference. The stability the experimental setup allows for determination conductance relative C60. endohedral doping reduces by factor about five respect Ab initio calculations show that reason this reduced is absence electron orbitals delocalized over cage in energy window measurement.