A5087866517- Catalytic Processes in Materials Science
- Semiconductor materials and devices
- Advanced Chemical Physics Studies
- Electronic and Structural Properties of Oxides
- Molecular Junctions and Nanostructures
- Electrocatalysts for Energy Conversion
- Electron and X-Ray Spectroscopy Techniques
- Advancements in Solid Oxide Fuel Cells
- Spectroscopy and Quantum Chemical Studies
- Catalysis and Oxidation Reactions
- Semiconductor materials and interfaces
- X-ray Spectroscopy and Fluorescence Analysis
- Surface and Thin Film Phenomena
- Graphene research and applications
- Quantum Dots Synthesis And Properties
- Rare-earth and actinide compounds
- Advanced Photocatalysis Techniques
- Catalysis and Hydrodesulfurization Studies
- Electrochemical Analysis and Applications
- Catalysts for Methane Reforming
- Radioactive element chemistry and processing
- Photochemistry and Electron Transfer Studies
- Chalcogenide Semiconductor Thin Films
- CO2 Reduction Techniques and Catalysts
- ZnO doping and properties
Laboratoire de Chimie Physique - Matière et Rayonnement
2016-2025
Sorbonne Université
2016-2025
Centre National de la Recherche Scientifique
2016-2025
Synchrotron soleil
2016-2025
Sorbonne Paris Cité
2023
PHENIX laboratory
2021
Université Paris Cité
2014-2021
Pohang University of Science and Technology
2021
Pohang Accelerator Laboratory
2021
Gwangju Institute of Science and Technology
2021
A CoFe Prussian blue analogue Rb1.8Co4[Fe(CN)6]3.3·13H2O was synthesized, which presents an important photomagnetic effect. The electronic structure and the local of ground excited states have been investigated. X-ray absorption spectroscopy measurements at Co Fe L2,3 edges cobalt K-edge (XANES EXAFS) evidence transfer spin change ions induced by irradiation. We observed a 0.19 Å increase Co−N bond length, associated with transformation CoIII low to CoII high spin. CoII/CoIII ratio has...
Ultra-high purity nano-sized iridium enclosed in a monolayer of Ir<sup>III</sup>/Ir<sup>IV</sup> oxides/hydroxides leads to an enhancement OER activity.
The origin of the synergistic catalytic effect between metal catalysts and reducible oxides has been debated for decades. Clarification this effect, namely, strong metal-support interaction (SMSI), requires an understanding geometric electronic structures metal-metal oxide interfaces under operando conditions. We show that inherent lattice mismatch bimetallic materials selectively creates surface segregation subsurface atoms. Interfacial nanostructures are then formed chemical reaction...
The use of high amounts iridium in industrial proton exchange membrane water electrolyzers (PEMWE) could hinder their widespread for the decarbonization society with hydrogen. Nonthermally oxidized Ir nanoparticles supported on antimony-doped tin oxide (SnO2:Sb, ATO) aerogel allow decreasing precious metal by more than 70% while enhancing electrocatalytic activity and stability. To date, origin these benefits remains unknown. Here, we present clear evidence mechanisms that lead to...
Exsolution generates stable and catalytically active metal nanoparticles via phase precipitation out of a host oxide. An ability to control the size dispersion exsolution particles is desirable for design nanostructured (electro)catalysts. Here, we demonstrate that tuning point defects by lattice strain affects both thermodynamics kinetics iron (Fe0) on La0.6Sr0.4FeO3 (LSF) thin film model. By combining in situ surface characterization ab initio defect modeling, show oxygen vacancy Schottky...
Abstract CO 2 hydrogenation to methane is gaining increasing interest as one of the most promising ways store intermittent renewable energy in form chemical fuels. Ni particles supported on CeO represent a highly efficient, stable and inexpensive catalyst for this reaction. Herein, Ni‐doped nanoparticles were tested methanation showing an extremely high mass‐specific activity CH 4 selectivity. Operando characterization reveals that performance tightly associated with ionic Νi Ce 3+ surface...
Hydrogen production via water splitting requires efficient electrocatalysts to reduce the overpotential of anodic oxygen evolution reaction (OER) and cathodic hydrogen (HER). In this study, we investigated influence apparent shell thickness on electrocatalytic activity Fe3O4@CoFe2O4 core@shell nanoparticles, an noble metal-free OER catalyst in alkaline media. Three different types nanoparticles were synthesized by seed-mediated crystal growth cobalt ferrite pristine magnetite nanoparticles....
Graphene layers have been grown by molecular beam epitaxy (MBE) on the (0001¯) C-face of SiC and characterized atomic force microscopy, low energy electron diffraction (LEED), UV photoelectron spectroscopy. Contrary to graphitization process, step-terrace structure is fully preserved during MBE growth. LEED patterns show multiple orientation domains which are characteristic graphene (0001¯), indicating non-Bernal rotated planes. Well-defined Dirac cones, typical single-layer graphene,...
Segregation of aliovalent dopant cations is a common degradation pathway on perovskite oxide surfaces in energy conversion and catalysis applications. Here we focus resolving quantitatively how segregation affected by oxygen chemical potential, which varies over wide range electrochemical thermochemical reactions. We employ polarization to tune the potential many orders magnitude. Altering effective causes nonstoichiometry change electrode. This then influences mechanisms underlying dopants....
Size- and shape-tailored copper (Cu) nanocrystals can offer vicinal planes for facile carbon dioxide (CO2) activation. Despite extensive reactivity benchmarks, a correlation between CO2 conversion morphology structure has not yet been established at Cu interfaces. Herein, ambient pressure scanning tunneling microscopy reveals step-broken nanocluster evolutions on the Cu(997) surface under 1 mbar CO2(g). The dissociation reaction produces monoxide (CO) adsorbate atomic oxygen (O) step-edges,...
The exsolved LaNiO 3 perovskite catalyst exhibits superior performance compared to supported Ni/La 2 O attributed the critical La–Ni arrangement differences, including Ni encapsulation and lanthana's affinity for hydroxide/carbonate formation.
The introduction of atomic layer deposition (ALD), to the microelectronics industry has introduced a large number new possible materials able be deposited in layers with thickness control. One such material is high-κ oxide HfO2; thermally stable and ultrathin HfO2 films by ALD are significant contender replace SiO2 as gate capacitor applications. We present mechanistic study first cycle on Si(111) surface using tetrakis(dimethylamido) hafnium (TDMAHf) water precursors operando ambient...
The atomic layer deposition (ALD) of TiO2 on a RuO2(110) surface from tetrakis(dimethylamido) titanium and water at 110 °C was investigated using near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) precursor pressures up to 0.1 mbar. In addition the expected cyclic species, evidence for side reactions found. Dimethylamine adsorbs during TDMAT half-cycle, second likely methyl methylenimine, also forms. removal amide ligand formation an alkyammonium species half-cycle were found...
Metal borides have mostly been studied as bulk materials. The nanoscale provides new opportunities to investigate the properties of these materials, e.g., hardening and surface reactivity. are often considered stable solids because their covalent character, but little is known on behavior under a reactive atmosphere, especially reductive gases. We use molten salt synthesis at 750 °C provide cobalt monoboride (CoB) nanocrystals embedded in an amorphous layer cobalt(II) partially oxidized...
A Keggin-type POM is attached to gold or glassy carbon surfaces by electro(chemical) peptidic coupling. In addition demonstrating the robust attachment of POMs (by electrochemistry, XPS, and IRRAS), surface concentration, layer thickness, rate constant for electron transfer from have been measured. The use such complementary techniques mandatory characterize modified electrodes properly. Whatever grafting method, experimental conditions are found allow monolayer submonolayer coverage....
The identification of the active sites in heterogeneous catalysis is important for a mechanistic understanding structure–reactivity relationship. Among others, oxide/metal boundaries are expected to contain various catalytic reactions. To reveal their nature and chemical evolution under reaction conditions, role an system consisting well-ordered ZnO nanoislands grown on Pt(111) low-temperature CO oxidation was studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS)...
Using the nascent band theory of solids, Cabrera and Mott designed in late 1940s a model for low-temperature oxidation metals that still stands today as landmark. The core assumption is an electric field set up growing oxide at thermodynamic equilibrium drives transport ionic species responsible process. existence electrostatic potential has long been sought experimentally by situ measurement work function changes presence gaseous O2. Here, we demonstrate insufficient to test model. Instead,...
The surface chemistry of the initial growth during first or few precursor cycles in atomic layer deposition is decisive for how proceeds later on and thus quality thin films grown. Yet, although general schemes have been developed many processes precursors, cases, knowledge this remains far from complete. For particular case HfO2 a SiO2 an alkylamido-hafnium water, we address lack by carrying out operando experiment cycle deposition. Ambient-pressure X-ray photoelectron spectroscopy density...
We investigated the reactivity of layered GeAs in presence oxygen or water using synchrotron-based X-ray photoelectron spectroscopy and ab initio calculations. By performing experiments at near-ambient pressure (up to 20 mbar), we gained detailed insights into material's stability under realistic conditions. showed limited with dry O2 deaerated H2O. However, a small amount humidity (Rw = 0.5% T °C) an atmosphere significantly enhanced reactivity. This synergistic effect was well captured by...
Using synchrotron radiation Near-Ambient Pressure X-ray photoemission spectroscopy (NAP-XPS) in surface and bulk sensitive conditions, we specifically explored the depth distribution of Na+ ions near vapor/liquid interface saturated solutions sodium halides (NaCl, NaBr, NaI) kept at 278 K under a pressure 8 mbar. By varying photoelectron kinetic energy, hence probing depth, show that is highly to size polarizability anion. The large polarizable anions, Br– I– segregate surface, tend drag...
Complexes of cobalt(II) stabilized by lacunary polyoxometalates (CoPOMs) are highly discussed water oxidation catalysts (WOC). While their activity and stability in the oxygen evolution reaction (OER) have been widely explored, there is still no consensus between those claiming that CoPOMs active stable OER suggesting they rather act as precatalysts, which degrade into OER-active heterogeneous CoOx catalysts. In this work, we use operando X-ray absorption spectroscopy along with...
Gold and silver are miscible over the entire composition range, form an attractive combination for fundamental studies on bimetallic catalysts. Au-Ag catalysts have shown synergistic effects different oxidation liquid-phase hydrogenation reactions, but rarely been studied gas-phase hydrogenation. In this study 3 nm particles of Au, Ag supported silica (SBA-15) were investigated as selective butadiene in excess propene. The Au catalyst was order magnitude more active than at 120 °C. initial...
The investigation of nanocatalysts under ambient pressure by X-ray photoelectron spectroscopy gives access to a wealth information on their chemical state reaction conditions. Considering the paradigmatic CO oxidation reaction, strong synergistic effect catalytic was recently observed partly dewetted ZnO(0001)/Pt(111) single crystal surface. In order bridge material gap, we have examined whether this inverse metal/oxide could be transposed supported ZnPt deposited rutile TiO2(110)....