A5050650768- Catalytic Processes in Materials Science
- Electrocatalysts for Energy Conversion
- Advanced Chemical Physics Studies
- Advanced Photocatalysis Techniques
- Catalysis and Oxidation Reactions
- Copper-based nanomaterials and applications
- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Electron and X-Ray Spectroscopy Techniques
- nanoparticles nucleation surface interactions
- Semiconductor materials and devices
- CO2 Reduction Techniques and Catalysts
- Transition Metal Oxide Nanomaterials
- Advanced battery technologies research
- Electrochemical Analysis and Applications
- Advanced Materials Characterization Techniques
- Gas Sensing Nanomaterials and Sensors
- Supercapacitor Materials and Fabrication
- Mesoporous Materials and Catalysis
- Advancements in Battery Materials
- Fuel Cells and Related Materials
- Surface and Thin Film Phenomena
- X-ray Spectroscopy and Fluorescence Analysis
- Perovskite Materials and Applications
- ZnO doping and properties
Koç University
2014-2024
Orient-Institut Istanbul
2018
MSSCORPS (Taiwan)
2018
SLAC National Accelerator Laboratory
2010-2016
Interface (United States)
2012-2016
Lawrence Berkeley National Laboratory
2014-2015
Joint Center for Artificial Photosynthesis
2014-2015
Menlo School
2015
Berkeley College
2015
Stanford Synchrotron Radiation Lightsource
2009-2013
An iridium oxide nanoparticle electrocatalyst under oxygen evolution reaction conditions was probed in situ by ambient-pressure X-ray photoelectron spectroscopy. Under OER conditions, undergoes a change oxidation state from Ir(IV) to Ir(V) that takes place predominantly at the surface of catalyst. The chemical is coupled decrease hydroxide, providing experimental evidence which strongly suggests on occurs through an OOH-mediated deprotonation mechanism.
Femtosecond x-ray laser pulses are used to probe the carbon monoxide (CO) oxidation reaction on ruthenium (Ru) initiated by an optical pulse. On a time scale of few hundred femtoseconds, pulse excites motions CO and oxygen (O) surface, allowing reactants collide, and, with transient close picosecond (ps), new electronic states appear in O K-edge absorption spectrum. Density functional theory calculations indicate that these result from changes adsorption site bond formation between...
The structure of a thin single crystalline SiO(2) film grown on Mo(112) has been studied by scanning tunneling microscopy, infrared reflection absorption spectroscopy, and x-ray photoelectron spectroscopy. In excellent agreement with the experimental results, density functional theory calculations show that consists two-dimensional network corner sharing [SiO(4)] tetrahedra, one oxygen each tetrahedron binding to protruding Mo atoms surface.
We used the Linac Coherent Light Source free-electron x-ray laser to probe electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting substrate by using a femtosecond optical pulse. observed that are consistent with weakening interaction but without notable desorption. A large fraction (30%) was trapped in transient precursor would precede calculated free energy molecule function desorption reaction coordinate density functional theory, including van...
The oxidation of Pt(111) at near-ambient O2 pressures has been followed in situ using x-ray photoelectron spectroscopy (XPS) and ex absorption (XAS). Polarization-dependent XAS signatures the O K edge reveal significant temperature- pressure-dependent changes Pt-O interaction. Oxide growth commences via a PtO-like surface oxide that coexists with chemisorbed oxygen, while an ultrathin α-PtO2 trilayer is identified as precursor to bulk oxidation. These results have important implications for...
We report on the hydrogen adsorption induced phase transition of a few layer graphene (1 to 4 layers) diamondlike structure Pt(111) based core level x-ray spectroscopy, temperature programed desorption, infrared and density functional theory total energy calculations. The surface induces hybridization change carbon from $s{p}^{2}$ $s{p}^{3}$ bond symmetry, which propagates through layers, resulting in interlayer formation. is stabilized termination interfacial atoms by substrate. structural...
Molybdenum sulfide structures, particularly amorphous MoS3 nanoparticles, are promising materials in the search for cost-effective and scalable water-splitting catalysts. Ex situ observations show that nanoparticles exhibit a composition change from to defective MoS2 when subjected hydrogen evolution reaction (HER) conditions, raising questions regarding active surface sites taking part reaction. We tracked transformation of under HER conditions through ambient pressure X-ray photoelectron...
HIPPIE is a soft X-ray beamline on the 3 GeV electron storage ring of MAX IV Laboratory, equipped with novel ambient-pressure photoelectron spectroscopy (APXPS) instrument. The endstation dedicated to performing in situ and operando experiments presence controlled gaseous atmosphere at pressures up 30 mbar [1 = 100 Pa] as well under ultra-high-vacuum conditions. photon energy range 250 2200 eV planar polarization fluxes >10 12 photons s −1 (500 mA current) resolving power greater than...
Developing active, durable, and inexpensive electrocatalysts is critical for hydrogen production to meet ever-growing sustainable energy needs. Nickel sulfides offer significant potential as a evolution reaction (HER); however, the active phase governing electrochemical conversion still under debate. We show that mesoporous thin-film NiS2 synthesized by novel soft-templating method without post-sulfurization exhibits superior HER activity in alkaline media after preconditioning step results...
The interaction of water with the Fe3O4(001) surface was investigated in a combined ambient pressure X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) study. uptake molecular hydroxyl species on (001) natural magnetite sample at near-ambient conditions quantified using O 1s spectra taken p(H2O) range from 10–9 to 2 Torr. At low (≤10–4–10–5 Torr) room temperature, we found that does not adsorb dissociatively surface, except defect sites. In contrast, progressive...
Abstract An iridium oxide nanoparticle electrocatalyst under oxygen evolution reaction conditions was probed in situ by ambient‐pressure X‐ray photoelectron spectroscopy. Under OER conditions, undergoes a change oxidation state from Ir IV to V that takes place predominantly at the surface of catalyst. The chemical is coupled decrease hydroxide, providing experimental evidence which strongly suggests on occurs through an OOH‐mediated deprotonation mechanism.
We have used X-ray photoelectron spectroscopy and polarization-resolved O K-edge absorption to investigate the reactivity of various oxygen covered Pt(111) surfaces, which emerge under high temperature pressure conditions, toward CO. find that O/Pt(111) system decreases monotonically with increasing coverage. Of three surface phases, viz., chemisorbed (O(ad)), a PtO-like oxide, α-PtO2 trilayers, Oad exhibits highest CO, whereas trilayers exhibit lowest. surfaces fully terminated by are inert...
The effect of crystal growth conditions on the O K-edge x-ray absorption spectra ice is investigated through detailed analysis spectral features. amount defects found to be minimized hydrophobic surfaces, such as BaF2(111), with low concentration nucleation centers. This manifested a reduction cross-section at 535 eV, which associated distorted hydrogen bonds. Furthermore, connection made between observed increase in intensity 544 and 548 eV high-symmetry points electronic band structure,...
On the BiVO 4 photoanode surface, oxygen vacancies modified by cobalt incorporation have a remarkable impact on water oxidation activity and charge injection efficiency.
The electrochemical CO
The atomic manipulation of the low-coordination sites metal catalysts can give rise to activity enhancement; however, it is rather challenging locally probe dynamic changes and activities these sites. Herein, step-edge/terrace site decoration exchange Pt atoms with a stepped Cu(211) surface were investigated by combination infrared reflection absorption spectroscopy (IRRAS) temperature-programmed desorption (TPD) carbon monoxide (CO). For low coverage Pt, step Cu found be two pathways...
We have investigated the reaction of water vapor with MgO(100) surface using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), which permits study chemical composition MgO/water interface at p(H2O) in Torr range. Water dissociation on thin films 4–5.5 monolayers (ML) grown Ag(100) was studied under isobaric conditions ranging from 0.005 to 0.5 and temperatures 380 −10 °C, up a maximum relative humidity (RH) 20%. At RH < 0.01% dissociative adsorption occurs only defect sites (∼0.08...
Size-selected 9 nm PtxY nanoparticles have recently shown an outstanding catalytic activity for the oxygen reduction reaction, representing a promising cathode catalyst proton exchange membrane fuel cells (PEMFCs). Studying their electrochemical dealloying is fundamental step towards understanding of both and stability. Herein, size-selected been deposited on side PEMFC specifically designed in situ ambient pressure X-ray photoelectron spectroscopy (APXPS). The mechanism was followed first...
We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in occupied and unoccupied electronic structure using ultrafast soft x-ray absorption emission. recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] phonon-mediated transition into weakly precursor state occurring time scale $>2\text{ }\text{ }\mathrm{ps}$ prior to desorption. Here we focus processes within first picosecond after show that...
Electrodeposited and thermally oxidized copper based electrodes to produce higher alcohols.