Research Project: Yapısal Gerinim Ve Komresyon Kaynaklı Geometrik Etkilerin Ve Ligand Etkisinin Platinin Katalitik Aktivitesindeki Rolü
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Contributors
Funders
ID
TB.00413
Authors
Kaya, Sarp
Faculty Member
Publications
Step-edge decoration and clustering of Pt atoms on a Cu(211) stepped surface
(American Chemical Society, 2024) Kaya, Sarp; Mohammadpour, Amin; Department of Chemistry; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Sciences; Research Center
The atomic manipulation of the low-coordination sites of metal catalysts can give rise to activity enhancement;however, it is rather challenging to locally probe the dynamic changes and activities of these sites. Herein, step-edge/terrace site decoration and site exchange of Pt atoms with a stepped Cu(211) surface were investigated by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) of carbon monoxide (CO). For a low coverage of Pt, step decoration and site exchange with Cu were found to be two pathways to isolate Pt as single atoms. CO preferentially adsorbs near the Cu step sites on the lower terrace, and the binding energies of CO show strong Pt coverage dependence. The presence of Pt on terrace and step sites modifies the binding energy of CO absorbed on Cu in the proximity. Increased Pt-Pt lateral coordination changes the site preference;however, the reduced binding energy of CO to Pt is attributed to heteroatom bond formation rather than the strain induced by the lattice mismatch.
Using Auger transitions as a route to determine the oxidation state of copper in high-pressure electron spectroscopy
(Elsevier, 2024) Kaya, Sarp; Soldemo, Markus; Garcia-Martinez, Fernando; Goodwin, Christopher M.; Loemker, Patrick; Shipilin, Mikhail; Nilsson, Anders; Amann, Peter; Weissenrieder, Jonas; Department of Chemistry; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Sciences; Research Center
Accurate discrimination between metallic copper (Cu0) and cuprous oxide (Cu2O, Cu+) in electron spectroscopy commonly relies on the Auger electron spectroscopy (AES) Cu L3M4,5M4,5 transitions, as the X-ray photoelectron spectroscopy (XPS) Cu core-levels do not provide large enough binding energy shifts. The kinetic energy of the AES Cu L3M4,5M4,5 electrons is 917 eV, which leaves the AES electron susceptible for efficient scattering in the gas phase and attenuation of the signal above near-ambient pressure conditions. To study copper-based materials at higher pressures, e.g., the active state of a catalyst, Auger transitions providing electrons with higher kinetic energies are needed. This study focuses on AES transitions involving the Cu K-shell (1s electrons) that exhibit discernible kinetic energy shifts between the oxidation states of Cu. It is shown that the AES Cu KL2M4,5 transition, with kinetic energy of 7936 eV, provides a large enough kinetic energy shift between metallic copper and Cu2O. AES signal is demonstrated in an ambient of 150 mbar CO2.
Probing water adsorption characteristics of Pt step-edge decorated CU (211) surface
(Elsevier, 2024) Kaya, Sarp; Mohammadpour, Amin; Department of Chemistry; KUTEM (Koç University Tüpraş Energy Center); Yes; College of Sciences; Research Center
The surface structure and atomic composition can affect the adsorption characteristics of water on metal surfaces. In this study, we investigated the adsorption of water on Cu(211) stepped surfaces decorated with Pt by a combination of infrared reflection absorption spectroscopy (IRRAS) and temperature -programmed desorption (TPD) studies. We have observed that step sites of Cu can increase the strength of the binding of water molecules to the surface and facilitate water partial dissociation and the formation of OH groups on the surface. Step decoration by Pt can change the water adsorption characteristics and eliminate the water dissociation. Water adsorbs molecularly on the fully Pt -decorated steps of the Cu(211) surface. Molecular water and OH adsorbed on Cu(211), which can make a chain structure, are disrupted with Pt atoms.
