Research Project: Yesil H2 Üretimi Için Atomik Katmanlı Heteroyapıların Makine Ögrenimine Dayalı Asagıdan Yukarıya Tasarımı
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Contributors
Funders
ID
TB.00799
Authors
Doustkhah, Esmail
Researcher
Publications
Catalytic synergy between PD nanoclusters and ligand-functionalized layered silicates for improved formic acid dehydrogenation
(American Chemical Society, 2024) Yusufoğlu, Muhammed; Zarenezhad, Hamaneh; Doustkhah, Esmail; El-Hosainy, Hamza; Ide, Yusuke; Gutierrez Moreno, Jose Julio; Assadi, M. Hussein N.; KUTEM (Koç University Tüpraş Energy Center); Graduate School of Sciences and Engineering; No; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center
The synthesis and stabilization of Pd nanoclusters on a support, as well as simultaneously achieving optimal catalytic activity, remain challenging tasks. Functionalizing the support surface with specific ligands offers a promising solution, but it often requires carefully balancing trade-offs between the reaction yield and catalyst stability. Here, we used two different ligands (propylamine and propylthiol) to functionalize the layered silicate's interlayer surface for Pd nanocluster synthesis and stabilization. For dehydrogenating formic acid, Pd nanoclusters on aminopropyl groups achieved a catalytic activity similar to 27-fold higher than that of thiopropyl groups at 70 degrees C. Our density functional calculations compared the adsorption energetics and bonding characteristics of single Pd atoms and Pd13 nanoclusters on amino- and thio-functionalized silicate surfaces. Pd-N bonds were predicted to be weaker with minimal covalency, while Pd-S bonds exhibit greater covalency due to higher 4d-3p hybridization, resulting in better stability. However, Pd-13 clusters undergo severe structural deformation on thiol-functionalized surfaces, resulting in a smaller overall surface area and diminished catalytic stability.
Interlayer atomic voids by partial cesium defect in layered titanate activate photo(electro)catalytic H2 and O2 generation
(American Chemical Society, 2025) Üstünel, Tuğçe; Jahangiri, Hadi; Kaya, Sarp; Gutierrez Moreno, Jose Julio; Zheng, Xiaoran; Mofarah, Sajjad S.; Doustkhah, Esmail; Graduate School of Sciences and Engineering; KUHyTech (Koç University Hydrogen Technologies Center); Department of Chemistry; KUYTAM (Koç University Surface Science and Technology Center); Yes; Üstünel, Tuğçe; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Research Center; College of Sciences
Although many layered oxide semiconductors possess seemingly suitable band gaps for photo(electro)catalysis in the UV-vis range, they often exhibit low or no activity in practice. Bulk layered cesium titanate is one such example of an inactive semiconductor, where the introduction of cesium vacancies with subsequent thermal treatment leads to the activation of its photocatalytic properties. Here, we demonstrate the promising effect of cesium vacancies on the photocatalytic (PC) activity enhancement in the hydrogen evolution reaction (HER) from water in the presence of H2O/MeOH (80:20). In a separate experiment, we also further prove that the Cs-vacant (VCs) layered titanate sample treated at 700 degrees C exhibits a remarkably improved photoelectrocatalytic (PEC) activity in the oxygen evolution reaction (OER) of partially exfoliated cesium titanates. In contrast, bulk cesium titanate shows no PC activity toward HER and only minimal PEC activity toward OER. Computational modeling reveals that partial interlayer Cs vacancies can increase the surface area up to 120 & Aring;2 and generate interlayer voids as large as 10 & Aring;. Furthermore, hybrid density functional theory (DFT) calculations indicate that these Cs vacancy defects lead to the formation of midgap states, which are expected to enhance photogenerated charge carrier separation and stabilization, thereby improving both PC and PEC activities. Our approach results in the development of a cocatalyst-free semiconductor light absorber capable of producing hydrogen with significantly higher efficiency than both bulk cesium titanate and protonated layered titanate.
Metal-support interaction in PT nanodisk-carbon nitride catalyst: insight from theory and experiment
(MDPI, 2024) Balkan, Timuçin; Doustkhah, Esmail; Kotb, Ahmed; Assadi, Mohammad Hussein Naseef; KUTEM (Koç University Tüpraş Energy Center); No; Research Center
Metal-support interaction plays a critical role in determining the eventual catalytic activity of metals loaded on supporting substrates. This interaction can sometimes cause a significant drop in the metallic property of the loaded metal and, hence, a drop in catalytic activity in the reactions, especially in those for which low charge carrier transfer resistance is a necessary parameter. Therefore, there should be a case-by-case experimental or theoretical (or both) in-depth investigation to understand the role of support on each metal. Here, onto a layered porous carbon nitride (g-CN), we grew single crystalline Pt nanodisks (Pt@g-CN) with a lateral average size of 21 nm, followed by various characterisations such as electron microscopy techniques, and the measurement of electrocatalytic activity in the O-2 reduction reaction (ORR). We found that intercalating Pt nanodisks in the g-CN interlayers causes an increase in electrocatalytic activity. We investigated the bonding mechanism between carbon support and platinum using density functional theory and applied the d-band theory to understand the catalytic performance. Analysis of Pt's density of states and electronic population across layers sheds light on the catalytic behaviour of Pt nanoparticles, particularly in relation to their thickness and proximity to the g-CN support interface. Our simulation reveals an optimum thickness of similar to 11 angstrom, under which the catalytic performance deteriorates.
