Researcher:
Korkut, Sibel Eken

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Sibel Eken

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Korkut

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Korkut, Sibel Eken

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2020 - 20223

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    The rational design of gCN/a-WOx/Pt heterostructured nanophotocatalysts for boosting the hydrogen generation from the hydrolysis of ammonia borane under visible light
    (Elsevier Ltd, 2022) N/A; Department of Chemistry; Department of Chemistry; Aksoy, Merve; Korkut, Sibel Eken; Metin, Önder; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM) / Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 46962
    In-situ generation of platinum nanoparticles (Pt NPs) supported on graphitic carbon nitride/amorphous tungsten oxide (gCN/a-WOx) binary heterojunctions under white-light irradiation was performed during the hydrolysis of ammonia borane (HAB). The gCN/a-WOx/Pt(IV) nanocomposites including different amount of W were prepared to study their comparative photocatalysis for the photocatalytic HAB. The yielded gCN/a-WOx/Pt nanocatalysts provided a maximum turnover frequency (TOF) value of 419.2 mol H2 mol Pt−1 min−1, which is higher than that of gCN/Pt nanocatalysts (287.7 mol H2 mol Pt−1 min−1). Many advanced analytical techniques comprising ICP-MS, TEM, HAADF-STEM, XRD, XPS, EDX, and BET were used to determine the elemental composition, morphology, elemental distribution, crystal structure, chemical/oxidation state of the surface elements and the textural properties of the nanocatalysts. The characterization results support the formation of wrinkled paper-like amorphous phase WOx (a-WOx) materials in multiple oxidation states over the gCN nanosheets. The photophysical properties of gCN/a-WOx nanocomposites were also analyzed by using UV–Vis DRS, PL, and TRES techniques to clarify the contribution of the heterojunction formation between gCN and a-WOx semiconductors to the photocatalytic activity. Owing to the enhanced visible light absorption, suppressed charge recombination, and promoted charge carrier transfer, gCN/a-WOx/Pt nanocatalysts boosted the hydrogen production from the HAB under white-light irradiation by providing 419.2 mol H2 mol Pt−1 min−1 TOF, which is 4.8 times higher compared to the one obtained in dark. A plausible photocatalytic mechanism for the photocatalytic HAB reaction in the presence of gCN/a-WOx/Pt nanocatalysts was suggested based on the results of performed scavenger experiments. The rate law and the activation parameters for the of gCN/a-WOx/Pt catalyzed HAB were also reported along with kinetic studies. Additionally, a reusability test was performed to understand the stability of gCN/a-WOx/Pt nanocatalysts in the HAB such that the significance of a-WOx species in the enhancement of photocatalytic activity became more pronounced. This study reports for the first time that gCN/a-WOx heterojunctions are favorable support materials for the in-situ generation of Pt NPs and promoting the photocatalytic activity of Pt NPs in the hydrogen generation from the HAB under white-light illumination. © 2022 Hydrogen Energy Publications LLC
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    Mesoporous graphitic carbon nitride/black phosphorus/agpd alloy nanoparticles ternary nanocomposite: a highly efficient catalyst for the methanolysis of ammonia borane
    (Amer Chemical Soc, 2020) N/A; Department of Chemistry; N/A; Department of Chemistry; Korkut, Sibel Eken; Küçükkeçeci, Hüseyin; Metin, Önder; Researcher; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; 46962
    A novel ternary nanocomposite, mesoporous graphitic carbon nitride/black phosphorus-AgPd (denoted mpg-CN/BP-AgPd), was successfully fabricated by assembling the as -prepared AgPd alloy nanoparticles (NPs) on mesoporous graphitic carbon nitride/black phosphorus (mpg-CN/BP) binary composites. This novel nanocomposite comprises a heterojunction support material formed by two distinct nonmetallic semiconductors (mpg-CN and BP) with adaptable band gaps and edge voltages, providing enhanced catalytic activity to AgPd alloy NPs in hydrogen generation from the methanolysis of ammonia borane (AB) compared to its single components under the blue light-emitting diode (LED) light illumination. The yielded mpg-CN/BP-AgPd ternary nanocomposites were characterized by many advanced analytical techniques (transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), time-resolved spectroscopy, inductively coupled plasma-mass spectroscopy (ICP-MS), and fourier transform infrared (FTIR), and then they were tested as catalysts in hydrogen generation from the methanolysis of AB at room temperature. Several parameters such as the effect of mpg-CN/BP ratio, alloy composition, and type of the light source were studied to optimize the catalytic activity of the mpg-CN/BP-AgPd nanocomposites in the methanolysis of AB. The best catalytic activity of mpg-CN/BP-AgPd nanocomposites was obtained using an mpg-CN/BP ratio of 5/1 (wt/wt) and Ag50Pd50 alloy composition under the blue LED illumination at room temperature. The activity of the ternary nanocomposites was further enhanced by the acetic acid treatment, and a high initial turnover frequency of 43.7 mol(center dot H-2) mol(catalyst)(-1) min(-1) was reported. Besides their high catalytic activity, the mpg-CN/BP-AgPd nanocomposites were reusable catalysts in the methanolysis of AB. This study also included detailed kinetics of AB methanolysis catalyzed by mpg-CN/BP-AgPd nanocomposites.
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    AuPt alloy nanoparticles supported on graphitic carbon nitride: in situ synthesis and superb catalytic performance in the light-assisted hydrolytic dehydrogenation of ammonia borane
    (Elsevier, 2022) N/A; Department of Chemistry; Department of Chemistry; Aksoy, Merve; Korkut, Sibel Eken; Metin, Önder; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM) / Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 46962
    Addressed herein is the enhancement of catalytic activity of Pt-based nanocatalysts in the hydrolysis of ammonia borane (AB) via in-situ synthesis of bimetallic AuPt alloy nanoparticles (NPs) supported on graphitic carbon nitride (gCN). The presented in-situ synthesis protocol yielded gCN/AuxPt100-x (x = 0, 8, 15, 33) nanocatalysts with highly dispersed AuxPt100-x NPs having the average particle sizes varied in the range of 1.6-2.6 nm over the gCN nanosheets. The generated gCN/Pt92Au8 (600.3 mol H-2 mol Pt-(1) min(-1)) and gCN/Pt85Au15 (587.1 mol H2 mol Pt-1 min(-1)) nanocatalysts showed higher catalytic activity compared to gCN/Pt-100 (525.7 mol H-2 mol Pt-1 min(-1)) under white-light irradiation, attributed to the synergistic effects aroused in the AuPt alloy NPs and heterojunctions formed between gCN and AuPt alloy NPs. The detailed characterization of photophysical properties of gCN/AuxPt100-x nanocatalysts revealed that their boosted catalytic activity is attributed to the improved charge kinetics, higher light absorption, and effective electron transfer channels from gCN to the bimetallic AuPt alloy NPs. The role of photogenerated carriers in the photocatalytic AB dehydrogenation was also elucidated via scavenger studies. This study shows that gCN/AuxPt100-x nanocatalysts can be prepared in situ during the hydrolysis of AB at room temperature and the yielded nanocatalysts have a significant role in boosting the hydrogen production from the light-assisted hydrolysis of AB.