Researcher:
Aksoy, Dilan

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PhD Student

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Dilan

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Aksoy

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Aksoy, Dilan

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2021 - 20233

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Researcher Of Publications: search.filters.isAuthorOfPublication.f59f610b-c5cc-4e24-81d1-f0595bc74af0

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    Controlling oxygen reduction reaction activities of Ag@Pt core-shell nanoparticles via tuning of ag in the surface layer
    (Wiley-VCH, 2023) Savaci, Umut; Turan, Servet; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Aksoy, Dilan; Karakaya, Cüneyt; Balkan, Timuçin; Metin, Önder; Kaya, Sarp; PhD Student; PhD Student; Other; Faculty Member; Faculty Member; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; College of Sciences; College of Sciences; N/A; N/A; N/A; 46962; 116541
    Herein, the effect of Pt shell thickness and Ag content in the surface layer on the oxygen reduction reaction activities of Ag@Pt core@shell nanoparticles (NPs) is discussed. Ag@Pt NPs are synthesized via the seeded-growth method, where colloidal Ag NPs are first synthesized and used as seeds for the growth of Pt. Electrochemical activity measurements in alkaline media show a remarkable dependency between the Ag content in the shell and the oxygen reduction reaction (ORR) activity, where the overpotentials required for -1.0 mA cm(-2) drop gradually, that is, 0.72, 0.77, and 0.80 V-RHE for Ag@Pt-25, Ag@Pt-35, and Ag@Pt-45, respectively. Tafel analysis also confirms this dependency with 73.5 mV dec(-1) for Ag@Pt-25, 71.3 mV dec(-1) for Ag@Pt-35, and 68.8 mV dec(-1) for Ag@Pt-45. A combination of the high-resolution transmission electron microscope, X-ray photoelectron spectroscopy, and X-Ray diffraction analysis shows an increase of the Pt shell thickness. It is shown that the absence of Pt-H adsorption/desorption peaks in cyclic voltammetry of Ag@Pt NPs is correlated with Ag in the surface layer, which plays an important role in the ORR activity due to the blockage of Pt(111) terrace sites. Rate-limiting first-electron transfer to oxygen is facilitated by decreasing Ag amount at the surface.
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    Ag/AgCl clusters derived from AgCu alloy nanoparticles as electrocatalysts for the oxygen reduction reaction
    (Royal Society of Chemistry (RSC), 2022) Harfouche, Messaoud; N/A; N/A; N/A; Department of Chemistry; Department of Chemistry; Balkan, Timuçin; Küçükkeçeci, Hüseyin; Aksoy, Dilan; Metin, Önder; Kaya, Sarp; Other; Master Student; PhD Student; Faculty Member; Faculty Member; Department of Chemistry; 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); N/A; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; 46962; 116541
    The structural changes induced by the selective dealloying of bimetallic alloy electrocatalysts could have a significant impact on the kinetics of the oxygen reduction reaction (ORR). Herein, we show that the activity of bimetallic AgCu alloy nanoparticles (NPs) towards the ORR can be enhanced by dealloying Cu in an acidic medium. A combination of core-level X-ray spectroscopy and X-ray diffraction investigations with scanning electron microscopy reveals that dealloying in HCl performed on annealed AgCu alloy NPs leads to the formation of relatively large nanostructures composed of Ag/AgCl. The initial composition of AgCu alloy NPs and the extent of the AgCl formation on Ag surfaces have a significant effect on the ORR activity. Furthermore, the formation of the active surface structure strongly depends on the initial composition of alloy NPs. Ag decorated with AgCl formed after dealloying Ag7Cu3 alloy NPs presents a superb ORR activity with a high onset potential (E-0) of approximate to 0.97 V vs. RHE, comparable to commercial Pt/C catalysts and outperforms dealloyed Ag3Cu2 and pristine Ag electrocatalysts. We suggest that Ag+ stabilized in the presence of sub-stoichiometric Cl- plays a critical role in the superior activity of the catalyst.
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    The significance of the local structure of cobalt-based catalysts on the photoelectrochemical water oxidation activity of BiVO4
    (Pergamon-Elsevier Science Ltd, 2021) Harfouche, Messaoud; Ogasawara, Hirohito; N/A; N/A; N/A; N/A; N/A; N/A; N/A; Department of Chemistry; Barzgarvishlaghi, Mahsa; Kahraman, Abdullah; Apaydın, Sinem; Usman, Emre; Aksoy, Dilan; Balkan, Timuçin; Munir, Shamsa; Kaya, Sarp; PhD Student; PhD Student; Master Student; Master Student; PhD Student; Other; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; N/A; N/A; College of Sciences; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); N/A; N/A; N/A; N/A; N/A; N/A; N/A; 116541
    The local structures of the water oxidation catalysts play an important role in reaction kinetics and the performance of the photoanodes. In this study, we deposited cobalt-based catalysts on nanoporous BiVO4 with controlled thicknesses by atomic layer deposition (ALD). Despite the similar oxidation states of cobalt in all depositions, different water oxidation activities in neutral pH conditions were observed. A dramatic photocurrent raise, lowered kinetic overpotential, and smaller charge transfer resistance across the photoanode/electrolyte interface were achieved when a uniform ultrathin Co(OH)(2) layer was formed on BiVO4. Photocurrent density for water oxidation showed a 95% enhancement at 0.6 V vs. RHE when the catalyst was in the form of Co(OH)(2), while an 80% increase was obtained for CoO. Ideal coordination of Co(OH)(2) on hydroxylated BiVO4 surface assists the charge transfer between the electrolyte and BiVO4 without increasing surface recombination. The results of this study emphasize the importance of controlling the local structure of the catalysts in the performance of the water splitting photoanodes.