Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Design of Sulfur Resistant Cobalt Catalysts by Boron Promotion: Atomic Scale Insights(Sakarya University, 2024) Kızılkaya, A.C.The effect of boron promotion on atomic sulfur formation by hydrogen sulfide dissociation on Co(111), flat surfaces of cobalt nanoparticles, was investigated using Density Functional Theory calculations. The results show that on clean Co(111), hydrogen sulfide dissociation proceeds fast due to low activation barriers, yielding atomic sulfur on the cobalt surfaces. Boron promotion hinders the dissociation of hydrogen sulfide due to increased activation barriers. Furthermore, boron prevents the interaction of sulfur compounds with cobalt surface atoms, as these poisons bind on boron. The findings indicate that boron is an effective promoter that can be used to design sulfur resistant cobalt catalysts. © 2024, Sakarya University. All rights reserved.Article Design of Sulfur Resistant Cobalt Catalysts by Boron Promotion: Atomic Scale Insights(Sakarya University, 2024) Kizilkaya, A.C.The effect of boron promotion on atomic sulfur formation by hydrogen sulfide dissociation on Co(111), flat surfaces of cobalt nanoparticles, was investigated using Density Functional Theory calculations. The results show that on clean Co(111), hydrogen sulfide dissociation proceeds fast due to low activation barriers, yielding atomic sulfur on the cobalt surfaces. Boron promotion hinders the dissociation of hydrogen sulfide due to increased activation barriers. Furthermore, boron prevents the interaction of sulfur compounds with cobalt surface atoms, as these poisons bind on boron. The findings indicate that boron is an effective promoter that can be used to design sulfur resistant cobalt catalysts. © 2024, Sakarya University. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 3Atomic-Scale Insights Into Carbon Dioxide Hydrogenation Over Bimetallic Iron-Cobalt Catalysts: a Density Functional Theory Study(MDPI, 2023) Tuncer, Dilan; Kızılkaya, Ali CanThe conversion of carbon dioxide to fuels and chemicals is a promising long-term approach for mitigating CO2 emissions. Despite extensive experimental efforts, a fundamental understanding of the bimetallic catalytic structures that selectively produce the desired products is still lacking. Here, we report on a computational surface science approach into the effect of the Fe doping of Co(111) surfaces in relation to CO2 hydrogenation to C1 products. Our results indicate that Fe doping increases the binding strength of surface species but slightly decreases the overall catalytic activity due to an increase in the rate-limiting step of CO dissociation. FeCo(111) surfaces hinder hydrogenation reactions due to lower H coverages and higher activation energies. These effects are linked to the Lewis basic character of the Fe atoms in FeCo(111), leading to an increased charge on the adsorbates. The main effect of Fe doping is identified as the inhibition of oxygen removal from cobalt surfaces, which can be expected to lead to the formation of oxidic phases on bimetallic FeCo catalysts. Overall, our study provides comprehensive mechanistic insights related to the effect of Fe doping on the catalytic behavior and structural evolution of FeCo bimetallic catalysts, which can contribute to the rational design of bimetallic catalysts.Review Citation - WoS: 18Citation - Scopus: 18A Review on New Cobalt-Free Cathode Materials for Reversible Solid Oxide Fuel Cells(Chulalongkorn Univ, Metallurgy & Materials Science Research Inst, 2023) Akkurt, Sedat; Sındırac, Can; Özmen Egesoy, Tuğce; Ergen, EmreThe exponential growth in the requirement of fuel cells and batteries leads to increased demand for cobalt due to its common use in high-performance Li-ion batteries and high-temperature fuel cells/electrolyzers. This sharp increment in demand raises concern about the availability of limited reserves of cobalt which can impact the price of cobalt. Moreover, the geographic limitations of cobalt resources may endanger the whole supply chain. In addition to all those, huge moral issues of cobalt mining are also another problem. Hence, leading battery, fuel cells and electrolyzer manufacturers are looking for sustainable alternatives to reduce cobalt dependency. A more specific limitation is shown in Solid Oxide Fuel Cells (SOFCs) cathode materials that contain cobalt. Incompatibilities have already been observed between the cathode materials containing cobalt and the electrolytes in terms of the thermal expansion coefficient mismatch during the transition of the operating temperature from high to low. An advantage of low operating temperatures is the reduction of material costs compared to high temperature. Increasing the electrochemical performance of the cell and eliminating thermal expansion coefficient difference problems are in concert aimed at the development of cobalt-free cathode materials. Therefore, cobalt-free cathode materials are vital for the sustainability of SOFCs and green transition of the energy sector since they can be used as cathode and anode material in symmetrical SOFCs which is also known as reversible SOFC (RSOFC). In this review, we comprehensively summarize the recent advances of cobalt-free perovskite cathode materials for intermediate temperature RSOFCs.Article Citation - WoS: 21Citation - Scopus: 22High-Dose Exposure To Polymer-Coated Iron Oxide Nanoparticles Elicits Autophagy-Dependent Ferroptosis in Susceptible Cancer Cells(MDPI, 2023) Lomphithak, Thanpisit; Helvacıoğlu, Selin; Armenia, Ilaria; Keshavan, Sandeep; Ovejero, Jesus G.; Baldi, Giovanni; Ravagli, Costanza; Grazú, Valeria; Fadeel, BengtFerroptosis, a form of iron-dependent, lipid peroxidation-driven cell death, has been extensively investigated in recent years, and several studies have suggested that the ferroptosis-inducing properties of iron-containing nanomaterials could be harnessed for cancer treatment. Here we evaluated the potential cytotoxicity of iron oxide nanoparticles, with and without cobalt functionalization (Fe2O3 and Fe2O3@Co-PEG), using an established, ferroptosis-sensitive fibrosarcoma cell line (HT1080) and a normal fibroblast cell line (BJ). In addition, we evaluated poly (ethylene glycol) (PEG)-poly(lactic-co-glycolic acid) (PLGA)-coated iron oxide nanoparticles (Fe3O4-PEG-PLGA). Our results showed that all the nanoparticles tested were essentially non-cytotoxic at concentrations up to 100 mu g/mL. However, when the cells were exposed to higher concentrations (200-400 mu g/mL), cell death with features of ferroptosis was observed, and this was more pronounced for the Co-functionalized nanoparticles. Furthermore, evidence was provided that the cell death triggered by the nanoparticles was autophagy-dependent. Taken together, the exposure to high concentrations of polymer-coated iron oxide nanoparticles triggers ferroptosis in susceptible human cancer cells.Article Citation - WoS: 6Citation - Scopus: 9Mechanistic Insights Into the Effect of Sulfur on the Selectivity of Cobalt-Catalyzed Fischer–tropsch Synthesis: a Dft Study(MDPI, 2022) Dağa, Yağmur; Kızılkaya, Ali CanSulfur is a common poison for cobalt-catalyzed Fischer–Tropsch Synthesis (FTS). Alt-hough its effects on catalytic activity are well documented, its effects on selectivity are controversial. Here, we investigated the effects of sulfur-covered cobalt surfaces on the selectivity of FTS using density functional theory (DFT) calculations. Our results indicated that sulfur on the surface of Co(111) resulted in a significant decrease in the adsorption energies of CO, HCO and acetylene, while the binding of H and CH species were not significantly affected. These findings indicate that sulfur increased the surface H/CO coverage ratio while inhibiting the adsorption of carbon chains. The elementary reactions of H-assisted CO dissociation, carbon and oxygen hydrogenation and CH coupling were also investigated on both clean and sulfur-covered Co(111). The results indicated that sulfur decreased the activation barriers for carbon and oxygen hydrogenation, while increasing the barriers for CO dissociation and CH coupling. Combining the results on elementary reactions with the modification of adsorption energies, we concluded that the intrinsic effect of sulfur on the selectivity of cobalt-catalyzed FTS is to increase the selectivity to methane and saturated short-chain hy-drocarbons, while decreasing the selectivity to olefins and long-chain hydrocarbons.Article Citation - WoS: 15Citation - Scopus: 18Preparation and Characterization of Magnesium Stearate, Cobalt Stearate, and Copper Stearate and Their Effects on Poly(vinyl Chloride) Dehydrochlorination(John Wiley and Sons Inc., 2015) Gönen, Mehmet; Egbuchunam, Theresa Obuajulu; Balköse, Devrim; İnal, Fikret; Ülkü, SemraPreparation and characterization of pure metal soaps and investigation of their effects on poly(vinyl chloride) (PVC) dehydrochlorination were the objectives of the present study. Magnesium stearate (MgSt2), cobalt stearate (CoSt2), and copper stearate (CuSt2) were prepared by a precipitation method. An aqueous sodium stearate (NaSt) solution was mixed at 500 rpm with respective metal salt solutions at 75oC. The precipitates that formed were collected by filtration, washed with water, and ultimately dried at 105oC under reduced pressure. Lamellar crystals that melted on heating were obtained. Solid-liquid phase transitions were observed by optical microscopy at 160oC, 159oC, and 117oC for MgSt2, CoSt2, and CuSt2, respectively. However, the melting points of MgSt2, CoSt2, and CuSt2 were determined as 115oC, 159oC, and 111oC, respectively, by analysis by differential scanning calorimetry. The onset temperature of the mass loss was the lowest at 255oC for CuSt2 and the lowest activation energy for thermal decomposition was 18 kJ/mol for CuSt2. CoSt2 was effective in extending the induction time of PVC dehydrochlorination at both 140oC and 160oC. The activation energy calculated from stability time decreased from 175 kJ/mol for a blank PVC sample to 114, 105, and 107 kJ/mol for MgSt2, CoSt2, and CuSt2-containing PVC samples, respectively. All three metal soaps accelerated the dehydrochlorination of PVC. J. VINYL ADDIT. TECHNOL., 21:235-244, 2015.Article Citation - WoS: 26Citation - Scopus: 24Effect of Ta Buffer Layer and Thickness on the Structural and Magnetic Properties of Co Thin Films(AVS Science and Technology Society, 2009) Vahaplar, Kadir; Tarı, Süleyman; Tokuç, Hüseyin; Okur, SalihSingle Co and Ta/Co bilayers were grown on Si(100) substrates in a magnetron sputtering system. The effect of Ta buffer layer and the thickness of Co layer on the structural and magnetic properties of the Co layers has been studied. A single Co layer shows a textured structure above thickness of 40 nm according to the x-ray diffraction (XRD) pattern. The magnetic properties of Co layers depend significantly on the thickness of the films. Ta grows as highly textured Β -Ta (tetragonal) phase on Si with a smooth surface. The XRD and atomic force microscopy results show that the Ta buffer layer improves the structural properties dramatically, resulting in a strongly textured and smoother surface morphology. The Ta layer also affects the magnetic properties of Co layers to a large extent, especially inducing an in-plane anisotropy in thin Co films.