Master Degree / Yüksek Lisans Tezleri

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Publisher: search.filters.publisher.01. Izmir Institute of TechnologySubject: search.filters.subject.Electric batteries

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  • Master Thesis
    Development of Carbon-Free Zinc-Air Batteries
    (01. Izmir Institute of Technology, 2024) Ebil, Özgenç; Ebil, Özgenç; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Zinc-air batteries are thought to be among the greatest substitutes for present energy storage systems because of their high energy densities (~1000 Wh/kg), affordability, and safety. However, zinc-air batteries face several problems, such as carbon corrosion, pore-clogging, and electrode passivation. The main cause of these problems is carbon in the air electrode. Therefore, carbon should be eliminated from the air electrode to enhance its performance. This thesis aims to synthesize an electrocatalyst for air electrodes for secondary carbon-free zinc-air batteries within the scope of the M-Era.NET 'AMAZE' project. Initially, manganese oxide was selected as an electrocatalyst and synthesized using a co-precipitation method with different parameters such as concentration, pH, temperature, and precursor materials. The best MnxOy was obtained with a solution pH and temperature of 9.5 and 60°C, respectively. The main precursor for the catalyst was KMnO4, with a ratio of KMnO4:HCl as 20:4 by volume. α-MnO2 with a surface area of 85.68 m2g-1 was obtained. In addition, onset overpotentials for oxygen reduction and oxygen evolution reactions with 650mV and 271mV, respectively, and a maximum current density of 10.5 mA.cm-2 were obtained. Nickel and cobalt additions were evaluated to improve ORR and OER activity. Catalyst with MnxNiyCozOt(1:0.5:0.5) composition performed better than other samples and had the highest surface area (172.06 m2g-1), ORR and OER potentials of 463mV and 700mV, respectively, and current density of 96 mA.cm-2.
  • Master Thesis
    Doping Effect on the Anode Material Capability of 2d Bn Nanosheets
    (01. Izmir Institute of Technology, 2024) Elmacı Irmak, Nuran; Özdemir, Mustafa Coşkun; Irmak, Nuran Elmacı; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this thesis, the potential of BNN surfaces doped with Al, Cl, Co, Fe, Ga, O, P, and S atoms as anode materials in K, Li, Mg, and Na ion batteries was investigated. Semi-empirical tight-binding combined with meta-dynamics methods and density functional theory were utilized to discover these properties. The effects of doping atoms on the electronic structure and geometry of BNN surfaces were also studied. Changes in the electronic structure and conductivity were reported by examining the HOMO-LUMO orbitals and the energy differences between these orbitals. Using previously reported experimental data and examining similar studies from the literature, the atoms to be doped were chosen. While vacancies at the sites of boron atoms in single-layer boron-nitride nanosheets were observed, vacancies formed by nitrogen atoms were not observed, indicating that boron vacancies are much more likely for the doping position. So that doping was performed on the boron atom. The level of quantum calculations used in this work was validated using experimental data. B3LYP/def2-SVP/D4/gCP level of theory is used for all calculations for BNN-nanosheets studied in this thesis. The bond lengths and the HOMO-LUMO energy difference were found to be nearly the same as the experimental data. The conductivity of the BNN surface was increased with the doping process. However, significant improvements are followed by doping of cobalt, iron, and sulfur atoms with 35%, 34%, and 26% alteration, respectively. For a suitable battery manufacture, the potential anode material should offer structures with high theoretical specific capacity, low anode electrode voltage, and minimal volume change between charged/discharged states. It was observed that none of the doped-BNN surfaces involved in this study were suitable for the use of anode material in magnesium ion batteries. On the other hand, they can be used as a negative electrode for potassium, lithium, and sodium batteries. Their capacity in lithium is better than Na and K batteries. Our results suggest that most of the doped BNN surface with ions studied in this thesis could be used as anode materials. However, none of them owns a better battery capacity than classic lithium batteries.