Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 TechnologyZinc-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 An Investigation of Electrochemical Stability of Zinc Electrodes for Battery Applications(Izmir Institute of Technology, 2014) Payer, Gizem; Çiftçioğlu, Muhsin; Ebil, Özgenç; Ebil, Özgenç; Çiftçioğlu, Muhsin; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyEnergy is the most important and inevitable requirement for humankind. The increasing energy demand has been connected with technological advances and the population growth. One of the most serious problems of the world is to provide sustainable energy. New alternative energy sources and renewable energy technologies have become notable research subjects due to wide availability of renewable energy sources in the world. However, most renewable energy sources do not provide uninterrupted energy to consumers. An economic, efficient and reliable energy storage technology is desperately needed. Therefore, academic research has focused on improving the capacity of electrochemical energy storage technologies. The main goal of this study is the preparation and characterization of zinc electrodes for battery applications using different zinc oxide powders with various morphologies and additives. Zinc oxide powders were synthesized with chemical precipitation method under different conditions (precursors, temperatures and aging times) in order to investigate their effects on ZnO morphology and on the performance of nickel-zinc battery. It was found out that the initial morphology of ZnO powder was not crucial for the electrochemical performance. Nickel-Zinc batteries with zinc electrodes prepared from commercial ZnO powder had discharge capacities around 247 mAhg-1 and showed slightly better performance compared to nickel-zinc batteries with zinc electrodes prepared from ZnO powders synthesized via chemical precipitation method. It was also determined that zinc electrode morphology was greatly affected by battery additives (PVA and PEG) and charging current density. The effects of some selected electrode additives (Ca(OH)2, PbO and PEG) on battery performance were also investigated. Zinc electrode with all additives showed improved electrochemical properties, such as higher discharge capacity (322 mAhg-1) and utilization ratio (48.86 %.)