Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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  • Doctoral Thesis
    Synthesis and Characterization of Doped Defective Titania Based Photocatalysts for Hydrogen Generation
    (01. Izmir Institute of Technology, 2025) Gözel, Gözde; Top, Ayben
    Sera gazlarındaki artış, sürdürülemez fosil yakıtların yaygın kullanımıyla yoğunlaşarak sera etkisini artırmış ve bu da küresel ısınma ve iklim değişikliğine yol açmıştır. Yapay fotosentez, küresel CO2 seviyelerini azaltırken metan, metanol ve hidrojen gibi yenilenebilir, sürdürülebilir yakıtlar üretmek için umut verici bir tekniktir. Benzersiz optik ve kimyasal özellikleriyle bilinen titanyum bazlı fotokatalitik malzemeler, yapay fotosentezde yaygın olarak kullanılmakta olup, yakın zamanda sentezlenen siyah nano titanya malzemeleri de dahil olmak üzere nano tasarımlı hatalı TiO2 yapıları, UV veya güneş ışığı ile çalışan fotokatalitik hidrojen üretimi için en umut verici adaylardan bazıları olarak ortaya çıkmaktadır. Bu çalışmada, hatalı TiO2 bazlı fotokatalizörler sentezlenmiş ve geliştirilmiş fotokatalitik verimlilik potansiyellerini araştırmak için karakterize edilmiştir. Saf TiO2, hidrosol ve çöktürme yöntemleri kullanılarak sentezlenmiş, ardından kusurların oluşturulması için NaBH4 indirgeme maddesi ile indirgenmiştir. Hidrosol yöntemiyle üretilen hatalı TiO2 nanomalzemeler, indirgeme sıcaklığı ve TiO2-NaBH4 ağırlık oranı gibi indirgeme koşullarının optimize edilmesine odaklanırken, çöktürme yöntemi ön ısıtma işlemi ve indirgeme stratejileri içermektedir. Malzemelerin yapısal/optik özelliklerini analiz etmek için XRD, SEM, BET, ATR-FTIR, PL, UV-Vis spektroskopisi ve GC analizi gibi gelişmiş karakterizasyon teknikleri uygulanmıştır. Hidrosol yöntemiyle üretilen hatalı TiO2 nanomalzemeler, 325°C indirgeme sıcaklığında ve TiO2-NaBH4 (1:1) ağırlık oranıyla en yüksek hidrojen verimini elde etmiştir. Çökeltme yöntemiyle üretilen hatalı TiO2 nanomalzemeler ise 500°C'de ön ısıtma sonrasında optimum aktivite göstermiştir. Zr/Nd katkı maddesiyle yapılan katkılama çalışmaları, katkılanmamış fotokatalizörlere kıyasla hidrojen üretim verimliliğini artırmıştır.
  • Doctoral Thesis
    Removal of Dyes and Antibiotics by Adsorption and Photocatalytic Degradation Using Zn-Based Composites
    (01. Izmir Institute of Technology, 2023) Saygı, Gizem; Çakıcıoğlu Özkan, Seher Fehime
    In this study, the ZIF-8 was synthesized and immobilized on the clinoptilolite surface (ZIF8@CLN) and doped with Ag nanoparticles, forming the Ag-ZIF8 and Ag-ZIF8@CLN composite materials. The characterization results indicated that the ZIF-8 was well-deposited on the clinoptilolite surface and doped successfully with Ag nanoparticles. The adsorption and photocatalytic activity of these adsorbents/catalysts were evaluated by the removal of the organic pollutants such as dyes and antibiotics. The target dyes were cationic Methylene blue (MB), anionic Methyl orange (MO) and Congo red (CR), and zwitterionic Rhodamine B (RhB). The target antibiotic was tetracycline (TC). The influence of various parameters on removal was investigated using different initial pH, photocatalyst amount, pollutant concentrations and ionic strength. The results showed that ZIF-8 and ZIF-8@CLN are excellent adsorbents. However, the photocatalytic activity of Ag-ZIF8 and especially Ag-ZIF8@CLN composites were much better than ZIF-8 and ZIF-8@CLN for degradation of all dyes. The Ag-ZIF8 and Ag-ZIF8@CLN composite catalysts exhibited more than 90% removal capacity under UV irradiation for 120 min with the dye concentration of 25 mg L-1 at the optimum pHs of each dye. The enhanced adsorption and photocatalytic performance of the composite photocatalysts was attributed to the synergistic effect between the ZIF-8, CLN and Ag. The adsorption data were evaluated by considering adsorption isotherms, kinetics and thermodynamics using target dyes and antibiotics. Proposed photodegradation mechanism of the dyes over Ag-ZIF8@CLN was explained detailed. This work introduced the ZIF-8-based composite photocatalysts with high efficiency, and may provide to prefer these catalysts in photocatalytic field.
  • Doctoral Thesis
    The Valorization of Various Wastewater for Hydrogen Production by Photocatalytic Oxidation
    (01. Izmir Institute of Technology, 2021) Orak, Ceren; Yüksel Özşen, Aslı
    Hydrogen is a clean, green and sustainable energy and photocatalysis a better approach for hydrogen production from various wastewaters. It was aimed to evolve new hybrid solar-driven catalysts for photocatalytic hydrogen production from various wastewaters. Firstly, catalysts were synthesized. Their characterization study were performed and PL results show that the most promising catalyst was GLFO. The impacts of pH, catalyst loading and light over hydrogen production from SMS were investigated using all synthesized catalysts. The hybrid catalysts show higher efficiency. FFD was created to elucidate the impacts of reaction parameters and graphene content of catalyst had a major impact. To optimize the reaction parameters for all hybrid catalysts, an experimental matrix was created using BBD. The higher hydrogen amounts were observed using GLFO. The same experimental matrix was used to search the effects of reaction parameters over produced hydrogen amounts from sugar beet wastewater using all hybrid catalysts and the highest hydrogen production was observed using GLFO. The observed reaction followed first order reaction model based on TOC removal. Therefore, the degradation of organic pollutants in wastewater streams and hydrogen evolution could simultaneously be achieved. Same experimental matrix was also used for hydrogen evolution from DBU using all hybrid catalysts. Relatively lower hydrogen amounts were obtained so that it was also treated under subcritical conditions. FFD was created to search the impacts of reaction parameters and NaOH concentration and current density had an impact over DBU removal. Based on GC-MS results, the hazardous intermediates did not form during hydrothermal electrolysis.
  • Doctoral Thesis
    Preparation and Characterization of Titania Based Powders and Suspensions for Photocatalytic Applications
    (Izmir Institute of Technology, 2015) Yurtsever, Hüsnü Arda; Çiftçioğlu, Muhsin
    Growing environmental concerns related to the extensive use of nonsustainable fossil fuels and increasing energy demand will force mankind, sooner or later, to tap into clean and sustainable sources of energy and artificial photosynthesis is being considered as a promising prospect for this concern. Photocatalysis is expected to make a great contribution to solutions for environmental problems and renewable energy generation. Titania based photocatalytic materials are one of the widely used materials in artificial photosynthesis research due to their unique chemical and optical properties. Recent research have shown that rare earth element (REE) doping improves the photocatalytic activity of TiO2 phases in the visible region. The effects of REE doping level and heat treatment temperature on the microstructure evolution, optical properties and the photocatalytic water splitting/CO2 photoreduction activities of mostly sol-gel derived titania powders were investigated in this thesis. The results of this thesis indicated that REE ions may enter the interstitial voids of TiO2 lattice or segregate on the grain boundaries of TiO2 as a separate phase and RE2Ti2O7 phases were formed for the REEs with relatively smaller ionic sizes. The experimental work conducted revealed the importance of surface area, crystallinity, light absorption, the presence of oxygen vacancies and structural defects in the efficiency of photocatalytic processes. Results have shown that REE doping improves the artificial photosynthesis activity of TiO2 at relatively low doping levels and 700oC heat treatment temperature as the production rate of H2 and CO/CH4 were significantly higher with REE doped TiO2 compared to pure TiO2.