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Iron-Doped Titanium Dioxide Nanomaterials: Synthesis, Characterization and Photodegradation Catalytic Behavior

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Iron-Doped Titanium Dioxide Nanomaterials: Synthesis, Characterization and Photodegradation Catalytic Behavior Iron-doped Titanium Dioxide Nanomaterials: Synthesis, Characterization and Photodegradation Catalytic Behavior Mohammad Nazari A DISSERTATION SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY GRADUATE PROGRAM IN CHEMISTRY YORK UNIVERSITY TORONTO, ONTARIO January 2019 © Mohammad Nazari, 2019 Abstract Titanium dioxide (TiO2) is a very good material for various photocatalytic industrial applications because of its non-toxicity, high chemical stability, low cost and relatively good photoactivity. However, one of the most serious challenges to its applicability is its wide band gap and because of that TiO2 absorbs mainly in the UV region of the solar spectrum, which corresponds to a small portion (<10%) of the sun's energy. In this thesis, doping of TiO2 is employed as a method to improve TiO2 optical properties by decreasing the band gap and enabling the material to absorb a larger fraction of the visible spectrum. A series of iron-doped titanium dioxide nanoparticles containing various percentages of iron was prepared and their chemical, structural, optical and electrochemical properties were characterized. These results confirm that the proposed materials were successfully prepared and that they indeed have smaller band gaps. Raman imaging was also employed to map the various phases present in our samples and to identify surface functionalities on the materials and their accessibility to binding especially with dyes, such as N3 and Z907 dye, for the first time. The results shows the coexistence of phases in TiO2 as well as adsorption pattern of the dyes on the surface of the TiO2. Finally, The photodegradation of methylene blue has been studied to quantify the photocatalytic activity of all prepared iron-doped TiO2 and pure TiO2 photocatalysts under simulated sunlight. The measurements are performed at two pH values and the different mechanism observed can be explained in terms of changes in the materials’ potential of zero charge (PZC) and how surface charge affects the dye adsorption. Using the Langmuir-Hinshelwood model, rate constants (kobs) decreasing with an increase in the molar percentage of iron in TiO2 as well as a decrease in the materials’ band gap. This trend is opposite to what was expected and it could be due to a significant increase in the charge recombination rate when the band gap is reduced, meaning that less charge is available to participate in the photodegradation process. ii Dedications -To my parents who raised me with their unconditional love, warmth, support, patience and kindness allowed me to focus on my life goals and reach my dreams. -To my siblings for their love, support and kindness. -To my role model, Dr. Mostafa Chamran, for his inspiration to survive even in the most sophisticated conditions. iii Acknowledgement First and foremost, I must express my gratitude to my supervisor, Professor Sylvie Morin, for all her incredible support through this project. You have shown me how to think in a critical way while having always the big picture of the project in my mind. I appreciate the freedom you provided for me to learn and find my way through out conducting this project. I warmly thank you for providing the opportunity to travel to Germany two times for my research and internship, although they were not mandatory parts of my PhD program. I also thank Professor René Fournier for undertaking the membership of my supervisory committee. I applause your positive attitude as well as your constructive support. I acknowledge Professor Jennifer Chen not only as a member of my supervisory committee, but also for assisting us to conduct part of my experiments in her research lab. Your great help and cooperation is well appreciated. I express my gratitude to Professor Jérôme Claverie and Professor Usman T. Khan for being my external and internal examiners, respectively. I appreciate your great feedback. I am incredibly grateful to Professor Susan Andrews from Department of Civil Engineering at University of Toronto, for her great collaboration for running all photocatalytic tests. I will never forget your kindness, support and the positive environment you provided me to successfully finish the last part of my work. I would also like to thank her Master's student, Sarah Larlee, for training me all necessary aspect of the DWRG (Drinking Water Research Group) facilities. As one of the most inspiring scientists in my life, I would like to thank Dr. Melisa Hatat Fraile, postdoctoral fellow from the DWRG, for nourishing my mind with new ideas regarding my research. I would like to acknowledge all other members of the DWRG at University of Toronto for all your astonishing help, effort and welcoming attitude, especially Dr. Kerry Evans-Tokaryk and Jim Wang. I express my thanks to Dr. Srebri Petrov and George Kretschmann, both from University of Toronto, for their great collaboration for performing XRD experiments. I also thank Ms. Karen Rethoret and Dr. Magdalena Jaklewicz from York University for assisting with the SEM experiments. iv Definitely, one of my unforgettable memories of my academic life was my internship period during summer 2018 at BASF SE, the world's largest chemical company located in Ludwigshafen, Germany. I was fortunate to meet two of the greatest people I have worked with during all my career life, Dr. Masayuki Hirosue and Dr. Daniel Wilms. I would like to express my deep gratitude to Dr. Hirosue for his unbelievable mentorship, kindness and support. I also acknowledge Dr. Wilms for his welcoming attitude, organization and positive approach. I express also my special gratitude to Dr. Klaus Weishaupt, the managing director of Witec GmbH for his great hospitality at Witec GmbH in Ulm, Germany to perform Raman imaging as well as sponsoring me to participate in a conference in Jena, Germany. I should admit that without the enormous help, coordination and supervision of Dr. Elena Bailo, it would have been impossible to run any experiments there. I would like to kindly thank other Witec GmbH staff for their support. I should thank especially two of my former colleagues in our research group, Dr. Ali Sepehrifard and Dr. Maryam Hariri for all their support, guidance and cooperation. I will never forget all your endless effort to help me to adjust myself in a new country, city and university. I also thank my other current and former coworkers and officemates, Dr. Moriam Ore, Sreena Thekkoot, Dr. Sven Kochmann, Paola Guarracino, Dr. Victor Galievsky and Antoine Dumont, for all the wonderful time that we have spent together. It is impossible to find yourself happy after moving to a new country without having wonderful friends that you can share both your happiness and hardships with them. I discover two of my best friends at York University, Dr. Amirsaman Sajad and Dr. Mahdi Daemi, after I encountered the biggest challenges of my whole life. You are both my friends for life. Thank you both for helping me when nobody pays any attention to me. I express my gratitude to all former and current staff members of Department of Chemistry at York University, especially Mary Mamais, Magy Baket, Natasha May and Sindy Mahal for your constant help during my academic life at York University. The last but not least, I would like to acknowledge all my family members. Although I have been living very far from you, you have been always in my heart. Without you, it was impossible to accomplish any kind of success I have reached so far in my life. I would like to thank the most v important person in my life, my mother. I know I am not able to thank you as you deserve it. Your unconditional love and understanding means the world to me. You are always my role model in terms of patience, kindness and humanity. I am very blessed to have you in life. vi Table of Contents Abstract..........................................................................................................................................ii Dedications....................................................................................................................................iii Acknowledgement.........................................................................................................................iv Table of Contents.........................................................................................................................vii List of Tables...............................................................................................................................xiii List of Figures..............................................................................................................................xiv List of Abbreviations.................................................................................................................xxii Chapter 1: Introduction................................................................................................................1 1-1-Outline of the thesis...................................................................................................................1 1-2-Introduction...............................................................................................................................2 1-3-Chemical structure of titanium dioxide.....................................................................................3 1-4-Doping.......................................................................................................................................5 1-5-Sol-gel
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