New challenges arise with advances in our understanding of two dimensional (2D) materials and their functionalities. The reactivity of defects engineered to drive targeted reactions, such as those relevant to sustainability, or to shape the electronic properties of the host material locally for new applications, such as in nanoelectronics or quantum computing, brings about the need to control the environment of the material and the defect. This is particularly important to advance fundamental studies of catalytic processes to mimic the reaction pathways taking place in large scale reactors at various defect sites. With atomic defects, this constitutes an outstanding challenge as it requires to develop tools that detect the presence of defects, achieve nanoscale resolution to visualize the defects, and monitor the structural and/or compositional changes taking place at defect sites under various environments. Such tools are not readily available. In this dissertation, we review the state of the art in catalytic reactions that have been reported on defect-engineered 2D materials. We discuss the level of fundamental understanding of processes taking place at defect sites reached with existing technology and detail the motivation of our work. Next, we summarize the different methods of 2D materials growth and the associated advantages and limitations for the targeted application of catalysis. Beside the most common techniques used for hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDs), we discuss our efforts to grow and characterize zirconium disulfide (ZrS2) using chemical vapor deposition. After the 2D materials are produced, we delve into the common methods of defect engineering that have been reported, including those to achieve large scale production or those to control the defect and their positions locally. We present our results in using ball milling defects in h-BN. With defect-laden h-BN, we describe our approach to control the environment of the defect to monitor the evolution of the defect under various environments including air, propene, propane, CO, CO2, H2, and O2 when activated with visible light. We explore in more details the synthesis for carbonaceous microstructures resulting from the reaction of defect-laden h-BN and propene, which constitutes an innovative approach. Finally, we investigate a new approach to controllably introduce defects in h-BN at targeted locations using AFM coupled with pulsed infrared light. We determine the effect of light, material of the tip, and thickness of the material in getting controllable defects. To conclude, we propose a perspective of the work and of potential near- and long-term applications of the work. We also discuss opportunities for in situ nanoscale imaging and spectroscopy to unveil important phenomena taking place at defect sites of catalysts and other functional materials that are often overlooked today due to the lack in technology.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Torres-Davila, Fernand, "Toward In-situ Nanoscale Imaging and Spectroscopy: Applications in Growth and Catalysis of Two-dimensional Materials" (2021). Electronic Theses and Dissertations, 2020-. 777.