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198255 https://hdl.handle.net/2286/R.2.N.198255 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2024 379 pages Doctoral Dissertation Academic theses Text eng Snyder, Rose May Birkel, Christina Trovitch, Ryan Kouvetakis, John Arizona State University Partial requirement for: Ph.D., Arizona State University, 2024 Field of study: Chemistry MXenes have garnered a significant amount of interest since they were first discovered in 2010, due to their wide range of interesting properties. The tunability of their parent compound, MAX phases, means that MXenes can have varying M-site metal elements, which can induce interesting properties. The robust M-A bonds in MAX phases means that the bulk solid cannot be mechanically exfoliated, and instead the A- element must be selectively etched from the MAX phase before it can be separated into sheets via delamination. Hydrofluoric acid is most commonly used, as it is selective for A-elements like silicon and aluminum. However, exposure to HF comes with risks. In this work, the aim is to reduce the amount of hydrofluoric acid used and reduce overall exposure while improving the conversion yield of MAX phase to MXene to produce a high-quality product.This dissertation focuses on vanadium- and molybdenum-based MXenes for applications of electrocatalysis. These elements work together well to form MAX phases with layer thicknesses that are not thermodynamically stable with either element alone. In addition, molybdenum is known to be a suitable choice for electrocatalytic reactions, such as the hydrogen evolution reaction (HER). The synthesis of newly discovered MAX phases, (Mo0.75V0.25)5AlC4 and (V1-yMoy)2AlC, are discussed, as well as the exfoliation of these phases into their respective MXenes, (Mo0.75V0.25)5C4Tx and (V1-yMoy)2CTx. The approach to these syntheses is guided by the desire to reduce the use of concentrated HF, instead opting for mixed acid solutions and in situ-formed HF by alkali salt and HCl. In the case of in situ HF, issues with residual Li3AlF6, which has previously caused issues with delamination, has been solved, producing highly stable V2CTx and (Mo1-yVy)2CTx MXenes. Finally, these findings are used to further MAX phase and MXene research on other vanadium based phases, including (V1-yNby)2AlC, (V1-yNby)2CTx, V4AlC3, and V4C3Tx. Inorganic chemistry Materials Science 2D materials MAX phase MXene Solid State Vanadium Advancing the Synthesis and Chemistry of Vanadium-Based MAX Phases and MXenes