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Solid-State NMR Structural Studies of Multifunctional Carbon-Based Materials
thesisposted on 31.10.2017 by Yichen Hu
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
This dissertation focuses on elucidating the structures of five important carbon-based materials using solid-state nuclear magnetic resonance (SSNMR) as well as other analytical methods. All of these materials originate from or are associated with rather unremarkable naturally-occurring graphite, yet possess exceptional properties leading to important applications. Three of these materials are derivatives of graphene oxide (GO) – a product of the oxidation of graphite. Structural investigation of GO-derivatives to better understand graphene chemistry has evolved into a pivotal issue in an era of rapid development of two-dimensional (2D) materials. The fourth material is an activated form of graphene, named activated microwave-expanded graphite oxide (a-MEGO). a-MEGO’s unique electronic properties, such as its capacitance and energy density due to its ultra-high surface area, make it an ideal supercapacitor electrode material. Despite great interest in its use, a structural representation of a-MEGO is lacking. Additionally, the adsorption mechanism of electrolytes to a-MEGO has not been investigated. The last material examined in this thesis, graphitic carbon nitride (g-C3N4), is a semiconducting polymer. It can be synthesized from different precursors and is widely known for its unique electronic properties for artificial photosynthesis, e.g., water splitting. Recent studies have demonstrated a novel synthetic approach for 2D g-C3N4 using the small-molecular precursor urea. However, the effectiveness of such a synthetic approach and the resultant polymeric forms of g-C3N4 remain unknown. The overarching goal of this dissertation research is to investigate the structures of these five materials and address the aforementioned issues using SSNMR. Successful completion of these investigations contributes greatly to understanding the electronic properties of these carbon-based materials and extending their applications to new territories.