Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

Song, Yang

Abstract

Clean and renewable energy has drawn much attention recently due to the increasing demand for more energy and environmental issues. New materials have been developed and the improved performance of such materials have been achieved in the past decades. It has been proved that application of external high pressure can significantly tune the structure of materials. Consequently, the properties of the materials could also be modified. Therefore, in this thesis, we focused on the high-pressure studies of two classes of energy storage materials, hydrogen storage materials and solar cell materials. Ammonia borane (AB) has been extensively investigated as an excellent hydrogen storage material, and abundant derivatives of AB with lower dehydrogenation temperatures and better kinetics have been obtained. Three AB derivatives, sodium amidoborane (NaAB), hydrazine borane (HB), and ethane 1,2-diamineborane (EDAB) have been studied under high pressure for the first time using in-situ vibrational spectroscopy and synchrotron X-ray diffraction. Structural transformations and interactions between molecules in the crystals have been explored for all three materials. It was also found that the ionic interaction, dihydrogen bonding and hydrogen bonding existing between the molecules in the crystals, which stabilize the crystal structures and may play an important role in the process of the dehydrogenation of materials. Significantly, our studies could also be a guidance for the designing of the new hydrogen storage material by substituting the hydrogen atoms on either B or N atoms to modify the reactivity of B-H and N-H bonds. Formamidinium lead iodide (FAPbI3) perovskite as a superior solar cell material was investigated under high pressure using in situ synchrotron X-ray diffraction, FTIR spectroscopy, photoluminescence (PL) spectroscopy, electrical conductivity (EC) measurements, and ab initio calculations. Structural stabilities of two polymorphs of FAPbI3 and the interactions between organic and inorganic moieties have been explored on compression, and pressure tuned optoelectric properties of FAPbI3 were also studied. Moreover, our investigation thus provides valuable insight into the design and engineering of organolead halide perovskite-based solar cell materials. Overall, our high-pressure studies of energy storage materials could provide the insight into the pressure-tuned structures and properties of the materials.

Available for download on Tuesday, December 31, 2019

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