Access Type

Open Access Dissertation

Date of Award

January 2022

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry

First Advisor

Aaron S. Rury

Second Advisor

Zhenfei Liu

Abstract

We develop the fundamental mechanistic understanding of the microscopic behavior of three next generation materials: antiferroelectrics, hybrid perovskites and metal organic frameworks. These materials have the potential to be used in energy and light related applications which could provide a solution for the energy efficiency challenges we face in todays society. Ideally we need to begin to bridge the gap of developing candidate materials that possess high power density and high energy density. The first step in bridging this gap is understanding how the material influ- ences its structure and thus the properties and performance. We leverage vibrational spectroscopy and first principles calculations to provide the fundamental insight into the electronic behaviors of these three materials. The antiferroelectric materials due to their dipole arrangements leads to a higher energy storage density than ferroelectric materials. We studied the anharmonic behaviors of vibrations in 2-trifluormethylbenzimidazole (TFMBI), the antiferroelectric material of interest, using temperature-dependent Raman Spectroscopy. We find the quartic anharmonic contribution to the interatomic potential energy can account for the observed vibrational peak shifts. In addition, we find our anharmonic model fits improve as we manually adjust the harmonic frequency. The perovskites are a layered 2D material consisting of organic and inorganic layers. We first determined the nature of the coupling between the layers and found the ammonium group is driving the electrostatics between the layers. We then examined the electronic structure of defective hexyl-ammonium lead iodide, the perovskite of interest, to understand how to control the light spectra these materials emit. We find the combination of iodine and hydrogen vacancies produce a localized electronic state in an energetic vicinity consistent with our experimental results. Metal organic frameworks are important in several applications including gas adsorption. We study two vanadium based MOFs, MIL-47 and MFM-300 with different organic linkers. We explored the binding mechanism of light hydrocarbons in the pores of our materials, focusing on the role the -OH/-O functional group plays. We conclude that the -OH or -O group acts as a pseudo-open metal site that provides the necessary binding preference and selectivity. The structure-property relation- ships we uncovered in these next-generation materials provides insight into the future design for desired functionality.

Download

Share

COinS