Electronic Theses and Dissertations

Date of Award

1-1-2019

Document Type

Dissertation

Degree Name

Ph.D. in Chemistry

First Advisor

Jared H. Delcamp

Second Advisor

David Colby

Third Advisor

Nathan Hammer

School

University of Mississippi

Relational Format

dissertation/thesis

Abstract

The development of high voltage solar cells is an attractive way to use sunlight to power electrocatalysts for water oxidation, electrocatalysts for CO2 reduction, and consumer electronics. Through careful molecular dye engineering and redox shuttle pairing, our group has reported a single-junction dye-sensitized solar cell (DSC) employing, for the first time, an iron redox mediator (Fe(bpy)33+/2+) in conjunction with a novel wide band gap dye (RR9). This system generates a high photovoltage of 1.42 V. To the best of our knowledge, this system is the highest photovoltage achieved by a single-junction DSC device without metal oxide doping. The RR9/Fe(bpy)33+/2+ redox shuttle pair was used as a front subcell for a sequential series multijunction (SSM)-DSC and one of the highest known three subcell photovoltage was attained for any solar-cell technology (3.34 V, > 1.0 V per subcell). The next generation of high voltage dyes was synthesized exchanging the Benzothiadiazole (BTD) bridge with thienopyrroledione (TPD) to access more positive potentials. Higher photocurrent (up to 3.5 mA/cm2), and a higher power conversion efficiency (up to 2.9 %) than a BTD analogue while retaining comparable photovoltages (~1.3 V versus ~1.4 V) was obtained. Another way to power catalysis is to use sunlight directly to photoexcite a catalyst or a photosensitizer to provide energy to reduce CO2 to many substrates including CO or HCO2-. Five ruthenium catalysts were synthesized, evaluated photocatalytically, and found to facilitate self- sensitized CO2 reduction to form CO. The best catalyst of the series reduces CO2 to CO with 33,000 turnover numbers (TON), one of the highest TONs for a self-sensitized system. Furthermore, the selective formation of CO versus HCO2- is presumed to be the result of catalyst design. To better understand the selectivity of products in this reaction, the choices of solvent, electron and proton source, photosensitizer, and catalyst were evaluated. Highly selective catalysts for CO or HCO2– were found to change selectivity depending on its environment. This highlights the importance of considering reaction conditions before assigning selectivity to an inherent molecular design property.

Available for download on Wednesday, August 31, 2022

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