ORCID Identifier(s)

0009-0000-2346-974X

Graduation Semester and Year

2023

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Krishnan Rajeshwar

Abstract

In recent years, there has been a growing interest in semiconductor photoelectrodes that can effectively split water into hydrogen and oxygen using sunlight. However, there is currently no known material that is efficient enough to be used for commercial purposes. Photoelectrodes currently have an efficiency of less than 10% in converting water under visible light irradiation. There is a need to develop an efficient semiconductor photoelectrode for photoelectrochemical water splitting that is both chemically stable and affordable, composed of earth-abundant elements and capable of operating under visible light. Metal oxides are considered promising photoelectrode materials due to their low cost, stability against oxidation, and tunable band gaps. This study aims to expand the library of metal oxide and sulfide materials that could potentially be used as photoelectrode materials for photoelectrochemical (PEC) water splitting. This research briefly introduces the photoelectrochemical technique and reviews various methods to tune the optoelectronic properties of semiconductors for solar fuel generation, focusing on improving the performance of visible-light active PEC materials. Through a combination of theory and experimentation, the potential of ternary metal oxide semiconductors in the A-Cu-V-O family (A= alkaline earth metal) was evaluated for PEC water splitting. By successfully incorporating 10% alkaline earth metals into α-CuV2O6, the optical band gap and PEC activity could be fine-tuned. Finally, we successfully synthesized alkaline earth metal vanadates, namely Mg2V2O7, Ca2V2O7, and Sr2V2O7, as well as quaternary vanadates of copper and alkaline earth metals through a solution combustion synthesis method that is both time- and energy-efficient. These metal oxide semiconductors have the potential as photoelectrode materials for PEC water splitting. We used both theory and experiment to investigate the effect of alkaline earth metal substitution on the crystal structure, optoelectronic properties, and PEC properties of copper pyrovanadate. Additionally, we were able to synthesize two polymorphs of ternary praseodymium sulfide, cubic NaPrS2 (C) and rhombohedral NaPrS2 (R), via the solid-state method. Notably, we successfully produced the layered R-NaPrS2 for the first time through slow cooling to room temperature.

Keywords

Band gap engineering, Photoelectrochemistry, Solid state

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Available for download on Thursday, August 01, 2024

Included in

Chemistry Commons

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