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
License
This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 International License.
Recommended Citation
Danladi, Fahad Ibrahim, "BAND GAP ENGINEERING IN TERNARY OXIDES AND SULFIDES: A ROUTE TO NEW PHOTOELECTRODES FOR SOLAR ENERGY CONVERSION" (2023). Chemistry & Biochemistry Dissertations. 237.
https://mavmatrix.uta.edu/chemistry_dissertations/237
Comments
Degree granted by The University of Texas at Arlington