Doctor of Philosophy (PhD)
Water scarcity threatens the lives of millions of people worldwide. It is imperative to improve the energy efficiency and affordability of water treatment methods to avoid a looming water-energy crisis. To meet this challenge, I have pursued research on the use of sunlight—our most reliable and abundant source of energy—to drive water treatment through photocatalysis. I explored the literature and found gold-semiconductor materials to hold promise for harvesting sunlight and catalyzing the breakdown of waterborne contaminants. Initially, I designed a novel optical cavity with gold (Au) nanoparticles on a zinc oxide / titania (TiO2) / aluminum film stack and enhanced the absorption of visible light by a factor of 5, extending the lifetimes of hot carriers in Au up to >2 ps. This improved the hot carrier transfer to zinc oxide and led to the generation 3 times more reactive oxygen species, which are used to disinfect water. I then pivoted to the use of ultraviolet (UV) light and developed a porous TiO2 photocatalyst coated with μM hydrogen peroxide (H2O2) with such, the system is suited to generate H2O2 on-sight for water treatment facilities that implement UV/H2O2 advanced oxidation processes in their treatment train. I also observed an unexpected activity of these Au-TiO2 films in electron-donor solutions and conducted fundamental studies on various TiO2 morphologies to explain the anomaly. Finally, I created a novel dual-porous photocatalyst of TiO2 on quartz fiber supports to provide photocatalytic activity under germicidal UV radiation. This technology overcomes mass and optical transport limitations that plague the field of immobilized photocatalysis and degrades a model contaminant, Rhodamine B, with a commercially viable energy efficiency. I further explored ways to optimize the dual-porous system through tuning of photoreactor design, photocatalyst loading, and UV intensity. As it currently stands, this technology outperforms traditional UV/H2O2 processes for decontamination of model wastewaters and holds the potential for near-term application within water reuse treatment systems.
Willis, Daniel, "Gold-Semiconductor Photocatalysts for Water Treatment Under Visible and Ultraviolet Light" (2021). LSU Doctoral Dissertations. 5517.
McPeak, Kevin M.
Available for download on Friday, March 15, 2024