Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemical and Environmental Engineering (ENAS)
First Advisor
Hu, Shu
Abstract
Due to the rising greenhouse gas emissions and increasing energy demand, efforts are urgently needed towards net zero emissions and beyond. Photocatalysts are promising technologies to not only achieve solar fuel production with zero emissions, but also can be integrated into carbon capture and utilization for negative emission. Photocatalysts, in the form of powder suspension or immobilized onto substrates as photocatalytic sheets, can potentially achieve low-cost solar fuel production due to its simplicity. However, its efficiency is still too low for any practical applications, and fundamental understanding on how photocatalysts operates under operating conditions are urgently needed to provide guidance on optimization and improvement. In this thesis, an overarching concept is the coevolution nature of photocatalysts. Coevolution means the concurring reductive and oxidative reactions at nanoscale proximity on photocatalyst surface. The overarching thrust is thus how to study and understand coevolution so that we can design photocatalysts with desired activities and better efficiency. In Chapter 2, charge separation in various types of photocatalysts are reviewed and categorized based on the electronic structure of photoabsorbers. Based on the classification, strategies and key parameters are identified and provided to achieve better charge separation. In Chapter 3, in aim to establish a photocatalyst/two-redox junction theory for describing photocatalyst operations, a kinetic model was established based on microscopic reversibility and detailed balance. Experimental characterization framework using gas-dependent open-circuit potential (OCP) measurements were established and the kinetic model was experimentally validated using this framework. In Chapter 4, as an extension of Chapter 3, hole quasi-Fermi levels of photocatalysts were probed using OCP measurements. This was achieved by first developing a hole-selective back contact and then depositing photoabsorbers on top of the back contact. The hole quasi-Fermi level measurements provided valuable information on state-of-the-art cocatalysts for oxygen evolution reactions (OER), such as IrOx and CoOx. In Chapter 5, the coevolution nature of photocatalysts was extended to CO2 reduction in bicarbonate solution, leveraging the short species transport between surface cathodic and anodic sites. This has important implications in integrated carbon capture and utilization (CCU), which can enable carbon neutral fuel production. In Chapter 6, a techno-economic analysis of a novel photocatalytic reactor was performed, and its feasibility was examined. Sensitivity analysis was performed, revealing that this new photocatalytic reactor is most sensitive to available light intensity, which is desirable as the system consists of abundant photocatalysts and low-cost reactor frames, and the process is only driven by solar radiation.
Recommended Citation
Yanagi, Rito, "Design Principles and Implementations Toward Particulate Solar Fuel Production With Carbon Capture and Utilization" (2024). Yale Graduate School of Arts and Sciences Dissertations. 1271.
https://elischolar.library.yale.edu/gsas_dissertations/1271
