Danhua Yan

Type

Text

Type

Dissertation

Advisor

Liu, Mingzhao | Venkatesh, T.A. | Nam, Chang-Yong | Stavitski, Eli

Date

2017-12-01

Keywords

Materials science | Chemistry | Chemistry, Physical and theoretical

Department

Department of Materials Science and Engineering

Language

en_US

Source

This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.

Identifier

http://hdl.handle.net/11401/78271

Publisher

The Graduate School, Stony Brook University: Stony Brook, NY.

Format

application/pdf

Abstract

Driven by a strong desire for clean and renewable fuel, effective methods of hydrogen production have been sought after for a long time. Solar water splitting within a photoelectrochemical (PEC) cell has been one of the most promising methods. The key component of a PEC cell, the semiconductor photoelectrode, is responsible for carrier generation through light absorption, which initiates redox reactions in water to produce hydrogen and oxygen. An optimal photoelectrode is believed to meet these requirements: a small semiconductor bandgap for visible solar light absorption, suitable band positions that straddle the water re-dox potentials, and high conversion efficiency of photocarriers to hydrogen fuels. To date, however, no pristine semiconductor has been found to fulfill the needs. In this dissertation, zinc oxide (ZnO) and hematite (alpha-Fe2O3) has been extensively studied as candidate materials for photoanode applications. ZnO is an n-type semiconductor that with a wide band gap of 3.37 eV (corresponding to the absorption of ultra-violet light) and outstanding electronic properties. Hematite as an n-type semiconductor with advantages such as vast abundance in earth's crust, low cost, robustness, and a suitable band gap of 2.0 eV (corresponding to the absorption of visible light). Pristine ZnO and Fe2O3 alone as photoanodes are still far beyond satisfactory, leaving much to be investigated and improved. Various efforts have been made to advance the performance of pristine semiconductors, such as tuning the morphology via various fabrication methods, developing core-shell hetero-structures for improved robustness and photo-catalytic behaviors, and engineering the bandgap through doping and surface modifications. In addition to improving the performance of the photoanodes, high-quality thin films synthesized by pulsed laser deposition are treated as model systems to unravel the photocarrier dynamics and mechanisms. | 129 pages

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