Award Date

2009

Degree Type

Thesis

Degree Name

Master of Science in Chemistry

Department

Chemistry

Advisor 1

Clemens Heske, Committee Chair

First Committee Member

David Hatchett

Second Committee Member

Dong-Chan Lee

Graduate Faculty Representative

James Selser

Number of Pages

89

Abstract

Solar energy is the most sustainable source of energy available. However, solar applications such as photovoltaic cells represent only a partial solution to weaning our dependence upon fossil fuels. Several methods of storing solar energy are currently being pursued, and chemical storage stands out as a promising option - combining design simplicity with high energy density, with hydrogen being particularly attractive because of its abundance and inherently clean nature. A monolithic Photoelectrochemical (PEC) device that produces hydrogen by electrolyzing water directly from sunlight has the benefit of utilizing "free" solar energy to drive the reaction.

Although α-Fe 2 O 3 (hematite) is a strong candidate for PEC applications with a bandgap of 2.2 eV, its conduction band minimum is generally believed to be positioned below the H + /H 2 reduction potential necessary for its use as a water splitting material. Additionally, the low charge carrier mobility of hematite implies that charge carrier recombination needs to be overcome. Despite this, α-Fe 2 O 3 is cheap and abundant, nontoxic and easily synthesized. Furthermore, several studies have shown that this material is particularly receptive to both n- and p-type doping - a solution that may address both the band edge position and charge mobility issues.

This thesis describes X-ray Photoelectron Spectroscopy (XPS) conducted at UNLV, Atomic Force Microscopy (AFM) imaging performed by Dr. Asanga Ranasinghe (also UNLV), Scanning Electron Microscopy (SEM) characterization by Arnold Forman and Alan Kleiman-Shwarsctein at the University of California, Santa Barbara (UCSB), and the synthesis process of α-Fe 2 O 3 samples grown by our collaborators Arnold Forman, Alan Kleiman-Shwarsctein, and Dr. Eric McFarland at UCSB. We describe the synthesis process and report our observations of Ti diffusion through the Ti/Pt substrate interface and of Fe 2 O 3 island growth due to high calcination temperatures. Furthermore, we identify contaminants incorporated into the samples, and correlate these findings with PEC sample performance.

Keywords

Energy storage; Hematite; Hydrogen production; Iron oxide; PEC; Photoelectrochemical hydrogen production; Platinum; Solar energy; Titanium; Water

Disciplines

Oil, Gas, and Energy | Physical Chemistry

Language

English


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