Kim, Min A
(2021)
The Effects of Electrical and Mechanical Modulation on the Chemical Reactivity of Graphene.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Extreme surface to volume ratio of graphene makes graphene widely open to various reactions; chemistry of graphene is of great interest to fine-tune electronic, chemical, and mechanical properties of graphene, and a better understanding of the factors that impact its chemical reactivity is an invaluable part of graphene chemistry. In this dissertation, dynamic modulation of graphene properties and their effects on the chemical reactivity of graphene are investigated.
A brief background on the history, synthesis, and characterization methods of graphene is summarized in chapter 1. In chapter 2, how graphene interacts with ambient-found species under electrical doping was studied. Electrical doping has significant advantage over chemical doping with in-situ controllability. Static back gating resulted doping hysteresis, which we explained using a charge trapping/de-trapping mechanism.
Efficient electrical doping method was developed to further investigate its effects on the reactivity of graphene in chapter 3. Graphene was heated photothermally in air to ca. 240 ºC and monitored using Raman spectroscopy. Electrically doped graphene showed increased rate in the oxidation reaction. Density functional theory (DFT) calculations indicate that the activation barriers for O2 insertion and CO2 desorption decrease with an electric field. This is the first example of charge-doping induced reactivity enhancement in macroscopic-sized solid-state material.
In chapter 4, the mechanical modulation of graphene and its effects were investigated. Preliminary results suggested an enhanced electrochemical catalytic activity of graphene as well as the electrochemical oxidation itself. The catalytic role of graphene was further investigated and found that applied tensile strain of 0.2 % on a graphene electrode led to a 1~3 % increase of hydrogen evolution reaction (HER) current. Tensile strain increases HER activity while compressive strain decreases it. DFT calculations show increasing H atom adsorption energy with growing tensile strain, leading to a corresponding enhancement of current density in HER.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
8 October 2021 |
| Date Type: |
Publication |
| Defense Date: |
21 July 2021 |
| Approval Date: |
8 October 2021 |
| Submission Date: |
7 July 2021 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
191 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
graphene, 2D materials, reactivity, catalysis, oxidation, hydrogen evolution reaction, electrical modulation, electrical doping, mechanical modulation, strain engineering |
| Date Deposited: |
08 Oct 2021 20:22 |
| Last Modified: |
08 Oct 2023 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/41400 |
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