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Document Type

Thesis - University Access Only

Award Date

2014

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

First Advisor

Qi Hua Fan

Abstract

Energy storage is critical for future sustainable energy infrastructure. Among energy storage options, supercapacitors can be important due to their large capacity, fast charge/discharge rates, and stability. For example, supercapacitors combined with batteries can make electric cars more efficient and can offset the intermittency of renewable energy sources, such as photovoltaics and wind. However, state-of-the-art supercapacitors use expensive synthesized carbon nanomaterials to store electricity. Environmentally friendly, sustainable, and inexpensive bio-inspired carbon materials, such as biochar have recently been shown to have potential for supercapacitors. A critical step in using biochar is activation which creates porous microstructures with large surface area. This requires high-temperature baking for several hours in an inert atmosphere using a strong base and accounts for over 50% of the cost of carbon electrodes. The objective of this research was to use plasma treated biochar electrodes to fabricate supercapacitors. Oxygen plasma is highly reactive to glassy carbon, which exists in biochar and can form of porous structures with active surfaces. Oxygen plasma was used to activate yellow-pine biochar and resulted in a specific capacitance of 171.8 F/g versus 60.4 F/g for untreated and ~99.5 F/g for chemical activation. Brunauer–Emmett–Teller (BET) measurements indicated that chemical activation created a larger surface area with uniform micropores (~2 nm), while oxygen plasma activation created significant mesopores (2 – 50 nm) as well as micropores and large macropores. Although chemical activation led to a larger surface area versus the plasma activation, the ions had limited accessibility to the chemically activate micropores versus the larger pores in the plasma activated biochar. This is first report of oxygen plasma activation of biochar. It can provide a low-cost, low-temperature, non-toxic, and highly efficient way to activate biochar for supercapacitors. Future research should include identifying the plasma chemical reactions and chemical composition of the resulted materials.

Library of Congress Subject Headings

Biochar
Energy storage
Supercapacitors
Electrodes, Carbon

Description

Includes bibliographical references (pages 79-92)

Format

application/pdf

Number of Pages

104

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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