- Title
- Hydrothermal carbonization for electrochemical capacitors: synthesis, characterization and nitrogen doping
- Creator
- Latham, Kenneth Gerard
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Hydrothermal carbonization has been gaining significant interest over the past ten years as a low temperature, environmentally friendly method of converting naturally occurring carbon containing precursors (e.g, glucose, cellulose) into valuable carbon materials. In addition to this, the doping of carbon materials is relatively easy under hydrothermal carbonization, as the dopant of choice can be simply added to the hydrothermal solution prior to carbonization. The overall purpose of this thesis was to examine the resultant material from hydrothermally carbonizing sucrose, with or without a nitrogen dopant, specifically for the purpose of producing enhanced carbon materials for electrochemical capacitors. The introduction chapters will examine the history and current understanding of both hydrothermal carbonization and electrochemical capacitors. Sucrose was chosen for the hydrothermal precursor due to its low cost, high rate of reaction and lack of examination in the literature. It was found that nitrogen level of 9.4 at% could be incorporated into the hydrothermal structure using a 0.2 M NaOH + 0.2 M (NH₄)₂SO₄ + 0.2 M sucrose hydrothermal solution. The hydrothermal carbons were thoroughly tested using FTIR, EA, XPS, NMR, NEXAFS, SEM and electrochemical methods. There were minimal differences between sucrose and other hydrothermally carbonized saccharides reported in the literature in regards to both the surface and bulk structure. The surface of the hydrothermal carbons from sucrose contained a wide variety of oxygenated functionalities (ketones, hydroxyls, carbonyls), whereas the bulk displayed the predominate furan structure that had previously been identified. The addition of nitrogen formed pyrroles, pyridines, imines, amides and imidazoles within the structure, while amines were only found on the surface. To the best of our knowledge, NEXAFS has not been applied to hydrothermal carbon and this is the first reported examination of hydrothermal carbon utilizing that technique. The hydrothermal carbon was also heat treated and activated for use in electrochemical capacitors, a maximum capacitance of 303 F g-1, was achieved with non-doped hydrothermal carbon activated with H₃PO₄ at 800°C. Step potential electrochemical spectroscopy was used to further examine the electrochemical properties of these activated hydrothermal carbons and, to the best of our knowledge, this is the first reported case of using this technique on activated hydrothermal carbon. The SPECS measurements indicated a relationship between oxygen and nitrogen groups on the surface, in that diffusion limited reactions (pseudocapacitance) increased with decreasing oxygen content. This suggested that oxygen functionalities inhibit the ability for nitrogen to contribute electrochemically, a finding that had not previously been reported.
- Subject
- hydrothermal carbonization; electrochemical capacitors; NMR; NEXAFS; Hydrochar; SPECS; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1315648
- Identifier
- uon:22981
- Rights
- Copyright 2016 Kenneth Gerard Latham
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Abstract | 777 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 8 MB | Adobe Acrobat PDF | View Details Download |