| dc.description.abstract | Bio-derived carbon-based-supercapacitor electrodes present an economical solution as sustainable sources for energy storage. Serious knowledge gaps exist for bio-derived carbon electrodes in terms of causes of largely unknown surface chemistry, poor volumetric energy density, and uneven pore structure and distribution which adversely affect electrochemical performance, cost, and scalability. To date, it is not yet clear how the electrochemical performance is affected by chemical composition and molecular structure in bio-derived carbon. In addition, the relation of surface morphology and microstructure with electrochemistry has not been established. This research attempts to fill those knowledge gaps with new understanding of the effects of bio-derived carbon structure and morphology on electrochemical performance.
The goal of this research is to obtain new knowledge in terms of biomass electrochemistry to design and engineer sustainable and high-performance electronics. To reach the goal, this research will investigate the structural and morphological characteristics of lignin based materials and their effects on electrochemical performance as electrodes. Specifically, it is intended to understand 1) how the presence of different chemical structures and 2) particle morphologies of lignin affect the charge storage and cycle life of a quasi solid-state supercapacitor. To carry out the research, experimental approaches combined with theoretical analysis will be conducted. Specific tasks include fabrication, assembly, test, analysis, and optimization of supercapacitor electrodes using various bio-derived lignin differing in structural identity and morphological features.
Lignin varying in structural identity (alkaline lignin (AL), lignosulfonate (LS), and dealkaline lignin (DAL)) and morphology (micro-fiber lignin and nano-spherical lignin) are used to evaluate electrochemical behavior. Specific capacitance, retention, impedance, energy, and power density results are compared and analyzed.
This research generates new knowledge in understanding lignin electrochemistry that will aid in significant advances in the future design of bio-derived carbon based electrochemical devices. Novel synthesis processes for electroactive lignin micro and nanoparticles will be developed. Unique design of lignin supercapacitors will be accomplished and improved to attain high performance.
This thesis contains seven chapters. Following the background introduction in Chapter I, the motivation and objectives of this work are presented in Chapter II. This is followed by the research on structural investigation of micro-lignin fibers: electrochemical behavior of alkali lignin fibers (Chapter III), transition metal oxide (NiWO₄) nanoparticles doped lignin (Chapter IV), and effects of hydrothermally impregnated MnO₂ particles on lignin fibers (Chapter V). Structural investigation on nano-spherical lignin particles is covered in Chapter VI. Finally, a summary and commentary on future directions of research are provided in Chapter VII. | |
