Development of Advanced Electrode Material for Supercapacitor Applications

Abstract

This aim of the thesis work was to provide an insight into the field of electrochemical energy storage in supercapacitors. Two different biomasses, bamboo bagasse and apple peel fiber were chosen as the raw materials for the preparation of supercapacitor electrode material. Three different activating agents like Potassium hydroxide (KOH), Potassium hydroxide with Potassium ferricyanide K3[Fe(CN6)] and Zinc chloride (ZnCl2) were chosen for the activation of the carbon obtained from the above raw material. The activation of carbon with KOH and KOH+K3[Fe(CN)6] was carried out at the controlled temperature and gas flow rates which resulted in production of nanoporous carbon with partially graphitic nature. A novel preparation technique, combined hydrothermal with chemical activation was carried out for the preparation of zinc-catalyzed activated carbon from bamboo bagasse. The physico-chemical properties of various biomass-derived graphitic nano-porous carbons were characterized by XRD, FTIR, TGA, Raman spectroscopy, SEM, TEM and electrochemical measurements. It was an interesting observation that the activation with the iron salts played a significant role in the formation of graphitic structures. The graphitic nanoporous carbonaceous materials showed high specific surface area of 1360 m2g-1, low impedance, large pore volume and high specific capacitance. The carbon activated in the presence of ZnCl2 has the highest capacitance of 180 Fg-1 in aqueous medium and 153 Fg-1 in the non-aqueous medium. This contemporary- novel method to synthesis of nano-porous carbon epitomizes a great potential for apparent and diversified applications in energy storage materials. newlineNext part of the study deals with the in-situ electrochemical hydrogen storage on the heteroatom (nitrogen) doped carbon that enhanced the electrochemical performance in the supercapacitor applications. There are only few studies on the electrochemical in-situ hydrogen newlinestorage technique, especially for N-doped graphene. Nitrogen-doped graphene was synthesized by an easy and simple hydrothermal method. This cost-effective method is promising for electrochemical hydrogen storage. A thorough study of structural analysis and electrochemical behaviour of graphene and nitrogen-doped graphene was conducted. The analysis confirmed that the product has a highly crystalline nitrogen enriched graphene structure and the material has an excellent hydrogen storage capacity. The nitrogen-doped graphene as anode material for energy storage showed high specific capacitance, conductivity and superior rate performance for electrochemical supercapacitor. The 3D structured porous graphene nanoball clusters prepared was characterized. The 2D peak formation in Raman spectra was compared to confirm the effective preparation of graphene nanoball and high performance supercapacitor applications from apple peel fibre based biomass carbon. The prepared graphene nanoball was subjected to physico-chemical characterization like surface morphology, crystal nature, functional group identification and atomic arrangement, etc. In the Raman spectrum, the 2D peak was obtained at 2670 Cm-1 which confirmed the graphene formation. However, no clear explanation could be provided for the graphene formation from the biomass derived carbon. Electrochemical performances of the material was evaluated in aqueous 6M KOH as the electrolyte and compared with the commercially available high surface carbon of 2000-2500m2g-1. The maximum specific capacitance was shown by graphene nanoball (415 Fg-1) than that of the commercially available high surface carbon electrode material (270 Fg-1) at 1 Ag-1, respectively. Thus, this study provided a lead for the mass production of graphene which is a significant contribution in the production of materials for energy storage applications. newlineKeywords: Supercapacitor; Specific Capacitance; Double Layer; Apple Peel; Bamboo Bagasse; Energy Density; Power Density; Graphene; Nitrogen-Doped Graphene; Coulombic Efficeincy. newline