Three dimensional graphene composites for energy storage applications

Abstract

The aim and objectives of this work is the development of a three dimensional graphene foam (GF) electrode for energy storage applications and study the electrochemical properties of the electrodes modified with different metal/metal oxides nanostructures. The GF was synthesised by chemical vapor deposition (CVD) and various metal/metal oxides were grafted on the surface of the GF by various method such as microwave irradiation (MW), aqueous chemical growth (ACG), successive ionic layer adsorption and reaction (SILAR) and reflux method. The interaction and formation mechanism between the GF and the metal/metal oxides nanostructures were all discussed. The obtained composite materials were characterized by Raman spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM). The composite materials synthesised revealed different morphologies as seen by the different characterization techniques. The major interest in the GF for electrochemical capacitors is due to its unique structure, good conductivity and large surface area which offer the possibility for deposition/adsorption of metal/metal oxides for practical applications. The composite synthesised were all investigated as electrode for electrochemical capacitors in different electrolytes and tested with different operating voltages vs silver/silver chloride (Ag/AgCl). The electron kinetics of the composite materials was studied and all show excellent electrochemical performance. All the results have clearly shown and demonstrated the great potential of three dimensional composite based novel electrode materials for energy storage applications. I hereby declare that the matter embodied in this thesis entitled “Three dimensional graphene composites for energy storage applications” is the result of investigations carried out by me under the supervision of Prof. N. Manyala, in the Physics department at the University of Pretoria South Africa and that it has not been submitted elsewhere for the award of any degree or diploma. In keeping with the general practice in reporting scientific observations, due acknowledgement has been made whenever the work described is based on the findings of other investigators.