الفهرس | Only 14 pages are availabe for public view |
Abstract The study aims at the preparation and characterization of nanostructured carbon-based materials for supercapacitors. These materials impely the synthesis of electrodes that are incorporateed with siver and some of the transition metals oxides such as (Titanium oxide). Chemical and / or electrochemical methods of synthesis were explored. The main objectives of this study were concerned with:- • Development of supercapacitor electrodes with long lifetime. • Acheiving high energy and power densities. The content of the thesis can be summarized as: I) The introduction includes a short outline of the importce of The energy in our life and its applications in devices, such as cell phones, pagers, stand-by power systems, and electric/hybrid vehicles. Previous studies on the graphene and its use in supercapacitors related to the present investigation are reviewed and discussed. II) The experimental part includes the materials, reagents used and the methods of preparation. The techniques and apparatus are also outlined, as well as, the experimental conditions associated with processes.III) The results obtained are explained and interpreted. In chapter 3. The main achievements and views discussed can be presented as follows: 1) characterization of spongy graphene oxide (SGO), reduced graphene oxide (RGO), functionalize of grapheme oxide (FGO) and Functionalized graphene (FG): characterization of functionalized graphene by FESEM, TEM, XRD, UV, FT-IR, TGA, and Ramen spectroscopy. Study of electrochemical behavior using cyclic voltammetry and chornopotentiometry. 2) characterization of functionalized graphene (FG-Ag): Characterization of functionalize graphene decorated with Ag NPs FG-Ag by FESEM, TEM, XRD, UV, FT-IR, TGA, EDX and Ramen spectroscopy. Study of the electrochemical behavior using cyclic voltammetry and chornopotentiometry. The composition of graphene and silver nanoparticles containing 100:15 ratio in the composite was found to have maximum synergistic effect resulting in the highest capacitive property than the other ratios.3) characterization of Functionalized graphene (FGTiO2H) Characterization of functionalized graphene by FESEM, TEM, XRD, FT-IR, EDX and Ramen spectroscopy. Study of the electtochemical behavior using cyclic voltammetry and chornopotentiometry. The composition of graphene and hydrogenated Titanium nano tubes containing 100:20 ratio in the composite was found to have maximum synergistic effect resulting in the highest capacitive property than the other ratio. 4) characterization of Functionalized N/P co-doped graphene. Characterization of N/P co-doped graphene by FESEM, TEM, XRD, UV, FT-IR, TGA, and Ramen spectroscopy. The study of Electrochemical behavior using cyclic voltammetry and chornopotentioetry. In conclusion, A green method is demonstrated to prepare 3-dimensional (3D) network crinkly sheets of adeninefunctionalized spongy graphene (SFG), The synthesized materials have been evaluated as supercapacitor materials in 0.5 M H2SO4 using cyclic voltammetry (CV) at different potential scan rates, and galvanostatic charge/discharge tests at different current densities. The SFG electrodes showed a maximum specific capacitance of 333 F/g at a scan rate of 1 mV/s with excellent cycling retention of 102% after 1000 cycles at 200 mV/s. The energy density was 64.42 Wh/kg with a power density of 599.8 W/kg at 1.0 A/g. Those figures of merit are much higher than those reported for graphene-based materials tested under similar conditions. The observed high performance can be related to the synergistic effects of the spongy structure and the adenine functionalization. The nanocomposite based on Ag nanoparticles decorated FG was synthesized successfully by simple and a green method The synthesized materials have been evaluated as supercapacitor materials in 0.5 M H2SO4 using cyclic voltammetry (CV) at different potential scan rates, and galvanostatic charge/discharge tests at different current densities. The FG-Ag2 electrodes showed a maximum specific capacitance of 567 F/g at a scan rate of 1 mV/s with excellent cycling retention of 100.5% after 1000 cycles at 200 mV/s. The energy density was 89.32 Wh/kg with a power density of 540 W/kg at 0.4 A/g. The observed high performance can be related to the synergistic effects of the spongy structure and the adenine functionalization with silver nanoparticles.The nanocomposite based on of the Functionalize graphene– HydrogenatedTiO2 hybrid nanostructure synthesized successfully by usind Anodization and hydrothermal process, showed a maximum specific of 401 F/g at a scan rate of 1 mV/s and 100.2% of the initial cycle, indicating the excellent cycling stability of the FGHTIO2 electrodes. The energy density can reach up to 78.66 Wh/Kg with a power density of 466.9 W/kg at 0.8 A/g. Note that 40.5 Wh/Kg and 1773.7 W/Kg remain there even at a current density as high as 3 A/g. The synthesis of heteroatom doped graphene nanosheets, showed a maximum specific of 499/g at scan rate of 1 mV/s and excellent cycling retention 101% after 1000 cycles at 200mV/s with high energy density 98.58Wh kg- 1. To the best of our knowledge the capacitance of (N/PGNS) would be a promising material for supercapacitors. Further, the prepared single pot method is easy and The improved electrochemical performance is due to the combination of all heteroatoms the co-doping of (P and N) graphene nanosheets synthesis. |