چكيده به لاتين
In recent years, the utilization of energy storage systems such as batteries, fuel cells, and electrochemical capacitors has attracted a great deal of interest in applications such as transportation systems and portable systems. Regarding the growing human need and demand for energy, the improvement of energy storages with high energy density, and more power, reduced production costs, and increase the lifespan of these devices is mandatory. Electrochemical supercapacitors, as one of the types of electrochemical energy storage systems, have a higher energy storage capacity compared to conventional capacitors and a higher power density than batteries. These capacitors with unique features such as high charge/ discharge rate, more charge/discharge cycles, and a wide operating temperature have been utilized in some applications such as electric and hybrid vehicles, air transport, and electronics industry, as well as in smart grids. In the current research, using chemical methods as well as the plasma enhanced physical vapor deposition (PECVD), various types of electrodes were fabricated by carbon-based materials such as carbon nanotubes and graphene sheets on steel substrates have been prepared. To prepare the graphene-based electrode, graphene oxide was first prepared by the modified Hammers method. The graphene oxide solution was thermally converted to graphene. The synthesized graphene oxide was characterized by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD) techniques The presence of two D band in 1312 cm-1 and G band in 1584 cm-1 in Raman spectrum, are related to the first-order defect and diffraction of the E2g mode of graphene sheets, respectively and confirmed the synthesis of graphene oxide sheets. Graphene electrodes were prepared by the slurry method on the steel substrate. Two methods were used to fabricate carbon nanotube electrodes. In the first method, electrodes based on carbon nanotubes were prepared by the slurry method on stainless steel current collector. In the second method, the PECVD method was used for the growth of carbon nanotubes on a steel substrate. To obtain such an electrode, the fundamental parameters in the growth of nanotubes were optimized. The grown nanotubes were characterized using Raman and XRD and SEM techniques. Electrochemical experiments, including cyclic voltammetry and galvanostatic charge and discharge tests, were performed on prepared electrodes of graphene sheets and carbon nanotubes. The results of electrochemical experiments demonstrated that the electrode fabricated by the direct growth of carbon nanotubes on a stainless steel substrate had a capacity of 16000 mF/g. In comparison, the capacity of the electrode prepared by graphene was 330 mF/g, and the electrode made of carbon nanotubes by the slurry method showed only 250 mF/g. Rectangular voltammograms achieved by cyclic voltammetry at different scanning rates for the electrode fabricated by the physical growth of carbon nanotubes on a steel substrate depicted the ideal capacitive behavior of the electrode and the stability of the electroactive material on the electrode surface.
