چكيده به لاتين
Given the rapid consumption of fossil fuels and the increasing environmental pollution resulting from their use, there is a growing global demand for the expansion of more efficient alternative energy sources. Consequently, the need for a more efficient energy storage system has become increasingly apparent. In this context, supercapacitors have garnered significant attention due to their high power density, longer cycle life, and rapid charge-discharge capabilities compared to traditional batteries and capacitors. However, the low energy density of supercapacitors limits their effectiveness. Therefore, our approach in this thesis focuses on enhancing the energy density of supercapacitors while maintaining high power density through the use of novel electrode materials. To improve the energy storage capacity of supercapacitors, we synthesized new nanocomposite electrodes consisting of reduced graphene oxide/vanadium tetrasulfide/cobalt oxide (Co₃O₄/VS₄/rGO-SDBS) via a hydrothermal method that requires no additives. The Co₃O₄/VS₄/rGO-SDBS@NF composite demonstrates a specific capacity of 2620 F g⁻¹ at a current density of 1 A g⁻¹, significantly higher than the 284 F g⁻¹ observed for the VS₄/rGO-SDBS@NF composite in a 6 M KOH solution. Furthermore, the resultant Co₃O₄/VS₄/rGO-SDBS@NF electrode exhibits excellent cycling stability, retaining 97.4% of its initial capacity after 5000 cycles. In summary, the use of a simple and accessible synthesis method, the absence of binders, a specific growth technique, and the achievement of a unique morphology with effective electrochemical performance result in significant improvements over recent studies. These findings provide a new perspective for the selection and synthesis of materials, as well as the design and construction of electrodes for supercapacitors as energy storage devices. In the subsequent phase, to enhance the performance of asymmetric supercapacitors, this electrode was employed as the positive electrode, while carbon cloth served as the negative electrode. Experimental analyses were conducted to investigate the effects of morphology, structure, specific surface area, and surface charge on electrochemical performance. The asymmetric supercapacitor (ASC) exhibits a specific capacity of 238.8 F g⁻¹ at a current density of 0.5 A g⁻¹, demonstrating capacity retention after 8500 charge-discharge cycles, indicative of effective electrochemical processes. Additionally, the ASC device shows an energy density of 74.6 Wh kg⁻¹ at a power density of 1500 W kg⁻¹. In the second part, the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite was synthesized. Due to its fully porous graphene structure and rapid redox reactions, this composite not only exhibits supercapacitive properties but also demonstrates photocatalytic performance for the degradation of rhodamine B dye. The ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite showed remarkable photocatalytic activity (99.86%) for the degradation of rhodamine dye in aqueous solution under sunlight and mercury lamp irradiation. Moreover, the supercapacitive behavior of the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite was investigated using cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques in a 6 M KOH electrolyte. The satisfactory performance of the ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ composite can be primarily attributed to the synergistic effects of ZnO/RGO/α-Fe₂O₃/ZnFe₂O₄ and the presence of RGO within this composite. The results of this study will contribute to determining the most efficient and cost-effective methods for dye removal from textile industry wastewater, as well as establishing this composite as an effective material for supercapacitor applications. Overall, the goal of this thesis is to present a novel approach for the design and development of new high-performance materials for dual applications, including their use as electrode materials in supercapacitors and as active materials in photocatalytic processes.
