Síntese e aplicação de compósitos baseados em sulfetos metálicos, estruturas de carbono e nitretos em supercapacitores de alto desempenho

• Ano de defesa: 2020
• Autor(a) principal: Rubens Lucas de Freitas Filho
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICX - DEPARTAMENTO DE QUÍMICA; Programa de Pós-Graduação em Química; UFMG
• Palavras-chave em Português: Compósitos; Óxido de grafeno (GO); Sulfetos metálicos (Ni/Co); Nanotubos de carbono helicoidais; Supercapacitores; Química inorgânica; Grafeno; Nanotubos de carbono; Capacitores; Sulfetos
• Link de acesso: http://hdl.handle.net/1843/33979

The present work consisted in the development of composites using graphene oxide as matrix (GO) to be applied as supercapacitor electrodes. Supercapacitors are electrochemical energy storage devices that can store large amounts of energy (charge) and can release this stored energy quickly, being applied in several areas of society. The development of composites was based on the improvements of charge storaged of the electrode, and for this purpose the behavior of several charges added to the GO matrix was studied, with these charges being carbon nitride (g-C3N4), boron nitride (BN), helical carbon nanotubes (h-CNTs), mesoporous carbon, and metallic Ni and Co sulfides. The GO matrix was obtained through the oxidation of mineral graphite by the modified Hummers method. The composites were obtained by the solvothermal method in which the amount of 20% w/w of load was fixed to matrix. The composites were characterized by the techniques of X-Ray Diffraction (XRD), Thermogravimetric Analysis (TG), Raman Spectroscopy, Scanning and Transmission Electron Microscopies (SEM / TEM), X-ray Spectroscopy by Dispersive Energy (EDS), Cyclic Voltammetry, charge-discharge curves and nitrogen adsorption and desorption isotherms. The specific surface area was obtained using the BET method. Through the characterizations performed it was possible to observe the formation of GO with few layers, and that it was reduced, leading to the formation of reduced graphene oxide (rGO), during the preparation of the composites by the solvothermal method. Through electrochemical characterization, the composites showed a purely capacitive behavior, operating by the double layer electrical mechanism, in which the rGO/CoNiS, rGO/h-CNT/CoS, rGO/CoS and rGO/h-CNT systems showed specific capacitance of 292, 173, 150 and 136 F.g-1 respectively. The composites showed improvements in their specific capacitances when compared to the GO matrix, and showed to be promising candidates to be applied as electrodes for supercapacitors.