Preparação e caracterização de eletrodos a base de óxido de grafeno reduzido in situ para aplicação como supercapacitores

• Autor(a) principal: Gomes, Oto Leonardo Reis
• Data de Publicação: 2017
• Outros Autores: [e-mail]
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/18915
• topic: Graphene oxide; Electrodes; Capacitance; Electrochemical techniques; Spraying; Eletrodos; Supercapacitor; Óxido de grafeno; Pulverização; Capacitância; Testes eletroquímicos; ENGENHARIAS::ENGENHARIA QUIMICA::TECNOLOGIA QUIMICA

This work presents a study on the obtainment of reduced graphene oxide (RGO) electrodes and their potential application as a supercapacitor. These electrodes were produced depositing graphene films on conductive substrates in two steps: production of GO and the deposition of RGO on the electrode. In sequence, it was made the structural and morphological characterization of the GO, the film and the evaluation of the electrochemical performance of the electrode. GO was prepared by the Hummers method and characterized by X-ray diffraction (XRD), Fourrier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Laser Raman spectroscopy (LRS). The capacitive behaviour was studied by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS) in 1 mol L-1 KOH aqueous solution. FTIR and LRS results confirmed the introduction of oxygen groups in graphite structure and the formation of GO. XRD analyses showed a high oxidation degree of the graphite and, SEM analyses showed the formation of oxide sheets with morphology similar to wrinkled paper. Subsequently, it was evaluated two methodologies of in situ reductions of GO over an electrolytic copper substrate: immersion and spraying. The electrodes produced by immersion were not uniform, while those produced by spraying showed an entirely coated surface. XRD analyses confirmed GO’s reduction, whereas LRS results showed the presence of sp3 hybridized carbon structures. Moreover, it was noted, by SEM, the deposition of few sheets of RGO and the presence of structures with morphology similar to copper oxide (I). As a function of higher uniformity, the electrodes produced by spraying were evaluated by electrochemical tests. The capacitance per area values obtained by CV varied between 117 and 253 mF cm-2, at a scan rate of 20 mV s-1, and showed capacitance retention values between 51 and 94% after 10 voltammetry cycles. The results of capacitance obtained by chronopotentiometry were between 600 and 720 mF cm-2 at an applied current of 2 mA. Capacitance retention of these electrodes varied between 77 and 86% after 10 galvanostatic charge/discharge cycles. In both techniques, the values found were similar to those normally reported in the literature, indicating potential application as a supercapacitor. The resistance values, obtained through the simulation of the EIS data using an equivalent electric circuit, varied between 9,3 and 42 Ω . These results indicate that electrodes behaved like a supercapacitor. Thus, the research of the production process and properties of RGO electrodes allowed the improvement of the knowledge of these materials and in the development of a device with a high capacity of energy storage.