Síntese e caracterização de nanotubos de dióxido de titânio dopado e revestidos com dióxido de rutênio para aplicações como supercapacitores

• Ano de defesa: 2018
• Autor(a) principal: Menezes, Wallas Teixeira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Mato Grosso; Brasil; Instituto de Ciências Exatas e da Terra (ICET); UFMT CUC - Cuiabá; Programa de Pós-Graduação em Química
• Palavras-chave em Português: TiO2NT; RuO2; Supercapacitor; Dopagem; Revestimento sonoquímico; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA; Doping; Sonochemical coating
• Link de acesso: http://ri.ufmt.br/handle/1/4225

Application of highly ordered titanium dioxide (TiO2NT) nanotubes in energy storage devices, such as supercapacitors, has been attractive and of great interest due to its large surface area and better transport of cargo due to its vertical orientation and one-dimensional nature of ballistic transport. As can be observed in the literature one can easily control the properties of TiO2NT by doping or coating the tubes with different materials, so that to improve the capacitive properties can be added to the nanotubes materials that have high surface capacitances, such as, RuO2, Mn3O4, among other materials. In this work, TiO2NT-L with continuous voltage (60 V) and TiO2NT-P with pulsed voltage (60-20 V) were synthesized by means of the electrochemical anodization technique in electrolyte containing glycerol, 0.25% of NH4F and 10% of H2O with anodization times of 12 h, and then a heat treatment was applied at 450 ° C. Doping and filling processes were promoted in the nanotubes with ruthenium oxide. Doping was performed during the anodizing step where a ruthenium precursor solution of 1 x 10-3 mol L -1 was added, the coating was promoted with the aid of an ultrasonic bath where the pre-prepared nanotubes were placed in a solution of 1 x 10-3 of RuCl3 and sonicated for 5 min, after that procedure the electrodes were brought to muffle and again calcined at 450 °C. Capacitance and electroactive area measurements were performed for all synthesized electrodes. The electrochemical measurements were promoted using the techniques of cyclic voltammetry, charge-discharge galvanostatic with 5000 cycles of charge-discharge and electrochemical impedance with adjustment using the methodology of transmission lines. For structural and morphological characterization, measurements of X-ray diffraction and FEG microscopy were performed. Preliminary electroarea experiments have shown that smooth nanotubes have larger areas than pulsed nanotubes, increasing their interest in modifying nanotubes. Through the voltammetric results it can be seen that the pure TiO2NT (TiO2NT-L and TiO2NT-P) did not present faradáicos processes indicating capacitive currents, common to electric double layer capacitors. Nanotubes with ruthenium addition (TiO2NT-L/DopRu, TiO2NT-P/DopRu e TiO2NT-L/PreRu) showed oxidation-reduction reactions common to pseudocapacitors. By means of the galvanostatic charge-discharge data, it was possible to calculate the capacitance values during the discharge process (Cd), and these showed that even after 5000 charge-discharge cycles the capacitance values did not decrease for any of the studied nanostructured materials. It was also observed that the Cd of the TiO2NT-L/DopRu was the largest of the studied electrodes, around 320% higher than the Cd of theTiO2NT-L. Three transmission lines were tested for the adjustments of impedances, and the R-0-Rq transmission line promoted adequate adjustment to the experimental data with good statistical and electrochemical concordances. The TiO2NT-L/DopRu electrode was of great interest for applications as supercapacitors because it presented high capacitance values and great stability even after 5000 loading and unloading cycles.