DESENVOLVIMENTO DE ELETRODOS À BASE DE CARBONO CERÂMICO MODIFICADOS COM NANOPARTÍCULAS DE HIDRÓXIDO DE NÍQUEL APLICADOS NA ELETRO-OXIDAÇÃO DE ALCOÓIS EM MEIO ALCALINO

Abstract

In this thesis a new class of chemically modified electrodes, carbon ceramic electrodes (CCE), was developed and applied produced by a sol-gel method. Different parameters for the synthesis of ecc were studied. Some factors such as the type of precursor and catalyst, directly influence the conductive properties, mechanical and morphological ecc, and these are reflected in the electrochemical response. Such responses were analyzed for the anodic peak current (Ipa) and the potential change (?E) of the respective cyclic voltammograms in presence of potassium ferrocyanide. Analyzing the set of results obtained from cyclic voltammetry a higher reversibility and anodic peak current was observed for the electrode synthesized with a greater proportion graphite/precursor in alkaline conditions as a precursor possessing the Methyltrimethoxysilane (MTMS). The electrode formed by this synthetic route was more hydrophobic, when compared to the precursor tetraethylorthosilicate (TEOS) minimizing background current, thus increasing the sensitivity of the electrode. It is suggested that the obtained material presents a porous morphological structure, providing higher reversibility and better definition of voltammetric peaks. These electrodes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Xray diffraction (XDR). The electrode with the best electrochemical response was then modified with nickel hydroxide nanoparticles and applied as anodes for electro-oxidation of alcohols in alkaline medium. High values of current density 67, 77, 72 and 99 mA were observed for methanol, ethanol, ethylene glycol and glycerol, respectively, using only a 10% (w/w) in the modifier solution of KOH 1.0 mol.L?¹. In addition, the electro-oxidation of alcohols studied occurs at lower potential, compared to catalysts based on noble metals. The dependence of the amount of the modifier in the CCE was studied, showing a linear response of the anodic peak current as a function of the amount of mass used. The electrode supported a large number of cycles in the presence of alcohols studied, with absence of poisoning. High concentration values of fuels at the point of saturation were found.