Síntese, modificação química e caracterização de óxido de grafeno preparado via eletroquímica

Abstract

The graphene is a material of 21st century with excellent mechanical, optical and electrical properties, with wide variety of technological applications and whose raw material is an abundant material in nature. However its large-scale production is still a challenge for science. Therefore, the aims of this Master's thesis was to study a simple methodology capable of preparing graphene oxide (GO) from electrochemical graphite exfoliation, as well as its functionalization with phthalic anhydride (f-GO) and subsequent doping with Cu2+ and Ag+ ions. The electrochemical graphite (as anode) exfoliation was performed in electrochemical cell using H2SO4 1M as electrolyte and positive potential of 2.3V, this potential was gradually increased up to 10V. The graphene oxide obtained was characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared absorption spectroscopy (FTIR), UV-vis spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM). All characterization techniques confirmed the incorporation of functional groups containing oxygen (hydroxyl, carboxyl and epoxy), confirmed therefore the oxidation of graphite. The confirmation of graphite exfoliation to graphene oxide was obtained by XRD. XRD spectrum shows the diffraction peak of the graphene. The MEV shows morphology of overlapping layer of graphene. The study of the electrical conductivity (σ, S/m) with temperature (T, K) confirmed the obtention of graphene oxide too, showing the curve σ versus T a semimetal behavior of graphene.The functionalization of GO with phthalic anhydride was confirmed by FTIR. The FTIR spectrum showed a decresed of OH groups concentration on f-GO. The doping of f-GO was confirmed by MEV-EDS. The MEV showed a morphology of corrugated graphene sheets, the EDS confirmed a presence of Cu2+ and Ag+ ions on the surface of f-GO. The dependence of conductivity with temperature of doped f-GO samples showed a semimetal and semiconductor behavior.