Síntese e caracterização de nanomateriais de carbono e suas aplicações na adsorção de contaminantes ambientais e como eletrodos em supercapacitores

Abstract

In this work, carbon nanomaterials were synthesized via CVD method at low tem-perature (700 ° C) using two classes of catalysts. The first one was formed by iron, nickel and cobalt supported in a MgO matrix, and the second used the same metals as centers of an organometallic complex. Ethanol and acetonitrile were used as carbon sources for the materials synthesized for the supported catalysts and ethanol as the carbon source in the case of organometallic complexes. For the six materials synthesized using the supported catalysts, NTCs were obtained in three cases. The results of transmission electron micros-copy and Raman spectroscopy showed that the materials obtained using supported cobalt as catalyst and ethanol as carbon source produced NMC with better graphite structures and better tube order. The organometallic catalyst produced materials with graphite walls, known as carbon nanofibers. The Raman spectroscopy results of these materials showed that they have a high degree of defects in their graphite structures, which allowed their application as electrodes in double layer supercapacitors. All carbon materials obtained were characterized by XRD, Raman spectroscopy, pho-toelectron spectroscopy, elemental and thermal analyses. The XPS results showed that NTCs formed from ethanol had functional groups on their surface, whereas NTCs formed from acetonitrile had nitrogen dopant atoms in their structures, leading to the formation of NTCs of the "bamboo like" type. The carbon nanofibers also had functional groups on their sur-face, as well as a high degree of defects in their graphite wall structures. The materials formed with the supported catalyst were applied in adsorption tests of the 17-ethinylestradiol contaminant and the carbon nanofibers were applied in electro-chemical tests. The materials obtained on the MgO matrix showed good dispersion in aque-ous solutions, with high contaminant removal potential. The NiCN sample formed the larg-est amount of carbon materials, and therefore presented a greater potential for the removal of the hormone, while the iron material presented low hormone removal potential. While studying the amount of hormones removed by the mass of NMC contained in the system, the values of the removals were observed to be different, and the cobalt materials pre-sented the best removal performance. Carbon nanofibers were used in cyclic voltammetry tests and showed good specific capacitance results, due to the large amount of mesopores present in their structures.