SÍNTESE, CARACTERIZAÇÃO E ESTUDO DAS PROPRIEDADES DOS ÓXIDOS DE Mo E W E SEUS RESPECTIVOS COMPÓSITOS COM QUITOSANA E POLIANILINA

Abstract

The following thesis describes the synthesis and characterization of molybdenum (α-MoO3) and tungsten (WO3·H2O) oxides as well as their respective composites with chitosan and polyaniline (pani). It was proposed a simple, low cost and ecological route for the synthesis of WO3·H2O from filament of discarded H4 halogen lamps. WO3·H2O has a high crystallinity orthorhombic structure with negatively charged particles and needle-like morphology with 3.9% of α-MoO3. The synthesis of polyaniline (pani) with chitosan and oxides characterized by infrared (FTIR), ultraviolet-visible (UV-VIS), Raman and Dispersive Energy (EDS) spectroscopies, thermogravimetric analysis, differential scanning calorimetry (DSC), Zeta potential, cyclic voltammetry (Vc) and scanning electron microscopy (SEM). The results indicate the formation of composites (pani/chitosan, pani/oxide and pani/chitosan/oxide) with the polyaniline in the form of pani emeraldine salt and the interaction between the chains of pani, chitosan and the particles of oxides. Thermogravimetric analysis indicated that the composites have a thermal stability superior to pure pani. FTIR spectroscopy and TG data indicates that occurred graft between the pani chains and the chitosan chains in the composites. SEM images and cyclic voltammograms indicated that chitosan and WO3·H2O particles promoted the ordering of pani chains with the pani/chitosan (PQ) composite, presenting fibrous morphology and potential application in supercapacitors and as adsorbent for macro-scale anionic pollutants. The composite Pani/α-MoO3 15% (PM15) presents promising performance in the electrocatalysis of ethanol. α-MoO3 and WO3·H2O improved the capacitance characteristics of the pani, attributing facilitated charge injection processes and higher current densities, characteristics not reported in the pani-chitosan-α-MoO3 or WO3·H2O composites described in the literature.