Nitretos de carbono: estudo de diferentes rotas sintéticas, obtenção de materiais heteroestruturados com níobio, caracterização, aplicações fotocatalíticas e na produção de biodisel

Abstract

In this work, several synthetic routes to obtain carbon nitrides structures with distinct physical-chemical properties were investigated. The materials were obtained using melamine as precursor of carbon and nitrogen. Through different methods bulk, honeycomb like, and nanosheets structures were synthetized. The nanosheets wereobtained either by direct synthesis or by exfoliation of the bulk material. Furthermore, C3N4/Nb2O5 heterostructures were produced. Those materials were applied on biodiesel production and on photocatalytic degradation of the dye Rhodamine B. Chapters 1 and 2 presented a brief introduction and bibliographic references about the composition, synthesis and applications of carbon nitrides. Chapter 3presents the purposes of this work. In chapter 4, the methods and synthetic routes used in this work are presented. As well as the description of each characterization techniques carried out to study thephysical-chemical properties of the synthetized materials. The methodologies of the carbon nitride applications are also presented.Chapter 5 deals with results and its discussion regarding the synthesis and characterization of the materials. Results of elemental analysis, IR and XPS certified the production of carbon nitride structures and indicated the presence of functionalization on each compound. Analysis of XRD, TEM, AFM and nitrogen sorption and desorption allowed to determine the morphology and microstructure of the compounds. Results of PL and diffuse reflectance allowed comprehending the relation between the synthetic route and the electronic structure, as well as thevariations on bandgap values. Chapter 6 shows the preliminary results of biodiesel production through the transesterification reaction of soy oil, using the obtained composites as catalysts. The compound obtained by acidic exfoliation was the only exhibiting satisfactory results, due to the presence of functionalization and basic groups on its surface. Chapter 7 deals with the results from oxidative photocatalysis of the dyeRhodamine B using the synthetized materials as catalysts. Those materials were capable of degrade the dye, making possible to relate the morphological and electronic properties with its performance.