Aperfeiçoamento e avaliação da estrutura eletrônica de óxidos de nióbio dopados com cério e titânio para fotocatálise

Abstract

The application of semiconductors in the degradation of organic pollutants in aqueous media has been evaluated due to their ability to interact with UV radiation and with these compounds through heterogeneous photocatalysis. This thesis proposes alternatives to increase efficiency in photocatalysis, highlighting processes of inclusion of elements that can generate surface defects, avoiding high recombination rates and altering the gap energy of the crystalline network of niobium oxides (Nb2O5). Elements such as cerium and titanium can have excellent optoelectronic properties. We sought to obtain new Nb2O5 nanostructured materials synthesized at pH= 1 and 3, loaded with titanium and/or cerium in the proportion of 0.5 to 1% with potential absorptivity in the UV and/or UV-Vis region and efficient in the photodegradation of pollutants. The materials were obtained by hydrothermal route and evaluated for their structural (FTIR, Raman, BET, DRX, TGA and XPS), morphological (SEM) and optical (DRS in UV-Vis) properties. The materials were obtained in the Orthorhombic phase or mixture between Orthorhombic and Monoclinic and the amount of dopant affected the gap energy, decreasing from 2.97 eV to 2.01 eV at pH=1 and increasing from 1.78 eV to 2.77 eV at pH=3. The Nb2O5 containing Ce and Ti were able to photocatalytic degradation of the methyl orange dye and the drug ibuprofen. In the photocatalytic tests, all materials were able to degrade all pollutants, with the material doped with 0.8% at pH=1 being the most promising for the dye and 0.5% for the drug.