Síntese e caracterização de nanoestruturas de Nb2O5 e Nb2O5@TiO2: avaliação do mecanismo de crescimento e potencial fotocatalítico

Abstract

This study aimed to investigate the hydrothermal/solvothermal synthesis of Nb2O5, using a reaction in the presence of hydrogen peroxide under different experimental conditions. Additionally, efforts were made to comprehend the growth mechanism of nanostructures of this crucial oxide. Furthermore, the synthesis of Nb2O5@TiO2 heterostructures was explored as a means to create interfaces that enable modification of the electron-hole pair recombination process. The photocatalytic activity of the obtained materials was studied in a model system, involving the degradation of rhodamine B dye in aqueous solution under UV radiation. The chemical and structural characterization of the obtained materials was performed using various techniques such as X-ray diffraction associated with Rietveld refinement, transmission electron microscopy with energy-dispersive X-ray spectroscopy (EDS) and electron diffraction analyses, UV-Vis spectroscopy by diffuse reflectance, infrared spectroscopy, and Raman spectroscopy. The results indicated the formation of Nb2O5 nanostructures of the TT type, with hedgehog and nanorod morphologies. Transmission electron microscopy and X-ray diffraction allowed the inference that nanorods form through an oriented attachment growth mechanism, growing along the crystallographic direction [001], with the formation of defects in the [100] and [010] directions. Nano-heterostructures of Nb2O5@TiO2 were investigated by transmission electron microscopy and X-ray diffraction. The formation of particles with a crystallized Nb2O5 core in the T crystalline phase, surrounded by an amorphous region corresponding to the titanium inorganic complex, was observed. After calcination, this leads to the formation of TiO2 in the anatase phase. In the rhodamine B degradation studies, Nb2O5 samples in the TT phase exhibited good photocatalytic activity, attributed to the nanorod morphology. This morphology, growing along the [001] direction, exposes crystallographic planes (100) and (010). However, Nb2O5@TiO2 nano-heterostructures showed the highest photocatalytic activity, potentially related to the formation of a type II heterojunction, reducing the recombination of electron-hole pairs.