Síntesis y caracterización de nanoestructuras de ferrita de bismuto dopadas: síntesis y caracterización estructural y morfológica de esferas huecas de ferrita de bismuto y su uso en la degradación de contaminantes orgánicos.

Abstract

Bismuth ferrite (BFO) is a semiconductor with a narrow energy bandgap (2.2-2.5 eV) and good chemical stability. This makes BFO a promising candidate for photocatalytic applications, such as organic pollutant degradation studies. Morphology is a crucial factor since having a greater surface area improves the photocatalytic activity of a material. Therefore, this work focused on synthesizing hollow BFO spheres by soft templating and hydrothermal methods. In the samples synthesized by soft templating methods, we varied the concentration of the surfactant, pluronic (P123), and the content of the dopant, i.e. Gd. On the other hand, in the samples synthesized by hydrothermal methods, conditions such as autoclave pressure, doping percentage and amount of precursors were varied. The samples were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was found that the samples synthesized by the soft templating method presented impurities in percentages less than 6%. However, the resulting morphologies were not homogeneous since none of the samples presented a homogeneous distribution of material. A clear influence of the P123 concentration on the morphology was observed. The number of spheres and their agglomeration increased with higher P123 concentration. For the hydrothermal method, the optimal parameters were found to obtain hollow BFO spheres with approximately 3% of impurities. We also found that acid washing of the samples considerably reduce the amount of impurities without affecting the morphology of the compound. The energy bandgap of the sample with the best morphology and the least amount of impurities was 2.22 eV for direct transitions. This sample was subjected to photocatalysis experiments, with Rhodamine B as a model contaminant, achieving complete degradation in 180 minutes without modifying the pH of the solution.