Síntese, caracterização e aplicação de compostos a base de cobalto

Abstract

Cobalt-based nanostructured compounds, in their oxide form (Co3O4) and oxyhydroxide (CoO(OH)), are well-known electroactive semiconductor materials, involving multiple oxidation states and different ions. Particularly, these semiconductor materials have been widely used in various technologies, mainly because they present a low cost of processing, as well as, exhibits excellent magnetic, sensor, catalytic, optical and electronic properties. Thus, the study of these potential applications in several technologies based on nanocrystals of cobalt compounds has aroused a great scientific and industrial interest in the last years. Thus, this work is focused on the deep understanding of the structural, optical and catalytic properties of nanostructured cobalt compounds, prepared by the hydrothermal method with different concentrations of hydrogen peroxide (H2O2). These nanomaterials were characterized by X-ray diffraction (XRD), photoluminescence (PL), ultraviolet and visible (UV-vis) reflectance spectroscopy, photocatalysis and hydrogen peroxide decomposition. The composite Co3O4/ CoO(OH) prepared with 4% of H2O2 presented superior catalytic activity for the decomposition of H2O2 in relation to the sample synthesized with only 1% of peroxide in the same hydrothermal conditions. The optical properties, measured by photoluminescence, demonstrate a broad emission band in the visible region of the electromagnetic spectrum, with superior luminescent properties for the 1% sample. Therefore, in this work we will discuss the influence of phase composition on the optical and photocatalytic properties of these materials. These studies can contribute to a greater understanding of their fundamental properties, as well as to the development of new emerging technologies.