Influência do método de síntese nas propriedades físico-químicas e no desempenho fotocatalítico do Nb2O5

Abstract

Population growth and economic expansion have led to significant environmental challenges stemming from the emission of various effluents (industrial, domestic, and agricultural) and the combustion of fossil fuels, resulting in the release of substantial quantities of greenhouse gases. It is imperative to develop strategies for the degradation of organic and fostering the production of renewable fuels, such as green hydrogen (H2). In this context, the application of the semiconductor Nb2O5 in heterogeneous photocatalysis has garnered attention due to its potential for facilitating both the oxidation of organic pollutants through radical species and the generation of fuels via solar irradiation. However, to date, Nb2O5 remains relatively underexplored for this purpose. Consequently, the primary aim of this study was to compare two synthesis techniques (hydrothermal and direct calcination) and two niobium (Nb) precursors to produce Nb2O5. The materials evaluation using X-Ray Diffraction and Raman Spectroscopy revealed that both the synthesis method and the Nb precursor had an impact on the structural characteristics of the catalysts. Specifically, the use of the ammonium niobium oxalate as precursor in conjunction with the hydrothermal method and calcination at 600ºC resulted in the formation of crystalline phases with pseudohexagonal and orthorhombic structures, respectively. Conversely, the hydrothermal method did not induce structural alterations in the commercially available Nb2O5. In all cases, the materials exhibited a comparable band gap of approximately 3.2 eV. Scanning electron microscopy images exhibited that the hydrothermal synthesis employing the Nb complex yielded materials with a more uniform morphology and smaller particle size, approximately 40 nm. All synthesized materials demonstrated activity in the degradation of the Rhodamine B dye and the Amiloride drug. Notably, the Nb2O5 sample produced via the hydrothermal method exhibited superior degradation performance, attributed to its larger specific surface area. Additionally, the introduction of Pt nanoparticles enhanced the catalytic reaction's efficiency. Consequently, this study elucidates the influence of various Nb2O5 synthesis parameters on its photocatalytic properties and underscores its versatility as a promising material for diverse photocatalytic applications.