Microparticles of α-Bi2O3 Obtained from Bismuth Basic Nitrate [Bi6O6(OH)2(NO3)4·2H2O] with Photocatalytic Properties

Alpha phase bismuth oxide (α-Bi2O3) microparticles were prepared through the annealing at 600 °C of basic bismuth nitrate [Bi6O6(OH)2(NO3)4·2H2O] precursors with different morphologies and crystallinity that were obtained by a chemical precipitation method. The precursors were synthesized using ethylenediamine (EN) solvent and varying the HNO3/Bi3+ and HNO3/EN molar ratios, with and without thermal reflux. The influence of the HNO3/EN molar ratio and the thermal reflux on the physicochemical properties of the Bi6O6(OH)2(NO3)4·2H2O precursors and the obtained α-Bi2O3 phase were analyzed by X-ray diffraction, thermogravimetric and differential scanning calorimetric analysis, FTIR analysis, scanning electron microscopy and diffuse reflectance spectroscopy. A correlation between the chemical composition of the Bi6O6(OH)2(NO3)4·2H2O precursors and the physicochemical properties of α-Bi2O3 phase was proposed. Finally, the photocatalytic activity of the α-Bi2O3 microparticles was tested in the photodegradation of indigo carmine dye under UV–A light.