Synthesis of bismuth oxyiodide (BiOI) by means of microwaves in glycerol with high photocatalytic activity for the elimination of NOx and SO2

Abstract

A facile microwave route was successfully developed to synthesize BiOI in glycerol as a medium of reaction. The temperature and time of synthesis were selected as the critical experimental variables to rule the physicochemical properties of the samples prepared. The products were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy, adsorption–desorption N2 isotherms, diffuse reflectance spectroscopy, scanning electron microscopy, X-ray electron spectroscopy and thermogravimetric/differential scanning calorimetry (TGA/DSC). The photocatalytic activity of BiOI samples was tested in the oxidation reactions of nitric oxide (NO) and sulfur dioxide (SO2) in gaseous phase under visible light radiation. The photocatalysts with the highest activity were the samples prepared by microwave irradiation at 135 °C for 20–34 min and were able to remove 97.8% of NO2 and 85.2% of SO2. The analysis by XRD revealed aspects of the samples that improved its photocatalytic activity, such as the preferential crystalline orientation in (110) BiOI planes, as well as the presence of the secondary crystalline phases Bi, Bi2O2.5 and Bi4O5I2. The use of chemical scavengers revealed that the ion superoxide (O2−) and photogenerated electrons (e−) were the predominant active species in the mechanism of the NO oxidation reaction.